Annexon (ANNX) 10-K 6 Mar 23 2022 FY Annual report Financial data

Cover Page

Cover Page - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Mar. 01, 2023	Jun. 30, 2022
Document Type	10-K
Document Annual Report	true
Document Transition Report	false
Amendment Flag	false
Document Period End Date	Dec. 31, 2022
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	FY
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	Non-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
Entity Public Float			$ 125
ICFR Auditor Attestation Flag	false
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Auditor Name	KPMG LLP
Auditor Location	San Francisco, CA
Auditor Firm ID	185
Documents Incorporated by Reference	Portions of the Registrant’s definitive proxy statement relating to the 2023 Annual Meeting of Stockholders, which will be filed with the Securities and Exchange Commission within 120 days after the end of the Registrant’s fiscal year ended December 31, 2022, are incorporated by reference into Part III of this Annual Report on Form 10-K.
Common Stock [Member]
Entity Common Stock, Shares Outstanding		50,493,255
Prefunded Warrant [Member]
Entity Common Stock, Shares Outstanding		24,696,206

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 140,020	$ 74,843
Short-term investments	102,637	167,872
Prepaid expenses and other current assets	5,441	4,978
Total current assets	248,098	247,693
Restricted cash	1,032	1,166
Property and equipment, net	16,838	17,848
Operating lease right-of-use assets	19,128	20,333
Total assets	285,096	287,040
Current liabilities:
Accounts payable	7,416	11,153
Accrued liabilities	13,448	9,250
Operating lease liabilities, current	1,316	1,202
Other current liabilities	180	139
Total current liabilities	22,360	21,744
Operating lease liabilities, non-current	31,542	33,387
Total liabilities	53,902	55,131
Commitments and contingencies (Note 5)
Stockholders’ equity:
Common stock, $0.001 par value; 300,000,000 shares authorized as of December 31, 2022 and 2021, respectively; 47,722,995 and 38,560,854 shares issued and outstanding as of December 31, 2022 and 2021, respectively	48	39
Additional paid-in capital	669,780	528,365
Accumulated other comprehensive loss	(372)	(180)
Accumulated deficit	(438,262)	(296,315)
Total stockholders' equity	231,194	231,909
Total liabilities and stockholders’ equity	$ 285,096	$ 287,040

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2022	Dec. 31, 2021
Statement of Financial Position [Abstract]
Common stock, par value per share	$ 0.001	$ 0.001
Common stock, shares authorized	300,000,000	300,000,000
Common stock, shares issued	47,722,995	38,560,854
Common stock, shares outstanding	47,722,995	38,560,854

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Operating expenses:
Research and development	$ 112,501	$ 100,066
General and administrative	33,098	30,647
Total operating expenses	145,599	130,713
Loss from operations	(145,599)	(130,713)
Interest and other income, net	3,652	390
Net loss	(141,947)	(130,323)
Net loss attributable to common stockholders	$ (141,947)	$ (130,323)
Net loss per share attributable to common stockholders, basic	$ (2.60)	$ (3.40)
Net loss per share attributable to common stockholders, diluted	$ (2.60)	$ (3.40)
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic	54,673,572	38,316,273
Weighted-average shares used in computing net loss per share attributable to common stockholders, diluted	54,673,572	38,316,273

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Statement of Comprehensive Income [Abstract]
Net loss	$ (141,947)	$ (130,323)
Other comprehensive gain (loss):
Foreign currency translation adjustment	1	(5)
Unrealized loss on available-for-sale securities	(193)	(98)
Comprehensive loss	$ (142,139)	$ (130,426)

Consolidated Statements of Stoc

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	16,262		16,262
Stock option exercises	1,610	$ 1	1,609
Stock option exercises, Shares		391,349
Issuance of common stock per Employee Stock Purchase Plan purchase	185		185
Issuance of common stock per Employee Stock Purchase Plan purchase, Shares		11,887
Foreign currency translation adjustment	(5)			(5)
Unrealized loss on available-for-sale securities	(98)			(98)
Net loss	(130,323)				(130,323)
Ending Balance, Values at Dec. 31, 2021	231,909	$ 39	528,365	(180)	(296,315)
Ending Balance, Shares at Dec. 31, 2021		38,560,854
Stock-based compensation	18,516		18,516
Stock option exercises	$ 80		80
Stock option exercises, Shares	15,364	15,364
Issuance of common stock, pre-funded warrants and common warrants, net of issuance costs	$ 122,488	$ 9	122,479
Issuance of common stock, pre-funded warrants and common warrants, net of issuance costs, Shares		9,013,834
Issuance of common stock per Employee Stock Purchase Plan purchase	340		340
Issuance of common stock per Employee Stock Purchase Plan purchase, Shares		121,126
Restricted common stock vested in the period		11,817
Foreign currency translation adjustment	1			1
Unrealized loss on available-for-sale securities	(193)			(193)
Net loss	(141,947)				(141,947)
Ending Balance, Values at Dec. 31, 2022	$ 231,194	$ 48	$ 669,780	$ (372)	$ (438,262)
Ending Balance, Shares at Dec. 31, 2022		47,722,995

Consolidated Statements of St_2

Consolidated Statements of Stockholders' Equity (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2022 USD ($)
Statement of Stockholders' Equity [Abstract]
Stock issuance costs	$ 7,988
Proceeds from the issuance of common stock, pre-funded warrants and common warrants - related party	$ 9,500

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Operating activities:
Net loss	$ (141,947)	$ (130,323)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	2,106	2,141
Accretion of discount on available-for-sale securities	73	1,253
Stock-based compensation	18,516	16,262
Reduction in the carrying amount of right-of-use assets	1,205	1,273
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(463)	(2,612)
Accounts payable	(287)	3,859
Accrued liabilities	6,178	773
Operating lease liabilities	(1,731)	1,125
Other current liabilities	41	139
Net cash used in operating activities	(116,309)	(106,110)
Investing activities:
Purchases of property and equipment	(6,526)	(1,654)
Purchases of available-for-sale securities	(113,197)	(225,601)
Proceeds from sale of available-for-sale securities		5,993
Proceeds from maturities of available-for-sale securities	178,166	133,026
Net cash provided by (used in) investing activities	58,443	(88,236)
Financing activities:
Proceeds from the exercise of common stock options	80	1,610
Proceeds from employee stock plan purchases	340	185
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	(7,988)
Net cash provided by financing activities	122,908	1,795
Increase (decrease) in cash, cash equivalents and restricted cash	65,042	(192,551)
Effect of exchange rate changes on cash, cash equivalents and restricted cash	1	(5)
Cash, cash equivalents and restricted cash
Beginning of period	76,009	268,565
End of period	141,052	76,009
Supplemental disclosure of cash flow information:
Cash paid for amounts included in the measurement of lease liability	10,078	996
Non-cash investing and financing activities:
Purchases of property and equipment included in accounts payable and accrued liabilities	$ 110	5,540
Right-of-use assets obtained in exchange for lease liability		21,084
Construction-in-progress obtained in exchange for tenant improvement allowance from lessors		$ 10,860

