As filed with the Securities and Exchange Commission on April 18, 2022

Registration No. 333-264159

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

AMENDMENT NO. 1

TO

FORM S-1

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

HILLEVAX, INC.

(Exact name of registrant as specified in its charter)

75 State Street, Suite 100 - #9995

Boston, Massachusetts 02109

(617) 213-5054

(Address, including zip code, and telephone number, including area code, of registrant’s principal executive offices)

Rob Hershberg, M.D., Ph.D.

Chairman, President and Chief Executive Officer

HilleVax, Inc.

75 State Street, Suite 100 - #9995

Boston, Massachusetts 02109

(617) 213-5054

(Name, address, including zip code, and telephone number, including area code, of agent for service)

Copies to:

Approximate date of commencement of proposed sale to the public: As soon as practicable after this Registration Statement is declared effective.

If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, check the following box.  ☐

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ☐

If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ☐

If this Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, smaller reporting company or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Securities Act.  ☐

The Registrant hereby amends this Registration Statement on such date or dates as may be necessary to delay its effective date until the Registrant shall file a further amendment which specifically states that this Registration Statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933, as amended, or until the Registration Statement shall become effective on such date as the Securities and Exchange Commission, acting pursuant to said Section 8(a), may determine.

The information in this preliminary prospectus is not complete and may be changed. We may not sell these securities until the registration statement filed with the Securities and Exchange Commission is effective. This prospectus is not an offer to sell these securities and it is not soliciting an offer to buy these securities in any state where the offer or sale is not permitted.

SUBJECT TO COMPLETION, DATED APRIL 18, 2022

Preliminary Prospectus

                 shares

Common stock

This is the initial public offering of shares of common stock by HilleVax, Inc. We are selling             shares of our common stock. The initial public offering price is expected to be between $                 and $                 per share.

Prior to this offering, there has been no public market for our common stock. We have applied to list our common stock on the Nasdaq Global Select Market under the symbol “HLVX.”

We are an “emerging growth company” as defined under the federal securities laws and, as such, have elected to comply with certain reduced public company reporting requirements.

At our request, the underwriters have reserved up to         % of the shares of common stock offered by this prospectus for sale, at the initial public offering price, to certain individuals associated with us. See “Underwriting—Directed share program.”

We have granted the underwriters an option for a period of 30 days to purchase up to                  additional shares of our common stock.

Investing in our common stock involves a high degree of risk. See “Risk factors” beginning on page 15.

Neither the Securities and Exchange Commission nor any other state securities commission has approved or disapproved of these securities or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

The underwriters expect to deliver the shares of common stock to purchasers on                , 2022.

                , 2022

Table of contents

Through and including                , 2022 (the 25th day after the date of this prospectus), all dealers effecting transactions in these securities, whether or not participating in this offering, may be required to deliver a prospectus. This delivery is in addition to a dealer’s obligation to deliver a prospectus when acting as an underwriter and with respect to an unsold allotment or subscription.

Neither we nor the underwriters have authorized anyone to provide you with information other than that contained in this prospectus or any free writing prospectus prepared by or on behalf of us or to which we have referred you. We and the underwriters take no responsibility for, and can provide no assurance as to the reliability of, any other information that others may give you. We and the underwriters are offering to sell, and seeking offers to buy, common stock only in jurisdictions where offers and sales are permitted. The information contained in this prospectus or any free writing prospectus is accurate only as of its date, regardless of its time of delivery or of any sale of shares of our common stock. Our business, financial condition, results of operations and prospects may have changed since that date.

For investors outside of the United States: we have not, and the underwriters have not, done anything that would permit this offering or possession or distribution of this prospectus in any jurisdiction where action for that purpose is required, other than the United States. Persons outside of the United States who come into possession of this prospectus must inform themselves about, and observe any restrictions relating to, the offering of the shares of common stock and the distribution of this prospectus outside of the United States.

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Risk factors

Investing in our common stock involves a high degree of risk. You should consider carefully the risks and uncertainties described below, together with all of the other information in this prospectus, including our combined financial statements and related notes included elsewhere in this prospectus and the section titled “Management’s discussion and analysis of financial condition and results of operations” before making an investment decision. If any of the following risks are realized, our business, financial condition, results of operations and prospects could be materially and adversely affected. In that event, the trading price of our common stock could decline and you could lose part or all of your investment. Additional risks and uncertainties not presently known to us or that we currently deem immaterial also may impair our business operations. This prospectus also contains forward-looking statements that involve risks and uncertainties. Our actual results could differ materially from those anticipated in the forward-looking statements as a result of a number of factors, including the risks described below. See “Special note regarding forward-looking statements.”

Risks related to our limited operating history, financial position and capital requirements

We have a limited operating history and have no products approved for commercial sale, which may make it difficult for you to evaluate our current business and predict our future success and viability.

Biopharmaceutical product development is a highly speculative undertaking and involves a substantial degree of risk. We are a clinical-stage biopharmaceutical company with a limited operating history upon which you can evaluate our business and prospects. We commenced operations in 2019, and we have no products approved for clinical commercial sale. To date, we have focused primarily on organizing and staffing our company, business planning, raising capital, in-licensing intellectual property related to our initial vaccine candidate, HIL-214, and preparing for our planned clinical trials of HIL-214. We have not yet submitted an IND or its equivalent to the applicable regulatory agencies or completed any clinical trials, manufactured a commercial-scale product or arranged for a third party to do so on our behalf, obtained regulatory approvals, or conducted sales and marketing activities necessary for successful product commercialization. Consequently, any predictions made about our future success or viability may not be as accurate as they would be if we had a history of successfully developing and commercializing vaccines.

In addition, we may encounter unforeseen expenses, difficulties, complications, delays and other known and unknown factors and risks frequently experienced by clinical-stage biopharmaceutical companies in rapidly evolving fields. If our planned clinical trials are successful, we will also need to transition from a company with a research focus to a company capable of successfully executing drug development activities and supporting commercial operations. If we do not adequately address these risks and difficulties or successfully make such a transition, our business, financial condition, results of operations and prospects will be significantly harmed.

We have incurred significant operating losses since our inception and expect to incur significant losses for the foreseeable future. We may never generate any revenue or become profitable or, if we achieve profitability, we may not be able to sustain it.

We have incurred significant operating losses since our inception. We do not have any products approved for sale and have not generated any revenue since our inception. If HIL-214 is not successfully developed, approved and commercialized, we may never generate any revenue. Our net losses were $2.1 million and $102.4 million for the years ended December 31, 2020 and 2021, respectively. We have financed our operations to date through the issuance of convertible promissory notes. Substantially all of our losses have resulted from expenses incurred in connection with in-licensing intellectual property related to, and developing, HIL-214 and from general and administrative costs associated with our operations. HIL-214 and any future vaccine candidates will require

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substantial additional development time and resources before we would be able to apply for or receive regulatory approvals and begin generating revenue from product sales. We expect to continue to incur losses for the foreseeable future, and we anticipate these losses will increase substantially as we continue our development of, seek regulatory approval for and potentially commercialize HIL-214 and seek to identify, assess, acquire, in-license intellectual property related to or develop additional vaccine candidates.

To become and remain profitable, we must succeed in developing and eventually commercializing products that generate significant revenue. This will require us to be successful in a range of challenging activities, including completing preclinical studies and clinical trials of HIL-214 and any future vaccine candidates, obtaining regulatory approval for these vaccine candidates, and manufacturing, marketing and selling any products for which we may obtain regulatory approval. We are only in the preliminary stages of most of these activities. We may never succeed in these activities and, even if we do, may never generate revenue that is significant enough to achieve profitability. In addition, we have not yet demonstrated an ability to successfully overcome many of the risks and uncertainties frequently encountered by companies in new and rapidly evolving fields, particularly in the biopharmaceutical industry. Because of the numerous risks and uncertainties associated with biopharmaceutical product development, we are unable to accurately predict the timing or amount of increased expenses or when or if, we will be able to achieve profitability. Even if we do achieve profitability, we may not be able to sustain or increase profitability on a quarterly or annual basis. Our failure to become and remain profitable may have an adverse effect on the value of our company and could impair our ability to raise capital, expand our business, maintain our research and development efforts, diversify our vaccine candidates or even continue our operations. A decline in the value of our company could also cause you to lose all or part of your investment.

We will require substantial additional financing to achieve our goals, and a failure to obtain this necessary capital when needed on acceptable terms, or at all, could force us to delay, limit, reduce or terminate our development programs, commercialization efforts or other operations.

The development of vaccine candidates is capital-intensive. We expect our expenses to increase in connection with our ongoing activities, particularly as we conduct our planned clinical trials for HIL-214 and potentially seek regulatory approval for HIL-214 and any future vaccine candidates we may develop. In addition, if we are able to progress HIL-214 through development and commercialization, we will be required to make milestone and royalty payments to Takeda, from whom we have in-licensed certain patents and know-how related to HIL-214 globally, other than in Japan, pursuant to the license agreement we entered into with Takeda on July 2, 2021 (the Takeda License). If we obtain regulatory approval for HIL-214 or any future vaccine candidates, we also expect to incur significant commercialization expenses related to product manufacturing, marketing, sales and distribution. Because the outcome of any preclinical study or clinical trial is highly uncertain, we cannot reliably estimate the actual amounts necessary to successfully complete the development and commercialization of HIL-214 or any future vaccine candidates. Furthermore, following the completion of this offering, we expect to incur additional costs associated with operating as a public company. We do not have any committed external source of funds.

As of December 31, 2021, we had cash of $124.6 million. Based on our current operating plan, we believe that the net proceeds from this offering, together with our existing cash, will enable us to fund our operations for at least the next                  from the date of this prospectus. We have based these estimates on assumptions that may prove to be wrong, and we could use our capital resources sooner than we currently expect and need to seek additional funds sooner than planned. The net proceeds of this offering, together with our existing cash and restricted cash, will not be sufficient to complete development of HIL-214, or any future vaccine candidate, and after this offering, we will require substantial capital in order to advance HIL-214 and any future vaccine candidates through clinical trials, regulatory approval and commercialization. Accordingly, we will need to

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obtain substantial additional funding in connection with our continuing operations. If we are unable to raise capital when needed or on attractive terms, we could be forced to delay, reduce or eliminate our research and development programs or any future commercialization efforts.

We expect to finance our cash needs through public or private equity or debt financings or other capital sources, including potential collaborations, licenses, non-dilutive sources of financing, such as grants, and other similar arrangements. In addition, we may seek additional capital due to favorable market conditions or strategic considerations even if we believe we have sufficient funds for our current or future operating plans. Attempting to secure additional financing may divert our management from our day-to-day activities, which may adversely affect our ability to develop HIL-214 and any future vaccine candidates.

Our future capital requirements will depend on many factors, including, but not limited to:

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Conducting preclinical studies and clinical trials is a time-consuming, expensive and uncertain process that takes years to complete, and we may never generate the necessary data or results required to obtain regulatory approval and commercialize HIL-214 and any future vaccine candidates. If approved, HIL-214 and any future vaccine candidates may not achieve commercial success. Our commercial revenue, if any, will initially be derived from sales of HIL-214, which we do not expect to be commercially available for many years, if at all. Accordingly, we will need to continue to rely on additional financing to achieve our business objectives. Adequate additional financing may not be available to us on acceptable terms, or at all.

Raising additional capital may cause dilution to our stockholders, including purchasers of common stock in this offering, restrict our operations or require us to relinquish rights to our technologies or vaccine candidates.

Until such time, if ever, as we can generate substantial product revenue, we expect to finance our cash needs through equity offerings, our loan and security agreement with Hercules Capital, Inc. (Hercules), as administrative and collateral agent, and the lenders party thereto (Loan Agreement), debt financings, or other capital sources, including potential collaborations, license agreements and other similar arrangements. To the extent that we raise additional capital through the sale of equity or convertible debt securities, your ownership interest may be diluted, and the terms of these securities may include liquidation or other preferences that adversely affect your rights as a common stockholder. The Loan Agreement includes, and any future debt financing and preferred equity financing, if available, may involve agreements that include, covenants limiting or restricting our ability to take specific actions, such as incurring additional debt, making capital expenditures or declaring dividends. Such restrictions could adversely impact our ability to conduct our operations and execute our business plan.

If we raise additional funds through future collaborations, license agreements and other similar arrangements, we may be required to relinquish valuable rights to our future revenue streams, research programs, vaccine candidates, intellectual property or proprietary technology, or grant licenses on terms that may not be favorable to us and/or that may reduce the value of our common stock. If we are unable to raise additional funds through equity or debt financings or other arrangements when needed or on terms acceptable to us, we would be required to delay, limit, reduce, or terminate our product development or future commercialization efforts or grant rights to develop and market vaccine candidates that we might otherwise prefer to develop and market ourselves.

Our management, as of December 31, 2021, and our independent registered public accounting firm, in their report on our audited combined financial statements as of and for the year ended December 31, 2021, have concluded that there is substantial doubt as to our ability to continue as a going concern.

Our audited combined financial statements for the year ended December 31, 2021 were prepared assuming that we will continue as a going concern. The going concern basis of presentation assumes that we will continue in operation for the foreseeable future and will be able to realize our assets and satisfy our liabilities in the normal course of business and do not include any adjustments to reflect the possible future effects on the recoverability and classification of assets or amounts and classification of liabilities that may result from our inability to continue as a going concern. As of December 31, 2021, our management concluded that, based on our expected operating losses, negative cash flows and maturities of outstanding convertible promissory notes, there is substantial doubt about our ability to continue as a going concern for the twelve months after the date the combined financial statements were issued. Our ability to continue as a going concern is subject to our ability to obtain sufficient financing. If we cannot continue as a going concern, we may have to liquidate our assets and may receive less than the value at which those assets are carried on our combined financial statements, and it is likely that our stockholders may lose some or all of their investment in us.

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After this offering, we may not raise the funding we require such that substantial doubt about our ability to

continue as a going concern continues. If we seek additional financing to fund our business activities in the future and there remains substantial doubt about our ability to continue as a going concern, investors or other financing sources may be unwilling to provide additional funding on commercially reasonable terms or at all.

Risks related to the development and regulatory approval of our vaccine candidates

We currently depend entirely on the success of HIL-214, which is our only vaccine candidate. If we are unable to advance HIL-214 in clinical development, obtain regulatory approval and ultimately commercialize HIL-214, or experience significant delays in doing so, our business will be materially harmed.

We currently only have one vaccine candidate, HIL-214, the intellectual property for which we have in-licensed from Takeda and which is in Phase 2 clinical development. Our business presently depends entirely on our ability to successfully develop, obtain regulatory approval for, and commercialize HIL-214 in a timely manner. This may make an investment in our company riskier than similar companies that have multiple vaccine candidates in active development that may be able to better sustain the delay or failure of a lead vaccine candidate. In addition, our assumptions about HIL-214’s development potential are based in large part on the data generated from preclinical studies and clinical trials conducted by Takeda and Ligocyte and we may observe materially and adversely different results as we conduct our planned clinical trials. The success of HIL-214 will depend on several factors, including the following:

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In addition, our development plan for HIL-214 initially targets the prevention of moderate to severe AGE caused by norovirus in infants. Depending on the feedback we receive from regulatory agencies, we may decide to further limit our initial target population to a subset of infants, such as infants with certain underlying health conditions common within this age range, or we may materially modify our current plans to use immunobridging studies based on a serology surrogate endpoint and or the criteria proposed to seek subsequent regulatory authorizations in older children, adults and older adults. Limiting our target patient population may negatively impact our ability to complete clinical trials or studies within our planned timeline and could limit the commercial potential of HIL-214. If we are unable to develop, receive marketing approval for and successfully commercialize HIL-214 in our targeted patient populations, or if we experience delays as a result of any of the above factors or otherwise, our business would be significantly harmed.

Clinical and preclinical development involves a lengthy and expensive process with an uncertain outcome, and the results of prior clinical trials and studies of HIL-214 are not necessarily predictive of our future results. We have not completed clinical trials for HIL-214 and we may not have favorable results in our clinical trials, or receive regulatory approval on a timely basis, if at all.

Clinical and preclinical development is expensive and can take many years to complete, and its outcome is inherently uncertain. We cannot guarantee that any preclinical studies or clinical trials will be conducted as planned or completed on schedule, if at all, and failure can occur at any time during the trial or study process. For example, we may not be able to meet expected timeframes for the initiation of our planned Phase 2b clinical trial of HIL-214 or the reporting of data from such trial. Despite promising preclinical or clinical results, any vaccine candidate can unexpectedly fail at any stage of preclinical or clinical development. The historical failure rate for vaccine candidates in our industry is high, particularly in the early stages of development.

The results from preclinical studies or clinical trials of a vaccine candidate or a competitor’s vaccine candidate in the same class may not predict the results of later clinical trials of such vaccine candidate, and interim, topline, or preliminary results of a clinical trial are not necessarily indicative of final results. Vaccine candidates in later stages of clinical trials may fail to show the desired safety and efficacy characteristics despite having progressed through preclinical studies and initial clinical trials. In particular, while HIL-214 has been studied by Takeda in an extensive clinical program that included nine clinical trials, we do not know how HIL-214 will perform in our planned clinical trials, whether due to design differences, subject population or otherwise, including our use of a different manufacturing process to produce clinical material than that used in these prior trials. For these reasons and others, it is not uncommon to observe results in clinical trials that are unexpected based on preclinical studies and early clinical trials. Many vaccine candidates fail in clinical trials despite very promising early results, and a number of companies in the biopharmaceutical and biotechnology industries have suffered significant setbacks in clinical development even after achieving promising results in earlier preclinical studies and clinical trials. Based upon negative or inconclusive results, we or any future collaborator may decide, or regulators may require us, to conduct additional preclinical studies or clinical trials, which would cause us to incur additional operating expenses. Further, since there are no reliable animal models to norovirus infection, we may have to complete additional human challenge studies, which have been used to understand viral activity and possible immune correlates that prevent infection, making trials costlier than animal-based studies.

In addition, under the Takeda License, Takeda, a third party over which we have no control, has the right to develop and commercialize HIL-214 in Japan. If Takeda conducts any clinical trials of HIL-214 or if such trials generate negative results or results that conflict with the results of our clinical trials, the FDA, EMA, or other regulatory authorities may delay, limit, or deny approval of HIL-214, require us to conduct additional clinical trials as a condition to marketing approval, or withdraw their approval of HIL-214 or otherwise restrict our ability to market and sell HIL-214, if approved.

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As a result, we cannot be certain that our planned preclinical studies and clinical trials will be successful. Any safety concerns observed in any one of our clinical trials in our targeted indications could limit the prospects for regulatory approval of HIL-214 in those and other indications, which could have a material adverse effect on our business, financial condition and results of operations.

Any difficulties or delays in the commencement or completion, or the termination or suspension, of our planned clinical trials could result in increased costs to us, delay or limit our ability to generate revenue or adversely affect our commercial prospects.

Before obtaining marketing approval from regulatory authorities for the sale of HIL-214 or any future vaccine candidates, we must conduct extensive clinical trials to demonstrate the safety, purity, potency, immunogenicity and efficacy of the vaccine candidates in humans. In September 2021, an open IND was transferred to us by Takeda, under which we plan to initiate a Phase 2b clinical trial. Before we can initiate clinical trials for any future vaccine candidates, we must submit the results of preclinical studies to the FDA or comparable foreign regulatory authorities along with other information, including information about vaccine candidate chemistry, manufacturing and controls and our proposed clinical trial protocol, as part of an IND with the FDA or as part of any similar regulatory submission required for allowance to proceed with clinical development. The FDA, EMA or comparable foreign regulatory authorities may require us to conduct additional preclinical studies, or added clinical evaluation under any IND, clinical trial authorization or similar regulatory submission, which may lead to delays and increase the costs of our clinical development program. Moreover, even if we commence clinical trials, issues may arise that could cause regulatory authorities to suspend or terminate such clinical trials. Any such delays in the commencement or completion of our ongoing and planned clinical trials for HIL-214 and any future vaccine candidates could significantly affect our product development timelines and product development costs.

We do not know whether our planned clinical trials will begin on time or be completed on schedule, if at all. The commencement, data readouts and completion of clinical trials can be delayed for a number of reasons, including delays related to:

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We could also encounter delays if a clinical trial is suspended or terminated by us, by the IRBs of the institutions in which such trials are being conducted, by a Data Safety Monitoring Board for such trial or by the FDA or comparable foreign regulatory authorities. Such authorities may impose such a suspension or termination due to a number of factors, including failure to conduct the clinical trial in accordance with regulatory requirements or our clinical protocols, inspection of the clinical trial operations or trial site by the FDA or comparable foreign regulatory authorities resulting in the imposition of a clinical hold, unforeseen safety issues or adverse side effects, failure to demonstrate a benefit from using a vaccine, changes in governmental regulations or administrative actions or lack of adequate funding to continue the clinical trial. In addition, changes in regulatory requirements and policies may occur, and we may need to amend clinical trial protocols to comply with these changes. Amendments may require us to resubmit our clinical trial protocols to IRBs for reexamination, which may impact the costs, timing or successful completion of a clinical trial.

Certain of our clinical trials are also being designed based on the learnings from previously completed clinical trials conducted by Takeda. For example, we have designed our planned Phase 2b clinical trial for HIL-214 based on the learnings from the NOR-211 Phase 2b study, the NOR-202 Phase 2 study, as well as preliminary feedback Takeda received from the FDA and the EMA. Although we do not currently expect the FDA to require us to conduct additional clinical trials before proceeding to the Phase 2b clinical trial, there is some risk that the FDA may ask questions or require additional information in order for us to advance to a Phase 2b clinical trial.

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Further, conducting clinical trials in foreign countries, as we plan to do for HIL-214 and may do for future vaccine candidates, presents additional risks that may delay completion of our clinical trials. These risks include the failure of enrolled subjects in foreign countries to adhere to clinical protocols as a result of differences in healthcare services or cultural customs, managing additional administrative burdens associated with foreign regulatory schemes, and political and economic risks, including war, relevant to such foreign countries.

In addition, many of the factors that cause, or lead to, the termination or suspension of, or a delay in the commencement or completion of, clinical trials may also ultimately lead to the denial of regulatory approval of a vaccine candidate. We may make formulation or manufacturing changes to HIL-214 or any future vaccine candidates, in which case we may need to conduct additional preclinical studies to bridge our modified vaccine candidates to earlier versions. Any resulting delays to our clinical trials could shorten any period during which we may have the exclusive right to commercialize our vaccine candidates. In such cases, our competitors may be able to bring products to market before we do, and the commercial viability of HIL-214 or any future vaccine candidates could be significantly reduced. Any of these occurrences may harm our business, financial condition and prospects.

We may find it difficult to enroll subjects in our clinical trials. If we encounter difficulties enrolling subjects in our clinical trials, our clinical development activities could be delayed or otherwise adversely affected.

Successful and timely completion of clinical trials will require that we identify and enroll a specified number of subjects for each of our clinical trials. We may not be able to initiate or continue clinical trials for HIL-214 or any future vaccine candidates if we are unable to identify and enroll a sufficient number of eligible subjects to participate in these trials as required by the FDA or similar regulatory authorities outside the United States.

Subject enrollment, a significant factor in the timing of clinical trials, is affected by many factors, including the size and nature of the subject population, the severity of the disease under investigation, the proximity of subjects to clinical sites, the eligibility and exclusion criteria for the trial, the design of the clinical trial, the ability to obtain and maintain informed consents, the risk that enrolled subjects will not complete a clinical trial, our ability to recruit clinical trial investigators with the appropriate competencies and experience, and competing clinical trials and clinicians’ and subjects’ perceptions as to the potential advantages and risks of the vaccine candidate being studied in relation to other available vaccines or therapies, including any new products that may be approved for the indications we are investigating as well as any vaccine candidates under development.

In addition, the process of finding and recruiting subjects may prove costly. The timing of our clinical trials depends, in part, on the speed at which we can recruit subjects to participate in our trials, as well as completion of required follow-up periods. The eligibility criteria of our clinical trials, once established, may further limit the pool of available trial participants. If subjects are unwilling or unable to participate in our trials for any reason, including the existence of concurrent clinical trials for similar target populations, negative perceptions of vaccines generally or of any of our vaccine candidates in particular, the availability of approved or authorized therapies, the effects of the COVID-19 pandemic, or the fact that enrolling in our trials may prevent subjects from taking a different product, or we otherwise have difficulty enrolling a sufficient number of subjects, the timeline for recruiting subjects, conducting trials and obtaining regulatory approval of our vaccine candidates may be delayed. Our inability to enroll a specified number of subjects for any of our future clinical trials would result in significant delays or may require us to abandon one or more clinical trials altogether. In addition, we rely on, and will continue to rely on, CROs and clinical trial sites to ensure proper and timely conduct of our preclinical studies and clinical trials. Though we have entered into agreements governing their services, we will have limited influence over their actual performance.

We cannot assure you that our assumptions used in determining expected clinical trial timelines are correct or that we will not experience delays in enrollment, which would result in the delay of completion of such trials beyond our expected timelines.

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As an organization, we have never completed any clinical trials, and we may be unable to do so for HIL-214 or any future vaccine candidates.

We will need to successfully complete our planned clinical trials in order to seek FDA, EMA or comparable foreign regulatory approval to market HIL-214 or any future vaccine candidates. Carrying out clinical trials and the submission of a successful BLA or MAA is a complicated process. We plan to initiate a Phase 2b clinical trial of HIL-214 in infants in the second quarter of 2022. While Takeda previously conducted both Phase 1 and 2 clinical trials of HIL-214, we have not previously submitted an IND or completed any clinical trials and have not previously submitted a BLA, MAA or other comparable foreign regulatory submission. Consequently, we may be unable to successfully and efficiently execute and complete necessary clinical trials in a way that enables us to seek and maintain approval of HIL-214 or any future vaccine candidates. We may require more time and incur greater costs than Takeda required, or than our competitors require, and may not succeed in obtaining regulatory approvals of vaccine candidates that we develop. Failure to commence or complete, or delays in, our planned clinical trials, could prevent us from or delay us in submitting BLAs or MAAs for and potentially commercializing HIL-214 or any future vaccine candidates.

Use of HIL-214 or any future vaccine candidates could be associated with adverse side effects, adverse events or other safety risks, which could delay or preclude approval, cause us to suspend or discontinue clinical trials, abandon a vaccine candidate, limit the commercial profile of an approved label or result in other significant negative consequences that could severely harm our business, prospects, operating results and financial condition.

As is the case with biopharmaceuticals generally, it is likely that there may be adverse side effects associated with HIL-214 or any future vaccine candidates’ use. Results of our clinical trials could reveal a high and unacceptable severity and prevalence of expected or unexpected side effects. Vaccine-related side effects could affect subject recruitment or the ability of enrolled subjects to complete the trial or result in potential product liability claims. Undesirable side effects caused by our vaccine candidates when used alone or in combination with approved drugs, biologics or vaccines could cause us or regulatory authorities to interrupt, delay or halt clinical trials and could result in a more restrictive label or lead to the delay or denial of regulatory approval by the FDA or comparable foreign regulatory authorities. Any of these occurrences could severely harm our business, prospectus, operating results and financial condition.

Moreover, if HIL-214 or any future vaccine candidates are associated with undesirable side effects in clinical trials or demonstrate characteristics that are unexpected, we may elect to abandon their development or limit their development to more narrow uses or subpopulations in which the undesirable side effects or other characteristics are less prevalent, less severe or more acceptable from a risk-benefit perspective, which may limit the commercial expectations for the vaccine candidate if approved. We may also be required to modify our development and clinical trial plans based on findings after we commence clinical trials. Many compounds that initially showed promise in early-stage testing have later been found to cause side effects that prevented further development of the compounds. In addition, regulatory authorities may draw different conclusions or require additional testing to confirm these determinations.

In addition to our planned Phase 2b clinical trial in infants and Phase 3 clinical trials, we will need to conduct co-administration trials with other vaccines as required to fit into a pediatric vaccination schedule, as well as other required pediatric trials. It is possible that as we test HIL-214 or any future vaccine candidates in larger, longer and more extensive clinical trials, or if the use of these vaccine candidates becomes more widespread following regulatory approval, more illnesses, injuries, discomforts and other adverse events than were observed in earlier trials, as well as new conditions that did not occur or went undetected, may be discovered. If such side effects become known later in development or upon approval, if any, such findings may harm our

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business, financial condition and prospects significantly. Further, if a serious safety issue is identified in connection with use of HIL-214 in any trials that may be conducted by Takeda, such issues may adversely affect the development potential of HIL-214 or result in regulatory authorities restricting our ability to develop HIL-214.

In addition, if HIL-214 or any future vaccine candidate receives marketing approval, and we or others later identify undesirable side effects caused by such vaccine, a number of potentially significant negative consequences could result, including:

Any of these events could prevent us from achieving or maintaining market acceptance of the particular vaccine candidate, if approved, and could significantly harm our business, results of operations and prospects.

Vaccine candidates are subject to extensive regulation and compliance, which is costly and time consuming, and such regulation and compliance may cause unanticipated delays or prevent the receipt of the required approvals and licenses to commercialize HIL-214 and any future vaccine candidates.

The clinical development, manufacturing, labeling, packaging, storage, record-keeping, advertising, promotion, import, export, marketing, distribution and adverse event reporting, including the submission of safety and other information, of vaccine candidates are subject to extensive regulation by the FDA in the United States, the EMA in the European Union and by comparable foreign regulatory authorities in other foreign markets. In the United States, we are not permitted to market our vaccine candidates until we receive regulatory approval from the FDA in the United States, which is referred to as licensure. The process of obtaining regulatory approval is expensive, often takes many years following the commencement of clinical trials and can vary substantially based upon the type, complexity and novelty of the vaccine candidates involved, as well as the target indications and populations. Approval policies or regulations may change, and the FDA and the EMA have substantial discretion in the vaccine approval process, including the ability to delay, limit or deny approval of a vaccine candidate for many reasons. Despite the time and expense invested in clinical development of vaccine candidates, regulatory approval is never guaranteed. We are not permitted to market any of our vaccine candidates until we receive approval of a BLA from the FDA in the United States or a MAA by the EMA in Europe.

Prior to obtaining approval to commercialize a vaccine candidate in the United States or abroad, we or our collaborators must demonstrate with substantial evidence from adequate and well-controlled clinical trials, and

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to the satisfaction of the FDA, EMA or other comparable foreign regulatory authorities, that such vaccine candidates are safe, pure and potent and effective for their intended uses. Results from preclinical studies and clinical trials can be interpreted in different ways. Even if we believe the preclinical or clinical data for our vaccine candidates are promising, such data may not be sufficient to support approval by the FDA, EMA or comparable foreign regulatory authorities. The FDA, EMA or other comparable foreign regulatory authorities, as the case may be, may also require us to conduct additional preclinical studies or clinical trials for HIL-214 or any future vaccine candidates either prior to approval or post-approval, or may object to elements of our clinical development program.

The FDA, EMA or other comparable foreign regulatory authorities can delay, limit or deny approval of a vaccine candidate for many reasons, including:

Of the large number of vaccines and biologics in development, only a small percentage successfully complete the FDA or foreign regulatory approval processes and are commercialized. The lengthy approval process as well as the unpredictability of future clinical trial results may result in our failing to obtain regulatory approval to market HIL-214 and any future vaccine candidates, which would significantly harm our business, results of operations and prospects.

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With respect to foreign markets, approval procedures vary among countries and, in addition to the foregoing risks, may involve additional product testing, administrative review periods and agreements with pricing authorities. In addition, events raising questions about the safety of certain marketed biopharmaceuticals may result in increased cautiousness by the FDA, EMA and other comparable foreign regulatory authorities in reviewing new drugs based on safety, efficacy or other regulatory considerations and may result in significant delays in obtaining regulatory approvals.

Any delay in obtaining, or inability to obtain, applicable regulatory approvals would prevent us from commercializing HIL-214 or any future vaccine candidates.

We may not be successful in our efforts to investigate HIL-214 in additional age groups or in additional indications and formulations. We may expend our limited resources to pursue a particular indication or formulation for HIL-214 and fail to capitalize on vaccine candidates, indications or formulations that may be more profitable or for which there is a greater likelihood of success.

Because we have limited financial and managerial resources, we focus on specific vaccine candidates, development programs and indications. We plan to focus our initial development efforts on evaluating HIL-214 for the prevention of moderate-to-severe acute gastroenteritis caused by norovirus in infants. We then plan to pursue an immunobridging strategy to expand the development of HIL-214 to older children, adults, older adults and other high-risk groups. Immunobridging studies aim to demonstrate non-inferiority of immune response against a pre-specified criteria between a reference age group (i.e., infants) and target age groups in specific clinical trials. These studies require an appropriate and acceptable serological surrogate and assay and are designed to support supplemental or additional marketing authorization for other age groups without the need for an efficacy trial. However, we may not be able to confirm an appropriate serological surrogate in our infant efficacy trials and even if we do, the FDA, EMA or other comparable foreign regulatory authority may not support our proposed immunobridging criteria or strategy. If either of these events occur, we would be required to conduct additional efficacy clinical trials in adults, which would lead to significant delays and would materially increase the costs of our clinical development program for HIL-214 in these additional age groups. In addition, immunobridging to older adults may be particularly challenging given the incidence rate seen in this population. We may also evaluate alternative formulations or combinations of HIL-214, including through the addition of new norovirus strains to cover relevant or emerging genotypes. As a result of our decision to pursue a given age group, formulation or indication, we may forgo or delay pursuit of opportunities with other vaccine candidates that could have had greater commercial potential. Our resource allocation decisions may cause us to fail to capitalize on viable commercial products or profitable market opportunities. Our spending on current and future research and development programs and vaccine candidates for specific indications may not yield any commercially viable vaccine candidates. If we do not accurately evaluate the commercial potential or target market for a particular vaccine candidate, we may relinquish valuable rights to that vaccine candidate through collaborations, license agreements and other similar arrangements in cases in which it would have been more advantageous for us to retain sole development and commercialization rights to such vaccine candidate.

If the incidence rates of infection for the specific pathogens we are targeting are smaller than we believe they are, our clinical development may be adversely affected, and our business may suffer.

Our projections of both the number of people who have a norovirus infection, as well as the subset of people with genotypes who have the potential to benefit from treatment with HIL-214 and any future vaccine candidates, are based on our estimates. These estimates have been derived from a variety of sources, including scientific literature, epidemiologic surveys, and market research based on healthcare databases, and may prove to be incorrect or imprecise. In addition, precise incidence for the noroviruses we aim to address with HIL-214 and any future vaccine candidates may vary from season to season. Further, new trials or information may

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change the estimated incidence of these diseases. Our planned clinical trial sizes are based on our current estimates for rates of infection for the specific norovirus targeted by HIL-214, and such rates and estimates may be affected by the COVID-19 pandemic. For example, measures taken that may limit social interaction or prevent reopening of high-transmission settings may reduce incidence rates. If our estimates are incorrect, this may impact the number of subjects that need to be recruited for our clinical trials, the time required to evaluate trial endpoints in these subjects and the overall time to complete the trial, may result in us having to repeat a clinical trial, or could impact the likelihood of success of our clinical development.

Interim, topline and preliminary data from our preclinical studies and clinical trials that we announce or publish from time to time may change as more subject data become available and are subject to audit and verification procedures that could result in material changes in the final data.

From time to time, we may publicly disclose preliminary or topline data from our preclinical studies and clinical trials, which is based on a preliminary analysis of then-available data, and the results and related findings and conclusions are subject to change following a more comprehensive review of the data related to the particular study or trial. We also make assumptions, estimations, calculations and conclusions as part of our analyses of data, and we may not have received or had the opportunity to fully and carefully evaluate all data. As a result, the topline or preliminary results that we report may differ from future results of the same studies or trials, or different conclusions or considerations may qualify such results, once additional data have been received and fully evaluated. Topline and preliminary data also remain subject to audit and verification procedures that may result in the final data being materially different from the topline or preliminary data we previously published. As a result, topline and preliminary data should be viewed with caution until the final data are available.

From time to time, we may also disclose interim data from our preclinical studies and clinical trials. Interim data from clinical trials that we may complete are subject to the risk that one or more of the clinical outcomes may materially change as patient enrollment continues and more patient data become available. Adverse differences between interim data and final data could significantly harm our business prospects. Further, disclosure of interim data by us or by our competitors could result in volatility in the price of our common stock.

Further, others, including regulatory agencies, may not accept or agree with our assumptions, estimates, calculations, conclusions or analyses or may interpret or weigh the importance of data differently, which could impact the value of the particular program, the approvability or commercialization of the particular vaccine candidate or product and our company in general. In addition, the information we choose to publicly disclose regarding a particular study or clinical trial is based on what is typically extensive information, and you or others may not agree with what we determine is material or otherwise appropriate information to include in our disclosure. . If the interim, topline, or preliminary data that we report differ from actual results, or if others, including regulatory authorities, disagree with the conclusions reached, our ability to obtain approval for, and commercialize, HIL-214 and any future vaccine candidates may be harmed, which could harm our business, operating results, prospects or financial condition.

