Annexon (ANNX) 10-Q 3 Nov 22 2022 Q3 Quarterly report Financial data

Cover Page

Cover Page - shares	9 Months Ended
	Sep. 30, 2022	Oct. 28, 2022
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Amendment Flag	false
Document Period End Date	Sep. 30, 2022
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q3
Trading Symbol	ANNX
Entity Registrant Name	ANNEXON, INC.
Entity Central Index Key	0001528115
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Title of 12(b) Security	Common Stock, par value $0.001 per share
Security Exchange Name	NASDAQ
Entity File Number	001-39402
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	27-5414423
Entity Address, Address Line One	1400 Sierra Point Parkway
Entity Address, Address Line Two	Bldg C
Entity Address, Address Line Three	Suite 200
Entity Address, City or Town	Brisbane
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94005
City Area Code	650
Local Phone Number	822-5500
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Common Stock [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		47,630,393
Prefunded Warrant [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		24,696,206

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 210,658	$ 74,843
Short-term investments	58,861	167,872
Prepaid expenses and other current assets	5,258	4,978
Total current assets	274,777	247,693
Restricted cash	1,032	1,166
Property and equipment, net	17,093	17,848
Operating lease right-of-use assets	19,616	20,333
Other non-current assets	204
Total assets	312,722	287,040
Current liabilities:
Accounts payable	6,921	11,153
Accrued liabilities	11,323	9,250
Operating lease liabilities, current	1,806	1,202
Other current liabilities	170	139
Total current liabilities	20,220	21,744
Operating lease liabilities, non-current	31,900	33,387
Total liabilities	52,120	55,131
Commitments and contingencies (Note 5)
Stockholders’ equity:
Common stock	48	39
Additional paid-in capital	664,839	528,365
Accumulated other comprehensive loss	(406)	(180)
Accumulated deficit	(403,879)	(296,315)
Total stockholders’ equity	260,602	231,909
Total liabilities and stockholders’ equity	$ 312,722	$ 287,040

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Operating expenses:
Research and development	$ 27,862	$ 27,581	$ 83,966	$ 72,849
General and administrative	8,207	8,099	24,938	20,406
Total operating expenses	36,069	35,680	108,904	93,255
Loss from operations	(36,069)	(35,680)	(108,904)	(93,255)
Interest and other income, net	1,015	82	1,340	303
Net loss	(35,054)	(35,598)	(107,564)	(92,952)
Net loss attributable to common stockholders	$ (35,054)	$ (35,598)	$ (107,564)	$ (92,952)
Net loss per share attributable to common stockholders, basic	$ (0.51)	$ (0.93)	$ (2.21)	$ (2.43)
Net loss per share attributable to common stockholders, diluted	$ (0.51)	$ (0.93)	$ (2.21)	$ (2.43)
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic	68,652,859	38,341,110	48,710,433	38,261,359
Weighted-average shares used in computing net loss per share attributable to common stockholders, diluted	68,652,859	38,341,110	48,710,433	38,261,359

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Statement of Comprehensive Income [Abstract]
Net loss	$ (35,054)	$ (35,598)	$ (107,564)	$ (92,952)
Other comprehensive gain (loss):
Foreign currency translation adjustment	(4)	(3)	(7)	(5)
Unrealized gain (loss) on available-for-sale securities	37	(7)	(219)	7
Comprehensive loss	$ (35,021)	$ (35,608)	$ (107,790)	$ (92,950)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Accumulated Deficit [Member]
Beginning Balance, Values at Dec. 31, 2020	$ 344,278	$ 38	$ 510,309	$ (77)	$ (165,992)
Beginning Balance, Shares at Dec. 31, 2020		38,157,618
Stock-based compensation	2,962		2,962
Stock option exercises	268		268
Stock option exercises, Shares		74,930
Foreign currency translation adjustment	(1)			(1)
Unrealized gain (loss) on available-for-sale securities	(25)			(25)
Net loss	(26,060)				(26,060)
Ending Balance, Values at Mar. 31, 2021	321,422	$ 38	513,539	(103)	(192,052)
Ending Balance, Shares at Mar. 31, 2021		38,232,548
Beginning Balance, Values at Dec. 31, 2020	344,278	$ 38	510,309	(77)	(165,992)
Beginning Balance, Shares at Dec. 31, 2020		38,157,618
Foreign currency translation adjustment	(5)
Unrealized gain (loss) on available-for-sale securities	7
Net loss	(92,952)
Ending Balance, Values at Sep. 30, 2021	264,477	$ 38	523,458	(75)	(258,944)
Ending Balance, Shares at Sep. 30, 2021		38,370,098
Beginning Balance, Values at Mar. 31, 2021	321,422	$ 38	513,539	(103)	(192,052)
Beginning Balance, Shares at Mar. 31, 2021		38,232,548
Stock-based compensation	4,517		4,517
Stock option exercises	534		534
Stock option exercises, Shares		82,805
Issuance of common stock per Employee Stock Purchase Plan	118		118
Issuance of common stock per Employee Stock Purchase Plan, Shares		6,759
Foreign currency translation adjustment	(1)			(1)
Unrealized gain (loss) on available-for-sale securities	39			39
Net loss	(31,294)				(31,294)
Ending Balance, Values at Jun. 30, 2021	295,335	$ 38	518,708	(65)	(223,346)
Ending Balance, Shares at Jun. 30, 2021		38,322,112
Stock-based compensation	4,428		4,428
Stock option exercises	322		322
Stock option exercises, Shares		47,986
Foreign currency translation adjustment	(3)			(3)
Unrealized gain (loss) on available-for-sale securities	(7)			(7)
Net loss	(35,598)				(35,598)
Ending Balance, Values at Sep. 30, 2021	264,477	$ 38	523,458	(75)	(258,944)
Ending Balance, Shares at Sep. 30, 2021		38,370,098
Beginning Balance, Values at Dec. 31, 2021	231,909	$ 39	528,365	(180)	(296,315)
Beginning Balance, Shares at Dec. 31, 2021		38,560,854
Stock-based compensation	4,252		4,252
Stock option exercises	19		19
Stock option exercises, Shares		2,711
Foreign currency translation adjustment	3			3
Unrealized gain (loss) on available-for-sale securities	(196)			(196)
Net loss	(35,373)				(35,373)
Ending Balance, Values at Mar. 31, 2022	200,614	$ 39	532,636	(373)	(331,688)
Ending Balance, Shares at Mar. 31, 2022		38,563,565
Beginning Balance, Values at Dec. 31, 2021	$ 231,909	$ 39	528,365	(180)	(296,315)
Beginning Balance, Shares at Dec. 31, 2021		38,560,854
Stock option exercises, Shares	11,474
Foreign currency translation adjustment	$ (7)
Unrealized gain (loss) on available-for-sale securities	(219)
Net loss	(107,564)
Ending Balance, Values at Sep. 30, 2022	260,602	$ 48	664,839	(406)	(403,879)
Ending Balance, Shares at Sep. 30, 2022		47,626,503
Beginning Balance, Values at Mar. 31, 2022	200,614	$ 39	532,636	(373)	(331,688)
Beginning Balance, Shares at Mar. 31, 2022		38,563,565
Stock-based compensation	4,520		4,520
Issuance of common stock per Employee Stock Purchase Plan	113		113
Issuance of common stock per Employee Stock Purchase Plan, Shares		40,341
Foreign currency translation adjustment	(6)			(6)
Unrealized gain (loss) on available-for-sale securities	(60)			(60)
Net loss	(37,137)				(37,137)
Ending Balance, Values at Jun. 30, 2022	168,044	$ 39	537,269	(439)	(368,825)
Ending Balance, Shares at Jun. 30, 2022		38,603,906
Stock-based compensation	4,911		4,911
Stock option exercises	45		45
Stock option exercises, Shares		8,763
Issuance of common stock, pre-funded warrants and common warrants, net of issuance costs of issuance costs, Shares		9,013,834
Issuance of common stock, pre-funded warrants and common warrants, net of issuance costs of issuance costs	122,623	$ 9	122,614
Foreign currency translation adjustment	(4)			(4)
Unrealized gain (loss) on available-for-sale securities	37			37
Net loss	(35,054)				(35,054)
Ending Balance, Values at Sep. 30, 2022	$ 260,602	$ 48	$ 664,839	$ (406)	$ (403,879)
Ending Balance, Shares at Sep. 30, 2022		47,626,503

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Stockholders' Equity (Parenthetical) $ in Thousands	3 Months Ended
	Sep. 30, 2022 USD ($)
Stock issuance cost for related party	$ 9,500

