Icosavax (ICVX) 10-Q 10 May 23 2023 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2023	May 03, 2023
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Mar. 31, 2023
Document Fiscal Year Focus	2023
Current Fiscal Year End Date	--12-31
Document Fiscal Period Focus	Q1
Entity Registrant Name	ICOSAVAX, INC.
Entity Central Index Key	0001786255
Entity File Number	001-40655
Entity Tax Identification Number	82-3640549
Entity Current Reporting Status	No
Entity Shell Company	false
Entity Filer Category	Non-accelerated Filer
Entity Interactive Data Current	Yes
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Address Address Line1	1930 Boren Avenue, Suite 1000
Entity Address City Or Town	Seattle
Entity Address, State and Province	WA
Entity Incorporation State Country Code	DE
Entity Address Postal Zip Code	98101
Local Phone Number	737-0085
City Area Code	206
Security12b Title	Common Stock, $0.0001 par value per share
Trading Symbol	ICVX
Security Exchange Name	NASDAQ
Entity Common Stock, Shares Outstanding		41,426,850

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 49,341	$ 58,846
Restricted cash	1,061	1,061
Short-term investments	147,249	159,461
Prepaid expenses and other current assets	4,517	4,545
Total current assets	202,168	223,913
Right-of-use assets - operating leases	3,163	3,247
Property and equipment, net	12,225	11,517
Other noncurrent assets	2,117	0
Total assets	219,673	238,677
Current liabilities:
Accounts payable	1,611	2,892
Accrued and other current liabilities	9,137	8,759
Current portion of operating lease liabilities	2,153	2,137
Total current liabilities	12,901	13,788
Operating lease liabilities, net of current portion	6,645	6,658
Other noncurrent liabilities	44	69
Total liabilities	19,590	20,515
Commitments and contingencies (Note 2)
Stockholders' equity (deficit):
Common stock, $0.0001 par value; 500,000,000 shares authorized at March 31, 2023 and December 31, 2022; 41,397,640 and 41,177,706 shares issued as of March 31, 2023 and December 31, 2022, respectively; 41,345,890 and 41,095,564 shares outstanding as of March 31, 2023 and December 31, 2022, respectively	6	6
Additional paid-in capital	410,528	404,386
Accumulated other comprehensive loss	(63)	(403)
Accumulated deficit	(210,388)	(185,827)
Total stockholders' equity	200,083	218,162
Total liabilities and stockholders' equity	$ 219,673	$ 238,677

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Mar. 31, 2023	Dec. 31, 2022
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	500,000,000	500,000,000
Common stock, shares issued	41,397,640	41,177,706
Common stock, shares outstanding	41,345,890	41,095,564

Condensed Statements of Operati

Condensed Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Grant revenue	$ 0	$ 582
Operating expenses:
Research and development	17,357	17,913
General and administrative	9,165	6,322
Total operating expenses	26,522	24,235
Loss from operations	(26,522)	(23,653)
Other income:
Interest and other income	1,961	120
Total other income	1,961	120
Net loss	(24,561)	(23,533)
Other comprehensive income:
Unrealized losses on available-for-sale debt securities	340	0
Comprehensive loss	$ (24,221)	$ (23,533)
Net loss per share, basic	$ (0.60)	$ (0.60)
Net loss per share, diluted	$ (0.60)	$ (0.60)
Weighted-average common shares outstanding, basic	41,264,508	39,401,805
Weighted-average common shares outstanding, diluted	41,264,508	39,401,805

Condensed Statements of Stockho

Condensed Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid In Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit
Beginning Balance at Dec. 31, 2021	$ 278,220	$ 5	$ 372,284		$ (94,069)
Beginning Balance (in shares) at Dec. 31, 2021		39,175,279
Shares released from restriction upon vesting of early-exercised stock options	27		27
Shares released from restriction upon vesting of early-exercised stock options (in shares)		53,483
Exercise of common stock options	276		276
Exercise of common stock options, (in shares)		295,764
Stock-based compensation	4,550		4,550
Net loss and comprehensive loss	(23,533)				(23,533)
Ending Balance at Mar. 31, 2022	259,540	$ 5	377,137		(117,602)
Ending Balance (in shares) at Mar. 31, 2022		39,524,526
Beginning Balance at Dec. 31, 2022	218,162	$ 6	404,386	$ (403)	(185,827)
Beginning Balance (in shares) at Dec. 31, 2022		41,095,564
Shares released from restriction upon vesting of early-exercised stock options	25		25
Shares released from restriction upon vesting of early-exercised stock options (in shares)		30,392
Exercise of common stock options	$ 117		117
Exercise of common stock options, (in shares)	109,913	109,913
Other comprehensive income	$ 340			340
Vesting of shares of restricted common stock (in Shares)		110,021
Stock-based compensation	6,000		6,000
Net loss and comprehensive loss	(24,561)				(24,561)
Ending Balance at Mar. 31, 2023	$ 200,083	$ 6	$ 410,528	$ (63)	$ (210,388)
Ending Balance (in shares) at Mar. 31, 2023		41,345,890

Condensed Statements of Cash Fl

Condensed Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Operating activities:
Net loss	$ (24,561)	$ (23,533)
Adjustments to reconcile net loss to cash used in operating activities:
Stock-based compensation	6,000	4,550
Depreciation	643	43
Non-cash lease expense	0	185
Amortization of premiums and discounts on short-term investments	(1,048)	0
Changes in operating assets and liabilities:
Prepaids and other current assets	(352)	(1,852)
Right-of-use assets - operating leases	84	0
Other noncurrent assets	(1,737)	0
Accounts payable	(1,059)	1,038
Accrued & other current liabilities	378	2,691
Deferred revenue	0	(582)
Operating lease liabilities	(527)	0
Proceed from Lease Incentive	530	0
Net cash used in operating activities	(21,649)	(17,460)
Investing activities:
Purchases of property and equipment	(1,573)	(1,122)
Purchases of short-term investments	(50,000)	0
Maturities of short-term investments	63,600	0
Net cash provided by (used in) investing activities	12,027	(1,122)
Financing activities:
Proceeds from exercise of stock options	117	276
Net cash provided by financing activities	117	276
Net (decrease) increase in cash and restricted cash	(9,505)	(18,306)
Cash and restricted cash at beginning of period	59,907	280,724
Cash and restricted cash at end of period	50,402	262,418
Supplemental disclosure of noncash activities
Purchases of property and equipment included in accounts payable and accrued liabilities	108	1,224
Right-of-use assets and lease liabilities recognized upon commencement of lease	$ 0	$ 3,370

Description of Business

Description of Business	3 Months Ended
	Mar. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business	1. Description of Business Organization Icosavax, Inc. (the “Company”) was incorporated in the state of Delaware on November 1, 2017, and is located in Seattle, Washington. The Company is focused on the research and development of vaccines against infectious diseases. The Company was founded on computationally designed virus-like particle technology, exclusively licensed for a variety of infectious disease indications from the Institute for Protein Design at the University of Washington. The Company’s business involves inherent risks. These risks include, among others, dependence on key personnel, licensors and third-party service providers, patentability of the Company’s products and processes, the immunogenicity, efficacy and safety of the Company’s vaccine candidates and the potential of the Company’s novel vaccine technology platform. In addition, any of the Company’s vaccine candidates, and the Company’s vaccine technology platform, could become obsolete or diminished in value by discoveries and developments at other organizations. Liquidity The Company had an accumulated deficit of $ 210.4 million, cash, cash equivalents, and short-term investments of $ 196.6 million, and restricted cash of $ 1.1 million at March 31, 2023. Management believes the Company has sufficient capital to execute its strategic plan and fund operations through at least the next twelve months from the date these condensed financial statements are issued. The Company has devoted substantially all its resources to organizing and staffing the Company, business planning, raising capital, in-licensing intellectual property rights, developing vaccine candidates, scaling up manufacturing of vaccine candidates, and preparing for and conducting preclinical studies and clinical trials. The Company has a limited operating history, 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 of its vaccine candidates. From inception to March 31, 2023, the Company has funded its operations primarily through the sale of its convertible preferred stock and common stock. The Company has an Equity Distribution Agreement with Oppenheimer & Co. Inc., pursuant to which the Company may offer and sell shares of the Company’s common stock having an aggregate offering price of up to $ 150.0 million from time to time, in “at the market” offerings. As of March 31, 2023, approximately $ 10.0 million of shares have been sold through the Equity Distribution Agreement, all of which were sold in 2022. As the Company continues to pursue its business plan, it expects to finance its operations through equity offerings, debt financings or other capital sources, including potential strategic collaborations, licenses, and other similar arrangements. However, there can be no assurance that any additional financing or strategic transactions will be available to the Company on acceptable terms, if at all. If events or circumstances occur such that the Company does not obtain additional funding, it may need to delay, reduce or eliminate its product development or future commercialization efforts, which could have a material adverse effect on the Company’s business, results of operations or financial condition. The accompanying financial statements do not include any adjustments that might be necessary if the Company were unable to continue as a going concern.