Organization

Organization	12 Months Ended
	Dec. 31, 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 December 31, 2022, had an accumulated deficit of $ 438.3 million and cash and cash equivalents and short-term investments of $ 242.7 million. The Company has historically funded its operations through the issuance of shares of its redeemable convertible preferred stock, common stock and warrants. 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 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	12 Months Ended
	Dec. 31, 2022
Accounting Policies [Abstract]
Basis of Presentation and Significant Accounting Policies	2. Basis of Presentation and Significant Accounting Policies Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America, or 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. Management evaluates its estimates, including but not limited to the fair value of investments, stock options, income taxes, clinical trial accruals and stock-based compensation. 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 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. Segments The Company’s chief operating decision maker is its Chief Executive Officer. The Chief Executive Officer reviews financial information on an aggregate basis for the purposes of evaluating financial performance and allocating the Company’s resources. Accordingly, the Company has determined that it operates in one segment. 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 December 31, 2022 relates to the letters of credit established for the Company’s office lease. The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the consolidated balance sheets that sum to the total of the same amounts shown in the consolidated statements of cash flows: December 31, 2022 2021 Cash $ 570 $ 734 Cash equivalents 139,450 74,109 Cash and cash equivalents 140,020 74,843 Restricted cash 1,032 1,166 Cash, cash equivalents and restricted cash $ 141,052 $ 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. Property and Equipment, Net Property and equipment are carried at cost less accumulated depreciation. Depreciation is computed using the straight-line method over the estimated useful lives of the respective assets. Depreciation begins at the time the asset is placed in service. Maintenance and repairs are charged to operations as incurred. Upon sale or retirement of assets, the cost and related accumulated depreciation are removed from the balance sheet and the resulting gain or loss is reflected in operations in the period realized. The useful lives of the property and equipment are as follows: Computer equipment 3 years Lab equipment and furniture and fixtures 5 years Leasehold improvements Shorter of remaining lease term or estimated useful life Impairment of Long-Lived Assets The Company evaluates its long-lived assets, including property and equipment, for impairment whenever events or changes in circumstances indicate that the carrying amount of these assets may not be recoverable. Recoverability of these assets is measured by comparison of the carrying amount of each asset to the future undiscounted cash flows the asset is expected to generate over its remaining life. When indications of impairment are present and the estimated undiscounted future cash flows from the use of these assets is less than the assets’ carrying value, the related assets will be written down to fair value. There were no impairments of the Company’s long-lived assets for the periods presented. Leases The Company determines if an arrangement is a lease at inception. Upon adoption of Accounting Standards Codification 842, Leases , as of January 1, 2021, the Company includes operating leases in operating lease right of use, or ROU, assets, current and noncurrent operating lease liabilities in the Company’s consolidated balance sheets. The 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 liabilities are recognized at the commencement date based on the present value of lease payments over the lease term. The Company measures the ROU assets based on the associated lease liabilities adjusted for any lease incentives such as tenant improvement allowances. As most of the leases do not provide an implicit rate, the Company generally uses its incremental borrowing rate based on the estimated rate of interest for collateralized borrowing over a similar term of the lease payments at the commencement date. The Company’s lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise the option. Lease expense for lease payments is recognized on a straight-line basis, net of sublease income, over the lease term. As a practical expedient, the Company elected, for all facility leases, not to separate non-lease components from lease components and instead to account for each separate lease component and its associated non-lease components as a single lease component. The Company elected to exclude from its balance sheets recognition of leases having a term of 12 months or less (short-term leases). Income Taxes Income taxes are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and operating loss and tax credit carry forwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. Valuation allowances are established when necessary to reduce deferred taxes to the amounts expected to be realized. The Company recognizes benefits of uncertain tax positions if it is more likely than not that such positions will be sustained upon examination based solely on their technical merit, as the largest amount of benefit that is more likely than not to be realized upon the ultimate settlement. The Company’s policy is to recognize interest and penalties related to the underpayment of income taxes as a component of income tax expense or benefit. To date, there have been no interest or penalties charged in relation to the unrecognized tax benefits. Commitments and Contingencies Liabilities for loss contingencies arising from claims, assessments, litigation, fines, and penalties and other sources are recorded when it is probable that a liability has been incurred and the amount can be reasonably estimated. Legal costs incurred in connection with loss contingencies are expensed as incurred. 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. The Company also estimates manufacturing costs based on services performed pursuant to contracts with contract manufacturing organizations that develop and manufacture product 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 and 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-employees on the date of grant using the Black-Scholes option pricing model. The fair value of RSU awards are based on the fair value of the underlying common stock as of the grant date. 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 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 impact on the Company’s consolidated financial statements. Recently Issued Accounting Pronouncements The Company has reviewed the FASB issued ASU accounting pronouncements and interpretations thereof that have effectiveness dates during the periods reported and in future periods. The Company has carefully considered the new pronouncements that alter previous generally accepted accounting principles and do not believe that any new or modified principles will have a material impact on the Company’s reported financial position or operations in the near term. The applicability of any standard is subject to the formal review of the Company’s financial management.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 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): December 31, 2022 Valuation Amortized Gross Gross Aggregate Assets: Cash equivalents: Money market funds Level 1 $ 139,450 $ — $ — $ 139,450 Short-term investments: Commercial paper Level 2 42,467 — ( 82 ) 42,385 Corporate bonds Level 2 35,638 14 — 35,652 Government bonds Level 2 24,804 — ( 204 ) 24,600 Total assets $ 242,359 $ 14 $ ( 286 ) $ 242,087 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 All of the investments held as of December 31, 2022 had original maturities of less than two years . As of December 31, 2022, all of the investments are scheduled to mature in 12 months . For the years ended December 31, 2022 and 2021, the Company recognized no material realized gains or losses on financial instruments.