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Operating activities:
Net loss	$ (107,564)	$ (92,952)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,576	1,635
Accretion of discount on available-for-sale securities	490	934
Stock-based compensation	13,683	11,907
Reduction in the carrying amount of right-of-use assets	717	926
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(280)	(1,765)
Other non-current assets	(204)
Accounts payable	(777)	874
Accrued liabilities	4,041	181
Operating lease liabilities	(883)	471
Other current liabilities	31
Net cash used in operating activities	(89,170)	(77,789)
Investing activities:
Purchases of property and equipment	(6,244)	(799)
Purchases of available-for-sale securities	(46,364)	(191,122)
Proceeds from sale of available-for-sale securities		7,988
Proceeds from maturities of available-for-sale securities	154,666	62,000
Net cash provided by (used in) investing activities	102,058	(121,933)
Financing activities:
Proceeds from the exercise common stock options	64	1,124
Proceeds from employee stock plan purchases	113	118
Proceeds from the issuance of common stock, pre-funded warrants and common warrants	120,976
Proceeds from the issuance of common stock, pre-funded warrants and common warrants - related party	9,500
Payment of issuance costs related to the issuance of common stock, pre-funded warrants and common warrants	(7,853)
Deferred offering costs payment related to the 2021 ATM program		(395)
Net cash provided by financing activities	122,800	847
increase (decrease) in cash, cash equivalents and restricted cash	135,688	(198,875)
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(7)	(5)
Cash, cash equivalents and restricted cash
Beginning of period	76,009	268,565
End of period	211,690	69,685
Supplemental disclosure of cash flow information:
Cash paid for amounts included in the measurement of lease liability	3,028	996
Non-cash investing and financing activities:
Purchases of property and equipment included in accounts payable and accrued liabilities	$ 118	372
Deferred offering costs included in accrued liabilities		198
Right-of-use assets obtained in exchange for lease liability		21,084
Construction-in-progress obtained in exchange for tenant improvement allowance from lessors		$ 10,748

Organization

Organization	9 Months Ended
	Sep. 30, 2022
Accounting Policies [Abstract]
Organization	1. Organization Annexon, Inc., or the Company, is a clinical-stage biopharmaceutical company pioneering a new class of complement medicines for patients with classical complement-mediated autoimmune, neurodegenerative and ophthalmic disorders. The Company is located in Brisbane, California and was incorporated in Delaware in March 2011. The Company’s wholly-owned subsidiary, Annexon Biosciences Australia Pty Ltd, or the Subsidiary, is a proprietary limited company incorporated in 2016 and domiciled in Australia. The Subsidiary is also engaged in research and development activities in support of its parent company. Liquidity Since inception, the Company has been involved primarily in performing research and development activities, conducting clinical trials, hiring personnel, and raising capital to support and expand these activities. The Company has experienced losses and negative cash flows from operations since its inception and, as of September 30, 2022, had an accumulated deficit of $ 403.9 million and cash and cash equivalents and short-term investments of $ 269.5 million. The Company has historically funded its operations through the issuance of shares of its redeemable convertible preferred stock and common stock. On July 11, 2022, the Company closed a private placement of shares of common stock, pre-funded warrants and common warrants, or Private Placement, which resulted in net proceeds of approximately $ 122.6 million, after deducting placement agent fees and other expenses. Based on projected activities, management projects that cash on hand is sufficient to support operations for at least the next 12 months following issuance of these condensed consolidated financial statements. Management expects to continue to incur losses and negative cash flows from operations for at least the next several years.

Basis of Presentation and Signi

Basis of Presentation and Significant Accounting Policies	9 Months Ended
	Sep. 30, 2022
Accounting Policies [Abstract]
Basis of Presentation and Significant Accounting Policies	2. Basis of Presentation and Significant Accounting Policies Basis of Presentation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States, or GAAP, and applicable rules and regulations of the SEC regarding interim financial reporting. The condensed consolidated balance sheet as of September 30, 2022, the condensed consolidated statements of operations, comprehensive loss, stockholders’ equity for the three and nine months ended September 30, 2022 and 2021 and the condensed consolidated statements of cash flows for the nine months ended September 30, 2022 and 2021 are unaudited. These unaudited condensed consolidated financial statements have been prepared on the same basis as the annual consolidated financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary to present fairly the Company’s consolidated financial position, results of operations and cash flows for the interim period presented. The financial data and the other financial information contained in these notes to the condensed consolidated financial statements related to the three and nine month periods are also unaudited. The results of operations for the three and nine months ended September 30, 2022 are not necessarily indicative of the results to be expected for the year ending December 31, 2022 or for any other future annual or interim period. The condensed consolidated balance sheet as of December 31, 2021 included herein was derived from the audited financial statements as of that date. These unaudited condensed consolidated financial statements should be read in conjunction with the Company's audited consolidated financial statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2021, filed with the SEC on March 1, 2022. Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported expenses during the reporting period. On an ongoing basis, management evaluates its estimates, including but not limited to fair value of investments, useful lives for property and equipment, incremental borrowing rate used in lease accounting, stock options, income taxes and certain accruals. The Company evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors and adjusts those estimates and assumptions when facts and circumstances dictate. Actual results could differ from those estimates. Principles of Consolidation The condensed consolidated financial statements include the operations of Annexon, Inc. and its wholly-owned subsidiary and include the results of operations and cash flows of these entities. All intercompany balances and transactions have been eliminated in consolidation. Cash, Cash Equivalents and Restricted Cash The Company considers all highly liquid instruments with an original maturity of three months or less at time of purchase to be cash equivalents. Cash equivalents, which includes amounts invested in money market funds, are stated at fair value. Restricted cash as of September 30, 2022 relates to the letters of credit established for the Company’s office leases. The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the condensed consolidated balance sheets that sum to the total of the same amounts shown in the condensed consolidated statements of cash flows: September 30, December 31, Cash $ 570 $ 734 Cash equivalents 210,088 74,109 Cash and cash equivalents 210,658 74,843 Restricted cash 1,032 1,166 Cash, cash equivalents and restricted cash $ 211,690 $ 76,009 Short-Term Investments Short-term investments 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. The Company determines the appropriate classification of its investments in debt securities at the time of purchase. Available-for-sale securities with original maturities beyond three months at the date of purchase are classified as current based on their availability for use in current operations. The Company evaluates, on a quarterly basis, its available-for-sale debt securities for potential impairment. For available-for-sale debt securities in an unrealized loss position, the Company assesses whether such declines are due to credit loss based on factors such as changes to the rating of the security by a ratings agency, market conditions and supportable forecasts of economic and market conditions, among others. If credit loss exists, the Company assesses whether it has plans to sell the security or it is more likely than not it will be required to sell any available-for-sale debt security before recovery of its amortized cost basis. If either condition is met, the security’s amortized cost basis is written down to fair value and is recognized through interest and other income (expense), net. If neither condition is met, declines as a result of credit losses, if any, are recognized as an allowance for credit loss, limited to the amount of unrealized loss, through interest and other income (expense), net. Any portion of the unrealized loss that is not a result of a credit loss, is recognized in other comprehensive income (loss). Realized gains and losses, if any, on available-for-sale debt securities are included in interest and other income (expense), net. The cost of investments sold is based on the specific-identification method. Interest on available-for-sale debt securities is included in interest and other income (expense), net. Warrants Warrants are accounted for as either derivative liabilities or as equity instruments depending on the specific terms of the agreement. The Company’s pre-funded and common warrants are equity-classified instruments that were recorded in additional paid-in capital at issuance and are not subject to remeasurement. The Company periodically evaluates changes in facts and circumstances that could impact the classification of warrants. Research and Development Expense Research and development expenses consist primarily of direct and indirect costs incurred for the development of the Company’s product candidates. Direct expenses include (i) preclinical and clinical outside service costs associated with discovery, preclinical and clinical testing of the Company’s product candidates; (ii) professional services agreements with third-party contract organizations, investigative clinical trial sites and consultants that conduct research and development activities on the Company’s behalf; (iii) contract manufacturing costs to produce clinical trial materials; and (iv) laboratory supplies and materials. Indirect expenses include (A) compensation and personnel-related expenses (including stock-based compensation); (B) allocated expenses for facilities and depreciation; and (C) other indirect costs. Research and development costs are expensed as incurred. Payments made to third parties are under agreements that are generally cancelable by the Company. Advance payments for research and development activities are deferred as prepaid expenses. The prepaid amounts are expensed as the related services are performed. The Company estimates preclinical studies and clinical trial expenses based on the services performed pursuant to contracts with research institutions and clinical research organizations that conduct and manage preclinical studies and clinical trials on the Company’s behalf. In accruing service fees, the Company estimates the period over which services will be performed and the level of effort to be expended in each period. These estimates are based on the Company’s communications with the third-party service providers and on information available at each balance sheet date. If the actual timing of the performance of services or the level of effort varies significantly from the estimate, the Company will adjust the accrual accordingly to reflect the best information available at the time of the financial statement issuance. The Company has not experienced any material differences between accrued costs and actual costs incurred since its inception. Stock-Based Compensation The Company accounts for stock-based compensation arrangements with employees, non-employee directors and consultants using a fair value method which requires the recognition of compensation expense for costs related to all stock-based payments, including stock options and restricted stock units, or RSUs. The fair value method requires the Company to estimate the fair value of stock options to employees and non-employee directors on the date of grant using the Black-Scholes option pricing model. The fair value of RSU awards is based on the fair value of the underlying common stock as of the grant date. The Company grants certain employees performance-based stock options. For awards that include performance conditions, no compensation cost is recognized until the performance goals are probable of being met, at which time the cumulative compensation expense from the service inception date would be recognized. Stock-based compensation costs are based on the fair value of the underlying option calculated using the Black-Scholes option pricing model and recognized as expense on a straight-line basis (for all but performance-based awards for which the accelerated method is used) over the requisite service period, which is the vesting period. Determining the appropriate fair value model and related assumptions requires judgment, including estimating the fair value of the underlying common stock, expected term, expected stock price volatility, risk-free interest rate and dividend yield. The Company accounts for forfeitures as they occur. Net Loss Per Share Attributable to Common Stockholders Basic net loss per share attributable to common stockholders is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of shares of common stock outstanding for the period, without consideration for potential dilutive shares of common stock. As the Company was in a loss position for all periods presented, basic net loss per share attributable to common stockholders is the same as diluted net loss per share attributable to common stockholders because the effects of potentially dilutive securities are antidilutive. Concentration of Credit Risk Financial instruments that potentially subject the Company to concentrations of credit risk consist primarily of cash and cash equivalents and short-term investments. The Company’s cash and cash equivalents and short-term investments are held by high credit quality financial institutions in the United States. At times, such deposits may be in excess of the Federal Depository Insurance Corporation insured limits. Management believes that the financial institutions are financially sound, and accordingly, minimal credit risk exists with respect to the financial institutions. Recently Adopted Accounting Pronouncements 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 No. 2020-06” ). ASU No. 2020-06 simplifies the accounting for convertible instruments. The guidance removes certain accounting models that separate the embedded conversion features from the host contract for convertible instruments. The Company adopted ASU 2020-06 effective as of January 1, 2022 . The adoption of ASU 2020-06 did not have an impac t on the Company’s condensed consolidated financial statements. Recently Issued Accounting Pronouncements The Company does not believe that any recently issued effective pronouncements, or pronouncements issued but not yet effective, if adopted, would have a material impact on its financial position or results of operations.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2022
Fair Value Disclosures [Abstract]
Fair Value Measurements	3. Fair Value Measurements The Company utilizes valuation techniques that maximize the use of observable inputs and minimize the use of unobservable inputs to the extent possible. The Company determines fair value based on assumptions that market participants would use in pricing an asset or liability in the principal or most advantageous market. When considering market participant assumptions in fair value measurements, the following fair value hierarchy distinguishes between observable and unobservable inputs, which are categorized in one of the following levels: • Level 1 Inputs: Unadjusted quoted prices in active markets for identical assets or liabilities accessible to the reporting entity at the measurement date. • Level 2 Inputs: Other than quoted prices included in Level 1 inputs that are observable for the asset or liability, either directly or indirectly, for substantially the full term of the asset or liability. • Level 3 Inputs: Unobservable inputs for the asset or liability used to measure fair value to the extent that observable inputs are not available, thereby allowing for situations in which there is little, if any, market activity for the asset or liability at measurement date. On a recurring basis, the Company measures certain financial assets and liabilities at fair value. The following tables summarize the fair value of the Company’s financial assets and liabilities measured at fair value on a recurring basis by level within the fair value hierarchy (in thousands): September 30, 2022 Valuation Amortized Gross Gross Aggregate Assets: Cash equivalents: Money market funds Level 1 $ 210,088 $ — $ — $ 210,088 Short-term investments: Commercial paper Level 2 23,825 — ( 100 ) 23,725 Government bonds Level 2 35,354 — ( 218 ) 35,136 Total assets $ 269,267 $ — $ ( 318 ) $ 268,949 December 31, 2021 Valuation Amortized Gross Gross Aggregate Assets: Cash equivalents: Money market funds Level 1 $ 74,109 $ — $ — $ 74,109 Short-term investments: Commercial paper Level 2 85,352 — ( 27 ) 85,325 Corporate bonds Level 2 48,814 — ( 24 ) 48,790 Government bonds Level 2 33,809 — ( 52 ) 33,757 Total assets $ 242,084 $ — $ ( 103 ) $ 241,981 For the three and nine months ended September 30, 2022 and 2021, the Company recognized no material realized gains or losses on financial instruments.

