Tenaya Therapeutics (TNYA) 10-Q 10 Nov 21 2021 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2021	Nov. 01, 2021
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Entity Registrant Name	TENAYA THERAPEUTICS, INC.
Entity Central Index Key	0001858848
Entity File Number	001-40656
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	81-3789973
Entity Address, Address Line One	171 Oyster Point Boulevard
Entity Address, Address Line Two	5th Floor
Entity Address, City or Town	South San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94080
City Area Code	650
Local Phone Number	825-6900
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Title of 12(b) Security	Common Stock, par value $0.0001 per share
Trading Symbol	TNYA
Security Exchange Name	NASDAQ
Document Quarterly Report	true
Document Transition Report	false
Entity Common Stock, Shares Outstanding		41,281,210

Condensed Balance Sheets (Unaud

Condensed Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 117,077	$ 128,535
Investments in marketable securities	163,388
Prepaid expenses and other current assets	4,357	1,429
Total current assets	284,822	129,964
Property and equipment, net	30,891	17,185
Operating lease right-of-use assets	12,006
Restricted cash, non-current	547	547
Other non-current assets	3,528	465
Total assets	331,794	148,161
Current liabilities:
Accounts payable	6,171	1,017
Accrued expenses and other current liabilities	5,607	3,161
Deferred rent and other lease liabilities, current		863
Operating lease liabilities, current	1,914
Total current liabilities	13,692	5,041
Deferred rent and other lease liabilities, non-current		3,662
Operating lease liabilities, non-current	14,307
Other non-current liabilities	96	19
Total liabilities	28,095	8,722
Commitments and contingencies (Note 6)
Convertible preferred stock		220,754
Stockholders’ equity (deficit):
Common stock	4
Additional paid-in capital	433,112	1,584
Notes receivable from stockholders	(12)	(87)
Accumulated other comprehensive loss	(23)
Accumulated deficit	(129,382)	(82,812)
Total stockholders’ equity (deficit)	303,699	(81,315)
Total liabilities, convertible preferred stock and stockholders’ equity (deficit)	$ 331,794	$ 148,161

Condensed Statements of Operati

Condensed Statements of Operations and Comprehensive Loss (Unaudited) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Operating expenses:
Research and development	$ 12,944,000	$ 8,480,000	$ 33,440,000	$ 22,735,000
General and administrative	5,356,000	1,972,000	13,202,000	5,855,000
Total operating expenses	18,300,000	10,452,000	46,642,000	28,590,000
Loss from operations	(18,300,000)	(10,452,000)	(46,642,000)	(28,590,000)
Other income (expense), net:
Interest income	23,000	7,000	41,000	82,000
Change in fair value of convertible preferred stock tranche liability		151,000		75,000
Other income (expense), net	15,000	(1,000)	31,000	356,000
Total other income (expense), net	38,000	157,000	72,000	513,000
Net loss before income tax expense	(18,262,000)	(10,295,000)	(46,570,000)	(28,077,000)
Income tax expense	0	0	0	0
Net loss	(18,262,000)	(10,295,000)	(46,570,000)	(28,077,000)
Other comprehensive loss:
Unrealized loss on marketable securities	(23,000)		(23,000)
Comprehensive loss	$ (18,285,000)	$ (10,295,000)	$ (46,593,000)	$ (28,077,000)
Net loss per share, basic and diluted	$ (0.68)	$ (10.29)	$ (4.75)	$ (29.65)
Weighted-average shares used in computing net loss per share, basic and diluted	26,895,716	1,000,052	9,808,162	947,009

Condensed Statements of Convert

Condensed Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Unaudited) - USD ($) $ in Thousands	Total	Convertible Preferred Stock	Series C Convertible Preferred Stock	Series B Convertible Preferred Stock	Common Stock	Additional Paid-In Capital	Notes Receivable from Stockholders	Accumulated Other Comprehensive Loss	Accumulated Deficit
Temporary equity balance, shares at Dec. 31, 2019		11,403,077
Temporary equity, balance at Dec. 31, 2019		$ 73,042
Balance, shares at Dec. 31, 2019					1,193,488
Balance at Dec. 31, 2019	$ (43,739)					$ 764	$ (86)		$ (44,417)
Issuance of convertible preferred stock, net of issuance costs				$ 30,671
Issuance of convertible preferred stock, net of issuance costs, shares				3,086,415
Issuance of common stock upon exercise of stock options	3					3
Issuance of common stock upon exercise of stock options, shares					3,333
Repurchase of common stock related to early exercise of options, shares					(612)
Vesting of early exercised stock options	11					11
Notes receivable from stockholders	1						1
Stock-based compensation	154					154
Net loss	(9,051)								(9,051)
Balance at Mar. 31, 2020	(52,621)					932	(85)		(53,468)
Temporary equity balance, shares at Mar. 31, 2020		14,489,492
Temporary equity, balance at Mar. 31, 2020		$ 103,713
Balance, shares at Mar. 31, 2020					1,196,209
Temporary equity balance, shares at Dec. 31, 2019		11,403,077
Temporary equity, balance at Dec. 31, 2019		$ 73,042
Balance, shares at Dec. 31, 2019					1,193,488
Balance at Dec. 31, 2019	(43,739)					764	(86)		(44,417)
Net loss	(28,077)
Balance at Sep. 30, 2020	(71,228)					1,351	(85)		(72,494)
Temporary equity balance, shares at Sep. 30, 2020		17,575,907
Temporary equity, balance at Sep. 30, 2020		$ 135,037
Balance, shares at Sep. 30, 2020					1,202,169
Temporary equity balance, shares at Mar. 31, 2020		14,489,492
Temporary equity, balance at Mar. 31, 2020		$ 103,713
Balance, shares at Mar. 31, 2020					1,196,209
Balance at Mar. 31, 2020	(52,621)					932	(85)		(53,468)
Issuance of common stock upon exercise of stock options	2					2
Issuance of common stock upon exercise of stock options, shares					1,793
Vesting of early exercised stock options	11					11
Stock-based compensation	185					185
Net loss	(8,731)								(8,731)
Balance at Jun. 30, 2020	(61,154)					1,130	(85)		(62,199)
Temporary equity balance, shares at Jun. 30, 2020		14,489,492
Temporary equity, balance at Jun. 30, 2020		$ 103,713
Balance, shares at Jun. 30, 2020					1,198,002
Issuance of convertible preferred stock, net of issuance costs		$ 31,324
Issuance of convertible preferred stock, net of issuance costs, shares		3,086,415
Issuance of common stock upon exercise of stock options	12					12
Issuance of common stock upon exercise of stock options, shares					4,583
Repurchase of common stock related to early exercise of options, shares					(416)
Vesting of early exercised stock options	11					11
Stock-based compensation	198					198
Net loss	(10,295)								(10,295)
Balance at Sep. 30, 2020	$ (71,228)					1,351	(85)		(72,494)
Temporary equity balance, shares at Sep. 30, 2020		17,575,907
Temporary equity, balance at Sep. 30, 2020		$ 135,037
Balance, shares at Sep. 30, 2020					1,202,169
Temporary equity balance, shares at Dec. 31, 2020	24,493,528	24,493,528	6,917,621	9,259,245
Temporary equity, balance at Dec. 31, 2020	$ 220,754	$ 220,754	$ 85,717	$ 91,644
Balance, shares at Dec. 31, 2020					1,210,306
Balance at Dec. 31, 2020	(81,315)					1,584	(87)		(82,812)
Issuance of convertible preferred stock, net of issuance costs			$ 19,981
Issuance of convertible preferred stock, net of issuance costs, shares			1,608,750
Issuance of common stock upon exercise of stock options	29					29
Issuance of common stock upon exercise of stock options, shares					12,508
Repurchase of common stock related to early exercise of options, shares					(365)
Vesting of early exercised stock options	9					9
Stock-based compensation	432					432
Net loss	(13,098)								(13,098)
Balance at Mar. 31, 2021	$ (93,943)					2,054	(87)		(95,910)
Temporary equity balance, shares at Mar. 31, 2021		26,102,278
Temporary equity, balance at Mar. 31, 2021		$ 240,735
Balance, shares at Mar. 31, 2021					1,222,449
Temporary equity balance, shares at Dec. 31, 2020	24,493,528	24,493,528	6,917,621	9,259,245
Temporary equity, balance at Dec. 31, 2020	$ 220,754	$ 220,754	$ 85,717	$ 91,644
Balance, shares at Dec. 31, 2020					1,210,306
Balance at Dec. 31, 2020	(81,315)					1,584	(87)		(82,812)
Net loss	(46,570)
Balance at Sep. 30, 2021	303,699				$ 4	433,112	(12)	$ (23)	(129,382)
Balance, shares at Sep. 30, 2021					41,280,402
Temporary equity balance, shares at Mar. 31, 2021		26,102,278
Temporary equity, balance at Mar. 31, 2021		$ 240,735
Balance, shares at Mar. 31, 2021					1,222,449
Balance at Mar. 31, 2021	(93,943)					2,054	(87)		(95,910)
Issuance of common stock upon exercise of stock options	31					31
Issuance of common stock upon exercise of stock options, shares					12,173
Repurchase of common stock related to early exercise of options, shares					(11,980)
Vesting of early exercised stock options	9					9
Notes receivable from stockholders	75						75
Stock-based compensation	502					502
Net loss	(15,210)								(15,210)
Balance at Jun. 30, 2021	(108,536)					2,596	(12)		(111,120)
Temporary equity balance, shares at Jun. 30, 2021		26,102,278
Temporary equity, balance at Jun. 30, 2021		$ 240,735
Balance, shares at Jun. 30, 2021					1,222,642
Temporary equity, Conversion of convertible preferred stock to common stock upon completion of initial public offering		$ (240,735)
Temporary equity, Conversion of convertible preferred stock to common stock upon completion of initial public offering, shares		(26,102,278)
Conversion of convertible preferred stock to common stock upon completion of initial public offering, shares					26,102,278
Conversion of convertible preferred stock to common stock upon completion of initial public offering	240,735				$ 3	240,732
Issuance of common stock upon initial public offering, net of issuance costs	188,541				$ 1	188,540
Issuance of common stock upon initial public offering, net of issuance costs, shares					13,800,000
Issuance of common stock upon exercise of stock options	268					268
Issuance of common stock upon exercise of stock options, shares					160,096
Repurchase of common stock related to early exercise of options, shares					(4,614)
Vesting of early exercised stock options	8					8
Stock-based compensation	968					968
Other comprehensive loss	(23)							(23)
Net loss	(18,262)								(18,262)
Balance at Sep. 30, 2021	$ 303,699				$ 4	$ 433,112	$ (12)	$ (23)	$ (129,382)
Balance, shares at Sep. 30, 2021					41,280,402