Balance Sheet Components

Balance Sheet Components	12 Months Ended
	Dec. 31, 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): December 31, 2022 2021 Prepaid research and development costs $ 3,805 $ 3,002 Prepaid insurance 755 1,282 Other prepaid expenses 678 231 Other current assets 203 463 Total prepaid expenses and other current assets $ 5,441 $ 4,978 Property and Equipment, Net Property and equipment, net consisted of the following (in thousands): December 31, 2022 2021 Leasehold improvements $ 17,231 $ 16,594 Laboratory equipment 1,764 1,353 Furniture and fixtures 692 649 Computer equipment and software 34 41 Total property and equipment, gross 19,721 18,637 Less: accumulated depreciation ( 2,883 ) ( 789 ) Total property and equipment, net $ 16,838 $ 17,848 Total depreciation expense recognized for the years ended December 31, 2022 and 2021 was $ 2.1 million and $ 2.1 million, respectively. Accrued Liabilities Accrued liabilities consisted of the following (in thousands): December 31, 2022 2021 Accrued research and development expenses $ 7,720 $ 2,404 Accrued compensation 5,299 3,573 Accrued professional services 394 1,274 Accrued construction costs — 1,917 Other accrued expenses 35 82 Total accrued liabilities $ 13,448 $ 9,250

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 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 $ 1.6 million and $ 0.1 million for the year ended December 31, 2022 and 2021, respectively. As of December 31, 2022, the operating lease right-of-use assets were $ 19.1 million and lease liabilities were $ 32.9 million in the consolidated balance sheet. The weighted average remaining lease term is 8.8 years. The weighted average incremental borrowing rate used to measure the operating lease liability is 8.4 % . Operating lease cost for the years ended December 31, 2022 and 2021 was $ 2.1 million and $ 2.9 million, respectively. Variable lease payments for the years ended December 31, 2022 and 2021 were $ 1.0 million and $ 0.4 million, respectively. Future minimum lease payments and related lease liabilities as of December 31, 2022, were as follows: (in thousands) 2023 $ 4,198 2024 4,893 2025 5,065 2026 5,242 2027 and thereafter 28,025 Total undiscounted lease payments 47,423 Less: Imputed interest ( 14,565 ) Total $ 32,858 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 $ 500,000 , 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 years ended December 31, 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. Under the terms of the Sponsored Research Agreement, as amended, 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 interest and other income. The Company recognized no income during the year ended December 31, 2022 and $ 0.1 million in income during the year ended December 31, 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 December 31, 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	12 Months Ended
	Dec. 31, 2022
Stockholders' Equity Note [Abstract]
Stockholder's Equity	6. Stockholder’s 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 . The private placement resulted in net proceeds of $ 122.5 million, after deducting placement agent fees and expenses. 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 days’ 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 December 31, 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 December 31, 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 December 31, 2022, no shares of common stock had been sold under the 2021 ATM program. In February 2023, an entity related to one of the Company’s directors purchased 2,646,458 shares of common stock at a price of $ 6.80 per share through the 2021 ATM program, resulting in net proceeds to the Company of approximately $ 17.5 million, after deducting placement agent fees. Common Stock The holders of the Company’s common stock have one vote for each share of common stock. Common stockholders are entitled to dividends when, as, and if declared by the Board of Directors. The holders have no preemptive or other subscription rights and there are no redemption or sinking fund provisions with respect to such shares. As of December 31, 2022, no dividends had been declared by the Board of Directors. The Company reserved the following shares of common stock for issuance as follows: December 31, 2022 2021 Stock options issued and outstanding 8,152,093 5,662,824 Stock options reserved for 2020 Incentive Award Plan 478,109 2,039,951 Unvested restricted stock units outstanding 550,236 50,000 Common stock reserved for 2021 ATM program 5,265,929 5,265,929 Common stock reserved for Employee Stock Purchase 994,257 729,775 Common stock reserved for Employment Inducement 1,610,600 — Common stock reserved for pre-funded warrants 24,696,206 — Common stock reserved for common warrants 8,427,508 — Total common stock reserved 50,174,938 13,748,479

Equity Incentive Plan

Equity Incentive Plan	12 Months Ended
	Dec. 31, 2022
Share-Based Payment Arrangement [Abstract]
Equity Incentive Plan	7. Equity Incentive Plan 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 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 increase 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 the 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 December 31, 2022 and 2021, there were 478,109 and 2,039,951 shares available for issuance under the 2020 Plan, respectively. 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 December 31, 2022, there were 1,610,600 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 3,767,835 $ 5.59 Stock options exercised ( 15,364 ) $ 5.28 Stock options forfeited ( 1,263,202 ) $ 15.78 Balances as of December 31, 2022 8,152,093 $ 11.92 8.09 $ 3,329 Exercisable as of December 31, 2022 3,406,230 $ 12.87 6.94 $ 1,428 The total intrinsic value of options exercised during the years ended December 31, 2022 and 2021 was $ 11,500 and $ 6.4 million, 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 years ended December 31, 2022 and 2021 was $ 3.94 and $ 18.83 per share, respectively. As of December 31, 2022, the total unrecognized stock-based compensation cost related to outstanding unvested stock options that are expected to vest was $ 37.4 million, which the Company expects to recognize over an estimated weighted-average period of 2.4 years. Restricted Stock Units RSUs are share awards that entitle the holder to receive freely tradeable 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 our equity incentive 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 604,583 5.40 Vested ( 11,817 ) 12.84 Cancelled ( 92,530 ) 7.37 Unvested as of December 31, 2022 550,236 $ 5.58 As of December 31, 2022, unrecognized stock-based compensation expense related to outstanding unvested RSUs was $ 2.4 million, which is expected to be recognized over a weighted-average period of 2.3 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 included 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, 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 December 31, 2022, 994,257 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 years ended December 31, 2022 and 2021. The stock-based compensation expense related to the ESPP for the years ended December 31, 2022 and 2021 was $ 0.1 million and $ 0.1 million, respectively. Stock-Based Compensation Expense The total stock-based compensation expense recognized was as follows (in thousands): Year Ended 2022 2021 Research and development $ 8,874 $ 8,610 General and administrative 9,642 7,652 Total stock-based compensation expense $ 18,516 $ 16,262 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. Fair Value of Common Stock —The fair value of each share of underlying common stock is based on the closing price of the Company’s common stock as reported on the date of grant on the Nasdaq Global Select Market. Expected Term —The expected term represents the period that the stock-based awards are expected to be outstanding and is determined using the simplified method (based on the mid-point between the vesting date and the end of the contractual term). The Company continues using the simplified method as it does not have sufficient historical exercise data to provide a reasonable basis upon which to estimate expected term due to the limited period of time its equity shares have been publicly traded. Expected Volatility —Because the Company does not have sufficient trading history for its common stock, the expected volatility was estimated based on the average volatility for comparable publicly traded life sciences companies over a period equal to the expected term of the stock option grants. The comparable companies were chosen based on the similar size, stage in life cycle or area of specialty. Risk-Free Interest Rate —The risk-free interest rate is based on the U.S. Treasury zero coupon issues in effect at the time of grant for periods corresponding with the expected term of the option. Dividend Yield —The Company has never paid dividends on its common stock and have no plans to pay dividends on its common stock. Therefore, the Company used an expected dividend yield of zero. The fair value of each stock option issued was estimated on the date of grant using the Black-Scholes option pricing model with the following assumptions: Year Ended 2022 2021 Expected term (in years) 5.50 - 6.08 4.33 - 6.08 Expected volatility 78.80 % - 85.90 % 88.30 % - 90.70 % Risk-free interest rate 1.49 % - 4.19 % 0.35 % - 1.31 % Dividend yield — —