Balance Sheet Components

Balance Sheet Components	9 Months Ended
	Sep. 30, 2022
Disclosure Of Balance Sheet Components [Abstract]
Balance Sheet Components	4. Balance Sheet Components Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets consisted of the following (in thousands): September 30, December 31, Prepaid research and development costs $ 3,562 $ 3,002 Prepaid insurance 1,243 1,282 Other prepaid expenses 396 231 Other current assets 57 463 Total prepaid expenses and other current assets $ 5,258 $ 4,978 Property and Equipment, Net Property and equipment, net, consisted of the following (in thousands): September 30, December 31, Leasehold improvements $ 17,179 $ 16,594 Laboratory equipment 1,552 1,353 Furniture and fixtures 682 649 Computer equipment and software 33 41 Total property and equipment, gross 19,446 18,637 Less: accumulated depreciation ( 2,353 ) ( 789 ) Total property and equipment, net $ 17,093 $ 17,848 The Company recognized depreciation for property and equipment of $ 0.5 million and $ 0.6 million for the three months ended September 30, 2022 and 2021, respectively, and $ 1.6 million and $ 1.6 million for the nine months ended September 30, 2022 and 2021, respectively. Accrued Liabilities Accrued liabilities consisted of the following (in thousands): September 30, December 31, Accrued research and development expenses $ 7,054 $ 2,404 Accrued compensation 3,792 3,573 Accrued professional services 313 1,274 Accrued construction costs — 1,917 Other accrued expenses 164 82 Total accrued liabilities $ 11,323 $ 9,250

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2022
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	5. Commitments and Contingencies Leases The Company leases its offices and laboratory in Brisbane, California, or the Brisbane Lease, under a ten-year noncancelable lease agreement that ends in October 2031 with a ten-year renewable option. In November 2021, the Company subleased unoccupied space for two years starting from December 2021 for aggregate sublease payments of $ 3.4 million. The sublease income, while it reduces the rent expense, is not considered in the value of the right-of-use assets or lease liabilities. The Company’s sublease income was $ 0.4 million and $ 1.2 million for the three and nine months ended September 30, 2022, respectively. As of September 30, 2022, the operating lease right-of-use assets were $ 19.6 million and lease liabilities were $ 33.7 million on the condensed consolidated balance sheet. The weighted-average remaining lease term is 9.1 years. The weighted-average incremental borrowing rate used to measure the operating lease liability is 8.4 % . Operating lease costs were $ 0.5 million and $ 1.1 million for the three months ended September 30, 2022 and 2021, respectively, and $ 1.5 million and $ 2.0 million for the nine months ended September 30, 2022 and 2021, respectively. Variable lease payments were $ 0.1 million and $ 36,000 for the three months ended September 30, 2022 and 2021, respectively, and $ 0.7 million and $ 0.1 million for the nine months ended September 30, 2022 and 2021, respectively. Future minimum lease payments and related lease liabilities as of September 30, 2022, were as follows: (in thousands) 2022 (remaining three months) $ 1,175 2023 4,742 2024 4,907 2025 5,079 2026 and thereafter 32,833 Total undiscounted lease payments 48,736 Less: Imputed interest ( 15,030 ) Total $ 33,706 License and Other Agreements In November 2011, the Company entered into an exclusive licensing agreement, or the Stanford Agreement, with The Board of Trustees of the Leland Stanford Junior University, or Stanford, whereby the Company was granted an exclusive, worldwide, royalty-bearing, sublicensable license, under certain patent rights, or the Licensed Patents, to make, use, offer for sale, sell, import and otherwise commercialize products covered by the Licensed Patents for human or animal diseases, disorders or conditions. Under the Stanford Agreement, the Company made an upfront payment and is obligated to pay Stanford annual license maintenance fees, potential future milestone payments totaling up to $ 0.5 million, and royalty payments at a rate equal to a low single-digit percentage of worldwide net sales of licensed products. The Company did not achieve any milestones or make any milestone payments for the three and nine months ended September 30, 2022 and 2021. In December 2016, the Company entered into a sponsored research agreement, with a not-for-profit entity to perform research on multiple sclerosis. The sponsored research agreement was amended in March 2019, or as amended, the Sponsored Research Agreement. Under the terms of the Sponsored Research Agreement, the Company may receive up to $ 0.7 million in funding. If within 15 years of the end of the Sponsored Research Agreement, the Company files a marketing authorization application for a product treating multiple sclerosis, the Company will be obligated to pay milestone payments up to four times the amounts received under the Sponsored Research Agreement. The Company has received $ 0.6 million in funding to date, which was recorded as other income. The Company recognized no income during the nine months ended September 30, 2022 and $ 0.1 million in income during the nine months ended September 30, 2021. Guarantees and Indemnifications In the normal course of business, the Company enters into agreements that contain a variety of representations and provide for general indemnification. The Company’s exposure under these agreements is unknown because it involves claims that may be made against the Company in the future. To date, the Company has no t paid any claims or been required to defend any action related to its indemnification obligations. As of September 30, 2022, the Company did no t have any material indemnification claims that were probable or reasonably possible and consequently has not recorded related liabilities.