Condensed Statements of Conve_2

Condensed Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Mar. 31, 2020
Initial Public Offering
Stock issuance costs	$ 18,459
Series C Convertible Preferred Stock
Stock issuance costs		$ 20
Series B Convertible Preferred Stock
Stock issuance costs			$ 26	$ 23
Partial settlement of stock, tranche liability			$ 684	$ 27

Condensed Statements of Cash Fl

Condensed Statements of Cash Flows (Unaudited) $ in Thousands	9 Months Ended
	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)
Cash flows from operating activities:
Net loss	$ (46,570)	$ (28,077)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	2,170	1,825
Amortization of premium on marketable securities	6
Stock-based compensation	1,902	537
Loss on disposal of property and equipment	4	35
Non-cash operating lease expense	743
Change in fair value of convertible preferred stock tranche liability		(75)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(3,029)	304
Other non-current assets	(3,063)	(168)
Accounts payable	2,518	527
Accrued expenses and other current liabilities	1,729	642
Deferred rent and other lease liabilities		(572)
Operating lease liabilities	(952)
Other non-current liabilities	77	(24)
Net cash used in operating activities	(44,465)	(25,046)
Cash flows from investing activities:
Purchases of property and equipment	(12,567)	(1,586)
Purchases of marketable securities	(163,417)
Proceeds from maturities of marketable securities		2,753
Net cash (used in) provided by investing activities	(175,984)	1,167
Cash flows from financing activities:
Proceeds from initial public offering, net of issuance costs	188,605
Proceeds from exercise of stock options	343	17
Repurchases of common stock	(13)	(1)
Proceeds from repayments on notes receivable from stockholders	75
Net cash provided by financing activities	208,991	61,344
Net change in cash, cash equivalents and restricted cash	(11,458)	37,465
Cash and cash equivalents and restricted cash at beginning of period	129,082	24,271
Cash and cash equivalents and restricted cash at end of period	117,624	61,736
Components of cash, cash equivalents and restricted cash:
Cash and cash equivalents	117,077	61,337
Restricted cash, non-current	547	399
Cash, cash equivalents and restricted cash	117,624	61,736
Supplemental disclosure of cash operating activities:
Cash paid for leases included in operating cash outflows	4,423
Supplemental disclosure of non-cash operating activities:
Lease liability obtained in exchange for right-of-use asset	8,558
Supplemental disclosure of non-cash investing and financing activities:
Conversion of convertible preferred stock to common stock upon completion of initial public offering	220,754
Offering costs related to initial public offering included in accounts payable and accrued expenses and other current liabilities	64
Property and equipment included in accounts payable and accrued expenses and other current liabilities	3,677
Series B Convertible Preferred Stock
Cash flows from financing activities:
Proceeds from issuance of convertible preferred stock, net of issuance costs		61,328
Supplemental disclosure of non-cash investing and financing activities:
Settlement of convertible preferred stock tranche liability in connection with the issuance of Series B convertible preferred stock		711
Offering costs related to Series B convertible preferred stock in accrued expenses and other current liabilities		$ 44
Series C Convertible Preferred Stock
Cash flows from financing activities:
Proceeds from issuance of convertible preferred stock, net of issuance costs	$ 19,981

Organization and Description of

Organization and Description of the Business	9 Months Ended
	Sep. 30, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization and Description of the Business	1. Organization and Description of the Business Description of the Business Tenaya Therapeutics, Inc. (the “Company”) was incorporated in the state of Delaware in August 2016 and is headquartered in South San Francisco, California. The Company is a preclinical stage biotechnology company focused on discovering, developing and delivering curative therapies that address the underlying drivers of heart disease. The Company is advancing product candidates from three distinct but interrelated product platforms: gene therapy, cellular regeneration and precision medicine. Reverse Stock Split In July 2021, the Company’s board of directors approved an amended and restated certificate of incorporation to effect a reverse split of shares of the Company’s common stock, convertible preferred stock, and authorized shares on a 1-for-6 basis (the “Reverse Stock Split”) effective on July 23, 2021. The par value of the common stock and convertible preferred stock was not adjusted as a result of the Reverse Stock Split. All share data, per share data and related information for all periods presented in the accompanying condensed financial statements have been retrospectively adjusted to reflect the effect of the Reverse Stock Split. Initial Public Offering On August 3, 2021, the Company completed its initial public offering (“IPO”), at which time the Company issued an aggregate of 13,800,000 shares of its common stock (inclusive of 1,800,000 shares pursuant to the underwriters’ overallotment option) at a price of $15.00 per share. The Company received net proceeds of $188.5 million, after deducting underwriting discounts and commissions of $14.5 million and other offering expenses of $4.0 million. Immediately prior to the completion of the IPO, all of the Company’s outstanding shares of convertible preferred stock automatically converted into 26,102,278 shares of common stock. Liquidity The Company has incurred net losses since inception and expects such losses to continue in the future as it conducts research and development activities. As of September 30, 2021, the Company had an accumulated deficit of $129.4 million. The Company incurred a net loss of $46.6 million and $28.1 million during the nine months ended September 30, 2021 and 2020. The Company had $280.5 million of cash, cash equivalents and investments in marketable securities as of September 30, 2021. Management recognizes the need to raise additional capital to fully implement its business plan. The Company may seek to raise capital through equity financings, debt financings, license agreements, collaborative agreements or other sources of financing. Management believes that its existing cash, cash equivalents and investments in marketable securities as of September 30, 2021 will be sufficient to fund the Company’s operations for at least the next twelve months following the date these condensed financial statements are filed with the Securities and Exchange Commission (“SEC”).