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Income Taxes	8. Income Taxes For financial reporting purposes, loss before provision for income taxes, includes the following components (in thousands): Year Ended December 31, 2022 2021 Domestic $ ( 141,939 ) $ ( 130,313 ) Foreign ( 8 ) ( 10 ) Loss before income taxes $ ( 141,947 ) $ ( 130,323 ) For each of the years ended December 31, 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. Reconciliation of income tax computed at federal statutory rates to the reported provision for income taxes was as follows (in thousands): Year Ended December 31, 2022 2021 Tax provision at U.S. statutory rate $ ( 29,809 ) $ ( 27,368 ) Stock-based compensation 2,362 794 Research and development tax credits ( 2,836 ) ( 2,392 ) Change in valuation allowance 30,148 25,911 Section 382 limitations — 2,922 Other 135 133 Provision for income taxes $ — $ — Deferred Tax Assets and Liabilities The tax effects of temporary differences that give rise to significant portions of the Company’s deferred tax assets and liabilities are as follows (in thousands): December 31, 2022 2021 Deferred Tax Assets: Net operating loss carryforwards $ 63,551 $ 57,073 Research and development credits 11,095 7,367 Other intangibles 4 5 Accruals and reserves 974 686 Stock-based compensation 4,551 3,041 Capitalized research and development 19,744 — Lease liabilities 6,946 7,340 Unrealized gain/loss on investments — 240 Total gross deferred tax assets 106,865 75,752 Less: valuation allowance ( 100,778 ) ( 69,147 ) Total deferred tax assets, net $ 6,087 $ 6,605 Deferred Tax Liabilities: Fixed assets $ ( 2,043 ) $ ( 2,290 ) Right-of-use assets ( 4,044 ) ( 4,315 ) Total gross deferred tax liabilities ( 6,087 ) ( 6,605 ) Net deferred tax assets $ — $ — As of December 31, 2022, the Company had $ 286.5 million of federal and $ 71.1 million of state net operating loss, or NOL, carryforwards available to offset future taxable income. Under the Tax Cuts and Jobs Act of 2017, or the Tax Act, federal NOLs generated after December 31, 2017 will be carried forward indefinitely with the yearly NOL utilization limited to 80 % of taxable income. The Company had $ 243.4 million of such federal NOLs that do not expire. If not utilized, the federal carryforward losses generated prior to 2018 and the state carryforward losses will expire in various amounts beginning in 2031 . As of December 31, 2022, the Company had approximately $ 10.9 million of federal and $ 6.7 million of state credit carryforwards available to offset future taxable income. If not utilized, these credit carryforwards will expire in various amounts for federal purposes beginning in 2031 . The state credits do not expire. In assessing the realization of deferred tax assets, management considers whether it is more likely than not that some portion or all of the deferred tax assets will not be realized. Management believes that, based on available evidence, both positive and negative, it is more likely than not that the deferred tax assets will not be utilized; therefore, a full valuation allowance has been recorded. The Company’s valuation allowance increased by $ 31.6 million and $ 24.4 million for the years ended December 31, 2022 and 2021, respectively. The changes in the 2022 valuation allowance were primarily due to the addition of capitalized research and development costs, current year loss carryforwards and research and development credits. The changes in the 2021 valuation allowance were primarily due to the addition of the current year loss carryforwards and research and development credits. Utilization of the net operating loss carryforwards and credits may be subject to an annual limitation due to the ownership change limitations provided by the Internal Revenue Code of 1986, as amended, and similar state provisions. The annual limitations may result in the expiration of net operating losses and credits before utilization. The Company performed a Section 382 analysis through December 31, 2021. Federal net operating losses carryforwards of $ 286.4 million and state and local net operating loss carryforwards of $ 36.4 million are not expected to expire unutilized as a result of ownership changes identified through December 31, 2021. The Company has identified $ 0.1 million and $ 34.7 million of federal and state net operating losses, respectively, that will expire unused due to ownership changes, and federal credits of $ 3.7 million that will not be able to be utilized due to ownership change limitation; these amounts have been excluded from the deferred tax assets table above. Further ownership changes subsequent to December 31, 2021 may be identified which could result in limitations to the amount of net operating losses and credits which may be utilized prior to expiration. Uncertain Tax Benefits The Company has the following activity relating to the gross amount of unrecognized tax benefits (in thousands): Year Ended December 31, 2022 2021 Beginning balance $ 1,794 $ 1,576 Decreases based on tax positions related to — ( 789 ) Additions based on tax positions related to 932 1,007 Ending balance $ 2,726 $ 1,794 None of these uncertain tax positions will impact the Company’s effective tax rate if assessed. The Company’s policy is to classify interest and penalties associated with unrecognized tax benefits as income tax expense. The Company had no interest or penalty accruals associated with uncertain tax benefits in its consolidated balance sheet and consolidated statement of operations for the years ended December 31, 2022 and 2021. The Company files income tax returns in the United States, California, Georgia, Indiana, Maryland, Massachusetts, Nebraska, New Jersey, North Carolina, Pennsylvania, Texas and in Australia. The Company is not currently under examination by any major tax jurisdictions nor has it been in the past. The tax years 2011 through 2022 remain effectively open for examination by the Internal Revenue Service and most state tax authorities because of net operating losses and credit carryovers. Although it is reasonably possible that certain unrecognized tax benefits may increase or decrease within the next twelve months due to tax examination changes, settlement activities, expirations of statute of limitations, or the impact on recognition and measurement considerations related to the results of published tax cases or other similar activities, the Company does not anticipated any significant changes to unrecognized tax benefits over the next 12 months.