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2023
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The accompanying unaudited condensed financial statements as of March 31, 2023 and for the three months ended March 31, 2023 and 2022 have been prepared in conformity with generally accepted accounting principles (“GAAP”) in the United States of America for interim financial information and pursuant to Article 10 of Regulation S-X of the Securities Act of 1933, as amended (the “Securities Act”). Accordingly, they do not include all of the information and notes required by GAAP for complete financial statements. These unaudited condensed financial statements include only normal and recurring adjustments that the Company believes are necessary to fairly state the Company’s financial position and the results of its operations and cash flows. The results for the three months ended March 31, 2023 are not necessarily indicative of the results expected for the full fiscal year or any subsequent interim period. The condensed balance sheet at December 31, 2022 has been derived from the audited financial statements at that date but does not include all disclosures required by GAAP for complete financial statements. Because all of the disclosures required by GAAP for complete financial statements are not included herein, these unaudited condensed financial statements and the notes accompanying them should be read in conjunction with the Company’s audited financial statements for the year ended December 31, 2022 included in the Annual Report on Form 10-K (the "Annual Report") that the Company filed with the Securities and Exchange Commission (the “SEC”) on March 30, 2023. Use of Estimates The Company’s significant accounting policies are described in Note 2, “Summary of significant accounting policies,” of the Company’s audited financial statements for the year ended December 31, 2022 included in the Annual Report. There have been no material changes to the significant accounting policies previously disclosed in those audited financial statements. Cash and Cash Equivalents and Restricted Cash Cash and cash equivalents consists of deposits with commercial banks in checking and interest-bearing accounts, highly rated money market funds, and all highly liquid investments with an original maturity of 90 days or less at the time of purchase. Restricted cash represents cash deposited in a collateral account to support a letter of credit issued as security for the Company's operating lease to rent office and laboratory space in Seattle, Washington. Investments Investments include U.S. Treasury and U.S. Agency securities, commercial paper, and corporate debt securities with a final maturity of each security of less than one year. These investments are classified as available-for-sale debt securities, which are recorded at fair value based on quoted prices in active markets. The Company classifies investments maturing within one year of the reporting date as short-term investments. If the estimated fair value of a debt security is below its amortized cost basis, the Company evaluates its ability and intent to hold the investment until a forecasted recovery occurs, including whether the Company has plans to sell the security or whether it is more likely than not the Company will be required to sell any investment before recovery of its amortized cost basis, and whether credit losses exist for the related securities. Factors considered include quoted market prices, recent financial results and operating trends, implied values from any recent transactions or offers of investee securities, credit quality of debt instrument issuers, other publicly available information that may affect the value of the investments, duration and severity of the decline in value, and the Company’s strategy and intentions for holding the investment. Credit-related losses are recognized as an allowance for credit losses on the balance sheet with a corresponding adjustment recognized in net loss. Unrealized gains and losses that are unrelated to credit deterioration are reported in other comprehensive loss. The Company recognizes purchase premiums and discounts as interest income using the interest method over the terms of the securities. Fair Value of Financial Instruments 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 nonrecurring 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. The carrying amounts of prepaid expenses and other assets, accounts payable, and accrued and other current liabilities are considered to be representative of their respective fair values due to their short maturities. 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. If both criteria are met, the Company records the associated lease liability and corresponding right-of-use ("ROU") asset upon commencement of the lease using the implicit rate or a discount rate based on a credit-adjusted secured borrowing rate commensurate with the term of the lease. The Company additionally evaluates leases at their inception to determine if they are to be accounted for as an operating lease or a finance lease. A lease is accounted for as a finance lease if it meets one of the following five criteria: the lease has a purchase option that is reasonably certain of being exercised, the present value of the future cash flows is substantially all of the fair market value of the underlying asset, the lease term is for a significant portion of the remaining economic life of the underlying asset, the title to the underlying asset transfers at the end of the lease term, or if the underlying asset is of such a specialized nature that it is expected to have no alternative uses to the lessor at the end of the term. Leases that do not meet the finance lease criteria are accounted for as an operating lease. Operating lease assets represent a right to use an underlying asset for the lease term and operating lease liabilities represent an obligation to make lease payments arising from the lease. Operating lease liabilities with a term greater than one year and their corresponding ROU assets are recognized on the balance sheet at the commencement date of the lease based on the present value of lease payments over the expected lease term. Certain adjustments to the ROU asset may be required for items such as initial direct costs paid or incentives received. As the Company’s leases do not typically provide an implicit rate, the Company utilizes the appropriate incremental borrowing rate, determined as the rate of interest that the Company would have to pay to borrow on a collateralized basis over a similar term and in a similar economic environment. Lease cost is recognized on a straight-line basis over the lease term and variable lease payments are recognized as operating expenses in the period in which the obligation for those payments is incurred. Variable lease payments primarily include common area maintenance, utilities, real estate taxes, insurance, and other operating costs that are passed on from the lessor in proportion to the space leased by the Company. The Company has elected the practical expedient to not separate lease and non-lease components. Liability for Early Exercise of Stock Options Certain individuals were granted the ability to early exercise their stock options. The shares of common stock issued from the early exercise of unvested stock options are restricted and continue to vest in accordance with the original vesting schedule. The Company has the option to repurchase any unvested shares at the original purchase price upon any voluntary or involuntary termination. The shares purchased by the employees and non-employees pursuant to the early exercise of stock options are not deemed, for accounting purposes, to be outstanding until those shares vest. The cash received in exchange for exercised and unvested shares related to stock options granted is recorded as a liability for the early exercise of stock options on the accompanying balance sheets and will be reclassified as common stock and additional paid-in capital as the shares vest. Unvested shares issued under early exercise provisions subject to repurchase by the Company totaled 51,750 and 82,142 shares as of March 31, 2023 and December 31, 2022, respectively. As of March 31, 2023 and December 31, 2022, the Company recorded $ 0.1 million and $ 0.1 million respectively, associated with shares issued with repurchase rights as other noncurrent liabilities in the accompanying condensed balance sheets. Commitments and Contingencies The Company recognizes a liability with regard to loss contingencies when it believes it is probable a liability has been incurred, and the amount can be reasonably estimated. If some amount within a range of loss appears at the time to be a better estimate than any other amount within the range, the Company accrues that amount. When no amount within the range is a better estimate than any other amount the Company accrues the minimum amount in the range. In the event the Company becomes subject to claims or suits arising in the ordinary course of business, the Company would accrue a liability for such matters when it is probable that future expenditures will be made and such expenditures can be reasonably estimated. The Company has not recorded any such liabilities at either March 31, 2023 or December 31, 2022. Net Loss Per Share Basic net loss per share is calculated by dividing the net loss attributable to common stockholders by the weighted- average number of shares of common stock outstanding for the period. Diluted net loss per share is computed by dividing the net loss by the weighted average number of shares of common stock and common stock equivalents outstanding for the period. Common stock equivalents are only included when their effect is dilutive. The Company’s potentially dilutive securities include outstanding stock options and restricted units under the Company’s equity incentive plan and shares that may be purchased under the Company's employee stock purchase plan. These potentially dilutive securities have been excluded from the computation of diluted net loss per share as they would be anti-dilutive to the net loss per share. For all periods presented, there is no difference in the number of shares used to calculate basic and diluted shares outstanding due to the Company’s net loss position. The following table summarizes the computation of the basic and diluted net loss per share (in thousands, except share and per share data): Three Months Ended 2023 2022 Numerator: Net loss $ ( 24,561 ) $ ( 23,533 ) Denominator: Weighted-average common shares outstanding, basic and 41,264,508 39,401,805 Net loss per share, basic and diluted $ ( 0.60 ) $ ( 0.60 ) The following table sets forth the outstanding potentially dilutive securities that have been excluded in the calculation of diluted net loss per share because their inclusion would be anti-dilutive. As of March 31, 2023 2022 Common stock options and restricted stock units 11,010,300 8,525,522 ESPP shares 71,107 — Unvested common stock 51,750 200,341 Total 11,133,157 8,725,863 Segments The Company has determined that it operates and manages one operating segment, which is the business of researching and developing vaccines against infectious diseases. The Company’s chief operating decision maker, its chief executive officer, reviews financial information on an aggregate basis for the purpose of allocating resources. All assets of the Company are located in the United States. Recent Accounting Pronouncements Recently Adopted Accounting Standards In June 2016, the FASB issued ASU 2016-13, Financial Instruments: Credit Losses (Topic 326) as clarified in ASU 2019-04, ASU 2019-05, and ASU 2020-02 ("ASU 2016-13"). The objective of the standard is to provide information about expected credit losses on financial instruments at each reporting date and to change how other-than-temporary impairments on investment securities are recorded. The ASU 2016-13 is effective beginning January 1, 2023, with early adoption permitted. The Company adopted ASU 2016-13 on January 1, 2023, and the standard did not have a material impact on its financial condition, results of operations, cash flows, and financial statement disclosures. Recently Issued Accounting Standards There were no recently issued accounting standards that the Company believes have had or will have a material impact on its financial position or results of operations.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2023
Fair Value Disclosures [Abstract]
Fair Value Disclosures	3. 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 nonrecurring 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 —Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities. Level 2 —Quoted prices for similar assets and liabilities in active markets, quoted prices in markets that are not active, or inputs which are observable, either directly or indirectly, for substantially the full term of the asset or liability. Level 3 —Prices or valuation techniques that require inputs that are both significant to the fair value measurement and unobservable (i.e., supported by little or no market activity). No transfers between levels have occurred during the periods presented. The Company measures the fair value of money market funds and U.S. Treasury securities based on quoted prices in active markets for identical securities. The Company measures the fair value of U.S. Agency securities, corporate debt securities and commercial paper based on recent trades of securities in inactive markets or based on quoted prices of similar instruments in active markets and other significant inputs derived from or corroborated by observable market data. The following tables summarize, by major security type, the Company's cash, cash equivalents, and investments that are measured at fair value on a recurring basis by level within the fair value hierarchy as of March 31, 2023 and December 31, 2022 (in thousands): March 31, 2023 Fair Value Hierarchy Level Amortized Cost Gross Unrealized Gross Unrealized Fair Market Value Assets: Cash and cash equivalents: Cash Level 1 $ 19,471 $ — $ — $ 19,471 Money market funds Level 1 29,870 — — 29,870 Total cash and cash equivalents 49,341 — — 49,341 Investments: U.S. Treasury securities Level 1 73,352 40 ( 112 ) 73,280 U.S. Agency securities Level 2 23,768 39 — 23,807 Corporate debt securities and commercial paper Level 2 50,192 — ( 30 ) 50,162 Total investments 147,312 79 ( 142 ) 147,249 Total assets measured at fair value on a recurring basis $ 196,653 $ 79 $ ( 142 ) $ 196,590 December 31, 2022 Fair Value Hierarchy Level Amortized Cost Gross Unrealized Gross Unrealized Fair Market Value Assets: Cash and cash equivalents: Cash Level 1 $ 23,376 $ — $ — $ 23,376 Money market funds Level 1 35,470 — — 35,470 Total cash and cash equivalents 58,846 — — 58,846 Investments: U.S. Treasury securities Level 1 82,277 3 ( 331 ) 81,949 U.S. Agency securities Level 2 14,044 28 — 14,072 Corporate debt securities and commercial paper Level 2 63,543 — ( 103 ) 63,440 Total investments 159,864 31 ( 434 ) 159,461 Total assets measured at fair value on a recurring basis $ 218,710 $ 31 $ ( 434 ) $ 218,307 All investments held as of March 31, 2023 and December 31, 2022 were classified as available-for-sale debt securities and had contractual maturities within one year. There were no realized gains or losses on these securities for the three months ended March 31, 2023 and 2022. The aggregate fair value of available-for-sale debt securities in an unrealized loss position was $ 54.9 million as of March 31, 2023, and $ 90.3 million as of December 31, 2022. The Company considered the decline in market value for the securities to be temporary in nature. The Company evaluated its investments in an unrealized loss position and believes it is not more likely than not that the Company will be required to sell the investments, and the Company does not intend to do so prior to recovery of the amortized cost basis.

