0000950170-22-016497 | 10-Q | XBRL Viewer

Document and Entity Information - shares	6 Months Ended
Document and Entity Information - shares	Jun. 30, 2022	Jul. 31, 2022
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2022
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q2
Entity Registrant Name	HILLEVAX, INC.
Entity Central Index Key	0001888012
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Small Business	true
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		33,427,209
Entity Interactive Data Current	Yes
Entity Current Reporting Status	Yes
Entity File Number	001-41365
Entity Tax Identification Number	85-0545060
Entity Address Address Line1	75 State Street
Entity Address, Address Line Two	Suite 100 - #9995
Entity Address City Or Town	Boston
Entity Address State Or Province	MA
Entity Address Postal Zip Code	02109
Entity Incorporation State Country Code	DE
City Area Code	617
Local Phone Number	213-5054
Title of each class	Common Stock, $0.0001 par value per share
Trading Symbol	HLVX
Name of each exchange on which registered	NASDAQ
Document Quarterly Report	true
Document Transition Report	false

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 314,612	$ 124,566
Prepaid expenses and other current assets (includes related party amounts of $692 and $0, respectively)	4,893	141
Total current assets	319,505	124,707
Property and equipment, net		42
Operating lease right-of-use assets	20,075	189
Restricted cash	1,631
Other assets	21	2,221
Total assets	341,232	127,159
Current liabilities:
Accounts payable (includes related party amounts of $1,645 and $22, respectively)	6,033	1,024
Accrued expenses (includes related party amounts of $757 and $4,911, respectively)	6,419	9,164
Accrued interest (includes related party amounts of $0 and $723, respectively)	23	2,821
Convertible promissory notes payable at fair value (includes related party amounts of $0 and $40,580, respectively)		158,276
Current portion of operating lease liability	35	32
Warrant liabilities - related party		56,445
Total current liabilities	12,510	227,762
Operating lease liability, net of current portion	20,790	153
Long-term debt, net of debt discount	4,697	0
Other long-term liabilities	81	1
Total liabilities	38,078	227,916
Commitments and contingencies (Note 3)
Stockholders' equity (deficit):
Preferred stock, $0.0001 par value; authorized shares-50,000,000 and 0 at June 30, 2022 and December 31, 2021, respectively; no shares issued and outstanding at June 30, 2022 and December 31, 2021
Common stock, $0.0001 par value; authorized shares- 500,000,000 and 50,000,000 at June 30, 2022 and December 31, 2021, respectively; issued shares-33,427,209 and 9,225,321 at June 30, 2022 and December 31, 2021, respectively; outstanding shares-31,311,387 and 6,599,886 at June 30, 2022 and December 31, 2021, respectively	3	1
Additional paid-in capital	530,151	4,426
Accumulated deficit	(227,000)	(105,184)
Total stockholders' equity (deficit)	303,154	(100,757)
Total liabilities and stockholders' equity (deficit)	$ 341,232	$ 127,159

Condensed Consolidated Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Operating expenses:
Research and development (includes related party amounts of $172, $0, $1,594 and $15, respectively)	$ 8,826	$ 460	$ 15,037	$ 727
In-process research and development			2,500
General and administrative (includes related party amounts of $8, $219, $34 and $384, respectively)	3,982	753	6,585	1,951
Total operating expenses	12,808	1,213	24,122	2,678
Loss from operating ,Total	(12,808)	(1,213)	(24,122)	(2,678)
Other income (expense):
Interest income	334		340
Interest expense (includes related party amounts of $188, $8, $717 and $17, respectively)	(888)	(8)	(2,952)	(17)
Change in fair value of convertible promissory notes (includes related party amounts of $8,818, $444, $13,196 and $517, respectively)	(34,396)	(444)	(51,469)	(517)
Change in fair value of warrant liabilities - related party	(6,151)		(43,575)
Other income (expense)	(20)	(2)	(38)	(1)
Total other income (expense)	(41,121)	(454)	(97,694)	(535)
Net loss	$ (53,929)	$ (1,667)	$ (121,816)	$ (3,213)
Net loss per share, basic	$ (2.03)	$ (0.34)	$ (7.30)	$ (0.66)
Net loss per share, diluted	$ (2.03)	$ (0.34)	$ (7.30)	$ (0.66)
Weighted-average shares of common stock outstanding, basic	26,512,881	4,935,738	16,685,372	4,869,690
Weighted-average shares of common stock outstanding, diluted	26,512,881	4,935,738	16,685,372	4,869,690

Condensed Consolidated Statements of Stockholders' Deficit (Unaudited) - USD ($) $ in Thousands	Total	Initial Public Offering	Common Stock	Common Stock Initial Public Offering	Additional Paid-in Capital	Additional Paid-in Capital Initial Public Offering	Accumulated Deficit
Beginning Balance at Dec. 31, 2020	$ (2,773)				$ 3		$ (2,776)
Beginning Balance, Shares at Dec. 31, 2020			4,759,968
Issuance of common stock, Shares			1,606,815
Vesting restrictions placed on previously issued and outstanding common stock	(1)				(1)
Vesting restrictions placed on previously issued and outstanding common stock, Shares			(2,332,386)
Vesting of restricted shares	1				1
Vesting of restricted shares, Shares			971,824
Net loss	(3,213)						(3,213)
Ending Balance at Jun. 30, 2021	(5,986)				3		(5,989)
Ending Balance, Shares at Jun. 30, 2021			5,006,221
Beginning Balance at Mar. 31, 2021	(4,320)				2		(4,322)
Beginning Balance, Shares at Mar. 31, 2021			4,860,449
Vesting of restricted shares	1				1
Vesting of restricted shares, Shares			145,772
Net loss	(1,667)						(1,667)
Ending Balance at Jun. 30, 2021	(5,986)				3		(5,989)
Ending Balance, Shares at Jun. 30, 2021			5,006,221
Beginning Balance at Dec. 31, 2021	(100,757)		$ 1		4,426		(105,184)
Beginning Balance, Shares at Dec. 31, 2021			6,599,886
Issuance of common stock		$ 209,515		$ 1		$ 209,514
Issuance of common stock, Shares				13,529,750
Conversion of August 2021 Notes and accrued interest into common shares	215,364		$ 1		215,363
Conversion of August 2021 Notes and accrued interest into common shares, Shares			10,672,138
Conversion of Takeda Warrant liability into equity	100,020				100,020
Vesting of restricted shares, Shares			509,613
Stock - based compensation	828				828
Net loss	(121,816)						(121,816)
Ending Balance at Jun. 30, 2022	303,154		$ 3		530,151		(227,000)
Ending Balance, Shares at Jun. 30, 2022			31,311,387
Beginning Balance at Mar. 31, 2022	(168,372)		$ 1		4,698		(173,071)
Beginning Balance, Shares at Mar. 31, 2022			6,897,450
Issuance of common stock		$ 209,515		$ 1		$ 209,514
Issuance of common stock, Shares				13,529,750
Conversion of August 2021 Notes and accrued interest into common shares	215,364		$ 1		215,363
Conversion of August 2021 Notes and accrued interest into common shares, Shares			10,672,138
Conversion of Takeda Warrant liability into equity	100,020				100,020
Vesting of restricted shares, Shares			212,049
Stock - based compensation	556				556
Net loss	(53,929)						(53,929)
Ending Balance at Jun. 30, 2022	$ 303,154		$ 3		$ 530,151		$ (227,000)
Ending Balance, Shares at Jun. 30, 2022			31,311,387