Net Loss Per Share Attributable

Net Loss Per Share Attributable to Common Stockholders	12 Months Ended
	Dec. 31, 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 December 31, 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: Year Ended 2022 2021 Stock options to purchase common stock 8,152,093 5,662,824 Shares subject to Employee Stock Purchase Plan 46,297 15,924 Unvested restricted stock units 550,236 50,000 Common warrants to purchase common stock 8,427,508 — Total 17,176,134 5,728,748

Basis of Presentation and Sig_2

Basis of Presentation and Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2022
Accounting Policies [Abstract]
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America, or 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. Management evaluates its estimates, including but not limited to the fair value of investments, stock options, income taxes, clinical trial accruals and stock-based compensation. 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 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.
Segments	Segments The Company’s chief operating decision maker is its Chief Executive Officer. The Chief Executive Officer reviews financial information on an aggregate basis for the purposes of evaluating financial performance and allocating the Company’s resources. Accordingly, the Company has determined that it operates in one segment.
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 December 31, 2022 relates to the letters of credit established for the Company’s office lease. The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the consolidated balance sheets that sum to the total of the same amounts shown in the consolidated statements of cash flows: December 31, 2022 2021 Cash $ 570 $ 734 Cash equivalents 139,450 74,109 Cash and cash equivalents 140,020 74,843 Restricted cash 1,032 1,166 Cash, cash equivalents and restricted cash $ 141,052 $ 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.
Property and Equipment, Net	Property and Equipment, Net Property and equipment are carried at cost less accumulated depreciation. Depreciation is computed using the straight-line method over the estimated useful lives of the respective assets. Depreciation begins at the time the asset is placed in service. Maintenance and repairs are charged to operations as incurred. Upon sale or retirement of assets, the cost and related accumulated depreciation are removed from the balance sheet and the resulting gain or loss is reflected in operations in the period realized. The useful lives of the property and equipment are as follows: Computer equipment 3 years Lab equipment and furniture and fixtures 5 years Leasehold improvements Shorter of remaining lease term or estimated useful life
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets The Company evaluates its long-lived assets, including property and equipment, for impairment whenever events or changes in circumstances indicate that the carrying amount of these assets may not be recoverable. Recoverability of these assets is measured by comparison of the carrying amount of each asset to the future undiscounted cash flows the asset is expected to generate over its remaining life. When indications of impairment are present and the estimated undiscounted future cash flows from the use of these assets is less than the assets’ carrying value, the related assets will be written down to fair value. There were no impairments of the Company’s long-lived assets for the periods presented.
Leases	Leases The Company determines if an arrangement is a lease at inception. Upon adoption of Accounting Standards Codification 842, Leases , as of January 1, 2021, the Company includes operating leases in operating lease right of use, or ROU, assets, current and noncurrent operating lease liabilities in the Company’s consolidated balance sheets. The 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 liabilities are recognized at the commencement date based on the present value of lease payments over the lease term. The Company measures the ROU assets based on the associated lease liabilities adjusted for any lease incentives such as tenant improvement allowances. As most of the leases do not provide an implicit rate, the Company generally uses its incremental borrowing rate based on the estimated rate of interest for collateralized borrowing over a similar term of the lease payments at the commencement date. The Company’s lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise the option. Lease expense for lease payments is recognized on a straight-line basis, net of sublease income, over the lease term. As a practical expedient, the Company elected, for all facility leases, not to separate non-lease components from lease components and instead to account for each separate lease component and its associated non-lease components as a single lease component. The Company elected to exclude from its balance sheets recognition of leases having a term of 12 months or less (short-term leases).
Income Taxes	Income Taxes Income taxes are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and operating loss and tax credit carry forwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. Valuation allowances are established when necessary to reduce deferred taxes to the amounts expected to be realized. The Company recognizes benefits of uncertain tax positions if it is more likely than not that such positions will be sustained upon examination based solely on their technical merit, as the largest amount of benefit that is more likely than not to be realized upon the ultimate settlement. The Company’s policy is to recognize interest and penalties related to the underpayment of income taxes as a component of income tax expense or benefit. To date, there have been no interest or penalties charged in relation to the unrecognized tax benefits.
Commitments and Contingencies	Commitments and Contingencies Liabilities for loss contingencies arising from claims, assessments, litigation, fines, and penalties and other sources are recorded when it is probable that a liability has been incurred and the amount can be reasonably estimated. Legal costs incurred in connection with loss contingencies are expensed as incurred.
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. The Company also estimates manufacturing costs based on services performed pursuant to contracts with contract manufacturing organizations that develop and manufacture product 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 and 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-employees on the date of grant using the Black-Scholes option pricing model. The fair value of RSU awards are based on the fair value of the underlying common stock as of the grant date. 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 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 impact on the Company’s consolidated financial statements.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements The Company has reviewed the FASB issued ASU accounting pronouncements and interpretations thereof that have effectiveness dates during the periods reported and in future periods. The Company has carefully considered the new pronouncements that alter previous generally accepted accounting principles and do not believe that any new or modified principles will have a material impact on the Company’s reported financial position or operations in the near term. The applicability of any standard is subject to the formal review of the Company’s financial management.

Basis of Presentation and Sig_3

Basis of Presentation and Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 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 consolidated balance sheets that sum to the total of the same amounts shown in the consolidated statements of cash flows: December 31, 2022 2021 Cash $ 570 $ 734 Cash equivalents 139,450 74,109 Cash and cash equivalents 140,020 74,843 Restricted cash 1,032 1,166 Cash, cash equivalents and restricted cash $ 141,052 $ 76,009
Schedule of Useful Lives of Property and Equipment	The useful lives of the property and equipment are as follows: Computer equipment 3 years Lab equipment and furniture and fixtures 5 years Leasehold improvements Shorter of remaining lease term or estimated useful life