Grant Agreement

Grant Agreement	3 Months Ended
	Mar. 31, 2023
Grant Agreement [Abstract]
Grant Agreement	4. Grant Agreement Bill & Melinda Gates Foundation Grant Agreement In support of the Company’s development of its former IVX-411 COVID-19 vaccine for pandemic use, in September 2020, the Company entered into the grant agreement (the “Grant Agreement”) with the Bill & Melinda Gates Foundation (“BMGF”), under which it was awarded a grant totaling up to $ 10.0 million (the “Grant”). The Grant supported development activities, including the Company’s regulatory filing preparations and its Phase 1/2 clinical trial of IVX-411. The Grant terminated in accordance with its terms on March 31, 2022. Concurrent with and in connection with the Grant Agreement, the Company entered into a Global Access Commitments Agreement (“GACA”) with BMGF. Under the terms of the GACA, among other things, the Company agreed to make a certain amount of its IVX-411 COVID-19 vaccine for pandemic use available and accessible at affordable pricing to people in certain low- and middle-income countries, if the vaccine was commercialized. The Company discontinued its IVX-411 program in July 2022. Payments received in advance that were related to future performance were deferred and recognized as revenue when the research and development activities were performed. Cash payments received under the Grant Agreement were restricted as to their use until eligible expenditures were incurred. At March 31, 2023 and December 31, 2022, the Company had no restricted cash and deferred revenue under the Grant Agreement. During the three months ended March 31, 2022, the Company recognized revenue from the Grant Agreement of $ 0.6 million. The Company had received the full $ 10.0 million in funding under the Grant Agreement as of December 31, 2021, and through March 31, 2022, the Company had recognized $ 10.0 million in revenue since the inception of the Grant Agreement.

Additional Balance Sheet Inform

Additional Balance Sheet Information	3 Months Ended
	Mar. 31, 2023
Balance Sheet Related Disclosures [Abstract]
Additional Balance Sheet Information	5. Additional Balance Sheet Information Accrued and other current liabilities consist of the following (in thousands): As of March 31, 2023 As of December 31, 2022 Taxes payable $ 50 $ 80 Accrued paid time off 811 664 Accrued bonus 979 3,135 Other accrued liabilities 6,763 4,512 Accrued 401k 351 324 ESPP liability 183 44 Total accrued and other current liabilities $ 9,137 $ 8,759 Other noncurrent assets as of March 31, 2023 consist of advance payments under manufacturing agreements and agreements with clinical research organizations.

License Agreements

License Agreements	3 Months Ended
	Mar. 31, 2023
License Agreements [Abstract]
License Agreements	6. License Agreements License Agreement with the National Institutes of Health The Company is a party to a non-exclusive patent license agreement (as amended, the “NIH Agreement”) with a U.S. government entity, the National Institutes of Health, represented by National Institute of Allergy and Infectious Disease (“NIAID”), which was originally entered into in June 2018. Under the NIH Agreement, the Company obtained a non-exclusive, worldwide, royalty-bearing, sublicensable license under certain NIAID patent rights, and transfer of know-how and biological materials for use in adjuvanted or non-adjuvanted vaccines for the prevention, cure, or treatment of RSV and metapneumovirus (hMPV) infection in humans. Under the NIH Agreement, the Company is required to use commercially reasonable efforts to meet certain specified development, sales and regulatory milestones related to the licensed products within specified time periods. In consideration of the rights granted to the Company under the NIH Agreement, the Company paid a licensing fee upon execution of the NIH Agreement of $ 100,000 , and will pay annual minimum royalty payments starting in the second year after the initial sale of each licensed product which can be credited against any earned royalties due for sales made in the year. The Company is obligated to pay aggregate potential milestone payments of up to $ 8.6 million with respect to future development and commercial milestones. Additionally, the Company has agreed to pay a tiered royalty of a low single digit percentage on net sales of all products applicable to the license. Additional royalties would be due in connection with sublicenses. The Company’s royalty obligations continue for each licensed product for so long as licensed patent rights exist and have not expired, been revoked, lapsed, or held unenforceable. The NIH Agreement will terminate upon the last expiration of the patent rights or the Company may terminate the entirety of the agreement upon discontinuation of development or sales of licensed products and provision of written notice thereof to NIH. The Company incurred no fees associated with the license during the three months ended March 31, 2023 and 2022. License Agreements with University of Washington License Agreement with respect to RSV and Other Pathogens The Company is a party to an exclusive license agreement with the University of Washington (“UW”), originally entered into in June 2018 (as amended, the “UW 2018 Agreement”). Under the UW 2018 Agreement, UW granted the Company an exclusive, worldwide, royalty-bearing, sublicensable license under certain UW patents to make, use, sell, offer to sell, import, and otherwise exploit any product covered by the licensed patents, or licensed products, for the prophylactic and/or therapeutic treatment of RSV infection, hMPV infection and eight other infectious diseases. UW also granted the Company a non-exclusive, worldwide license under certain know-how related to the licensed patents. The licensed patents and know-how generally relate to computationally designed nanoparticles and vaccines based upon such designs, and relate to the Company’s proprietary two-component virus-like-particle technology as well as certain one-component virus-like-particle technology. The Company’s rights and obligations under the UW 2018 Agreement are subject to certain U.S. government rights, certain global access commitment rights for humanitarian purposes to BMGF, certain rights to Howard Hughes Medical Institute ("HHMI"), and certain other limited rights retained by UW. The Company issued 192,276 shares of common stock on August 1, 2018 in exchange for the UW 2018 Agreement’s exclusive license. Under the UW 2018 Agreement, the Company is required to use commercially reasonable efforts to meet certain specified development, regulatory and sales milestones related to the licensed products within specified time periods. In consideration of the rights granted to the Company under the UW 2018 Agreement, the Company is required to pay an annual maintenance fee in the mid four figures starting in 2020. Additionally, the Company is required to pay minimum annual royalties following the first year after commercial sale of each licensed product. There are milestone payments due upon the completion of certain development, regulatory, and commercial milestones for licensed products in the future. The aggregate potential milestone payments for future development, regulatory, and sales-based milestones are $ 1.35 million per indication, up to a maximum of $ 12.2 million in total milestone payments. Additionally, the Company has agreed to pay a royalty of a low single digit percentage on net sales of all licensed products. Additional royalties would be due in connection with sublicenses. The Company’s royalty obligations continue for each licensed product for so long as licensed patent rights exist and have not expired, been revoked, lapsed, or held unenforceable. Unless terminated earlier, the UW 2018 Agreement will remain in effect until all licensed patent rights have terminated and all obligations due to UW have been fulfilled. The last-to-expire licensed patent, if issued, is expected to expire in 2042, subject to any adjustment or extension of patent term that may be available. UW can terminate the UW 2018 Agreement if the Company breaches or fails to perform one of its material duties under the UW 2018 Agreement and the Company is unable to remedy the default within an agreed upon time period that can be extended by UW. The Company may terminate the UW 2018 Agreement at will with prior written notice to UW. Option and License Agreement with Respect to COVID-19 The Company is also a party to an option and license agreement, originally entered into in July 2020 (as amended, the “UW 2020 Agreement”). Under the UW 2020 Agreement, UW granted the Company a non-exclusive, worldwide (excluding South Korea), sublicensable license under certain UW patents to make, use, sell, offer to sell, import, or otherwise exploit any product covered by the licensed patents for the prophylactic and/or therapeutic treatments of SARS-CoV-2 infection. Under an option exercised by the Company, UW granted the Company an exclusive license under the licensed patents for the United States, Canada, Mexico, and Europe (including Switzerland and the United Kingdom) starting in 2025. UW also granted the Company a non-exclusive, worldwide license under certain know-how related to the licensed patents. The licensed patents and know-how generally relate to computationally designed nanoparticles and vaccines based upon such designs. The Company’s rights and obligations under the UW 2020 Agreement are subject to certain U.S. government rights, certain global access commitment rights for humanitarian purposes to BMGF, certain rights to HHMI, and certain other limited rights retained by UW. Under the UW 2020 Agreement, the Company is required to use commercially reasonable efforts to meet certain specified development, regulatory and sales milestones related to the licensed products within specified time periods. The Company has agreed to pay a royalty of a low single digit percentage on net sales of all products applicable to the license. However, the Company will not be required to pay royalties on net sales of any licensed product under the UW 2020 Agreement if the Company is required to pay royalties on net sales under the UW 2018 Agreement. Additional royalties would be due in connection with sublicenses and milestones. The Company’s royalty obligations continue for each licensed product for so long as licensed patent rights exist and have not expired, been revoked, lapsed, or held unenforceable. Unless terminated earlier, the UW 2020 Agreement will remain in effect until all licensed patent rights have terminated and all obligations due to UW have been fulfilled. The last-to-expire licensed patent, if issued, is expected to expire in 2041, subject to any adjustment or extension of patent term that may be available. UW can terminate the UW 2020 Agreement if the Company breaches or fails to perform one of its material duties under the UW 2020 Agreement and the Company is unable to remedy the default within an agreed upon time period that can be extended by UW. The Company may terminate the UW 2020 Agreement at will with prior written notice to UW. During the three months ended March 31, 2023, the Company incurred a negligible amount of fees associated with the 2018 and 2020 Agreements, recorded as research and development expenses. During the three months ended March 31, 2022, the Company incurred a negligible amount of fees associated with the 2018 and 2020 Agreements. License Agreement with Respect to Influenza The Company is a party to a license agreement with UW ("UW Flu License Agreement") entered into in September 2021. Pursuant to the UW Flu License Agreement, UW granted the Company a non-exclusive, worldwide, royalty-bearing, sublicensable (subject to certain restrictions) license under certain UW patents to make, use, sell, offer to sell, import, and otherwise exploit any product covered by the licensed patents ("Licensed Flu Products"), for the prophylactic and/or therapeutic treatment of influenza. UW also granted the Company a non-exclusive, worldwide license to use certain know-how related to the licensed patents. The licensed patents and know-how generally relate to computationally designed nanoparticles and vaccines based upon such designs, and relate to the Company's proprietary two-component virus-like-particle technology and nanoparticle-based influenza virus vaccines. The United States federal government and HHMI have similar rights under the UW Flu License Agreement and the UW 2018 Agreement described above in “License Agreement with respect to RSV and Other Pathogens". The Company is obligated to use commercially reasonable efforts to commercialize Licensed Flu Products, and to initiate a clinical trial with respect to such Licensed Flu Products by a specified date in 2025. If the Company is unable to initiate a clinical trial by the specified date and cannot agree with UW to modify such obligation or does not cure by meeting such obligation, then UW may terminate the UW Flu License Agreement. Under the UW Flu License Agreement, the Company paid UW a one-time upfront license fee, and after September 2023 and for the remainder of the term of the UW Flu License Agreement, the Company is required to pay tiered minimum annual fees ranging from the mid four figures to the mid five figures, with such fees creditable against royalty payments. The Company is required to pay UW up to an aggregate of $ 6.4 million for payments related to development and commercial milestones. The Company is also required to pay UW a fixed, low single-digit percentage royalty on net sales of Licensed Flu Products by the Company and its sublicensees, subject to certain reductions if the Company is required to pay for third-party intellectual property rights in order to commercialize the Licensed Flu Products. The Company is not obligated to pay duplicate royalties on net sales of any Licensed Flu Products if the Company is already required to pay a royalty on such net sales under the UW 2018 Agreement and the UW 2020 Agreement. Unless terminated earlier, the UW Flu License Agreement will remain in effect until all licensed patent rights have expired and all obligations due to UW have been fulfilled. The last-to-expire licensed patent, if issued, is expected to expire in 2041, subject to any adjustment or extension of patent term that may be available. UW can terminate the UW Flu License Agreement if the Company breaches or fails to perform one of its material duties under the UW Flu License Agreement and is unable to remedy the default within an agreed upon time period that can be extended by UW. The Company can terminate the UW Flu License Agreement at will with prior written notice to UW. During the three months ended March 31, 2023 and 2022, the Company incurred a negligible amount of fees associated with the UW Flu License Agreement, recorded as research and development expenses. License Agreement with the University of Texas The Company is a party to an exclusive patent license agreement with the University of Texas at Austin (“UT”) with respect to its hMPV antigen utilized in the IVX-A12 program (the “UT Agreement”). The UT Agreement was entered into in June 2021. Under the UT Agreement, UT granted the Company an exclusive, worldwide, royalty-bearing, sublicensable license under certain patent rights, to use licensed know-how for prevention, cure, amelioration or treatment of respiratory disease caused by hMPV infection in all vaccine fields, excluding up to one mRNA-based vaccine. The Company is obligated to pay aggregate potential milestone payments of up to $ 4.6 million with respect to future development and commercial milestones. Unless terminated earlier, the UT Agreement will remain in effect until all the licensed patent rights have expired. The Company may terminate the UT Agreement with prior written notice to UT. UT may terminate the UT Agreement in whole or in part, or narrow the vaccine field, reduce the territory, or convert the license from exclusive to non-exclusive if the Company: (i) fails to meet its payment obligations, (ii) commits an uncured breach, (iii) commits three or more cured breaches within a specified time period, (iv) challenges the validity, enforceability, or scope of the licensed patent rights, or (v) undergoes certain insolvency-related events. During the three months ended March 31, 2023, the Company incurred no fees associated with the UT Agreement. During the three months ended March 31, 2022, the Company incurred a negligible amount in fees associated with the UT Agreement, recorded as research and development expenses.