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The accompanying condensed financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) and follow the requirements of the SEC for interim reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by GAAP can be condensed or omitted. The interim condensed balance sheet as of September 30, 2021, the interim condensed statements of operations and comprehensive loss, convertible preferred stock and stockholders’ equity (deficit) for the three and months ended September 30, 2021 and 2020 and the interim condensed statements of cash flows for the nine months ended September 30, 2021 and 2020 are unaudited. These unaudited interim condensed financial statements have been prepared on the same basis as the Company’s annual financial statements and reflect all adjustments (consisting only of normal recurring adjustments) that are necessary for the fair statement of the Company’s financial position, results of operations and cash flows for the interim periods presented. The condensed results of operations for the three and months ended September 30, 2021 are not necessarily indicative of the results to be expected for the full year or for any other future annual or interim period. The condensed balance sheet as of December 31, 2020 included herein was derived from the audited financial statements as of that date. These condensed financial statements should be read in conjunction with the Company’s audited financial statements included in the prospectus dated July 29 , 20 2 1 , that forms a part of the Company's Registration Statements on Form S-1 (File Nos. 333-2 5 7820 and 333-2 58285 ), as filed with the SEC pursuant to Rule 424 promulgated under the Securities Act of 1933, as amended . Use of Estimates The preparation of condensed financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, and the disclosure of contingent assets and liabilities at the date of the condensed financial statements and the reported amounts of expenses during the reporting period. Significant estimates and assumptions made in the accompanying condensed financial statements include, but are not limited to, the fair value of common stock, the valuation of equity-based awards, the useful lives of property and equipment, the fair value of the convertible preferred stock tranche liability, accrued expenses related to research and development activities and the valuation allowance for deferred tax assets. The Company bases its estimates on historical experience, the current economic environment, and on various other assumptions that are believed to be reasonable under the circumstances. Actual results may differ from those estimates or assumptions. Cash and Cash Equivalents The Company considers all highly liquid investments purchased with an original maturity of three months or less on the date of purchase to be cash equivalents. Cash equivalents primarily consist of money market funds, commercial paper and U.S. government agencies bonds that are stated at fair value. Marketable Securities The Company invests in marketable securities, primarily securities issued by the U.S. government and its agencies, commercial paper and corporate bonds. All marketable securities have been classified as available-for-sale and are carried at estimated fair value as determined based upon quoted market prices or pricing models for similar securities. Management determines the appropriate classification of its marketable debt securities at the time of purchase and reevaluates such designation at each balance sheet date. Unrealized gains and losses are excluded from earnings and are reported as a component of other comprehensive loss. Realized gains and losses and declines in fair value judged to be other than temporary, if any, on available-for-sale securities are included in other income (expense), net. There are no material realized gains or losses on marketable securities for all periods presented. The cost of securities sold is based on the specific-identification method. Interest earned on marketable securities is included in interest income. Leases The Company adopted Accounting Standards Codification (“ASC”) Topic 842, Leases Operating lease right-of-use (“ROU”) assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Operating lease ROU assets and liabilities are recognized based on the present value of lease payments over the lease term at the commencement date of the lease. ROU assets also include any initial direct costs incurred and any lease payments made at or before the lease commencement date, less any lease incentive received. The Company uses the rate implicit in the lease in determining the present value of lease payments and, if that rate is not readily determinable, the Company uses its incremental borrowing rate based on the information available at the date of lease commencement. The incremental borrowing rate reflects the rate of interest that a lessee would have to pay to borrow, on a collateralized basis over a similar term, an amount equal to the lease payments in a similar economic environment. The Company’s lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Lease expense for lease payments is recognized on a straight-line basis over the lease term. The Company’s non-lease components are primarily related to property taxes, insurance, and common area maintenance, which vary based on future outcomes, and are recognized as rent expense when incurred. Asset Retirement Obligation The Company records asset retirement obligations (“AROs”) for the estimated cost of removing constructed leasehold improvement assets and restoring the leased premises back to their original condition, at the time when the contractual obligations are incurred. AROs represent the present value of the expected costs for the related restoration activities. The ARO assets and liabilities are recorded in property, plant and equipment and other long-term liabilities, respectively, in the Company’s balance sheets. The Company records accretion expense, which represents the increase in the asset retirement obligations, over the remaining or operational life of the associated leasehold improvements. Accretion expense is recorded as operating expense in the statements of operations using an accretion rate based on the credit adjusted risk-free interest rate. Changes resulting from revisions to the timing or amount of the original estimate of cash flows are recognized as an increase or a decrease in the asset retirement cost, or income when the asset retirement cost is depleted. Net Loss Per Share Basic net loss per share is calculated by dividing the net loss by the weighted-average number of shares of the Company’s common stock outstanding for the period, without consideration for potential dilutive shares of common stock. As the Company is in a loss position for the periods presented, diluted net loss per share is the same as basic net loss per share, since the effects of potentially dilutive securities are antidilutive. Shares related to early exercised stock options and restricted stock that are subject to repurchase are excluded from the basic and diluted net loss per share calculation until the Company’s repurchase right lapses. Recently Adopted Accounting Standards On January 1, 2021, the Company adopted ASC 842 using the modified retrospective transition method and elected the practical expedients to not reassess whether any expired or existing contracts are or contain leases, carry forward its historical lease classification and not reassess initial direct costs for existing leases. The Company elected to not separate non-lease components from the associated lease components and to not recognize ROU assets and lease liabilities for leases with a term of twelve months or less. Upon adoption of ASC 842, the Company recorded an operating right-of-use asset of $4.6 million, operating lease liabilities of $9.1 million and derecognized deferred rent and other lease liabilities of $4.5 million. Results for the nine months ended September 30, 2021 are presented under ASC 842. Prior period amounts before January 1, 2021 have not been adjusted and continue to be reported in accordance with the Company’s historical accounting under previous lease guidance, ASC 840: Leases (Topic 840) Recently Issued Accounting Pronouncements Not Yet Adopted In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments which replaces the existing incurred loss impairment model with an expected credit loss model In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes In August 2020, the FASB issued ASU No. 2020-06, Debt— Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40) (“ASU 2020-06”), which is intended to simplify the accounting for convertible debt instruments and convertible preferred stock. This standard removes the existing guidance in ASC 470-20 that requires companies to account for cash conversion features and beneficial conversion features in equity, separately from the host convertible debt or preferred stock. As an emerging growth company, ASU 2020-06 is effective for the Company beginning January 1, 2024. The Company currently does not expect the adoption of this standard to have a material impact on its financial statements.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2021
Fair Value Disclosures [Abstract]
Fair Value Measurements	3. Fair Value Measurements Financial assets and liabilities are recognized at fair value on a recurring basis. Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability (an exit price) in an orderly transaction between market participants at the reporting date. The accounting guidance establishes a three-tiered hierarchy, which prioritizes the inputs used in the valuation methodologies in measuring fair value as follows: Level 1 - Inputs are unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date. Level 2 - Inputs other than quoted market prices included in Level 1 are either directly or indirectly observable for the asset or liability through correlation with market data at the measurement date and for the duration of the instrument’s anticipated life. Level 3 - Inputs reflect management’s best estimate of what market participants would use in pricing the asset or liability at the measurement date. Consideration is given to the risk inherent in the valuation technique and the risk inherent in the inputs to the model. The following tables summarize the Company’s financial assets measured at fair value on a recurring basis by level within the fair value hierarchy: September 30, 2021 Valuation Hierarchy Amortized Cost Unrealized Gain Unrealized Loss Fair Value (In thousands) Assets: Cash equivalents: Money market funds Level 1 $ 68,815 $ — $ — $ 68,815 Commercial paper Level 2 44,246 — — 44,246 Government agencies bonds Level 2 3,015 — — 3,015 Marketable securities: U.S. treasuries Level 1 40,677 — (9 ) 40,668 Commercial paper Level 2 109,095 3 (12 ) 109,086 Corporate bonds Level 2 9,036 — (4 ) 9,032 Government agencies bonds Level 2 4,603 — (1 ) 4,602 Total financial assets $ 279,487 $ 3 $ (26 ) $ 279,464 December 31, 2020 Valuation Hierarchy Amortized Cost Unrealized Gain Unrealized Loss Fair Value (In thousands) Assets: Cash equivalents: Money market funds Level 1 $ 127,535 $ — $ — $ 127,535 Total financial assets $ 127,535 $ — $ — $ 127,535 Money market funds are classified as Level 1 because they are valued using quoted market prices in active markets for identical assets. Financial instruments classified within Level 2 of the fair value hierarchy are valued based on observable inputs or can be derived from non-binding quotes from the Company’s investment managers, which are based on proprietary valuation models of independent pricing services. These models generally use inputs such as observable market data, quoted market prices for similar instruments, or historical pricing trends of a security relative to its peers. To validate the fair value determination provided by its investment managers, the Company reviews the pricing movement in the context of overall market trends and trading information from its investment managers. In addition, the Company considers the inputs and methods used in determining the fair value in order to determine the classification of securities in the fair value hierarchy. The Company believes it is more likely than not that its marketable securities in an unrealized loss position will be held until maturity or the recovery of the cost basis of the investment. To date, the Company has not recorded any impairment charges on marketable securities related to other-than-temporary declines in market value. All available-for-sale marketable securities held as of September 30, 2021 are short-term investments with contractual maturities of less than one year. Convertible Preferred Stock Tranche Liability The Company’s convertible preferred stock tranche liability (see Note 7) was determined based on significant inputs not observable in the market, which represents a Level 3 measurement within the fair value hierarchy. Fair value was calculated using an option pricing model that required significant unobservable inputs supported by little or no market activity. The convertible preferred stock tranche liability is considered a non-contingent forward and the standard forward pricing model was used with the following key assumptions: (a) calculation of an expected term and (b) a risk-free interest rate The following table summarizes the significant unobservable assumptions used to value the convertible preferred stock tranche liability as of the settlement date of August 24, 2020: August 24, 2020 Term to valuation date (in years) 0.00 Discount rate 5.0% The following table summarizes the changes in the estimated fair value of the Company’s convertible preferred stock tranche liability measured on a recurring basis using significant Level 3 inputs: Nine Months Ended September 30, 2020 (In thousands) Beginning balance $ 786 Change in fair value upon remeasurement (75 ) Settlement of convertible preferred stock tranche liability on second and third closings of the Series B convertible preferred stock (711 ) Ending balance $ —

Balance Sheet Components

Balance Sheet Components	9 Months Ended
	Sep. 30, 2021
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Components	4 . Balance Sheet Components Property and Equipment, Net Property and equipment, net consists of the following: September 30, 2021 December 31, 2020 (In thousands) Construction in progress $ 21,895 $ 7,678 Laboratory equipment 9,806 8,182 Leasehold improvements 7,242 7,237 Furniture and fixtures 534 534 Computer equipment and software 272 257 Total property and equipment $ 39,749 $ 23,888 Less: accumulated depreciation and amortization (8,858 ) (6,703 ) Total property and equipment, net $ 30,891 $ 17,185 Depreciation and amortization expense for the three months ended September 30, 2021 and 2020 was $0.7 million and $0.6 million, respectively. Depreciation and amortization expense for the nine months ended September 30, 2021 and 2020 was $2.2 million and $1.8 million, respectively. Construction in progress primarily consists of capitalized machinery and equipment that is expected to be placed in service in the Company’s manufacturing and office space located in Union City, California (see Note 6). Accrued Expenses and Other Current Liabilities Accrued expenses and other current liabilities consist of the following: September 30, 2021 December 31, 2020 (In thousands) Accrued compensation and related expenses $ 2,663 $ 2,090 Accrued research and development expenses 1,043 391 Accrued property and equipment 972 231 Other current liabilities 514 121 Accrued professional services 415 328 Total accrued expenses and other current liabilities $ 5,607 $ 3,161