Changes in methods of vaccine candidate manufacturing or formulation may result in additional costs or delay.

As vaccine candidates progress through clinical trials to marketing approval and commercialization, it is common that various aspects of the development program, such as manufacturing methods and formulation, are altered along the way in an effort to optimize safety, efficacy, yield and manufacturing batch size, minimize costs and achieve consistent quality and results. Such changes carry the risk that they will not achieve these intended objectives. For example, the manufacturing process being used to produce clinical material for our planned clinical trials is different than that used in prior trials of HIL-214. These changes and any future changes we may make to HIL-214 or any future vaccine candidates may cause such candidates to perform

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differently and affect the results of future clinical trials conducted with the altered materials. We plan to review and report safety and immunogenicity data from the first approximately 200 subjects in our planned Phase 2b clinical trial to assess HIL-214 manufactured using this new process. Such changes or negative trial results could delay initiation or completion of clinical trials, require the conduct of bridging studies or clinical trials or the repetition of one or more studies or clinical trials, increase development costs, delay potential marketing approval and jeopardize our ability to commercialize HIL-214 or any future vaccine candidates, if approved, and generate revenue.

Disruptions at the FDA and other government agencies caused by funding shortages or global health concerns could hinder their ability to hire, retain or deploy key leadership and other personnel, or otherwise prevent new or modified products from being developed, approved or commercialized in a timely manner or at all, which could negatively impact our business.

The ability of the FDA and other government agencies to review and approve new products can be affected by a variety of factors, including government budget and funding levels, statutory, regulatory and policy changes, a government agency’s ability to hire and retain key personnel and accept the payment of user fees, and other events that may otherwise affect the government agency’s ability to perform routine functions. Average review times at the FDA and other government agencies have fluctuated in recent years as a result. In addition, government funding of other government agencies that fund research and development activities is subject to the political process, which is inherently fluid and unpredictable. Disruptions at the FDA and other agencies may also slow the time necessary for new biologics or modifications to approved biologics to be reviewed and/or approved by necessary government agencies, which would adversely affect our business. For example, over the last several years, the U.S. government has shut down several times and certain regulatory agencies, such as the FDA, have had to furlough critical employees and stop critical activities.

Separately, in response to the COVID-19 pandemic, in March 2020, the FDA announced its intention to postpone most inspections of foreign manufacturing facilities, and on March 18, 2020, the FDA temporarily postponed routine surveillance inspections of domestic manufacturing facilities. Subsequently, in July 2020, the FDA resumed certain on-site inspections of domestic manufacturing facilities subject to a risk-based prioritization system. The FDA utilized this risk-based assessment system to assist in determining when and where it was safest to conduct prioritized domestic inspections. Additionally, on April 15, 2021, the FDA issued a guidance document in which the FDA described its plans to conduct voluntary remote interactive evaluations of certain drug manufacturing facilities and clinical research sites, among other facilities. According to the guidance, the FDA may request such remote interactive evaluations where the FDA determines that remote evaluation would be appropriate based on mission needs and travel limitations. In May 2021, the FDA outlined a detailed plan to move toward a more consistent state of inspectional operations, and in July 2021, the FDA resumed standard inspectional operations of domestic facilities. More recently, the FDA has continued to monitor and implement changes to its inspectional activities to ensure the safety of its employees and those of the firms it regulates as it adapts to the evolving COVID-19 pandemic, including by temporarily halting certain activities from December 29, 2021 to February 7, 2022. Regulatory authorities outside the United States may adopt similar restrictions or other policy measures in response to the COVID-19 pandemic. In addition, regulatory agencies such as the FDA and EMA slowed down the review of non-COVID vaccine-related efforts since 2020 in order to handle the workload and priority needed for review of COVID-related vaccines. If a prolonged government shutdown occurs, or if global health concerns continue to prevent the FDA or other regulatory authorities from conducting their regular inspections, reviews or other regulatory activities, it could significantly impact the ability of the FDA or other regulatory authorities to timely review and process our regulatory submissions, which could have a material adverse effect on our business.

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Risks related to our reliance on third parties

We heavily rely on the Takeda License to provide us with intellectual property rights to develop and commercialize HIL-214. If the Takeda License is terminated, we would lose our rights to develop and commercialize HIL-214.

Pursuant to the Takeda License, we have, among other things, secured an exclusive license from Takeda under certain patents and know-how relating to HIL-214 to commercialize HIL-214 globally, with the exception of Japan. The Takeda License expires on a country-by-country basis and product-by-product basis upon the expiration of the applicable royalty term with respect to each product in each country, as applicable, or in its entirety upon the expiration of the royalty term with respect to the last product commercialized in the last country, unless terminated earlier. We may terminate the Takeda License in its entirety without cause upon six months’ prior written notice. We and Takeda may terminate the Takeda License in the case of the other party’s insolvency, or upon prior written notice within a specified time period for the other party’s material uncured breach. Takeda may terminate the Takeda License in its entirety if we challenge the licensed patents, or if we assist any third party in challenging such patents. In addition, if any of the regulatory milestones or other cash payments become due under the terms of the Takeda License, we may not have sufficient funds available to meet our obligations, Takeda has the right to terminate the Takeda License upon our uncured failure to pay Takeda. If the Takeda License is terminated, we would lose our rights to develop and commercialize HIL-214, which in turn would have a material adverse effect on our business, operating results and prospects. For additional information on the Takeda License, see “Business—License agreement with Takeda.”

We rely on third parties to conduct preclinical studies and clinical trials. If these third parties do not successfully carry out their contractual duties, comply with applicable regulatory requirements or meet expected deadlines, our development programs and our ability to seek or obtain regulatory approval for or commercialize HIL-214 and any future vaccine candidates may be delayed.

We depend on third parties to conduct our preclinical studies and clinical trials for HIL-214 and any future vaccine candidates. Specifically, we rely on, and will continue to rely on, medical institutions, clinical investigators, CROs and consultants to conduct preclinical studies and clinical trials, in each case in accordance with our clinical protocols and regulatory requirements. These CROs, investigators and other third parties play a significant role in the conduct and timing of these trials and subsequent collection and analysis of data. Though we expect to carefully manage our relationships with our CROs, investigators and other third parties, there can be no assurance that we will not encounter challenges or delays in the future or that these delays or challenges will not have a material adverse impact on our business, financial condition and prospects. Further, while we will have agreements governing the activities of our third-party contractors, we have limited influence over their actual performance. Nevertheless, we are responsible for ensuring that each of our preclinical studies and clinical trials are conducted in accordance with the applicable protocol and legal, regulatory and scientific standards and requirements, and our reliance on our CROs and other third parties does not relieve us of our regulatory responsibilities. In addition, we and our CROs are required to comply with GCP requirements, which are regulations and guidelines enforced by the FDA, EMA and comparable foreign regulatory authorities for HIL-214 and any future vaccine candidates in clinical development. Regulatory authorities enforce these GCPs through periodic inspections of trial sponsors, principal investigators and trial sites. If we or any of our CROs or trial sites fail to comply with applicable GCPs, the clinical data generated in our clinical trials may be deemed unreliable, and the FDA, EMA or comparable foreign regulatory authorities may require us to perform additional clinical trials before approving our marketing applications. Furthermore, our clinical trials must be conducted with vaccine candidates produced under cGMP regulations. Failure to comply with these regulations may require us to repeat clinical trials or recall batches of our vaccine candidate, which would delay the regulatory approval process.

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There is no guarantee that any of our CROs, investigators or other third parties will devote adequate time and resources to our preclinical studies or clinical trials or perform as contractually required. If any of these third parties fails to meet expected deadlines, adhere to our clinical protocols or meet regulatory requirements, or otherwise performs in a substandard manner, our clinical trials may be extended, delayed or terminated. In addition, many of the third parties with whom we contract may also have relationships with other commercial entities, including our competitors, for whom they may also be conducting preclinical studies, clinical trials or other development activities that could harm our competitive position.

If any of our relationships with these third parties terminate, we may not be able to enter into arrangements with alternative third parties on commercially reasonable terms or at all. Switching or adding additional CROs, investigators and other third parties involves additional cost and requires our management’s time and focus. In addition, there is a natural transition period when a new CRO commences work. As a result, delays occur, which can materially impact our ability to meet our desired clinical development timelines. Though we work to carefully manage our relationships with our CROs, investigators and other third parties, there can be no assurance that we will not encounter challenges or delays in the future or that these delays or challenges will not have a material adverse impact on our business, financial condition and prospects.

We currently rely on third parties for the manufacture of HIL-214 for clinical development and expect to continue to rely on third parties for the foreseeable future. This reliance on third parties increases the risk that we will not have sufficient quantities of HIL-214 or such quantities at an acceptable cost, which could delay, prevent or impair our development or potential commercialization efforts.

We do not own or operate manufacturing facilities and have no plans to develop our own clinical or commercial-scale manufacturing capabilities. Pursuant to the Takeda License, we entered into a clinical manufacturing and supply agreement with Takeda for the supply of HIL-214 for our planned Phase 2b clinical trial in infants. In addition, we are exploring options for clinical supply of HIL-214 from additional third-party contract manufacturers for future clinical trials. As a result, we currently rely, and expect to continue to rely, on third parties for the manufacture of HIL-214, placebo and related raw materials for clinical development, as well as for commercial manufacture if HIL-214 or any future vaccine candidates receives marketing approval. The facilities used by third-party manufacturers to manufacture HIL-214 must be approved by the FDA and any comparable foreign regulatory authority pursuant to inspections that will be conducted after we submit a BLA to the FDA or any comparable submission to a foreign regulatory authority. We do not control the manufacturing process of, and are completely dependent on, third-party manufacturers for compliance with cGMP requirements for manufacture of products. In addition, we have no control over the ability of third-party manufacturers to maintain adequate quality control, quality assurance and qualified personnel. Furthermore, the process of manufacturing biologics is complex and highly susceptible to product loss due to contamination, equipment failure, improper installation or operation of equipment, vendor or operator error, inconsistency in yields, variability in product characteristics and difficulties in scaling the production process. Even minor deviations from normal manufacturing processes could result in reduced production yields, product defects, other supply disruptions and higher costs. If microbial, viral or other contaminations are discovered at the facilities of our third-party manufacturers, such facilities may need to be closed for an extended period of time to investigate and remedy the contamination, which could delay clinical trials, result in higher costs of drug product and adversely affect our business. Further, our clinical supply of HIL-214 and placebo for use in future clinical trials has a shelf life that may expire prior to the full enrollment of our planned clinical trials causing similar delays or other supply disruptions. Any performance failure on the part of our third-party manufacturers could delay clinical development or marketing approval of HIL-214, and may adversely affect our future profit margins and our ability to commercialize any vaccines that receive marketing approval on a timely and competitive basis.

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In addition, we do not have any long-term commitments or supply agreements with any third-party manufacturers. We may be unable to establish any supply agreements with additional third-party manufacturers or to do so on acceptable terms, which increases the risk of failing to timely obtain sufficient quantities of HIL-214 or such quantities at an acceptable cost. Even if we are able to establish long-term agreements with third-party manufacturers, reliance on third-party manufacturers entails additional risks, including:

There are a limited number of manufacturers that operate under cGMP regulations and that might be capable of manufacturing for us, and HIL-214 and any future vaccine candidates that we may develop may compete with other vaccine candidates and products for access to such manufacturers and manufacturing facilities. In addition, the COVID-19 pandemic has reduced manufacturing capacity worldwide and limited access to materials needed to manufacture key components of HIL-214. Increased competition amongst developers to access manufacturers and materials could increase the costs of, or otherwise limit our ability to, manufacture HIL-214 or any future vaccine candidates.

If materials manufactured by our third-party manufacturers do not conform to our specifications or the regulatory requirements necessary for use in clinical trials, we may experience delays in our development efforts or may need to find alternative manufacturing facilities, which would significantly impact our ability to obtain regulatory approval for or commercialize our vaccine candidates, if approved.

Our third-party manufacturers may be unable to successfully manufacture material that conforms to our specifications and the strict regulatory requirements of the FDA or any comparable foreign regulatory authority. In order for us to use the material manufactured by third-party manufacturers, their manufacturing facilities in which our materials are produced must comply with applicable laws and regulations governing the manufacture of biologic product candidates, and upon a request for marketing authorization, these facilities must be authorized for the manufacture of HIL-214 and any future vaccine candidates in connection with any approval of a marketing application we submit. If the FDA or any comparable foreign regulatory authority determines that such facilities are noncompliant or does not authorize these facilities to manufacture our vaccine candidates or if it withdraws any such authorization in the future, we may need to find alternative manufacturing facilities, which would significantly impact our ability to develop, obtain regulatory approval for or market our vaccine candidates, if approved. For example, in June 2020, the FDA issued a warning letter to Takeda following a routine inspection of aseptic (sterile) drug product manufacturing at Takeda’s manufacturing facility located in Hikari, Yamaguchi (the Hikari Facility). Takeda also manufactures HIL-214, an aseptic product, at the Hikari Facility. The warning letter stated that the FDA was not satisfied with Takeda’s response to an FDA Form 483 issued to Takeda following the inspection and cited significant violations of cGMP for finished aseptic pharmaceuticals. We have not experienced any clinical supply constraints to date as a result of these issues and the issues relating to the Hikari Facility were closed by the FDA in October 2021. We currently do not expect that the issues relating to the Hikari Facility will have an effect on our ongoing or future clinical trials. While we are seeking to identify and secure additional third-party contract manufacturers, we may be unable to do so at an acceptable cost, or at all, which could significantly impact our ability to obtain

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regulatory approval for or commercialize HIL-214, if approved. Our failure, or the failure of our third-party manufacturers, to comply with applicable regulations could result in sanctions being imposed on us, including clinical holds, fines, injunctions, civil penalties, delays, suspension or withdrawal of approvals, seizures or recalls of vaccine candidates or products, operating restrictions and criminal prosecutions, any of which could significantly and adversely affect supplies of our products. Additionally, our third-party manufacturers may rely on single source suppliers for certain of the raw materials for our preclinical and clinical product supplies. If current or future suppliers are delayed or unable to supply sufficient raw materials to manufacture product for our preclinical studies and clinical trials, we may experience delays in our development efforts as materials are obtained or we locate and qualify new raw material manufacturers.

Our or a third party’s failure to execute on our manufacturing requirements on commercially reasonable terms and in compliance with cGMP or other regulatory requirements could adversely affect our business in a number of ways, including:

Any performance failure on the part of Takeda or other future manufacturers could delay clinical development or marketing approval, and any related remedial measures may be costly or time consuming to implement. In addition, our current and anticipated future dependence upon others for the manufacture of HIL-214 and any future vaccine candidates may adversely affect our future profit margins and our ability to commercialize any vaccines that receive marketing approval on a timely and competitive basis.

Our reliance on third parties requires us to share our trade secrets, which increases the possibility that a competitor or other third party will discover them or that our trade secrets will be misappropriated or disclosed.

Because we currently rely on Takeda to manufacture HIL-214 and to perform quality testing, we must, at times, share our proprietary technology and confidential information, including trade secrets, with them. We seek to protect our proprietary technology, in part, by entering into confidentiality agreements, and, if applicable, material transfer agreements, collaborative research agreements, consulting agreements or other similar agreements with our collaborators, advisors, employees and consultants prior to beginning research or disclosing proprietary information. These agreements typically limit the rights of the third parties to use or disclose our confidential information, including our trade secrets. Despite the contractual provisions employed when working with third parties, the need to share trade secrets and other confidential information increases the risk that such trade secrets become known by our competitors or other third parties, are intentionally or inadvertently incorporated into the technology of others or are disclosed or used in violation of these agreements. Given that our proprietary position is based, in part, on our know-how and trade secrets and despite our efforts to protect our trade secrets, a competitor’s or other third party’s discovery of our proprietary technology and confidential information or other unauthorized use or disclosure of such technology or information would impair our competitive position and may have a material adverse effect on our business, financial condition, results of operations and prospects.

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We may seek to enter into collaborations, license agreements and other similar arrangements and may not be successful in doing so, and even if we are, we may relinquish valuable rights and may not realize the benefits of such relationships.

We may seek to enter into collaborations, joint ventures, license agreements and other similar arrangements for the development or commercialization of HIL-214 and any future vaccine candidates, due to capital costs required to develop or commercialize the vaccine candidate or manufacturing constraints. We may not be successful in our efforts to establish or maintain such collaborations because our research and development pipeline may be insufficient, HIL-214 or any future vaccine candidates may be deemed to be at too early of a stage of development for collaborative effort or third parties may not view such vaccine candidates as having the requisite potential to demonstrate safety, immunogenicity and efficacy or significant commercial opportunity. In addition, we face significant competition in seeking appropriate strategic partners, and the negotiation process can be time-consuming and complex.

Even if we are successful in our efforts to establish such collaborations, the terms that we agree upon may not be favorable to us. For example, we may need to relinquish valuable rights to our future revenue streams, research programs, intellectual property or vaccine candidates, or grant licenses on terms that may not be favorable to us, as part of any such arrangement, and such arrangements may restrict us from entering into additional agreements with other potential collaborators. In addition, if we enter into such collaborations, we will have limited control over the amount and timing of resources that our collaborators will dedicate to the development or commercialization of our vaccine candidates. Our ability to generate revenue from these arrangements will depend on any future collaborators’ abilities to successfully perform the functions assigned to them in these arrangements. We cannot be certain that, following a collaboration, license or strategic transaction, we will achieve an economic benefit that justifies such transaction. Furthermore, we may not be able to maintain such collaborations if, for example, the development or approval of a vaccine candidate is delayed, the safety of a vaccine candidate is questioned or the sales of an approved vaccine candidate are unsatisfactory.

Collaborations involving HIL-214 or any future vaccine candidates would pose significant risks to us, including the following:

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Any termination of collaborations we enter into in the future, or any delay in entering into collaborations related to HIL-214 or any future vaccine candidates, could delay the development and commercialization of such vaccine candidates and reduce their competitiveness if they reach the market, which could have a material adverse effect on our business, financial condition and results of operations.

Risks related to commercialization of HIL-214 and any future vaccine candidates

Even if we receive regulatory approval for HIL-214 and any future vaccine candidates, we will be subject to ongoing regulatory obligations and continued regulatory review, which may result in significant additional

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expense. Additionally, HIL-214 and any future vaccine candidates, if approved, could be subject to labeling and other restrictions on marketing or withdrawal from the market, and we may be subject to penalties if we fail to comply with regulatory requirements or if we experience unanticipated problems with our vaccine candidates, when and if any of them are approved.

Any regulatory approvals that we may receive for HIL-214 or any future vaccine candidates will require the submission of reports to regulatory authorities, subject us to surveillance to monitor the safety and efficacy of the product, may contain significant limitations related to use restrictions for specified age groups, warnings, precautions or contraindications, and may include burdensome post-approval study or risk management requirements. For example, the FDA may require a REMS as a condition of approval of HIL-214 or any future vaccine candidates, which could include requirements for a medication guide, physician communication plans or additional elements to ensure safe use, such as restricted distribution methods, patient registries and other risk minimization tools. In addition, if the FDA or a comparable foreign regulatory authority approves HIL-214 or any future vaccine candidates, the manufacturing processes, labeling, packaging, distribution, adverse event reporting, storage, advertising, promotion, import, export and recordkeeping for our products will be subject to extensive and ongoing regulatory requirements. These requirements include submissions of safety and other post-marketing information and reports, registration, as well as continued compliance with cGMPs and GCP requirements for any clinical trials that we conduct post-approval. Failure to comply with regulatory requirements or later discovery of previously unknown problems with our products, including adverse events of unanticipated severity or frequency, or with our third-party manufacturers or manufacturing processes, may result in, among other things:

The occurrence of any event or penalty described above may inhibit our ability to commercialize HIL-214 or any future vaccine candidates and generate revenue and could require us to expend significant time and resources in response and could generate negative publicity.

The FDA’s and other regulatory authorities’ policies may change and additional government regulations may be promulgated that could prevent, limit or delay marketing authorization of any vaccine candidates we develop. If we are slow or unable to adapt to changes in existing requirements or the adoption of new requirements or policies, or if we are not able to maintain regulatory compliance, we may be subject to enforcement action and we may not achieve or sustain profitability.

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HIL-214 and any future vaccine candidates for which we intend to seek approval as biologic products may face competition sooner than anticipated.

The Patient Protection and Affordable Care Act, as amended by the Health Care and Education Reconciliation Act (the ACA), includes a subtitle called the Biologics Price Competition and Innovation Act of 2009 (BPCIA), which created an abbreviated approval pathway for biological products that are biosimilar to or interchangeable with an FDA-licensed reference biological product. Under the BPCIA, an application for a highly similar or “biosimilar” product may not be submitted to the FDA until four years following the date that the reference product was first approved by the FDA. In addition, the approval of a biosimilar product may not be made effective by the FDA until 12 years from the date on which the reference product was first approved. During this 12-year period of exclusivity, the FDA may approve a full BLA for the competing product containing the sponsor’s own preclinical data and data from adequate and well-controlled clinical trials to demonstrate the safety, purity and potency of their product. We believe that HIL-214 or any future vaccine candidates approved as a biological product under a BLA should qualify for the 12-year period of exclusivity. However, there is a risk that this exclusivity could be shortened due to congressional action or otherwise, or that the FDA will not consider our vaccine candidates to be reference products for competing products, potentially creating the opportunity for competition sooner than anticipated.

The commercial success of HIL-214 or any future vaccine candidates will depend upon the degree of market acceptance of such vaccine candidates by healthcare providers, vaccine recipients, healthcare payors and others in the medical community, which is reliant on a number of factors, including the receipt of a preferred recommendation from the ACIP or other foreign national immunization technical advisory groups.

HIL-214 and any future vaccine candidates may not be commercially successful. Even if HIL-214 or any future vaccine candidates receive regulatory approval, they may not gain market acceptance among healthcare providers, individuals within our target population, healthcare payors, NITAGs or the medical community. The commercial success of any of HIL-214 or any future vaccine candidates will depend significantly on the broad adoption and use of the resulting product by these individuals and organizations for approved indications. The degree of market acceptance of our products will depend on a number of factors, including:

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In the United States, the ACIP develops vaccine recommendations, and there are similar NITAG agencies in other jurisdictions around the world that develop vaccine recommendations. To develop its recommendations, the ACIP forms working groups that gather, analyze and prepare scientific information. The ACIP also considers many of the factors above, as well as myriad additional factors such as the value of vaccination for the target population regarding the outcomes, health economic data and implementation issues. The ACIP recommendations are also made within categories, such as in an age group or a specified risk group, and vaccines that receive a preferred ACIP recommendation are generally widely adopted in the United States. Following completion of our Phase 2b and 3 clinical trials of HIL-214 in infants, if achieved, ACIP may decline to recommend our vaccine. In addition, the failure of any other developer of norovirus vaccine candidates to secure such an ACIP recommendation, or any limitations of any ACIP recommendations secured by any other developers, may limit the market opportunity of HIL-214 or any future vaccine candidates. If HIL-214 or any future vaccine candidate is approved but does not achieve an adequate level of acceptance by physicians, hospitals, healthcare payors or patients, we may not generate sufficient revenue from that product and may not become or remain profitable.

The FDA and other regulatory agencies actively enforce the laws and regulations prohibiting the promotion of off-label uses. If we are found or alleged to have improperly promoted off-label uses, we may become subject to significant liability.

The FDA and other regulatory agencies strictly regulate the promotional claims that may be made about biologics. These regulations include standards and restrictions for direct-to-consumer advertising, industry-sponsored scientific and educational activities, promotional activities involving the internet and off-label promotion.

Any regulatory approval that the FDA grants is limited to those indications and patient populations for which a biologic product is deemed to be safe, pure and potent by the FDA. While physicians in the United States may choose, and are generally permitted, to prescribe products for uses that are not described in the product’s labeling and for uses that differ from those tested in clinical trials and approved by the FDA, our ability to promote HIL-214 and any future vaccine candidates, if approved, will be narrowly limited to those indications and populations that are specifically approved by the FDA, and if we are found to have promoted such off-label uses, we may become subject to significant liability. For example, the federal government has levied large civil and criminal fines against companies for alleged improper promotion and has enjoined several companies from

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engaging in off-label promotion. The government has also required companies to enter into consent decrees or imposed permanent injunctions under which specified promotional conduct is changed or curtailed. If we cannot successfully manage the promotion of HIL-214 or any future vaccine candidates, if approved, we could become subject to significant liability, which would materially adversely affect our business and financial condition.

The successful commercialization of HIL-214 or any future vaccine candidates, if approved, will depend in part on the extent to which governmental authorities and health insurers establish coverage, adequate reimbursement levels and favorable pricing policies. Failure to obtain or maintain coverage and adequate reimbursement for our products could limit our ability to market those products and decrease our ability to generate revenue.

The availability of coverage and the adequacy of reimbursement by governmental healthcare programs such as Medicare and Medicaid, private health insurers and other third-party payors are essential for most vaccine recipients to be able to afford prescription medications such as HIL-214 and any future vaccine candidates, if approved. Our ability to achieve coverage and acceptable levels of reimbursement for our products by third-party payors will have an effect on our ability to successfully commercialize those products. Accordingly, we will need to successfully implement a coverage and reimbursement strategy for any approved vaccine candidate. Even if we obtain coverage for a given product by a third-party payor, the resulting reimbursement payment rates may not be adequate or may require copayments that vaccine recipients find unacceptably high. We cannot be sure that coverage and reimbursement in the United States, the European Union or elsewhere will be available, or at an acceptable level, for any product that we may develop, and any reimbursement that may become available may be decreased or eliminated in the future.

There is significant uncertainty related to third-party payor coverage and reimbursement of newly approved products. In the United States, third-party payors, including private and governmental payors, such as the Medicare and Medicaid programs, play an important role in determining the extent to which new vaccines will be covered. Some third-party payors may require pre-approval of coverage for new or innovative products before they will reimburse healthcare providers who use such products. It is difficult to predict at this time what third-party payors will decide with respect to the coverage and reimbursement for HIL-214 and any future vaccine candidates. In addition, certain ACA marketplace and other private payor plans are required to include coverage for certain preventative services, including vaccinations recommended by the ACIP and on the CDC’s National Immunization Program, without cost share obligations (i.e., co-payments, deductibles or co-insurance) for plan members. Children up to 18 years of age without other health insurance coverage may be eligible to receive such vaccinations free-of-charge through the CDC’s Vaccines for Children program. For Medicare beneficiaries, vaccines may be covered for reimbursement under either Medicare Part B or Part D depending on several criteria, including the type of vaccine and the beneficiary’s coverage eligibility. If HIL-214 or any future vaccine candidates, if approved, are reimbursed only under the Part D program, healthcare providers may be less willing to use our products because of the claims adjudication costs and time related to the claims adjudication process and collection of co-payment associated with the Part D program.

Obtaining and maintaining reimbursement status is time-consuming, costly and uncertain. The Medicare and Medicaid programs increasingly are used as models for how private payors and other governmental payors develop their coverage and reimbursement policies for drugs. However, no uniform policy for coverage and reimbursement for products exists among third-party payors in the United States. Therefore, coverage and reimbursement for products can differ significantly from payor to payor. As a result, the coverage determination process is often a time-consuming and costly process that will require us to provide scientific and clinical support for the use of our products to each payor separately, with no assurance that coverage and adequate reimbursement will be applied consistently or obtained in the first instance. Furthermore, rules and

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regulations regarding reimbursement change frequently and, in some cases, at short notice, and we believe that changes in these rules and regulations are likely.

Outside the United States, international operations are generally subject to extensive governmental price controls and other market regulations, and we believe the increasing emphasis on cost-containment initiatives in Europe and other countries has and will continue to put pressure on the pricing and usage of our products. In many countries, the prices of medical products are subject to varying price control mechanisms as part of national health systems. Other countries allow companies to fix their own prices for medical products but monitor and control company profits. Additional foreign price controls or other changes in pricing regulation could restrict the amount that we are able to charge for our products. Accordingly, in markets outside the United States, the reimbursement for our products may be reduced compared with the United States and may be insufficient to generate commercially reasonable revenue and profits.

Moreover, increasing efforts by governmental and third-party payors in the United States and abroad to cap or reduce healthcare costs may cause such organizations to limit both coverage and the level of reimbursement for newly approved products and, as a result, they may not cover or provide adequate payment for our products. We expect to experience pricing pressures in connection with the sale of any of our products due to the trend toward managed healthcare, the increasing influence of health maintenance organizations and additional legislative changes. The downward pressure on healthcare costs in general, and prescription drugs, surgical procedures and other treatments in particular, has become very intense. As a result, increasingly high barriers are being erected to the entry of new products.

We face significant competition, and if our competitors develop technologies or vaccine candidates more rapidly than we do or their technologies are more effective, our business and our ability to develop and successfully commercialize products may be adversely affected.

Our industry is characterized by rapid advancing technologies, intense competition and a strong emphasis on proprietary and novel products. The current vaccine market is concentrated among a few global biopharmaceutical companies including BioNTech, CSL Bering, GlaxoSmithKline, Merck, Moderna, Pfizer, Sanofi, and Takeda, which together account for the majority of global vaccine sales. Other pharmaceutical and biotechnology companies, academic institutions, governmental agencies, and public and private research institutions are also active in the vaccine market given the continuing global need for both existing and new vaccines. We also compete with these organizations to recruit management, scientists and clinical development personnel, which could negatively affect our level of expertise and our ability to execute our business plan. Any vaccine candidates that we successfully develop and commercialize will compete with existing therapies and new therapies that may become available in the future. We will also face competition in establishing clinical trial sites, enrolling subjects for clinical trials and in identifying and in-licensing intellectual property related to new vaccine candidates. Smaller or early-stage companies may also prove to be significant competitors, particularly through collaborative arrangements with large and established companies.

There are currently no approved vaccines for the prevention of norovirus-related illness. While we are not aware of all of our competitors’ efforts, based on public statements, we believe that several companies are in various stages of developing a vaccine for norovirus including China National Biotec, Chongqing Zhifei Biological, Icon Genetics and Vaxart. We believe that China National Biotec, Chongqing Zhifei Biological and Icon Genetics are also focused on developing a vaccine consisting of VLPs representing the GI and GII genogroups of norovirus. Further, we believe that China National Biotec and Chongqing Zhifei Biological are also developing a pediatric vaccine for the prevention of norovirus-related illness.

Many of our competitors have significantly greater financial, technical, manufacturing, marketing, sales and supply resources or experience than we do. If we successfully obtain approval for HIL-214 or any future vaccine

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candidate, we will face competition based on many different factors, including the safety and effectiveness of our products, the ease with which our products can be administered, the extent to which vaccine recipients accept relatively new vaccines, the timing and scope of regulatory approvals for these products, the availability and cost of manufacturing, marketing and sales capabilities, price, reimbursement coverage and patent position. Competing products could present superior treatment alternatives, including by being more effective, safer, more convenient, less expensive or marketed and sold more effectively than any products we may develop. Competing products may render HIL-214 or any future vaccine candidates we develop obsolete or noncompetitive before we recover the expense of developing and commercializing such vaccine candidate. If we are unable to compete effectively, our opportunity to generate revenue from the sale of our products we may develop, if approved, could be adversely affected.

We currently have no marketing and sales organization and have no experience as a company in commercializing products, and we may need to invest significant resources to develop these capabilities. If we are unable to establish marketing and sales capabilities or enter into agreements with third parties to market and sell our products, we may not be able to generate product revenue.

We have no internal sales, marketing or distribution capabilities, nor have we commercialized a product. If HIL-214 or any future vaccine candidates ultimately receives regulatory approval, we must build a marketing and sales organization with technical expertise and supporting distribution capabilities to commercialize each such product in major markets, which will be expensive and time-consuming. Alternatively, we may need to collaborate with third parties that have direct sales forces and established distribution systems, in lieu of or to augment our own sales force and distribution systems. We plan to independently commercialize HIL-214, if approved, in the United States by building a highly-targeted sales force to support the adoption of HIL-214 and we plan to seek one or more partners with existing commercial infrastructure and expertise in markets outside the United States. We have no prior experience as a company with the marketing, sale or distribution of biopharmaceutical products and there are significant risks involved in the building and managing of a sales organization, including our ability to hire, retain and incentivize qualified individuals, generate sufficient sales leads, provide adequate training to sales and marketing personnel and effectively manage a geographically dispersed sales and marketing team. Any failure or delay in the development of our internal sales, marketing and distribution capabilities would adversely impact the commercialization of these products. We may not be able to enter into collaborations or hire consultants or external service providers to assist us in sales, marketing and distribution functions on acceptable financial terms, or at all. In addition, our product revenue and our profitability, if any, may be lower if we rely on third parties for these functions than if we were to market, sell and distribute any products that we develop ourselves. We likely will have little control over such third parties, and any of them may fail to devote the necessary resources and attention to sell and market our products effectively. If we are not successful in commercializing our products, either on our own or through arrangements with one or more third parties, we may not be able to generate any future product revenue and we would incur significant additional losses.

Our future growth may depend, in part, on our ability to operate in foreign markets, where we would be subject to additional regulatory burdens and other risks and uncertainties.

Our future growth may depend, in part, on our ability to develop and commercialize HIL-214 and any future vaccine candidates in foreign markets, particularly Europe. We are not permitted to market or promote any vaccine candidate before we receive regulatory approval from applicable regulatory authorities in foreign markets, and we may never receive such regulatory approvals for HIL-214 or any future vaccine candidates. To obtain separate regulatory approval in many other countries we must comply with numerous and varying regulatory requirements regarding safety and efficacy and governing, among other things, clinical trials,

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commercial sales, pricing and distribution of HIL-214 and any future vaccine candidates. Approval procedures may be more onerous than those in the United States and may require that we conduct additional preclinical studies or clinical trials. If we obtain regulatory approval of vaccine candidates and ultimately commercialize our products in foreign markets, we would be subject to additional risks and uncertainties, including:

Risks related to our business operations and industry

Our operating results may fluctuate significantly, which makes our future operating results difficult to predict and could cause our operating results to fall below expectations or any guidance we may provide.

Our quarterly and annual operating results may fluctuate significantly, which makes it difficult for us to predict our future operating results. These fluctuations may occur due to a variety of factors, many of which are outside of our control, including, but not limited to:

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The cumulative effects of these factors could result in large fluctuations and unpredictability in our quarterly and annual operating results. As a result, comparing our operating results on a period-to-period basis may not be meaningful. Investors should not rely on our past results as an indication of our future performance.

This variability and unpredictability could also result in our failing to meet the expectations of industry or financial analysts or investors for any period. If our revenue or operating results fall below the expectations of analysts or investors or below any forecasts we may provide to the market, or if the forecasts we provide to the market are below the expectations of analysts or investors, the price of our common stock could decline substantially. Such a stock price decline could occur even when we have met any previously publicly stated revenue or earnings guidance we may provide.

We are dependent on the services of our management and other clinical and scientific personnel, and if we are not able to retain these individuals or recruit additional management or clinical and scientific personnel, our business will suffer.

Our success depends in part on our continued ability to attract, retain and motivate highly qualified management, clinical and scientific personnel. We are highly dependent upon our senior management, as well as our senior scientists and other members of our management team. The loss of services of any of these individuals could delay or prevent the successful development of our product pipeline, initiation or completion of our preclinical studies and clinical trials or the commercialization of our vaccine candidates. Although we have executed employment agreements or offer letters with each member of our senior management team, these agreements are terminable at will with or without notice and, therefore, we may not be able to retain their services as expected. We do not currently maintain “key person” life insurance on the lives of our executives or any of our employees. This lack of insurance means that we may not have adequate compensation for the loss of the services of these individuals.

We will need to expand and effectively manage our managerial, operational, financial and other resources in order to successfully pursue our clinical development and commercialization efforts. We may not be successful in maintaining our unique company culture and continuing to attract or retain qualified management and scientific and clinical personnel in the future due to the intense competition for qualified personnel among biopharmaceutical, biotechnology and other businesses. Our industry has experienced a high rate of turnover of management personnel in recent years. If we are not able to attract, integrate, retain and motivate necessary personnel to accomplish our business objectives, we may experience constraints that will

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significantly impede the achievement of our development objectives, our ability to raise additional capital and our ability to implement our business strategy.

We may encounter difficulties in managing our growth and expanding our operations successfully.