Leases

Leases	3 Months Ended
	Mar. 31, 2023
Leases [Abstract]
Leases	. Leases In January 2020, and amended in March 2020, the Company entered into a 12-month lease agreement with renewal options for office and laboratory space in Seattle, Washington. The lease was terminated in June 2022. The lease agreement was considered short-term and therefore, no right-of-use asset or lease liability was recorded. In December 2021, the Company entered into a lease agreement for corporate office and laboratory space in Seattle, Washington. The Company took possession of certain leased space at various dates in January 2022 and March 2022. The lease agreement expires in December 2027 and provides for a one-time option to extend for a period of five additional years. The lease agreement provides the Company with an allowance for tenant improvements of $ 5.3 million that is reimbursed to the Company as construction of improvements occurs. Through March 31, 2023, the Company had received the full amount of the tenant improvement allowance. The monthly base rent will be $ 0.2 million for the first year, beginning in October 2022, and will increase by 3.0 % per year over the initial term. In addition, the Company is obligated to pay for common area maintenance and other costs. Under the terms of the lease agreement, the Company is required to maintain a standby letter of credit of $ 1.1 million at the execution of the lease agreement, reduced to $ 0.9 million in October 2023, and further reduced to $ 0.7 million in October 2024. In June 2022, the Company took possession of temporary office and laboratory space under a short-term lease that terminated in September 2022. Classification of ROU assets and lease liabilities and the weighted-average remaining lease term and discount rate associated with operating leases are as follows (in thousands): As of March 31, 2023 As of December 31, 2022 ROU assets: ROU assets - operating leases $ 3,163 $ 3,247 Lease liabilities: Current portion of operating lease liabilities 2,153 2,137 Noncurrent portion of operating lease liabilities 6,645 6,658 Total lease liabilities $ 8,798 $ 8,795 Weighted-average remaining lease term (in years): Operating leases 4.8 5.0 Weighted-average discount rate: Operating leases 8.0 % 8.0 % The components of lease costs are as follows (in thousands): Three Months Ended 2023 2022 Operating lease costs $ 263 $ 185 Variable lease costs 196 — Short-term lease costs — 141 Total lease costs $ 459 $ 326 The maturities of lease liabilities and reconciliation to the present value of lease liabilities are as follows (in thousands): As of March 31, 2023 2023 $ 1,430 2024 2,201 2025 2,267 2026 2,335 2027 2,405 Total undiscounted lease payments 10,638 Less: imputed interest ( 1,840 ) Total lease liabilities 8,798 Less: current lease liabilities ( 2,153 ) Lease liabilities, net of current portion $ 6,645 Cash paid for amounts included in operating lease liabilities for the three months ended March 31, 2023 was $ 0.7 million.