License Agreements

License Agreements	9 Months Ended
	Sep. 30, 2021
License Agreements [Abstract]
License Agreements	5. License Agreements Gladstone License Agreement In October 2016, the Company entered into a license agreement with the J. David Gladstone Institute (Gladstone), pursuant to which Gladstone granted the Company a worldwide, royalty-bearing exclusive patent license and a non-exclusive technology license to develop and commercialize certain products for certain diseases (“Gladstone License Agreement”). Pursuant to the Gladstone License Agreement, the Company is obligated, among other things, to pay Gladstone (i) annual license maintenance fees ranging from $25,000 up to $0.1 million per year, which will be creditable against royalties paid in the following twelve month period, (ii) milestone payments up to $4.1 million for royalty-bearing products directed to a particular target, which are contingent upon achieving specific clinical and commercialization milestone events, and (iii) tiered low-single digit royalties on future net sales of each royalty-bearing product. Under the agreement, the Company is subject to diligence requirements to develop and commercialize at least one royalty-bearing product. The Company may pay $50,000 to $100,000 to extend the deadline for its diligence milestone obligations for up to four additional one-year During the three and nine months ended September 30, 2020 and 2021, there were no material amounts recorded related to annual license fees payable pursuant to the Gladstone License Agreement. University of Texas Southwestern License Agreement In January 2020, the Company entered into a license agreement with the University of Texas Southwestern (“UTSW License”), pursuant to which UTSW granted the Company a royalty-bearing exclusive and sublicensable patent license and a non-exclusive, non-sublicensable license for mutually agreed upon development activities. Under the UTSW License, the Company is obligated to pay UTSW (i) a non-refundable upfront license fee of $0.1 million, (ii) milestone payments up to a total of $14.8 million in aggregate, which are contingent upon achieving specific development and commercialization milestone events, and (iii) royalties on future net sales of each royalty-bearing product ranging in the low-single digits. As of September 30, 2021, the Company has not recognized any milestone and royalty payments under the UTSW License. During the three and nine months ended September 30, 2020, the Company recorded research and development expenses of $nil and $0.1 million related to the upfront license fee payable pursuant to the UTSW License. Other License Agreements In addition to the agreements described above, the Company has also entered into other license agreements with various institutions and business entities, none of which are material individually or in the aggregate.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2021
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	6 . Commitments and Contingencies Facility Leases In December 2016, the Company entered into a lease agreement for office and laboratory space in South San Francisco, California. The lease expires in May 2025 and the Company may renew the lease term for two additional five-year In December 2020, the Company entered into a short-term sublease agreement for additional office and laboratory space in South San Francisco, California that expires on November 30, 2021. In February 2021, the Company entered into a lease agreement for manufacturing and office space located in Union City, California. The lease commenced in May 2021 and has a ten-year five-year On January 1, 2021, the Company adopted ASC 842 and the following disclosures as of and for the three and nine months ended September 30, 2021 are presented under ASC 842. As of September 30, 2021, the remaining weighted-average lease term was 6.8 years and the weighted-average incremental borrowing rate used to determine the operating lease liabilities was 9.5%. For the three months ended September 30, 2021, the Company incurred $1.6 million of lease costs, of which $0.6 million is related to the Company’s short-term lease and $0.4 million is related to variable lease payments. For the three months ended September 30, 2020, the Company incurred $0.6 million in rent expense. For the nine months ended September 30, 2021, the Company incurred $4.2 million of lease costs, of which $1.8 million is related to the Company’s short-term lease and $1.2 million is related to variable lease payments. For the nine months ended September 30, 2020, the Company incurred $1.9 million in rent expense. As of September 30, 2021, the undiscounted future minimum lease payments due under the Company’s non-cancelable operating leases are as follows: Amount (In thousands) 2021 (remaining 3 months) $ 902 2022 3,678 2023 3,792 2024 3,910 2025 2,445 Thereafter 8,291 Total undiscounted future minimum lease payments $ 23,018 Present value adjustment for minimum lease commitments (6,515 ) Tenant improvement receivable (282 ) Total operating lease liabilities $ 16,221 As of December 31, 2020, undiscounted future minimum lease payments due under the Company’s non-cancelable operating lease are as follows: Amount (In thousands) 2021 $ 3,752 2022 2,206 2023 2,283 2024 2,363 2025 999 Total future minimum lease payments $ 11,603 The Company has previously entered into agreements to sublease portions of the Company’s facilities in South San Francisco to two different subtenants, both of which expired as of December 31, 2020. Pursuant to the sublease agreements, the Company received sublease income of $nil and $0.2 million during the three and nine months ended September 30, 2020, which is included in other income (expense), net on the condensed statements of operations and comprehensive loss. Asset Retirement Obligation Under the lease agreement for the manufacturing and office facility in Union City, the Company is contractually obligated to remove constructed leasehold improvements related to capitalized machinery and equipment (see Note 4) and to restore the leased space to its original condition upon termination of the lease agreement. The Company applies the proportionate method to account for the buildup of the asset retirement obligation while leasehold improvements are in progress. As of September 30, 2021, the balance of the asset retirement obligation liability was not material. The Company elected to defer the commencement of accretion of the asset retirement obligation until the underlying construction is completed, on the basis that the financial statement impact from the deferral is immaterial. Purchase Commitments The Company enters into contractual agreements with various suppliers in the normal course of its business, including vendors that provide machinery and equipment. All contracts are terminable, with varying provisions regarding termination. If a contract with a specific vendor were to be terminated, the Company would only be obligated for the products or services that the Company had received through the time of termination. Indemnification In the normal course of business, the Company enters into agreements that may include indemnification provisions. Pursuant to such agreements, the Company may indemnify, hold harmless and defend an indemnified party for losses suffered or incurred by the indemnified party. In some cases, the indemnification will continue after the termination of the agreement. The maximum potential amounts of future payments the Company could be required to make under these provisions is not determinable. In addition, the Company has entered into indemnification agreements with its directors and certain officers that may require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors or officers. As of September 30, 2021 and December 31, 2020, the Company does not have any material indemnification claims that were probable or reasonably possible and, consequently, has not recorded any related liabilities.

Convertible Preferred Stock

Convertible Preferred Stock	9 Months Ended
	Sep. 30, 2021
Temporary Equity Disclosure [Abstract]
Convertible Preferred Stock	7 . Convertible Preferred Stock On August 3, 2021, immediately prior to the completion of the Company’s IPO, all outstanding shares of convertible preferred stock were converted into 26,102,278 shares of the Company’s common stock. Prior to the Company’s IPO, convertible preferred stock as of December 31, 2020 consists of the following: December 31, 2020 Shares Authorized Shares Issued and Outstanding Net Carrying Value Liquidation Preference (In thousands, except share data) Convertible Preferred Stock Series A 8,316,666 8,316,662 $ 43,393 $ 49,900 Series B 9,259,254 9,259,245 91,644 92,000 Series C 8,526,381 6,917,621 85,717 86,000 Total 26,102,301 24,493,528 $ 220,754 $ 227,900 The Company classifies its convertible preferred stock outside of total stockholders’ equity (deficit) because, in the event of certain change of control events that are not solely within the control of the Company (including liquidation, sale or transfer of the Company), the shares would become redeemable at the option of the holders. As a result, the Company classified its convertible preferred stock as mezzanine equity on the balance sheet as the preferred stock is contingently redeemable. Series B Convertible Preferred Stock Financing In August 2019, the Company entered into a Series B preferred stock purchase agreement (“Series B SPA”) for the issuance of up to 9,259,254 shares of the Company’s Series B convertible preferred stock at a purchase price of $9.936 per share in multiple closings. The Company completed the initial closing in August 2019, whereby 3,086,415 shares of Series B convertible preferred stock were issued for gross proceeds of $30.7 million. Pursuant to the Series B SPA, the Company was permitted to sell additional shares in subsequent closings contingent upon the approval of the Company’s board of directors. On issuance, the Company determined that its obligation to issue additional shares of Series B convertible preferred stock in future closings was a freestanding instrument that should be classified as a liability on the Company’s balance sheets. The freestanding financial instrument, or convertible preferred stock tranche liability, was recorded at fair value on issuance of $0.8 million with the remaining proceeds being allocated to the Series B convertible preferred stock. Any changes in fair value of the convertible preferred stock tranche liability in subsequent reporting periods are recognized as a component of other income (expense), net in the statements of operations and comprehensive loss (see Note 3). In March 2020, the Company completed its second closing of Series B convertible preferred stock financing and issued 3,086,415 shares of Series B convertible preferred stock at the fixed purchase price of $9.936 per share for gross proceeds of $30.7 million, thereby settling a portion of the convertible preferred stock tranche liability. Immediately prior to the second closing, the Company measured the convertible preferred stock tranche liability to its then fair value. Upon the closing of the second tranche, the convertible preferred stock tranche liability was partially settled and the related balance of the liability of $27,000 was reclassified to Series B convertible preferred stock. In August 2020, the Company completed its third closing of Series B convertible preferred stock financing and issued 3,086,415 shares of Series B convertible preferred stock at the purchase price of $9.936 per share for gross proceeds of $30.7 million, thereby settling the remainder of the convertible preferred stock tranche liability. Immediately prior to the third closing, the Company measured the convertible preferred stock tranche liability to its then fair value. Upon the closing of the third tranche, the remaining convertible preferred stock tranche liability was settled and the balance of the liability of $0.7 million was reclassified to Series B convertible preferred stock. Series C Convertible Preferred Stock Financing In December 2020, the Company entered into a Series C preferred stock purchase agreement (“Series C SPA”) for the issuance of up to 8,526,381 shares of the Company’s Series C convertible preferred stock at a purchase price of $12.432 per share in two closings. The Company completed the initial closing in December 2020, whereby 6,917,621 shares of Series C convertible preferred stock were issued for gross proceeds of $86.0 million. In January 2021, the Company sold an additional 1,608,750 shares of Series C convertible preferred stock at a purchase price of $12.432 per share for gross proceeds of $20.0 million.