As of March 31, 2022, we had 31 full-time employees, including 20 employees engaged in research and development. As we continue development and pursue the potential commercialization of HIL-214 and any future vaccine candidates, as well as transition to functioning as a public company, we will need to expand our financial, development, regulatory, manufacturing, marketing and sales capabilities or contract with third parties to provide these capabilities for us. As our operations expand, we expect that we will need to manage additional relationships with various strategic partners, suppliers and other third parties. In addition, we may need to expand our facilities, including laboratory operations, and may be unable to do so on commercially reasonable terms, or at all. Our future financial performance and our ability to develop and commercialize HIL-214 and any future vaccine candidates and to compete effectively will depend, in part, on our ability to manage any future growth effectively.

The terms of our Loan Agreement place restrictions on our operating and financial flexibility.

As of the inception of the Loan Agreement on April 18, 2022, we borrowed $5.0 million and have the right to borrow an additional $70.0 million in the aggregate (collectively, Term Loans) subject to the achievement of certain specified financing and clinical development milestones (as described in the section titled “Management’s discussion and analysis of financial condition and results of operations—Liquidity and capital resources—Term Loan Facility”) and no event of default having occurred and be continuing. All obligations under the Term Loans are secured by a first priority lien on substantially all of our assets, including intellectual property and certain other assets. As a result, if we default on any of our obligations under the Loan Agreement, the lenders could foreclose on their security interest and liquidate some or all of the collateral, which would harm our business, financial condition and results of operations and could require us to reduce or cease operations.

In order to service this indebtedness and any additional indebtedness we may incur in the future, we need to generate cash from our operating activities. Our ability to generate cash is subject, in part, to our ability to successfully execute our business strategy, as well as general economic, financial, competitive, regulatory and other factors beyond our control. Our business may not be able to generate sufficient cash flow from operations, and future borrowings or other financings may not be available to us in an amount sufficient to enable us to service our indebtedness and fund our other liquidity needs. To the extent we are required to use cash from operations or the proceeds of any future financing to service our indebtedness instead of funding working capital, capital expenditures or other general corporate purposes, we will be less able to plan for, or react to, changes in our business, industry and in the economy generally. This could place us at a competitive disadvantage compared to our competitors that have less indebtedness.

The Loan Agreement contains certain customary affirmative and negative covenants and events of default. The affirmative covenants include, among others, covenants requiring us to maintain our legal existence and governmental approvals, deliver certain financial reports, maintain insurance coverage and satisfy certain requirements regarding our operating accounts. The negative covenants include, among others, limitations on our ability to incur additional indebtedness and liens, merge with other companies or consummate certain changes of control, acquire other companies or businesses, make certain investments, pay dividends, transfer or dispose of assets, amend certain material agreements, including the Takeda License, or enter into various specified transactions.

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While we believe we are currently in compliance with the covenants contained in the Loan Agreement, we may breach these covenants in the future. Our ability to comply with these covenants may be affected by events and factors beyond our control. In the event that we breach one or more covenants, the lenders may choose to declare an event of default and require that we immediately repay all amounts outstanding under the Loan Agreement, terminate any commitment to extend further credit and foreclose on the collateral. The occurrence of any of these events could have a material adverse effect on our business, financial condition and results of operations.

We are subject to various U.S. federal, state and foreign healthcare laws and regulations, which could increase compliance costs, and our failure to comply with these laws and regulations could harm our results of operations and financial condition.

Our business operations and current and future arrangements with investigators, healthcare professionals, consultants, third-party payors, patient organizations and customers expose us to broadly applicable foreign, federal and state fraud and abuse and other healthcare laws and regulations. These laws may constrain the business or financial arrangements and relationships through which we conduct our operations, including how we research, market, sell and distribute any products for which we obtain marketing approval. Such laws include:

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Efforts to ensure that our current and future business arrangements with third parties will comply with applicable healthcare and privacy laws and regulations will involve ongoing substantial costs. It is possible that governmental authorities will conclude that our business practices, including consulting agreements with certain physicians who are paid in the form of stock or stock options as compensation for services provided to us, may not comply with current or future statutes, regulations or case law involving applicable fraud and abuse or other healthcare laws and regulations. If our operations are found to be in violation of any of these laws or any other governmental regulations that may apply to us, we may be subject to significant penalties, including civil, criminal and administrative penalties, damages, fines, disgorgement, imprisonment, exclusion from participation in government-funded healthcare programs, such as Medicare and Medicaid, integrity oversight and reporting obligations, contractual damages, reputational harm, diminished profits and future earnings and the curtailment or restructuring of our operations. Defending against any such actions can be costly and time-consuming and may require significant financial and personnel resources. Therefore, even if we are successful in defending against any such actions that may be brought against us, our business may be impaired. Further, if any of the physicians or other healthcare providers or entities with whom we expect to do business are found not to be in compliance with applicable laws or regulations, they may be subject to significant criminal, civil or administrative sanctions, including exclusions from government-funded healthcare programs.

Recently enacted legislation, future legislation and healthcare reform measures may increase the difficulty and cost for us to obtain marketing approval for and commercialize HIL-214 and any future vaccine candidates and may affect the prices we may set.

In the United States and some foreign jurisdictions, there have been, and we expect there will continue to be, a number of legislative and regulatory changes to the healthcare system, including cost-containment measures that may reduce or limit coverage and reimbursement for newly approved drugs and affect our ability to profitably sell HIL-214 and any future vaccine candidates for which we obtain marketing approval. In particular, there have been and continue to be a number of initiatives at the U.S. federal and state levels that seek to reduce healthcare costs and improve the quality of healthcare.

For example, in March 2010, the ACA was enacted in the United States. The ACA established an annual, nondeductible fee on any entity that manufactures or imports specified branded prescription drugs and biologic agents; extended manufacturers’ Medicaid rebate liability to covered drugs dispensed to individuals who are enrolled in Medicaid managed care organizations; expanded eligibility criteria for Medicaid programs; expanded the entities eligible for discounts under the Public Health program; increased the statutory minimum

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rebates a manufacturer must pay under the Medicaid Drug Rebate Program; created a new Medicare Part D coverage gap discount program; established a new Patient- Centered Outcomes Research Institute to oversee, identify priorities in and conduct comparative clinical effectiveness research, along with funding for such research; and established a Center for Medicare Innovation at CMS to test innovative payment and service delivery models to lower Medicare and Medicaid spending.

Since its enactment, there have been executive, judicial and Congressional challenges to certain aspects of the ACA, and on June 17, 2021, the U.S. Supreme Court dismissed the most recent judicial challenge to the ACA brought by several states without specifically ruling on the constitutionality of the ACA. Prior to the Supreme Court’s decision, President Biden had issued an executive order to initiate a special enrollment period from February 15, 2021 through August 15, 2021 for purposes of obtaining health insurance coverage through the ACA marketplace. The executive order also instructed certain governmental agencies to review and reconsider their existing policies and rules that limit access to healthcare, including among others, reexamining Medicaid demonstration projects and waiver programs that include work requirements, and policies that create unnecessary barriers to obtaining access to health insurance coverage through Medicaid or the ACA. It is unclear how the healthcare reform measures of the Biden administration will impact our business.

In addition, other legislative changes have been proposed and adopted since the ACA was enacted. On August 2, 2011, the Budget Control Act of 2011 was signed into law, which, among other things, resulted in reductions to Medicare payments to providers of 2% per fiscal year, which went into effect on April 1, 2013 and, due to subsequent legislative amendments to the statute, will remain in effect through 2030, with the exception of a temporary suspension from May 1, 2020 through March 31, 2022 and a 1% reduction from April 1, 2022 through June 30, 2022, unless additional Congressional action is taken. In addition, on January 2, 2013, the American Taxpayer Relief Act of 2012 was signed into law, which, among other things, further reduced Medicare payments to several providers, including hospitals, and increased the statute of limitations period for the government to recover overpayments to providers from three to five years.

Further, there has been heightened governmental scrutiny in the United States of pharmaceutical pricing practices in light of the rising cost of prescription drugs. Such scrutiny has resulted in several recent congressional inquiries and proposed and enacted federal and state legislation designed to, among other things, bring more transparency to product pricing, review the relationship between pricing and manufacturer patient assistance programs, and reform government program reimbursement methodologies for products. At the federal level, the former Trump administration used several means to propose or implement drug pricing reform, including through federal budget proposals, executive orders and policy initiatives. It is unclear whether the Biden administration will work to reverse these measures or pursue similar policy initiatives. Further, it is possible that additional governmental action is taken in response to the COVID-19 pandemic.

At the state level, legislatures have increasingly passed legislation and implemented regulations designed to control pharmaceutical and biological product pricing, including price or reimbursement constraints, discounts, restrictions on certain product access and marketing cost disclosure and transparency measures, and, in some cases, designed to encourage importation from other countries and bulk purchasing. Legally mandated price controls on payment amounts by third-party payors or other restrictions could harm our business, results of operations, financial condition and prospects. In addition, regional healthcare authorities and individual hospitals are increasingly using bidding procedures to determine what pharmaceutical products and which suppliers will be included in their prescription drug and other healthcare programs. This could reduce the ultimate demand for HIL-214 and any future vaccine candidates, if approved, or put pressure on our product pricing, which could negatively affect our business, results of operations, financial condition and prospects.

We expect that the ACA, these new laws and other healthcare reform measures that may be adopted in the future may result in additional reductions in Medicare and other healthcare funding, more rigorous coverage

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criteria, new payment methodologies and additional downward pressure on the price that we receive for any approved product. Any reduction in reimbursement from Medicare or other government programs may result in a similar reduction in payments from private payors. The implementation of cost containment measures or other healthcare reforms may prevent us from being able to generate revenue, attain profitability or commercialize HIL-214 and any future vaccine candidates, if approved.

If product liability lawsuits are brought against us, we may incur substantial liabilities and may be required to limit commercialization of our products.

We face an inherent risk of product liability as a result of the planned clinical trials of HIL-214 and any future vaccine candidates and will face an even greater risk if we commercialize such vaccine candidates. For example, we may be sued if HIL-214 or any future vaccine candidates allegedly cause injury or are found to be otherwise unsuitable during product testing, manufacturing, marketing or sale. Any such product liability claims may include allegations of defects in manufacturing, defects in design, a failure to warn of dangers inherent in the vaccine candidate, negligence, strict liability and a breach of warranties. Claims may be brought against us by clinical trial participants, vaccine recipients or others using, administering or selling products that may be approved in the future. Claims could also be asserted under state consumer protection acts.

If we cannot successfully defend ourselves against product liability claims, we may incur substantial liabilities or be required to limit or cease the commercialization of our products. Even a successful defense would require significant financial and management resources. Regardless of the merits or eventual outcome, liability claims may result in:

We may need to increase our insurance coverage as we expand our clinical trials or if we commence commercialization of HIL-214 or any future vaccine candidates. Insurance coverage is increasingly expensive. Our inability to obtain and retain sufficient product liability insurance at an acceptable cost to protect against potential product liability claims could prevent or inhibit the commercialization of HIL-214 or any future vaccine candidates. Although we will maintain such insurance, any claim that may be brought against us could result in a court judgment or settlement in an amount that is not covered, in whole or in part, by our insurance or that is in excess of the limits of our insurance coverage. Our insurance policies will also have various exclusions, and we may be subject to a product liability claim for which we have no coverage. We may have to pay any amounts awarded by a court or negotiated in a settlement that exceed our coverage limitations or that are not covered by our insurance, and we may not have, or be able to obtain, sufficient capital to pay such amounts.

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Our insurance policies are expensive and only protect us from some business risks, which will leave us exposed to significant uninsured liabilities.

We do not carry insurance for all categories of risk that our business may encounter. Some of the policies we currently maintain include property, general liability, workers’ compensation, clinical trials, and directors’ and officers’, employment practices and fiduciary liability insurance. We do not know, however, if we will be able to maintain insurance with adequate levels of coverage. Any significant uninsured liability may require us to pay substantial amounts, which would adversely affect our financial position and results of operations.

We and any of our potential future collaborators will be required to report to regulatory authorities if any of our approved products cause or contribute to adverse medical events, and any failure to do so would result in sanctions that would materially harm our business.

If we or any of our potential future collaborators are successful in commercializing our products, the FDA and foreign regulatory authorities would require that we and such collaborators report certain information about adverse medical events if those products may have caused or contributed to those adverse events. The timing of our obligation to report would be triggered by the date we become aware of the adverse event as well as the nature of the event. We and any of our potential future collaborators or CROs may fail to report adverse events within the prescribed timeframe. If we or any of our current or potential future collaborators or CROs fail to comply with such reporting obligations, the FDA or a foreign regulatory authority could take action, including criminal prosecution, the imposition of civil monetary penalties, seizure of our products or delay in approval or clearance of future products.

We and our service providers may be subject to a variety of privacy and data security laws and contractual obligations, which could increase compliance costs, and our actual or perceived failure to comply with such laws and obligations could subject us to potentially significant liability, fines or penalties and otherwise harm our business.

We and our service providers maintain and will maintain a large quantity of sensitive information, including confidential business and patient health information, in connection with our preclinical studies and planned clinical trials, and are subject to laws and regulations governing the privacy and security of such information. The global data protection landscape is rapidly evolving, and we and our service providers may be affected by or subject to new, amended or existing laws and regulations in the future, including as our operations continue to expand or if we operate in foreign jurisdictions. These laws and regulations may be subject to differing interpretations, which adds to the complexity of processing personal data. Guidance on implementation and compliance practices are often updated or otherwise revised. This may create uncertainty in our business, affect our ability to operate in certain jurisdictions or to collect, store, transfer, use, share and otherwise process personal information, necessitate the acceptance of more onerous obligations in our contracts, result in liability or impose additional costs on us. The cost of compliance with these laws, regulations and standards is high and is likely to increase in the future. Any failure or perceived failure by us to comply with federal, state or foreign laws or regulation, our internal policies and procedures or our contracts governing our processing of personal information could result in negative publicity, government investigations and enforcement actions, claims by third parties and damage to our reputation, any of which could have a material adverse effect on our operations, financial performance and business.

As our operations and business grow, we may become subject to or affected by new or additional data protection laws and regulations and face increased scrutiny or attention from regulatory authorities. In the United States, numerous federal and state laws and regulations, including health information privacy laws, data breach notification laws and consumer protection laws (e.g., Section 5 of the Federal Trade Commission Act), that govern

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the collection, use, storage, transfer, disclosure, protection and other processing of health-related and other personal information could apply to our operations or the operations of our collaborators and third-party providers. In addition, we may obtain health information from third parties (including research institutions from which we obtain clinical trial data) that are subject to privacy and security requirements under HIPAA. Depending on the facts and circumstances, we could be subject to significant penalties if we violate HIPAA.

In addition, certain state laws govern the privacy and security of health-related and other personal information in certain circumstances. These laws are evolving rapidly and may differ from each other in significant ways and may not have the same effect, thus complicating compliance efforts. By way of example, the California Consumer Privacy Act (CCPA), which went into effect on January 1, 2020, gives California residents individual privacy rights to access and delete their personal information, opt out of certain personal information sharing, and receive detailed information about how their personal information is used. The CCPA provides for civil penalties for violations, as well as a private right of action for data breaches that is expected to increase data breach litigation. The CCPA may increase our compliance costs and potential liability and many similar laws have been proposed at the federal level and in other states. Further, the California Privacy Rights Act (CPRA) recently passed in California. The CPRA will impose additional data protection obligations on covered businesses, including additional consumer rights processes, limitations on data uses, new audit requirements for higher risk data, and opt outs for certain uses of sensitive data. It will also create a new California data protection agency authorized to issue substantive regulations and could result in increased privacy and information security enforcement. The majority of the provisions of the CPRA will go into effect on January 1, 2023, and additional compliance investment and potential business process changes may be required. Other states are exploring their own laws, which may or may not be similar to the CCPA or the CPRA. In the event that we are subject to or affected by HIPAA, the CCPA, the CPRA or other domestic privacy and data protection laws, any liability from failure to comply with the requirements of these laws could adversely affect our financial condition.

There also are a wide variety of privacy laws in other countries that may impact our operations, now or in the future. For example, in Europe, the General Data Protection Regulation (GDPR) imposes stringent requirements regarding the collection, use, disclosure, storage, transfer or other processing of personal data of individuals within the European Economic Area (EEA). Companies that must comply with the GDPR face increased compliance obligations and risk, including more robust regulatory enforcement of data protection requirements and potential fines for noncompliance of up to €20 million or 4% of the annual global revenue of the noncompliant company, whichever is greater. The GDPR also confers a private right of action in some circumstances on data subjects and consumer associations to lodge complaints with supervisory authorities, seek judicial remedies and obtain compensation for damages resulting from violations of the GDPR. Among other things, the GDPR requires the establishment of a lawful basis for the processing of data, imposes requirements relating to the consent of the individuals to whom the personal data relates, including detailed notices for clinical trial subjects and investigators, as well as requirements regarding the security of personal data and notification of data processing obligations to the competent national data processing authorities. In addition, the GDPR increases the scrutiny of transfers of personal data from the EEA to the United States and other jurisdictions that the European Commission does not recognize as having “adequate” data protection laws. Recent legal developments in Europe have created complexity and uncertainty regarding transfers of personal data from the EEA to the United States. For example, on July 16, 2020, the Court of Justice of the European Union (CJEU) invalidated the EU-US Privacy Shield Framework (Privacy Shield) under which personal data could be transferred from the EEA to United States entities that had self-certified under the Privacy Shield scheme. While the CJEU upheld the adequacy of the standard contractual clauses (a standard form of contract approved by the European Commission as an adequate personal data transfer mechanism, and potential alternative to the Privacy Shield), it made clear that reliance on the standard contractual clauses alone may not

necessarily be sufficient in all circumstances. Use of the standard contractual clauses must now be assessed on

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a case-by-case basis taking into account the legal regime applicable in the destination country, in particular applicable surveillance laws and rights of individuals, and additional measures and/or contractual provisions may need to be put in place, however, the nature of these additional measures is currently uncertain. The European Commission issued revised standard contractual clauses on June 4, 2021 to account for the decision of the CJEU and recommendations made by the European Data Protection Board. The revised standard contractual clauses must be used for relevant new data transfers beginning on September 27, 2021 and existing standard contractual clauses arrangements must be migrated to the revised clauses by December 27, 2022. The new standard contractual clauses apply only to the transfer of personal data outside of the EEA and not the United Kingdom; the United Kingdom’s Information Commissioner’s Office launched a public consultation on its draft revised data transfers mechanisms in August 2021 and the United Kingdom standard contractual clauses came into force in March 2022, with a two-year grace period. There is some uncertainty around whether the revised clauses can be used for all types of data transfers, particularly whether they can be relied on for data transfers to non-EEA entities subject to the GDPR. As supervisory authorities issue further guidance on personal data export mechanisms, including circumstances where the standard contractual clauses cannot be used, and/or start taking enforcement action, we could suffer additional costs, complaints and/or regulatory investigations or fines, and/or if we are otherwise unable to transfer personal data between and among countries and regions in which we operate, it could affect the manner in which we provide our services, the geographical location or segregation of our relevant systems and operations, and could adversely affect our financial results.

Further, following the withdrawal of the United Kingdom from the European Union and the EEA and the end of the transition period, from January 1, 2021, we have to comply with the GDPR and separately the GDPR as implemented in the United Kingdom, which, together with the amended UK Data Protection Act 2018, retains the GDPR in UK national law. The UK GDPR mirrors the fines under the GDPR and has the ability to fine up to the greater of €20 million/£17 million or 4% of global turnover. The relationship between the United Kingdom and the European Union and the EEA in relation to certain aspects of data protection law remains unclear, and it is unclear how United Kingdom data protection laws and regulations will develop in the medium to longer term. The European Commission has adopted an adequacy decision in favor of the United Kingdom, enabling data transfers from EU member states to the United Kingdom without additional safeguards. However, the UK adequacy decision will automatically expire in June 2025 unless the European Commission re-assesses and renews or extends that decision.

In many jurisdictions, enforcement actions and consequences for noncompliance are rising. In the United States, these include enforcement actions in response to rules and regulations promulgated under the authority of federal agencies and state attorneys general and legislatures and consumer protection agencies. In addition, privacy advocates and industry groups have regularly proposed, and may propose in the future, self-regulatory standards that may legally or contractually apply to us. If we fail to follow these security standards, even if no personal information is compromised, we may incur significant fines or experience a significant increase in costs. Many state legislatures have adopted legislation that regulates how businesses operate online, including measures relating to privacy, data security and data breaches. Laws in all U.S. states require businesses to provide notice to customers whose personally identifiable information has been disclosed as a result of a data breach. The laws are not consistent, and compliance in the event of a widespread data breach is costly.

Compliance with U.S. and international data protection laws and regulations could require us to take on more onerous obligations in our contracts, restrict our ability to collect, store, use, transfer, disclose and otherwise process data, update our data privacy and security policies and procedures, or in some cases, impact our ability to operate in certain jurisdictions. Failure by us or our collaborators and our service providers to comply with U.S. and international data protection laws and regulations could result in government enforcement actions (which could include civil or criminal penalties), private litigation and/or

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adverse publicity and could negatively affect our operating results and business. Moreover, clinical trial subjects about whom we or our potential collaborators obtain information, as well as the providers who share this information with us, may contractually limit our ability to use and disclose such information. Claims that we have violated individuals’ privacy rights, failed to comply with data protection laws, or breached our contractual obligations, even if we are not found liable, could be expensive and time consuming to defend, could result in adverse publicity and adversely affect our business, financial condition, results of operations and prospects. Should any of these events occur, they could have a material adverse effect on our business, financial condition, results of operations, and prospects.

Our internal information technology systems, or those of any of our service providers, may fail or suffer security breaches, loss or leakage of data and other disruptions, which could result in a material disruption of our product development programs, compromise sensitive information related to our business or prevent us from accessing critical information, potentially exposing us to liability or otherwise adversely affecting our business.

We are increasingly dependent upon information technology systems, infrastructure and data to operate our business. In the ordinary course of business, we collect, store and transmit confidential information (including but not limited to intellectual property, proprietary business information and personal information). It is critical that we do so in a secure manner to maintain the confidentiality and integrity of such confidential information.

Attacks upon information technology systems are increasing in their frequency, levels of persistence, sophistication and intensity, and are being conducted by sophisticated and organized groups and individuals with a wide range of motives and expertise. These attacks can present meaningful risks to our operations, data and commercial information. As a result of the COVID-19 pandemic, we may also face increased cybersecurity risks due to our reliance on internet technology and the number of our employees who are working remotely, which may create additional opportunities for cybercriminals to exploit vulnerabilities. Furthermore, because the techniques used to obtain unauthorized access to, or to sabotage, systems change frequently and often are not recognized until launched against a target, we may be unable to anticipate these techniques or implement adequate preventative measures. We may also experience security breaches that may remain undetected for an extended period. Even if identified, we may be unable to adequately investigate or remediate incidents or breaches due to attackers increasingly using tools and techniques that are designed to circumvent controls, to avoid detection, and to remove or obfuscate forensic evidence. Any security breach or other incident, whether actual or perceived, were to occur, it could impact our reputation and/or operations, cause us to incur significant costs, including legal expenses, harm customer confidence, hurt our expansion into new markets, cause us to incur remediation costs, or cause us to lose existing customers. For example, the loss of clinical trial data from clinical trials could result in delays in our regulatory approval efforts and significantly increase our costs to recover or reproduce the data. We also rely on third parties to manufacture HIL-214, and similar events relating to their computer systems could also have a material adverse effect on our business. To the extent that any actual or perceived disruption or security breach affects our systems (or those of our third-party collaborators, service providers, contractors or consultants) or were to result in a loss of or accidental, unlawful or unauthorized access to, use of, release of, or other processing of personally identifiable information, or damage to, our data or applications, or inappropriate disclosure of confidential or proprietary information, we could incur liability, the further development and commercialization of HIL-214 or any future vaccine candidate could be delayed, and we could be subject to significant fines, penalties or liabilities for any noncompliance to certain privacy and security laws.

Further, despite the implementation of security measures, our internal technology systems (including infrastructure) and those of our current and any future CROs and other contractors, consultants and

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collaborators are vulnerable to breakdown or other damage or interruption from service interruptions, system malfunction, computer viruses, cybersecurity threats (such as ransomware attacks, denial-of-service attacks, cyber-attacks or cyber-intrusions over the Internet, hacking, phishing and other social engineering attacks), unauthorized access or use, natural disasters, terrorism, war and telecommunication and electrical failures. Such information technology systems are additionally vulnerable to security incidents from inadvertent or intentional actions by our employees, contractors, consultants or other third parties. We and certain of our service providers are from time to time subject to cyberattacks and security incidents. While we do not believe that we have experienced any significant system failure, accident or security breach to date, if such an event were to occur and cause interruptions in our operations or result in the unauthorized disclosure of or access to personally identifiable information or individually identifiable health information, it could result in a material disruption of our development programs and our business operations, whether due to a loss of our trade secrets or other similar disruptions. We do not currently hold cybersecurity insurance, and the costs related to significant security breaches or disruptions could be material and cause us to incur significant expenses.

We have also outsourced elements of our information technology infrastructure, and as a result a number of third-party vendors may or could have access to our confidential information. If our third-party vendors fail to protect their information technology systems and our confidential and proprietary information, we may be vulnerable to disruptions in service and unauthorized access to our confidential or proprietary information and we could incur liability and reputational damage. If the information technology systems of our third-party vendors and other contractors and consultants become subject to disruptions or security breaches, we may have insufficient recourse against such third parties and we may have to expend significant resources to mitigate the impact of such an event, and to develop and implement protections to prevent future events of this nature from occurring. Some of the federal, state and foreign government requirements include obligations of companies to notify individuals of security breaches involving particular categories of personally identifiable information, which could result from breaches experienced by us or by our vendors, contractors, or organizations with which we have formed strategic relationships.

Our business is subject to risks arising from the COVID-19 pandemic and other epidemic diseases.

The COVID-19 worldwide pandemic has presented substantial public health and economic challenges and is affecting our employees, clinical trial subjects, physicians and other healthcare providers, communities and business operations, as well as the U.S. and global economies and financial markets. International and U.S. governmental authorities in impacted regions have taken, and are continuing to take, actions in an effort to slow the spread of COVID-19 and variants of the virus, including issuing varying forms of “stay-at-home” orders, and restricting business functions outside of one’s home. In response, our administrative employees have worked remotely and we have limited the number of staff in our research and development laboratories. To date we have not experienced material disruptions in our business operations. However, while it is not possible at this time to estimate the impact that COVID-19 could have on our business in the future, particularly as we advance HIL-214 through clinical development, the continued spread of COVID-19 and the measures taken by the governmental authorities, and any future epidemic disease outbreaks, could disrupt the supply chain and the manufacture or shipment of drug substances and finished drug products for HIL-214 for use in our clinical trials and research and preclinical studies and, delay, limit or prevent our employees and CROs from continuing research and development activities, impede our clinical trial initiation and recruitment and the ability of subjects to continue in clinical trials, result in a decrease in the incidence of norovirus infection among trial subjects delaying any evaluation of the endpoints in our clinical trials of HIL-214 and the ultimate completion of such trials, including due to measures taken that may limit social interaction or prevent reopening of high-transmission settings, impede testing, monitoring, data collection and analysis and other related activities, any of which could delay our preclinical studies and clinical trials and increase our development costs, and have a

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material adverse effect on our business, financial condition and results of operations. The COVID-19 pandemic and any future epidemic disease outbreak could also potentially further affect the business of the FDA or other regulatory authorities, which could result in delays in meetings related to our planned clinical trials. The COVID-19 pandemic and mitigation measures have had and may continue to have, and any future epidemic disease outbreak may have, an adverse impact on global economic conditions which could have an adverse effect on our business and financial condition, including impairing our ability to raise capital when needed. The extent to which the COVID-19 pandemic impacts our results will depend on future developments that are highly uncertain and cannot be predicted, including new information that may emerge concerning the severity of the virus, including the identification of new variants, and the actions to contain its impact.

Our business could be affected by litigation, government investigations and enforcement actions.

We currently operate in a number of jurisdictions in a highly regulated industry and we could be subject to litigation, government investigation and enforcement actions on a variety of matters in the United States. or foreign jurisdictions, including, without limitation, intellectual property, regulatory, product liability, environmental, whistleblower, false claims, privacy, anti-kickback, anti-bribery, securities, commercial, employment and other claims and legal proceedings which may arise from conducting our business. Any determination that our operations or activities are not in compliance with existing laws or regulations could result in the imposition of fines, civil and criminal penalties, equitable remedies, including disgorgement, injunctive relief and/or other sanctions against us, and remediation of any such findings could have an adverse effect on our business operations.

Legal proceedings, government investigations and enforcement actions can be expensive and time-consuming. An adverse outcome resulting from any such proceeding, investigations or enforcement actions could result in significant damages awards, fines, penalties, exclusion from the federal healthcare programs, healthcare debarment, injunctive relief, product recalls, reputational damage and modifications of our business practices, which could have a material adverse effect on our business and results of operations.

Our employees and independent contractors, including principal investigators, CROs, consultants and vendors, may engage in misconduct or other improper activities, including noncompliance with regulatory standards and requirements.

We are exposed to the risk that our employees and independent contractors, including principal investigators, CROs, consultants and vendors, may engage in misconduct or other illegal activity. Misconduct by these parties could include intentional, reckless and/or negligent conduct or disclosure of unauthorized activities to us that violate: (i) the laws and regulations of the FDA and other similar regulatory requirements, including those laws that require the reporting of true, complete and accurate information to such authorities, (ii) manufacturing standards, including cGMP requirements, (iii) federal and state data privacy, security, fraud and abuse and other healthcare laws and regulations in the United States and abroad or (iv) laws that require the true, complete and accurate reporting of financial information or data. Activities subject to these laws also involve the improper use or misrepresentation of information obtained in the course of clinical trials, the creation of fraudulent data in our preclinical studies or clinical trials or illegal misappropriation of drug product, which could result in regulatory sanctions and cause serious harm to our reputation. It is not always possible to identify and deter misconduct by employees and other third parties, and the precautions we take to detect and prevent this activity may not be effective in controlling unknown or unmanaged risks or losses or in protecting us from governmental investigations or other actions or lawsuits stemming from a failure to be in compliance with such laws or regulations. In addition, we are subject to the risk that a person or government could allege such fraud or other misconduct, even if none occurred. If any such actions are instituted against us, and we are

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not successful in defending ourselves or asserting our rights, those actions could have a significant impact on our business and financial results, including, without limitation, the imposition of significant civil, criminal and administrative penalties, damages, monetary fines, disgorgements, possible exclusion from participation in Medicare, Medicaid and other federal healthcare programs, imprisonment, contractual damages, reputational harm, diminished profits and future earnings, additional reporting requirements and oversight if we become subject to a corporate integrity agreement or similar agreement to resolve allegations of non-compliance with these laws and curtailment of our operations, any of which could adversely affect our ability to operate our business and our results of operations.

We may engage in strategic transactions that could impact our liquidity, increase our expenses and present significant distractions to our management.

From time to time, we may consider strategic transactions, such as acquisitions of companies, asset purchases and out-licensing or in-licensing of intellectual property, products or technologies. Additional potential transactions that we may consider in the future include a variety of business arrangements, including spin-offs, strategic partnerships, joint ventures, restructurings, divestitures, business combinations and investments. Any future transactions could increase our near and long-term expenditures, result in potentially dilutive issuances of our equity securities, including our common stock, or the incurrence of debt, contingent liabilities, amortization expenses or acquired in-process research and development expenses, any of which could affect our financial condition, liquidity and results of operations. Future acquisitions may also require us to obtain additional financing, which may not be available on favorable terms or at all. These transactions may never be successful and may require significant time and attention of our management. In addition, the integration of any business that we may acquire in the future may disrupt our existing business and may be a complex, risky and costly endeavor for which we may never realize the full benefits. Accordingly, although there can be no assurance that we will undertake or successfully complete any additional transactions of the nature described above, any additional transactions that we do complete could have a material adverse effect on our business, results of operations, financial condition and prospects.

Risks related to our intellectual property

If we are unable to obtain, maintain and enforce patent protection for HIL-214 or any future vaccine candidates, or if the scope of the patent protection obtained is not sufficiently broad, our competitors or other third parties could develop and commercialize products similar or identical to ours, and our ability to successfully commercialize HIL-214 or any future vaccine candidates may be adversely affected.

Our success depends in large part on our ability to obtain, maintain and enforce patent protection in the United States and other countries with respect to our vaccine candidates and other proprietary technologies we may develop. We seek to protect our proprietary position, in part, by exclusively licensing patents and patent applications in the United States and abroad relating to our vaccine candidates, manufacturing processes, and methods of use. If we or our principal licensor, Takeda, are unable to obtain, maintain or enforce patent protection, our business, financial condition, results of operations and prospects could be materially harmed.

Changes in either the patent laws or their interpretation in the United States and other jurisdictions may diminish our or our licensors’ ability to protect our intellectual property, obtain, maintain and enforce our intellectual property rights and, more generally, could affect the value of our intellectual property or narrow the scope of our protection. We cannot predict whether the patent applications we currently or may in the future pursue or in-license will issue as patents in any particular jurisdiction or whether the claims of any issued patents will provide sufficient protection against competitors or other third parties.

The patent prosecution process is expensive, time-consuming, and complex, and we or our licensors may not be able to file, prosecute, maintain, enforce or license all necessary or desirable patent applications at a

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reasonable cost or in a timely manner. It is also possible that we will fail to identify patentable aspects of our research and development output in time to obtain patent protection. Although we enter into non-disclosure and confidentiality agreements with parties who have access to confidential or patentable aspects of our research and development output, such as our employees, third party collaborators, CROs, contract manufacturers, consultants, advisors and other third parties, any of these parties may breach the agreements and disclose such output before a patent application is filed, thereby jeopardizing our or our licensors’ ability to seek patent protection. Consequently, we may not be able to prevent any third party from using any of our technology that is in the public domain to compete with our vaccine candidates and technologies. In addition, our ability to obtain and maintain valid and enforceable patents depends on whether the differences between our inventions and the prior art allow our inventions to be patentable in light of the prior art. Furthermore, publications of discoveries in the scientific literature often lag behind the actual discoveries, and patent applications in the United States and other jurisdictions are typically not published until 18 months after filing, or in some cases not at all. Therefore, we cannot be certain that our licensors were the first to invent the inventions claimed in any of our licensed patents or pending patent applications or patents or pending patent applications we may own in the future, or that we or our licensors were the first to make the inventions claimed in those patents or pending patent applications, or were the first to file for patent protection of such inventions. If a third party can establish that we or our licensors were not the first to make or the first to file for patent protection of such inventions, our owned or licensed patents and patent applications may not issue as patents and even if issued, may be challenged and invalidated or rendered unenforceable.

The patent position of biotechnology and pharmaceutical companies generally is highly uncertain, involves complex legal and factual questions and has been the subject of much litigation in recent years. As a result, the issuance, scope, validity, enforceability and commercial value of our patent rights are highly uncertain. Our owned and in-licensed patent applications or patent applications we may own in the future may not result in patents being issued which protect our vaccine candidates or proprietary technologies we may develop or which effectively prevent others from commercializing competitive technologies and products. In fact, patent applications may not issue as patents at all.

Moreover, the claim coverage in a patent application can be significantly reduced before the corresponding patent is granted. Even if our in-licensed patent applications or patent applications we may own in the future issue as patents, they may not issue in a form that will provide us with any meaningful protection, prevent competitors or other third parties from competing with us or otherwise provide us with any competitive advantage. Any patents issuing from our in-licensed patent applications may be challenged, narrowed, circumvented or invalidated by third parties. Our competitors or other third parties may avail themselves of safe harbors under the Drug Price Competition and Patent Term Restoration Act of 1984 (Hatch-Waxman Amendments) to conduct research and clinical trials. Consequently, we do not know whether our vaccine development programs and other proprietary technology will be protectable or remain protected by valid and enforceable patents. Even if a patent is granted, our competitors or other third parties may be able to circumvent the patent by developing similar or alternative technologies or products in a non-infringing manner which could materially adversely affect our business, financial condition, results of operations and prospects. In addition, given the amount of time required for the development, testing and regulatory review of our vaccine candidates, patents protecting the vaccine candidates might expire before or shortly after such vaccine candidates are commercialized. As a result, our intellectual property may not provide us with sufficient rights to exclude others from commercializing products similar or identical to ours.

The issuance of a patent is not conclusive as to its inventorship, scope, validity, or enforceability and our patent rights may be challenged in the courts or patent offices in the United States and abroad. We may be subject to a third-party pre-issuance submission of prior art to the United States Patent and Trademark Office (USPTO)

challenging the validity of one or more claims of our in-licensed patents or patents we may own in the future.