Preferred Stock and Stockholder

Preferred Stock and Stockholders' Equity (Deficit)	3 Months Ended
	Mar. 31, 2023
Stockholders' Equity Note [Abstract]
Preferred Stock and Stockholders' Equity (Deficit)	8. Preferred Stock and Stockholders’ Equity (Deficit) Preferred Stock The Company is authorized to issue 50,000,000 shares of preferred stock, which shares of preferred stock are currently undesignated. The Company did no t have any outstanding preferred stock as of March 31, 2023 and December 31, 2022. Common Stock The Company is authorized to issue 500,000,000 shares of common stock. As of March 31, 2023 and December 31, 2022, 41,397,640 and 41,177,706 shares were issued, respectively. As of March 31, 2023 and December 31, 2022, shares outstanding, which excludes common stock issued from the early exercise of unvested stock options, were 41,345,890 and 41,095,564 , respectively. Equity Incentive Plans In 2017, the Company established a stock option plan (the “2017 Plan”) under which incentives were granted to officers, employees, directors, consultants and advisors. Awards under the 2017 Plan consisted of restricted stock and incentive and non-qualified stock options to purchase shares of common stock of the Company. During 2021, the Company’s stockholders approved the 2021 Incentive Plan (the “2021 Plan”), which became effective in July 2021. The 2021 Plan provides for the grant of incentive stock options, nonstatutory stock options, stock appreciation rights, restricted stock, dividend equivalents, RSUs and other stock or cash-based awards. The number of shares of the Company’s common stock initially reserved for issuance under the 2021 Plan was 4,600,000 shares; plus the shares of common stock remaining available for issuance under the 2017 Plan as of the effective date of the 2021 Plan, as well as any shares subject to outstanding awards under the 2017 Plan as of the effective date of the 2021 Plan that become available for issuance under the 2021 Plan thereafter in accordance with its terms. The number of shares initially available for issuance increases annually on January 1 of each calendar year beginning in 2022 and ending in and including 2031, equal to the lesser of (A) 5 % of the shares outstanding on the final day of the immediately preceding calendar year and (B) a smaller number of shares as determined by the Company's board of directors. The reserve for the 2021 Plan increased by 2,058,885 shares effective January 1, 2023. No more than 50,000,000 shares of common stock may be issued under the 2021 Plan upon the exercise of incentive stock options. The 2021 Plan is administered by the Board of Directors of the Company or a committee appointed by the Board of Directors, which determines the types of awards to be granted, including the number of shares subject to the awards, the exercise price and the vesting schedule. All option and service-based RSU awards are subject to a time-based vesting period which will generally be four years. Performance-based RSU awards are subject to vesting conditions based on the achievement of specified milestones related to development of vaccine candidates. Certain option and RSU awards provide for accelerated vesting if there is a change in control or if other contractually specified contingencies are met. The term of stock options granted under the 2021 Plan cannot exceed ten years (or five years in the case of incentive stock options granted to certain significant stockholders). Options shall not have an exercise price less than 100 % of the fair market value of the Company’s common stock on the grant date (or 110 % in the case of incentive stock options granted to certain significant stockholders), except with respect to certain substitute awards granted in connection with a corporate transaction. Common stock reserved for future issuance consisted of the following: As of March 31, 2023 Common stock options and restricted stock units granted and outstanding 11,010,300 Shares available for issuance under the equity incentive plans 2,626,207 Shares available for issuance under the 2021 Employee Stock Purchase Plan 1,179,462 Total common stock reserved for issuance 14,815,969 A summary of the status of the options issued under the Company’s equity incentive plans as of March 31, 2023, and information with respect to the changes in options outstanding is as follows (in thousands, except share and per share data) : Options Weighted Average Exercise Weighted Average Remaining Aggregate Balance at December 31, 2022 8,384,990 $ 9.00 Granted 1,825,500 8.94 Exercised ( 109,913 ) 1.06 Balance at March 31, 2023 10,100,577 $ 9.08 8.74 $ 9,552 Vested and expected to vest as of 10,100,577 $ 9.08 8.74 $ 9,552 Vested and exercisable at 2,840,901 $ 9.35 8.19 $ 2,391 Exercisable options in the table above reflect the number of options vested as of the date reported. Options that were granted under the 2017 Plan permitted early exercise. Cash received for early exercise of unvested options is recognized as an other noncurrent liability in the accompanying balance sheet and totaled $ 0.1 million at March 31, 2023. The aggregate intrinsic value in the table above is calculated as the difference between the exercise price of the underlying options and the fair value of the Company’s common stock for all options that were in-the-money as of March 31, 2023. The aggregate intrinsic value of options exercised during the three months ended March 31, 2023 and 2022 was $ 1.0 million and $ 4.3 million, respectively. The weighted-average grant date fair value of options granted during the three months ended March 31, 2023 and 2022 was $ 6.75 and $ 13.08 per share, respectively. A summary of the status of RSUs issued under the Company’s equity incentive plans as of March 31, 2023, and information with respect to the changes in RSUs outstanding is as follows: Service-based RSUs Performance-based RSUs Units Weighted Average Grant-Date Fair Value Units Weighted Average Grant-Date Fair Value Nonvested at December 31, 2022 966,973 $ 17.81 36,000 $ 3.08 Granted 16,771 $ 10.46 — Vested ( 110,021 ) $ 17.48 — Nonvested at March 31, 2023 873,723 $ 17.71 36,000 $ 3.08 Expected to vest at March 31, 2023 873,723 $ 17.71 — The total fair value of RSUs vested during the three months ended March 31, 2023 was $ 1.1 million. No RSUs vested during the three months ended March 31, 2022. The weighted-average grant date fair value of RSUs granted during the three months ended March 31, 2022 was $ 17.72 per share. Employee Stock Purchase Plan During 2021, the Company’s stockholders approved the 2021 Employee Stock Purchase Plan (the “ESPP”), which became effective in July 2021. The ESPP permits eligible employees who elect to participate in an offering under the ESPP to have up to 15% of their eligible earnings withheld, subject to certain limitations, to purchase shares of common stock pursuant to the ESPP. The price of common stock purchased under the ESPP is equal to 85% of the lower of the fair market value of the common stock at the commencement date of each offering period or the relevant date of purchase. The number of shares of common stock initially reserved for issuance under the ESPP was 400,000 shares. The number of shares of common stock reserved for issuance under the ESPP increased on January 1, 2022 and will increase each January 1 thereafter through January 1, 2031, in an amount equal to the lower of (1) 1% of the aggregate number of shares of common stock of the Company outstanding on the final day of the immediately preceding calendar year and (2) such smaller number of shares of common stock as determined by the Board, provided that no more than 15,000,000 shares of our common stock may be issued under the ESPP. The reserve for the ESPP increased by 411,777 shares effective January 1, 2023. No shares were purchased by employees under the ESPP during the three months ended March 31, 2023 and 2022. Stock-based compensation expense related to the ESPP for the three months ended March 31, 2023 and 2022 was $ 0.1 million and $ 0.1 million, respectively. Stock-Based Compensation Expense Stock-based compensation expense for all equity awards and the ESPP has been reported in the condensed statements of operations and comprehensive loss as follows (in thousands): Three Months Ended 2023 2022 Research and development $ 2,414 $ 1,687 General and administrative 3,586 2,863 Total $ 6,000 $ 4,550 The Company recognizes compensation expense for options and RSU awards granted based on their grant date fair value. The compensation expense is recognized over the requisite service period on a straight-line basis. The fair value of RSUs is equal to the closing stock price on the date of grant. The fair value of each stock option granted was determined using the Black-Scholes option pricing model. The assumptions used in the Black-Scholes option pricing model to determine the fair value of the stock option grants issued during periods ended were as follows: Three Months Ended 2023 2022 Risk-free rate of interest 3.54 % - 3.95 % 1.43 % - 2.12 % Expected term (years) 5.26 - 6.09 years 5.77 - 6.08 years Expected stock price volatility 87.6 % - 89.6 % 89.3 % - 118.1 % Dividend yield 0 % 0 % As of March 31, 2023, the unrecognized compensation cost related to outstanding stock options and RSU awards was $ 51.0 million and $ 13.0 million, respectively, and is expected to be recognized as expense over a weighted-average period of approximately 2.7 years.

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2023
Income Tax Disclosure [Abstract]
Income Taxes	9. Income Taxes There was no provision for income taxes recorded during the three months ended March 31, 2023 or 2022. The Company’s deferred tax assets continue to be reduced by a full valuation allowance. The Company is subject to income taxes in the United States and its effective tax rate is calculated quarterly based upon current assumptions relating to the full year’s estimated operating results and various tax-related items. Each quarter an estimate of the annual effective tax rate is updated should the Company revise its forecast of earnings based upon its operating results. If there is a change in the estimated effective annual tax rate, a cumulative adjustment is made. The Company's effective tax rate was 0 % for the three months ended March 31, 2023 and 2022. The difference between the effective tax rate of 0 % and the U.S. federal statutory rate of 21 % for the three months ended March 31, 2023 and 2022 was primarily due to recognizing a full valuation allowance on deferred tax assets. As of March 31, 2023, the Company determined that, based on an evaluation of the four sources of taxable income that may be available under the tax law to realize a tax benefit for deductible temporary differences and carryforwards, and all available evidence, both positive and negative, including the Company's latest forecasts and cumulative losses in recent years, it was more likely than not that none of its deferred tax assets would be realized and therefore the Company continued to record a full valuation allowance. No current tax liability or expense has been recorded in the financial statements.