Stockholder's Equity

Stockholder's Equity	9 Months Ended
	Sep. 30, 2022
Stockholders' Equity Note [Abstract]
Stockholders' Equity	6. Stockholders’ Equity Private Placement On July 11, 2022, the Company sold in a private placement an aggregate of 9,013,834 shares of common stock, pre-funded warrants to purchase up to 24,696,206 shares of its common stock and accompanying common warrants to purchase up to 8,427,508 shares of its common stock. The offering price per share and accompanying common warrant was $ 3.87125 per share and the offering price per pre-funded warrant and accompanying common warrant was $ 3.87025 per share, which equals the per share offering price for the shares of common stock less the $ 0.001 exercise price for each such pre-funded warrant. The pre-funded warrants remain exercisable until exercised in full. The common warrants have an exercise price of $ 5.806875 per share and expire on June 30, 2025 . An entity related to one of the Company’s directors participated in the Private Placement and purchased 2,453,988 shares of common stock and accompanying common warrants to purchase up to an additional 613,497 shares of common stock for an aggregate price of approximately $ 9.5 million. Both the pre-funded and common warrants are immediately exercisable, subject to beneficial ownership limitations. The Company may not effect the exercise of any pre-funded warrant, and a holder will not be entitled to exercise any portion of any pre-funded warrant that, upon giving effect to such exercise, would cause: (i) the aggregate number of shares of common stock beneficially owned by such holder, together with its affiliates, to exceed 9.99 % of the total number of shares of common stock outstanding immediately after giving effect to the exercise or (ii) the combined voting power of the Company’s securities beneficially owned by such holder, together with its affiliates, to exceed 9.99 % of the combined voting power of all of the Company’s securities immediately outstanding after giving effect to the exercise, which such percentage may be changed at the holder’s election to a higher or lower percentage not in excess of 19.99 % upon at least 61 day s’ notice to the Company. The Company may not effect the exercise of any common warrant, and a holder will not be entitled to exercise any portion of any common warrant that, upon giving effect to such exercise, would cause the aggregate number of shares of common stock beneficially owned by such holder, together with its affiliates, to exceed 4.99 %, 9.99 % or 19.99% (as applicable pursuant to the holder’s common warrant) of the total number of shares of common stock outstanding immediately after giving effect to the exercise, which such percentage may be changed at the holder’s election to a higher or lower percentage, including 9.99%, 14.99 % or 19.99 %, and not in excess of 19.99 %, upon at least 61 days’ notice to the Company. The warrants meet the criteria for equity classification and were therefore recorded at fair value as of the grant date as a component of stockholders’ equity within additional paid-in capital. As of September 30, 2022, no pre-funded or common warrants were exercised, and there were pre-funded and common warrants to purchase an aggregate of 33,123,714 shares of common stock outstanding. The 24,696,206 shares of common stock issuable upon the exercise of the pre-funded warrants and the 8,427,508 shares of common stock issuable upon the exercise of the common warrants are not included in the number of issued and outstanding shares of common stock as of September 30, 2022. At-the-Market Offering In August 2021, the Company entered into a sales agreement with Cowen and Company LLC, or Cowen, as sales agent, pursuant to which the Company may issue and sell shares of its common stock for an aggregate maximum offering price of $ 100.0 million under an at-the-market offering program, or 2021 ATM program. The Company will pay Cowen up to 3 % of gross proceeds for the common stock sold through the 2021 ATM program. As of September 30, 2022, no shares of common stock have been sold under the 2021 ATM program. Common Stock The Company has reserved the following shares of common stock for issuance as follows: September 30, December 31, Stock options issued and outstanding 8,178,136 5,662,824 Stock options reserved for 2020 Incentive Award Plan 334,001 2,039,951 Unvested restricted stock units outstanding 591,608 50,000 Common stock reserved for 2021 ATM program 5,265,929 5,265,929 Common stock reserved for Employee Stock Purchase 1,075,042 729,775 Common stock reserved for Employment Inducement 1,703,000 — Common stock reserved for pre-funded warrants 24,696,206 — Common stock reserved for common warrants 8,427,508 — Total common stock reserved 50,271,430 13,748,479

Equity Incentive Plans

Equity Incentive Plans	9 Months Ended
	Sep. 30, 2022
Share-Based Payment Arrangement [Abstract]
Equity Incentive Plans	7. Equity Incentive Plans In July 2020, the Company’s board of directors and stockholders adopted and approved the 2020 Incentive Award Plan, or the 2020 Plan, and the Employee Stock Purchase Plan, or the ESPP, which became effective in connection with the Company’s initial public offering, or the IPO. The Company may not grant any additional awards under the 2011 Equity Incentive Plan, or the 2011 Plan. The 2011 Plan will continue to govern outstanding equity awards granted thereunder. 2020 Equity Incentive Plan The number of shares of common stock reserved for issuance under the 2020 Plan automatically increases on the first day of January, in an amount equal to 4 % of the total number of shares of the Company’s capital stock outstanding on the last day of the preceding year, or a lesser number of shares determined by the Company’s board of directors. Awards granted under the 2020 Plan expire no later than ten years from the date of grant. For Incentive Stock Options, or ISOs, and Nonstatutory Stock Options, or NSOs, the option price shall not be less than 100 % of the estimated fair value on the date of grant. Options granted typically vest over a four-year period but may be granted with different vesting terms. As of September 30, 2022, there were 334,001 shares available for issuance under the 2020 Plan. 2022 Employment Inducement Award Plan In July 2022, the Company’s board of directors adopted the Annexon, Inc. 2022 Employment Inducement Award Plan, or the Inducement Plan, and together with the 2011 Plan and the 2020 Plan, the Plans. The Inducement Plan was adopted by the Company’s board of directors without stockholder approval pursuant to Nasdaq Marketplace Rule 5635(c)(4), or Rule 5635(c)(4). In accordance with Rule 5635(c)(4), awards made under the Inducement Plan may only be granted to newly hired employees as an inducement material to the employees entering into employment with the Company. Awards granted under the Inducement Plan expire no later than ten years from the date of grant. An aggregate of 2,000,000 shares of common stock were reserved for issuance under the Inducement Plan. As of September 30, 2022, there were 1,703,000 shares available for issuance under the Inducement Plan. Stock Options The following table presents stock option activity under the Plans for the period: Number of Weighted- Weighted- Aggregate Balances as of December 31, 2021 5,662,824 $ 16.98 8.26 $ 10,186 Stock options granted 3,645,435 5.59 Stock options exercised ( 11,474 ) 5.65 Stock options forfeited ( 1,118,649 ) 16.24 Balances as of September 30, 2022 8,178,136 $ 12.02 8.39 $ 6,084 Exercisable as of September 30, 2022 2,968,956 $ 12.75 7.17 $ 2,494 The total intrinsic value of options exercised were $ 2,500 and $ 0.7 million during the three months ended September 30, 2022 and 2021, respectively, and $ 5,000 and $ 3.9 million for the nine months ended September 30, 2022 and 2021, respectively. The intrinsic value is the difference between the fair value of the Company’s common stock at the time of exercise and the exercise price of the stock option. The weighted-average grant date fair value of options granted to employees during the nine months ended September 30, 2022 and 2021 was $ 3.93 and $ 19.41 per share, respectively. As of September 30, 2022, the total unrecognized stock-based compensation cost related to outstanding unvested stock options that are expected to vest was $ 42.7 million, which the Company expects to recognize over an estimated weighted-average period of 2.6 years. Restricted Stock Units RSUs are equity awards that entitle the holder to receive shares of the Company’s common stock upon vesting. The RSUs cannot be transferred and the awards are subject to forfeiture if the holder’s employment terminates prior to the release of the vesting restrictions. The RSUs generally vest over a three-year period in equal amounts on an annual basis, provided the employee remains continuously employed with the Company. The fair value of the RSUs is equal to the closing price of the Company’s common stock on the grant date. A summary of RSU activity under the 2020 Plan and related information is as follows: Number of Shares Weighted-Average Grant Date Fair Value Per Share Unvested as of December 31, 2021 50,000 $ 12.84 Granted 600,583 5.40 Cancelled ( 58,975 ) 8.04 Unvested as of September 30, 2022 591,608 $ 5.76 As of September 30, 2022, unrecognized stock-based compensation expense related to outstanding unvested RSUs was $ 2.8 million, which is expected to be recognized over a weighted-average period of 2.5 years. Employee Stock Purchase Plan The ESPP enables eligible employees to purchase shares of the Company's common stock at the end of each offering period at a price equal to 85 % of the fair market value of the shares on the first business day or the last business day of the offering period, whichever is lower. Eligible employees generally include all employees. Share purchases are funded through payroll deductions of at least 1 %, and up to 15 % of an employee’s eligible compensation for each payroll period. The number of shares reserved for issuance under the ESPP increase automatically on the first day of each fiscal year, by a number equal to the least of 360,086 shares, 1 % of the shares of common stock outstanding on the last day of the immediately preceding fiscal year, or such number of shares determined by the Company’s board of directors. As of September 30, 2022, 1,075,042 shares were available for future purchase. The ESPP generally provides for six-month consecutive offering periods beginning on May 15 th and November 15 th of each year. The ESPP is a compensatory plan as defined by the authoritative guidance for stock compensation. As such, stock-based compensation expense has been recorded for the three and nine months ended September 30, 2022. The stock-based compensation expense related to the ESPP was $ 29,000 and $ 42,000 for the three months ended September 30, 2022 and 2021, respectively, and $ 0.1 million and $ 0.1 million for the nine months ended September 30, 2022 and 2021, respectively. Stock-Based Compensation Expense The total stock-based compensation expense related to all equity-based awards recognized in the period was as follows (in thousands): Three Months Ended Nine Months Ended 2022 2021 2022 2021 Research and development $ 2,433 $ 2,382 $ 6,509 $ 6,330 General and administrative 2,478 2,046 7,174 5,577 Total stock-based compensation expense $ 4,911 $ 4,428 $ 13,683 $ 11,907 To determine the value of stock option awards for stock-based compensation purposes, the Company uses the Black-Scholes option pricing model and the assumptions discussed below. Each of these inputs is subjective and generally requires significant judgment. The fair value of each award issued was estimated on the date of grant using the Black-Scholes option pricing model with the following assumptions: Three Months Ended Nine Months Ended 2022 2021 2022 2021 Expected term (in years) 5.77 - 6.08 4.33 - 6.08 5.50 - 6.08 4.33 - 6.08 Expected volatility 81.70 % - 82.70 % 88.3 % - 89 % 78.80 % - 82.80 % 88.3 % - 90.7 % Risk-free interest rate 2.92 % - 3.61 % 0.70 % - 1.10 % 1.49 % - 3.61 % 0.35 % - 1.10 % Dividend yield — — — —