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 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): December 31, 2022 Valuation Amortized Gross Gross Aggregate Assets: Cash equivalents: Money market funds Level 1 $ 139,450 $ — $ — $ 139,450 Short-term investments: Commercial paper Level 2 42,467 — ( 82 ) 42,385 Corporate bonds Level 2 35,638 14 — 35,652 Government bonds Level 2 24,804 — ( 204 ) 24,600 Total assets $ 242,359 $ 14 $ ( 286 ) $ 242,087 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)	12 Months Ended
	Dec. 31, 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): December 31, 2022 2021 Prepaid research and development costs $ 3,805 $ 3,002 Prepaid insurance 755 1,282 Other prepaid expenses 678 231 Other current assets 203 463 Total prepaid expenses and other current assets $ 5,441 $ 4,978
Summary of Property and Equipment, Net	Property and equipment, net consisted of the following (in thousands): December 31, 2022 2021 Leasehold improvements $ 17,231 $ 16,594 Laboratory equipment 1,764 1,353 Furniture and fixtures 692 649 Computer equipment and software 34 41 Total property and equipment, gross 19,721 18,637 Less: accumulated depreciation ( 2,883 ) ( 789 ) Total property and equipment, net $ 16,838 $ 17,848
Summary of Accrued Liabilities	Accrued liabilities consisted of the following (in thousands): December 31, 2022 2021 Accrued research and development expenses $ 7,720 $ 2,404 Accrued compensation 5,299 3,573 Accrued professional services 394 1,274 Accrued construction costs — 1,917 Other accrued expenses 35 82 Total accrued liabilities $ 13,448 $ 9,250

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2022
Commitments and Contingencies Disclosure [Abstract]
Future Minimum Lease Payments and Related Lease Liabilities	Future minimum lease payments and related lease liabilities as of December 31, 2022, were as follows: (in thousands) 2023 $ 4,198 2024 4,893 2025 5,065 2026 5,242 2027 and thereafter 28,025 Total undiscounted lease payments 47,423 Less: Imputed interest ( 14,565 ) Total $ 32,858

Stockholder's Equity (Tables)

Stockholder's Equity (Tables)	12 Months Ended
	Dec. 31, 2022
Stockholders' Equity Note [Abstract]
Schedule of Common Stock Reserved for Future Issuance	The Company reserved the following shares of common stock for issuance as follows: December 31, 2022 2021 Stock options issued and outstanding 8,152,093 5,662,824 Stock options reserved for 2020 Incentive Award Plan 478,109 2,039,951 Unvested restricted stock units outstanding 550,236 50,000 Common stock reserved for 2021 ATM program 5,265,929 5,265,929 Common stock reserved for Employee Stock Purchase 994,257 729,775 Common stock reserved for Employment Inducement 1,610,600 — Common stock reserved for pre-funded warrants 24,696,206 — Common stock reserved for common warrants 8,427,508 — Total common stock reserved 50,174,938 13,748,479

Equity Incentive Plan (Tables)

Equity Incentive Plan (Tables)	12 Months Ended
	Dec. 31, 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 3,767,835 $ 5.59 Stock options exercised ( 15,364 ) $ 5.28 Stock options forfeited ( 1,263,202 ) $ 15.78 Balances as of December 31, 2022 8,152,093 $ 11.92 8.09 $ 3,329 Exercisable as of December 31, 2022 3,406,230 $ 12.87 6.94 $ 1,428
Summary of RSU Activity under Equity Incentive Plan	A summary of RSU activity under our equity incentive 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 604,583 5.40 Vested ( 11,817 ) 12.84 Cancelled ( 92,530 ) 7.37 Unvested as of December 31, 2022 550,236 $ 5.58
Summary of Stock-Based Compensation Expense	The total stock-based compensation expense recognized was as follows (in thousands): Year Ended 2022 2021 Research and development $ 8,874 $ 8,610 General and administrative 9,642 7,652 Total stock-based compensation expense $ 18,516 $ 16,262
Summary of Fair Value of Each Stock Option Issued Estimated on the Date of Grant Using the Black-Scholes Option Pricing Model	The fair value of each stock option issued was estimated on the date of grant using the Black-Scholes option pricing model with the following assumptions: Year Ended 2022 2021 Expected term (in years) 5.50 - 6.08 4.33 - 6.08 Expected volatility 78.80 % - 85.90 % 88.30 % - 90.70 % Risk-free interest rate 1.49 % - 4.19 % 0.35 % - 1.31 % Dividend yield — —

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Components of Loss Before Income Taxes	For financial reporting purposes, loss before provision for income taxes, includes the following components (in thousands): Year Ended December 31, 2022 2021 Domestic $ ( 141,939 ) $ ( 130,313 ) Foreign ( 8 ) ( 10 ) Loss before income taxes $ ( 141,947 ) $ ( 130,323 )
Reconciliation of Income Tax Computed at Federal Statutory Rates to Provision for Income Taxes	Reconciliation of income tax computed at federal statutory rates to the reported provision for income taxes was as follows (in thousands): Year Ended December 31, 2022 2021 Tax provision at U.S. statutory rate $ ( 29,809 ) $ ( 27,368 ) Stock-based compensation 2,362 794 Research and development tax credits ( 2,836 ) ( 2,392 ) Change in valuation allowance 30,148 25,911 Section 382 limitations — 2,922 Other 135 133 Provision for income taxes $ — $ —
Deferred Tax Assets and Liabilities	The tax effects of temporary differences that give rise to significant portions of the Company’s deferred tax assets and liabilities are as follows (in thousands): December 31, 2022 2021 Deferred Tax Assets: Net operating loss carryforwards $ 63,551 $ 57,073 Research and development credits 11,095 7,367 Other intangibles 4 5 Accruals and reserves 974 686 Stock-based compensation 4,551 3,041 Capitalized research and development 19,744 — Lease liabilities 6,946 7,340 Unrealized gain/loss on investments — 240 Total gross deferred tax assets 106,865 75,752 Less: valuation allowance ( 100,778 ) ( 69,147 ) Total deferred tax assets, net $ 6,087 $ 6,605 Deferred Tax Liabilities: Fixed assets $ ( 2,043 ) $ ( 2,290 ) Right-of-use assets ( 4,044 ) ( 4,315 ) Total gross deferred tax liabilities ( 6,087 ) ( 6,605 ) Net deferred tax assets $ — $ —
Unrecognized Tax Benefits	The Company has the following activity relating to the gross amount of unrecognized tax benefits (in thousands): Year Ended December 31, 2022 2021 Beginning balance $ 1,794 $ 1,576 Decreases based on tax positions related to — ( 789 ) Additions based on tax positions related to 932 1,007 Ending balance $ 2,726 $ 1,794

Net Loss Per Share Attributab_2

Net Loss Per Share Attributable to Common Stockholders (Tables)	12 Months Ended
	Dec. 31, 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: Year Ended 2022 2021 Stock options to purchase common stock 8,152,093 5,662,824 Shares subject to Employee Stock Purchase Plan 46,297 15,924 Unvested restricted stock units 550,236 50,000 Common warrants to purchase common stock 8,427,508 — Total 17,176,134 5,728,748