Employee Saving Plan

Employee Saving Plan	3 Months Ended
	Mar. 31, 2023
Postemployment Benefits [Abstract]
Employee Saving Plan	10. Employee Savings Plan The Company has a defined contribution 401(k) savings plan for those employees who meet minimum eligibility requirements. Under the terms of the plan, eligible employees may contribute up to 90 % of their annual compensation to the plan, subject to Internal Revenue Service limitations. The Company may also, at its sole discretion, make contributions to the plan. The Company did no t make any contributions to the plan during the three months ended March 31, 2023 or 2022.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2023
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed financial statements as of March 31, 2023 and for the three months ended March 31, 2023 and 2022 have been prepared in conformity with generally accepted accounting principles (“GAAP”) in the United States of America for interim financial information and pursuant to Article 10 of Regulation S-X of the Securities Act of 1933, as amended (the “Securities Act”). Accordingly, they do not include all of the information and notes required by GAAP for complete financial statements. These unaudited condensed financial statements include only normal and recurring adjustments that the Company believes are necessary to fairly state the Company’s financial position and the results of its operations and cash flows. The results for the three months ended March 31, 2023 are not necessarily indicative of the results expected for the full fiscal year or any subsequent interim period. The condensed balance sheet at December 31, 2022 has been derived from the audited financial statements at that date but does not include all disclosures required by GAAP for complete financial statements. Because all of the disclosures required by GAAP for complete financial statements are not included herein, these unaudited condensed financial statements and the notes accompanying them should be read in conjunction with the Company’s audited financial statements for the year ended December 31, 2022 included in the Annual Report on Form 10-K (the "Annual Report") that the Company filed with the Securities and Exchange Commission (the “SEC”) on March 30, 2023.
Use of Estimates	Use of Estimates The Company’s significant accounting policies are described in Note 2, “Summary of significant accounting policies,” of the Company’s audited financial statements for the year ended December 31, 2022 included in the Annual Report. There have been no material changes to the significant accounting policies previously disclosed in those audited financial statements.
Cash and Cash Equivalents and Restricted Cash	Cash and Cash Equivalents and Restricted Cash Cash and cash equivalents consists of deposits with commercial banks in checking and interest-bearing accounts, highly rated money market funds, and all highly liquid investments with an original maturity of 90 days or less at the time of purchase. Restricted cash represents cash deposited in a collateral account to support a letter of credit issued as security for the Company's operating lease to rent office and laboratory space in Seattle, Washington. Investments Investments include U.S. Treasury and U.S. Agency securities, commercial paper, and corporate debt securities with a final maturity of each security of less than one year. These investments are classified as available-for-sale debt securities, which are recorded at fair value based on quoted prices in active markets. The Company classifies investments maturing within one year of the reporting date as short-term investments. If the estimated fair value of a debt security is below its amortized cost basis, the Company evaluates its ability and intent to hold the investment until a forecasted recovery occurs, including whether the Company has plans to sell the security or whether it is more likely than not the Company will be required to sell any investment before recovery of its amortized cost basis, and whether credit losses exist for the related securities. Factors considered include quoted market prices, recent financial results and operating trends, implied values from any recent transactions or offers of investee securities, credit quality of debt instrument issuers, other publicly available information that may affect the value of the investments, duration and severity of the decline in value, and the Company’s strategy and intentions for holding the investment. Credit-related losses are recognized as an allowance for credit losses on the balance sheet with a corresponding adjustment recognized in net loss. Unrealized gains and losses that are unrelated to credit deterioration are reported in other comprehensive loss. The Company recognizes purchase premiums and discounts as interest income using the interest method over the terms of the securities.
Fair Value of Financial Instruments	Fair Value of Financial Instruments 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 nonrecurring 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. The carrying amounts of prepaid expenses and other assets, accounts payable, and accrued and other current liabilities are considered to be representative of their respective fair values due to their short maturities.
Leases	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. If both criteria are met, the Company records the associated lease liability and corresponding right-of-use ("ROU") asset upon commencement of the lease using the implicit rate or a discount rate based on a credit-adjusted secured borrowing rate commensurate with the term of the lease. The Company additionally evaluates leases at their inception to determine if they are to be accounted for as an operating lease or a finance lease. A lease is accounted for as a finance lease if it meets one of the following five criteria: the lease has a purchase option that is reasonably certain of being exercised, the present value of the future cash flows is substantially all of the fair market value of the underlying asset, the lease term is for a significant portion of the remaining economic life of the underlying asset, the title to the underlying asset transfers at the end of the lease term, or if the underlying asset is of such a specialized nature that it is expected to have no alternative uses to the lessor at the end of the term. Leases that do not meet the finance lease criteria are accounted for as an operating lease. Operating lease assets represent a right to use an underlying asset for the lease term and operating lease liabilities represent an obligation to make lease payments arising from the lease. Operating lease liabilities with a term greater than one year and their corresponding ROU assets are recognized on the balance sheet at the commencement date of the lease based on the present value of lease payments over the expected lease term. Certain adjustments to the ROU asset may be required for items such as initial direct costs paid or incentives received. As the Company’s leases do not typically provide an implicit rate, the Company utilizes the appropriate incremental borrowing rate, determined as the rate of interest that the Company would have to pay to borrow on a collateralized basis over a similar term and in a similar economic environment. Lease cost is recognized on a straight-line basis over the lease term and variable lease payments are recognized as operating expenses in the period in which the obligation for those payments is incurred. Variable lease payments primarily include common area maintenance, utilities, real estate taxes, insurance, and other operating costs that are passed on from the lessor in proportion to the space leased by the Company. The Company has elected the practical expedient to not separate lease and non-lease components.
Liability for Early Exercise of Stock Options	Liability for Early Exercise of Stock Options Certain individuals were granted the ability to early exercise their stock options. The shares of common stock issued from the early exercise of unvested stock options are restricted and continue to vest in accordance with the original vesting schedule. The Company has the option to repurchase any unvested shares at the original purchase price upon any voluntary or involuntary termination. The shares purchased by the employees and non-employees pursuant to the early exercise of stock options are not deemed, for accounting purposes, to be outstanding until those shares vest. The cash received in exchange for exercised and unvested shares related to stock options granted is recorded as a liability for the early exercise of stock options on the accompanying balance sheets and will be reclassified as common stock and additional paid-in capital as the shares vest. Unvested shares issued under early exercise provisions subject to repurchase by the Company totaled 51,750 and 82,142 shares as of March 31, 2023 and December 31, 2022, respectively. As of March 31, 2023 and December 31, 2022, the Company recorded $ 0.1 million and $ 0.1 million respectively, associated with shares issued with repurchase rights as other noncurrent liabilities in the accompanying condensed balance sheets.
Commitments and Contingencies	Commitments and Contingencies The Company recognizes a liability with regard to loss contingencies when it believes it is probable a liability has been incurred, and the amount can be reasonably estimated. If some amount within a range of loss appears at the time to be a better estimate than any other amount within the range, the Company accrues that amount. When no amount within the range is a better estimate than any other amount the Company accrues the minimum amount in the range. In the event the Company becomes subject to claims or suits arising in the ordinary course of business, the Company would accrue a liability for such matters when it is probable that future expenditures will be made and such expenditures can be reasonably estimated. The Company has not recorded any such liabilities at either March 31, 2023 or December 31, 2022.
Net Loss Per Share	Net Loss Per Share Basic net loss per share is calculated by dividing the net loss attributable to common stockholders by the weighted- average number of shares of common stock outstanding for the period. Diluted net loss per share is computed by dividing the net loss by the weighted average number of shares of common stock and common stock equivalents outstanding for the period. Common stock equivalents are only included when their effect is dilutive. The Company’s potentially dilutive securities include outstanding stock options and restricted units under the Company’s equity incentive plan and shares that may be purchased under the Company's employee stock purchase plan. These potentially dilutive securities have been excluded from the computation of diluted net loss per share as they would be anti-dilutive to the net loss per share. For all periods presented, there is no difference in the number of shares used to calculate basic and diluted shares outstanding due to the Company’s net loss position. The following table summarizes the computation of the basic and diluted net loss per share (in thousands, except share and per share data): Three Months Ended 2023 2022 Numerator: Net loss $ ( 24,561 ) $ ( 23,533 ) Denominator: Weighted-average common shares outstanding, basic and 41,264,508 39,401,805 Net loss per share, basic and diluted $ ( 0.60 ) $ ( 0.60 ) The following table sets forth the outstanding potentially dilutive securities that have been excluded in the calculation of diluted net loss per share because their inclusion would be anti-dilutive. As of March 31, 2023 2022 Common stock options and restricted stock units 11,010,300 8,525,522 ESPP shares 71,107 — Unvested common stock 51,750 200,341 Total 11,133,157 8,725,863
Segments	Segments The Company has determined that it operates and manages one operating segment, which is the business of researching and developing vaccines against infectious diseases. The Company’s chief operating decision maker, its chief executive officer, reviews financial information on an aggregate basis for the purpose of allocating resources. All assets of the Company are located in the United States.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Recently Adopted Accounting Standards In June 2016, the FASB issued ASU 2016-13, Financial Instruments: Credit Losses (Topic 326) as clarified in ASU 2019-04, ASU 2019-05, and ASU 2020-02 ("ASU 2016-13"). The objective of the standard is to provide information about expected credit losses on financial instruments at each reporting date and to change how other-than-temporary impairments on investment securities are recorded. The ASU 2016-13 is effective beginning January 1, 2023, with early adoption permitted. The Company adopted ASU 2016-13 on January 1, 2023, and the standard did not have a material impact on its financial condition, results of operations, cash flows, and financial statement disclosures. Recently Issued Accounting Standards There were no recently issued accounting standards that the Company believes have had or will have a material impact on its financial position or results of operations.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2022
Accounting Policies [Abstract]
Computation of Basic and Diluted Net Loss Per Share	The following table summarizes the computation of the basic and diluted net loss per share (in thousands, except share and per share data): Three Months Ended 2023 2022 Numerator: Net loss $ ( 24,561 ) $ ( 23,533 ) Denominator: Weighted-average common shares outstanding, basic and 41,264,508 39,401,805 Net loss per share, basic and diluted $ ( 0.60 ) $ ( 0.60 )
Summary of Outstanding Potentially Dilutive Securities Excluded in Calculation of Diluted Net Loss Per Share	The following table sets forth the outstanding potentially dilutive securities that have been excluded in the calculation of diluted net loss per share because their inclusion would be anti-dilutive. As of March 31, 2023 2022 Common stock options and restricted stock units 11,010,300 8,525,522 ESPP shares 71,107 — Unvested common stock 51,750 200,341 Total 11,133,157 8,725,863

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2023
Fair Value Disclosures [Abstract]
Fair Value, Liabilities Measured on Recurring Basis	The following tables summarize, by major security type, the Company's cash, cash equivalents, and investments that are measured at fair value on a recurring basis by level within the fair value hierarchy as of March 31, 2023 and December 31, 2022 (in thousands): March 31, 2023 Fair Value Hierarchy Level Amortized Cost Gross Unrealized Gross Unrealized Fair Market Value Assets: Cash and cash equivalents: Cash Level 1 $ 19,471 $ — $ — $ 19,471 Money market funds Level 1 29,870 — — 29,870 Total cash and cash equivalents 49,341 — — 49,341 Investments: U.S. Treasury securities Level 1 73,352 40 ( 112 ) 73,280 U.S. Agency securities Level 2 23,768 39 — 23,807 Corporate debt securities and commercial paper Level 2 50,192 — ( 30 ) 50,162 Total investments 147,312 79 ( 142 ) 147,249 Total assets measured at fair value on a recurring basis $ 196,653 $ 79 $ ( 142 ) $ 196,590 December 31, 2022 Fair Value Hierarchy Level Amortized Cost Gross Unrealized Gross Unrealized Fair Market Value Assets: Cash and cash equivalents: Cash Level 1 $ 23,376 $ — $ — $ 23,376 Money market funds Level 1 35,470 — — 35,470 Total cash and cash equivalents 58,846 — — 58,846 Investments: U.S. Treasury securities Level 1 82,277 3 ( 331 ) 81,949 U.S. Agency securities Level 2 14,044 28 — 14,072 Corporate debt securities and commercial paper Level 2 63,543 — ( 103 ) 63,440 Total investments 159,864 31 ( 434 ) 159,461 Total assets measured at fair value on a recurring basis $ 218,710 $ 31 $ ( 434 ) $ 218,307