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2022
Income Tax Disclosure [Abstract]
Income Taxes	8. Income Taxes For the three and nine months ended September 30, 2022 and 2021, the Company incurred insignificant amounts for an income tax provision. The U.S. federal and California deferred tax assets generated from the Company’s net operating losses have been fully reserved, as the Company believes it is not more likely than not that the benefit will be realized.

Net Loss Per Share Attributable

Net Loss Per Share Attributable to Common Stockholders	9 Months Ended
	Sep. 30, 2022
Earnings Per Share [Abstract]
Net Loss Per Share Attributable to Common Stockholders	9. Net Loss Per Share Attributable to Common Stockholders The Company calculates basic net loss per share by dividing net loss by the weighted-average number of shares of common stock outstanding, excluding restricted common stock. The weighted-average number of shares of common stock used in the basic and diluted net loss per share calculation include the pre-funded warrants issued in connection with the Private Placement as the pre-funded warrants are exercisable at any time for nominal cash consideration. As of September 30, 2022, no pre-funded warrants have been exercised and there were pre-funded warrants to purchase an aggregate of 24,696,206 shares of common stock outstanding. The Company has generated a net loss in all periods presented, so the basic and diluted net loss per share are the same, as the inclusion of the potentially dilutive securities would be anti-dilutive. The following outstanding potentially dilutive shares have been excluded from the calculation of diluted net loss per share due to their anti-dilutive effect: Nine Months Ended 2022 2021 Stock options to purchase common stock 8,178,136 5,918,981 Shares subject to Employee Stock Purchase Plan 110,897 9,538 Unvested restricted stock units 591,608 — Common warrants to purchase common stock 8,427,508 — Total 17,308,149 5,928,519

Basis of Presentation and Sig_2

Basis of Presentation and Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2022
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States, or GAAP, and applicable rules and regulations of the SEC regarding interim financial reporting. The condensed consolidated balance sheet as of September 30, 2022, the condensed consolidated statements of operations, comprehensive loss, stockholders’ equity for the three and nine months ended September 30, 2022 and 2021 and the condensed consolidated statements of cash flows for the nine months ended September 30, 2022 and 2021 are unaudited. These unaudited condensed consolidated financial statements have been prepared on the same basis as the annual consolidated financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary to present fairly the Company’s consolidated financial position, results of operations and cash flows for the interim period presented. The financial data and the other financial information contained in these notes to the condensed consolidated financial statements related to the three and nine month periods are also unaudited. The results of operations for the three and nine months ended September 30, 2022 are not necessarily indicative of the results to be expected for the year ending December 31, 2022 or for any other future annual or interim period. The condensed consolidated balance sheet as of December 31, 2021 included herein was derived from the audited financial statements as of that date. These unaudited condensed consolidated financial statements should be read in conjunction with the Company's audited consolidated financial statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2021, filed with the SEC on March 1, 2022.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported expenses during the reporting period. On an ongoing basis, management evaluates its estimates, including but not limited to fair value of investments, useful lives for property and equipment, incremental borrowing rate used in lease accounting, stock options, income taxes and certain accruals. The Company evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors and adjusts those estimates and assumptions when facts and circumstances dictate. Actual results could differ from those estimates.
Principles of Consolidation	Principles of Consolidation The condensed consolidated financial statements include the operations of Annexon, Inc. and its wholly-owned subsidiary and include the results of operations and cash flows of these entities. All intercompany balances and transactions have been eliminated in consolidation.
Cash, Cash Equivalents and Restricted Cash	Cash, Cash Equivalents and Restricted Cash The Company considers all highly liquid instruments with an original maturity of three months or less at time of purchase to be cash equivalents. Cash equivalents, which includes amounts invested in money market funds, are stated at fair value. Restricted cash as of September 30, 2022 relates to the letters of credit established for the Company’s office leases. The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the condensed consolidated balance sheets that sum to the total of the same amounts shown in the condensed consolidated statements of cash flows: September 30, December 31, Cash $ 570 $ 734 Cash equivalents 210,088 74,109 Cash and cash equivalents 210,658 74,843 Restricted cash 1,032 1,166 Cash, cash equivalents and restricted cash $ 211,690 $ 76,009
Short-Term Investments	Short-Term Investments Short-term investments 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. The Company determines the appropriate classification of its investments in debt securities at the time of purchase. Available-for-sale securities with original maturities beyond three months at the date of purchase are classified as current based on their availability for use in current operations. The Company evaluates, on a quarterly basis, its available-for-sale debt securities for potential impairment. For available-for-sale debt securities in an unrealized loss position, the Company assesses whether such declines are due to credit loss based on factors such as changes to the rating of the security by a ratings agency, market conditions and supportable forecasts of economic and market conditions, among others. If credit loss exists, the Company assesses whether it has plans to sell the security or it is more likely than not it will be required to sell any available-for-sale debt security before recovery of its amortized cost basis. If either condition is met, the security’s amortized cost basis is written down to fair value and is recognized through interest and other income (expense), net. If neither condition is met, declines as a result of credit losses, if any, are recognized as an allowance for credit loss, limited to the amount of unrealized loss, through interest and other income (expense), net. Any portion of the unrealized loss that is not a result of a credit loss, is recognized in other comprehensive income (loss). Realized gains and losses, if any, on available-for-sale debt securities are included in interest and other income (expense), net. The cost of investments sold is based on the specific-identification method. Interest on available-for-sale debt securities is included in interest and other income (expense), net.
Warrants	Warrants Warrants are accounted for as either derivative liabilities or as equity instruments depending on the specific terms of the agreement. The Company’s pre-funded and common warrants are equity-classified instruments that were recorded in additional paid-in capital at issuance and are not subject to remeasurement. The Company periodically evaluates changes in facts and circumstances that could impact the classification of warrants.
Research and Development Expense	Research and Development Expense Research and development expenses consist primarily of direct and indirect costs incurred for the development of the Company’s product candidates. Direct expenses include (i) preclinical and clinical outside service costs associated with discovery, preclinical and clinical testing of the Company’s product candidates; (ii) professional services agreements with third-party contract organizations, investigative clinical trial sites and consultants that conduct research and development activities on the Company’s behalf; (iii) contract manufacturing costs to produce clinical trial materials; and (iv) laboratory supplies and materials. Indirect expenses include (A) compensation and personnel-related expenses (including stock-based compensation); (B) allocated expenses for facilities and depreciation; and (C) other indirect costs. Research and development costs are expensed as incurred. Payments made to third parties are under agreements that are generally cancelable by the Company. Advance payments for research and development activities are deferred as prepaid expenses. The prepaid amounts are expensed as the related services are performed. The Company estimates preclinical studies and clinical trial expenses based on the services performed pursuant to contracts with research institutions and clinical research organizations that conduct and manage preclinical studies and clinical trials on the Company’s behalf. In accruing service fees, the Company estimates the period over which services will be performed and the level of effort to be expended in each period. These estimates are based on the Company’s communications with the third-party service providers and on information available at each balance sheet date. If the actual timing of the performance of services or the level of effort varies significantly from the estimate, the Company will adjust the accrual accordingly to reflect the best information available at the time of the financial statement issuance. The Company has not experienced any material differences between accrued costs and actual costs incurred since its inception.
Stock-Based Compensation	Stock-Based Compensation The Company accounts for stock-based compensation arrangements with employees, non-employee directors and consultants using a fair value method which requires the recognition of compensation expense for costs related to all stock-based payments, including stock options and restricted stock units, or RSUs. The fair value method requires the Company to estimate the fair value of stock options to employees and non-employee directors on the date of grant using the Black-Scholes option pricing model. The fair value of RSU awards is based on the fair value of the underlying common stock as of the grant date. The Company grants certain employees performance-based stock options. For awards that include performance conditions, no compensation cost is recognized until the performance goals are probable of being met, at which time the cumulative compensation expense from the service inception date would be recognized. Stock-based compensation costs are based on the fair value of the underlying option calculated using the Black-Scholes option pricing model and recognized as expense on a straight-line basis (for all but performance-based awards for which the accelerated method is used) over the requisite service period, which is the vesting period. Determining the appropriate fair value model and related assumptions requires judgment, including estimating the fair value of the underlying common stock, expected term, expected stock price volatility, risk-free interest rate and dividend yield. The Company accounts for forfeitures as they occur.
Net Loss Per Share Attributable to Common Stockholders	Net Loss Per Share Attributable to Common Stockholders Basic net loss per share attributable to common stockholders is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of shares of common stock outstanding for the period, without consideration for potential dilutive shares of common stock. As the Company was in a loss position for all periods presented, basic net loss per share attributable to common stockholders is the same as diluted net loss per share attributable to common stockholders because the effects of potentially dilutive securities are antidilutive.
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments that potentially subject the Company to concentrations of credit risk consist primarily of cash and cash equivalents and short-term investments. The Company’s cash and cash equivalents and short-term investments are held by high credit quality financial institutions in the United States. At times, such deposits may be in excess of the Federal Depository Insurance Corporation insured limits. Management believes that the financial institutions are financially sound, and accordingly, minimal credit risk exists with respect to the financial institutions.
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements 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 No. 2020-06” ). ASU No. 2020-06 simplifies the accounting for convertible instruments. The guidance removes certain accounting models that separate the embedded conversion features from the host contract for convertible instruments. The Company adopted ASU 2020-06 effective as of January 1, 2022 . The adoption of ASU 2020-06 did not have an impac t on the Company’s condensed consolidated financial statements.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements The Company does not believe that any recently issued effective pronouncements, or pronouncements issued but not yet effective, if adopted, would have a material impact on its financial position or results of operations.