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Such submissions may also be made prior to a patent’s issuance, precluding the granting of a patent based on one of our owned or licensed pending patent applications. A third party may also claim that our patent rights are invalid or unenforceable in a litigation. The outcome following legal assertions of invalidity and unenforceability is unpredictable. In addition, we may become involved in opposition, derivation, revocation, reexamination, post-grant and inter partes review or interference proceedings and other similar proceedings in foreign jurisdictions challenging the validity, priority or other features of patentability of our patent rights. An adverse determination in any such submission, proceeding or litigation could reduce the scope of, or invalidate or render unenforceable, our patent rights, allow third parties to commercialize our vaccine candidates and other proprietary technologies we may develop and compete directly with us, without payment to us, or result in our inability to commercialize products without infringing third-party patent rights. Such adverse determinations may also require us to cease using the related technology or to attempt to license rights from the prevailing party. Such proceedings also may result in substantial cost and require significant time from our scientists and management, even if the eventual outcome is favorable to us. Any of the foregoing, could have a material adverse effect on our business, financial condition, results of operations and prospects.

Moreover, some of our patent rights may in the future be co-owned with third parties. If we are unable to obtain an exclusive license to any such third-party co-owners’ interest in such patent rights, such co-owners may be able to license their rights to other third parties, including our competitors, and our competitors could market competing products and technology. In addition, we may need the cooperation of any such co-owners of such patent rights in order to enforce such patent rights against third parties, and such cooperation may not be provided to us. Any of the foregoing could have a material adverse effect on our competitive position, business, financial conditions, results of operations, and prospects.

We do not own any issued patents or patent applications and we completely depend on intellectual property licensed from third parties, including under the Takeda License, and our licensors may not always act in our best interest. If we fail to comply with our obligations under our intellectual property licenses, if the licenses are terminated or if disputes regarding these licenses arise, we could lose significant rights that are important to our business.

We do not own any issued patents or patent applications. Our vaccine candidate is completely dependent on patents, know-how and proprietary technology licensed from Takeda under the Takeda License. As a result, any termination of the Takeda License would result in the loss of significant rights and could harm our ability to commercialize HIL-214. The Takeda License imposes, and we expect that any future license agreements where we in-license intellectual property will impose on us, various development, regulatory and/or commercial diligence obligations, payment of milestones and/or royalties and other obligations. If we fail to comply with our obligations under the Takeda License or future license agreements, or we are subject to bankruptcy-related proceedings, the licensor may have the right to terminate the license, in which event we would not be able to develop or market the products covered by the license, including our HIL-214 vaccine candidate. In addition, we may need to obtain additional licenses from our existing licensors and others to advance our research or allow commercialization of vaccine candidates we may develop. It is possible that we may be unable to obtain any additional licenses at a reasonable cost or on reasonable terms, if at all. In either event, we may be required to expend significant time and resources to redesign our technology, vaccine candidates, or the methods for manufacturing them or to develop or license replacement technology, all of which may not be feasible on a technical or commercial basis. If we are unable to do so, we may be unable to develop or commercialize the affected technology or vaccine candidates. Even if we are able to obtain such additional licenses, they may be non-exclusive thereby giving our competitors and other third parties access to the same technology licensed to us.

If we or our licensors fail to adequately maintain, enforce and protect our licensed intellectual property, our ability to commercialize HIL-214 or any future vaccine candidates could suffer. We do not have complete control over the maintenance, enforcement, prosecution and litigation of our in-licensed patents and patent

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applications and may have limited control over future intellectual property that may be in-licensed. Therefore, such in-licensed patents and applications may not be prosecuted and enforced in a manner consistent with the best interests of our business. For example, we cannot be certain that activities such as the maintenance and prosecution by our licensors have been or will be conducted in compliance with applicable laws and regulations or will result in valid and enforceable patents and other intellectual property rights. It is possible that our licensors’ infringement proceedings or defense activities may be less vigorous than had we conducted them ourselves, or may not be conducted in accordance with our best interests. Furthermore, there are certain limitations to our right to enforce certain exclusively licensed patents, including, for example, the requirement that we obtain the licensor’s consent prior to settling lawsuits related to such patents. If our licensors fail to maintain such patents or patent applications, or lose rights to those patents or patent applications, the rights we have licensed may be reduced or eliminated, and our right to develop and commercialize any of our vaccine candidates that are the subject of such licensed rights and our right to exclude third parties from commercializing competing products could be adversely affected. Any of the foregoing could have a material adverse effect on our business, financial condition, results of operations and prospects.

In addition, the Takeda License is, and any future agreements under which we license intellectual property or technology from third parties may be, complex, and certain provisions in such agreements may be susceptible to multiple interpretations. The resolution of any contract interpretation disagreement that may arise could narrow what we believe to be the scope of our rights to the relevant patents, know-how and proprietary technology, or increase what we believe to be our financial or other obligations under the relevant agreement. In spite of our efforts, our current and future licensors might conclude that we have materially breached our obligations under our license agreements and might therefore terminate such license agreements, thereby removing or limiting our ability to develop and commercialize products and technology covered by these license agreements. Disputes that may arise between us and our licensors regarding intellectual property subject to a license agreement could include disputes regarding:

If disputes over intellectual property that we have licensed prevent or impair our ability to maintain our current licensing arrangements on reasonable terms, we may be unable to successfully develop and commercialize the affected technology or vaccine candidates. As a result, any termination of or disputes over our intellectual property licenses could result in the loss of our ability to develop and commercialize HIL-214 or any future vaccine candidates, or we could lose other significant rights, experience significant delays in the development and commercialization of our vaccine candidates, or incur liability for damages, any of which could have a material adverse effect on our business, financial condition, results of operations and prospects. In addition, we

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may seek to obtain additional licenses from our licensors and, in connection with obtaining such licenses, we may agree to amend our existing licenses in a manner that may be more favorable to the licensors, including by agreeing to terms that could enable third parties, including our competitors, to receive licenses to a portion of the intellectual property that is subject to our existing licenses and to compete with our vaccine candidates.

If our licenses are terminated, or if the underlying patents fail to provide the intended exclusivity, competitors or other third parties would have the freedom to seek regulatory approval of, and to market, products identical or competitive to ours and we may be required to cease our development and commercialization of certain of our vaccine candidates. Moreover, if disputes over intellectual property that we license prevent or impair our ability to maintain other licensing arrangements on commercially acceptable terms, we may be unable to successfully develop and commercialize the affected vaccine candidates.

In addition, certain of our agreements may not be assignable by us without the consent of the respective licensor, which may limit or delay our ability to consummate certain transactions, may impact the value of those transactions, or may limit our ability to pursue certain activities. For example, if we choose to sublicense or assign to any third parties our rights under the Takeda License with respect to any licensed product, we may be required to wait for a certain period or until the occurrence of certain funding or development milestones. For additional information on the Takeda License, see “Business—License agreement with Takeda.”

We may not be able to protect our intellectual property and proprietary rights throughout the world.

Filing, prosecuting and defending patents on HIL-214 and any future vaccine candidates in all countries throughout the world would be prohibitively expensive, and the laws of foreign countries may not protect our intellectual property rights to the same extent as the laws of the United States. Consequently, we may not be able to prevent third parties from practicing our or our licensors’ inventions in all countries outside the United States, or from selling or importing products made using our or our licensors’ intellectual property in and into the United States or other jurisdictions. Competitors may use our intellectual property in jurisdictions where we and our licensors have not pursued and obtained patent protection to develop their own products and, further, may export otherwise infringing products to territories where we have patent protection but enforcement is not as strong as that in the United States. These products may compete with our products, and our owned and in-licensed patents or other intellectual property rights may not be effective or sufficient to prevent them from competing. Many companies have encountered significant problems in protecting and defending intellectual property rights in foreign jurisdictions. The legal systems of certain countries, particularly certain developing countries, do not favor the enforcement of patents, trade secrets and other intellectual property protection, particularly those relating to biotechnology products, which could make it difficult for us to stop the infringement of our in-licensed patents, if pursued and obtained, or marketing of competing products in violation of our intellectual property and proprietary rights generally. In addition, some jurisdictions, such as Europe and China, may have a higher standard for patentability than in the United States, including, for example, the requirement of claims having literal support in the original patent filing and the limitation on using supporting data that is not in the original patent filing. Under those heightened patentability requirements, we may not be able to obtain sufficient patent protection in certain jurisdictions even though the same or similar patent protection can be secured in the United States and other jurisdictions.

Proceedings to enforce our intellectual property and proprietary rights in foreign jurisdictions could result in substantial costs and divert our efforts and attention from other aspects of our business, could put our in-licensed patents or patents we may own in the future at risk of being invalidated or interpreted narrowly, could put our in-licensed patent applications or patent applications we may own in the future at risk of not issuing and could provoke third parties to assert claims against us. We or our licensors may not prevail in any lawsuits that we or our

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licensors initiate, and the damages or other remedies awarded, if any, may not be commercially meaningful. Accordingly, our efforts to enforce our intellectual property and proprietary rights around the world may be inadequate to obtain a significant commercial advantage from the intellectual property that we develop.

Many countries have compulsory licensing laws under which a patent owner may be compelled to grant licenses to third parties. In addition, many countries limit the enforceability of patents against government agencies or government contractors. In these countries, the patent owner may have limited remedies, which could materially diminish the value of such patent. If we or any of our licensors are forced to grant a license to third parties with respect to any patents relevant to our business, our competitive position may be impaired, and our business, financial condition, results of operations and prospects may be adversely affected.

Obtaining and maintaining our patent protection depends on compliance with various procedural, document submission, fee payment, and other requirements imposed by government patent agencies, and our patent protection could be reduced or eliminated for non-compliance with these requirements.

The USPTO and various non-U.S. government agencies require compliance with several procedural, documentary, fee payment and other similar provisions during the patent application process. In some circumstances, we are dependent on our licensors to take the necessary action to comply with these requirements with respect to our licensed intellectual property. For example, periodic maintenance fees, renewal fees, annuity fees, and various other government fees on patents and applications will be due to be paid to the USPTO and various government patent agencies outside of the United States over the lifetime of our licensed patents and applications or any patents and applications we may own in the future. In certain circumstances, we rely on our licensors to pay these fees due to U.S. and non-U.S. patent agencies. The USPTO and various non-U.S. patent agencies require compliance with several procedural, documentary, fee payment and other similar provisions during the patent application process. We are also dependent on our licensors to take the necessary action to comply with these requirements with respect to our licensed intellectual property. In some cases, an inadvertent lapse can be cured by payment of a late fee or by other means in accordance with the applicable rules. There are situations, however, in which non-compliance can result in abandonment or lapse of the patent or patent application, resulting in a partial or complete loss of patent rights in the relevant jurisdiction. In such an event, potential competitors might be able to enter the market with similar or identical products or technology, which could have a material adverse effect on our business, financial condition, results of operations, and prospects.

The USPTO and various non-U.S. government agencies require compliance with certain foreign filing requirements during the patent application process. For example, in some countries, including the United States, China, India and some European countries, a foreign filing license is required before certain patent applications are filed. The foreign filing license requirements vary by country and depend on various factors, including where the inventive activity occurred, citizenship status of the inventors, the residency of the inventors and the invention owner, the place of business for the invention owner and the nature of the subject matter to be disclosed (e.g., items related to national security or national defense). In some cases, a foreign filing license may be obtained retroactively in accordance with the applicable rules. There are situations, however, in which non-compliance can result in abandonment of a pending patent application or can be grounds for revoking or invalidating an issued patent, resulting in the loss of patent rights in the relevant jurisdiction. In such an event, potential competitors might be able to enter the relevant markets with similar or identical products or technology, which could have a material adverse effect on our business, financial condition, results of operations, and prospects. We are also dependent on our licensors to take the necessary actions to comply with these requirements with respect to our licensed intellectual property.

The COVID-19 pandemic may impair our and our licensors’ ability to comply with these procedural, document submission, fee payment, and other requirements imposed by government patent agencies, which may materially and adversely affect our ability to obtain or maintain patent protection for our vaccine candidates.

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Changes in patent law could diminish the value of patents in general, thereby impairing our ability to protect our products.

Changes in either the patent laws or interpretation of the patent laws in the United States could increase the uncertainties and costs surrounding the prosecution of patent applications and the enforcement or defense of issued patents. Assuming that other requirements for patentability are met, prior to March 2013, in the United States, the first to invent the claimed invention was entitled to the patent, while outside the United States, the first to file a patent application was entitled to the patent. After March 2013, under the Leahy-Smith America Invents Act (the America Invents Act) enacted in September 2011, the United States transitioned to a first inventor to file system in which, assuming that other requirements for patentability are met, the first inventor to file a patent application will be entitled to the patent on an invention regardless of whether a third party was the first to invent the claimed invention. A third party that files a patent application in the USPTO after March 2013, but before us or our licensors could therefore be awarded a patent covering an invention of ours or our licensors even if we had made the invention before it was made by such third party. This will require us to be cognizant going forward of the time from invention to filing of a patent application. Since patent applications in the United States and most other countries are confidential for a period of time after filing or until issuance, we cannot be certain that we or our licensors were the first to either (i) file any patent application related to our vaccine candidates and other proprietary technologies we may develop or (ii) invent any of the inventions claimed in our patents or patent applications.

The America Invents Act also includes a number of significant changes that affect the way patent applications will be prosecuted and also may affect patent litigation. These include allowing third party submission of prior art to the USPTO during patent prosecution and additional procedures to attack the validity of a patent by USPTO administered post-grant proceedings, including post-grant review, inter partes review and derivation proceedings. Because of a lower evidentiary standard in USPTO proceedings compared to the evidentiary standard in United States federal courts necessary to invalidate a patent claim, a third party could potentially provide evidence in a USPTO proceeding sufficient for the USPTO to hold a claim invalid even though the same evidence would be insufficient to invalidate the claim if first presented in a district court action.

Accordingly, a third party may attempt to use the USPTO procedures to invalidate our patent claims that would not have been invalidated if first challenged by the third party as a defendant in a district court action. Therefore, the America Invents Act and its implementation could increase the uncertainties and costs surrounding the prosecution of our in-licensed patent applications or patent applications we may own in the future and the enforcement or defense of patents issuing from those patent applications, all of which could have a material adverse effect on our business, financial condition, results of operations and prospects.

In addition, the patent positions of companies in the development and commercialization of biologics and pharmaceuticals are particularly uncertain. Recent U.S. Supreme Court rulings have narrowed the scope of patent protection available in certain circumstances and weakened the rights of patent owners in certain situations. We cannot predict how decisions by the courts, the U.S. Congress or the USPTO may impact the value of our patent rights. This combination of events has created uncertainty with respect to the validity and enforceability of patents, once obtained. Depending on future actions by the U.S. Congress, the federal courts and the USPTO, the laws and regulations governing patents could change in unpredictable ways that could have a material adverse effect on our existing patent portfolio and our ability to protect and enforce our intellectual property in the future.

Issued patents covering our vaccine candidates could be found invalid or unenforceable if challenged in court or before administrative bodies in the United States or abroad.

Our patent rights may be subject to priority, validity, inventorship and enforceability disputes. If we or our licensors are unsuccessful in any of these proceedings, such patents and patent applications may be narrowed,

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invalidated or held unenforceable, we may be required to obtain licenses from third parties, which may not be available on commercially reasonable terms or at all, or we may be required to cease the development, manufacture and commercialization of HIL-214 or one or future vaccine candidates. Any of the foregoing could have a material adverse effect on our business, financial condition, results of operations and prospects.

If we or our licensors’ initiated legal proceedings against a third party to enforce a patent covering our vaccine candidates, the defendant could counterclaim that such patent is invalid or unenforceable. In patent litigation in the United States, defendant counterclaims alleging invalidity or unenforceability are commonplace. Grounds for a validity challenge could include an alleged failure to meet any of several statutory requirements, including lack of novelty, obviousness, non-enablement, lack of sufficient written description, failure to claim patent-eligible subject matter or obviousness-type double patenting. Grounds for an unenforceability assertion could be an allegation that someone connected with prosecution of the patent withheld relevant information from the USPTO, or made a misleading statement, during prosecution. Third parties may raise claims challenging the validity or enforceability of a patent before administrative bodies in the United States or abroad, even outside the context of litigation. Such mechanisms include re-examination, post-grant review, inter partes review, interference proceedings, derivation proceedings, and equivalent proceedings in foreign jurisdictions (e.g., opposition proceedings). Such proceedings could result in the revocation of, cancellation of or amendment to our patent rights in such a way that they no longer cover our vaccine candidates or prevent third parties from competing with our vaccine candidates. The outcome following legal assertions of invalidity and unenforceability is unpredictable. With respect to the validity question, for example, we cannot be certain that there is no invalidating prior art, of which we or our licensing partners and the patent examiner were unaware during prosecution. If a third party were to prevail on a legal assertion of invalidity or unenforceability, we would lose at least part, and perhaps all, of the patent protection on our vaccine candidates. Such a loss of patent protection would have a material adverse impact on our business, financial condition, results of operations and prospects.

Patent terms may be inadequate to protect the competitive position of our vaccine candidates for an adequate amount of time.

Patents have a limited lifespan. In the United States, if all maintenance fees are timely paid, the natural expiration of a patent is generally 20 years from its earliest U.S. non-provisional or international patent application filing date. Various extensions may be available, but the life of a patent, and the protection it affords, is limited. Even if patents covering our vaccine candidates are obtained, once the patent has expired, we may be vulnerable to competition from competitive products, including generics or biosimilars. Given the amount of time required for the development, testing and regulatory review of new vaccine candidates, patents protecting such vaccine candidates might expire before or shortly after such vaccine candidates are commercialized. As a result, our in-licensed patent portfolio may not provide us with sufficient rights to exclude others from commercializing products similar or identical to ours. For additional information on the anticipated expiration dates of our licensed patents, see “Business—Intellectual Property.”

If we do not obtain patent term extension and equivalent extensions outside of the United States for our vaccine candidates, our business may be materially harmed.

Depending upon the timing, duration and specifics of any FDA marketing approval of HIL-214 or any future vaccine candidate we may develop, one or more of our in-licensed issued U.S. patents or issued U.S. patents we may own in the future may be eligible for limited patent term extension under the Hatch-Waxman Amendments. The Hatch-Waxman Amendments permit a patent term extension (PTE) of up to five years as compensation for patent term lost during the FDA regulatory review process. A patent term extension cannot extend the remaining term of a patent beyond a total of 14 years from the date of product approval, only one patent may be extended, and only those

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claims covering the approved drug, a method for using it or a method for manufacturing it may be extended. Similar patent term restoration provisions to compensate for commercialization delay caused by regulatory review are also available in certain foreign jurisdictions, such as in Europe under Supplemental Protection Certificate (SPC). However, we may not be granted an extension for various reasons, including failing to exercise due diligence during the testing phase or regulatory review process, failing to apply within applicable deadlines, failing to apply prior to expiration of relevant patents, or failing to satisfy other applicable requirements. Moreover, the applicable time period or the scope of patent protection afforded could be less than we request. In addition, to the extent we wish to pursue patent term extension based on a patent that we in-license from a third party, we may need the cooperation of that third party. If we are unable to obtain patent term extension, or the foreign equivalent, or if the term of any such extension is less than we request, our competitors may obtain approval of competing products following our patent expiration, and our business, financial condition, results of operations and prospects could be materially harmed. For additional information on the anticipated expiration dates of our licensed patents, see “Business—Intellectual Property.”

We may be subject to claims challenging the inventorship of our patents and other intellectual property.

We or our licensors may be subject to claims that former employees, collaborators or other third parties have an interest in our patent rights, trade secrets, or other intellectual property as an inventor or co-inventor. For example, we may have inventorship disputes arise from conflicting obligations of consultants or others who are involved in developing our vaccine candidates and other proprietary technologies we may develop. Litigation may be necessary to defend against these and other claims challenging inventorship or our patent rights, trade secrets or other intellectual property. If we fail in defending any such claims, in addition to paying monetary damages, we may lose valuable intellectual property rights, such as exclusive ownership of, or right to use, intellectual property that is important to our vaccine candidates and other proprietary technologies we may develop. Even if we are successful in defending against such claims, litigation could result in substantial costs and be a distraction to our management and other employees. Any of the foregoing could have a material adverse effect on our business, financial condition, results of operations and prospects.

If we are unable to protect the confidentiality of our trade secrets, our business and competitive position would be harmed.

In addition to seeking patent protection for our vaccine candidates and proprietary technologies, we also rely on trade secret protection and confidentiality agreements to protect our unpatented know-how, technology, and other proprietary information and to maintain our competitive position. We seek to protect these trade secrets and other proprietary technology, in part, by entering into non-disclosure and confidentiality agreements with parties who have access to them, such as our employees, third-party collaborators, CROs, contract manufacturers, consultants, advisors and other third parties. We also enter into confidentiality and invention or patent assignment agreements with our employees and consultants. Trade secrets and know-how can be difficult to protect. We cannot guarantee that we have entered into applicable agreements with each party that may have or have had access to our trade secrets or proprietary technology and processes. Despite these efforts, any of these parties may breach the agreements and disclose our proprietary information, including our trade secrets, and we may not be able to obtain adequate remedies for such breaches. Enforcing a claim that a party illegally disclosed or misappropriated a trade secret is difficult, expensive and time-consuming, and the outcome is unpredictable. In addition, some courts inside and outside the United States are less willing or unwilling to protect trade secrets. If any of our trade secrets were to be lawfully obtained or independently developed by a competitor or other third party, we would have no right to prevent them from using that technology or information to compete with us. If any of our trade secrets were to be disclosed or misappropriated, or if any such information were to be independently developed by a competitor or other third party, our competitive position would be materially and adversely harmed.

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We may be subject to claims that third parties have an ownership interest in our trade secrets. For example, we may have disputes arise from conflicting obligations of our employees, consultants or others who are involved in developing our vaccine candidate. Litigation may be necessary to defend against these and other claims challenging ownership of our trade secrets. If we fail in defending any such claims, in addition to paying monetary damages, we may lose valuable trade secret rights, such as exclusive ownership of, or right to use, trade secrets that are important to our vaccine candidates and other proprietary technologies we may develop. Such an outcome could have a material adverse effect on our business. Even if we are successful in defending against such claims, litigation could result in substantial costs and be a distraction to our management and other employees. Any of the foregoing could have a material adverse effect on our business, financial condition, results of operations and prospects.

We may not identify relevant third-party patents or may incorrectly interpret the relevance, scope or expiration of a third-party patent, which might adversely affect our ability to develop and market our products and vaccine candidates.

We cannot guarantee that any of our or our licensors’ patent searches or analyses, including the identification of relevant patents, the scope of patent claims or the expiration of relevant patents, are complete or thorough, nor can we be certain that we or our licensors have identified each and every third-party patent and pending patent application in the United States and abroad that is relevant to or necessary for the commercialization of our current and future products and vaccine candidates in any jurisdiction. Patent applications in the United States and elsewhere are not published until approximately 18 months after the earliest filing for which priority is claimed, with such earliest filing date being commonly referred to as the priority date. Therefore, patent applications covering our vaccine candidates could have been filed by others without our knowledge. Additionally, pending patent applications that have been published can, subject to certain limitations, be later amended in a manner that could cover vaccine candidates or the use of our vaccine candidates.

The scope of a patent claim is determined by the interpretation of the law, the words of a patent claim, the written disclosure in a patent and the patent’s prosecution history. Our interpretation of the relevance or the scope of a patent or a pending patent application may be incorrect, which may negatively impact our ability to market our products. We may incorrectly determine that our products or vaccine candidates are not covered by a third-party patent or may incorrectly predict whether a third party’s pending patent application will issue with claims of relevant scope. Our determination of the expiration date of any patent in the United States or abroad that we consider relevant may be incorrect, and we may incorrectly conclude that a third-party patent is invalid or unenforceable. Our failure to identify and correctly interpret relevant patents may negatively impact our ability to develop and market our products and vaccine candidates. If we fail to identify and correctly interpret relevant patents, we may be subject to infringement claims. We cannot guarantee that we will be able to successfully settle or otherwise resolve such infringement claims. If we fail in any such dispute, in addition to being forced to pay damages, we may be temporarily or permanently prohibited from commercializing any of our vaccine candidates that are held to be infringing. We might, if possible, also be forced to redesign vaccine candidates or services so that we no longer infringe the third-party intellectual property rights. Any of these events, even if we were ultimately to prevail, could require us to divert substantial financial and management resources that we would otherwise be able to devote to our business.

We may be subject to claims asserting that our employees, consultants or advisors have wrongfully used or disclosed alleged trade secrets of their current or former employers or claims asserting ownership of what we regard as our own intellectual property.

Some of our employees, consultants and advisors are currently or were previously employed at universities or other biotechnology or pharmaceutical companies, including our competitors or potential competitors. Although we try to ensure that our employees, consultants and advisors do not use the proprietary information or know-how of others in their work for us, we may be subject to claims that we or these individuals have used

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or disclosed intellectual property, including trade secrets or other proprietary information, of any such individual’s current or former employer. Litigation may be necessary to defend against these claims. If we fail in defending any such claims, in addition to paying monetary damages, we may lose valuable intellectual property rights or personnel. Even if we are successful in defending against such claims, litigation could result in substantial costs and be a distraction to our management.

In addition, while it is our policy to require our employees and contractors who may be involved in the conception or development of intellectual property to execute agreements assigning such intellectual property to us, we may be unsuccessful in executing such an agreement with each party who, in fact, conceives or develops intellectual property that we regard as our own. The assignment of intellectual property rights may not be self executing, or the assignment agreements may be breached, and we may be forced to bring claims against third parties, or defend claims that they may bring against us, to determine the ownership of what we regard as our intellectual property. Such claims could have a material adverse effect on our business, financial condition, results of operations and prospects.

Third-party claims of intellectual property infringement, misappropriation or other violations against us or our potential future collaborators could be expensive and time consuming and may prevent or delay the development and commercialization of our vaccine candidates.

Our commercial success depends in part on our ability to avoid infringing, misappropriating and otherwise violating the patents and other intellectual property rights of third parties. There is a substantial amount of complex litigation involving patents and other intellectual property rights in the biotechnology and pharmaceutical industries, as well as administrative proceedings for challenging patents, including interference, derivation and reexamination proceedings before the USPTO or oppositions and other comparable proceedings in foreign jurisdictions. As discussed above, recently, due to changes in U.S. law referred to as patent reform, new procedures including inter partes review and post-grant review have also been implemented. As stated above, this reform adds uncertainty to the possibility of challenge to our patent rights in the future.

Numerous U.S. and foreign issued patents and pending patent applications owned by third parties exist in the fields in which we are commercializing or plan to commercialize HIL-214. As the biotechnology and pharmaceutical industries expand and more patents are issued, and as we gain greater visibility and market exposure as a public company, the risk increases that HIL-214 or any future vaccine candidates, and commercializing activities may give rise to claims of infringement of the patent rights of others. We cannot assure you that HIL-214 or any future vaccine candidates will not infringe existing or future patents owned by third parties. We may not be aware of patents that have already been issued for which a third party, such as a competitor in the fields in which we are developing our vaccine candidates, might accuse us of infringing. It is also possible that patents owned by third parties of which we are aware, but which we do not believe we infringe or that we believe we have valid defenses to any claims of patent infringement, could be found to be infringed by us. It is not unusual that corresponding patents issued in different countries have different scopes of coverage, such that in one country a third-party patent does not pose a material risk, but in another country, the corresponding third-party patent may pose a material risk to our vaccine candidates. As such, we monitor third-party patents in the relevant pharmaceutical markets. In addition, because patent applications can take many years to issue, there may be currently pending patent applications that may later result in issued patents that we may infringe.

In the event that any third-party claims that we infringe their patents or that we are otherwise employing their proprietary technology without authorization and initiates litigation against us, even if we believe such claims are without merit, a court of competent jurisdiction could hold that such patents are valid, enforceable and infringed by us. Defense of infringement claims, regardless of their merit, would involve substantial litigation expense and would be a substantial diversion of management and other employee resources from our business,

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and may impact our reputation. In the event of a successful claim of infringement against us, we may be enjoined from further developing or commercializing the infringing products or technologies. In addition, we may be required to pay substantial damages, including treble damages and attorneys’ fees for willful infringement, obtain one or more licenses from third parties, pay royalties and/or redesign our infringing products or technologies, which may be impossible or require substantial time and monetary expenditure. Such licenses may not available on commercially reasonable terms or at all. Even if we are able to obtain a license, the license would likely obligate us to pay license fees or royalties or both, and the rights granted to us might be nonexclusive, which could result in our competitors gaining access to the same intellectual property. If we are unable to obtain a necessary license to a third-party patent on commercially reasonable terms or at all, we may be unable to commercialize the infringing products or technologies or such commercialization efforts may be significantly delayed, which could in turn significantly harm our business. In addition, we may in the future pursue patent challenges with respect to third- party patents, including as a defense against the foregoing infringement claims. The outcome of such challenges is unpredictable.

Even if resolved in our favor, the foregoing proceedings could be very expensive, particularly for a company of our size, and time-consuming. Such proceedings could substantially increase our operating losses and reduce the resources available for development activities or any future sales, marketing or distribution activities. We may not have sufficient financial or other resources to conduct such proceedings adequately. Some of our competitors may be able to sustain the costs of litigation or administrative proceedings more effectively than we can because of greater financial resources. Such proceedings may also absorb significant time of our technical and management personnel and distract them from their normal responsibilities. Uncertainties resulting from such proceedings could impair our ability to compete in the marketplace. In addition, there could be public announcements of the results of hearings, motions or other interim proceedings or developments and if securities analysts or investors perceive these results to be negative, it could have a substantial adverse effect on the price of our common stock. The occurrence of any of the foregoing could have a material adverse effect on our business, financial condition or results of operations.

We may become involved in lawsuits to protect or enforce our patent and other intellectual property rights, which could be expensive, time-consuming and unsuccessful.

Third parties, such as a competitor, may infringe our patent rights. In an infringement proceeding, a court may decide that a patent owned by us or licensed to us is invalid or unenforceable or may refuse to stop the other party from using the invention at issue on the grounds that the patent does not cover the technology in question. In addition, our or our licensors’ patent rights may become involved in inventorship, priority or validity disputes. To counter or defend against such claims can be expensive and time-consuming. An adverse result in any litigation proceeding could put our patent rights at risk of being invalidated, held unenforceable or interpreted narrowly. Furthermore, because of the substantial amount of discovery required in connection with intellectual property litigation and proceedings, there is a risk that some of our confidential information could be compromised by disclosure during such litigation and proceedings.

Even if resolved in our favor, litigation or other legal proceedings relating to intellectual property claims may cause us to incur significant expenses and could distract our personnel from their normal responsibilities. In addition, there could be public announcements of the results of hearings, motions or other interim proceedings or developments, and if securities analysts or investors perceive these results to be negative, it could have a substantial adverse effect on the price of our common stock. Such litigation or proceedings could substantially increase our operating losses and reduce the resources available for development activities or any future sales, marketing or distribution activities. We may not have sufficient financial or other resources to conduct such litigation or proceedings adequately. Some of our competitors may be able to sustain the costs of such litigation or proceedings more effectively than we can because of their greater financial resources and more mature and

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developed intellectual property portfolios. Uncertainties resulting from the initiation and continuation of patent litigation or other proceedings could have a material adverse effect on our ability to compete in the marketplace.

If our trademarks and trade names are not adequately protected, then we may not be able to build name recognition in our markets of interest and our business may be adversely affected.

Our registered or unregistered trademarks or trade names may be challenged, infringed, diluted, circumvented or declared generic or determined to be infringing, misappropriating or violating other marks. During trademark registration proceedings, we may receive rejections of our applications by the USPTO or in other foreign jurisdictions. Although we are given an opportunity to respond to such rejections, we may be unable to overcome them. In addition, in the USPTO and in comparable agencies in many foreign jurisdictions, third parties are given an opportunity to oppose pending trademark applications and to seek to cancel registered trademarks. Opposition or cancellation proceedings may be filed against our trademarks, which may not survive such proceedings. Moreover, any name we may propose to use with HIL-214 or any future vaccine candidate in the United States must be approved by the FDA, regardless of whether we have registered it, or applied to register it, as a trademark. Similar requirements exist in Europe. The FDA typically conducts a review of proposed product names, including an evaluation of potential for confusion with other product names. If the FDA or an equivalent administrative body in a foreign jurisdiction objects to any of our proposed proprietary product names, we may be required to expend significant additional resources in an effort to identify a suitable substitute name that would qualify under applicable trademark laws, not infringe, misappropriate or otherwise violate the existing rights of third parties and be acceptable to the FDA. Furthermore, in many countries, owning and maintaining a trademark registration may not provide an adequate defense against a subsequent infringement claim asserted by the owner of a senior trademark.

We may not be able to obtain, protect or enforce our rights to these trademarks and trade names, which we need to build name recognition among potential partners or customers in our markets of interest. At times, competitors or other third parties may adopt trade names or trademarks similar to ours, thereby impeding our ability to build brand identity and possibly leading to market confusion. In addition, there could be potential trade name or trademark infringement, misappropriation, dilution or other claims brought by owners of other registered trademarks or trademarks that incorporate variations of our registered or unregistered trademarks or trade names. Over the long term, if we are unable to establish name recognition based on our trademarks and trade names, then we may not be able to compete effectively and our business may be adversely affected. Our efforts to obtain, enforce or protect our proprietary rights related to trademarks, trade names, domain name or other intellectual property may be ineffective and could result in substantial costs and diversion of resources and could adversely affect our business, financial condition, results of operations and prospects.

Intellectual property rights do not necessarily address all potential threats.

The degree of future protection afforded by our intellectual property rights is uncertain because intellectual property rights have limitations and may not adequately protect our business or permit us to maintain our competitive advantage. For example:

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Should any of the foregoing occur, it could adversely affect our business, financial condition, results of operations and prospects.

We may not be successful in obtaining or maintaining necessary rights to product components and processes for our development pipeline through acquisitions and in-licenses.

The growth of our business may depend in part on our ability to acquire, in-license or use third-party intellectual property and proprietary rights. For example, HIL-214 or any future vaccine candidates may require specific formulations to work effectively and efficiently and we may develop vaccine candidates containing our compounds and pre-existing pharmaceutical compounds, which could require us to obtain rights to use intellectual property held by third parties. For example, we may find from our preclinical or clinical trials that HIL-214 or any future vaccine candidates achieve improved efficacy through combination with proprietary adjuvants. We may not be able to achieve long-term access to these adjuvants or may be only able to do so under unfavorable terms. This could limit the effectiveness of HIL-214 or any future vaccine candidates if we are unable to obtain access to these adjuvants or could impact our potential profitability if we can only obtain access under unfavorable terms. In addition, with respect to any patent or other intellectual property rights we may co-own with third parties, we may require licenses to such co-owners interest to such patents. We may be unable to acquire or in-license any compositions, methods of use, processes or other third-party intellectual property rights from third parties that we identify as necessary or important to our business operations. In addition, we may fail to obtain any of these licenses at a reasonable cost or on reasonable terms, if at all. Were that to happen, we may need to cease use of the compositions or methods covered by those third-party intellectual property rights, and may need to seek to develop alternative approaches that do not infringe, misappropriate or otherwise violate those intellectual property rights, which may entail additional costs and development delays, even if we were able to develop such alternatives, which may not be feasible. Even if we are able to obtain a license, it may be non-exclusive, which means that our competitors may also receive access to the same technologies licensed to us. In that event, we may be required to expend significant time and resources to develop or license replacement technology.

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Additionally, we may collaborate with academic institutions to accelerate our preclinical research or development under written agreements with these institutions. In certain cases, these institutions provide us with an option to negotiate a license to any of the institution’s rights in technology resulting from the collaboration. Even if we hold such an option, we may be unable to negotiate a license from the institution within the specified timeframe or under terms that are acceptable to us. If we are unable to do so, the institution may offer the intellectual property rights to others, potentially blocking our ability to pursue our program.

The licensing and acquisition of third-party intellectual property rights is a competitive area, and companies that may be more established or have greater resources than we do may also be pursuing strategies to license or acquire third-party intellectual property rights that we may consider necessary or attractive in order to commercialize HIL-214 or any future vaccine candidates. More established companies may have a competitive advantage over us due to their size, cash resources and greater clinical development and commercialization capabilities. In addition, companies that perceive us to be a competitor may be unwilling to assign or license rights to us. There can be no assurance that we will be able to successfully complete these types of negotiations and ultimately acquire the rights to the intellectual property surrounding the additional vaccine candidates that we may seek to develop or market. If we are unable to successfully obtain rights to required third-party intellectual property or to maintain the existing intellectual property rights we have, we may have to abandon development of certain programs and our business financial condition, results of operations and prospects could suffer.

Intellectual property discovered through government funded programs may be subject to federal regulations such as “march-in” rights, certain reporting requirements and a preference for U.S.-based companies. Compliance with such regulations may limit our exclusive rights and limit our ability to contract with non-U.S. manufacturers.