Additional Balance Sheet Info_2

Additional Balance Sheet Information (Tables)	3 Months Ended
	Mar. 31, 2023
Balance Sheet Related Disclosures [Abstract]
Schedule of Accrued and Other Current Liabilities	Accrued and other current liabilities consist of the following (in thousands): As of March 31, 2023 As of December 31, 2022 Taxes payable $ 50 $ 80 Accrued paid time off 811 664 Accrued bonus 979 3,135 Other accrued liabilities 6,763 4,512 Accrued 401k 351 324 ESPP liability 183 44 Total accrued and other current liabilities $ 9,137 $ 8,759

Leases (Tables)

Leases (Tables)	3 Months Ended
	Mar. 31, 2023
Leases [Abstract]
Classified of ROU assets and lease liabilities and weighted average remaining lease term	Classification of ROU assets and lease liabilities and the weighted-average remaining lease term and discount rate associated with operating leases are as follows (in thousands): As of March 31, 2023 As of December 31, 2022 ROU assets: ROU assets - operating leases $ 3,163 $ 3,247 Lease liabilities: Current portion of operating lease liabilities 2,153 2,137 Noncurrent portion of operating lease liabilities 6,645 6,658 Total lease liabilities $ 8,798 $ 8,795 Weighted-average remaining lease term (in years): Operating leases 4.8 5.0 Weighted-average discount rate: Operating leases 8.0 % 8.0 %
Schedule of Component of Lease Cost	The components of lease costs are as follows (in thousands): Three Months Ended 2023 2022 Operating lease costs $ 263 $ 185 Variable lease costs 196 — Short-term lease costs — 141 Total lease costs $ 459 $ 326
Schedule of Maturities of Lease Liabilities	The maturities of lease liabilities and reconciliation to the present value of lease liabilities are as follows (in thousands): As of March 31, 2023 2023 $ 1,430 2024 2,201 2025 2,267 2026 2,335 2027 2,405 Total undiscounted lease payments 10,638 Less: imputed interest ( 1,840 ) Total lease liabilities 8,798 Less: current lease liabilities ( 2,153 ) Lease liabilities, net of current portion $ 6,645 Cash paid for amounts included in operating lease liabilities for the three months ended March 31, 2023 was $ 0.7 million.

Preferred Stock and Stockhold_2

Preferred Stock and Stockholders' Equity (Deficit) (Tables)	3 Months Ended
	Mar. 31, 2023
Stockholders' Equity Note [Abstract]
Schedule of common stock reserved for future issuance	Common stock reserved for future issuance consisted of the following: As of March 31, 2023 Common stock options and restricted stock units granted and outstanding 11,010,300 Shares available for issuance under the equity incentive plans 2,626,207 Shares available for issuance under the 2021 Employee Stock Purchase Plan 1,179,462 Total common stock reserved for issuance 14,815,969
Summary of the Status of the Options Issued Under the Plan	A summary of the status of the options issued under the Company’s equity incentive plans as of March 31, 2023, and information with respect to the changes in options outstanding is as follows (in thousands, except share and per share data) : Options Weighted Average Exercise Weighted Average Remaining Aggregate Balance at December 31, 2022 8,384,990 $ 9.00 Granted 1,825,500 8.94 Exercised ( 109,913 ) 1.06 Balance at March 31, 2023 10,100,577 $ 9.08 8.74 $ 9,552 Vested and expected to vest as of 10,100,577 $ 9.08 8.74 $ 9,552 Vested and exercisable at 2,840,901 $ 9.35 8.19 $ 2,391
Summary of the RSU under Equity incentive plan	A summary of the status of RSUs issued under the Company’s equity incentive plans as of March 31, 2023, and information with respect to the changes in RSUs outstanding is as follows: Service-based RSUs Performance-based RSUs Units Weighted Average Grant-Date Fair Value Units Weighted Average Grant-Date Fair Value Nonvested at December 31, 2022 966,973 $ 17.81 36,000 $ 3.08 Granted 16,771 $ 10.46 — Vested ( 110,021 ) $ 17.48 — Nonvested at March 31, 2023 873,723 $ 17.71 36,000 $ 3.08 Expected to vest at March 31, 2023 873,723 $ 17.71 —
Schedule of Stock-based Compensation Expense for All Equity Awards	Stock-based compensation expense for all equity awards and the ESPP has been reported in the condensed statements of operations and comprehensive loss as follows (in thousands): Three Months Ended 2023 2022 Research and development $ 2,414 $ 1,687 General and administrative 3,586 2,863 Total $ 6,000 $ 4,550
Summary of Assumptions Used in Black-Scholes Model	The fair value of each stock option granted was determined using the Black-Scholes option pricing model. The assumptions used in the Black-Scholes option pricing model to determine the fair value of the stock option grants issued during periods ended were as follows: Three Months Ended 2023 2022 Risk-free rate of interest 3.54 % - 3.95 % 1.43 % - 2.12 % Expected term (years) 5.26 - 6.09 years 5.77 - 6.08 years Expected stock price volatility 87.6 % - 89.6 % 89.3 % - 118.1 % Dividend yield 0 % 0 %

Description of Business - Addit

Description of Business - Additional Information (Detail) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Subsidiary, Sale of Stock [Line Items]
Accumulated Deficit	$ 210,388	$ 185,827
Cash and cash equivalents restricted cash	196,600
Restricted cash	1,100
Common stock aggregate offering price	150,000
Common stock sold	$ 10,000

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Details) $ in Millions	3 Months Ended
	Mar. 31, 2023 USD ($) Segment shares	Dec. 31, 2022 USD ($) shares
Number of shares subject to repurchase | shares	51,750	82,142
Liabilities with shares issued with repurchase rights | $	$ 0.1	$ 0.1
Number Of Reporting Units | Segment	1

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Computation of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Numerator:
Net loss	$ (24,561)	$ (23,533)
Denominator:
Weighted-average common shares outstanding, basic	41,264,508	39,401,805
Weighted-average common shares outstanding, diluted	41,264,508	39,401,805
Net loss per share, basic	$ (0.60)	$ (0.60)
Net loss per share, diluted	$ (0.60)	$ (0.60)

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Summary of Outstanding Potentially Dilutive Securities Excluded in Calculation of Diluted Net Loss Per Share (Details) - shares	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive common equivalent shares	11,133,157	8,725,863
Stock Option [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive common equivalent shares	11,010,300	8,525,522
Unvested Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive common equivalent shares	51,750	200,341
ESPP shares
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive common equivalent shares	71,107	0

Fair value measurements - Sched

Fair value measurements - Schedule of Fair Value Liabilities Measured on Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	$ 196,653	$ 218,710
Gross Unrealized Gains	79	31
Gross Unrealized Losses	(142)	(434)
Fair Market Value	196,590	218,307
Cash And Cash Equivalents [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	49,341	58,846
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Market Value	49,341	58,846
Investment [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	147,312	159,864
Gross Unrealized Gains	79	31
Gross Unrealized Losses	(142)	(434)
Fair Market Value	147,249	159,461
Level 1 | Cash And Cash Equivalents [Member] | Fair Value, Recurring [Member] | Cash [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	19,471	23,376
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Market Value	19,471	23,376
Level 1 | Cash And Cash Equivalents [Member] | Fair Value, Recurring [Member] | Money market funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	29,870	35,470
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Market Value	29,870	35,470
Level 1 | Investment [Member] | Fair Value, Recurring [Member] | U.S. Treasury securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	73,352	82,277
Gross Unrealized Gains	40	3
Gross Unrealized Losses	(112)	(331)
Fair Market Value	73,280	81,949
Level 2 | Investment [Member] | Fair Value, Recurring [Member] | U.S. Agency securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	23,768	14,044
Gross Unrealized Gains	39	28
Gross Unrealized Losses	0	0
Fair Market Value	23,807	14,072
Level 2 | Investment [Member] | Fair Value, Recurring [Member] | Corporate debt securities and commercial paper [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	50,192	63,543
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(30)	(103)
Fair Market Value	$ 50,162	$ 63,440

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Unrealized Loss on Securities	$ 54.9	$ 90.3

Grant Agreement - Additional In

Grant Agreement - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2021	Dec. 31, 2022
Grant Agreement [Line Items]
Restricted cash	$ 1,100
BMGF Grant
Grant Agreement [Line Items]
Grant received	10,000	$ 10,000	$ 10,000
Deferred revenue	0			$ 0
Restricted cash	$ 0			$ 0
Revenue from grant		$ 600

Additional Balance Sheet Info_3

Additional Balance Sheet Information - Schedule of Accrued and Other Current Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Balance Sheet Related Disclosures [Abstract]
Taxes payable	$ 50	$ 80
Accrued paid time off	811	664
Accrued bonus	979	3,135
Other accrued liabilities	6,763	4,512
Accrued 401K	351	324
ESPP Liability	183	44
Total accrued and other current liabilities	$ 9,137	$ 8,759

License Agreements - Additional

License Agreements - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022	Aug. 01, 2018
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Payment of license fee	$ 0	$ 0
Common stock, shares issued	41,397,640		41,177,706
NIH Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Payment of license fee	$ 100,000
Potential milestone payments	8,600
U W Two Thousand And Eighteen Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Common stock, shares issued				192,276
Potential Payments for Future Development Regulatory and Sales Based Milestones	1,350
Total Milestone Payments	12,200
Uw Flu License Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Aggregate Payments Related To Cumulative Net Sales Thresholds	6,400
U T Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Payment of license fee	0
Potential milestone payments	$ 4,600