Basis of Presentation and Sig_3

Basis of Presentation and Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2022
Accounting Policies [Abstract]
Schedule of Reconciliation of Cash, Cash Equivalents and Restricted Cash	The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the condensed consolidated balance sheets that sum to the total of the same amounts shown in the condensed consolidated statements of cash flows: September 30, December 31, Cash $ 570 $ 734 Cash equivalents 210,088 74,109 Cash and cash equivalents 210,658 74,843 Restricted cash 1,032 1,166 Cash, cash equivalents and restricted cash $ 211,690 $ 76,009

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2022
Fair Value Disclosures [Abstract]
Summary of Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis	The following tables summarize the fair value of the Company’s financial assets and liabilities measured at fair value on a recurring basis by level within the fair value hierarchy (in thousands): September 30, 2022 Valuation Amortized Gross Gross Aggregate Assets: Cash equivalents: Money market funds Level 1 $ 210,088 $ — $ — $ 210,088 Short-term investments: Commercial paper Level 2 23,825 — ( 100 ) 23,725 Government bonds Level 2 35,354 — ( 218 ) 35,136 Total assets $ 269,267 $ — $ ( 318 ) $ 268,949 December 31, 2021 Valuation Amortized Gross Gross Aggregate Assets: Cash equivalents: Money market funds Level 1 $ 74,109 $ — $ — $ 74,109 Short-term investments: Commercial paper Level 2 85,352 — ( 27 ) 85,325 Corporate bonds Level 2 48,814 — ( 24 ) 48,790 Government bonds Level 2 33,809 — ( 52 ) 33,757 Total assets $ 242,084 $ — $ ( 103 ) $ 241,981

Balance Sheet Components (Table

Balance Sheet Components (Tables)	9 Months Ended
	Sep. 30, 2022
Disclosure Of Balance Sheet Components [Abstract]
Summary of Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets consisted of the following (in thousands): September 30, December 31, Prepaid research and development costs $ 3,562 $ 3,002 Prepaid insurance 1,243 1,282 Other prepaid expenses 396 231 Other current assets 57 463 Total prepaid expenses and other current assets $ 5,258 $ 4,978
Summary of Property and Equipment, Net	Property and equipment, net, consisted of the following (in thousands): September 30, December 31, Leasehold improvements $ 17,179 $ 16,594 Laboratory equipment 1,552 1,353 Furniture and fixtures 682 649 Computer equipment and software 33 41 Total property and equipment, gross 19,446 18,637 Less: accumulated depreciation ( 2,353 ) ( 789 ) Total property and equipment, net $ 17,093 $ 17,848
Summary of Accrued Liabilities	Accrued liabilities consisted of the following (in thousands): September 30, December 31, Accrued research and development expenses $ 7,054 $ 2,404 Accrued compensation 3,792 3,573 Accrued professional services 313 1,274 Accrued construction costs — 1,917 Other accrued expenses 164 82 Total accrued liabilities $ 11,323 $ 9,250

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2022
Commitments and Contingencies Disclosure [Abstract]
Future Minimum Lease Payments and Related Lease Liabilities	Future minimum lease payments and related lease liabilities as of September 30, 2022, were as follows: (in thousands) 2022 (remaining three months) $ 1,175 2023 4,742 2024 4,907 2025 5,079 2026 and thereafter 32,833 Total undiscounted lease payments 48,736 Less: Imputed interest ( 15,030 ) Total $ 33,706

Stockholder's Equity (Tables)

Stockholder's Equity (Tables)	9 Months Ended
	Sep. 30, 2022
Stockholders' Equity Note [Abstract]
Schedule of Common Stock Reserved for Future Issuance	The Company has reserved the following shares of common stock for issuance as follows: September 30, December 31, Stock options issued and outstanding 8,178,136 5,662,824 Stock options reserved for 2020 Incentive Award Plan 334,001 2,039,951 Unvested restricted stock units outstanding 591,608 50,000 Common stock reserved for 2021 ATM program 5,265,929 5,265,929 Common stock reserved for Employee Stock Purchase 1,075,042 729,775 Common stock reserved for Employment Inducement 1,703,000 — Common stock reserved for pre-funded warrants 24,696,206 — Common stock reserved for common warrants 8,427,508 — Total common stock reserved 50,271,430 13,748,479

Equity Incentive Plans (Tables)

Equity Incentive Plans (Tables)	9 Months Ended
	Sep. 30, 2022
Share-Based Payment Arrangement [Abstract]
Summary of Stock Option Activity	The following table presents stock option activity under the Plans for the period: Number of Weighted- Weighted- Aggregate Balances as of December 31, 2021 5,662,824 $ 16.98 8.26 $ 10,186 Stock options granted 3,645,435 5.59 Stock options exercised ( 11,474 ) 5.65 Stock options forfeited ( 1,118,649 ) 16.24 Balances as of September 30, 2022 8,178,136 $ 12.02 8.39 $ 6,084 Exercisable as of September 30, 2022 2,968,956 $ 12.75 7.17 $ 2,494
Summary of RSU Activity under 2020 Plan	A summary of RSU activity under the 2020 Plan and related information is as follows: Number of Shares Weighted-Average Grant Date Fair Value Per Share Unvested as of December 31, 2021 50,000 $ 12.84 Granted 600,583 5.40 Cancelled ( 58,975 ) 8.04 Unvested as of September 30, 2022 591,608 $ 5.76
Summary of Stock-Based Compensation Expense	The total stock-based compensation expense related to all equity-based awards recognized in the period was as follows (in thousands): Three Months Ended Nine Months Ended 2022 2021 2022 2021 Research and development $ 2,433 $ 2,382 $ 6,509 $ 6,330 General and administrative 2,478 2,046 7,174 5,577 Total stock-based compensation expense $ 4,911 $ 4,428 $ 13,683 $ 11,907
Summary of Fair Value of Each Award Issued Estimated on the Date of Grant Using the Black-Scholes Option Pricing Model	The fair value of each award issued was estimated on the date of grant using the Black-Scholes option pricing model with the following assumptions: Three Months Ended Nine Months Ended 2022 2021 2022 2021 Expected term (in years) 5.77 - 6.08 4.33 - 6.08 5.50 - 6.08 4.33 - 6.08 Expected volatility 81.70 % - 82.70 % 88.3 % - 89 % 78.80 % - 82.80 % 88.3 % - 90.7 % Risk-free interest rate 2.92 % - 3.61 % 0.70 % - 1.10 % 1.49 % - 3.61 % 0.35 % - 1.10 % Dividend yield — — — —