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Cash flows from operating activities
Net loss	$ (121,816)	$ (3,213)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation		1
Stock-based compensation	828
Change in fair value of convertible promissory notes (includes related party amounts of $13,196 and $517, respectively)	51,469	517
Change in fair value of warrant liabilities - related party	43,575
Amortization of debt discount	81
Issuance of PIK interest debt	21
Acquired in-process research and development	2,500
Loss on disposal of property and equipment	42
Changes in operating assets and liabilities:
Prepaid expenses and other current assets (includes related party amounts of $(692) and $41, respectively)	(4,750)	39
Accounts payable, accrued expenses and other long-term liabilities (includes related party amounts of $(2,531) and $(59), respectively)	550	1,103
Accrued interest (includes related party amounts of $717 and $17, respectively)	2,821	17
Operating lease right-of-use assets and liabilities	754
Net cash used in operating activities	(23,925)	(1,536)
Cash flows from investing activities
Cash paid for purchased in-process research and development	(2,500)
Purchase of property and equipment		(6)
Net cash used in investing activities	(2,500)	(6)
Cash flows from financing activities
Proceeds from issuance of common stock		1
Proceeds from issuance of common stock in initial public offering	230,006
Payment of initial public offering costs	(16,569)
Proceeds from issuance of long-term debt, net of issuance costs	4,665
Proceeds from issuance of convertible promissory notes		1,750
Net cash provided by financing activities	218,102	1,751
Net increase in cash, cash equivalents and restricted cash	191,677	209
Cash and, cash equivalents and restricted cash-beginning of period	124,566	457
Cash, cash equivalents and restricted cash-end of period	316,243	$ 666
Supplemental disclosure of cash flow information
Cash paid for interest	30
Supplemental disclosure of noncash investing and financing activities
Operating lease	20,317
Unpaid initial public offering costs	1,724
Conversion of convertible promissory notes and accrued interest into common stock	215,364
Conversion of warrant liability into equity	100,020
Accreted final interest payment fees	$ 70

Organization, Basis of Presentation and Summary of Significant Accounting Policies

6 Months Ended

Jun. 30, 2022

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Organization, Basis of Presentation and Summary of Significant Accounting Policies

1. Organization, Basis of Presentation and Summary of Significant Accounting Policies

Organization

HilleVax, Inc. (the “Company” or “HilleVax”) was incorporated in the state of Delaware in March 2020 under the name MokshaCo, Inc. (“MokshaCo”). On February 8, 2021, MokshaCo changed its name to HilleVax and merged with North Bridge V, Inc. (“North Bridge V”) and YamadaCo III, Inc. (“YamadaCo III”), each a Delaware corporation formed in 2019, with HilleVax being the surviving entity (the “Merger”). The Company is a biopharmaceutical company focused on developing and commercializing novel vaccines.

Forward Stock Split

On April 22, 2022, the Company effected a 1.681-for-1 forward split of shares of the Company’s common stock (the “Forward Stock Split”). The par value of the common stock was not adjusted as a result of the Forward Stock Split and the authorized shares were increased to 50,000,000 shares of common stock in connection with the Forward Stock Split. The accompanying financial statements and notes to the financial statements give retroactive effect to the Forward Stock Split for all periods presented, unless otherwise indicated.

Initial Public Offering

On May 3, 2022, the Company completed its initial public offering ("IPO") whereby it sold 13,529,750 shares of common stock at a public offering price of $17.00 per share, for net proceeds of approximately $209.5 million, after deducting underwriting discounts, commissions and offering costs of approximately $20.5 million (see Note 5).

Basis of Presentation

The Company, North Bridge V and YamadaCo III were entities under the common control of Frazier Life Sciences X, L.P. or its affiliates (“Frazier”) as a result of, among others, Frazier’s; (i) ownership of a majority of the outstanding capital stock of each of the companies, (ii) financing of each of the companies, (iii) control of board of directors of each of the companies, and (iv) management of each of the companies. As the merged entities were under common control, the financial statements prior to the Merger report the financial position, results of operations and cash flows of these merged companies. The financial statements also include, subsequent to its formation in May 2021, the accounts of HilleVax GmbH, a wholly-owned subsidiary formed in Zurich, Switzerland. The functional currency of both the Company and HilleVax GmbH is the U.S. dollar. The Company’s assets and liabilities that are not denominated in the functional currency are remeasured into U.S. dollars at foreign currency exchange rates in effect at the balance sheet date except for nonmonetary assets, which are remeasured at historical foreign currency exchange rates in effect at the date of transaction. Net realized and unrealized gains and losses from foreign currency transactions and remeasurement are reported in other income (expense), in the condensed consolidated statements of operations and were not material for the periods presented. All intercompany transactions have been eliminated in consolidation.

Liquidity and Capital Resources

From inception to June 30, 2022, the Company has devoted substantially all of its efforts to organizing and staffing the Company, business planning, raising capital, in-licensing its initial vaccine candidate, HIL-214, preparing for and managing its clinical trials of HIL-214, and providing other general and administrative support for these operations. The Company has a limited operating history, has never generated any revenue, and the sales and income potential of its business is unproven. The Company has incurred net losses and negative cash flows from operating activities since its inception and expects to continue to incur net losses into the foreseeable future as it continues the development and potential commercialization of HIL-214. From inception to June 30, 2022, the Company has funded its operations through the issuance of convertible promissory notes, commercial bank debt and the sale of common stock in its IPO which closed in May 2022.

The accompanying condensed consolidated financial statements have been prepared assuming the Company will continue as a going concern, which contemplates the realization of assets and the satisfaction of 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 the outcome of this uncertainty.

Management is required to perform a two-step analysis over the Company’s ability to continue as a going concern. Management must first evaluate whether there are conditions and events that raise substantial doubt about the Company’s ability to continue as a going concern (Step 1). If management concludes that substantial doubt is raised, management is also required to consider whether its plans alleviate that doubt (Step 2). Management believes that it has sufficient working capital on hand to fund operations through at least the next twelve months from the date these financial statements were issued. There can be no assurance that the Company will be successful in acquiring additional funding, if needed, that the Company’s projections of its future working capital needs will prove accurate, or that any additional funding would be sufficient to continue operations in future years.

Unaudited Interim Financial Information

The unaudited condensed consolidated financial statements as of June 30, 2022, and for the three and six months ended June 30, 2022 and 2021, have been prepared in accordance with the rules and regulations of the Securities and Exchange Commission (“SEC”), and with U.S. generally accepted accounting principles (“GAAP”) applicable to interim financial statements. These unaudited condensed consolidated financial statements have been prepared on the same basis as the Company’s audited financial statements and include all adjustments, consisting of only normal recurring accruals, which in the opinion of management are necessary to present fairly the Company’s financial position as of the interim date and results of operations for the interim periods presented. Interim results are not necessarily indicative of results for a full year or future periods. The condensed consolidated balance sheet data as of December 31, 2021 was derived from the Company’s audited financial statements but does not include all disclosures required by GAAP. These unaudited condensed financial statements should be read in conjunction with the Company’s audited financial statements for the year ended December 31, 2021, included in the Company’s prospectus filed with the SEC on April 29, 2022 pursuant to Rule 424(b) under the Securities Act of 1933, as amended.

Use of Estimates

The preparation of the Company’s unaudited condensed consolidated financial statements requires it to make estimates and assumptions that impact the reported amounts of assets, liabilities and expenses and the disclosure of contingent assets and liabilities in the Company’s condensed consolidated financial statements and accompanying notes. The most significant estimates in the Company’s unaudited condensed consolidated financial statements relate to accruals for research and development expenses, and the valuation of convertible promissory notes, warrant liabilities and various other equity instruments. Although these estimates are based on the Company’s knowledge of current events and actions it may undertake in the future, actual results could differ materially from those estimates and assumptions.

Fair Value Option

As permitted under Accounting Standards Codification (“ASC”) 825, Financial Instruments, (“ASC 825”), the Company has elected the fair value option to account for its convertible promissory notes issued through December 31, 2021. In accordance with ASC 825, the Company recorded these convertible promissory notes at fair value with changes in fair value recorded in the condensed consolidated statements of operations. As a result of applying the fair value option, direct costs and fees related to the convertible promissory notes were recognized in earnings as incurred and not deferred. These convertible promissory notes converted to equity in connection with the Company's IPO.

Fair Value Measurements

The accounting guidance defines fair value, establishes a consistent framework for measuring fair value and expands disclosure for each major asset and liability category measured at fair value on either a recurring or non-recurring basis. Fair value is defined as an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. As a basis for considering such assumptions, the accounting guidance establishes a three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value as follows:

Level 1: Observable inputs such as quoted prices in active markets.

Level 2: Inputs, other than the quoted prices in active markets that are observable either directly or indirectly.

Level 3: Unobservable inputs in which there is little or no market data, which require the reporting entity to develop its own assumptions.

The carrying amounts of the Company’s financial instruments, including cash, cash equivalents and restricted cash, classified within the Level 1 designation discussed above, prepaid expenses and other current assets, accounts payable, and accrued liabilities, approximate fair value due to their short maturities. Warrant liabilities and convertible promissory notes were recorded at fair value on a recurring basis until they converted to equity in connection with the Company's IPO which closed in May 2022.