Leases - Additional Information

Leases - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2023	Dec. 31, 2021	Dec. 31, 2022
Lessee, Lease, Description [Line Items]
Lease agreement option to extend	the Company entered into a 12-month lease agreement with renewal options
Lease liability	$ 8,798		$ 8,795
Operating lease paid in cash	700
Right-of-use assets - operating leases	$ 3,163		$ 3,247
Lease Agreements [Member]
Lessee, Lease, Description [Line Items]
Lease agreement option to extend		The lease agreement expires in December 2027 and provides for a one-time option to extend for a period of five additional years.
Monthly Base Rent		$ 200
Allowance for tenant improvements		$ 5,300
Monthly base rent yearly increase percentage		3%
Standby Letters of Credit | Lease Agreements [Member]
Lessee, Lease, Description [Line Items]
Standby letters of credit		$ 1,100
Second Anniversary [Member] | Lease Agreements [Member]
Lessee, Lease, Description [Line Items]
Standby letters of credit		700
First Anniversary [Member] | Lease Agreements [Member]
Lessee, Lease, Description [Line Items]
Standby letters of credit		$ 900

Leases - Classified of ROU asse

Leases - Classified of ROU assets and lease liabilities and weighted average remaining lease term (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Leases [Abstract]
Right-of-use assets - operating leases	$ 3,163	$ 3,247
Current portion of operating lease liabilities	2,153	2,137
Noncurrent portion of operating lease liabilities	6,645	6,658
Total lease liabilities	$ 8,798	$ 8,795
Weighted-average remaining lease term (in years): Operating leases	4 years 9 months 18 days	5 years
Weighted-average discount rate: Operating leases	8%	8%

Leases - Schedule of Component

Leases - Schedule of Component of Lease Cost (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Leases [Abstract]
Operating lease costs	$ 263	$ 185
Variable lease costs	196	0
Short-term lease costs	0	141
Total lease costs	$ 459	$ 326

Leases - Schedule of Maturities

Leases - Schedule of Maturities of Lease Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Leases [Abstract]
2023	$ 1,430
2024	2,201
2025	2,267
2026	2,335
2027	2,405
Lessee, Operating Lease, Liability, Undiscounted Excess Amount, Total	10,638
Less: imputed interest	(1,840)
Total lease liabilities	8,798	$ 8,795
Less: current lease liabilities	(2,153)	(2,137)
Operating lease liabilities, net of current portion	$ 6,645	$ 6,658

Preferred Stock and Stockhold_3

Preferred Stock and Stockholders' Equity (Deficit) - Schedule of Common Stock Reserved for Future Issuance (Details)	Mar. 31, 2023 shares
Class Of Stock [Line Items]
Common stock reserved for issuance	14,815,969
Equity Incentive Plan [Member]
Class Of Stock [Line Items]
Common stock reserved for issuance	2,626,207
2021 Employee Stock Purchase Plan [Member]
Class Of Stock [Line Items]
Common stock reserved for issuance	1,179,462
Common Stock Options and Restricted Stock Units [Member]
Class Of Stock [Line Items]
Common stock reserved for issuance	11,010,300

Preferred Stock and Stockhold_4

Preferred Stock and Stockholders' Equity (Deficit) - Summary of the Status of the Options Issued Under the Plan (Details) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2023 USD ($) $ / shares shares
Stockholders' Equity Note [Abstract]
Options Outstanding, Balance at December 31, 2022 | shares	8,384,990
Options Outstanding, Granted | shares	1,825,500
Options Outstanding, Exercised | shares	(109,913)
Options Outstanding, Balance at March 31, 2023 | shares	10,100,577
Options Outstanding, Vested and expected to vest as of March 31, 2022 | shares	10,100,577
Options Outstanding, Vested and exercisable at March 31, 2023 | shares	2,840,901
Weighted average exercise price per share, Balance at December 31, 2022 | $ / shares	$ 9
Weighted average exercise price per share, Granted | $ / shares	8.94
Weighted average exercise price per share, Exercised | $ / shares	1.06
Weighted average exercise price per share, Balance at March 31, 2023 | $ / shares	9.08
Weighted average exercise price per share, Vested and expected to vest as of March 31, 2022 | $ / shares	9.08
Weighted average exercise price per share, Expected to vest at March 31, 2023 | $ / shares	$ 9.35
Weighted average remaining contractual term (Years)	8 years 8 months 26 days
Weighted average remaining contractual term, Vested and expected to vest as of March 31, 2023	8 years 8 months 26 days
Weighted average remaining contractual term, Vested and exercisable at March 31, 2023	8 years 2 months 8 days
Aggregate intrinsic value, Balance at March 31, 2023 | $	$ 9,552
Vested and expected to vest as of March 31, 2023 | $	9,552
Aggregate intrinsic value, Vested and exercisable at March 31, 2023 | $	$ 2,391

Preferred Stock and Stockhold_5

Preferred Stock and Stockholders' Equity (Deficit) - Summary of RSU Equity incentive plans (Details) - $ / shares	3 Months Ended
	Mar. 31, 2023	Dec. 31, 2022
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Granted	1,825,500
Expected to vest at March 31, 2023	10,100,577
Weighted average exercise price per share, Expected to vest at March 31, 2023	$ 9.35
Service Based RSU Member
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Nonvested at December 31, 2022	873,723	966,973
Granted	16,771
Vested	110,021
Nonvested at March 31, 2023	873,723	966,973
Expected to vest at March 31, 2023	873,723
Weighted Average Nonvested at December 31, 2022	$ 17.71	$ 17.81
Weight granted fair value Nonvested Granted	10.46
Weight granted fair value Nonvested Vested	17.48
Weighted Average Grant Nonvested at March 31, 2023	17.71	$ 17.81
Weighted average exercise price per share, Expected to vest at March 31, 2023	$ 17.71
Performance Based RSUs Member
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Nonvested at December 31, 2022	36,000	36,000
Nonvested at March 31, 2023	36,000	36,000
Weighted Average Nonvested at December 31, 2022	$ 3.08	$ 3.08
Weighted Average Grant Nonvested at March 31, 2023	$ 3.08	$ 3.08

Preferred Stock and Stockhold_6

Preferred Stock and Stockholders' Equity (Deficit) - Schedule of Stock-based Compensation Expense for All Equity Awards (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Class Of Stock [Line Items]
Total	$ 6,000	$ 4,550
Research and Development Expense [Member]
Class Of Stock [Line Items]
Total	2,414	1,687
General and Administrative [Member]
Class Of Stock [Line Items]
Total	$ 3,586	$ 2,863

Preferred Stock and Stockhold_7

Preferred Stock and Stockholders' Equity (Deficit) - Summary of Assumptions Used in Black-Scholes Model (Details)	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Class Of Stock [Line Items]
Risk-free rate of interest, Minimum	3.54%	1.43%
Risk-free rate of interest, Maximum	3.95%	2.12%
Expected stock price volatility, Minimum	87.60%	89.30%
Expected stock price volatility, Maximum	89.60%	118.10%
Dividend yield	0%	0%
Minimum [Member]
Class Of Stock [Line Items]
Expected term (years)	5 years 3 months 3 days	5 years 9 months 7 days
Maximum [Member]
Class Of Stock [Line Items]
Expected term (years)	6 years 1 month 2 days	6 years 29 days

Preferred Stock and Stockhold_8

Preferred Stock and Stockholders' Equity (Deficit) - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Class Of Stock [Line Items]
Common stock, shares authorized	500,000,000		500,000,000
Share based compensation expense	$ 6,000	$ 4,550
Common stock, shares issued	41,397,640		41,177,706
Common stock, shares outstanding	41,345,890		41,095,564
Aggregate intrinsic value of options exercised	$ 1,000	$ 4,300
Cash received for early exercise of unvested options	$ 100
Compensation expense recognition vesting period	2 years 8 months 12 days
Common stock reserved for issuance	14,815,969
Weighted-average grant date fair value of RSUs granted per share		$ 17.72
Preferred stock, shares outstanding	0		0
Preferred stock, shares authorized	50,000,000
2021 Stock Incentive Plan
Class Of Stock [Line Items]
Increase in common stock shares reserved for future issuance	2,058,885
Common stock, shares issued	50,000,000
Stock option granted maximum term	10 years
Percentage of exercise price to fair market value common stock on grant date	100%
Common stock reserved for issuance	4,600,000
Percentage of common stock outstanding	5%
Restricted Stock
Class Of Stock [Line Items]
Unrecognised compensation cost	$ 13,000
Restricted Stock Units
Class Of Stock [Line Items]
Convertible preferred stock issuance cost, net	$ 1,100	$ 0
Stock Options
Class Of Stock [Line Items]
Weighted-average grant date fair value	$ 6.75	$ 13.08
Stock Options | 2021 Stock Incentive Plan
Class Of Stock [Line Items]
Percentage of exercise price to fair market value common stock on grant date	110%
2021 Employee Stock Purchase Plan
Class Of Stock [Line Items]
Increase in common stock shares reserved for future issuance	411,777
Share based compensation expense	$ 100	$ 100
Common stock, shares issued	15,000,000
Unrecognised compensation cost	$ 51,000
Common stock reserved for issuance	400,000
Number of purchased shares by the employee	0	0

Income Taxes (Additional Inform

Income Taxes (Additional Information) (Details)	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Income Tax Disclosure [Abstract]
Effective Income Tax Rate	0%	0%
Difference Between Effective Tax Rate	0%	0%
Federal Statutory Rate	21%	21%

Employee Savings Plan - Additio

Employee Savings Plan - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Defined Contribution Plan Disclosure [Line Items]
Employer discretionary contribution amount	$ 0	$ 0
Maximum [Member]
Defined Contribution Plan Disclosure [Line Items]
Percent of employees gross pay	90%