Net Loss Per Share Attributab_2

Net Loss Per Share Attributable to Common Stockholders (Tables)	9 Months Ended
	Sep. 30, 2022
Earnings Per Share [Abstract]
Summary of Outstanding Potentially Dilutive Shares Excluded From Calculation of Diluted Net Loss Per Share	The following outstanding potentially dilutive shares have been excluded from the calculation of diluted net loss per share due to their anti-dilutive effect: Nine Months Ended 2022 2021 Stock options to purchase common stock 8,178,136 5,918,981 Shares subject to Employee Stock Purchase Plan 110,897 9,538 Unvested restricted stock units 591,608 — Common warrants to purchase common stock 8,427,508 — Total 17,308,149 5,928,519

Organization - Additional Infor

Organization - Additional Information (Detail) - USD ($) $ in Thousands	Jul. 11, 2022	Sep. 30, 2022	Dec. 31, 2021
Accounting Policies [Abstract]
Accumulated deficit		$ 403,879	$ 296,315
Cash and cash equivalents and short-term investments		$ 269,500
Net proceeds from private placement	$ 122,600

Basis of Presentation and Sig_4

Basis of Presentation and Significant Accounting Policies - Schedule of Reconciliation of Cash, Cash Equivalents and Restricted Cash (Detail) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents [Abstract]
Cash	$ 570	$ 734
Cash equivalents	210,088	74,109
Cash and cash equivalents	210,658	74,843
Restricted cash	1,032	1,166
Cash, cash equivalents and restricted cash	$ 211,690	$ 76,009

Basis of Presentation and Sig_5

Basis of Presentation and Significant Accounting Policies - Additional Information (Detail) - ASU 2020-06 [Member]	Sep. 30, 2022
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Change in accounting principle, ASU adopted	true
Change in accounting principle, ASU, adoption date	Jan. 01, 2022
Change in accounting principle, ASU, Immaterial effect	true

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis (Detail) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	$ 269,267	$ 242,084
Gross Unrealized Holding Losses	(318)	(103)
Aggregate Fair Value	268,949	241,981
Level 1 [Member] | Money Market Funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	210,088	74,109
Aggregate Fair Value	210,088	74,109
Level 2 [Member] | Commercial Paper [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	23,825	85,352
Gross Unrealized Holding Losses	(100)	(27)
Aggregate Fair Value	23,725	85,325
Level 2 [Member] | Government Bonds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	35,354	33,809
Gross Unrealized Holding Losses	(218)	(52)
Aggregate Fair Value	$ 35,136	33,757
Level 2 [Member] | Corporate Bonds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost		48,814
Gross Unrealized Holding Losses		(24)
Aggregate Fair Value		$ 48,790

Balance Sheet Components - Summ

Balance Sheet Components - Summary of Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Prepaid Expense and Other Assets, Current [Abstract]
Prepaid research and development costs	$ 3,562	$ 3,002
Prepaid insurance	1,243	1,282
Other prepaid expenses	396	231
Other current assets	57	463
Total prepaid expenses and other current assets	$ 5,258	$ 4,978

Balance Sheet Components - Su_2

Balance Sheet Components - Summary of Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Property Plant And Equipment [Line Items]
Total property and equipment, gross	$ 19,446	$ 18,637
Less: accumulated depreciation	(2,353)	(789)
Total property and equipment, net	17,093	17,848
Leasehold Improvements [Member]
Property Plant And Equipment [Line Items]
Total property and equipment, gross	17,179	16,594
Laboratory Equipment [Member]
Property Plant And Equipment [Line Items]
Total property and equipment, gross	1,552	1,353
Furniture and Fixtures [Member]
Property Plant And Equipment [Line Items]
Total property and equipment, gross	682	649
Computer Equipment and Software [Member]
Property Plant And Equipment [Line Items]
Total property and equipment, gross	$ 33	$ 41

Balance Sheet Components - Addi

Balance Sheet Components - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Prepaid Expense and Other Assets, Current [Abstract]
Depreciation expense	$ 0.5	$ 0.6	$ 1.6	$ 1.6

Balance Sheet Components - Su_3

Balance Sheet Components - Summary of Accrued Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Accrued Liabilities, Current [Abstract]
Accrued research and development expenses	$ 7,054	$ 2,404
Accrued compensation	3,792	3,573
Accrued professional services	313	1,274
Accrued construction costs		1,917
Other accrued expenses	164	82
Total accrued liabilities	$ 11,323	$ 9,250

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail)		1 Months Ended		3 Months Ended						9 Months Ended
	Nov. 01, 2021 USD ($)	Mar. 31, 2019 USD ($)	Nov. 30, 2011 USD ($)	Sep. 30, 2022 USD ($) Claim	Jun. 30, 2022 USD ($)	Mar. 31, 2022 USD ($)	Sep. 30, 2021 USD ($)	Jun. 30, 2021 USD ($)	Mar. 31, 2021 USD ($)	Sep. 30, 2022 USD ($) Claim	Sep. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)
Gain Contingencies [Line Items]
Aggregate sublease payment receivable	$ 3,400,000
Sublease income				$ 400,000						$ 1,200,000
Operating lease right-of-use asset				19,616,000						19,616,000		$ 20,333,000
Lease liabilities				$ 33,706,000						$ 33,706,000
Weighted average incremental borrowing rate				8.40%						8.40%
Operating lease costs				$ 500,000			$ 1,100,000			$ 1,500,000	$ 2,000,000
Variable lease payments				100,000			36,000			700,000	100,000
Income (loss)				(35,054,000)	$ (37,137,000)	$ (35,373,000)	$ (35,598,000)	$ (31,294,000)	$ (26,060,000)	(107,564,000)	(92,952,000)
Loss contingency accrual				$ 0						$ 0
Indemnification Agreement [Member]
Gain Contingencies [Line Items]
Loss contingency pending claims | Claim				0						0
Stanford Agreement [Member] | Research and Development Arrangement [Member]
Gain Contingencies [Line Items]
Sponsor research agreements, commitment amount			$ 500,000
Proceeds from funding										$ 600,000
Sponsored Research Agreement [Member]
Gain Contingencies [Line Items]
Maximum threshold period allowed for filing market authorization		15 years
Income (loss)										$ 0	$ 100,000
Sponsored Research Agreement [Member] | Research and Development Arrangement [Member]
Gain Contingencies [Line Items]
Maximum expected research funding		$ 700,000
Brisbane, California [Member]
Gain Contingencies [Line Items]
Operating lease, term of contract				10 years						10 years
Operating lease, expiration month and year										2031-10
Operating lease, renewal term				10 years						10 years
Operating lease right-of-use asset				$ 19,600,000						$ 19,600,000
Lease liabilities				$ 33,700,000						$ 33,700,000
Weighted average remaining lease term				9 years 1 month 6 days						9 years 1 month 6 days

Commitments and Contingencies_2

Commitments and Contingencies - Future Minimum Lease Payments and Related Lease Liabilities (Detail) $ in Thousands	Sep. 30, 2022 USD ($)
Commitments and Contingencies Disclosure [Abstract]
2022 (remaining six months)	$ 1,175
2023	4,742
2024	4,907
2025	5,079
2026 and thereafter	32,833
Total undiscounted lease payments	48,736
Less: Imputed interest	(15,030)
Lease liabilities	$ 33,706

Stockholder's Equity - Schedule

Stockholder's Equity - Schedule of Common Stock Reserved for Future Issuance (Detail) - shares	Sep. 30, 2022	Dec. 31, 2021
Class Of Stock [Line Items]
Common stock reserved	8,178,136	5,662,824
Common stock reserved	334,001
Common stock reserved	50,271,430	13,748,479
Stock Options Issued and Outstanding [Member]
Class Of Stock [Line Items]
Common stock reserved	8,178,136	5,662,824
Stock Options Reserved for 2020 Incentive Award Plan [Member]
Class Of Stock [Line Items]
Common stock reserved	334,001	2,039,951
Unvested Restricted Stock Units Outstanding [Member]
Class Of Stock [Line Items]
Common stock reserved	591,608	50,000
Common Stock Reserved for Employee Stock Purchase Plan [Member]
Class Of Stock [Line Items]
Common stock reserved	1,075,042	729,775
Employment Inducement Award Plan [Member]
Class Of Stock [Line Items]
Common stock reserved	1,703,000
Pre-Funded Warrants [Member]
Class Of Stock [Line Items]
Common stock reserved	24,696,206
Common Warrants [Member]
Class Of Stock [Line Items]
Common stock reserved	8,427,508
2021 ATM Program [Member]
Class Of Stock [Line Items]
Common stock reserved	5,265,929	5,265,929