The Company has no financial assets measured at fair value on a recurring basis. None of the Company’s non-financial assets or liabilities are recorded at fair value on a non-recurring basis. No transfers between levels have occurred during the periods presented.

Liabilities measured at fair value on a recurring basis are as follows (in thousands):


			Fair Value Measurements at Reporting Date Using:
	Total		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
As of June 30, 2022:
Warrant liabilities	$	—	$	—	$	—	$	—
Convertible promissory notes		—		—		—		—
Total	$	—	$	—	$	—	$	—
As of December 31, 2021:
Warrant liabilities	$	56,445	$	—	$	—	$	56,445
Convertible promissory notes		158,276		—		—		158,276
Total	$	214,721	$	—	$	—	$	214,721

The warrant liabilities consisted of an issued and outstanding common stock warrant (the “Takeda Warrant”) and a right to receive an additional common stock warrant (the “Takeda Warrant Right”, and together with the Takeda Warrant, the “Takeda Warrants”) issued to Takeda Vaccines, Inc. (“Takeda”) in connection with a July 2021 license agreement. The Takeda Warrants were accounted for as liabilities at fair value as they did 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 the Company’s own stock. The Takeda Warrant, which became exercisable upon the Company's IPO, is for the purchase of 5,883,500 shares of the Company's common stock at an exercise price of $0.0000595 per share that expires on July 2, 2031. As a result of the Company increasing its authorized shares of common stock (see Note 5) in the second quarter of 2022, the Takeda Warrant met the requirements to be equity classified, and the Company reclassified the fair value of the Takeda Warrant to stockholders' equity. The Takeda Warrant Right expired upon the closing of the Company's IPO without effect to the financial statements since no fair value was allocated to it at that time. Prior to the reclassification to stockholders' equity, the fair value of the Takeda Warrants was derived from the model used to estimate the fair value of the Company’s common stock and, upon reclassification, the fair value was based on the Company's IPO price.

The Company issued convertible promissory notes to Frazier (the “Frazier Notes”) from April 2019 to July 2021 and issued unsecured convertible promissory notes in August 2021 (the “August 2021 Notes”) to investors including Frazier. The Company elected the fair value option for each of its convertible promissory note issuances due to certain embedded features within the notes. Prior to conversion, the fair value of the Frazier Notes and the August 2021 Notes was 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. The Frazier Notes were exchanged for August 2021 Notes in August 2021. The principal and accrued interest of the August 2021 Notes automatically converted into shares of the Company's common stock immediately prior to the completion of the IPO (see Note 4). The conversion date fair value of the August 2021 Notes was reclassified to stockholders' equity and was estimated using the Company's publicly traded closing price on the date the notes were converted to common stock.

Prior to their reclassification to stockholders' equity in connection with the IPO, the Company adjusted the carrying value of its warrant liabilities and convertible promissory notes to their estimated fair value at each reporting date, with any related increases or decreases in the fair value recorded as change in fair value of warrant liabilities and as change in fair value of convertible promissory notes, respectively, in the condensed consolidated statements of operations.

The following table summarizes information about the significant unobservable inputs used in the fair value measurements for the Takeda Warrants and the August 2021 Notes as of December 31, 2021:


Liability	Key Unobservable Inputs	Range
Takeda Warrants	Transaction prices per share	$11.83 - $12.54
	Estimated time to liquidity	0.20 - 1.75 years
	Discount rate	20%
August 2021 Notes	Estimated time to liquidity	0.20 - 1.75 years
	Volatility	80% - 100%
	Discount rate	19% - 20%
	Risk-free interest rate	0.1% - 0.7%

There are significant judgments, assumptions and estimates inherent in the determination of the fair value of each of the instruments described above. These include determination of a valuation method and selection of the possible outcomes available to the Company, including the determination of timing and expected future investment returns for such scenarios. The related judgments, assumptions and estimates are highly interrelated and changes in any one assumption could necessitate changes in another. In particular, any changes in the probability of a particular outcome would require a related change to the probability of another outcome. In the future, depending on the valuation approaches used and the expected timing and weighting of each, the inputs described above, or other inputs, may have a greater or lesser impact on the Company’s estimates of fair value.

The following table provides a reconciliation of all liabilities measured at fair value using Level 3 significant unobservable inputs (in thousands):


	Warrant Liabilities			Convertible Promissory Notes
Balance at December 31, 2021	$	56,445		$	158,276
Change in fair value		43,575			51,469
Reclass Takeda Warrant into equity		(100,020	)		—
Conversion of August 2021 Notes into common shares upon IPO (excluding accrued interest of $5,619)		—			(209,745	)
Balance at June 30, 2022	$	—		$	—

Cash and Cash Equivalents

The Company considers all highly liquid investments with original maturities of three months or less when purchased to be cash equivalents. Cash and cash equivalents include cash in readily available checking accounts and money market funds.

Restricted Cash

Restricted cash consists of a money market account securing a standby letter of credit issued in connection with the Company’s Boston Lease (as defined and described in Note 3).

The following table provides a reconciliation of cash and cash equivalents and restricted cash recorded within the accompanying condensed consolidated balance sheets that sum to the amounts shown in the condensed consolidated statements of cash flows (in thousands):


	June 30, 2022
Cash and cash equivalents	$	314,612
Restricted cash		1,631
Total cash, cash equivalents and restricted cash	$	316,243

Concentrations of Credit Risk

Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash, cash equivalents and restricted cash. The Company maintains deposits in federally insured financial institutions in excess of federally insured limits. The Company has not experienced any losses in such accounts and management believes that the Company is not exposed to significant credit risk due to the financial position of the depository institutions in which those deposits are held.

Leases

At the inception of a contractual arrangement, the Company determines whether the contract contains a lease by assessing whether there is an identified asset and whether the contract conveys the right to control the use of the identified asset in exchange for consideration over a period of time. Lease terms are determined at the commencement date by considering whether renewal options and termination options are reasonably assured of exercise. For its long-term operating leases, the Company recognizes a lease liability and a right-of-use (“ROU”) asset on its balance sheet and recognizes lease expense on a straight-line basis over the lease term. The lease liability is determined as the present value of future lease payments, reduced by any reimbursements for tenant improvements, using the discount rate implicit in the lease or, if the implicit rate is not readily determinable, an estimate of the Company’s incremental borrowing rate. The ROU asset is based on the lease liability, adjusted for any prepaid or deferred rent, and reduced by any reimbursements for tenant improvements. The Company aggregates all lease and non-lease components for each class of underlying assets into a single lease component and variable charges for common area maintenance and other variable costs are recognized as expense as incurred. The Company has elected to not recognize a lease liability or ROU asset in connection with short-term operating leases and recognizes lease expense for short-term operating leases on a straight-line basis over the lease term. The Company does not have any financing leases.

Research and Development Expenses and Accruals

All research and development costs are expensed in the period incurred and consist primarily of salaries, payroll taxes, employee benefits, stock-based compensation charges for those individuals involved in research and development efforts, external research and development costs incurred under agreements with contract research organizations and consultants to conduct and support the Company’s clinical trials of HIL-214.

The Company has entered into various research and development contracts with clinical research organizations, clinical manufacturing organizations and other companies. Payments for these activities are based on the terms of the individual agreements, which may differ from the pattern of costs incurred, and payments made in advance of performance are reflected in the accompanying balance sheets as prepaid expenses. The Company records accruals for estimated costs incurred for ongoing research and development activities. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the services, including the phase or completion of events, invoices received and contracted costs. Significant judgments and estimates may be made in determining the prepaid or accrued balances at the end of any reporting period. Actual results could differ from the Company’s estimates.

In-Process Research and Development

The Company evaluates whether acquired intangible assets are a business under applicable accounting standards. Additionally, the Company evaluates whether the acquired assets have a future alternative use. Intangible assets that do not have future alternative use 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.

Patent Costs

Costs related to filing and pursuing patent applications are recorded as general and administrative expenses and expensed as incurred since recoverability of such expenditures is uncertain.