We have in-licensed certain patents and patent applications that have been generated through the use of U.S. government funding or grants, and we may acquire or license in the future additional intellectual property rights that have been generated through the use of U.S. government funding or grants. Pursuant to the Bayh-Dole Act of 1980, the U.S. government has certain rights in inventions developed with government funding. Many of the U.S. patents and patent applications that we currently license that may be subject to these government rights are licensed from Takeda pursuant to the Takeda License and relate to HIL-214. These U.S. government rights include a non-exclusive, non-transferable, irrevocable worldwide license to use inventions for any governmental purpose. In addition, the U.S. government has the right, under certain limited circumstances, to require us to grant exclusive, partially exclusive, or non-exclusive licenses to any of these inventions to a third-party if it determines that: (1) adequate steps have not been taken to commercialize the invention; (2) government action is necessary to meet public health or safety needs; or (3) government action is necessary to meet requirements for public use under federal regulations (also referred to as “march-in rights”). If the U.S. government exercises its march-in rights in our current or future intellectual property rights that are generated through the use of U.S. government funding or grants, we could be forced to license or sublicense intellectual property developed by us or that we license on terms unfavorable to us, and there can be no assurance that we would receive compensation from the U.S. government for the exercise of such rights. The U.S. government also has the right to take title to these inventions if the grant recipient fails to disclose the invention to the government or fails to file an application to register the intellectual property within specified time limits. Intellectual property generated under a government funded program is also subject to certain reporting requirements, compliance with which may require us or the applicable licensor to expend substantial resources. In addition, the U.S. government requires that any products embodying any of these inventions or produced through the use of any of these inventions be manufactured substantially in the United States. This preference for U.S. industry may be waived by the federal agency that provided the funding if the owner or

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assignee of the intellectual property can show that reasonable but unsuccessful efforts have been made to grant licenses on similar terms to potential licensees that would be likely to manufacture substantially in the United States or that under the circumstances domestic manufacture is not commercially feasible. This preference for U.S. industry may limit our ability to contract with non-U.S. product manufacturers for products covered by such intellectual property. Any exercise by the government of such rights or failure by us to comply with federal regulations regarding intellectual property rights that were developed through the use of U.S. government funding could have a material adverse effect on our business, financial condition, results of operations, and prospects.

Risks related to our common stock, this offering and being a public company

There has been no public market for our common stock. An active, liquid and orderly market for our common stock may not develop, and you may not be able to resell your common stock at or above the initial public offering price.

Prior to this offering, there has been no public market for our common stock. Although we have applied to list our common stock on the Nasdaq Global Select Market (Nasdaq), an active trading market for our common stock may never develop or may not be sustained following this offering. We and the representatives of the underwriters will determine the initial public offering price of our common stock through negotiation. This price will not necessarily reflect the price at which investors in the market will be willing to buy and sell our shares following this offering. In addition, an active trading market may not develop following the consummation of this offering or, if it is developed, may not be sustained. The lack of an active market may impair your ability to sell your shares at the time you wish to sell them or at a price that you consider reasonable. An inactive market may also impair our ability to raise capital by selling shares and may impair our ability to acquire other businesses or technologies using our shares as consideration, which, in turn, could materially adversely affect our business.

The trading price of the shares of our common stock could be highly volatile, and purchasers of our common stock could incur substantial losses.

Our stock price is likely to be volatile. The stock market in general and the market for stock of biopharmaceutical companies in particular have experienced extreme volatility that has often been unrelated to the operating performance of particular companies. As a result of this volatility, investors may not be able to sell their common stock at or above the initial public offering price. The market price for our common stock may be influenced by the factors discussed in this “Risk factors” section and many others, including:

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In addition, in the past, stockholders have initiated class action lawsuits against biopharmaceutical companies following periods of volatility in the market prices of these companies’ stock. Such litigation, if instituted against us, could cause us to incur substantial costs, divert our management’s attention and resources and damage our reputation, which could have a material adverse effect on our business, financial condition and results of operations and prospects.

We may allocate the net proceeds from this offering in ways of which you and other stockholders may not approve.

Our management will have broad discretion in the application of the net proceeds from this offering, including for any of the purposes described in “Use of proceeds.” Because of the number and variability of factors that will determine our use of the net proceeds from this offering, their ultimate use may vary substantially from their currently intended use. Our management might not apply our net proceeds in ways that ultimately increase the value of your investment, and the failure by our management to apply these funds effectively could harm our business. Pending their use, we may invest the net proceeds from this offering in short-and intermediate-term, interest-bearing obligations, investment-grade instruments, certificates of deposit or direct or guaranteed obligations of the U.S. government. These investments may not yield a favorable return to our stockholders. If we do not invest or apply the net proceeds from this offering in ways that enhance stockholder value, we may fail to achieve expected results, which could cause our stock price to decline.

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You will suffer immediate and substantial dilution in the net tangible book value of the common stock you purchase.

The initial public offering price of our common stock will be substantially higher than the pro forma as adjusted net tangible book value per share of our outstanding common stock immediately after the completion of this offering. Purchasers of common stock in this offering will experience immediate dilution of approximately $            per share, assuming an initial public offering price of $            per share, which is the midpoint of the price range set forth on the cover of this prospectus. In addition, to the extent the Takeda Warrant or our outstanding options are exercised, investors purchasing common stock in this offering will sustain further dilution. For a further description of the dilution that you will experience immediately after this offering, see “Dilution.”

After this offering, our executive officers, directors and principal stockholders, if they choose to act together, will continue to have the ability to significantly influence all matters submitted to stockholders for approval.

Following the completion of this offering, our executive officers, directors and greater than 5% stockholders, in the aggregate, will own approximately    % of our outstanding common stock (assuming no exercise of the underwriters’ option to purchase additional shares and no exercise of outstanding options, warrants or other rights, and without giving effect to any potential purchases by such persons through our directed share program or otherwise in this offering). As a result, such persons, acting together, will have the ability to significantly influence all matters submitted to our board of directors or stockholders for approval, including the appointment of our management, the election and removal of directors and approval of any significant transaction, as well as our management and business affairs. This concentration of ownership may have the effect of delaying, deferring or preventing a change in control, impeding a merger, consolidation, takeover or other business combination involving us, or discouraging a potential acquiror from making a tender offer or otherwise attempting to obtain control of our business, even if such a transaction would benefit other stockholders.

If we were to “reprice” any stock option or stock appreciation right without the approval of our stockholders, proxy advisory firms may issue a negative recommendation on certain of our compensation-related proposals at future annual meetings of our stockholders.

Our 2022 Incentive Award Plan permits the plan administrator, without the approval of our stockholders, to amend any outstanding stock option or stock appreciation right to reduce its price per share, other than in the context of corporate transactions or equity restructurings, as further described in such plan. Proxy advisory firms generally disfavor repricings without stockholder approval under their voting guidelines as currently in effect. In the event we choose to undertake a repricing in the future without the approval of our stockholders, proxy advisory firms may view such an action as a problematic practice under their voting policies and may issue adverse voting recommendations on certain compensation-related proposals at future annual meetings of our stockholders. Certain institutional and other stockholders may similarly view such actions as problematic.

We do not currently intend to pay dividends on our common stock, and, consequently, your ability to achieve a return on your investment will depend on appreciation, if any, in the price of our common stock.

We have never declared or paid any cash dividend on our common stock. We currently anticipate that we will retain future earnings for the development, operation and expansion of our business and do not anticipate declaring or paying any cash dividends for the foreseeable future. In addition, under the terms of our Loan Agreement, we are prohibited from paying any cash dividends and any future debt agreements may preclude us from paying dividends. Any return to stockholders will therefore be limited to the appreciation of their stock. There is no guarantee that shares of our common stock will appreciate in value or even maintain the price at which stockholders have purchased their shares.

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Sales of a substantial number of shares of our common stock by our existing stockholders in the public market could cause our stock price to fall.

Sales of a substantial number of shares of our common stock in the public market or the perception that these sales might occur could significantly reduce the market price of our common stock and impair our ability to raise adequate capital through the sale of additional equity securities.

Based on shares of common stock outstanding as of December 31, 2021, upon the closing of this offering, we will have outstanding a total of            shares of common stock, assuming no exercise of the underwriters’ option to purchase additional shares and no exercise of outstanding options, warrants or other rights. Of these shares, only the            shares of common stock sold in this offering by us, plus any shares sold upon exercise of the underwriters’ option to purchase additional shares, will be freely tradable, without restriction, in the public market immediately following this offering, unless they are purchased by one of our affiliates.

In addition, immediately following the completion of this offering, Takeda will beneficially own    % of our outstanding shares of common stock, including 3,500,000 shares of common stock issuable pursuant to the Takeda Warrant (or    % if the underwriters exercise their option to purchase additional shares in full). The sale by Takeda of a substantial number of shares after this offering, or a perception that such sales could occur, could significantly reduce the market price of our common stock.

Our directors and officers and holders of substantially all of our outstanding securities have entered into lock-up agreements with the underwriters pursuant to which they may not, with limited exceptions, for a period of 180 days from the date of this prospectus, offer, sell or otherwise transfer or dispose of any of our securities, without the prior written consent of J.P. Morgan Securities LLC and SVB Securities LLC. The underwriters may permit our officers, directors and other securityholders who are subject to the lock-up agreements to sell shares prior to the expiration of the lock-up agreements at any time in their sole discretion. See “Underwriting.” Sales of these shares, or perceptions that they will be sold, could cause the trading price of our common stock to decline.

After the lock-up agreements expire, up to an additional    shares of common stock will be eligible for sale in the public market, of which            shares are held by directors, executive officers and other affiliates and will be subject to volume limitations under Rule 144 under the Securities Act, in each case based on shares of common stock outstanding as of December 31, 2021 and without giving effect to any potential purchases by such persons in this offering.

In addition, promptly following this offering, we intend to file one or more registration statements on Form S-8 under the Securities Act registering the issuance of approximately            shares of common stock subject to options or other equity awards issued or reserved for future issuance under our equity incentive plans. Shares registered under these registration statements on Form S-8 will be available for sale in the public market subject to vesting arrangements and exercise of options, the lock-up agreements described above and the restrictions of Rule 144 in the case of our affiliates. If these additional shares of common stock are sold, or if it is perceived that they will be sold, in the public market, the trading price of our common stock could decline.

After this offering, the holders of            shares of our outstanding common stock, or approximately    % of our total outstanding common stock based on shares outstanding as of December 31, 2021, will be entitled to rights with respect to the registration of their shares under the Securities Act, subject to vesting and the 180-day lock-up agreements described above. In addition, upon the closing of this offering Takeda will be entitled to the same rights with respect to the registration of 3,500,000 shares of our common stock underlying the Takeda Warrant. See “Description of capital stock—Registration rights.” Registration of these shares under the Securities Act would result in the shares becoming freely tradable without restriction under the Securities Act, except for shares held by affiliates, as defined in Rule 144 under the Securities Act. Any sales of securities by these stockholders could have a material adverse effect on the trading price of our common stock.

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We are an emerging growth company and a smaller reporting company, and the reduced disclosure requirements applicable to emerging growth companies and smaller reporting companies may make our common stock less attractive to investors.

We are an emerging growth company, as defined in the JOBS Act, and may remain an emerging growth company until the last day of the fiscal year following the fifth anniversary of the completion of this offering. However, if certain events occur prior to the end of such five-year period, including if we become a “large accelerated filer”, as defined under the Exchange Act, our annual gross revenue exceeds $1.07 billion or we issue more than $1.0 billion of non-convertible debt in any three-year period, we will cease to be an emerging growth company prior to the end of such five-year period. For so long as we remain an emerging growth company, we are permitted and intend to rely on exemptions from certain disclosure requirements that are applicable to other public companies that are not emerging growth companies. These exemptions include:

We have taken advantage of reduced reporting burdens in this prospectus. In particular, in this prospectus, we have provided only two years of audited financial statements and have not included all of the executive compensation related information that would be required if we were not an emerging growth company. We cannot predict whether investors will find our common stock less attractive if we rely on these exemptions. If some investors find our common stock less attractive as a result, there may be a less active trading market for our common stock and our stock price may be reduced or more volatile. In addition, the JOBS Act provides that an emerging growth company can take advantage of an extended transition period for complying with new or revised accounting standards. This allows an emerging growth company to delay the adoption of these accounting standards until they would otherwise apply to private companies. We have elected to avail ourselves of this exemption and, therefore, we will not be subject to the same new or revised accounting standards as other public companies that are not emerging growth companies.

We are also a smaller reporting company as defined in the Exchange Act. We may continue to be a smaller reporting company even after we are no longer an emerging growth company. We may take advantage of certain of the scaled disclosures available to smaller reporting companies and will be able to take advantage of these scaled disclosures for so long as our voting and non-voting common stock held by non-affiliates is less than $250.0 million measured on the last business day of our second fiscal quarter, or our annual revenue is less than $100.0 million during the most recently completed fiscal year and our voting and non-voting common stock held by non-affiliates is less than $700.0 million measured on the last business day of our second fiscal quarter.

Provisions in our charter documents and under Delaware law could discourage a takeover that stockholders may consider favorable and may lead to entrenchment of management.

Our amended and restated certificate of incorporation and amended and restated bylaws that will be in effect immediately prior to the consummation of this offering will contain provisions that could significantly reduce

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the value of our shares to a potential acquiror or delay or prevent changes in control or changes in our management without the consent of our board of directors. The provisions in our charter documents will include the following:

We are also subject to the anti-takeover provisions contained in Section 203 of the Delaware General Corporation Law. Under Section 203, a corporation may not, in general, engage in a business combination with any holder of 15% or more of its capital stock unless the holder has held the stock for three years or, among other exceptions, the board of directors has approved the transaction.

Our amended and restated certificate of incorporation and amended and restated bylaws will provide that the Court of Chancery of the State of Delaware will be the exclusive forum for substantially all disputes between us and our stockholders, which could limit our stockholders’ ability to obtain a favorable judicial forum for disputes with us or our directors, officers or employees.

Our amended and restated certificate of incorporation and amended and restated bylaws will provide that the Court of Chancery of the State of Delaware is the exclusive forum for any derivative action or proceeding

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brought on our behalf, any action asserting a breach of fiduciary duty, any action asserting a claim against us arising pursuant to the Delaware General Corporation Law, our amended and restated certificate of incorporation or our amended and restated bylaws, or any action asserting a claim against us that is governed by the internal affairs doctrine; provided, that, this provision would not apply to suits brought to enforce a duty or liability created by the Exchange Act. Furthermore, our amended and restated certificate of incorporation will also provide that unless we consent in writing to the selection of an alternative forum, the federal district courts of the United States shall be the exclusive forum for the resolution of any complaint asserting a cause of action arising under the Securities Act. These choice of forum provisions may limit a stockholder’s ability to bring a claim in a judicial forum that it finds favorable for disputes with us or our directors, officers or other employees, which may discourage such lawsuits against us and our directors, officers and other employees and result in increased costs for investors to bring a claim. By agreeing to this provision, however, stockholders will not be deemed to have waived our compliance with the federal securities laws and the rules and regulations thereunder. Furthermore, the enforceability of similar choice of forum provisions in other companies’ certificates of incorporation has been challenged in legal proceedings, and it is possible that a court could find these types of provisions to be inapplicable or unenforceable. If a court were to find the choice of forum provisions in our amended and restated certificate of incorporation to be inapplicable or unenforceable in an action, we may incur additional costs associated with resolving such action in other jurisdictions, which could adversely affect our business and financial condition.

General risk factors

We will incur significant increased costs as a result of operating as a public company, and our management will be required to devote substantial time to new compliance initiatives.

As a public company, we will incur significant legal, accounting and other expenses that we did not incur as a private company. We will be subject to the reporting requirements of the Exchange Act, which will require, among other things, that we file with the SEC annual, quarterly and current reports with respect to our business and financial condition. In addition, the Sarbanes Oxley Act, as well as rules subsequently adopted by the SEC and Nasdaq to implement provisions of Sarbanes-Oxley, impose significant requirements on public companies, including requiring establishment and maintenance of effective disclosure and financial controls and changes in corporate governance practices. Further, pursuant to the Dodd-Frank Wall Street Reform and Consumer Protection Act of 2010, the SEC has adopted additional rules and regulations in these areas, such as mandatory “say on pay” voting requirements that will apply to us when we cease to be an emerging growth company. Stockholder activism, the current political environment and the current high level of government intervention and regulatory reform may lead to substantial new regulations and disclosure obligations, which may lead to additional compliance costs and impact the manner in which we operate our business in ways we cannot currently anticipate.

We expect the rules and regulations applicable to public companies to substantially increase our legal and financial compliance costs and to make some activities more time consuming and costly. If these requirements divert the attention of our management and personnel from other business concerns, they could have a material adverse effect on our business, financial condition and results of operations. The increased costs will decrease our net income or increase our net loss, and may require us to reduce costs in other areas of our business or increase the prices of our products or services. For example, we expect these rules and regulations to make it more difficult and more expensive for us to obtain director and officer liability insurance, and we may be required to incur substantial costs to maintain the same or similar coverage. We cannot predict or estimate the amount or timing of additional costs we may incur to respond to these requirements. The impact of these requirements could also make it more difficult for us to attract and retain qualified persons to serve on our board of directors, our board committees or as executive officers.

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We are subject to U.S. and certain foreign export and import controls, sanctions, embargoes, anti-corruption laws and anti-money laundering laws and regulations. Compliance with these legal standards could impair our ability to compete in domestic and international markets. We could face criminal liability and other serious consequences for violations, which could harm our business.

We are subject to export control and import laws and regulations, including the U.S. Export Administration Regulations, U.S. Customs regulations, and various economic and trade sanctions regulations administered by the U.S. Treasury Department’s Office of Foreign Assets Controls and anti-corruption and anti-money laundering laws and regulations, including the U.S. Foreign Corrupt Practices Act of 1977, as amended, the U.S. domestic bribery statute contained in 18 U.S.C. § 201, the U.S. Travel Act, the USA PATRIOT Act and other state and national anti-bribery and anti-money laundering laws in the countries in which we conduct activities. Anti-corruption laws are interpreted broadly and prohibit companies and their employees, agents, CROs, contractors and other collaborators and partners from authorizing, promising, offering, providing, soliciting or receiving, directly or indirectly, improper payments or anything else of value to recipients in the public or private sector. We may engage third parties for clinical trials outside of the United States, to sell our products abroad once we enter a commercialization phase, and/or to obtain necessary permits, licenses, patent registrations and other regulatory approvals. We have direct or indirect interactions with officials and employees of government agencies or government-affiliated hospitals, universities and other organizations. We can be held liable for the corrupt or other illegal activities of our employees, agents, CROs, contractors and other collaborators and partners, even if we do not explicitly authorize or have actual knowledge of such activities. Any violations of the laws and regulations described above may result in substantial civil and criminal fines and penalties, imprisonment, the loss of export or import privileges, debarment, tax reassessments, breach of contract and fraud litigation, reputational harm and other consequences.

Furthermore, U.S. export control laws and economic sanctions prohibit the provision of certain products and services to countries, governments, and persons targeted by U.S. sanctions. U.S. sanctions that have been or may be imposed as a result of military conflicts in other countries may impact our ability to continue activities at future clinical trial sites within regions covered by such sanctions. If we fail to comply with export and import regulations and such economic sanctions, penalties could be imposed, including fines and/or denial of certain export privileges. These export and import controls and economic sanctions could also adversely affect our supply chain.

Business disruptions could seriously harm our future revenue and financial condition and increase our costs and expenses.

Our operations could be subject to earthquakes, power shortages, telecommunications failures, water shortages, floods, hurricanes, typhoons, blizzards and other extreme weather conditions, fires, public health pandemics or epidemics (including, for example, the COVID-19 pandemic) and other natural or manmade disasters or business interruptions, for which we are predominantly self-insured. We rely on third-party manufacturers to produce HIL-214. Our ability to obtain clinical supplies of HIL-214 or any future vaccine candidates could be disrupted if the operations of these suppliers were affected by a man-made or natural disaster or other business interruption. In addition, our corporate headquarters is located in Boston, Massachusetts, where we are subject to both severe winter and summer weather conditions. The occurrence of any of these business disruptions could seriously harm our operations and financial condition and increase our costs and expenses.

We and any of our third-party manufacturers or suppliers may use potent chemical agents and hazardous materials, and any claims relating to improper handling, storage or disposal of these materials could be time-consuming or costly.

We and any of our third-party manufacturers or suppliers and current or potential future collaborators will use biological materials, potent chemical agents and may use hazardous materials, including chemicals and biological

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agents and compounds that could be dangerous to human health and safety of the environment. Our operations and the operations of our third-party manufacturers and suppliers also produce hazardous waste products. Federal, state and local laws and regulations govern the use, generation, manufacture, storage, handling and disposal of these materials and wastes. Compliance with applicable environmental laws and regulations may be expensive, and current or future environmental laws and regulations may impair our product development efforts. In addition, we cannot eliminate the risk of accidental injury or contamination from these materials or wastes. We do not carry specific biological or hazardous waste insurance coverage, and our property, casualty and general liability insurance policies specifically exclude coverage for damages and fines arising from biological or hazardous waste exposure or contamination. In the event of contamination or injury, we could be held liable for damages or be penalized with fines in an amount exceeding our resources, and our clinical trials or regulatory approvals could be suspended. Although we maintain workers’ compensation insurance for certain costs and expenses we may incur due to injuries to our employees resulting from the use of hazardous materials or other work-related injuries, this insurance may not provide adequate coverage against potential liabilities. We do not maintain insurance for toxic tort claims that may be asserted against us in connection with our storage or disposal of biologic, hazardous or radioactive materials.

In addition, we may incur substantial costs in order to comply with current or future environmental, health and safety laws and regulations, which have tended to become more stringent over time. These current or future laws and regulations may impair our research, development or production efforts. Failure to comply with these laws and regulations also may result in substantial fines, penalties or other sanctions or liabilities, which could materially adversely affect our business, financial condition, results of operations and prospects.

Unstable market and economic conditions may have serious adverse consequences on our business, financial condition and stock price.

The global credit and financial markets have recently experienced extreme volatility and disruptions, including severely diminished liquidity and credit availability, declines in consumer confidence, declines in economic growth, increases in unemployment rates and uncertainty about economic stability. The financial markets and the global economy may also be adversely affected by the current or anticipated impact of military conflict, including the conflict between Russia and Ukraine, terrorism or other geopolitical events. Sanctions imposed by the United States and other countries in response to such conflicts, including the one in Ukraine, may also adversely impact the financial markets and the global economy, and any economic countermeasures by the affected countries or others could exacerbate market and economic instability. There can be no assurance that further deterioration in credit and financial markets and confidence in economic conditions will not occur. Our general business strategy may be adversely affected by any such economic downturn, volatile business environment or continued unpredictable and unstable market conditions. If the current equity and credit markets deteriorate, it may make any necessary debt or equity financing more difficult, more costly and more dilutive. Failure to secure any necessary financing in a timely manner and on favorable terms could have a material adverse effect on our growth strategy, financial performance and stock price and could require us to delay or abandon clinical development plans. In addition, there is a risk that one or more of our current service providers, manufacturers and other partners may not survive an economic downturn, which could directly affect our ability to attain our operating goals on schedule and on budget.

Our ability to use net operating loss carryforwards and other tax attributes may be limited in connection with this offering or other ownership changes.

We have incurred substantial losses during our history, do not expect to become profitable in the near future and may never achieve profitability. To the extent that we continue to generate taxable losses, unused losses will carry forward to offset future taxable income (subject to limitations), if any, until such unused losses expire (if at all). As of December 31, 2021, we had net operating loss (NOL) carryforwards of $13.4 million for federal

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income tax purposes and $2.9 million for state income tax purposes. Our state NOL carryforwards begin to expire in various amounts in 2041. Our federal NOL carryforwards will not expire but may generally only be used to offset 80% of taxable income, which may require us to pay federal income taxes in future years despite generating federal NOL carryforwards in prior years.

In addition, our NOL carryforwards and other tax attributes are subject to review and possible adjustment by the Internal Revenue Service (IRS) and state tax authorities. Furthermore, in general, under Section 382 of the U.S. Internal Revenue Code of 1986, as amended (the Code), our federal NOL carryforwards may be or become subject to an annual limitation in the event we have had or have in the future an “ownership change.” For these purposes, an “ownership change” generally occurs if one or more stockholders or groups of stockholders who own at least 5% of a company’s stock increase their ownership by more than 50 percentage points over their lowest ownership percentage within a rolling three-year period. Similar rules may apply under state tax laws. We have not yet determined the amount of the cumulative change in our ownership resulting from this offering or other transactions, or any resulting limitations on our ability to utilize our NOL carryforwards and other tax attributes. However, we believe that our ability to utilize our NOL carryforwards and other tax attributes to offset future taxable income or tax liabilities may be limited as a result of ownership changes, including potential changes in connection with this offering. If we earn taxable income, such limitations could result in increased future income tax liability to us and our future cash flows could be adversely affected. We have recorded a full valuation allowance related to our NOL carryforwards and other deferred tax assets due to the uncertainty of the ultimate realization of the future benefits of those assets.

Changes in tax law may materially adversely affect our financial condition, results of operations and cash flows.

New income, sales, use or other tax laws, statutes, rules, regulations or ordinances could be enacted at any time, or interpreted, changed, modified or applied adversely to us, any of which could adversely affect our business operations and financial performance. In particular, the U.S. government may enact significant changes to the taxation of business entities including, among others, an increase in the corporate income tax rate and the imposition of minimum taxes or surtaxes on certain types of income. The likelihood of these changes being enacted or implemented is unclear. We are currently unable to predict whether such changes will occur. If such changes are enacted or implemented, we are currently unable to predict the ultimate impact on our business. We urge our investors to consult with their legal and tax advisors with respect to any changes in tax law and the potential tax consequences of investing in our common stock.

If securities or industry analysts do not publish research or reports or publish unfavorable research or reports about our business, our stock price and trading volume could decline.

The trading market for our common stock will depend in part on the research and reports that securities or industry analysts publish about us, our business, our market or our competitors. We do not currently have and may never obtain research coverage by securities and industry analysts. If no securities or industry analysts commence coverage of our company, the trading price for our stock would be negatively impacted. In the event we obtain securities or industry analyst coverage, if one or more of the analysts who covers us downgrades our stock, or if we fail to meet the expectations of one or more of these analysts, our stock price would likely decline. If one or more of these analysts ceases to cover us or fails to regularly publish reports on us, interest in our stock could decrease, which could cause our stock price or trading volume to decline.

If we fail to maintain proper and effective internal control over financial reporting, our ability to produce accurate and timely financial statements could be impaired, investors may lose confidence in our financial reporting and the trading price of our common stock may decline.

Pursuant to Section 404 of the Sarbanes-Oxley Act, our management will be required to report upon the effectiveness of our internal control over financial reporting beginning with the annual report for our fiscal year

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ending December 31, 2023. When we lose our status as an “emerging growth company” and do not otherwise qualify as a “smaller reporting company” with less than $100 million in annual revenue, our independent registered public accounting firm will be required to attest to the effectiveness of our internal control over financial reporting. The rules governing the standards that must be met for our management to assess our internal control over financial reporting are complex and require significant documentation, testing and possible remediation. To comply with the requirements of being a reporting company under the Exchange Act, we may need to upgrade our information technology systems; implement additional financial and management controls, reporting systems and procedures; and hire additional accounting and finance staff. If we or, if required, our auditors are unable to conclude that our internal control over financial reporting is effective, investors may lose confidence in our financial reporting and the trading price of our common stock may decline.

We cannot assure you that there will not be material weaknesses or significant deficiencies in our internal control over financial reporting in the future. Any failure to maintain internal control over financial reporting could severely inhibit our ability to accurately report our financial condition, results of operations or cash flows. If we are unable to conclude that our internal control over financial reporting is effective, or if our independent registered public accounting firm determines we have a material weakness or significant deficiency in our internal control over financial reporting once that firm begin its Section 404 reviews, investors may lose confidence in the accuracy and completeness of our financial reports, the market price of our common stock could decline, and we could be subject to sanctions or investigations by Nasdaq, the SEC or other regulatory authorities. Failure to remedy any material weakness in our internal control over financial reporting, or to implement or maintain other effective control systems required of public companies, could also restrict our future access to the capital markets.

We could be subject to securities class action litigation.

In the past, securities class action litigation has often been brought against a company following a decline in the market price of its securities. This risk is especially relevant for us, because biotechnology and biopharmaceutical companies have experienced significant stock price volatility in recent years. If we face such litigation, it could result in substantial costs and a diversion of our management’s attention and resources, which could harm our business.

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Special note regarding forward-looking statements

This prospectus contains forward-looking statements. All statements other than statements of historical fact contained in this prospectus, including statements regarding our future results of operations and financial position, business strategy, research and development plans, the anticipated timing, costs, design and conduct of our planned and potential clinical trials and preclinical studies for HIL-214 and any future vaccine candidates, the timing and likelihood of regulatory filings and approvals for HIL-214 and any future vaccine candidates, our ability to commercialize our vaccine candidates, if approved, the impact of COVID-19 on our business, the pricing and reimbursement of our vaccine candidates, if approved, the potential to develop future vaccine candidates, the potential benefits of strategic collaborations and our intent to enter into any strategic arrangements, the timing and likelihood of success, plans and objectives of management for future operations, and future results of anticipated product development efforts, are forward-looking statements. These statements involve known and unknown risks, uncertainties and other important factors that may cause our actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by the forward-looking statements.

In some cases, you can identify forward-looking statements by terms such as “may,” “will,” “should,” “expect,” “plan,” “anticipate,” “could,” “intend,” “target,” “project,” “contemplates,” “believes,” “estimates,” “predicts,” “potential” or “continue” or the negative of these terms or other similar expressions. The forward-looking statements in this prospectus are only predictions. We have based these forward-looking statements largely on our current expectations and projections about future events and financial trends that we believe may affect our business, financial condition, results of operations and prospects. These forward-looking statements speak only as of the date of this prospectus and are subject to a number of risks, uncertainties and assumptions described under the sections titled “Risk factors” and “Management’s discussion and analysis of financial condition and results of operations” and elsewhere in this prospectus. Forward-looking statements are inherently subject to risks and uncertainties, some of which cannot be predicted or quantified and some of which are beyond our control, and therefore should not be considered predictions of future events. The events and circumstances reflected in our forward-looking statements may not be achieved or occur and actual results could differ materially from those projected in the forward-looking statements. Moreover, we operate in an evolving environment. New risk factors and uncertainties may emerge from time to time, and it is not possible for management to predict all risk factors and uncertainties. Except as required by applicable law, we undertake no obligation to publicly update or revise any forward-looking statements contained herein, whether as a result of any new information, future events, changed circumstances or otherwise. You should, however, review the factors and risks we describe in the reports we will file from time to time with the SEC after the date of this prospectus. See the section titled “Where you can find more information.”

In addition, statements that “we believe” and similar statements reflect our beliefs and opinions on the relevant subject. These statements are inherently uncertain and are based upon information available to us as of the date of this prospectus, and while we believe such information forms a reasonable basis for such statements, such information may be limited or incomplete, and our statements should not be read to indicate that we have conducted an exhaustive inquiry into, or review of, all potentially available relevant information.

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Market and industry data

We obtained the industry, market and competitive position data used throughout this prospectus from our own internal estimates and research, as well as from independent market research, industry and general publications and surveys, governmental agencies and publicly available information in addition to research, surveys and studies conducted by third parties. Internal estimates are derived from publicly available information released by industry analysts and third-party sources, our internal research and our industry experience, and are based on assumptions made by us based on such data and our knowledge of our industry and market. In some cases, we do not expressly refer to the sources from which this data is derived. In that regard, when we refer to one or more sources of this type of data in any paragraph, you should assume that other data of this type appearing in the same paragraph is derived from the same sources, unless otherwise expressly stated or the context otherwise requires. In addition, while we believe the industry, market and competitive position data included in this prospectus is reliable and based on reasonable assumptions, such data involve risks and uncertainties and are subject to change based on various factors, including those discussed in the section titled “Risk factors.” These and other factors could cause results to differ materially from those expressed in the estimates made by the independent parties or by us.

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Use of proceeds

We estimate that the net proceeds to us from this offering will be approximately $                 million (or approximately $                 million if the underwriters exercise their option to purchase additional shares in full) from the sale of the shares of common stock offered by us in this offering, assuming an initial public offering price of $     per share, the midpoint of the price range set forth on the cover page of this prospectus, and after deducting estimated underwriting discounts and commissions and estimated offering expenses payable by us.

Each $1.00 increase (decrease) in the assumed initial public offering price of $                 per share, the midpoint of the price range set forth on the cover page of this prospectus, would increase (decrease) the net proceeds to us from this offering by approximately $                 million, assuming that the number of shares offered by us, as set forth on the cover page of this prospectus, remains the same, and after deducting estimated underwriting discounts and commissions and estimated offering expenses payable by us. We may also increase or decrease the number of shares we are offering. A one million share increase (decrease) in the number of shares offered by us would increase (decrease) the net proceeds to us from this offering by approximately $     million, assuming that the assumed initial public offering price of $                 per share, the midpoint of the price range set forth on the cover page of this prospectus, remains the same, and after deducting estimated underwriting discounts and commissions and estimated offering expenses payable by us. We do not expect that a change in the initial public offering price or the number of shares by these amounts would have a material effect on our intended uses of the net proceeds from this offering, although it may accelerate the time at which we will need to seek additional capital.

The principal purposes of this offering are to obtain additional capital to support our operations, to create a public market for our common stock and to facilitate our future access to the public equity markets. We intend to use approximately $                of the net proceeds from this offering to fund the clinical development of HIL-214, including certain manufacturing activities, and the remainder for working capital and general corporate purposes.

We may also use a portion of the remaining net proceeds to in-license, acquire or invest in complementary businesses, technologies, products or assets, although we have no current agreements, commitments or understandings to do so.

Based on our current operating plan, we believe our existing cash, together with the estimated net proceeds from this offering, will be sufficient to meet our anticipated cash requirements through at least the next      months. In particular, we expect that the net proceeds from this offering will allow us to complete enrollment and dosing in our Phase 2b NOR-212 study, technical transfer and manufacturing readiness for producing clinical trial supply for a Phase 3 study, and will be used for working capital and other general corporate purposes, which may include the hiring of additional personnel, capital expenditures and the costs of operating as a public company. We have based this estimate on assumptions that may prove to be wrong, and we could use our available capital resources sooner than we expect. The net proceeds of this offering, together with our existing cash, will not be sufficient to complete development of HIL-214, and after this offering, we will require substantial capital in order to advance HIL-214 and any future vaccine candidates through clinical trials, regulatory approval and commercialization.

Our expected use of existing cash and our net proceeds from this offering represent our intentions based upon our current plans and business conditions, which could change in the future as our plans and business conditions evolve. Predicting the costs necessary to develop vaccine candidates can be difficult and we will need substantial additional capital to complete our clinical development of HIL-214 and any future vaccine candidates. The amounts and timing of our actual expenditures may vary significantly depending on numerous factors, including the progress and costs of our development activities, the status of and results from clinical

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trials, as well as the status and results from our current and any future collaborations with third parties for HIL-214 and any future vaccine candidates, and any unforeseen cash needs.

Our management will have broad discretion in the application of the net proceeds from this offering, and investors will be relying on the judgment of our management regarding the application of those net proceeds. The timing and amount of our actual expenditures will be based on many factors, including cash flows from operations and the anticipated growth of our business. Pending these uses, we plan to invest these net proceeds in short-term, interest bearing obligations, investment-grade instruments, certificates of deposit or direct or guaranteed obligations of the United States.

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Dividend policy

We have never declared or paid, and do not anticipate declaring or paying in the foreseeable future, any cash dividends on our capital stock. We currently intend to retain all available funds and any future earnings to support our operations and finance the growth and development of our business. Any future determination related to our dividend policy will be made at the discretion of our board of directors and will depend upon, among other factors, our results of operations, financial condition, capital requirements, contractual restrictions, business prospects and other factors our board of directors may deem relevant. In addition, under the terms of our Loan Agreement, we are prohibited from paying any cash dividends.

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Capitalization

The following table sets forth our cash and capitalization as of December 31, 2021:

You should read the information in this table together with our combined financial statements and related notes included elsewhere in this prospectus and the section titled “Management’s discussion and analysis of financial condition and results of operations.”

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The table above is based on the number of shares of common stock outstanding as of December 31, 2021 and excludes:

Each $1.00 increase in the assumed initial public offering price of $                per share, the midpoint of the price range set forth on the cover page of this prospectus, would decrease the number of shares of our common stock issued upon conversion of the August 2021 Notes by                shares. Each $1.00 decrease in the assumed initial public offering price of $                per share would increase the number of shares of our common stock issued upon conversion of the August 2021 Notes by                shares.