Stockholder's Equity - Addition

Stockholder's Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended		9 Months Ended
	Jul. 11, 2022	Jul. 31, 2022	Aug. 31, 2021	Sep. 30, 2022	Dec. 31, 2021
Class Of Stock [Line Items]
Common stock				$ 48	$ 39
Exercise of common warrant, description				The Company may not effect the exercise of any common warrant, and a holder will not be entitled to exercise any portion of any common warrant that, upon giving effect to such exercise, would cause the aggregate number of shares of common stock beneficially owned by such holder, together with its affiliates, to exceed 4.99%, 9.99% or 19.99% (as applicable pursuant to the holder’s common warrant) of the total number of shares of common stock outstanding immediately after giving effect to the exercise, which such percentage may be changed at the holder’s election to a higher or lower percentage, including 9.99%, 14.99% or 19.99%, and not in excess of 19.99%, upon at least 61 days’ notice to the Company.
Pre-funded Warrants [Member]
Class Of Stock [Line Items]
Purchase of shares				0
Offering price per share	$ 3.87025
Combined voting power maximum	19.99%
Notice period	61 days
Warrants outstanding				24,696,206
Pre-funded Warrants [Member] | Maximum [Member]
Class Of Stock [Line Items]
Purchase of shares	24,696,206
Purchase price per share	$ 0.001
Pre-funded Warrants [Member] | Minimum [Member]
Class Of Stock [Line Items]
Total number of common shares outstanding	9.99%
Combined voting power	9.99%
Warrants or Common Warrants [Member]
Class Of Stock [Line Items]
Purchase of shares				0
Offering price per share	$ 3.87125
Purchase price per share	$ 5.806875
Warrant expiration date	Jun. 30, 2025
Combined voting power	9.99%
Combined voting power maximum	19.99%
Notice period	61 days
Warrants outstanding				8,427,508
Warrants or Common Warrants [Member] | Maximum [Member]
Class Of Stock [Line Items]
Purchase of shares	8,427,508
Combined voting power	19.99%
Warrants or Common Warrants [Member] | Minimum [Member]
Class Of Stock [Line Items]
Total number of common shares outstanding	4.99%
Combined voting power	14.99%
Private Placement [Member]
Class Of Stock [Line Items]
Sale of shares	9,013,834	2,453,988
Warrants outstanding				33,123,714
Additional common shares purchased		613,497
Exchange value		$ 9,500
Sales Agreement with Cowen and Company LLC [Member] | 2021 ATM Program [Member]
Class Of Stock [Line Items]
Common stock			$ 100,000
Percentage of gross proceeds of common stock to be paid			3%

Equity Incentive Plans - Additi

Equity Incentive Plans - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Jul. 31, 2022	Dec. 31, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of number of shares of capital stock outstanding on last day of preceding year			4%
Stock option grants description			Awards granted under the 2020 Plan expire no later than ten years from the date of grant. For Incentive Stock Options, or ISOs, and Nonstatutory Stock Options, or NSOs, the option price shall not be less than 100% of the estimated fair value on the date of grant. Options granted typically vest over a four-year period but may be granted with different vesting terms.
Option expiry period			10 years
Vesting Period			4 years
Options available for future grant	334,001		334,001
Intrinsic value of options exercised	$ 2,500	$ 700,000	$ 5,000	$ 3,900,000
Weighted- average exercise price per share, Stock options granted			$ 5.59
Unrecognized stock-based compensation cost expected period for recognition			2 years 7 months 6 days
Common stock for future issuance	50,271,430		50,271,430			13,748,479
Total stock-based compensation expense	$ 4,911,000	4,428,000	$ 13,683,000	$ 11,907,000
Employees [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted- average exercise price per share, Stock options granted			$ 3.93	$ 19.41
2022 Employment Inducement Award Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options available for future grant	1,703,000		1,703,000		2,000,000
Incentive Stock Options, or ISOs, and Nonstatutory Stock Options, or NSOs [Member] | Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Purchase of Common stock at end of each offering period at price equal to percentage of fair market value of shares			100%
Options Issued and Outstanding [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized stock-based compensation cost	$ 42,700,000		$ 42,700,000
Restricted Stock Units [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized stock-based compensation cost	$ 2,800,000		$ 2,800,000
Unrecognized stock-based compensation cost expected period for recognition			2 years 6 months
Employee Stock Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Purchase of Common stock at end of each offering period at price equal to percentage of fair market value of shares			85%
Share purchases funded through payroll deductions minimum percentage of employee's eligible compensation	1%		1%
Share purchases funded through payroll deductions maximum percentage of employee's eligible compensation	15%		15%
Common stock for future issuance	1,075,042		1,075,042			729,775
Maximum number of shares to be issued in accordance with plan as a proportion of outstanding capital stock	360,086		360,086
Percentage of shares of common stock outstanding on last day of immediately preceding fiscal year			1%
Total stock-based compensation expense	$ 29,000	$ 42,000	$ 100,000	$ 100,000

Equity Incentive Plans - Summar

Equity Incentive Plans - Summary of Stock Option Activity (Detail) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2022 USD ($) $ / shares shares	Dec. 31, 2021 USD ($) $ / shares shares
Share-Based Payment Arrangement [Abstract]
Number of shares, Beginning balance | shares	5,662,824
Number of shares, Stock options granted | shares	3,645,435
Number of shares, Stock options exercised | shares	(11,474)
Number of shares, Stock options forfeited | shares	(1,118,649)
Number of shares, Ending balance | shares	8,178,136	5,662,824
Number of shares, Exercisable | shares	2,968,956
Weighted- average exercise price per share, Beginning balance | $ / shares	$ 16.98
Weighted- average exercise price per share, Stock options granted | $ / shares	5.59
Weighted- average exercise price per share, Stock options exercised | $ / shares	5.65
Weighted average exercise price per share, Stock options forfeited | $ / shares	16.24
Weighted- average exercise price per share, Ending balance | $ / shares	12.02	$ 16.98
Weighted- average exercise price per share, Exercisable | $ / shares	$ 12.75
Weighted- average remaining contractual term	8 years 4 months 20 days	8 years 3 months 3 days
Weighted- average remaining contractual term, Exercisable	7 years 2 months 1 day
Aggregate intrinsic value | $	$ 6,084	$ 10,186
Aggregate intrinsic value, Exercisable | $	$ 2,494

Equity Incentive Plans - Summ_2

Equity Incentive Plans - Summary of RSU Activity under 2020 Plan (Detail)	9 Months Ended
	Sep. 30, 2022 $ / shares shares
Share-Based Payment Arrangement [Abstract]
Number of Shares, Unvested as of December 31, 2021 | shares	50,000
Number of Shares, Granted | shares	600,583
Number of Shares, Cancelled | shares	(58,975)
Number of Shares, Unvested as of September 30, 2022 | shares	591,608
Weighted-Average Grant Date Fair Value Per Share, Granted Unvested as of December 31, 2021 | $ / shares	$ 12.84
Weighted-Average Grant Date Fair Value Per Share, Granted | $ / shares	5.40
Weighted-Average Grant Date Fair Value Per Share, Cancelled | $ / shares	8.04
Weighted-Average Grant Date Fair Value Per Share, Granted Unvested as of September 30, 2022 | $ / shares	$ 5.76

Equity Incentive Plans - Summ_3

Equity Incentive Plans - Summary of Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	$ 4,911	$ 4,428	$ 13,683	$ 11,907
Research and Development [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	2,433	2,382	6,509	6,330
General and Administrative [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	$ 2,478	$ 2,046	$ 7,174	$ 5,577

Equity Incentive Plans - Summ_4

Equity Incentive Plans - Summary of Fair Value of Each Award Issued Estimated on the Date of Grant Using the Black-Scholes Option Pricing Model (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility, Minimum	81.70%	88.30%	78.80%	88.30%
Expected volatility, Maximum	82.70%	89%	82.80%	90.70%
Risk-free interest rate, Minimum	2.92%	0.70%	1.49%	0.35%
Risk-free interest rate, Maximum	3.61%	1.10%	3.61%	1.10%
Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	5 years 9 months 7 days	4 years 3 months 29 days	5 years 6 months	4 years 3 months 29 days
Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	6 years 29 days	6 years 29 days	6 years 29 days	6 years 29 days

Net Loss Per Share Attributab_3

Net Loss Per Share Attributable to Common Stockholders - Additional Information (Detail) - Pre-funded Warrants [Member]	Sep. 30, 2022 shares
Class of Warrant or Right [Line Items]
Warrants exercised	0
Warrants outstanding	24,696,206

Net Loss Per Share Attributab_4

Net Loss Per Share Attributable to Common Stockholders - Summary of Outstanding Potentially Dilutive Shares Excluded From Calculation of Diluted Net Loss Per Share (Detail) - shares	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of diluted net loss per share	17,308,149	5,928,519
Shares Subject to Employee Stock Purchase Plan [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of diluted net loss per share	110,897	9,538
Stock Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of diluted net loss per share	8,178,136	5,918,981
Unvested Restricted Stock Units [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of diluted net loss per share	591,608
Common Warrants to Purchase Common Stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of diluted net loss per share	8,427,508