Stock-Based Compensation

Stock-based compensation expense represents the cost of the grant date fair value of equity awards, primarily consisting of stock options and employee stock purchase rights, recognized on a straight-line basis over the requisite service period for stock options and over the respective offering period for employee stock purchase plan rights. The Company recognizes forfeitures as they occur.

Income Taxes

The Company accounts for income taxes under the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements. Under this method, deferred tax assets and liabilities are determined on the basis of the differences between the financial statements and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in the condensed consolidated statements of operations in the period that includes the enactment date.

The Company recognizes net deferred tax assets to the extent that the Company believes these assets are more likely than not to be realized. In making such a determination, management considers all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax-planning strategies, and results of recent operations. If management determines that the Company would be able to realize its deferred tax assets in the future in excess of their net recorded amount, management would make an adjustment to the deferred tax asset valuation allowance, which would reduce the provision for income taxes.

The Company records uncertain tax positions on the basis of a two-step process whereby (i) management determines whether it is more likely than not that the tax positions will be sustained on the basis of the technical merits of the position and (ii) for those tax positions that meet the more-likely-than-not recognition threshold, management recognizes the largest amount of tax benefit that is more than 50 percent likely to be realized upon ultimate settlement with the related tax authority. The Company recognizes interest and penalties related to unrecognized tax benefits within income tax expense in the condensed consolidated statements of operations. Any accrued interest and penalties are included within the related tax liability in the condensed consolidated balance sheets. The Company did not recognize any interest or penalties during the periods presented.

Comprehensive Loss

Comprehensive loss is defined as a change in equity during a period from transactions and other events and circumstances from non-owner sources. The Company’s comprehensive loss was the same as its reported net loss for all periods presented.

Segment Reporting

Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision maker in making decisions on how to allocate resources and assess performance. The Company views its operations and manages its business as one operating segment.

Net Loss Per Share

Basic net loss per share is computed by dividing the consolidated net loss by the weighted-average number of common shares outstanding for the period, without consideration for potentially dilutive securities. The Company has included 5,883,500 shares of common stock under the Takeda Warrant in the calculation of basic weighted-average common shares outstanding from the time the Takeda Warrant became exercisable upon the Company’s IPO because the Takeda Warrant is exercisable for minimal consideration. The Company has excluded weighted-average unvested shares of 2,218,351 shares, 3,368,582 shares, 2,346,789 shares and 2,520,901 shares from the basic weighted-average number of common shares outstanding for the three months ended June 30, 2022 and 2021 and the six months ended June 30, 2022 and 2021, respectively. Diluted net loss per share is computed by dividing the consolidated net loss by the weighted-average number of common shares and dilutive common stock equivalents outstanding for the period determined using the treasury-stock and if-converted methods. Potentially dilutive common stock equivalents are comprised of unvested common stock, common stock options, contingently issuable shares under the Company's employee stock purchase plan, common stock warrants and convertible promissory notes. For all periods presented, there is no difference in the number of shares used to calculate basic and diluted shares outstanding as inclusion of the potentially dilutive common stock equivalents would be antidilutive.

Potentially dilutive securities not included in the calculation of diluted net loss per share, because to do so would be anti-dilutive, are as follows (in common stock equivalent shares):


	June 30,
	2022		2021
Common stock options		1,515,447		—
Unvested common stock		2,115,822		3,630,752
ESPP shares		5,175		—
Total potentially dilutive shares		3,636,444		3,630,752

Emerging Growth Company Status

The Company is an emerging growth company, as defined in the Jumpstart Our Business Startups Act of 2012 (“JOBS Act”). Under the JOBS Act, emerging growth companies can delay adopting new or revised accounting standards issued subsequent to the enactment of the JOBS Act until such time as those standards apply to private companies. The Company has irrevocably elected to avail itself of this exemption from new or revised accounting standards and, therefore, will not be subject to the same new or revised accounting standards as other public companies that are not emerging growth companies.

Recently Adopted Accounting Standards

There were no recently adopted accounting standards which would have a material impact on the Company's financial statements.

Recently Issued Accounting Pronouncements

The Company assesses the adoption impacts of recently issued accounting standards by the Financial Accounting Standards Board or other standard setting bodies on the Company's condensed consolidated financial statements as well as material updates to previous assessments, if any. There were no new material accounting standards issued during 2022 that impacted the Company.

Convertible Promissory Notes and Long-Term Debt

6 Months Ended

Jun. 30, 2022

Debt Disclosure [Abstract]

Convertible Promissory Notes and Long-Term Debt

4. Convertible Promissory Notes and Long-Term Debt

Frazier Convertible Note Financings

During 2019, 2020 and 2021, the Company issued the Frazier Notes for an aggregate of $8.5 million bearing interest at per annum rates ranging from 0.12% to 2.52%. An aggregate of $0.9 million of the Frazier Notes were issued in April, May

and September of 2019 (the “2019 Frazier Notes”), an aggregate of $1.3 million of the Frazier Notes were issued in March, August and October of 2020 (the “2020 Frazier Notes”) and an aggregate of $6.3 million of Frazier Notes were issued from April to July 2021 (the “2021 Frazier Notes”). The Frazier Notes were generally scheduled to mature 12 to 18 months from the date of issuance. The Company recorded changes in the fair value of the Frazier Notes in the condensed consolidated statements of operations. The Frazier Notes were exchanged for convertible promissory notes newly issued in connection with the August 2021 convertible note financing described below. For the three and six months ended June 30, 2021, the Company recognized a $0.4 million and $0.5 million, respectively, change in fair value of convertible promissory notes and recognized $8,000 and $17,000, respectively, of interest expense in connection with outstanding Frazier Notes.

August 2021 Convertible Note Financing

On August 31, 2021, the Company entered into a note purchase agreement under which it issued the August 2021 Notes for an aggregate of $139.52 million. Of the August 2021 Notes, $103.75 million were issued to new investors, $25.0 million were issued to Frazier for cash and $10.77 million were issued to Frazier in exchange for the then outstanding principal and accrued interest on the Frazier Notes. The August 2021 Notes bear interest at a rate of 6% per annum, compounded annually. For the three and six months ended June 30, 2022, the Company recognized a $34.4 million and $51.5 million, respectively, change in fair value of convertible promissory notes in the condensed consolidated statements of operations and recognized $0.7 million and $2.8 million, respectively, of interest expense in connection with outstanding August 2021 Notes. As of December 31, 2021, the outstanding principal balance of the August 2021 Notes was $139.5 million. The principal and accrued interest on the August 2021 Notes automatically converted into 10,672,138 shares of the Company's common stock immediately prior to the completion of the IPO.

Long-Term Debt

The Company’s Term Loan consists of the following (in thousands):


	June 30, 2022
Long-term debt	$	5,000
Accumulated PIK interest		21
Total principal (including PIK interest)		5,021
Unamortized debt discount		(324	)
Long-term debt, net of debt discount	$	4,697

On April 18, 2022, the Company 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. The Company borrowed $5.0 million on April 18, 2022 and has 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”). The Company also has the right to borrow up to $20.0 million through June 30, 2023 (“Term Loan 2”). In addition, the Company has the right to borrow $25.0 million through March 31, 2024 (“Term Loan 3”), provided that on or prior to March 31, 2023, (i) the Company has announced that the 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 the planned interim safety and immunogenicity analysis on the first 200 evaluable subjects in the HIL-214 Vaccine Trial, and (ii) the Company has 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 under the Loan Agreement having occurred and is continuing. The borrowings under the Loan Agreement are collateralized by substantially all of the Company’s 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% (interest rate of 5.80% as of June 30, 2022), and (b) additional interest ("PIK 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 3 have been satisfied and (y) the Company has 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, the Company supports 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, the Company is 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 (which is $2.1 million as of June 30, 2022). The Company 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 the Company to maintain its legal existence and governmental approvals, deliver certain financial reports, maintain insurance coverage and satisfy certain requirements regarding its operating accounts. The negative covenants include, among others, limitations on the Company’s 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 the Company 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.

During the three and six months ended June 30, 2022, the Company has recognized interest expense of $0.2 million related to the Term Loans using the effective interest method. Included in such expense is $0.1 million related to accretion of the final payment fee to other long-term liabilities, $21,000 of PIK interest, $11,000 of debt discount amortization and $0.1 million of coupon interest.