Common Stock

Common Stock	9 Months Ended
	Sep. 30, 2021
Equity [Abstract]
Common Stock	8. Common Stock The holders of common stock are entitled to one vote per share on all matters to be voted on by the stockholders of the Company and are entitled to dividends, if and when declared by the board of directors, subject to the prior rights of the preferred stockholders. Common stock issued and outstanding on the condensed statements of convertible preferred stock and stockholders’ equity (deficit) includes shares related to early exercised options and restricted stock that are subject to repurchase. Common stock issued and outstanding is reduced for any repurchases of early exercised stock options and restricted stock. As of September 30, 2021 and December 31, 2020, outstanding common stock included 40,915 and 138,127 shares related to early exercised stock options and restricted stock that are unvested and subject to repurchase. Total shares of common stock reserved for issuance, on an as-if converted basis, is as follows: September 30, 2021 December 31, 2020 Conversion of outstanding shares of convertible preferred stock — 24,493,528 Stock options issued and outstanding 2,530,121 1,160,808 Stock options available for future grant 3,847,160 412,170 Total 6,377,281 26,066,506

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	9 . Stock-Based Compensation 2021 Equity Incentive Plan In July 2021, the Company adopted the 2021 Equity Incentive Plan (the “2021 Plan”), which became effective in connection with the IPO. The Company’s 2016 Equity Incentive Plan (the “2016 Plan”) was terminated in 2021. Shares subject to awards granted under the 2016 Plan that are repurchased by or forfeited to the Company will also be reserved for issuance under the 2021 Plan. The number of shares of common stock available for issuance under the 2021 Plan will automatically increase on the first day of January for a period of ten years, commencing on January 1, 2022, in an amount equal to the lesser of: 4,000,000 shares; 4% of the outstanding shares of the Company’s common stock as of the last day of the immediately preceding year; or such other amount as the Company’s board of directors may determine. Total shares reserved and available for grant under the 2021 Plan as of September 30, 2021 are 3,847,160. Stock Option Activity The following table summarizes stock option activity: Number of Options Outstanding Weighted- Average Exercise Price Per Share Weighted- Average Remaining Contractual Life Aggregate Intrinsic Value (Years) (In thousands) Outstanding as of December 31, 2020 1,160,808 $ 1.74 8.40 $ 6,060 Options granted 1,595,128 9.36 Options exercised (184,777 ) 1.85 Options cancelled (41,038 ) 3.51 Outstanding as of September 30, 2021 2,530,121 $ 6.50 8.87 $ 35,805 Exercisable as of September 30, 2021 590,000 $ 2.18 7.71 $ 10,898 2021 Employee Stock Purchase Plan In July 2021, the Company adopted the 2021 Employee Stock Purchase Plan (the “ESPP”), which became effective in connection with the IPO. The Company initially reserved 800,000 shares for future issuance under the ESPP. The ESPP permits participants to purchase common stock through payroll deductions of up to 15% of their eligible compensation. The number of shares of common stock available for issuance under the ESPP will automatically increase on the first day of January following the year in which the first offering period under the ESPP commences, in an amount equal to the lesser of: 800,000 shares; 1% of the outstanding shares of the Company’s common stock as of the last day of the immediately preceding year; or such other amount as the board of directors may determine. The first offering period has not commenced as of September 30, 2021 and there is no stock-based compensation related to the ESPP for the three and nine months ended September 30, 2021. Stock-Based Compensation The following table summarizes stock-based compensation recognized in the Company’s condensed statements of operations and comprehensive loss: Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 (In thousands) Research and development $ 326 $ 97 $ 654 $ 273 General and administrative 642 101 1,248 264 Total stock-based compensation $ 968 $ 198 $ 1,902 $ 537 As of September 30, 2021, there was approximately $14.3 million of unrecognized stock-based compensation, which the Company expects to recognize over a weighted-average period of 3.5 years. Stock Option Valuation The fair value of the Company’s stock option awards is estimated on the date of grant using the Black-Scholes option pricing model using the following assumptions: Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Expected term (in years) 6.0 - 6.1 6.0 5.0 - 6.1 6.0 - 6.1 Expected volatility 95% - 96% 183% 95% - 103% 178% - 183% Risk-free interest rate 0.9% - 1.2% 0.4% 0.6% - 1.2% 0.4% - 1.5% Expected dividend yield — % — % — % — % Restricted Stock A summary of restricted stock activity is as follows: Number of Shares Weighted Average Fair Value at Date of Grant per Share Unvested as of December 31, 2020 138,127 $ 0.90 Granted 19,852 $ 1.93 Vested (100,105 ) $ 0.56 Repurchased (16,959 ) $ 2.27 Unvested as of September 30, 2021 40,915 $ 1.67 Employee Recourse Notes In 2017 and 2018, the Company entered into full recourse notes with certain employees upon the exercise of stock options that are treated as substantive exercises for accounting purposes. The Company has the right to repurchase unvested shares up to 90 days after employment is terminated. As of September 30, 2021, the principal and accrued interest amount of the notes was $12,000. The notes are presented in the condensed statements of convertible preferred stock and stockholders’ equity (deficit).

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2021
Income Tax Disclosure [Abstract]
Income Taxes	1 0 . Income Taxes For the three and nine months ended September 30, 2021 and 2020, the Company did not record any income tax expense. The Company has recorded a full valuation allowance against its U.S. federal and state deferred tax assets as the Company believes it is not more likely than not that the benefit will be realized.

Net Loss Per Share

Net Loss Per Share	9 Months Ended
	Sep. 30, 2021
Earnings Per Share [Abstract]
Net Loss Per Share	11 . Net Loss Per Share The following potentially dilutive securities were not included in the calculation of diluted net loss per share as of the periods presented because the effect would have been anti-dilutive: September 30, 2021 2020 Convertible preferred stock — 17,575,907 Outstanding stock options 2,530,121 1,099,224 Restricted stock subject to future vesting 40,915 179,062 Total 2,571,036 18,854,193