Organization - Additional Infor

Organization - Additional Information (Detail) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Accounting Policies [Abstract]
Accumulated deficit	$ 438,262	$ 296,315
Cash and cash equivalents and short-term investments	$ 242,700

Basis of Presentation and Sig_4

Basis of Presentation and Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2022 USD ($) Segment	Dec. 31, 2021 USD ($)
Basis Of Presentation And Significant Accounting Policies [Line Items]
Number of operating segment | Segment	1
Impairments of long-lived assets	$ 0
Operating lease right-of-use assets	19,128,000	$ 20,333,000
Lease liabilities	$ 32,858,000
ASU 2020-06 [Member]
Basis Of Presentation And Significant Accounting Policies [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

Basis of Presentation and Sig_5

Basis of Presentation and Significant Accounting Policies - Schedule of Reconciliation of Cash, Cash Equivalents and Restricted Cash (Detail) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents [Abstract]
Cash	$ 570	$ 734
Cash equivalents	139,450	74,109
Cash and cash equivalents	140,020	74,843
Restricted cash	1,032	1,166
Cash, cash equivalents and restricted cash	$ 141,052	$ 76,009

Basis of Presentation and Sig_6

Basis of Presentation and Significant Accounting Policies - Schedule of Useful Lives of Property and Equipment (Detail)	12 Months Ended
	Dec. 31, 2022
Computer Equipment [Member]
Property Plant And Equipment [Line Items]
Useful lives of property and equipment	3 years
Laboratory Equipment [Member]
Property Plant And Equipment [Line Items]
Useful lives of property and equipment	5 years
Leasehold Improvements [Member]
Property Plant And Equipment [Line Items]
Useful lives of property and equipment	Shorter of remaining lease term or estimated useful life

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	Dec. 31, 2022	Dec. 31, 2021
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	$ 242,359	$ 242,084
Gross Unrealized Holding Gains	14
Gross Unrealized Holding Losses	(286)	(103)
Aggregate Fair Value	242,087	241,981
Level 1 [Member] | Money Market Funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	139,450	74,109
Aggregate Fair Value	139,450	74,109
Level 2 [Member] | Commercial Paper [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	42,467	85,352
Gross Unrealized Holding Losses	(82)	(27)
Aggregate Fair Value	42,385	85,325
Level 2 [Member] | Government Bonds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	24,804	33,809
Gross Unrealized Holding Losses	(204)	(52)
Aggregate Fair Value	24,600	33,757
Level 2 [Member] | Corporate Bonds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	35,638	48,814
Gross Unrealized Holding Gains	14
Gross Unrealized Holding Losses		(24)
Aggregate Fair Value	$ 35,652	$ 48,790

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Investment maturity period	2 years
Investment expected maturity period	12 months

Balance Sheet Components - Summ

Balance Sheet Components - Summary of Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Prepaid Expense and Other Assets, Current [Abstract]
Prepaid research and development costs	$ 3,805	$ 3,002
Prepaid insurance	755	1,282
Other prepaid expenses	678	231
Other current assets	203	463
Total prepaid expenses and other current assets	$ 5,441	$ 4,978

Balance Sheet Components - Su_2

Balance Sheet Components - Summary of Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Property Plant And Equipment [Line Items]
Total property and equipment, gross	$ 19,721	$ 18,637
Less: accumulated depreciation	(2,883)	(789)
Total property and equipment, net	16,838	17,848
Leasehold Improvements [Member]
Property Plant And Equipment [Line Items]
Total property and equipment, gross	17,231	16,594
Laboratory Equipment [Member]
Property Plant And Equipment [Line Items]
Total property and equipment, gross	1,764	1,353
Furniture and Fixtures [Member]
Property Plant And Equipment [Line Items]
Total property and equipment, gross	692	649
Computer Equipment and Software [Member]
Property Plant And Equipment [Line Items]
Total property and equipment, gross	$ 34	$ 41

Balance Sheet Components - Addi

Balance Sheet Components - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Prepaid Expense and Other Assets, Current [Abstract]
Depreciation expense	$ 2.1	$ 2.1

Balance Sheet Components - Su_3

Balance Sheet Components - Summary of Accrued Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Accrued Liabilities, Current [Abstract]
Accrued research and development expenses	$ 7,720	$ 2,404
Accrued compensation	5,299	3,573
Accrued professional services	394	1,274
Accrued construction costs		1,917
Other accrued expenses	35	82
Total accrued liabilities	$ 13,448	$ 9,250

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail)	1 Months Ended			12 Months Ended
	Nov. 30, 2021 USD ($)	Mar. 31, 2019 USD ($)	Nov. 30, 2011 USD ($)	Dec. 31, 2022 USD ($) Claim	Dec. 31, 2021 USD ($)
Gain Contingencies [Line Items]
Sublease Income				$ 1,600,000	$ 100,000
Aggregate sublease payment receivable	$ 3,400,000
Operating lease right-of-use assets				19,128,000	20,333,000
Lease liabilities				$ 32,858,000
Weighted average incremental borrowing rate				8.40%
Operating lease cost				$ 2,100,000	2,900,000
Variable lease payments				1,000,000	400,000
Income (loss)				(141,947,000)	(130,323,000)
Loss contingency accrual				$ 0
Indemnification Agreement [Member]
Gain Contingencies [Line Items]
Loss contingency pending claims | Claim				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
Operating lease, expiration month and year				2031-10
Operating lease, renewal term				10 years
Operating lease right-of-use assets				$ 19,100,000
Lease liabilities				$ 32,900,000
Weighted average remaining lease term				8 years 9 months 18 days

Commitments and Contingencies_2

Commitments and Contingencies - Future Minimum Lease Payments and Related Lease Liabilities (Detail) $ in Thousands	Dec. 31, 2022 USD ($)
Commitments and Contingencies Disclosure [Abstract]
2023	$ 4,198
2024	4,893
2025	5,065
2026	5,242
2027 and thereafter	28,025
Total undiscounted lease payments	47,423
Less: Imputed interest	(14,565)
Lease liabilities	$ 32,858

Stockholder's Equity - Addition

Stockholder's Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands			1 Months Ended		12 Months Ended
	Feb. 23, 2023	Jul. 11, 2022	Jul. 31, 2022	Aug. 31, 2021	Dec. 31, 2022	Dec. 31, 2021
Class Of Stock [Line Items]
Net proceeds from private placement		$ 122,500
Common stock, voting rights					The holders of the Company’s common stock have one vote for each share of common stock.
Common stock, dividends declared					$ 0
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.
Common stock, shares issued					47,722,995	38,560,854
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%
Common stock, shares issued					0
Sales Agreement with Cowen and Company LLC [Member] | 2021 ATM Program [Member] | Subsequent Event [Member]
Class Of Stock [Line Items]
Common stock, shares issued	2,646,458
Shares issued price per share	$ 6.80
Net proceeds from sale of common stock	$ 17,500