Future minimum principal and interest payments, including the final payment fee, as of June 30, 2022 are as follows (in thousands):


	June 30, 2022
Years ending December 31:
2022 (remaining 6 months)	$	137
2023		303
2024		313
2025		1,680
2026		2,654
2027		3,974
Total principal payments, interest payments and final payment fee		9,061
Less: interest, PIK interest and final payment fee		(4,040	)
Long-term debt	$	5,021

- Definition

The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.

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+ Details

Stockholders' Deficit

6 Months Ended

Jun. 30, 2022

Stockholders Equity Note [Abstract]

Stockholders' Equity (Deficit)

5. Stockholders’ Equity (Deficit)

Initial Public Offering

On May 3, 2022, the Company completed its IPO whereby it sold 13,529,750 shares of common stock at a public offering price of $17.00 per share, for net proceeds of approximately $209.5 million, after deducting underwriting discounts, commissions and offering costs of approximately $20.5 million. In connection with the Company's IPO, the Company increased the number of authorized shares of the Company's common stock and preferred stock to 500,000,000 shares and 50,000,000 shares, respectively.

2021 Equity Incentive Plan

On February 8, 2021, the Company’s board of directors and stockholders approved and adopted the HilleVax, Inc. 2021 Equity Incentive Plan (the “2021 Plan”). The term of the 2021 Plan is ten years from the adoption date. Under the 2021 Plan, the Company may grant stock options, restricted stock, restricted stock units, and other stock-based awards to employees, directors or consultants of the Company and its subsidiaries. The stock options granted under the plan generally vest over a four-year period from the vesting commencement date. Upon the effectiveness of the 2022 Plan defined and described below, no further grants will be made under the 2021 Plan, and any outstanding awards granted under the 2021 Plan will remain subject to the terms of the 2021 Plan and applicable award agreements.

2022 Incentive Award Plan

In April 2022, the Company’s board of directors and stockholders approved the 2022 Incentive Award Plan (the “2022 Plan,” and together with the 2021 Plan, the "Plans") under which the Company may grant stock options, restricted stock, dividend equivalents, restricted stock units, stock appreciation rights, and other stock or cash-based awards to its employees, consultants and directors. The 2022 Plan became effective in connection with the Company’s IPO and will remain in effect until the tenth anniversary of its effective date, which will be April 28, 2032, unless earlier terminated by the Company’s board of directors. The number of shares of the Company's common stock initially available for issuance under awards granted pursuant to the 2022 Plan was the sum of (1) 4,900,000 shares of the Company’s common stock, plus (2) 216,849 shares remaining available for issuance under the 2021 Plan as of the effective date of the 2022 Plan, plus (3) any shares subject to outstanding awards under the 2021 Plan as of the effective date of the 2022 Plan that become available for issuance under the 2022 Plan thereafter in accordance with its terms. The number of shares initially available for issuance will be increased by an annual increase on January 1 of each calendar year beginning in 2023 and ending in and including 2032, equal to the lesser of (1) 5% of the shares of common stock outstanding on the final day of the immediately preceding calendar year and (2) such smaller number of shares as determined by the Company’s board of directors. As of June 30, 2022, 5,116,849 shares were reserved for issuance under the 2022 Plan, of which 4,791,550 shares remained available for future issuance.

2022 Employee Stock Purchase Plan

In April 2022, the Company’s board of directors and stockholders approved the 2022 Employee Stock Purchase Plan (the “2022 ESPP”). The 2022 ESPP became effective in connection with the Company’s IPO. The 2022 ESPP permits eligible employees who elect to participate in an offering under the ESPP to have up to a specified percentage of their eligible earnings withheld, subject to certain limitations, to purchase shares of common stock pursuant to the 2022 ESPP. The price of common stock purchased under the 2022 ESPP is equal to 85% of the lower of the fair market value of the common stock on the first trading day of the offering period or the relevant purchase date. A total of 410,000 shares of the Company’s common stock was initially reserved for issuance under the 2022 ESPP. In addition, the number of shares available for issuance under the 2022 ESPP will be annually increased on January 1 of each calendar year beginning in 2023 and ending in and including 2032, by an amount equal to the lesser of (1) 1% of the shares outstanding on the final day of the immediately preceding calendar year and (2) such smaller number of shares as is determined by the Company’s board of directors, provided that no more than 10,000,000 shares of the Company’s common stock may be issued under the 2022 ESPP. Stock-based compensation expense related to the ESPP for the three and six months ended June 30, 2022 was not material.

A summary of the Company’s stock option activity under the Plans is as follows (in thousands, except share and per share data):


	Number of Outstanding Options			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value
Balance at December 31, 2021		727,873		$	6.99		9.94	$	765
Granted		804,384			9.88
Cancelled		(16,810	)		6.99
Balance at June 30, 2022		1,515,447		$	8.52		9.62	$	1,652
Vested and expected to vest at June 30, 2022		1,515,447		$	8.52		9.62	$	1,652
Exercisable at June 30, 2022		—		$	—		—	$	—

Stock-Based Compensation Expense

The assumptions used in the Black-Scholes option pricing model to determine the fair value of stock option grants were as follows:


	Three Months Ended June 30,		Six Months Ended June 30,
	2022	2021 (1)	2022	2021 (1)
Risk-free interest rate	2.9%–3.4%	— %	1.9%–3.4%	— %
Expected volatility	83.4%–92.9%	— %	83.4%–92.9%	— %
Expected term (in years)	6.0–6.1	—	5.5–6.1	—
Expected dividend yield	0 %	0 %	0 %	0 %

(1)

No stock options were granted until December 2021.

Risk-free interest rate. The risk-free interest rate is based on the U.S. Treasury yield in effect at the time of grant for zero coupon U.S. Treasury notes with maturities similar to the expected term of the awards.

Expected volatility. Given the Company's limited historical stock price volatility data, the expected volatility assumption is based on volatilities of a peer group of similar companies whose share prices are publicly available. The peer group was developed based on companies in the biotechnology industry. The Company will continue to apply this process until a sufficient amount of historical information regarding the volatility of its own stock price becomes available.

Expected term. The expected term represents the period of time that options are expected to be outstanding. Because the Company does not have historical exercise behavior, it determines the expected life assumption using the simplified method, for employees, which is an average of the contractual term of the option and its vesting period.

Expected dividend yield. The Company bases the expected dividend yield assumption on the fact that it has never paid cash dividends and has no present intention to pay cash dividends and, therefore, used an expected dividend yield of zero.

Stock-based compensation expense has been reported in the condensed consolidated statements of operations as follows (in thousands):


	Three Months Ended June 30,				Six Months Ended June 30,
	2022		2021		2022		2021
Research and development	$	179	$	—	$	578	$	—
General and administrative		377		—		250		—
Total	$	556	$	—	$	828	$	—

The weighted average grant date fair value per share of option grants for the three and six months ended June 30, 2022 was $9.36 and $7.31, respectively. There were no option grants during the six months ended June 30, 2021. No stock options were exercised during the six months ended June 30, 2022 or 2021. As of June 30, 2022, total unrecognized stock-based compensation cost was approximately $8.5 million, which is expected to be recognized over a remaining weighted-average period of approximately 3.66 years.

A summary of the Company’s unvested shares is as follows:


	Number of Unvested Shares
Balance at December 31, 2021		2,625,435
Share vesting		(509,613	)
Balance at June 30, 2022		2,115,822

For accounting purposes, unvested shares of common stock are considered issued, but not outstanding until they vest. As of June 30, 2022 and December 31, 2021, the Company had no material repurchase liability related to the unvested shares in the table above.

Common Stock Reserved for Future Issuance

Common stock reserved for future issuance consists of the following:


	June 30, 2022
Common stock warrants		5,883,500
Common stock options outstanding		1,515,447
Shares available for issuance under the Plans		4,791,550
Shares available for issuance under the ESPP		410,000
		12,600,497

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

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+ Details

Organization, Basis of Presentation and Summary of Significant Accounting Policies (Policies)

6 Months Ended

Jun. 30, 2022

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Forward Stock Split

Initial Public Offering

Basis of Presentation

Liquidity and Capital Resources

Unaudited Interim Financial Information

Use of Estimates

Fair Value Option

Fair Value Measurements

Level 1: Observable inputs such as quoted prices in active markets.

Level 2: Inputs, other than the quoted prices in active markets that are observable either directly or indirectly.