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying condensed financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) and follow the requirements of the SEC for interim reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by GAAP can be condensed or omitted. The interim condensed balance sheet as of September 30, 2021, the interim condensed statements of operations and comprehensive loss, convertible preferred stock and stockholders’ equity (deficit) for the three and months ended September 30, 2021 and 2020 and the interim condensed statements of cash flows for the nine months ended September 30, 2021 and 2020 are unaudited. These unaudited interim condensed financial statements have been prepared on the same basis as the Company’s annual financial statements and reflect all adjustments (consisting only of normal recurring adjustments) that are necessary for the fair statement of the Company’s financial position, results of operations and cash flows for the interim periods presented. The condensed results of operations for the three and months ended September 30, 2021 are not necessarily indicative of the results to be expected for the full year or for any other future annual or interim period. The condensed balance sheet as of December 31, 2020 included herein was derived from the audited financial statements as of that date. These condensed financial statements should be read in conjunction with the Company’s audited financial statements included in the prospectus dated July 29 , 20 2 1 , that forms a part of the Company's Registration Statements on Form S-1 (File Nos. 333-2 5 7820 and 333-2 58285 ), as filed with the SEC pursuant to Rule 424 promulgated under the Securities Act of 1933, as amended .
Use of Estimates	Use of Estimates The preparation of condensed financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, and the disclosure of contingent assets and liabilities at the date of the condensed financial statements and the reported amounts of expenses during the reporting period. Significant estimates and assumptions made in the accompanying condensed financial statements include, but are not limited to, the fair value of common stock, the valuation of equity-based awards, the useful lives of property and equipment, the fair value of the convertible preferred stock tranche liability, accrued expenses related to research and development activities and the valuation allowance for deferred tax assets. The Company bases its estimates on historical experience, the current economic environment, and on various other assumptions that are believed to be reasonable under the circumstances. Actual results may differ from those estimates or assumptions.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments purchased with an original maturity of three months or less on the date of purchase to be cash equivalents. Cash equivalents primarily consist of money market funds, commercial paper and U.S. government agencies bonds that are stated at fair value.
Marketable Securities	Marketable Securities The Company invests in marketable securities, primarily securities issued by the U.S. government and its agencies, commercial paper and corporate bonds. All marketable securities have been classified as available-for-sale and are carried at estimated fair value as determined based upon quoted market prices or pricing models for similar securities. Management determines the appropriate classification of its marketable debt securities at the time of purchase and reevaluates such designation at each balance sheet date. Unrealized gains and losses are excluded from earnings and are reported as a component of other comprehensive loss. Realized gains and losses and declines in fair value judged to be other than temporary, if any, on available-for-sale securities are included in other income (expense), net. There are no material realized gains or losses on marketable securities for all periods presented. The cost of securities sold is based on the specific-identification method. Interest earned on marketable securities is included in interest income.
Leases	Leases The Company adopted Accounting Standards Codification (“ASC”) Topic 842, Leases Operating lease right-of-use (“ROU”) assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Operating lease ROU assets and liabilities are recognized based on the present value of lease payments over the lease term at the commencement date of the lease. ROU assets also include any initial direct costs incurred and any lease payments made at or before the lease commencement date, less any lease incentive received. The Company uses the rate implicit in the lease in determining the present value of lease payments and, if that rate is not readily determinable, the Company uses its incremental borrowing rate based on the information available at the date of lease commencement. The incremental borrowing rate reflects the rate of interest that a lessee would have to pay to borrow, on a collateralized basis over a similar term, an amount equal to the lease payments in a similar economic environment. The Company’s lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Lease expense for lease payments is recognized on a straight-line basis over the lease term. The Company’s non-lease components are primarily related to property taxes, insurance, and common area maintenance, which vary based on future outcomes, and are recognized as rent expense when incurred.
Asset Retirement Obligation	Asset Retirement Obligation The Company records asset retirement obligations (“AROs”) for the estimated cost of removing constructed leasehold improvement assets and restoring the leased premises back to their original condition, at the time when the contractual obligations are incurred. AROs represent the present value of the expected costs for the related restoration activities. The ARO assets and liabilities are recorded in property, plant and equipment and other long-term liabilities, respectively, in the Company’s balance sheets. The Company records accretion expense, which represents the increase in the asset retirement obligations, over the remaining or operational life of the associated leasehold improvements. Accretion expense is recorded as operating expense in the statements of operations using an accretion rate based on the credit adjusted risk-free interest rate. Changes resulting from revisions to the timing or amount of the original estimate of cash flows are recognized as an increase or a decrease in the asset retirement cost, or income when the asset retirement cost is depleted.
Net Loss Per Share	Net Loss Per Share Basic net loss per share is calculated by dividing the net loss by the weighted-average number of shares of the Company’s common stock outstanding for the period, without consideration for potential dilutive shares of common stock. As the Company is in a loss position for the periods presented, diluted net loss per share is the same as basic net loss per share, since the effects of potentially dilutive securities are antidilutive. Shares related to early exercised stock options and restricted stock that are subject to repurchase are excluded from the basic and diluted net loss per share calculation until the Company’s repurchase right lapses.
Recently Adopted Accounting Standards and Recently Issued Accounting Pronouncements Not Yet Adopted	Recently Adopted Accounting Standards On January 1, 2021, the Company adopted ASC 842 using the modified retrospective transition method and elected the practical expedients to not reassess whether any expired or existing contracts are or contain leases, carry forward its historical lease classification and not reassess initial direct costs for existing leases. The Company elected to not separate non-lease components from the associated lease components and to not recognize ROU assets and lease liabilities for leases with a term of twelve months or less. Upon adoption of ASC 842, the Company recorded an operating right-of-use asset of $4.6 million, operating lease liabilities of $9.1 million and derecognized deferred rent and other lease liabilities of $4.5 million. Results for the nine months ended September 30, 2021 are presented under ASC 842. Prior period amounts before January 1, 2021 have not been adjusted and continue to be reported in accordance with the Company’s historical accounting under previous lease guidance, ASC 840: Leases (Topic 840) Recently Issued Accounting Pronouncements Not Yet Adopted In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments which replaces the existing incurred loss impairment model with an expected credit loss model In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes In August 2020, the FASB issued ASU No. 2020-06, Debt— Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40) (“ASU 2020-06”), which is intended to simplify the accounting for convertible debt instruments and convertible preferred stock. This standard removes the existing guidance in ASC 470-20 that requires companies to account for cash conversion features and beneficial conversion features in equity, separately from the host convertible debt or preferred stock. As an emerging growth company, ASU 2020-06 is effective for the Company beginning January 1, 2024. The Company currently does not expect the adoption of this standard to have a material impact on its financial statements.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2021
Fair Value Disclosures [Abstract]
Summary of Fair Value of Financial Assets Measured at Fair Value on Recurring Basis	The following tables summarize the Company’s financial assets measured at fair value on a recurring basis by level within the fair value hierarchy: September 30, 2021 Valuation Hierarchy Amortized Cost Unrealized Gain Unrealized Loss Fair Value (In thousands) Assets: Cash equivalents: Money market funds Level 1 $ 68,815 $ — $ — $ 68,815 Commercial paper Level 2 44,246 — — 44,246 Government agencies bonds Level 2 3,015 — — 3,015 Marketable securities: U.S. treasuries Level 1 40,677 — (9 ) 40,668 Commercial paper Level 2 109,095 3 (12 ) 109,086 Corporate bonds Level 2 9,036 — (4 ) 9,032 Government agencies bonds Level 2 4,603 — (1 ) 4,602 Total financial assets $ 279,487 $ 3 $ (26 ) $ 279,464 December 31, 2020 Valuation Hierarchy Amortized Cost Unrealized Gain Unrealized Loss Fair Value (In thousands) Assets: Cash equivalents: Money market funds Level 1 $ 127,535 $ — $ — $ 127,535 Total financial assets $ 127,535 $ — $ — $ 127,535
Summary of Significant Unobservable Assumptions used to Convertible Preferred Stock Tranche Liability	The following table summarizes the significant unobservable assumptions used to value the convertible preferred stock tranche liability as of the settlement date of August 24, 2020: August 24, 2020 Term to valuation date (in years) 0.00 Discount rate 5.0%
Summary of Changes in Estimated Fair Value Liabilities Measures at Fair Value on a Recurring Basis	The following table summarizes the changes in the estimated fair value of the Company’s convertible preferred stock tranche liability measured on a recurring basis using significant Level 3 inputs: Nine Months Ended September 30, 2020 (In thousands) Beginning balance $ 786 Change in fair value upon remeasurement (75 ) Settlement of convertible preferred stock tranche liability on second and third closings of the Series B convertible preferred stock (711 ) Ending balance $ —

Balance Sheet Components (Table

Balance Sheet Components (Tables)	9 Months Ended
	Sep. 30, 2021
Balance Sheet Related Disclosures [Abstract]
Summary of Property and Equipment, Net	Property and equipment, net consists of the following: September 30, 2021 December 31, 2020 (In thousands) Construction in progress $ 21,895 $ 7,678 Laboratory equipment 9,806 8,182 Leasehold improvements 7,242 7,237 Furniture and fixtures 534 534 Computer equipment and software 272 257 Total property and equipment $ 39,749 $ 23,888 Less: accumulated depreciation and amortization (8,858 ) (6,703 ) Total property and equipment, net $ 30,891 $ 17,185
Summary of Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities consist of the following: September 30, 2021 December 31, 2020 (In thousands) Accrued compensation and related expenses $ 2,663 $ 2,090 Accrued research and development expenses 1,043 391 Accrued property and equipment 972 231 Other current liabilities 514 121 Accrued professional services 415 328 Total accrued expenses and other current liabilities $ 5,607 $ 3,161

Commitment and Contingencies (T

Commitment and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2021
Commitments And Contingencies Disclosure [Abstract]
Summary of Undiscounted Future Minimum Lease Payments Due Under Non-cancelable Operating Lease	As of September 30, 2021, the undiscounted future minimum lease payments due under the Company’s non-cancelable operating leases are as follows: Amount (In thousands) 2021 (remaining 3 months) $ 902 2022 3,678 2023 3,792 2024 3,910 2025 2,445 Thereafter 8,291 Total undiscounted future minimum lease payments $ 23,018 Present value adjustment for minimum lease commitments (6,515 ) Tenant improvement receivable (282 ) Total operating lease liabilities $ 16,221
Summary of Undiscounted Future Minimum Lease Payments Due Under Non-cancelable Operating Lease	As of December 31, 2020, undiscounted future minimum lease payments due under the Company’s non-cancelable operating lease are as follows: Amount (In thousands) 2021 $ 3,752 2022 2,206 2023 2,283 2024 2,363 2025 999 Total future minimum lease payments $ 11,603

Convertible Preferred Stock (Ta

Convertible Preferred Stock (Tables)	9 Months Ended
	Sep. 30, 2021
Temporary Equity Disclosure [Abstract]
Schedule of Convertible Preferred Stock	Prior to the Company’s IPO, convertible preferred stock as of December 31, 2020 consists of the following: December 31, 2020 Shares Authorized Shares Issued and Outstanding Net Carrying Value Liquidation Preference (In thousands, except share data) Convertible Preferred Stock Series A 8,316,666 8,316,662 $ 43,393 $ 49,900 Series B 9,259,254 9,259,245 91,644 92,000 Series C 8,526,381 6,917,621 85,717 86,000 Total 26,102,301 24,493,528 $ 220,754 $ 227,900

Common Stock (Tables)

Common Stock (Tables)	9 Months Ended
	Sep. 30, 2021
Equity [Abstract]
Schedule of Common Stock Reserved for Issuance	Total shares of common stock reserved for issuance, on an as-if converted basis, is as follows: September 30, 2021 December 31, 2020 Conversion of outstanding shares of convertible preferred stock — 24,493,528 Stock options issued and outstanding 2,530,121 1,160,808 Stock options available for future grant 3,847,160 412,170 Total 6,377,281 26,066,506

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Stock Option Activity	The following table summarizes stock option activity: Number of Options Outstanding Weighted- Average Exercise Price Per Share Weighted- Average Remaining Contractual Life Aggregate Intrinsic Value (Years) (In thousands) Outstanding as of December 31, 2020 1,160,808 $ 1.74 8.40 $ 6,060 Options granted 1,595,128 9.36 Options exercised (184,777 ) 1.85 Options cancelled (41,038 ) 3.51 Outstanding as of September 30, 2021 2,530,121 $ 6.50 8.87 $ 35,805 Exercisable as of September 30, 2021 590,000 $ 2.18 7.71 $ 10,898
Summary of Stock-based Compensation	The following table summarizes stock-based compensation recognized in the Company’s condensed statements of operations and comprehensive loss: Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 (In thousands) Research and development $ 326 $ 97 $ 654 $ 273 General and administrative 642 101 1,248 264 Total stock-based compensation $ 968 $ 198 $ 1,902 $ 537
Summary of Fair Value of Stock Option Awards	The fair value of the Company’s stock option awards is estimated on the date of grant using the Black-Scholes option pricing model using the following assumptions: Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Expected term (in years) 6.0 - 6.1 6.0 5.0 - 6.1 6.0 - 6.1 Expected volatility 95% - 96% 183% 95% - 103% 178% - 183% Risk-free interest rate 0.9% - 1.2% 0.4% 0.6% - 1.2% 0.4% - 1.5% Expected dividend yield — % — % — % — %
Summary of Restricted Stock Activity	A summary of restricted stock activity is as follows: Number of Shares Weighted Average Fair Value at Date of Grant per Share Unvested as of December 31, 2020 138,127 $ 0.90 Granted 19,852 $ 1.93 Vested (100,105 ) $ 0.56 Repurchased (16,959 ) $ 2.27 Unvested as of September 30, 2021 40,915 $ 1.67