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Dilution

If you invest in our common stock in this offering, your ownership interest will be immediately diluted to the extent of the difference between the initial public offering price per share of our common stock and the pro forma as adjusted net tangible book value per share of our common stock immediately after this offering.

As of December 31, 2021, our historical net tangible book value (deficit) was $(100.8) million, or $(18.36) per share of our common stock, based on 5,488,000 shares of common stock outstanding as of such date, including 1,561,830 shares subject to forfeiture or our right of repurchase as of such date. Our historical net tangible book value (deficit) per share represents the amount of our total tangible assets less total liabilities, divided by the total number of shares of common stock outstanding at December 31, 2021.

After giving effect to (i) the automatic conversion of the August 2021 Notes into an aggregate of    shares of our common stock immediately prior to the closing of this offering (based on an assumed initial public offering price of $    per share, the midpoint of the price range set forth on the cover page of this prospectus, and assuming the conversion occurs on    , 2022), and (ii) the reclassification of the Takeda Warrant to stockholders’ equity (deficit), our pro forma net tangible book value as of December 31, 2021 would have been approximately $                 million, or approximately $                per share of our common stock.

After giving further effect to the sale of                 shares of our common stock that we are offering at the assumed initial public offering price of $                per share, the midpoint of the price range set forth on the cover page of this prospectus, and after deducting the estimated underwriting discounts and commissions and estimated offering expenses payable by us, our pro forma as adjusted net tangible book value as of December 31, 2021 would have been $                million, or approximately $                per share. This amount represents an immediate increase in pro forma net tangible book value of $                per share to our existing stockholders and an immediate dilution in pro forma net tangible book value of approximately $                per share to new investors participating in this offering.

Dilution per share to new investors is determined by subtracting pro forma as adjusted net tangible book value per share after this offering from the assumed initial public offering price per share paid by new investors. The following table illustrates this dilution (without giving effect to any exercise by the underwriters of their option to purchase additional shares):

A $1.00 increase in the assumed initial public offering price of $    per share, the midpoint of the price range set forth on the cover page of this prospectus, would decrease the number of shares of our common stock issued upon conversion of the August 2021 Notes by                shares, and would increase the pro forma as adjusted net tangible book value per share after this offering by approximately $    , and decrease the dilution in pro forma net tangible book value per share to new investors by approximately $    , assuming that the number of shares offered by us, as set forth on the cover page of this prospectus, remains the same and after deducting

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the estimated underwriting discounts and commissions and the estimated offering expenses payable by us. A $1.00 decrease in the assumed initial public offering price of $    per share would increase the number of shares of our common stock issued upon conversion of the August 2021 Notes by                shares, and would decrease the pro forma as adjusted net tangible book value per share after this offering by approximately $    , and increase the dilution in pro forma net tangible book value per share to new investors by approximately $    , assuming that the number of shares offered by us, as set forth on the cover page of this prospectus, remains the same and after deducting the estimated underwriting discounts and commissions and the estimated offering expenses payable by us.

We may also increase or decrease the number of shares we are offering. An increase of one million shares in the number of shares offered by us, as set forth on the cover page of this prospectus, would increase our pro forma as adjusted net tangible book value per share after this offering by approximately $                and decrease the dilution to investors participating in this offering by approximately $                per share, assuming that the assumed initial public offering price remains the same, and after deducting the estimated underwriting discounts and commissions and the estimated offering expenses payable by us. Similarly, a decrease of one million shares in the number of shares offered by us, as set forth on the cover page of this prospectus, would decrease the pro forma as adjusted net tangible book value per share after this offering by approximately $                and increase the dilution to investors participating in this offering by approximately $                per share, assuming the assumed initial public offering price of $                 per share, the midpoint of the price range set forth on the cover page of this prospectus, remains the same, and after deducting the estimated underwriting discounts and commissions and the estimated offering expenses payable by us.

If the underwriters exercise their option to purchase up to                 additional shares of our common stock in full in this offering, the pro forma as adjusted net tangible book value after the offering would be $                per share, the increase in pro forma as adjusted net tangible book value per share to existing stockholders would be $                per share and the dilution per share to new investors would be $                per share, in each case assuming an initial public offering price of $                per share, the midpoint of the price range set forth on the cover page of this prospectus.

If the Takeda Warrant had been exercised as of December 31, 2021, the pro forma as adjusted net tangible book value after this offering would be approximately $    million, or approximately $    per share, and total dilution per share to new investors would be approximately $    per share.

The following table summarizes, on a pro forma as adjusted basis as of December 31, 2021, the number of shares of common stock purchased or to be purchased from us, the total consideration paid or to be paid to us in cash and the average price per share paid by existing stockholders for shares issued prior to this offering and the price to be paid by new investors in this offering. The calculation below is based on an assumed initial public offering price of $                per share, the midpoint of the price range set forth on the cover page of this prospectus, before deducting the estimated underwriting discounts and commissions and estimated offering expenses payable by us. As the table below shows, investors participating in this offering will pay an average price per share substantially higher than our existing stockholders paid.

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If the underwriters exercise their option to purchase additional shares of our common stock in full:

The foregoing tables and calculations exclude:

To the extent any outstanding warrants, options or other rights are exercised, or we issue additional equity or convertible securities in the future, there will be further dilution to new investors.

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Management’s discussion and analysis of financial condition and results of operations

The following discussion and analysis should be read in conjunction with our combined financial statements and related notes included elsewhere in this prospectus. This discussion and analysis and other parts of this prospectus contain forward-looking statements based upon current beliefs, plans and expectations that involve risks, uncertainties and assumptions, such as statements regarding our plans, objectives, expectations, intentions and projections. Our actual results and the timing of selected events could differ materially from those anticipated in these forward-looking statements as a result of several factors, including those set forth in the section titled “Risk factors” and elsewhere in this prospectus. You should carefully read the “Risk factors” section of this prospectus to gain an understanding of the important factors that could cause actual results to differ materially from our forward-looking statements. Please also see the section titled “Special note regarding forward-looking statements.”

Overview

We are a clinical-stage biopharmaceutical company focused on developing and commercializing novel vaccines. Our initial program, HIL-214, is a VLP-based vaccine candidate for the prevention of moderate-to-severe AGE caused by norovirus infection. It is estimated that norovirus causes nearly 700 million cases of illness and more than 200,000 deaths worldwide per year, as well as significant additional economic and social burden. To date, HIL-214 has been studied in nine clinical trials conducted by Takeda and LigoCyte, which collectively generated safety data from more than 4,500 subjects and immunogenicity data from more than 2,200 subjects, including safety and immunogenicity data from more than 800 pediatric subjects. A randomized, placebo-controlled Phase 2b field efficacy trial enrolled 4,712 adult subjects, and HIL-214 was well tolerated and demonstrated clinical proof of concept in preventing moderate-to-severe cases of AGE from norovirus infection. In September 2021, an open IND was transferred to us from Takeda, under which we plan to initiate a Phase 2b clinical trial in the second quarter of 2022 to evaluate the safety, immunogenicity, and efficacy of HIL-214 in infants. We expect to report interim safety data from this trial for the first 200 subjects in the second half of 2022, interim immunogenicity data for the first 200 subjects in the first half of 2023, and top-line data in the second half of 2023. We believe HIL-214 has the potential to be the first ever vaccine approved for norovirus-related illness and will help grow HilleVax into a leading global vaccines company.

We commenced our operations in 2019 and have devoted substantially all of our resources to date to organizing and staffing our company, business planning, raising capital, in-licensing intellectual property related to our initial vaccine candidate, HIL-214, preparing for our planned clinical trials of HIL-214, and providing other general and administrative support for our operations. We have funded operations to date primarily through the issuance of convertible promissory notes. As of December 31, 2021, we had cash of $124.6 million. From inception to December 31, 2021, we raised aggregate gross proceeds of $137.2 million from the issuance of convertible promissory notes.

We do not have any products approved for sale, have not generated any revenue and have incurred net losses since our inception. Our net losses for the years ended December 31, 2020 and 2021 were $2.1 million and $102.4 million, respectively. As of December 31, 2021, we had an accumulated deficit of $105.2 million. Our net losses may fluctuate significantly from quarter-to-quarter and year-to-year, depending on the timing of our clinical development activities, other research and development activities and pre-commercialization activities. We expect our expenses and operating losses will increase substantially as we advance HIL-214 through clinical trials, seek regulatory approval for HIL-214, expand our clinical, regulatory, quality, manufacturing and commercialization capabilities, incur significant commercialization expenses for marketing, sales, manufacturing and distribution in anticipation of obtaining potential marketing approval for HIL-214, obtain,

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maintain, protect and enforce our intellectual property, expand our general and administrative support functions, including hiring additional personnel, and incur additional costs associated with operating as a public company.

Based on our current operating plan, we believe that our existing cash, together with the estimated net proceeds from this offering, will be sufficient to meet our anticipated cash requirements through at least the next      months. We have never generated any revenue and do not expect to generate any revenue from product sales unless and until we successfully complete development of, and obtain regulatory approval for, HIL-214, which will not be for several years, if ever. Accordingly, until such time as we can generate significant revenue from sales of HIL-214, if ever, we expect to finance our cash needs through equity offerings, our existing Loan Agreement, debt financings, or other capital sources, including potential collaborations, licenses and other similar arrangements. However, we may be unable to raise additional funds or enter into such other arrangements when needed on favorable terms or at all. Our failure to raise capital or enter into such other arrangements when needed would have a negative impact on our financial condition and could force us to delay, limit, reduce or terminate our product development or future commercialization efforts or grant rights to develop and market vaccine candidates that we would otherwise prefer to develop and market ourselves.

The global COVID-19 pandemic continues to evolve, and we will continue to monitor the COVID-19 situation closely. The extent of the impact of the COVID-19 pandemic on our business, operations and clinical development timelines and plans remains uncertain, and will depend on certain developments, including its impact on our clinical trial enrollment, trial sites, manufacturers, CROs and other third parties with whom we do business, as well as its impact on regulatory authorities and our key scientific and management personnel. The ultimate impact of the COVID-19 pandemic, including the impact of new variants of the virus that causes COVID-19, or a similar health epidemic is highly uncertain and subject to change. To the extent possible, we are conducting business as usual, with necessary or advisable modifications to employee travel and most of our non-lab-based employees working remotely. We will continue to actively monitor the evolving situation related to COVID-19 and may take further actions that alter our operations, including those that may be required by federal, state or local authorities, or that we determine are in the best interests of our employees and other third parties with whom we do business. At this point, the extent to which the COVID-19 pandemic may affect our business, operations and development timelines and plans, including the resulting impact on our expenditures and capital needs, remains uncertain and is subject to change.

Financial operations overview

Our combined financial statements include the accounts of HilleVax (formerly MokshaCo, Inc. and also the receiving entity), North Bridge V, Inc. (North Bridge V) and YamadaCo III, Inc. (YamadaCo III), prior to being merged into a single entity effective February 8, 2021. Our combined financial statements also include the accounts of our wholly-owned subsidiary HilleVax GmbH subsequent to its formation in May 2021. HilleVax, North Bridge V and YamadaCo III were entities under common control of Frazier Life Sciences X, L.P. or its affiliates (Frazier), as a result of, among other things, Frazier’s: (i) ownership of a majority of the outstanding capital stock of each of the combined companies; (ii) financing of each of the combined companies; (iii) control of board of directors of each of the combined companies; and (iv) management of each of the combined companies. All of the combined companies were formed for the purpose of identifying potential assets around which to form an operating company. As the merged entities were under common control, the combined financial statements report the financial position, results of operations and cash flows of the combined companies for all periods presented. All intercompany transactions have been eliminated in combination.

License agreement with Takeda

On July 2, 2021, we and Takeda Vaccines, Inc. (Takeda), a subsidiary of Takeda Pharmaceutical Company Limited, entered into a license agreement (the Takeda License), pursuant to which we exclusively in-licensed

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certain intellectual property rights to commercialize HIL-214 products worldwide (excluding Japan) (the Territory). We will be responsible, at our cost, for the development, manufacture and commercialization of HIL-214 products. We are obligated to use commercially reasonable efforts to develop and commercialize HIL-214 products in the Territory, and to seek regulatory approval for such products throughout the world.

We paid Takeda upfront consideration consisting of 500,000 shares of our common stock and a warrant to purchase 3,500,000 shares of our common stock (the Takeda Warrant). We further agreed that, in the event that Takeda’s fully-diluted ownership, including the Takeda Warrant, represents less than a certain specified percentage of our fully-diluted capitalization, including shares issuable upon conversion of outstanding convertible promissory notes, calculated immediately prior to the closing of this offering, we will issue an additional warrant to purchase shares of common stock such that Takeda would hold a certain specified percentage of the fully-diluted capitalization immediately before the closing of this offering. We also paid Takeda $2.5 million in cash upon the consummation of our convertible note financing in August 2021 and are obligated to pay an additional cash payment of $2.5 million upon release of certain drug product and completion of certain regulatory activities. We are required to make to Takeda a one-time payment of $7.5 million upon achievement of a specified development milestone and one-time commercial milestone payments of up to $150.0 million in the aggregate if certain annual sales targets for HIL-214 products are met in the Territory. We agreed to pay Takeda tiered high-single digit to low-teen percentage royalties on net sales of HIL-214 products in the Territory, subject to specified offsets and reductions, and Takeda agreed to pay us tiered mid-single digit to low-double digit percentage royalties on net sales of HIL-214 products in Japan, subject to specified offsets and reductions. Royalties will be payable, on a product-by-product and country-by-country basis beginning on the first commercial sale of such product in such country, until the later of (i) the expiration of the licensed patents covering the applicable product, (ii) the expiration of regulatory exclusivity in such country, or (iii) 20 years following the first commercial sale of such product in such country. For additional information regarding the Takeda License, including termination provisions, see “Business—Intellectual property—License agreement with Takeda.”

Transitional services agreement with Takeda

As contemplated by the Takeda License, on December 17, 2021, we and Takeda entered into a Transitional Services Agreement (the TSA). Pursuant to the TSA, Takeda has agreed to provide, on a transitional basis following the effective date of the Takeda License, certain services related to research and development and regulatory assistance services, oversight and management of ongoing clinical and research studies, and maintenance of certain third party vendor contracts. In consideration for the services provided under the TSA, we have agreed to pay certain specified amounts to Takeda in cash for such services and certain pass-through costs. During 2021, we incurred $4.9 million of research and development expenses for Takeda’s services. For additional information regarding the TSA, including termination provisions, see “Business—Intellectual property—Transitional services agreement with Takeda.”

Components of results of operations

Operating expenses

Research and development

We did not incur any research and development expenses through December 31, 2020. Since December 31, 2020, our research and development expenses have been related to the development of HIL-214. Research and development expenses are recognized as incurred, and payments made prior to the receipt of goods or services to be used in research and development are capitalized until the goods or services are received.

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Research and development expenses include:

We plan to substantially increase our research and development expenses for the foreseeable future as we continue the development of HIL-214. We cannot determine with certainty the timing of initiation, the duration or the completion costs of current or future preclinical studies and clinical trials of HIL-214 or any future vaccine candidates due to the inherently unpredictable nature of clinical and preclinical development. Clinical and preclinical development timelines, the probability of success and development costs can differ materially from expectations. In addition, we cannot forecast whether HIL-214 or any future vaccine candidates may be subject to future collaborations, when such arrangements will be secured, if at all, and to what degree such arrangements would affect our development plans and capital requirements.

Our future development costs may vary significantly based on factors such as:

In-process research and development

In-process research and development expenses for the year ended December 31, 2021 relate to the Takeda License, and includes the $37.7 million purchase price of the acquired research and development assets. The purchase price of the Takeda License consisted of the following: (i) $2.5 million in cash; (ii) issuance to Takeda

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of 500,000 shares of our common stock at a fair value of $4.4 million; (iii) issuance of the Takeda Warrant at an initial fair value of $30.5 million; (iv) issuance of the Takeda Warrant Right, with an initial fair value of $34,000; and (v) $0.3 million of transaction costs incurred by us. The fair value of the Takeda Warrant was derived from the model used to estimate the fair value of our common stock and the fair value of the common stock was determined using the methodologies described below under “Critical accounting policies and significant judgments and estimates—Common stock valuations.”

General and administrative

General and administrative expenses consist of salaries and employee-related costs for personnel in executive, finance and other administrative functions, legal fees relating to intellectual property and corporate matters, and professional fees for accounting, auditing and consulting services. We anticipate that our general and administrative expenses will increase substantially in the future to support our research and development activities, pre-commercial preparation activities for HIL-214 and, if any vaccine candidate receives marketing approval, commercialization activities. We also anticipate increased expenses related to audit, legal, regulatory, and tax-related services associated with maintaining compliance with exchange listing and SEC requirements, director and officer insurance premiums, and investor relations costs associated with operating as a public company.

Interest expense

Interest expense consists of interest on our outstanding convertible promissory notes.

Change in fair value of warrant liabilities

In connection with the Takeda License, we issued the Takeda Warrant and Takeda Warrant Right (together, the Takeda Warrants). The Takeda Warrants are accounted for as liabilities as they do not meet all the conditions for equity classification due to (i) insufficient authorized shares for the Takeda Warrant and (ii) the Takeda Warrant Right is not indexed to our own stock. We adjust the carrying value of our warrant liabilities to their estimated fair value at each reporting date, with any change in fair value of the warrant liabilities recorded as an increase or decrease to change in fair value of warrant liabilities in the combined statements of operations.

Upon the closing of this offering, we expect the Takeda Warrants will be reclassified to stockholders’ equity as a result of meeting the criteria for equity classification, and require a final adjustment to fair value.

Change in fair value of convertible promissory notes

We issued convertible promissory notes in 2019, 2020 and 2021 for which we have elected the fair value option. We adjust the carrying value of our convertible promissory notes to their estimated fair value at each reporting date, with any change in fair value of the convertible promissory notes recorded as an increase or decrease to change in fair value of convertible promissory notes in our combined statements of operations. All outstanding convertible promissory notes and related accrued interest will convert into shares of our common stock upon the closing of this offering.

The fair value of our convertible promissory notes has been estimated using a scenario-based analysis that estimated the fair value of the convertible promissory notes based on the probability-weighted present value of expected future investment returns, considering possible outcomes available to the noteholders, including various IPO, settlement, equity financing, corporate transactions and dissolution scenarios.

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Results of operations

Comparison of the years ended December 31, 2020 and 2021

The following table summarizes our results of operations for the periods indicated (in thousands):

Research and development expenses. We had no research and development expenses for the year ended December 31, 2020 as we had not yet identified or in-licensed a product candidate. The $10.0 million of research and development expenses for the year ended December 31, 2021 consisted of $6.3 million of clinical development expenses for HIL-214, $2.4 million of consulting expenses and $1.3 million of personnel-related expenses.

In-process research and development expenses. We had no in-process research and development expenses for the year ended December 31, 2020. The $37.7 million of in-process research and development expenses for the year ended December 31, 2021 consisted of the purchase price for the research and development assets we acquired as part of the Takeda License.

General and administrative expenses. General and administrative expenses were $1.3 million and $5.8 million for the years ended December 31, 2020 and 2021, respectively. The increase of $4.5 million was due to increases of $1.9 million of personnel-related expenses, $1.3 million in professional services expenses for accounting, audit, tax, valuation and other services, $0.9 million in legal fees related to corporate and other matters and $0.4 million of other expenses.

Other income (expense). Other expense of $0.8 million for the year ended December 31, 2020 consisted of $0.8 million of other expense related to the increase in fair value of our convertible promissory notes and $29,000 of interest expense on those convertible promissory notes. Other expense of $49.0 million for the year ended December 31, 2021 consisted of $25.9 million of other expense related to the increase in the fair value of warrant liabilities, $20.2 million of other expense related to the increase in the fair value of our convertible promissory notes and $2.9 million of interest expense on our outstanding convertible promissory notes.

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Unaudited pro forma net loss per share

The unaudited pro forma basic and diluted net loss per share reflects (i) the automatic conversion of all outstanding convertible promissory notes and related accrued interest into                shares of common stock (assuming an IPO price of $                per share, which is the midpoint of the price range set forth on the cover page of this prospectus and assuming the conversion occurs on                 2022, the expected closing date of this offering), and (ii) the reclassification of the Takeda Warrant to stockholders’ equity (deficit), each as of the beginning of the period presented or the issuance date, if later.

The unaudited pro forma basic and diluted net loss per share amounts do not give effect to the issuance of common stock issued in this offering nor do they give effect to potential dilutive securities where the impact would be anti-dilutive.

The following table summarizes our unaudited pro forma net loss per share (in thousands, except share and per share data):

Liquidity and capital resources

We have incurred net losses and negative cash flows from operations since our inception and anticipate we will continue to incur net losses for the foreseeable future as we continue the development and potential commercialization of HIL-214. We have funded our operations to date through the issuance of convertible promissory notes. As of December 31, 2021, we had cash of $124.6 million.

Term Loan Facility

On April 18, 2022, we entered into a Loan and Security Agreement (Loan Agreement) with Hercules Capital, Inc. (Hercules), as administrative and collateral agent, and the lenders party thereto, providing for term loans (Term Loans) of up to $75.0 million in the aggregate. We borrowed $5.0 million on April 18, 2022 and have the right to borrow up to an additional $10.0 million through December 15, 2022 and up to an additional $15.0 million through June 30, 2023 (collectively, Term Loan 1). We also have the right to borrow up to $20.0 million through June 30, 2023 (Term Loan 2), provided that we have received at least $150.0 million of net cash proceeds from

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this offering, in connection with any other issuance and sale of our equity securities, and/or in connection with any upfront consideration under business development transactions on or prior to March 31, 2023. In addition, we have the right to borrow up to $25.0 million through March 31, 2024 (Term Loan 3), provided that on or prior to March 31, 2023, (i) the condition to Term Loan 2 has been satisfied, (ii) we have announced that our planned Phase 2b clinical trial evaluating the safety, immunogenicity, and efficacy of HIL-214 in infants (HIL-214 Vaccine Trial) will continue without material adverse modification after completion of our planned interim safety and immunogenicity analysis on the first 200 evaluable subjects in the HIL-214 Vaccine Trial, and (iii) we have announced the completion of subject enrollment for the HIL-214 Vaccine Trial, which shall involve the enrollment of approximately 3,000 or more subjects. All Term Loans are subject to a minimum draw amount of $5.0 million and no event of default having occurred and be continuing. The borrowings under the Loan Agreement are collateralized by substantially all of our assets, including intellectual property and certain other assets.

The Term Loans bear (a) cash interest at a floating rate of the higher of (i) the Wall Street Journal prime rate (or 5.00% if less) plus 1.05%, or (ii) 4.55%, and (b) additional interest at a per annum rate equal to 2.85%, with such interest being added to the outstanding principal balance of the Term Loans on a monthly basis. The monthly payments consist of interest-only through June 1, 2025 or, if prior to April 30, 2025, (x) the conditions to Term Loan 2 and Term Loan 3 have been satisfied and (y) we have reasonably determined that (i) the HIL-214 Vaccine Trial has achieved the protocol-specified primary efficacy endpoint and (ii) HIL-214 has demonstrated acceptable safety results in the HIL-214 Vaccine Trial, and, as a result, we support the initiation of a Phase 3 registrational trial as the next immediate step in the development of HIL-214, in each case subject to reasonable verification by Hercules, through June 1, 2026. Subsequent to the interest-only period, the Term Loans will be payable in equal monthly installments of principal, plus accrued and unpaid interest, through the maturity date of May 1, 2027. In addition, we are obligated to pay a final payment fee equal to the greater of (i) $2.1 million and (ii) 7.15% of the original principal amount of the Term Loans. We may elect to prepay all or a portion of the Term Loans prior to maturity, subject to a prepayment fee of up to 2.00% of the then outstanding principal balance and the pro rata application of such payment to the final payment fee. After repayment, no Term Loan amounts may be borrowed again.

The Loan Agreement contains certain customary affirmative and negative covenants and events of default. The affirmative covenants include, among others, covenants requiring us to maintain our legal existence and governmental approvals, deliver certain financial reports, maintain insurance coverage and satisfy certain requirements regarding our operating accounts. The negative covenants include, among others, limitations on our ability to incur additional indebtedness and liens, merge with other companies or consummate certain changes of control, acquire other companies or businesses, make certain investments, pay dividends, transfer or dispose of assets, amend certain material agreements, including the Takeda License, or enter into various specified transactions. Upon the occurrence of an event of default, subject to any specified cure periods, all amounts owed by us would begin to bear interest at a rate that is 4.00% above the rate effective immediately before the event of default and may be declared immediately due and payable by Hercules, as collateral agent.

Convertible promissory note financings

From inception to July 2021, we issued an aggregate of $8.5 million of convertible promissory notes to Frazier (the Frazier Notes), bearing interest at per annum rates ranging from 0.12% to 2.52%. In August 2021, these notes and related accrued interest were exchanged for the August 2021 Notes described below.

On August 31, 2021, we entered into a note purchase agreement under which we issued $139.5 million of unsecured convertible promissory notes (the August 2021 Notes). Of the August 2021 Notes, $103.8 million were issued to new investors, $25.0 million were issued to Frazier for cash and $10.7 million were issued to Frazier in exchange for the then outstanding principal and accrued interest on the Frazier Notes. The August 2021 Notes

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bear interest at a rate of 6% per annum, compounded annually. The August 2021 Notes become payable upon demand of the holders of at least a majority of the outstanding principal, including Frazier (the Requisite Holders), on August 31, 2022 (the Maturity Date), and become due and payable on August 31, 2024, subject to earlier conversion or repayment in the event we complete certain equity financings or a change of control. The August 2021 Notes will automatically convert into shares of our common stock immediately prior to the completion of this offering.

Funding requirements

Based on our current operating plan, we believe that our existing cash, together with the estimated net proceeds from this offering, will be sufficient to meet our anticipated cash requirements through at least the next          months. In particular, we expect the net proceeds from this offering will allow us to complete enrollment and dosing in our Phase 2b NOR-212 study, technical transfer and manufacturing readiness for producing clinical trial supply for a Phase 3 study, and will be used for working capital and other general corporate purposes, which may include the hiring of additional personnel, capital expenditures and the costs of operating as a public company. However, our forecast of the period of time through which our financial resources will be adequate to support our operations is a forward-looking statement that involves risks and uncertainties, and actual results could vary materially. We have based this estimate on assumptions that may prove to be wrong, and we could deplete our capital resources sooner than we expect. Additionally, the process of testing vaccine candidates in clinical trials is costly, and the timing of progress and expenses in these trials is uncertain.

Our future capital requirements will depend on many factors, including:

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Until such time, if ever, as we can generate substantial product revenues to support our cost structure, we expect to finance our cash needs through equity offerings, the Loan Agreement, debt financings, or other capital sources, including potential collaborations, licenses and other similar arrangements. To the extent that we raise additional capital through the sale of equity or convertible debt securities, the ownership interest of our stockholders will be or could be diluted, and the terms of these securities may include liquidation or other preferences that adversely affect the rights of our common stockholders. Debt financing and equity financing, if available, may involve agreements that include covenants limiting or restricting our ability to take specific actions, such as incurring additional debt, making capital expenditures or declaring dividends. If we raise funds through collaborations, or other similar arrangements with third parties, we may have to relinquish valuable rights to our technologies, intellectual property, future revenue streams, research programs or vaccine candidates or grant licenses on terms that may not be favorable to us and/or may reduce the value of our common stock. If we are unable to raise additional funds through equity or debt financings when needed, we may be required to delay, limit, reduce or terminate our product development or future commercialization efforts or grant rights to develop and market our vaccine candidates even if we would otherwise prefer to develop and market such vaccine candidates ourselves. We have prepared cash flow forecasts which indicate that based on our expected operating losses, negative cash flows and maturities of outstanding convertible promissory notes, there is substantial doubt about our ability to continue as a going concern without raising additional capital within 12 months after the date that the combined financial statements for the year ended December 31, 2021 were issued. Our independent registered public accounting firm also included an explanatory paragraph in its report on our combined financial statements as of and for the year ended December 31, 2021 indicating that there is substantial doubt about our ability to continue as a going concern.

Cash flows

The following table sets forth a summary of the net cash flow activity for each of the periods indicated (in thousands):

Operating activities

Net cash used in operating activities for the year ended December 31, 2020 of $1.3 million was due to our net loss of $2.1 million, adjusted for $0.8 million of noncash charges related to the change fair value of convertible

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promissory notes. Net cash used in operating activities for the year ended December 31, 2021 of $7.3 million was due to our net loss of $102.4 million, adjusted for $83.8 million of noncash charges and a $11.3 million net change in operating assets and liabilities. Noncash charges consisted of our in-process research and development charges of $37.7 million related to the Takeda License, $25.9 million related to the change in fair value of warrant liabilities and $20.2 million related to the change in fair value of convertible promissory notes. The net change in operating assets and liabilities primarily related to an $8.5 million increase in accounts payable and accrued expenses in support of the growth in our operating activities and a $2.8 million increase in accrued interest on our outstanding convertible promissory notes.

Investing activities

Net cash used in investing activities for the year ended December 31, 2021 was primarily due to the cash we paid, including transaction costs, to acquire the Takeda License and payments for the acquisition of property and equipment. We had no investing activities prior to 2021.

Financing activities

Net cash provided by financing activities for the years ended December 31, 2020 and 2021 was primarily due to proceeds from our issuance of convertible promissory notes. In addition, during the year ended December 31, 2021, we paid $0.8 million of costs related to our proposed initial public offering.

Contractual obligations and commitments

In August 2021, we issued $139.5 million of convertible promissory notes, all of which remain outstanding as of December 31, 2021. The aggregate principal, plus accured interest thereon, of these convertible promissory notes will automatically convert into shares of our common stock immediately prior to the closing of this offering. See above and Note 4 to our combined financial statements included elsewhere in this prospectus for additional information regarding these convertible promissory notes.

In August 2021, we entered into a five-year noncancelable operating lease for a facility in Switzerland. We are obligated to make monthly rental payments that periodically escalate during the lease term and are subject to additional charges for common area maintenance and other costs. We have an option to extend the lease for a period of five years. See Note 3 to our combined financial statements included elsewhere in this prospectus for additional information regarding this operating lease agreement.

In March 2022, we entered into a ten-year lease for office and laboratory space located in Boston, Massachusetts. The future noncancelable lease payments under this lease, excluding operating expenses and management fees, total $37.4 million.

In April 2022, we borrowed $5.0 million at the inception of the Loan Agreement as described above.

Under the Takeda License, we have milestone payment obligations that are contingent upon the achievement of certain development milestones and specified levels of product sales and are required to make certain royalty payments in connection with the sale of products developed under the agreement. We are currently unable to estimate the timing or likelihood of achieving the milestones or making future product sales. In addition, we have payment obligations under the TSA. See above and Note 3 to our combined financial statements included elsewhere in this prospectus for additional information regarding the Takeda License and TSA.

We enter into contracts in the normal course of business for contract research services, contract manufacturing services, professional services and other services and products for operating purposes. These contracts generally provide for termination after a notice period, and, therefore, are cancelable contracts.

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Critical accounting policies and significant judgments and estimates

Our management’s discussion and analysis of our financial condition and results of operations is based on our combined financial statements, which have been prepared in accordance with generally accepted accounting principles in the United States (GAAP). The preparation of our combined financial statements requires us to make estimates and assumptions that affect the reported amounts of assets, liabilities and expenses and the disclosure of contingent assets and liabilities in our combined financial statements and accompanying notes. We evaluate these estimates and judgments on an ongoing basis. We base our estimates on historical experience and on various other factors that we believe are reasonable under the circumstances, the results of which form the basis for making judgments about the carrying value of assets and liabilities that are not readily apparent from other sources. Actual results may differ from these estimates under different assumptions or conditions.

While our significant accounting policies are more fully described in Note 1 to our combined financial statements included elsewhere in this prospectus, we believe that the following accounting policies are the most critical for fully understanding and evaluating our financial condition and results of operations.

Accrued research and development expenses

As part of the process of preparing our combined financial statements, we are required to estimate our accrued expenses as of each balance sheet date. This process involves reviewing open contracts and purchase orders, communicating with our personnel to identify services that have been performed on our behalf and estimating the level of service performed and the associated cost incurred for the service when we have not yet been invoiced or otherwise notified of the actual cost. We make estimates of our accrued expenses as of each balance sheet date based on facts and circumstances known to us at that time. We periodically confirm the accuracy of our estimates with the service providers and make adjustments, if necessary. The significant estimates in our accrued research and development expenses include the costs incurred for services performed by our vendors in connection with research and development activities for which we have not yet been invoiced.

We base our expenses related to research and development activities on our estimates of the services received and efforts expended pursuant to quotes and contracts with vendors that conduct research and development on our behalf. The financial terms of these agreements are subject to negotiation, vary from contract to contract and may result in uneven payment flows. There may be instances in which payments made to our vendors will exceed the level of services provided and result in a prepayment of the research and development expense. In accruing service fees, we estimate the time period over which services will be performed and the level of effort to be expended in each period. If the actual timing of the performance of services or the level of effort varies from our estimate, we adjust the accrual or prepaid expense accordingly. Advance payments for goods and services that will be used in future research and development activities are expensed when the activity has been performed or when the goods have been received rather than when the payment is made.

Although we do not expect our estimates to be materially different from amounts actually incurred, if our estimates of the status and timing of services performed differ from the actual status and timing of services performed, it could result in us reporting amounts that are too high or too low in any particular period. To date, there have been no material differences between our estimates of such expenses and the amounts actually incurred.

In-process research and development

We evaluate whether acquired intangible assets are a business under applicable accounting standards. Additionally, we evaluate whether the acquired assets have a future alternative use. Intangible assets that do

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not have future alternative use, such as the Takeda License, are considered acquired in-process research and development. When the acquired in-process research and development assets are not part of a business combination, the value of the consideration paid is expensed on the acquisition date.

Fair value of warrant liabilities and convertible promissory notes

As described above, our warrant liabilities and convertible promissory notes are revalued at each reporting period with changes in the fair value of the liabilities recorded as a component of other income (expense) in the combined statements of operations. See Note 1 to our combined financial statements included elsewhere in this prospectus for information concerning certain of the specific assumptions we used in determining the fair value of our warrant liabilities and convertible promissory notes. There are significant judgments and estimates inherent in the determination of the fair value of these liabilities. If we had made different assumptions including, among others, those related to the timing and probability of various corporate scenarios, discount rates, volatilities and exit valuations, the carrying values of our warrant liabilities and convertible promissory notes, and our net loss and net loss per common share could have been significantly different.

Stock-based compensation expense

Stock-based compensation expense represents the cost of the grant date fair value of equity awards recognized over the requisite service period of the awards (generally the vesting period) on a straight-line basis with forfeitures recognized as they occur. Since all equity awards from inception to July 1, 2021 were issued prior to us obtaining the Takeda License on July 2, 2021, we have not recognized any material amount of stock-based compensation and do not have any material amounts of unrecognized stock-based compensation related to those awards.

We estimate the fair value of option grants using the Black-Scholes option pricing model. Estimating the fair value of equity awards as of the grant date using valuation models, such as the Black-Scholes option pricing model, is affected by assumptions regarding a number of variables, including the risk-free interest rate, the expected stock price volatility, the expected term of stock options, the expected dividend yield and the fair value of the underlying common stock on the date of grant. Changes in the assumptions can materially affect the fair value and ultimately how much stock-based compensation expense is recognized. These inputs are subjective and generally require significant analysis and judgment to develop. See Note 5 to our combined financial statements included elsewhere in this prospectus for information concerning certain of the specific assumptions we used in applying the Black-Scholes option pricing model to determine the estimated fair value of our stock options granted during 2021.

As of December 31, 2021, the unrecognized stock-based compensation expense related to stock options was $3.5 million and is expected to be recognized as expense over a weighted average period of approximately 3.95 years. The intrinsic value of all outstanding stock options as of December 31, 2021 was approximately $                 million, based on the assumed initial public offering price of $                 per share (the midpoint of the price range set forth on the cover page of this prospectus), of which approximately $                 million related to vested options and approximately $                 million related to unvested options.

Common stock valuations

Prior to obtaining the Takeda License in July 2021, the fair value of our common stock was nominal because we were not sufficiently capitalized and held no assets that could be used to generate future revenues. Subsequent to obtaining the Takeda License, we estimated the fair value of our common stock using methodologies, approaches and assumptions consistent with the American Institute of Certified Public Accountants Accounting

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and Valuation Guide: Valuation of Privately Held Company Equity Securities Issued as Compensation (the Practice Aid). The Practice Aid prescribes several valuation approaches for setting the value of an enterprise, such as the cost, income and market approaches, and various methodologies for allocating the value of an enterprise to its common stock. We utilized a scenario-based analysis that estimated the fair value per share based on the probability-weighted present value of expected future investment returns, considering each of the possible outcomes available to us, including various initial public offering, stay private and dissolution scenarios, and applying a discount for lack of marketability for certain equity holders. We considered various stay private scenarios using the income approach and allocated the indicated equity value, adjusted for the expected impact of the convertible notes, to each class of equity on a fully-diluted basis, considering option value for certain option classes. We also considered various initial public offering scenarios based on expected equity values in an initial public offering and allocated the indicated equity value to each class of equity on a fully-diluted basis considering the dilutive impacts of the convertible promissory notes.