Level 3: Unobservable inputs in which there is little or no market data, which require the reporting entity to develop its own assumptions.

Liabilities measured at fair value on a recurring basis are as follows (in thousands):


			Fair Value Measurements at Reporting Date Using:
	Total		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
As of June 30, 2022:
Warrant liabilities	$	—	$	—	$	—	$	—
Convertible promissory notes		—		—		—		—
Total	$	—	$	—	$	—	$	—
As of December 31, 2021:
Warrant liabilities	$	56,445	$	—	$	—	$	56,445
Convertible promissory notes		158,276		—		—		158,276
Total	$	214,721	$	—	$	—	$	214,721

The following table summarizes information about the significant unobservable inputs used in the fair value measurements for the Takeda Warrants and the August 2021 Notes as of December 31, 2021:


Liability	Key Unobservable Inputs	Range
Takeda Warrants	Transaction prices per share	$11.83 - $12.54
	Estimated time to liquidity	0.20 - 1.75 years
	Discount rate	20%
August 2021 Notes	Estimated time to liquidity	0.20 - 1.75 years
	Volatility	80% - 100%
	Discount rate	19% - 20%
	Risk-free interest rate	0.1% - 0.7%

The following table provides a reconciliation of all liabilities measured at fair value using Level 3 significant unobservable inputs (in thousands):


	Warrant Liabilities			Convertible Promissory Notes
Balance at December 31, 2021	$	56,445		$	158,276
Change in fair value		43,575			51,469
Reclass Takeda Warrant into equity		(100,020	)		—
Conversion of August 2021 Notes into common shares upon IPO (excluding accrued interest of $5,619)		—			(209,745	)
Balance at June 30, 2022	$	—		$	—

Cash and Cash Equivalents

Restricted Cash

Restricted cash consists of a money market account securing a standby letter of credit issued in connection with the Company’s Boston Lease (as defined and described in Note 3).


	June 30, 2022
Cash and cash equivalents	$	314,612
Restricted cash		1,631
Total cash, cash equivalents and restricted cash	$	316,243

Concentrations of Credit Risk

Leases

Research and Development Expenses and Accruals

In-Process Research and Development

Patent Costs

Costs related to filing and pursuing patent applications are recorded as general and administrative expenses and expensed as incurred since recoverability of such expenditures is uncertain.

Stock-Based Compensation

Potentially dilutive securities not included in the calculation of diluted net loss per share, because to do so would be anti-dilutive, are as follows (in common stock equivalent shares):


	June 30,
	2022		2021
Common stock options		1,515,447		—
Unvested common stock		2,115,822		3,630,752
ESPP shares		5,175		—
Total potentially dilutive shares		3,636,444		3,630,752

Emerging Growth Company Status

Recently Adopted/Issued Accounting Standards/Pronouncements

Recently Adopted Accounting Standards

There were no recently adopted accounting standards which would have a material impact on the Company's financial statements.

Recently Issued Accounting Pronouncements

Organization, Basis of Presentation and Summary of Significant Accounting Policies (Tables)

6 Months Ended

Jun. 30, 2022

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Liabilities Measured at Fair Value on Recurring Basis

Liabilities measured at fair value on a recurring basis are as follows (in thousands):


			Fair Value Measurements at Reporting Date Using:
	Total		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
As of June 30, 2022:
Warrant liabilities	$	—	$	—	$	—	$	—
Convertible promissory notes		—		—		—		—
Total	$	—	$	—	$	—	$	—
As of December 31, 2021:
Warrant liabilities	$	56,445	$	—	$	—	$	56,445
Convertible promissory notes		158,276		—		—		158,276
Total	$	214,721	$	—	$	—	$	214,721

Summary of Significant Unobservable Inputs Used in Fair Value Measurements

The following table summarizes information about the significant unobservable inputs used in the fair value measurements for the Takeda Warrants and the August 2021 Notes as of December 31, 2021:


Liability	Key Unobservable Inputs	Range
Takeda Warrants	Transaction prices per share	$11.83 - $12.54
	Estimated time to liquidity	0.20 - 1.75 years
	Discount rate	20%
August 2021 Notes	Estimated time to liquidity	0.20 - 1.75 years
	Volatility	80% - 100%
	Discount rate	19% - 20%
	Risk-free interest rate	0.1% - 0.7%

Reconciliation of All Liabilities Measured at Fair Value Using Level 3 Significant Unobservable Inputs

The following table provides a reconciliation of all liabilities measured at fair value using Level 3 significant unobservable inputs (in thousands):


	Warrant Liabilities			Convertible Promissory Notes
Balance at December 31, 2021	$	56,445		$	158,276
Change in fair value		43,575			51,469
Reclass Takeda Warrant into equity		(100,020	)		—
Conversion of August 2021 Notes into common shares upon IPO (excluding accrued interest of $5,619)		—			(209,745	)
Balance at June 30, 2022	$	—		$	—

Schedule of Reconciliation of Cash and Cash Equivalents and Restricted Cash


	June 30, 2022
Cash and cash equivalents	$	314,612
Restricted cash		1,631
Total cash, cash equivalents and restricted cash	$	316,243

Schedule of Potentially Dilutive Securities Not Included in the Calculation of Diluted Net Loss Per Share

Potentially dilutive securities not included in the calculation of diluted net loss per share, because to do so would be anti-dilutive, are as follows (in common stock equivalent shares):


	June 30,
	2022		2021
Common stock options		1,515,447		—
Unvested common stock		2,115,822		3,630,752
ESPP shares		5,175		—
Total potentially dilutive shares		3,636,444		3,630,752

Stockholder's Deficit (Tables)

6 Months Ended

Jun. 30, 2022

Stockholders Equity Note [Abstract]

Summary of Stock Option Activity

A summary of the Company’s stock option activity under the Plans is as follows (in thousands, except share and per share data):


	Number of Outstanding Options			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value
Balance at December 31, 2021		727,873		$	6.99		9.94	$	765
Granted		804,384			9.88
Cancelled		(16,810	)		6.99
Balance at June 30, 2022		1,515,447		$	8.52		9.62	$	1,652
Vested and expected to vest at June 30, 2022		1,515,447		$	8.52		9.62	$	1,652
Exercisable at June 30, 2022		—		$	—		—	$	—

Summary of Assumptions used in Black-Scholes Option Pricing Model to Determine Fair Value of Stock Option Grants

The assumptions used in the Black-Scholes option pricing model to determine the fair value of stock option grants were as follows:


	Three Months Ended June 30,		Six Months Ended June 30,
	2022	2021 (1)	2022	2021 (1)
Risk-free interest rate	2.9%–3.4%	— %	1.9%–3.4%	— %
Expected volatility	83.4%–92.9%	— %	83.4%–92.9%	— %
Expected term (in years)	6.0–6.1	—	5.5–6.1	—
Expected dividend yield	0 %	0 %	0 %	0 %

No stock options were granted until December 2021.

Schedule of Stock-based Compensation Expense

Stock-based compensation expense has been reported in the condensed consolidated statements of operations as follows (in thousands):


	Three Months Ended June 30,				Six Months Ended June 30,
	2022		2021		2022		2021
Research and development	$	179	$	—	$	578	$	—
General and administrative		377		—		250		—
Total	$	556	$	—	$	828	$	—

Summary of Unvested Shares

A summary of the Company’s unvested shares is as follows:


	Number of Unvested Shares
Balance at December 31, 2021		2,625,435
Share vesting		(509,613	)
Balance at June 30, 2022		2,115,822

Schedule of Common Stock Reserved for Future Issuance

Common stock reserved for future issuance consists of the following:


	June 30, 2022
Common stock warrants		5,883,500
Common stock options outstanding		1,515,447
Shares available for issuance under the Plans		4,791,550
Shares available for issuance under the ESPP		410,000
		12,600,497