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	9 Months Ended
	Sep. 30, 2021
Earnings Per Share [Abstract]
Schedule of Antidilutive Securities Excluded from Computation of Diluted Net Loss Per Share	The following potentially dilutive securities were not included in the calculation of diluted net loss per share as of the periods presented because the effect would have been anti-dilutive: September 30, 2021 2020 Convertible preferred stock — 17,575,907 Outstanding stock options 2,530,121 1,099,224 Restricted stock subject to future vesting 40,915 179,062 Total 2,571,036 18,854,193

Organization and Description _2

Organization and Description of the Business - Additional Information (Details) $ / shares in Units, $ in Thousands	Aug. 03, 2021USD ($)$ / sharesshares	Jul. 23, 2021	Sep. 30, 2021USD ($)shares	Jun. 30, 2021USD ($)	Mar. 31, 2021USD ($)	Sep. 30, 2020USD ($)	Jun. 30, 2020USD ($)	Mar. 31, 2020USD ($)	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Dec. 31, 2020USD ($)
Organization And Description Of Business [Line Items]
Reverse stock split description		1-for-6
Reverse stock split		0.1667
Net proceeds of after deducting underwriting discounts and commissions									$ 188,605
Accumulated deficit			$ (129,382)						(129,382)		$ (82,812)
Net loss			(18,262)	$ (15,210)	$ (13,098)	$ (10,295)	$ (8,731)	$ (9,051)	(46,570)	$ (28,077)
Cash, cash equivalents and investments in marketable securities			$ 280,500						$ 280,500
Common Stock
Organization And Description Of Business [Line Items]
Issuance of common stock | shares			13,800,000
Net proceeds of after deducting underwriting discounts and commissions	$ 188,500
Conversion of outstanding shares of convertible preferred stock | shares	26,102,278
Common Stock | Initial Public Offering
Organization And Description Of Business [Line Items]
Issuance of common stock | shares	13,800,000
Share price | $ / shares	$ 15
Underwriting discounts and commissions	$ 14,500
Other offering expenses	$ 4,000
Common Stock | Overallotment Option
Organization And Description Of Business [Line Items]
Issuance of common stock | shares	1,800,000

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Jan. 01, 2021
Significant Accounting Policies [Line Items]
Operating lease right-of-use assets	$ 12,006
Operating lease liabilities	$ 16,221
ASC 842
Significant Accounting Policies [Line Items]
Operating lease right-of-use assets		$ 4,600
Operating lease liabilities		9,100
Derecognized deferred rent and other lease liabilities		$ 4,500
Accounting standards update, adopted [true false]	true
Accounting standards update, adoption date	Jan. 1, 2021

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Fair Value of Financial Assets Measured at Fair Value on Recurring Basis (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	$ 279,487	$ 127,535
Unrealized Gain	3
Unrealized Loss	(26)
Fair Value	279,464	127,535
Money Market Funds | Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	68,815	127,535
Fair Value	68,815	$ 127,535
Commercial Paper | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	44,246
Fair Value	44,246
Government Agencies Bonds | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	3,015
Fair Value	3,015
U.S. Treasuries | Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	40,677
Unrealized Loss	(9)
Fair Value	40,668
Commercial Paper | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	109,095
Unrealized Gain	3
Unrealized Loss	(12)
Fair Value	109,086
Corporate Bonds | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	9,036
Unrealized Loss	(4)
Fair Value	9,032
Government Agencies Bonds | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	4,603
Unrealized Loss	(1)
Fair Value	$ 4,602

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details) - USD ($)	9 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Impairment charges on marketable securities related to other-than-temporary	$ 0
Convertible preferred stock tranche liability	$ 0	$ 0
Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale marketable securities contractual maturities term	1 year

Fair Value Measurements - Sum_2

Fair Value Measurements - Summary of Significant Unobservable Assumptions used to Convertible Preferred Stock Tranche Liability (Details) - Convertible Preferred Stock Tranche Liability	Aug. 24, 2020
Term to Valuation Date
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Term to valuation date (in years)	0 years
Discount rate
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Measurement input	5

Fair Value Measurements - Sum_3

Fair Value Measurements - Summary of Changes in Estimated Fair Value Liabilities Measures at Fair Value on a Recurring Basis (Details) - Level 3 - Convertible Preferred Stock Tranche Liability $ in Thousands	9 Months Ended
	Sep. 30, 2020USD ($)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Beginning balance	$ 786
Change in fair value upon remeasurement	(75)
Settlement of convertible preferred stock tranche liability on second and third closings of the Series B convertible preferred stock	$ (711)

Balance Sheet Components - Summ

Balance Sheet Components - Summary of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Property Plant And Equipment [Line Items]
Total property and equipment	$ 39,749	$ 23,888
Less: accumulated depreciation and amortization	(8,858)	(6,703)
Total property and equipment, net	30,891	17,185
Construction in Progress
Property Plant And Equipment [Line Items]
Total property and equipment	21,895	7,678
Laboratory Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	9,806	8,182
Leasehold Improvements
Property Plant And Equipment [Line Items]
Total property and equipment	7,242	7,237
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Total property and equipment	534	534
Computer Equipment and Software
Property Plant And Equipment [Line Items]
Total property and equipment	$ 272	$ 257

Balance Sheet Components - Addi

Balance Sheet Components - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Balance Sheet Related Disclosures [Abstract]
Depreciation and amortization expense	$ 0.7	$ 0.6	$ 2.2	$ 1.8

Balance Sheet Components - Su_2

Balance Sheet Components - Summary of Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Balance Sheet Related Disclosures [Abstract]
Accrued compensation and related expenses	$ 2,663	$ 2,090
Accrued research and development expenses	1,043	391
Accrued property and equipment	972	231
Other current liabilities	514	121
Accrued professional services	415	328
Total accrued expenses and other current liabilities	$ 5,607	$ 3,161

License Agreements (Details)

License Agreements (Details)	1 Months Ended		3 Months Ended		9 Months Ended
	Jan. 31, 2020USD ($)	Oct. 31, 2016USD ($)Option	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development expense related to upfront license fee payable			$ 12,944,000	$ 8,480,000	$ 33,440,000	$ 22,735,000
University of Texas Southwestern License Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone and royalty payments recognized					0
Non-refundable upfront license fee	$ 100,000
Research and development expense related to upfront license fee payable						$ 100,000
University of Texas Southwestern License Agreement | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments contingent upon achieving specific development and commercialization milestone events	$ 14,800,000
Gladstone | Gladstone License Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone and royalty payments recognized					$ 0
Number of additional option to extend milestone payment | Option		4
Milestone obligation additional extended payment terms		1 year
Gladstone | Gladstone License Agreement | Minimum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Annual license maintenance fees		$ 25,000
Milestone obligation amount		50,000
Gladstone | Gladstone License Agreement | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Annual license maintenance fees		100,000
Milestone payments for royalty-bearing products contingent upon achieving specific clinical and commercialization milestone events		4,100,000
Milestone obligation amount		$ 100,000

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) $ in Millions	1 Months Ended			3 Months Ended		9 Months Ended
	Feb. 28, 2021USD ($)RenewalOption	Dec. 31, 2020	Dec. 31, 2016USD ($)RenewalOption	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)
Commitments And Contingencies [Line Items]
Rent expense				$ 1.6	$ 0.6	$ 4.2	$ 1.9
Short-term lease				0.6		1.8
Variable lease payments				$ 0.4		$ 1.2
Sublease agreements expiration date							Dec. 31, 2020
Other Income (Expense), Net
Commitments And Contingencies [Line Items]
Sublease Income							$ 0.2
ASC 842
Commitments And Contingencies [Line Items]
Remaining weighted-average lease term				6 years 9 months 18 days		6 years 9 months 18 days
Weighted-average incremental borrowing rate used to determine operating lease liability				9.50%		9.50%
Office and Laboratory Space | South San Francisco, California
Commitments And Contingencies [Line Items]
Lease expiration month and year			2025-05
Lease renewal term			5 years
Number of lease renewal term | RenewalOption			2
Tenant improvement allowance			$ 5.8
Additional Office and Laboratory Space | South San Francisco, California
Commitments And Contingencies [Line Items]
Lease Expiration Date		Nov. 30, 2021
Manufacturing and Office Space | Union City, California
Commitments And Contingencies [Line Items]
Lease renewal term	5 years
Number of lease renewal term | RenewalOption	1
Lease commenced month and year	2021-05
Term of lease	10 years
Manufacturing and Office Space | Union City, California | Other Noncurrent Assets
Commitments And Contingencies [Line Items]
Security deposit	$ 3.3

Commitments and Contingencies_2

Commitments and Contingencies - Summary of Undiscounted Future Minimum Lease Payments Due Under Non-cancelable Operating Lease (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Commitments And Contingencies Disclosure [Abstract]
2021 (remaining 3 months)	$ 902
2022	3,678
2023	3,792
2024	3,910
2025	2,445
Thereafter	8,291
Total undiscounted future minimum lease payments	23,018
Present value adjustment for minimum lease commitments	(6,515)
Tenant improvement receivable	(282)
Operating lease liabilities	$ 16,221
2021		$ 3,752
2022		2,206
2023		2,283
2024		2,363
2025		999
Total future minimum lease payments		$ 11,603