We considered various objective and subjective factors to determine the fair value of our common stock, including:

There are significant judgments and estimates inherent in the determination of the fair value of our common stock. These judgments and estimates include assumptions regarding our future operating performance, the time to complete an initial public offering or other liquidity event and the determination of the appropriate valuation methods. If we had made different assumptions, our net loss and net loss per common share could have been significantly different.

Following the completion of this offering, the fair value of our common stock will be based on the closing price as reported on the date of grant on the primary stock exchange on which our common stock is traded.

JOBS Act and smaller reporting company

As an emerging growth company under the Jumpstart Our Business Startups Act of 2012 (the JOBS Act), we can take advantage of an extended transition period for complying with new or revised accounting standards. This allows an emerging growth company to delay the adoption of certain accounting standards until those standards would otherwise apply to private companies. We have elected to avail ourselves of this exemption and, therefore, we will not be subject to the same new or revised accounting standards as other public

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companies that are not emerging growth companies. We intend to rely on other exemptions provided by the JOBS Act, including without limitation, not being required to comply with the auditor attestation requirements of Section 404(b) of Sarbanes-Oxley. As a result, our combined financial statements may not be comparable to companies that comply with new or revised accounting pronouncements as of public company effective dates.

We will remain an emerging growth company until the earliest of (i) the last day of the fiscal year following the fifth anniversary of the consummation of this offering, (ii) the last day of the fiscal year in which we have total annual gross revenue of at least $1.07 billion, (iii) the last day of the fiscal year in which we are deemed to be a “large accelerated filer” as defined in Rule 12b-2 under the Exchange Act, which would occur if the market value of our common stock held by non-affiliates exceeded $700.0 million as of the last business day of the second fiscal quarter of such year, or (iv) the date on which we have issued more than $1.0 billion in non-convertible debt securities during the prior three-year period.

We are also a smaller reporting company as defined in the Exchange Act. We may continue to be a smaller reporting company even after we are no longer an emerging growth company. We may take advantage of certain of the scaled disclosures available to smaller reporting companies and will be able to take advantage of these scaled disclosures for so long as our voting and non-voting common stock held by non-affiliates is less than $250.0 million measured on the last business day of our second fiscal quarter, or our annual revenue is less than $100.0 million during the most recently completed fiscal year and our voting and non-voting common stock held by non-affiliates is less than $700.0 million measured on the last business day of our second fiscal quarter.

Recent accounting pronouncements

See Note 1 to our combined financial statements appearing elsewhere in this prospectus for recent accounting pronouncements.

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Business

Our founders and inspirations

We are founded on the legacies of leading vaccine developers who inspire us to build a company to benefit human health on a global scale. Our late co-founder, Dr. Tadataka “Tachi” Yamada, championed vaccines as a powerful means to address health inequities and equalize opportunity for people around the world. As the former Chief Medical and Scientific Officer at Takeda Pharmaceutical Company Limited (Takeda Pharmaceuticals), Tachi helped establish Takeda Pharmaceuticals’ vaccine pipeline, which included the most advanced norovirus vaccine candidate in clinical development. Through his most recent role as a venture partner at Frazier Healthcare Partners (Frazier), he helped Frazier and Takeda Pharmaceuticals launch their third collaboration, HilleVax, to continue the development of this novel norovirus vaccine candidate, HIL-214 (formerly TAK-214). At HilleVax, we aim to continue Tachi’s mission of improving global health with a sense of urgency by always putting patients first.

Our work, and company name itself, is also inspired by Dr. Maurice Hilleman. Dr. Hilleman is considered by many to be the father of modern vaccines. He developed many of the vaccines that are routinely recommended for children today. By the end of his career, Dr. Hilleman had played a key role in developing more than forty vaccines, including those for the flu, chickenpox, hepatitis A, hepatitis B, pneumococcus, meningococcus, measles, mumps, rubella, and other diseases. These vaccines are estimated to save millions of lives every year. We are honored that his daughter, Jeri Hilleman, serves on our Board of Directors.

We aim to have a global impact on human health and believe the best way to achieve this goal is by developing novel vaccines for severe and life-threatening diseases. HIL-214 is our foundational vaccine candidate from which we are building our company. We are honored to continue Dr. Yamada’s and Dr. Hilleman’s legacies through the further development of HIL-214 and other potential vaccine candidates.

Overview

We are a clinical-stage biopharmaceutical company focused on developing and commercializing novel vaccines. Our initial program, HIL-214, is a virus-like particle (VLP) based vaccine candidate for the prevention of moderate-to-severe acute gastroenteritis (AGE) caused by norovirus infection. It is estimated that norovirus causes nearly 700 million cases of illness and more than 200,000 deaths worldwide per year, as well as significant additional economic and social burden. To date, HIL-214 has been studied in nine clinical trials conducted by Takeda Vaccines, Inc. (Takeda) and its predecessor, LigoCyte Pharmaceuticals, Inc. (LigoCyte), which collectively generated safety data from more than 4,500 subjects and immunogenicity, or the ability of the vaccine to provoke an immune response, data from more than 2,200 subjects, including safety and immunogenicity data from more than 800 pediatric subjects. A randomized, placebo-controlled Phase 2b field efficacy trial enrolled 4,712 adult subjects, and HIL-214 was well tolerated and demonstrated clinical proof of concept in preventing moderate-to-severe cases of AGE from norovirus infection. In September 2021, an open investigational new drug application (IND) was transferred to us from Takeda, under which we plan to initiate a Phase 2b clinical trial in the second quarter of 2022 to evaluate the safety, immunogenicity, and efficacy of HIL-214 in infants. We expect to report interim safety data from this trial for the first 200 subjects in the second half of 2022, interim immunogenicity data for the first 200 subjects in the first half of 2023, and top-line data in the second half of 2023. We believe HIL-214 has the potential to be the first ever vaccine approved for norovirus-related illness and will help grow HilleVax into a leading global vaccines company.

Norovirus is the most common cause of viral AGE worldwide and is characterized by diarrhea, vomiting, abdominal pain, nausea, and, sometimes, fever that may lead to clinically significant dehydration. The global cost of norovirus-caused AGE is estimated to be over $4 billion in direct health system costs and approximately

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$60 billion in societal costs per year. In the United States alone, norovirus-caused AGE is estimated to result in $2 billion in direct medical costs and $10 billion in societal costs per year. While norovirus can cause illness in any age group, the majority of deaths and illnesses due to norovirus are borne by young children and older adults. In children younger than four years of age, norovirus is estimated to cause 95,000 deaths and 450 million illnesses globally each year. Up to 80% of children will experience a norovirus infection within one year of birth, with the majority of cases occurring between six months and two years of age. Almost all children will experience at least one norovirus infection by the age of five. In the United States, this results in approximately 627,000 outpatient visits, 281,000 emergency room visits and 14,000 hospitalizations each year for children under the age of five. Older adults are also vulnerable to severe norovirus infection given their higher rate of comorbidities, especially if they live in settings conducive to outbreaks, such as assisted living facilities. For adults older than 55 years of age, norovirus is estimated to cause 78,000 deaths and 81 million illnesses globally each year. In the United States, older adults are estimated to account for 17% of illnesses due to norovirus yet comprise 52% of hospitalizations and 94% of deaths. There are currently no approved vaccines or antiviral therapies for either the prevention or treatment of norovirus-related illness.

In July 2021, Takeda granted us, among other things, an exclusive license (the Takeda License) under certain intellectual property to commercialize HIL-214 (formerly TAK-214) worldwide (excluding Japan) in exchange for upfront consideration as well as future cash milestones and royalties on net sales. Takeda will retain commercialization rights in Japan, and we will integrate certain Japan development activities into our global development plan. As of March 31, 2022, our intellectual property portfolio for HIL-214 includes six issued U.S. composition and formulation patents that are licensed to us under the Takeda License.

HIL-214 is a bivalent (containing two proteins) vaccine candidate consisting of VLPs representing two common genotypes of norovirus and is co-formulated with an aluminum hydroxide (alum) adjuvant, which is commonly used in adult and pediatric vaccines to enhance immunogenicity. Alum may also improve the stability of VLPs in solution. VLPs are self-assembling structures that mimic the unique and repetitive geometric features that characterize the surface of a live virus. VLPs can be produced in a wide range of expression systems and can be readily manufactured at large scale. Importantly, VLPs lack a viral genome and can therefore neither replicate nor cause infection, which may present an important safety advantage over live vaccines. The genotypes represented by the two VLPs in HIL-214 are from the GI and GII genogroups of norovirus, which are responsible for the majority of human norovirus infection. VLP-based vaccines are well-characterized and include currently marketed vaccines, such as Gardasil, Cervarix, and Sci-B-Vac, and have been administered to millions of patients worldwide.

HIL-214 has been extensively evaluated in nine Phase 1 and 2 clinical trials conducted by Takeda. Safety data generated across more than 4,500 subjects in these trials showed that HIL-214 was well tolerated across all age groups and had an adverse event (AE) profile similar to that of other approved alum-adjuvanted vaccines. In infants between six weeks and six months of age who received two doses of HIL-214, AEs were largely mild to moderate in intensity, with the most common reactions being fussiness (19-28%), drowsiness (16-21%), diarrhea (10-19%), and pain near the injection site (9-21%) in 180 subjects studied. In adults, systemic AEs were found to occur at a rate similar to placebo, with the most common local reaction being pain near the injection site (48% for HIL-214 vs. 38% for placebo) in a safety subset of 377 subjects. In addition, immunogenicity data has been collected in over 2,200 subjects. HIL-214 was found to induce antibody responses greater than eight-fold above baseline at least 28 days post vaccination against norovirus in all age groups. An extensive set of clinical dose finding and formulation studies were conducted to evaluate the immune response across age groups and between the two VLPs contained in HIL-214. In a clinical trial of military recruits, in which 4,712 subjects were administered HIL-214 or placebo, HIL-214 demonstrated an estimated 80% efficacy in preventing AGE caused by norovirus strains represented in our vaccine candidate and 62% efficacy for AGE caused by any norovirus strain (including those not represented in HIL-214) in the first 45 days post vaccination. We believe

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this trial demonstrated clinical proof of concept and protection against strains not included in the vaccine (i.e., heterotypic or cross-protection).

Our near-term clinical development plan is focused on infants, a population in which norovirus is routinely circulating and infections are common. We plan to initiate a Phase 2b clinical trial in the second quarter of 2022 to evaluate the safety, immunogenicity, and efficacy of HIL-214 in infants. We expect to report interim safety data from this trial for the first 200 subjects in the second half of 2022, interim immunogenicity data for the first 200 subjects in the first half of 2023, and top-line data in the second half of 2023. While Takeda previously conducted both Phase 1 and 2 clinical trials of HIL-214, we have not previosuly completed any clinical trials. After conclusion of the Phase 2b trial in infants, we plan to proceed to a pivotal Phase 3 efficacy trial in infants. We believe that successful completion of these Phase 2b and Phase 3 trials, together with existing clinical data and additional co-administration trials with other common pediatric vaccines and lot-to-lot consistency trials, will support regulatory submissions for marketing approval in the United States, Europe, Japan, and other key markets. We also expect these data to be evaluated by the Advisory Committee on Immunization Practices (ACIP), an advisory body of the Centers for Disease Control and Prevention (CDC) which develops vaccine recommendations for children and adults in the United States. New pediatric vaccines that receive a preferred recommendation from ACIP are nearly universally adopted in the United States, with many reaching national immunization rates of over 90%. In addition, depending upon the results from our Phase 2b trial in infants, we also plan to initiate a series of trials to support the potential approval of HIL-214 for older children, adults, and older adults.

The global vaccine market is estimated to be over $50 billion in 2020 and is expected to exceed $100 billion by 2027. While there are currently no approved vaccines for the prevention of norovirus-related illness, we believe there are market analogues that we can use to estimate the size of the commercial opportunity for HIL-214. In the pediatric market, we believe that rotavirus vaccines are the closest analogue to HIL-214. Rotavirus was the leading cause of pediatric viral AGE before the introduction of the rotavirus vaccines, Rotarix and RotaTeq. These vaccines, approved only in infants, are now widely adopted worldwide, with many countries achieving vaccination rates above 80% among one-year-olds. Rotavirus vaccines generated approximately $1.6 billion in global sales in 2020. In the older adult market, we believe that Shingrix, a vaccine developed by GlaxoSmithKline to prevent shingles, is an analogue for HIL-214 due to the similarities in morbidity, mortality and economic burden between shingles and norovirus each before the introduction of a vaccine. Shingrix generated $2.7 billion in sales in 2020. Furthermore, we believe that there is a commercial opportunity in other groups at high risk for norovirus infection, such as healthcare workers, immunocompromised individuals, military personnel, food handlers, and travelers, including cruise ship passengers.

Our company was founded by Frazier and Takeda Pharmaceuticals with the goal of developing and commercializing the first vaccine for norovirus-related illness. Our late co-founder, Tachi Yamada, M.D., was the former Chief Medical and Scientific Officer at Takeda Pharmaceuticals. Since our founding, we have assembled a distinguished group of executives, directors, and advisors with extensive experience in vaccine development, clinical trial operations, manufacturing, and commercialization, including prior experience developing HIL-214 at Takeda Pharmaceuticals. Our President, Chief Executive Officer, and Chairman, Rob Hershberg, M.D., Ph.D., was previously Executive Vice President and Chief Scientific Officer of Celgene and was subsequently Executive Vice President and Head of Business Development & Global Alliances and served as a member of the Executive Committee until the acquisition of Celgene by Bristol-Myers Squibb in 2019. David Socks, our Chief Financial Officer and Chief Business Officer, co-founded Arcutis, Cadence Pharmaceuticals, Incline Therapeutics, Passage Bio, and Phathom Pharmaceuticals, where he was the Chief Executive Officer through the company’s initial public offering in 2019 and later served as interim Chief Financial Officer. Aditya Kohli, Ph.D., our Chief Operating Officer, co-founded Scout Bio, Passage Bio, and Phathom Pharmaceuticals, where he was the Chief Business Officer, and currently serves on the board of Scout Bio. Astrid Borkowski, M.D., Ph.D., our Chief

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Medical Officer, is the former VP, Head of Clinical Development at Takeda Pharmaceuticals’ Vaccine Business Unit where she oversaw the clinical development of all vaccine assets, including HIL-214. Paul Bavier, our General Counsel, Secretary, and Chief Administrative Officer, is the former General Counsel at VelosBio, Avedro and Biodel.

Since our inception, we have raised approximately $137.2 million in capital from leading investors, including Frazier Healthcare Partners, RA Capital Management, Deerfield Management Company, Abingworth, Lightspeed Venture Partners, Perceptive Advisors, Franklin Templeton, Catalys Pacific, Samsara BioCapital, BVF Partners LP, Qiming Venture Partners USA, Greenspring Associates, Richard King Mellon Foundation, and Sahsen Ventures.

Our pipeline

The following chart summarizes our current development programs.

Our strategy

Our goal is to be a leader in the development and commercialization of novel vaccines. Our strategy is initially focused on the development and commercialization of HIL-214 as the first potential vaccine for the prevention of AGE caused by norovirus infection. Key elements of this strategy include:

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Overview of norovirus

Overview

Norovirus is the most common cause of viral AGE. AGE is characterized by acute-onset vomiting and diarrhea, typically lasting between one and three days, that may be accompanied by abdominal cramps, nausea, and fever. Most infections result in a full recovery, although severe outcomes such as hospitalization and death are more common among young children and older adults. Given that there are no antiviral therapies available to treat norovirus infections, clinical management is focused on supportive care to prevent dehydration and manage symptoms.

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The burden of norovirus falls disproportionately on young children and older adults. Incidence of norovirus is highest among young children, with 70% of cases in children under four years of age occurring between six months and two years of age. As a result, almost all children will have experienced at least one norovirus infection by the age of five. While incidence is lower among older adults, norovirus illnesses are more likely to result in lingering symptoms, hospitalization, and death in this population. Older adults are also more likely to be found in high risk settings for norovirus outbreaks, such as long-term care facilities and hospitals. Other high-risk groups for norovirus infection include healthcare workers, immuno-compromised individuals, military personnel, food handlers, and travelers, including cruise ship passengers. Globally, norovirus is estimated to result in over approximately 700 million cases of AGE and 200,000 deaths per year, resulting in over $4 billion in direct health system costs and $60 billion in societal costs per year. In the United States alone, norovirus is estimated to result in over 20 million cases of AGE, resulting in over $2 billion in direct medical costs, and $10 billion in indirect societal costs, per year. In addition, outbreaks of norovirus at restaurant chains, cruise ships, and in other industries have caused significant industry disruptions and reputational damage to the affected brands.

Genogroups and genotypes

Noroviruses are a group of small, non-enveloped viruses belonging to the Caliciviridae family. Noroviruses contain a single-stranded positive-sense RNA genome that codes for seven nonstructural and two structural proteins. The first structural protein, VP1, encodes the major capsid protein. VP1 is further subdivided into the N-terminal, shell, and protruding domains. The protruding domain of VP1 is present on the surface of viral particles and is necessary for binding to HBGAs on epithelial cells in the human gastrointestinal tract.

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Noroviruses are classified into ten genetic groups called genogroups. These genogroups, GI through GX, are based on amino acid diversity in the major capsid protein VP1. Genogroups GI and GII are responsible for the majority of human infections across major geographies worldwide, with GII accounting for an estimated 96% of global prevalence. Norovirus genogroups are further subdivided into at least 48 genotypes: 9 genotypes in GI, 26 genotypes in GII, and 13 genotypes in GIII through GX. A single genotype, GII.4, is estimated to be responsible for nearly two-thirds of norovirus outbreaks in both developed and developing countries. GII.4 has been the dominant genotype in circulation for the last two decades, and of the GII.4 strains, GII.4 Sydney 2012 has been the predominant variant detected worldwide since 2012. In addition to causing the majority of norovirus infections, hospitalizations and deaths were more likely in outbreaks associated with GII.4 viruses.

Norovirus attachment and entry

Norovirus entry into host cells is a multi-step process. The first step is norovirus binding to attachment factors that concentrate the virus on the cell surface. The most well-characterized attachment factors are HBGAs. HBGAs are units of simple sugar that are bonded together, or oligosaccharides, found on the epithelia of the respiratory, genitourinary, and digestive tracts, as well as in body fluids such as blood and saliva. The interaction between norovirus and HBGAs is known to promote viral entry into host cells, and this interaction is supported by population genetics. Specifically, individuals with mutations in the FUT2 gene, which is required for secretion of HBGAs into body fluids, are highly resistant to infection by GI.1 and most GII.4 norovirus strains. Approximately 20% of Caucasians lack a functional FUT2 gene. Given the importance of HBGAs for norovirus attachment and cell entry, measurement of HBGA-blocking antibodies is the primary functional method used to assess the immunogenicity of norovirus vaccine candidates. We believe that data from our planned clinical trials of HIL-214 will help determine whether anti-HBGA antibodies are an appropriate surrogate for evaluating norovirus vaccine efficacy.

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The next step for norovirus entry is receptor engagement. Receptors are essential host factors that bind to the norovirus particle and actively promote entry into the cell. The receptor(s) for human norovirus are currently unknown. The last steps for norovirus entry are cell entry, or endocytosis, and uncoating, which results in release of the viral genome into the host cytoplasm. New norovirus particles are then produced and released via cell lysis, which results in inflammation of the stomach or intestines, the underlying pathology of AGE.

Clinical presentation and management

Clinical presentation of norovirus infections can range widely, from asymptomatic infections to life-threatening dehydration and diarrhea. Asymptomatic cases are estimated to account for 30% of norovirus infections. For a symptomatic case, the illness typically begins after an incubation period of 12 to 48 hours and is characterized by acute-onset vomiting and diarrhea that may be accompanied by abdominal cramps, nausea, and fever. Other symptoms, including muscle pain, malaise, headache, and chills, can also occur. The duration of clinical symptoms is typically 12 to 72 hours in otherwise healthy individuals. The most serious complication is severe dehydration leading to hypovolemic shock, which occurs when the body loses more than one-fifth of its fluid supply. Hypovolemic shock makes it difficult for the heart to pump sufficient blood to the body and can lead to organ failure, coma, and death. Severe outcomes of acute AGE as a result of norovirus infection, such as hospitalization and death, are more likely among young children, older adults, and immunocompromised patients.

There are currently no antiviral therapies available to treat norovirus infection. Clinical management is focused on supportive therapy to prevent dehydration. First line therapy is comprised of oral rehydration solutions, followed by intravenous rehydration for patients with profuse vomiting or worsening dehydration that could lead to hypovolemic shock. Medicines to relieve pain, nausea, or vomiting can also be used.

Transmission and prevention

Norovirus is highly transmissible, with as few as 18 viral particles needed to make a person sick. For context, a single gram of feces can contain up to 95 billion particles of norovirus. A systematic review of norovirus outbreak data in the United States from 2009-2017 reported a median R₀ (a measure of the average number of

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people who will contract a viral disease from one infected person) of 2.75, but this number is likely to be a lower bound for norovirus globally given generally high sanitation rates and comparatively easy access to clean food and water in the United States compared to other nations with higher burden of norovirus infection. For context, seasonal strains of influenza in the United States tend to have R₀ values between 1 and 2.

There are three general modes of norovirus transmission: person-to-person, foodborne, and waterborne. Person-to-person transmission occurs mainly through the fecal-oral route and potentially through aerosolized vomitus. Viral shedding in stool can also occur before the onset of symptoms and continue up to eight weeks after a person has been infected, leading to secondary transmission rates, defined as the probability that some or all family members also become infected, of up to 30%^. Person-to-person transmission can also occur indirectly through contaminated fomites, such as clothes and utensils, or through environmental surfaces. Foodborne transmission typically occurs by exposure to infected food handlers, although exposure to human waste further upstream in the food distribution system is also a possibility. For example, oysters filter ocean water through their bodies to get food and will absorb viral particulates when exposed to untreated human waste, which can make its way into ocean water in the case of leaky septic systems and/or dysfunctional waste-water treatment plants. Waterborne transmission can occur through the failure to properly chlorinate municipal water or through the contamination of well water with human waste. Norovirus outbreaks can occur throughout the year, although increased activity is observed in the winter months.

Preventing the spread of norovirus is challenging. The virus can persist on environmental surfaces such as utensils and countertops for up to two weeks. Norovirus can remain infectious on foods that are frozen and until heated above 140°F. Furthermore, alcohol-based hand sanitizers are not as effective at removing norovirus particles as washing hands with soap and water, and their use in place of hand washing is associated with a greater risk for norovirus outbreaks in long-term care facilities. This resistance to common disinfectants appears to be unique to norovirus, as there have not been similar reports of outbreaks associated with the use of hand sanitizers in lieu of handwashing for other common viruses. The CDC recommends four strategies to help prevent the transmission of norovirus: proper hand hygiene, safe food handling, isolation while sick, and surface decontamination. Hand hygiene with running water and soap is viewed as the most effective method to control norovirus transmission. Food and vegetables should be carefully washed before eating, and affected individuals should refrain from preparing food for others for up to two days after symptoms stop. Furthermore, kitchen surfaces and frequently touched objects should be sanitized using chlorine-based disinfectants such as bleach. In the event of an outbreak in a high transmission environment like a cruise ship, nursing home, daycare, or hospital ward, a full decontamination procedure must be performed in order minimize the risk of additional spread.

Burden in young children

Norovirus routinely circulates among young children, a mode of transmission categorized as endemic. Up to 80% of children will experience a norovirus infection within one year of birth, with the majority of cases occurring between six months and two years of age. Although norovirus can infect all age groups, the incidence of norovirus is highest among young children. The GII genogroup is the dominant source of infection in children, accounting for 96% of all sporadic infections, and the GII.4 genotype, in particular, accounts for 70% of detected genotypes. The consistent dominance of GII.4 in circulation over more than two decades, particularly among children, highlights the importance of vaccination efforts to be directed against this strain.

Most infections are completely resolved, resulting in a full recovery, although severe outcomes such as hospitalization and death are more common among young children when considering global burden. In both high- and middle-income countries with mature rotavirus vaccination programs, norovirus is now the most common cause of pediatric gastroenteritis requiring medical care. In the United States, norovirus is estimated

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to result in 627,000 outpatient visits, 281,000 emergency room visits, and 14,000 hospitalizations each year for children under the age of five. Globally, norovirus is estimated to result in 450 million illnesses and 95,000 deaths annually for children under the age of four, resulting in a total societal cost of approximately $39 billion. In the United States alone, norovirus is estimated to result in 2.8 million illnesses annually in children under the age of four, resulting in a total societal cost of approximately $1.2 billion.

For comparison, norovirus today has a similar morbidity, mortality, and economic burden in children as rotavirus did before the introduction of rotavirus vaccines. Prior to rotavirus vaccines becoming available, rotavirus was estimated to result in 2.7 million illnesses each year in children under the age of five in the United States, resulting in a total societal cost of approximately $1.5 billion. Today, rotavirus vaccines are estimated to avert 280,000 outpatient visits, 62,000 emergency room visits, and 45,000 hospitalizations each year in the United States. When considering all age groups, the overall burden of norovirus is greater than that of rotavirus.

Further, norovirus today has a greater morbidity, mortality, and economic burden than shingles did before the introduction of shingles vaccines. Prior to shingles vaccines becoming available, shingles was estimated to result in 1 million illnesses, 46,000 hospitalizations, and 80 deaths each year among adults over 50 years of age in the United States, for a total societal cost of $2.4 billion. In comparison, norovirus results in 22 million illnesses, 96,000 hospitalizations, and 1,350 deaths each year among all age groups in the United States, for a total societal cost of $10 billion.

Burden in older adults

Adults older than 65 are another high-risk group for norovirus infections. In the United States, older adults are estimated to account for 17% of illnesses due to norovirus yet comprise 52% of hospitalizations and 94% of deaths. Symptoms are often more severe in this age group and include diarrhea lasting up to nine days and headache, thirst, and vertigo lasting up to 19 days. Older adults are also more likely to be found in certain settings vulnerable to norovirus outbreaks. Long-term care facilities (LTCFs) are the most commonly reported location for norovirus outbreaks, with an estimated 8 – 17% of LTCFs experiencing an outbreak each year. Hospitals are another common setting for norovirus outbreaks. After admittance to a hospital, older adults are more likely to acquire a norovirus infection than younger hospitalized patients. In the United States, norovirus is estimated to result in 3.7 million illnesses, 380,000 outpatient visits, 50,000 hospitalizations, and 1,250 deaths annually for adults over 65. Globally, norovirus is estimated to result in 81 million illnesses and 78,000 deaths annually for adults older than 55.

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Burden in other high-risk groups

In addition to young children and older adults, there are other groups that are at high risk for norovirus infection. These include healthcare workers, immunocompromised individuals, military personnel, food handlers, and travelers, including cruise ship passengers. More than 100 outbreaks of norovirus have been described in military units since 1988, reducing operational effectiveness and staff availability for duties. Food handlers are another source of concern. Given the small amount of virus needed for infection, a single individual can be responsible for widespread virus transmission. For example, a norovirus outbreak in 2006 resulting in at least 350 gastroenteritis cases was linked to a single food handler. Another series of high-profile outbreaks occurred at Chipotle restaurants between 2015 and 2018, where 1,100 patrons fell ill after eating at various locations of the chain restaurant. This outbreak resulted in the largest fine in food safety in U.S. history. Travelers are another high-risk group, with more than 20% of travelers with diarrheal symptoms testing positive for norovirus. Cruise ships present a high risk of norovirus outbreaks due to their ideal conditions for transmission: common sources for food and drinks, a semi-closed environment, and older adult passengers that may be more vulnerable to infections and complications arising from gastroenteritis. Outbreaks on cruise ships can be quite severe with infection rates for passengers ranging from 19% to 74%. The CDC reported 84 outbreaks of norovirus on cruise ships between 2010 and 2019.

Our solution: HIL-214

HIL-214 is a bivalent vaccine candidate in development for the prevention of moderate-to-severe AGE caused by norovirus infection. HIL-214 consists of VLPs which are designed to mimic the structure of norovirus and are co-formulated with an alum adjuvant to enhance immunogenicity and stability of the VLPs in solution. HIL-214 is administered intramuscularly via prefilled syringes and has demonstrated stability at standard refrigeration temperatures of 4°C for at least 24 months.

VLP technology

VLPs are self-assembling structures that mimic the unique and repetitive geometric features that characterize the surface of a live virus. VLPs can be produced using a common range of expression systems, including bacterial, mammalian, or insect cells, and can present a conformationally correct representation of the virus capsid to the immune system. As a result, VLPs can be readily manufactured in cell culture at large scale and offer a highly immunogenic vaccine template. Importantly, VLPs lack a viral genome and can therefore neither replicate nor cause infection, which may provide an important safety advantage over live vaccines.

There is ample precedent for the development of safe and effective vaccines that leverage VLP technology. Gardasil, a commercially available vaccine for human papillomavirus (HPV) developed by Merck, consists of recombinant VLPs self-assembled from the capsid protein of HPV types 6, 11, 16, and 18. A subsequent iteration of the product, known as Gardasil9, added five additional VLPs to its formulation to cover HPV types 31, 33, 45, 52, and 58. Other commercially available VLP vaccines include Cervarix, an HPV vaccine manufactured by GlaxoSmithKline, and Sci-B-Vac, an HBV vaccine developed by VBI Vaccines. There are also a number of VLP vaccines in clinical development for H1N1, HIV, malaria, respiratory syncytial virus, human metapneumovirus, and COVID-19, among other indications. Vaccines that employ VLP technology have been given to millions of patients worldwide.

HIL-214 construct

HIL-214 includes VLPs representing the two genogroups of norovirus responsible for the majority of human infection: GI and GII. Our G1.1 Norwalk VLP was selected based on its potential to promote a broad immune response to GI norovirus strains. In an independent study, infection of human volunteers with GI.1 Norwalk virus

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resulted in a broad antibody response against GI.1, GI.2, GI.3, and GI.4 strains. Our GII.4 VLP is a consensus sequence of three GII.4 strains that were responsible for major outbreaks in 2002 and 2006: GII.4 Houston/2002, GII.4 Yerseke/2006a, and GII.4 Den Haag/2006b. The GII.4 genotype accounts for two-thirds of norovirus outbreaks worldwide and its prevalence is attributed to its ability to rapidly evolve, with novel variants emerging every two to four years that may evade immunity in the human population. We believe that presenting epitopes from three GII.4 strains on our GII.4 VLP will result in a broader response to GII.4 strains than a VLP presenting a single strain. Sera from subjects vaccinated with HIL-214 have been shown to generate antibody titers against a broad range of GI and GII norovirus genogroups. Specifically, HIL-214 resulted in a greater than fourfold rise in antibodies against multiple GI strains (GI.1, GI.5, GI.6) and GII.4 strains (2002, 2006a, 2006b, 2009, 2012). The observation that HIL-214 induced antibodies against GII.4 strains that have emerged after the formulation of our vaccine candidate (GII.4 New Orleans 2009 and GII.4 Sydney 2012) suggests that our GII.4 VLP may protect against newly emerging strains in the future.

HIL-214 also includes alum as an adjuvant. Alum is the predominant adjuvant used in human vaccines and is a common component of several pediatric vaccines, including those for pneumococcus, diphtheria-tetanus-pertussis (DTaP), Hepatitis A, Hepatitis B and HPV.

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HIL-214 clinical data

Overview

HIL-214 has been the subject of nine Phase 1 and Phase 2 clinical trials, including more than 4,500 subjects of which more than 2,200 subjects have been evaluated for immunogenicity. These subjects have ranged from 6 weeks to 102 years old. An overview of the clinical trials conducted to date by Takeda and its predecessor, LigoCyte Pharmaceuticals, Inc., is tabulated below:

Dose finding and formulation trials in infants and children

A Phase 2 dose finding and formulation trial has been conducted in infants and children for HIL-214. Based on the results from this trial, in addition to considerations around disease burden and maternal antibody concentrations, we have selected the following dose and schedule to continue to evaluate HIL-214 in infants: two doses of 50/150 µg GI.1/GII.4 with 500 µg alum given at approximately 5 months of age at the time of the first dose. Further details on this trial are summarized below.

NOR-202—A Phase 2 safety, immunogenicity, and dose finding trial of HIL-214 in infants and children between the ages of 6 weeks and 9 years old. The trial enrolled 840 subjects in Colombia, Panama, and Finland into two cohorts. The first cohort was aged 6 months to 9 years old and received one or two doses of one of four potential HIL-214 formulations containing either 15/15, 15/50, 50/50, or 50/150 µg of the GI.1/GII.4 VLP combination and 500 µg of alum at least 28 days apart. The second cohort was aged 6 weeks to 6 months old and received two or three doses of one of the four potential HIL-214 formulations. All dosages of HIL-214 were generally well tolerated with no AEs related to HIL-214 leading to study withdrawal. All HIL-214 formulations were found to be immunogenic in each pediatric age group as measured by HBGA blocking titers. In children between 6 weeks and 6 months of age, both the two- and three-dose regimens of the 50/150 µg formulation of HIL-214 were found to be immunogenic. In children between 6 and 12 months of age, two doses of the 50/150 µg formulation of HIL-214 were found to be more immunogenic than one dose.

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Dose finding and formulation trials in adults

Four dose finding and formulation trials have been conducted in adults for HIL-214. Based on the results of these trials, we selected a single dose of 15/50 µg GI.1/GII.4 VLP combination with 500 µg alum to continue to evaluate HIL-214 in adults. Further details on these trials are summarized below.

LV03-104—A Phase 1, randomized, double-blind, placebo-controlled age- and dose-escalation trial to evaluate the safety and immunogenicity of HIL-214 or saline placebo in 102 adults aged 18 to 85 years old. Forty-eight subjects aged 18 to 49 years old received either two doses of HIL-214 containing GI.1 and GII.4 VLPs (5, 15, 50, or 150 µg of each VLP) or two doses of placebo administered 4 weeks apart. Subsequently, 54 adults aged 18 to 85 years old received two doses of HIL-214 containing 50 µg of each VLP. At all tested dose levels, the vaccine was generally well tolerated and immunogenic as measured by pan-IG, class-specific IgG, and HBGA blocking titers. One dose of vaccine containing 50 µg of each VLP increased GI.1 antibody levels by 118-fold and GII.4 antibody levels by 49-fold in subjects aged 18 to 49 years old. Local reactions were mainly tenderness (71%) and injection site pain (68%) in the 66 subjects who received HIL-214, with no reported fever or vaccine-related serious AEs. A second dose at day 28 provided no apparent improvement in immunogenicity across any of the age groups. The sample size was chosen to obtain indications of safety, reactogenicity, and immune response data but was not powered for statistical significance.

NOR-107—A Phase 2, randomized, double-blind trial to evaluate the safety, immunogenicity, dose, and adjuvant justification of HIL-214 in 420 healthy adults aged 18 to 64 years old. One or two doses of HIL-214 were administered 28 days apart in a factorial design testing combination of 15, 50 or 150 µg of each VLP with 0, 15 or 50 µg of monophosphoryl lipid A (MPL) and 167 or 500 µg of alum. For subjects receiving a single dose of HIL-214, a hepatitis A vaccine (Havrix) was given as a control to maintain the blinding. The trial demonstrated that the adjuvant MPL did not significantly improve immunogenicity, and that seroresponse rates (the percentage of subjects with a greater than four-fold rise in antibody levels) were greater with 500 µg of alum than with 167 µg of alum. The most common AEs were injection site pain (46%), headache (18%), and fatigue (14%) in the 420 subjects studied, with no vaccine-related serious AEs reported. The study also showed that a

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second dose of the 15/50 µg GI.1/GII.4 formulation provided no apparent improvement in immunogenicity. This study was powered for statistical significance.

NOR-201—A Phase 2, randomized, double-blind trial to evaluate the safety and immunogenicity of HIL-214 in 454 adults aged 18 to 49 years old. Enrolled subjects were randomly assigned among three groups receiving one dose of saline placebo or HIL-214 containing either 15/50 or 50/50 µg GI.1/GII.4 VLP combinations adjuvanted with 50 µg of MPL and 500 µg of alum. Both HIL-214 formulations were well tolerated and immunogenic, although GII.4 responses were higher with the 15/50 VLP combination (although the difference did not reach statistical significance). The most common AEs were pain near the injection site (69%) and muscle pain (22%) in the 299 subjects who received HIL-214, with no vaccine-related serious AEs reported. The results from this trial suggest that the 15/50 µg dose may be the optimal formulation to evaluate in adults. The sample size was chosen to provide a clinical database to support initiation of larger Phase 2 and 3 studies but was not powered for statistical significance.