Convertible Promissory Notes and Long-Term Debt - Additional Information (Details) - USD ($)			3 Months Ended		6 Months Ended		12 Months Ended
	Apr. 18, 2022	Aug. 31, 2021	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Convertible Promissory Notes [Line Items]
Change in fair value of convertible promissory notes			$ 34,396,000	$ 444,000	$ 51,469,000	$ 517,000
Interest expense				8,000,000		17,000,000
Convertible promissory notes, outstanding principal balance							$ 158,276,000
Debt instrument, carrying amount			5,000,000		5,000,000
PIK interest					21,000
Amortization of debt discount					$ 81,000
Minimum
Convertible Promissory Notes [Line Items]
Notes issuance, maturity period					12 months
Maximum
Convertible Promissory Notes [Line Items]
Notes issuance, maturity period					18 months
Term Loan
Convertible Promissory Notes [Line Items]
Interest expense			$ 200,000		$ 200,000
Debt instrument, accretion of final payment fee					100,000
PIK interest					21,000
Amortization of debt discount					11,000
Debt instrument, coupon interest					$ 100,000
Term Loan \| Loan Agreement
Convertible Promissory Notes [Line Items]
Debt instrument, interest rate	4.55%		5.80%		5.80%
Debt instrument, carrying amount	$ 75,000,000.0
Debt instrument, minimum draw amount	$ 5,000,000.0
Debt instrument, basis spread on variable rate	5.00%
Debt instrument, interest rate per annum	2.85%
Debt instrument, payment terms	The monthly payments consist of interest-only through June 1, 2025 or, if prior to April 30, 2025, (x) the conditions to Term Loan 3 have been satisfied and (y) the Company has 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, the Company supports 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.
Debt instrument, maturity date	May 01, 2027
Debt instrument, final payment fee	$ 2,100,000		$ 2,100,000		$ 2,100,000
Percentage of original principal amount payable	7.15%
Percentage of interest upon event of default	4.00%
Term Loan \| Loan Agreement \| Maximum
Convertible Promissory Notes [Line Items]
Percentage of prepayment fee on outstanding principal balance	2.00%
Term Loan \| Prime Rate \| Loan Agreement
Convertible Promissory Notes [Line Items]
Debt instrument, basis spread on variable rate	1.05%
Term Loan 1 \| Loan Agreement
Convertible Promissory Notes [Line Items]
Debt instrument, amount borrowed	$ 5,000,000.0
Frazier
Convertible Promissory Notes [Line Items]
Aggregate amount			$ 8,500,000		$ 8,500,000
Change in fair value of convertible promissory notes				$ 400,000		$ 500,000
Frazier \| Minimum
Convertible Promissory Notes [Line Items]
Bearing interest			0.12%		0.12%
Frazier \| Maximum
Convertible Promissory Notes [Line Items]
Bearing interest			2.52%		2.52%
2019 Frazier Notes
Convertible Promissory Notes [Line Items]
Aggregate amount			$ 900,000		$ 900,000
2020 Frazier Notes
Convertible Promissory Notes [Line Items]
Aggregate amount			1,300,000		1,300,000
2021 Frazier Notes
Convertible Promissory Notes [Line Items]
Aggregate amount			6,300,000		$ 6,300,000
August 2021 Notes \| Common Stock
Convertible Promissory Notes [Line Items]
Debt instrument conversion, common stock shares issued							10,672,138
August 2021 Notes \| Note Purchase Agreement
Convertible Promissory Notes [Line Items]
Aggregate amount		$ 139,520,000
Debt instrument, interest rate		6.00%
Debt instrument, frequency of periodic payment					annually
Change in fair value of convertible promissory notes			34,400,000		$ 51,500,000
Interest expense			700,000		2,800,000
Convertible promissory notes, outstanding principal balance							$ 139,500,000
August 2021 Notes \| Note Purchase Agreement \| New Investors
Convertible Promissory Notes [Line Items]
Aggregate amount		$ 103,750,000
August 2021 Notes \| Note Purchase Agreement \| Frazier Life Sciences X, L.P.
Convertible Promissory Notes [Line Items]
Aggregate amount		10,770,000
Cash proceeds from issuance of convertible notes		$ 25,000,000.0
Term Loan 1 Borrowing through December 15, 2022 \| Term Loan 1 \| Loan Agreement \| Maximum
Convertible Promissory Notes [Line Items]
Debt instrument, available credit under loan agreement			10,000,000.0		10,000,000.0
Term Loan 1 Borrowing through June 30, 2023 \| Term Loan 1 \| Loan Agreement \| Maximum
Convertible Promissory Notes [Line Items]
Debt instrument, available credit under loan agreement			15,000,000.0		15,000,000.0
Term Loan 2 Borrowing through June 30, 2023 \| Term Loan 2 \| Loan Agreement \| Maximum
Convertible Promissory Notes [Line Items]
Debt instrument, available credit under loan agreement			20,000,000.0		20,000,000.0
Term Loan 3 Borrowing through March 31, 2024 \| Term Loan 3 \| Loan Agreement \| Maximum
Convertible Promissory Notes [Line Items]
Debt instrument, available credit under loan agreement			$ 25,000,000.0		$ 25,000,000.0

Stockholders' Deficit - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended
	May 03, 2022	Apr. 30, 2022	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021	Apr. 22, 2022
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected dividend yield			0.00%	0.00%	0.00%	0.00%
Weighted average grant date fair value per share of option grants			$ 9.36		$ 7.31
Stock options granted						0	0
Stock options exercised					0	0
Total unrecognized stock-based compensation cost			$ 8,500		$ 8,500
Total unrecognized stock-based compensation cost expected to be recognized over remaining weighted-average period					3 years 7 months 28 days
Net proceeds from initial public offering					$ 230,006
Increase in number of authorized shares of common stock			500,000,000		500,000,000		50,000,000	50,000,000
Increase in number of authorized shares of preferred stock			50,000,000		50,000,000		0
Number of shares initially available for issuance under awards granted			4,791,550		4,791,550
Initial Public Offering
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Sale of common stock	13,529,750
Public offering price per share	$ 17.00
Net proceeds from initial public offering	$ 209,500
Underwriting discounts, commissions and offering costs	$ 20,500
Increase in number of authorized shares of common stock	500,000,000
Increase in number of authorized shares of preferred stock	50,000,000
Common Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Sale of common stock						1,606,815
Common Stock \| Initial Public Offering
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Sale of common stock			13,529,750		13,529,750
2021 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Plan term					ten years
Vesting period					4 years
Stock options granted					804,384
Number of shares initially available for issuance under awards granted		216,849
Share based compensation arrangement by share-based payment award, terms of award					ten years
2022 Incentive Award Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Plan term		The 2022 Plan became effective in connection with the Company’s IPO and will remain in effect until the tenth anniversary of its effective date, which will be April 28, 2032, unless earlier terminated by the Company’s board of directors. The number of shares of the Company's common stock initially available for issuance under awards granted pursuant to the 2022 Plan was the sum of (1) 4,900,000 shares of the Company’s common stock, plus (2) 216,849 shares remaining available for issuance under the 2021 Plan as of the effective date of the 2022 Plan, plus (3) any shares subject to outstanding awards under the 2021 Plan as of the effective date of the 2022 Plan that become available for issuance under the 2022 Plan thereafter in accordance with its terms.
Number of shares initially available for issuance under awards granted		4,900,000	5,116,849		5,116,849
Share based compensation arrangement by share-based payment award, terms of award		The 2022 Plan became effective in connection with the Company’s IPO and will remain in effect until the tenth anniversary of its effective date, which will be April 28, 2032, unless earlier terminated by the Company’s board of directors. The number of shares of the Company's common stock initially available for issuance under awards granted pursuant to the 2022 Plan was the sum of (1) 4,900,000 shares of the Company’s common stock, plus (2) 216,849 shares remaining available for issuance under the 2021 Plan as of the effective date of the 2022 Plan, plus (3) any shares subject to outstanding awards under the 2021 Plan as of the effective date of the 2022 Plan that become available for issuance under the 2022 Plan thereafter in accordance with its terms.
Shares issuance, ending year		2032
Percentage of shares issued from outstanding number of shares		5.00%
Shares issuance, beginning year		2023
2022 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserved for issuance		410,000
Maximum number of shares that may be authorized in accordance with plan		10,000,000
Shares issuance, ending year		2032
Percentage of shares issued from outstanding number of shares		1.00%
Purchase price of common stock, percent		85.00%
Shares issuance, beginning year		2023