Convertible Preferred Stock - A

Convertible Preferred Stock - Additional Information (Details)	Aug. 03, 2021shares	Jan. 31, 2021USD ($)$ / sharesshares	Dec. 31, 2020USD ($)Closing$ / sharesshares	Aug. 31, 2020USD ($)$ / sharesshares	Mar. 31, 2020USD ($)$ / sharesshares	Aug. 31, 2019USD ($)$ / sharesshares	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)
Temporary Equity [Line Items]
Convertible preferred stock, shares authorized			26,102,301
Convertible preferred stock shares issued			24,493,528
Series B Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible preferred stock, shares authorized			9,259,254
Convertible preferred stock purchase price per share | $ / shares				$ 9.936	$ 9.936
Convertible preferred stock shares issued			9,259,245	3,086,415	3,086,415
Proceeds from issuance of convertible preferred stock, net of issuance costs | $				$ 30,700,000	$ 30,700,000	$ 30,700,000		$ 61,328,000
Reclassification of balance liability to convertible preferred stock | $				$ 700,000	$ 27,000
Series C Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible preferred stock, shares authorized			8,526,381
Convertible preferred stock purchase price per share | $ / shares		$ 12.432
Convertible preferred stock shares issued		1,608,750	6,917,621
Proceeds from issuance of convertible preferred stock, net of issuance costs | $		$ 20,000,000					$ 19,981,000
Series B Preferred Stock Purchase Agreement | Series B Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible preferred stock, shares authorized						9,259,254
Convertible preferred stock purchase price per share | $ / shares						$ 9.936
Convertible preferred stock shares issued						3,086,415
Fair value of convertible preferred stock tranche liability | $							$ 800,000
Series C Preferred Stock Purchase Agreement | Series C Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible preferred stock, shares authorized			8,526,381
Convertible preferred stock purchase price per share | $ / shares			$ 12.432
Convertible preferred stock shares issued			6,917,621
Proceeds from issuance of convertible preferred stock, net of issuance costs | $			$ 86,000,000
Number of closings | Closing			2
Common Stock
Temporary Equity [Line Items]
Conversion of outstanding shares of convertible preferred stock	26,102,278

Convertible Preferred Stock - S

Convertible Preferred Stock - Schedule of Convertible Preferred Stock (Details) - USD ($) $ in Thousands	Jan. 31, 2021	Dec. 31, 2020	Aug. 31, 2020	Mar. 31, 2020
Temporary Equity [Line Items]
Shares Authorized		26,102,301
Shares Issued		24,493,528
Shares Outstanding		24,493,528
Net Carrying Value		$ 220,754
Liquidation Preference		$ 227,900
Series A Convertible Preferred Stock
Temporary Equity [Line Items]
Shares Authorized		8,316,666
Shares Issued		8,316,662
Shares Outstanding		8,316,662
Net Carrying Value		$ 43,393
Liquidation Preference		$ 49,900
Series B Convertible Preferred Stock
Temporary Equity [Line Items]
Shares Authorized		9,259,254
Shares Issued		9,259,245	3,086,415	3,086,415
Shares Outstanding		9,259,245
Net Carrying Value		$ 91,644
Liquidation Preference		$ 92,000
Series C Convertible Preferred Stock
Temporary Equity [Line Items]
Shares Authorized		8,526,381
Shares Issued	1,608,750	6,917,621
Shares Outstanding		6,917,621
Net Carrying Value		$ 85,717
Liquidation Preference		$ 86,000

Common Stock - Additional Infor

Common Stock - Additional Information (Details) - shares	9 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Class Of Stock [Line Items]
Common stock voting rights	The holders of common stock are entitled to one vote per share on all matters to be voted on by the stockholders of the Company and are entitled to dividends, if and when declared by the board of directors, subject to the prior rights of the preferred stockholders.
Early Exercised Stock Options and Restricted Stock That are Unvested and Subject to Repurchase
Class Of Stock [Line Items]
Common stock outstanding	40,915	138,127

Common Stock - Schedule of Comm

Common Stock - Schedule of Common Stock Reserved for Issuance (Details) - shares	Sep. 30, 2021	Dec. 31, 2020
Class Of Stock [Line Items]
Common stock reserved for issuance	6,377,281	26,066,506
Stock Options Issued and Outstanding
Class Of Stock [Line Items]
Common stock reserved for issuance	2,530,121	1,160,808
Stock Options Available for Future Grant
Class Of Stock [Line Items]
Common stock reserved for issuance	3,847,160	412,170
Conversion of Outstanding Shares of Convertible Preferred Stock
Class Of Stock [Line Items]
Common stock reserved for issuance		24,493,528

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) - USD ($)	1 Months Ended	3 Months Ended		9 Months Ended
	Jul. 31, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for issuance		6,377,281		6,377,281		26,066,506
Stock-based compensation		$ 968,000	$ 198,000	$ 1,902,000	$ 537,000
Unrecognized stock-based compensation		14,300,000		$ 14,300,000
Weighted-average period				3 years 6 months
Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Repurchase unvested shares after unemployment, terminated				90 days
Principal and accrued interest amount				$ 12,000
2021 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for issuance	800,000
Participants to purchase common stock through payroll deduction maximum percentage of eligible compensation	15.00%
Number of shares of common stock that may be issued in accordance with the plan	800,000
Percentage of shares of common stock outstanding on last day of immediately preceding year	1.00%
Stock-based compensation		$ 0		$ 0
2021 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock shares available for issuance period	10 years
Number of shares of common stock that may be issued in accordance with the plan	4,000,000
Percentage of shares of common stock outstanding on last day of immediately preceding year	4.00%
Shares reserved and available for grant		3,847,160		3,847,160

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock Option Activity (Details) - 2021 Equity Incentive Plan $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021USD ($)$ / sharesshares	Dec. 31, 2020USD ($)$ / sharesshares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Options Outstanding, Outstanding Beginning Balance | shares	1,160,808
Number of Options Outstanding, Options granted | shares	1,595,128
Number of Options Outstanding, Options exercised | shares	(184,777)
Number of Options Outstanding, Options cancelled | shares	(41,038)
Number of Options Outstanding, Outstanding Ending Balance | shares	2,530,121	1,160,808
Number of Options Outstanding, Exercisable as of June 30, 2021 | shares	590,000
Weighted-Average Exercise Price Per Share, Outstanding Beginning Balance | $ / shares	$ 1.74
Weighted-Average Exercise Price Per Share, Options granted | $ / shares	9.36
Weighted-Average Exercise Price Per Share, Options exercised | $ / shares	1.85
Weighted-Average Exercise Price Per Share, Options cancelled | $ / shares	3.51
Weighted-Average Exercise Price Per Share, Outstanding Ending Balance | $ / shares	6.50	$ 1.74
Weighted-Average Exercise Price Per Share, Exercisable as of June 30, 2021 | $ / shares	$ 2.18
Weighted-Average Remaining Contractual Life, Outstanding	8 years 10 months 13 days	8 years 4 months 24 days
Weighted-Average Remaining Contractual Life, Exercisable as of June 30, 2021	7 years 8 months 15 days
Aggregate Intrinsic Value, Outstanding | $	$ 35,805	$ 6,060
Aggregate Intrinsic Value, Exercisable as of June 30, 2021 | $	$ 10,898

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of Stock-based Compensation (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation	$ 968	$ 198	$ 1,902	$ 537
Research and Development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation	326	97	654	273
General and Administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation	$ 642	$ 101	$ 1,248	$ 264

Stock-Based Compensation - Su_3

Stock-Based Compensation - Summary of Fair Value of Stock Option Awards (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)		6 years
Expected volatility		183.00%
Expected volatility, minimum	95.00%		95.00%	178.00%
Expected volatility, maximum	96.00%		103.00%	183.00%
Risk-free interest rate		0.40%
Risk-free interest rate, minimum	0.90%		0.60%	0.40%
Risk free interest rate, maximum	1.20%		1.20%	1.50%
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	6 years		5 years	6 years
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	6 years 1 month 6 days		6 years 1 month 6 days	6 years 1 month 6 days

Stock-Based Compensation - Su_4

Stock-Based Compensation - Summary of Restricted Stock Activity (Details) - Restricted Stock	9 Months Ended
	Sep. 30, 2021$ / sharesshares
Number of Shares
Unvested as of December 31, 2020 | shares	138,127
Granted | shares	19,852
Vested | shares	(100,105)
Repurchased | shares	(16,959)
Unvested as of September 30, 2021 | shares	40,915
Weighted Average Fair Value at Date of Grant per Share
Unvested as of December 31, 2020 | $ / shares	$ 0.90
Granted | $ / shares	1.93
Vested | $ / shares	0.56
Repurchased | $ / shares	2.27
Unvested as of September 30, 2021 | $ / shares	$ 1.67

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Tax Disclosure [Abstract]
Income tax expense	$ 0	$ 0	$ 0	$ 0

Net Loss Per Share - Schedule o

Net Loss Per Share - Schedule of Antidilutive Securities Excluded from Computation of Diluted Net Loss Per Share (Details) - shares	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities were not included in the calculation of diluted net loss per share	2,571,036	18,854,193
Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities were not included in the calculation of diluted net loss per share		17,575,907
Outstanding Stock Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities were not included in the calculation of diluted net loss per share	2,530,121	1,099,224
Restricted Stock Subject to Future Vesting
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities were not included in the calculation of diluted net loss per share	40,915	179,062