NOR-204—A Phase 2, randomized, double-blind trial to evaluate the safety, immunogenicity, dose formulation, and dose regimen of HIL-214 in 320 healthy adults aged 18 to over 85 years old. Older adults were stratified into three groups of 60-74 years, 75-84 years and greater than 85 years. A cohort of younger adults of 18 to 49 years was enrolled for comparison. One or two doses of HIL-214 were administered in a 15/50 µg GI.1/GII.4 VLP combination adjuvanted with 500 µg alum with or without 50 µg of MPL. For subjects receiving a single dose of HIL-214, a saline placebo was given as a control to maintain the blinding. The most common AEs were injection site pain (33%) and fatigue (12%) in the 73 subjects studied, with no vaccine-related serious AEs reported. The results of this trial suggest that there was no statistically significant benefit of either MPL or a second dose on immunogenicity, and further, suggested that the formulation of 15/50 µg GI.1/GII.4 VLP combination and 500 µg alum may be the optimal formulation to evaluate in adults. The trial also found that the antibody response in each of the older age groups was similar to that in the young adult age group. This study was powered for statistical significance.

Efficacy trials in adults

Proof-of-concept of the efficacy of HIL-214 in adults has been demonstrated across three clinical trials: two Phase 1/2 challenge trials and a Phase 2b field efficacy trial. Further details on these trials are summarized below.

Challenge trial (LV01-103)—A Phase 1/2, randomized, double-blind, placebo-controlled trial to evaluate the efficacy of an intranasal GI.1 VLP vaccine candidate after challenge with a live, vaccine-matched GI.1 norovirus strain in 98 healthy adults aged 18 and 50 years old. The vaccine formulation used in the trial contained 100 µg of GI.1 VLP and was adjuvanted with chitosan and MPL. Subjects were randomized to receive either two doses of saline placebo or GI.1 vaccine delivered intranasally three weeks apart. Subjects were then challenged with a live GI.1 virus to test the effect of vaccination on norovirus infection and disease. Vaccination significantly reduced the frequency of GI.1 infection (occurring in 61% in vaccine recipients vs. 82% in placebo recipients, p = 0.05). Vaccination also significantly reduced the frequency of GI.1 virus gastroenteritis (occurring in 37% of vaccine recipients vs. 69% of placebo recipients, p = 0.006). Furthermore, disease severity was significantly reduced as measured by modified Vesikari score, which is a validated common metric for rating the severity of gastroenteritis symptoms based on a scale of 20 (3.6 for vaccine recipients vs. 5.5 for placebo recipients, p = 0.009).

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A p-value is the probability that the reported result was achieved purely by chance, such that a p-value of less than or equal to 0.05 means that there is a less than or equal to 5% probability that the difference between the control group and the treatment group is purely due to chance. A p-value of 0.05 or less typically represents a statistically significant result. The United States Food and Drug Administration’s (FDA’s) evidentiary standard when evaluating the results of a clinical trial generally relies on a p-value of less than or equal to 0.05.

Challenge trial (LV03-105)—A Phase 1/2, randomized, double-blind, placebo-controlled trial to evaluate the efficacy of HIL-214 after challenge with a live, GII.4 norovirus strain. The HIL-214 formulation used in the trial contained a 50/50 µg ratio of GI.1 and GII.4 VLPs and was adjuvanted with 500 µg of alum and 50 µg MPL. Subjects were between 18 and 50 years of age and received two doses of either saline placebo or GI.1/GII.4 vaccine intramuscularly four weeks apart. Subjects were then challenged with a live GII.4 virus to test the effect of vaccination on norovirus infection or disease. HIL-214 led to a significant reduction in the severity of vomiting or diarrhea by subject assessment (20% in vaccine recipients vs. 42% in placebo recipients, p = 0.028). HIL-214 also led to a significant reduction in disease severity as measured by modified Vesikari score (4.5 in vaccine recipients vs. 7.3 in placebo recipients, p = 0.002). The results of this trial showed a directional, albeit not statistically significant, reduction in frequency of AGE (26% vs. 33%) and infection (54% vs. 63%) for the HIL-214 group relative to the placebo group after challenge. We believe the lack of statistical significance was potentially due to a lower than expected infection and illness rate; only 57 of the 98 subjects were successfully infected with norovirus which lowered the statistical power for the study.

Field efficacy trial (NOR-211)—A Phase 2b, randomized, double-blind, placebo-controlled trial to evaluate the efficacy of HIL-214 to prevent norovirus infection and moderate-to-severe AGE in the field setting. The trial was conducted in U.S. military recruits at a single base in Great Lakes, Illinois over the course of two winter seasons (2016 – 2018). In total, 4,712 subjects aged 18-49 years old were enrolled in the trial and received one dose of either saline placebo or HIL-214 (15/50 µg of GI.1/GII.4 with 500 µg of alum as an adjuvant). The primary

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endpoint of the NOR-211 trial was the efficacy of a single dose of HIL-214 compared to placebo to prevent cases of moderate to severe AGE due to infection by genotype matched norovirus strains represented in the vaccine (i.e., GI.1 or GII.4). The low attack rate of norovirus strains represented in the vaccine resulted in insufficient cases to assess the primary endpoint. Thirty vaccine-matched AGE cases were required to provide 80% statistical power to detect 70% vaccine efficacy; however, only 6 vaccine-matched cases occurred during the trial. Of those 6 cases, 5 were in the placebo group, corresponding to 80% vaccine efficacy for genotype matched cases of AGE (p=0.1417).

On account of this lower than anticipated attack rate of GI.1 and GII.4, the statistical analysis plan was amended prior to locking the database and unblinding the trial. While only 6 vaccine-matched AGE cases caused by GII.4 were observed, a total of 36 AGE cases caused by any norovirus genotype was observed, which was a sufficient number to evaluate the secondary endpoint of HIL-214 against moderate-to-severe AGE due to norovirus infection irrespective of genotype. Of those 36 cases, 26 were in the placebo group, corresponding to 62% vaccine efficacy (p = 0.0097) for any norovirus genotype, including those not included in HIL-214. In sum, this trial provided statistically significant evidence of heterotypic protection against at least one non-vaccine norovirus strain (GII.2). This trial also provided encouraging evidence of protection against vaccine-matched strains.

One potential explanation for the cross-protection observed in this trial is that HIL-214 may have induced cross-reactive antibodies against GII.2 viruses (evidence of heterotypic protection). In support of this hypothesis, HIL-214 was found to induce both binding and HBGA-blocking antibodies against GII.2 VLPs.

Safety results in infants and children

Safety data for HIL-214 in infants and children were collected for over 800 subjects in NOR-202, a Phase 2 safety, immunogenicity and dose finding trial. This trial demonstrated that all doses of HIL-214 were well tolerated, and there were no HIL-214-related AEs leading to trial withdrawal. AEs were largely mild to moderate in intensity and tended to subside in 3 to 4 days. In children between 6 weeks to 6 months of age who received two doses of HIL-214, the most common reactions were irritability / fussiness (19—28%), drowsiness (16—21%), pain near the injection site (9—21%), and diarrhea (10—19%) in the 180 subjects studied. In children between 6 months and 9 years of age who received two doses of HIL-214, the most common reactions were pain near the injection site (21—33%), fatigue (16—24%), headache (14—21%), and irritability / fussiness (10—20%) in the 238 subjects studied. A comparison of the reactogenicity of HIL-214 to other common pediatric vaccinations is tabulated below. These data are presented for informational purposes only, as the comparison in the table below is not based on head-to-head clinical studies and these data may not be comparable due to differences in vaccine design, disease under evaluation, trial designs and subject characteristics.

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Safety in adults

Safety data for HIL-214 in adults have been collected for over 4,000 subjects across seven clinical trials. These trials have demonstrated that HIL-214 was well tolerated, and there were no HIL-214-related AEs leading to trial withdrawal. In the NOR-211 field efficacy trial of military recruits, the most common reaction was pain near the injection site with a mean duration of 2 days (48% for HIL-214 vs. 38% for placebo) in a safety subset of 377 subjects. Systemic AEs were found to occur at a similar rate to placebo (56% for HIL-214 vs. 60% for placebo).

Safety data for HIL-214 in older adults (>60 years old) have also been collected for 294 subjects in NOR-204, a Phase 2 safety, immunogenicity, and dose finding trial. This study found that local AEs were mostly mild in intensity and injection-site pain was the most frequently reported symptom. In addition to these completed trials, a Phase 2 trial is currently ongoing to evaluate the long-term safety and immunogenicity of HIL-214 in 528 subjects between 18 and 85 years of age up to 5 years post vaccination (NOR-213). Interim data from this study have shown no vaccine-related serious AEs reported and maintenance of antibody levels above baseline at 3 years post vaccination. A comparison of the reactogenicity of HIL-214 to other common adult vaccinations is tabulated below. These data are presented for informational purposes only, as the comparison in the table below is not based on head-to-head clinical studies and these data may not be comparable due to differences in vaccine design, disease under evaluation, trial designs, and subject characteristics.

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Our clinical program in infants

Phase 2b infant efficacy trial

We plan to build on the extensive clinical data generated to date by initiating our next clinical trial in infants. We believe that initial development of HIL-214 in infants will de-risk its development given the endemic nature of disease in this population, which allows for rapid case accrual and enrollment of subjects without pre-existing immunity to norovirus.

This clinical trial will be a Phase 2b, randomized, double-blind, placebo-controlled trial to evaluate the efficacy, safety, and immunogenicity of HIL-214 in infants of approximately 5 months of age at time of initial vaccination at sites in the United States and Latin America. We believe 5 months of age is the optimum time to begin immunization as it is prior to the sharp increase in incidence of norovirus that begins at 6 months of age and coincides with the waning of maternal antibodies to norovirus. We plan to enroll 3,000 subjects (irrespective of FUT2 secretor status) who will be randomized 1:1 to receive either HIL-214 or placebo. In the vaccine arm, subjects will receive HIL-214 (50/150 µg GI.1/GII.4 VLP combination with 500 µg alum) in a two-dose regimen delivered 28 to 56 days apart. In the control arm, subjects will receive saline placebo at the corresponding timepoints. The dosage and scheduling were based on learnings from the NOR-202 Phase 2 trial. We expect that the primary objective of the trial will be to evaluate the protective efficacy of HIL-214 against the first confirmed moderate or severe AGE event due to GI.1 or GII.4 norovirus strains (excluding certain co-infections) that occurs prior to each subject reaching 12 months of age. Key secondary endpoints may include evaluation of the protective efficacy of HIL-214 against any GI or GII norovirus strain. We plan to conduct a pre-specified safety and immunogenicity analysis on the first 200 subjects.

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We are developing and qualifying a number of clinical assays to support the determination of our primary and secondary endpoints. These include an assay to detect norovirus in stool samples and determine norovirus genogroup (e.g., GI or GII), a sequencing assay to determine norovirus genotype (e.g., GI.1 or GII.4), and a co-pathogen assay to detect other pathogens that may cause AGE (e.g., rotavirus or Salmonella). The immunogenicity of HIL-214 will be evaluated using assays that measure HBGA-blocking antibody titers and pan-Ig antibody titers. We have designed our planned Phase 2b clinical trial based on learnings from the NOR-211 Phase 2b study and the NOR-202 Phase 2 study, as well as preliminary feedback Takeda received from the FDA and European Medicines Agency (EMA). We expect to report interim safety data for the first 200 subjects in the second half of 2022, interim immunogenicity data for the first 200 subjects in the first half of 2023, and top-line results from the full Phase 2b trial in the second half of 2023.

Phase 3 infant efficacy trial

Based on the results from our planned Phase 2b trial, if positive, we plan to interact with key regulatory authorities and initiate a Phase 3, randomized, double-blind, placebo-controlled trial to evaluate the efficacy, safety, and immunogenicity of HIL-214 in a larger clinical trial. We expect that this trial will enroll approximately 5,000 to 6,000 subjects that will be randomized 1:1 into the vaccine or control arm. Trial sites under consideration include those located in the United States, Latin America, Europe, and Japan.

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Other trials in infants

We are planning additional trials in infants to support regulatory submissions and the potential co-administration of HIL-214 with common pediatric vaccines. These potentially include a Phase 3 trial to evaluate the safety and immunogenicity of HIL-214 when co-administered with other routine pediatric vaccines and a Phase 3 trial to evaluate lot-to-lot consistency of HIL-214. We believe that successful completion of this clinical program in infants, together with existing clinical data, will support regulatory submissions for marketing approval in most territories of the world, including the United States, Europe, Japan, and Latin America.

Our immunobridging strategy to other age groups

Overview

If we are successful in obtaining approval for HIL-214 in infants, we plan to subsequently seek approval of HIL-214 in additional age groups, including older children and adolescents (2 to 17 years of age), adults (18 to 59 years of age), and older adults (60 years of age and older). Our preferred strategic approach for seeking approval in these populations is through conducting immunobridging trials, which aim to demonstrate non-inferiority of immune response between a reference age group (i.e., infants) and target age groups. These trials require an appropriate serological surrogate for efficacy and can potentially support regulatory submissions seeking approval to expand to these other age groups without the need for an efficacy trial. Key requirements for an immunobridging strategy include:

We believe the most likely serological surrogate will be blocking antibodies to HBGAs, which have previously been shown to correlate with protection against norovirus. We are planning to collect HBGA-blocking titers for all subjects in our planned Phase 2b and Phase 3 infant efficacy trials to use as a reference for immunobridging to other age groups. In addition to HBGA-blocking antibodies, we are also exploring the measurement of other immune parameters that may be reasonably likely to predict protection.

If we are not able to confirm an appropriate serological surrogate in our planed infant efficacy trials, or if the FDA or EMA do agree with our proposed immunobridging strategy, we plan to directly evaluate HIL-214 for efficacy in older adults (65 years of age and older). We would plan to conduct this trial across multiple sites at high-risk for norovirus outbreaks, including nursing homes, assisted living facilities, and other older adult communities.

Historical precedent for immunobridging

A number of vaccines have successfully used immunobridging to expand the approval of a vaccine to those in other age groups, without conducting further efficacy studies, including Boostrix, Gardasil, Cervarix, and Vaxchora. For example, Boostrix used a prior infant efficacy study to bridge to older subjects and included the use of a different vaccine strength and regimen in infants and older age groups. This immunobridging strategy

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was based on demonstrating non-inferiority of pertussis antigen seroresponses in adolescents (10 to 18 years of age), adults (19 to 64 years of age), and older adults (65 years of age and older) to prior infant responses in efficacy trials. Of particular note, this strategy was successful for Boostrix even in the absence of an established correlate of protection for pertussis.

HIL-214 commercial opportunity

The global vaccine market is estimated to have been over $50 billion in 2020 and is expected to exceed $100 billion by 2027. Pneumococcal vaccines have historically been the largest vaccine category, with $7 billion in sales in 2020. COVID-19 vaccines are expected to become the largest category in 2021. We believe that the increased attention given to infectious diseases during the COVID-19 pandemic, and the important role of vaccines in disease prevention, is likely to further increase the size of the global vaccine market.

There are currently no approved vaccines for the prevention of norovirus-related illness. However, there are market analogues that we believe we can use to estimate the size of the commercial opportunity for HIL-214. In the pediatric market, we believe that rotavirus vaccines are the closest analogue to HIL-214. Rotavirus was the leading cause of pediatric viral AGE before the introduction of the rotavirus vaccines, Rotarix and RotaTeq. These vaccines, approved only in infants, are now widely adopted worldwide, with many countries achieving vaccination rates above 80% among one-year-olds. Rotavirus vaccines generated more than $1.6 billion in sales in 2020. For comparison, norovirus today has a similar morbidity, mortality, and economic burden in children as rotavirus did before the introduction of rotavirus vaccines. When considering all age groups, the overall burden of norovirus is greater than that of rotavirus.

In the older adult market, we believe that Shingrix, a recombinant protein vaccine developed by GSK to prevent shingles, is an analogue for HIL-214 due to the similarities in morbidity, mortality and economic burden between shingles and norovirus each before the introduction of a vaccine. Shingrix generated $2.7 billion in sales in 2020. For comparison, norovirus today has a greater morbidity, mortality, and economic burden than shingles did before the introduction of shingles vaccines. Prior to shingles vaccines becoming available, shingles was estimated to result in 1 million illnesses, 46,000 hospitalizations, and 80 deaths each year among adults over 50 years of age in the United States, for a total societal cost of $2.4 billion. In contrast, norovirus results in 22 million illnesses, 96,000 hospitalizations, and 1,350 deaths each year among all age groups in the United States, for a total societal cost of $10 billion. Furthermore, we believe that there is a commercial opportunity for a norovirus vaccine in other groups at high risk for norovirus infection, such as healthcare workers, immunocompromised individuals, military personnel, food handlers, and travelers, including cruise ship passengers.

A key element of our commercial strategy is to receive advisory body recommendations for the use of HIL-214. In particular, we are focused on the ACIP, which is an advisory body of the CDC that develops vaccine recommendations for children and adults in the United States. New pediatric vaccines that received a preferred recommendation from ACIP are nearly universally adopted by pediatricians and are often required by schools. Rotavirus vaccines received an ACIP recommendation in 2006, which has contributed to their broad uptake in the United States. Following completion of our planned Phase 2b and 3 trials in infants, we expect ACIP to review these data with the goal of having ACIP recommend HIL-214 for routine pediatric use. We also plan to pursue an ACIP recommendation in the older adult population.

Competition

Our industry is characterized by rapidly advancing technologies, intense competition, and strong emphasis on proprietary products. According to EvaluatePharma, October, 2021, the current vaccine market is concentrated among a few global biopharmaceutical companies including BioNTech, CSL Bering, GlaxoSmithKline, Merck,

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Moderna, Pfizer, Sanofi, and Takeda, which together account for the majority of global vaccine sales. Other pharmaceutical and biotechnology companies, academic institutions, governmental agencies, and public and private research institutions are also active in the vaccine market given the continuing global need for both existing and new vaccines.

While we believe that our team, technology, strategy, and depth of clinical data relative to other products in clinical development provide us with a strong competitive advantage, if HIL-214 receives marketing approval, we will have to compete with new products and therapies that may become available in the future. The key competitive factors that will affect the success of HIL-214 are similar to those faced by other vaccine products: safety, immunogenicity, protective efficacy, duration of effect, convenience of administration, price, public health policy, and reimbursement by third-party payors.

There are currently no approved vaccines for the prevention of norovirus-related illness. While we are not aware of all of our competitors’ efforts, based on public statements, we believe that several companies are in various stages of developing a vaccine for norovirus including China National Biotec, Chongqing Zhifei Biological, Icon Genetics and Vaxart. We believe that China National Biotec, Chongqing Zhifei Biological and Icon Genetics are also focused on developing a vaccine consisting of VLPs representing the GI and GII genogroups of norovirus. Further, we believe that China National Biotec and Chongqing Zhifei Biological are also developing a pediatric vaccine for the prevention of norovirus-related illness. We believe that HIL-214 is well positioned to be the first norovirus vaccine approved in any market worldwide.

Manufacturing

We do not have, nor do we plan to establish, large-scale manufacturing facilities that are compliant with current Good Manufacturing Practices (cGMP). For our Phase 2b infant efficacy trial, we plan to use clinical material that was previously manufactured by Takeda. We plan to continue to use third-party manufacturers to produce cGMP material for our future clinical trials and commercial supply, if approved.

Intellectual property

Intellectual property, including patents, trade secrets, and trademarks, is important to our business. Our commercial success depends in part on our ability to obtain and maintain proprietary intellectual property protection for HIL-214, as well as for future vaccine candidates and novel discoveries, product development technologies, and know-how. Our commercial success also depends in part on our ability to operate without infringing, misappropriating or violating the intellectual property and proprietary rights of others and to prevent others from infringing, misappropriating or violating our intellectual property and proprietary rights. Our policy is to develop and maintain protection of our proprietary position by, among other methods, licensing or filing U.S. and foreign patents and applications relating to our technology, inventions, and improvements that are important to the development and implementation of our business.

Our patent portfolio, comprising patents and patent applications exclusively licensed to us, is built with a goal of establishing broad protection that generally includes, for the vaccine candidate compound, claims directed to composition of matter, pharmaceutical compositions or formulations, methods of synthesis, and methods of use of such pharmaceutical compositions or formulations. As of March 31, 2022, our patent portfolio covering HIL-214 consists solely of patents and patent applications exclusively licensed from Takeda. Subject to the terms of the Takeda License we entered into with Takeda on July 2, 2021, we have licensed from Takeda exclusive commercialization rights worldwide, excluding Japan, to patents and patent applications covering the composition of matter, formulation, use and/or manufacture of HIL-214. Our patent portfolio comprises 8 distinct patent families protecting the technology relating to HIL-214 composition of matter, methods of manufacturing HIL-214, formulations of HIL-214 products, as well as methods of use of HIL-214. As of

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March 31, 2022, our portfolio consists of approximately 22 issued U.S. patents, 5 pending U.S. patent applications, 65 issued foreign patents including 6 issued European patents subsequently validated in individual European countries, and 54 foreign patent applications pending in major international markets. The issued patents and pending applications have nominal expiration dates ranging from 2027 to 2039, without accounting for any available patent term adjustments or extensions.

More specifically, of the 8 distinct patent families, we have in-licensed two patent families relating to manufacturing methods for norovirus VLPs. One of these families contains four U.S. patents projected to expire from 2028 to 2029, as well as a granted patent in each of Canada, Hong Kong, Europe, Republic of Korea and Singapore and two granted patents in Australia, also projected to expire in 2028, in each case without accounting for any available patent term adjustments or extensions. The European patent in this family was validated in Belgium, Bulgaria, Switzerland, Czech Republic, Germany, Denmark, France, the United Kingdom, Hungary, Ireland, Netherlands, Poland and Sweden. There is an additional pending application in Singapore, projected to expire in 2028, without accounting for any available patent term adjustments or extensions.

The other patent family covering manufacturing methods contains two U.S. patents projected to expire from 2033 to 2035, as well as a granted patent in each of Australia, Europe, Hong Kong, Jordan, Lebanon, Republic of Korea, Mexico and Taiwan, all projected to expire in 2033, in each case without accounting for any available patent term adjustments or extensions. The European patent in this family was validated in Belgium, Switzerland, Czech Republic, Germany, France, the United Kingdom, Ireland and Netherlands. There are two additional pending patent applications in China and Argentina and an additional pending application in each of Bangladesh, Canada, Gulf Co-Operation Council, India, Iran, Pakistan, Singapore, Uruguay, Venezuela and the U.S., all projected to expire in 2033, in each case without accounting for any available patent term adjustments or extensions.

We have also in-licensed six patent families covering VLP compositions for HIL-214 and methods of use of HIL-214. One of these families contains seven U.S. patents, all projected to expire in 2027, as well as two granted patents in Europe, two granted patents in Hong Kong and a granted patent in each of Australia, Canada, Republic of Korea, Singapore, also projected to expire in 2027, in each case without accounting for any available patent term adjustments or extensions. One European patent in this family was validated in Austria, Belgium, Switzerland, Germany, Denmark, Spain, Finland, France, the United Kingdom, Greece, Ireland, Italy, Lithuania, Netherlands, Sweden and Turkey. A second European patent in this family was validated in Belgium, Bulgaria, Switzerland, Czech Republic, Germany, Denmark, Spain, Finland, France, the United Kingdom, Hungary, Ireland, Italy, Netherlands, Poland and Sweden. There is an additional pending application in Singapore, projected to expire in 2027, without accounting for any available patent term adjustments or extensions.

A second family covering VLP compositions and methods of use contains four U.S. patents projected to expire from 2027 to 2028, as well as two granted patents in each of Australia and China and a granted patent in each of Canada, Macau and Hong Kong, projected to expire from 2027 to 2028, in each case without accounting for any available patent term adjustments or extensions. There is an additional pending application in the U.S. and two in Singapore, projected to expire in 2028, in each case without accounting for any available patent term adjustments or extensions.

A third family covering VLP compositions and methods of use contains two U.S. patents projected to expire in 2029, as well as two granted patents in Republic of Korea and a granted patent in each of Australia, Canada, China, Macau, Europe, Hong Kong and Singapore, projected to expire in 2029, in each case without accounting for any available patent term adjustments or extensions. The European patent in this family was validated in Austria, Belgium, Denmark, Finland, France, Germany, Ireland, Italy, Netherlands, Norway, Poland, Spain, Sweden, Switzerland, Turkey and the United Kingdom. There is an additional pending application in each of

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China, Europe and Hong Kong, all projected to expire in 2029, in each case without accounting for any available patent term adjustments or extensions.

A fourth family covering VLP compositions and methods of use contains three US patents projected to expire in 2032, as well as two granted patents in Australia, Eurasia, Mexico, New Zealand, Philippines and South Africa and a granted patent in each of Canada, Chile, Europe, Georgia, Hong Kong, Israel, India, Republic of Korea, Morocco, Malaysia, Peru, Tunisia, Ukraine and Vietnam, also projected to expire in 2032, in each case without accounting for any available patent term adjustments or extensions. The European patent in this family was validated in Austria, Belgium, Switzerland, Germany, Spain, France, the United Kingdom, Italy, Netherlands, Poland and Sweden. There are two additional pending applications in China and Dominican Republic and an additional pending application in each of Algeria, Brazil, Costa Rica, Ecuador, Egypt, Europe, Eurasia, Hong Kong, Indonesia, Philippines, Singapore, Thailand, United States and Uzbekistan, all projected to expire in 2032, in each case without accounting for any available patent term adjustments or extensions.

A fifth family covering VLP compositions and methods of use contains a U.S. patent application projected to expire in 2039, without accounting for any available patent term adjustments or extensions. There is a pending application in each of Argentina, Australia, Brazil, Canada, China, Colombia, Europe, Indonesia, Israel, India, Republic of Korea, Mexico, Malaysia, New Zealand, Singapore and Thailand, all projected to expire in 2039, in each case without accounting for any available patent term adjustments or extensions.

A sixth family covering VLP compositions and methods of use contains a U.S. patent application projected to expire in 2039, without accounting for any available patent term adjustments or extensions. There is an additional pending application in Europe, projected to expire in 2039, without accounting for any available patent term adjustments or extensions.

The term of individual patents in our portfolio depends upon the legal term of patents in the countries in which they are obtained. In most countries in which we file, including the United States, the patent term is 20 years from the earliest date of filing a non-provisional patent application. In the United States, the term of a patent may be eligible for patent term adjustment, which permits patent term restoration as compensation for delays incurred at the USPTO during the patent prosecution process. In addition, for patents that cover an FDA-approved drug, the Drug Price Competition and Patent Term Restoration Act of 1984, or the Hatch-Waxman Amendments, permits a patent term extension of up to five years beyond the expiration of the patent. While the length of the patent term extension is related to the length of time the drug is under regulatory review, patent term extension cannot extend the remaining term of a patent beyond a total of 14 years from the date of product approval, only one patent per approved drug may be extended, and only those claims covering the approved drug, a method for using it or a method for manufacturing it may be extended. Similar provisions are available in Europe and other foreign jurisdictions to extend the term of a patent that covers an approved drug. In the future, if and when our products receive FDA approval, we expect to apply for patent term extensions on patents covering those products. We plan to seek any available patent term extension to any issued patents we may be granted in any jurisdiction where such extensions are available; however, there is no guarantee that the applicable authorities, including the FDA in the United States, will agree with our assessment of whether such extensions should be granted, and if granted, the length of such extensions.

The patent positions of companies like ours are generally uncertain and involve complex legal and factual questions. The relevant patent laws and their interpretation outside of the United States is also uncertain. Changes in either the patent laws or their interpretation in the United States and other countries may diminish our ability to protect our technology or vaccine candidates and could affect the value of such intellectual property. In particular, our ability to stop third parties from making, using, selling, offering to sell or importing products that infringe, misappropriate or violate our intellectual property will depend in part on our success in obtaining and enforcing patent claims that cover our technology, inventions and improvements. We cannot

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guarantee that patents will be granted with respect to any of our licensed pending patent applications or with respect to any patent applications we may file in the future, nor can we be sure that any patents that may be granted to us or Takeda in the future will be commercially useful in protecting our products or the methods of use or manufacture of those products. Moreover, issued patents do not guarantee the right to practice our technology in relation to the commercialization of our products. Issued patents only allow us to block potential competitors from practicing the claimed inventions of the issued patents.

Further, patents and other intellectual property rights in the pharmaceutical and biotechnology space are evolving and involve many risks and uncertainties. For example, third parties may have blocking patents that could be used to prevent us from commercializing HIL-214 and any future vaccine candidates and practicing our proprietary technology, and any issued patents may be challenged, invalidated or circumvented, which could limit our ability to stop competitors from marketing related products or could limit the term of patent protection that otherwise may exist for HIL-214 and any future vaccine candidates. In addition, the scope of the rights granted under any issued patents may not provide us with protection or competitive advantages against competitors with similar technology. Furthermore, our competitors may independently develop similar technologies that are outside the scope of the rights granted under any issued patents. For these reasons, we may face competition with respect to HIL-214 and any future vaccine candidates. Moreover, because of the extensive time required for development, testing and regulatory review of a potential product, it is possible that, before any particular vaccine candidate can be commercialized, any patent protection for such product may expire or remain in force for only a short period following commercialization, thereby reducing the commercial advantage the patent provides.

It is our policy to require our employees, consultants, outside scientific collaborators, sponsored researchers and other advisors to execute confidentiality agreements upon the commencement of employment or consulting relationships with us, and for employees and consultants to enter into invention assignment agreements with us. These agreements provide that all confidential information developed or made known to the individual during the course of the individual’s relationship with us is to be kept confidential and not disclosed to third parties except in specific circumstances. Where applicable, the agreements provide that all inventions to which the individual contributed as an inventor shall be assigned to Hillevax, and as such, will become our property. There can be no assurance, however, that these agreements will provide meaningful protection or adequate remedies for our trade secrets in the event of unauthorized use or disclosure of such information. For information regarding the risks related to intellectual property, see “Risk factors—Risks related to our intellectual property.”

Further, we have filed for three trademark applications in the United States for the HilleVax trademark and logo.

License agreement with Takeda

On July 2, 2021, we and Takeda entered into the Takeda License. Pursuant to the Takeda License, Takeda granted us: (a) an exclusive, royalty-bearing, sublicensable (with Takeda’s reasonable consent) license under (1) certain patents and know-how relating to HIL-214 (formerly TAK-214), and owned or controlled by Takeda during the term of the Takeda License and (2) Takeda’s rights in intellectual property jointly created by the parties under the Takeda License (the Joint Intellectual Property), in each case, to commercialize for all human uses worldwide outside of Japan (the Territory) any pharmaceutical products (the Products) containing the HIL-214 compounds and any derivatives thereof to prevent or minimize disease and/or infections caused by norovirus (the Compounds), and (b) a worldwide, non-exclusive, sublicensable (with Takeda’s reasonable consent) license under such patents and know-how to develop and manufacture the Compounds and Products solely to: (1) exploit the Compounds and Products in the Territory, (2) perform certain development activities in

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Japan, and (3) supply the Product to Takeda pursuant to any clinical supply or commercial supply agreement. We granted Takeda: (a) a non-exclusive, fully paid-up, royalty-free, sublicensable license under our rights in any patents and know-how and our rights in the Joint Intellectual Property that are necessary or useful to enable Takeda to develop and manufacture the Compounds and Products anywhere in the world for the purposes of commercialization of the Products in Japan, (b) an exclusive, royalty-bearing, sublicensable license under such patents and know-how to (1) commercialize Products in Japan and (2) commercialize Products for purposes other than for use in humans, and (c) an exclusive, sublicensable license to use Product trademarks solely for commercialization of a Product for human uses in Japan. Certain rights granted to us under the Takeda License are subject to rights granted by Takeda to the United States government pursuant to sponsored research, clinical development and material transfer agreements.

If, other than due to force majeure or our failure to perform our obligations under the Takeda License, Takeda fails to pursue regulatory or commercialization activities by specified deadlines, and does not dispute such failure or initiate such activities by a specified deadline, then the Territory may be expanded to include Japan (i.e., worldwide). During the term of the Takeda License, neither party is permitted to commercialize any vaccine product (other than the Product) that includes norovirus virus-like particles and is being developed for or is approved for the prevention or minimization of symptoms caused by norovirus infections without the other party’s prior written consent. We will be responsible, at our cost, for the development, manufacture and commercialization of the Product in the Territory. We are obligated to use commercially reasonable efforts to develop and commercialize the Product in the Territory, and to seek regulatory approval for the Product throughout the world.

We paid Takeda upfront consideration consisting of 500,000 shares of common stock and a warrant to purchase 3,500,000 shares of common stock (the Takeda Warrant). We further agreed that, in the event that Takeda’s fully-diluted ownership, including the Takeda Warrant, represents less a certain specified percentage of our fully-diluted capitalization, including shares issuable upon conversion of outstanding convertible promissory notes, calculated immediately prior to the closing of this offering, we will issue an additional warrant to purchase shares of common stock such that Takeda would hold a certain specified percentage of the fully-diluted capitalization immediately before the closing of this offering (the Takeda Warrant Right). We also paid Takeda a cash payment of $2.5 million upon the consummation of our convertible promissory note financing in August 2021 and are obligated to pay an additional cash payment of $2.5 million upon release of certain drug product and completion of certain regulatory activities. We are required to make to Takeda a one-time payment of $7.5 million upon achievement of a specified development milestone and one-time commercial milestone payments of up to $150.0 million in the aggregate if certain annual sales targets for Products are met in the Territory. We agreed to pay Takeda tiered high-single digit to low-teen percentage royalties on net sales of Products in the Territory, subject to specified offsets and reductions, and Takeda agreed to pay us tiered mid-single digit to low-double digit percentage royalties on net sales of Products in Japan, subject to specified offsets and reductions. Royalties will be payable, on a Product-by-Product and country-by-country basis beginning on the first commercial sale of such Product in such country, until the later of (i) the expiration of the licensed patents covering the applicable Product, (ii) the expiration of regulatory exclusivity in such country, or (iii) 20 years following the first commercial sale of such Product in such country.

Absent early termination, the Takeda License expires on a country-by-country and Product-by-Product basis upon the expiration of the applicable royalty term with respect to each Product in each country, as applicable, or in its entirety upon the expiration of the royalty term with respect to the last Product commercialized in the last country. We may terminate the Takeda License in its entirety without cause upon six months’ prior written notice. We and Takeda may terminate the Takeda License in the case of the other party’s insolvency, or upon prior written notice within a specified time period for the other party’s material uncured breach. Takeda may terminate the Takeda License in its entirety if we challenge the licensed patents, or if we assist any third party

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in challenging such patents. Upon termination of the Takeda License, Takeda will have an exclusive, transferable, fully paid-up, royalty-free, sublicensable license under the patents and know-how we license to Takeda under the Takeda License and our rights in the Joint Intellectual Property to exploit the Product in the terminated countries.

Transitional services agreement with Takeda

As contemplated by the Takeda License, on December 17, 2021, we and Takeda entered into a Transitional Services Agreement (the TSA). Pursuant to the TSA, Takeda has agreed to provide, on a transitional basis following the effective date of the Takeda License, certain services related to research and development and regulatory assistance services, oversight and management of ongoing clinical and research studies, and maintenance of certain third party vendor contracts. In consideration for the services provided under the TSA, we have agreed to pay certain specified amounts to Takeda in cash for such services and certain pass-through costs.

Unless earlier terminated under its terms, the TSA will remain in effect until all transitional services are completed. We may terminate the provision of any or all services under the TSA upon certain written notice. We and Takeda may terminate the TSA in the case of the other party’s insolvency, or upon prior written notice within a specified time period for the other party’s material uncured breach. Takeda may terminate the TSA for non-payment and, in certain circumstances, upon a change of control of our company.

Government regulation and product approval

The FDA and other regulatory authorities at federal, state, and local levels, as well as in foreign countries, extensively regulate, among other things, the research, development, testing, manufacture, quality control, import, export, safety, effectiveness, labeling, packaging, storage, distribution, record keeping, approval, advertising, promotion, marketing, post-approval monitoring, and post-approval reporting of biologics such as those we are developing. We, along with third-party contractors, will be required to navigate the various preclinical, clinical and commercial approval requirements of the regulatory agencies of the countries in which we wish to conduct studies or seek approval or licensure of our product candidates. The process of obtaining regulatory approvals and the subsequent compliance with applicable federal, state, local and foreign statutes and regulations require the expenditure of substantial time and financial resources.

U.S. biologics regulation