Condensed Consolidated Balance Sheets (Parenthetical) (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Preferred stock par value	$ 0.0001	$ 0.0001
Preferred stock shares authorized	50,000,000	0
Preferred stock shares issued	0	0
Preferred stock shares outstanding	0	0
Common stock par value	$ 0.0001	$ 0.0001
Common stock shares authorized	500,000,000	50,000,000
Common stock shares issued	33,427,209	9,225,321
Common stock shares outstanding	31,311,387	6,599,886
Prepaid expenses and other current assets
Related party amounts	$ 692	$ 0
Accounts Payable
Related party amounts	1,645	22
Accrued Expenses
Related party amounts	757	4,911
Accrued Interest
Related party amounts	0	723
Convertible Promissory Notes Payable
Related party amounts	$ 0	$ 40,580

Organization, Basis of Presentation and Summary of Significant Accounting Policies - Additional Information (Details)			3 Months Ended		6 Months Ended
	May 03, 2022 USD ($) $ / shares shares	Apr. 22, 2022 shares	Jun. 30, 2022 USD ($) $ / shares shares	Jun. 30, 2021 shares	Jun. 30, 2022 USD ($) $ / shares shares	Jun. 30, 2021 shares	Dec. 31, 2021 shares
Organization Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Forward split of shares		1.681
Common stock shares authorized		50,000,000	500,000,000		500,000,000		50,000,000
Net proceeds from initial public offering \| $					$ 230,006,000
Purchase of common stock upon exercise of outstanding warrant			5,883,500		5,883,500
Transaction prices per share \| $ / shares			$ 0.0000595		$ 0.0000595
Basic weighted- average common shares outstanding			26,512,881	4,935,738	16,685,372	4,869,690
Weighted-average unvested shares excluded from computation of earnings per share amount			2,218,351	3,368,582	2,346,789	2,520,901
Initial Public Offering
Organization Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Common stock shares authorized	500,000,000
Sale of common stock	13,529,750
Public offering price per share \| $ / shares	$ 17.00
Net proceeds from initial public offering \| $	$ 209,500,000
Underwriting discounts, commissions and offering costs \| $	$ 20,500,000
Basic weighted- average common shares outstanding					5,883,500
Recurring
Organization Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Assets measured at fair value \| $			$ 0		$ 0
Non-Recurring
Organization Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Non-financial assets at fair value \| $					0
Non-financial liabilities at fair value \| $			$ 0		$ 0

Organization, Basis of Presentation and Summary of Significant Accounting Policies - Summary of Significant Unobservable Inputs Used in Fair Value Measurements (Details)	12 Months Ended
	Dec. 31, 2021 $ / shares	Jun. 30, 2022 $ / shares
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Transaction prices per share		$ 0.0000595
Takeda Warrants \| Discount Rate
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Warrants measurement input	20
Takeda Warrants \| Minimum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Transaction prices per share	$ 11.83
Estimated time to liquidity	2 months 12 days
Takeda Warrants \| Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Transaction prices per share	$ 12.54
Estimated time to liquidity	1 year 9 months
August 2021 Notes \| Minimum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Estimated time to liquidity	2 months 12 days
August 2021 Notes \| Minimum \| Discount Rate
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Notes measurement input	19
August 2021 Notes \| Minimum \| Volatility
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Notes measurement input	80
August 2021 Notes \| Minimum \| Risk-Free Interest Rate
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Notes measurement input	0.1
August 2021 Notes \| Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Estimated time to liquidity	1 year 9 months
August 2021 Notes \| Maximum \| Discount Rate
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Notes measurement input	20
August 2021 Notes \| Maximum \| Volatility
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Notes measurement input	100
August 2021 Notes \| Maximum \| Risk-Free Interest Rate
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Notes measurement input	0.7

Organization, Basis of Presentation and Summary of Significant Accounting Policies - Reconciliation of All liabilities Measured At Fair Value Using Level 3 Significant Unobservable Inputs (in thousands) - (Parenthetical) (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2022 USD ($)
August 2021 Notes
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Debt instrument accrued interest	$ 5,619

Related Party Transactions - Additional Information (Details) - USD ($)	1 Months Ended	3 Months Ended		6 Months Ended
	Mar. 31, 2022	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Related Party Transaction [Line Items]
Contingent payment recorded as in-process research and development				$ 2,500,000
Accounts payable		$ 6,033,000		6,033,000		$ 1,024,000
Accrued expenses		6,419,000		6,419,000		9,164,000
Frazier
Related Party Transaction [Line Items]
Due to related parties		8,000		8,000		22,000
Shared operating expenses		8,000	$ 200,000	34,000	$ 400,000
Mountain Field
Related Party Transaction [Line Items]
Shared operating expenses		0	$ 0	0	$ 5,000
Takeda
Related Party Transaction [Line Items]
Contingent payment recorded as in-process research and development	$ 2,500,000
Takeda \| TSA
Related Party Transaction [Line Items]
Research and development expenses		200,000		1,600,000
Accounts payable		1,600,000		1,600,000
Accrued expenses		$ 800,000		$ 800,000		$ 4,900,000

Condensed Consolidated Statements of Cash Flows (Unaudited) (Parenthetical) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Statement Of Cash Flows [Abstract]
Change in fair value of convertible promissory notes, related party	$ 13,196	$ 517
Related parties prepaid expenses and other assets current	(692)	41
Related parties accounts payable, accrued expenses and other long-term liabilities	(2,531)	(59)
Related parties accrued interest	$ 717	$ 17

Organization, Basis of Presentation and Summary of Significant Accounting Policies - Liabilities Measured at Fair Value on Recurring Basis (Details) - Recurring $ in Thousands	Dec. 31, 2021 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities measured at fair value	$ 214,721
Warrant Liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities measured at fair value	56,445
Convertible Promissory Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities measured at fair value	158,276
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities measured at fair value	214,721
Significant Unobservable Inputs (Level 3) \| Warrant Liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities measured at fair value	56,445
Significant Unobservable Inputs (Level 3) \| Convertible Promissory Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities measured at fair value	$ 158,276

Organization, Basis of Presentation and Summary of Significant Accounting Policies - Schedule of Potential Dilutive Securities Not Included in the Calculation of Diluted Net Loss Per Share (Details) - shares	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount	3,636,444	3,630,752
Common Stock Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount	1,515,447
Unvested common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount	2,115,822	3,630,752
ESPP shares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount	5,175

Commitments and Contingencies - Schedule of Future Minimum Noncancelable Operating Lease Payments (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Commitments And Contingencies Disclosure [Abstract]
2022 (remaining 6 months)	$ 60
2023	3,481
2024	3,582
2025	3,686
2026	3,782
Thereafter	24,935
Total undiscounted operating lease payments	39,526
Present value adjustment	(12,712)
Tenant improvement reimbursements	(5,989)
Operating lease liability	20,825
Less current portion of operating lease liability	35	$ 32
Operating lease liability, net of current portion	$ 20,790	$ 153

Convertible Promissory Notes and Long-Term Debt - Schedule of Future Minimum Principal and Interest Payments (Details) $ in Thousands	Jun. 30, 2022 USD ($)
Debt Disclosure [Abstract]
2022 (remaining 6 months)	$ 137
2023	303
2024	313
2025	1,680
2026	2,654
2027	3,974
Total principal payments, interest payments and final payment fee	9,061
Less: interest, PIK interest and final payment fee	(4,040)
Long-term debt	$ 5,021

Stockholders' Deficit - Summary of Unvested Shares (Details)	6 Months Ended
	Jun. 30, 2022 shares
Stockholders Equity Note [Abstract]
Number of unvested shares, Beginning balance	2,625,435
Number of unvested shares, Shares vesting	(509,613)
Number of unvested shares, Ending balance	2,115,822

Stockholders' Deficit - Schedule of Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2022
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total	$ 556	$ 828
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total	179	578
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total	$ 377	$ 250

Stockholders' Deficit - Schedule of Common Stock Reserved for Future Issuance (Details)	Jun. 30, 2022 shares
Class Of Stock [Line Items]
Common stock reserved for future issuance	12,600,497
Common Stock Warrants
Class Of Stock [Line Items]
Common stock reserved for future issuance	5,883,500
Common Stock Options
Class Of Stock [Line Items]
Common stock reserved for future issuance	1,515,447
Shares Available for Issuance Under the 2021 Plan
Class Of Stock [Line Items]
Common stock reserved for future issuance	4,791,550
Shares available for issuance under the ESPP
Class Of Stock [Line Items]
Common stock reserved for future issuance	410,000