Stockholder's Equity - Schedule

Stockholder's Equity - Schedule of Common Stock Reserved for Future Issuance (Detail) - shares	Dec. 31, 2022	Dec. 31, 2021
Class Of Stock [Line Items]
Common stock reserved	8,152,093	5,662,824
Common stock reserved	478,109	2,039,951
Common stock reserved	50,174,938	13,748,479
Stock Options Issued and Outstanding [Member]
Class Of Stock [Line Items]
Common stock reserved	8,152,093	5,662,824
Stock Options Reserved for 2020 Incentive Award Plan [Member]
Class Of Stock [Line Items]
Common stock reserved	478,109	2,039,951
Unvested Restricted Stock Units Outstanding [Member]
Class Of Stock [Line Items]
Common stock reserved	550,236	50,000
Common Stock Reserved for Employee Stock Purchase Plan [Member]
Class Of Stock [Line Items]
Common stock reserved	994,257	729,775
Employment Inducement Award Plan [Member]
Class Of Stock [Line Items]
Common stock reserved	1,610,600
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

Equity Incentive Plan - Additio

Equity Incentive Plan - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Jul. 31, 2022
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 the 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	478,109	2,039,951
Intrinsic value of options exercised	$ 11,500	$ 6,400,000
Weighted- average exercise price per share, Stock options granted	$ 5.59
Unrecognized stock-based compensation cost expected period for recognition	2 years 4 months 24 days
Common stock for future issuance	50,174,938	13,748,479
Total stock-based compensation expense	$ 18,516,000	$ 16,262,000
Employees [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted- average exercise price per share, Stock options granted	$ 3.94	$ 18.83
2022 Employment Inducement Award Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options available for future grant	1,610,600		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%
Stock Options Issued and Outstanding [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized stock-based compensation cost	$ 37,400,000
Restricted Stock Units [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized stock-based compensation cost	$ 2,400,000
Unrecognized stock-based compensation cost expected period for recognition	2 years 3 months 18 days
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%
Share purchases funded through payroll deductions maximum percentage of employee's eligible compensation	15%
Common stock for future issuance	994,257	729,775
Percentage of shares of common stock outstanding on last day of immediately preceding fiscal year	1%
Total stock-based compensation expense	$ 100,000	$ 100,000

Equity Incentive Plan - Summary

Equity Incentive Plan - Summary of Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Share-Based Payment Arrangement [Abstract]
Number of shares, Beginning balance	5,662,824
Number of shares, Stock options granted	3,767,835
Number of shares, Stock options exercised	(15,364)
Number of shares, Stock options forfeited	(1,263,202)
Number of shares, Ending balance	8,152,093	5,662,824
Number of shares, Exercisable	3,406,230
Weighted- average exercise price per share, Beginning balance	$ 16.98
Weighted- average exercise price per share, Stock options granted	5.59
Weighted- average exercise price per share, Stock options exercised	5.28
Weighted- average exercise price per share, Stock options forfeited	15.78
Weighted- average exercise price per share, Ending balance	11.92	$ 16.98
Weighted- average exercise price per share, Exercisable	$ 12.87
Weighted- average remaining contractual term	8 years 1 month 2 days	8 years 3 months 3 days
Weighted- average remaining contractual term, Exercisable	6 years 11 months 8 days
Aggregate intrinsic value	$ 3,329	$ 10,186
Aggregate intrinsic value, Exercisable	$ 1,428

Equity Incentive Plan - Summa_2

Equity Incentive Plan - Summary of RSU Activity under Equity Incentive Plan (Detail)	12 Months Ended
	Dec. 31, 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	604,583
Number of Shares, Vested | shares	(11,817)
Number of Shares, Cancelled | shares	(92,530)
Number of Shares, Unvested as of December 31, 2022 | shares	550,236
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, Vested | $ / shares	12.84
Weighted-Average Grant Date Fair Value Per Share, Cancelled | $ / shares	7.37
Weighted-Average Grant Date Fair Value Per Share, Granted Unvested as of December 31, 2022 | $ / shares	$ 5.58

Equity Incentive Plan - Summa_3

Equity Incentive Plan - Summary of Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	$ 18,516	$ 16,262
Research and Development [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	8,874	8,610
General and Administrative [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	$ 9,642	$ 7,652

Equity Incentive Plan - Summa_4

Equity Incentive Plan - Summary of Fair Value of Each Stock Option Issued Estimated on the Date of Grant Using the Black-Scholes Option Pricing Model (Detail)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility, Minimum	78.80%	88.30%
Expected volatility, Maximum	85.90%	90.70%
Risk-free interest rate, Minimum	1.49%	0.35%
Risk-free interest rate, Maximum	4.19%	1.31%
Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	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

Income Taxes - Components of Lo

Income Taxes - Components of Loss Before Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Domestic	$ (141,939)	$ (130,313)
Foreign	(8)	(10)
Loss before income taxes	$ (141,947)	$ (130,323)

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Income Tax Computed at Federal Statutory Rates to Provision for Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Tax provision at U.S. statutory rate	$ (29,809)	$ (27,368)
Stock-based compensation	2,362	794
Research and development tax credits	(2,836)	(2,392)
Change in valuation allowance	30,148	25,911
Section 382 limitations		2,922
Other	$ 135	$ 133

Income Taxes - Deferred Tax Ass

Income Taxes - Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Net operating loss carryforwards	$ 63,551	$ 57,073
Research and development credits	11,095	7,367
Other intangibles	4	5
Accruals and reserves	974	686
Stock-based compensation	4,551	3,041
Capitalized research and development	19,744
Lease liabilities	6,946	7,340
Unrealized gain/loss on investments		240
Total gross deferred tax assets	106,865	75,752
Less: valuation allowance	(100,778)	(69,147)
Total deferred tax assets, net	6,087	6,605
Fixed assets	(2,043)	(2,290)
Right-of-use assets	(4,044)	(4,315)
Total gross deferred tax liabilities	$ (6,087)	$ (6,605)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Income Tax [Line Items]
Federal net operating loss carryforwards	$ 286,500,000
State net operating loss carryforwards	$ 71,100,000
Percentage of taxable income	80%
State carryforward losses expiration beginning year	2031
Increase in valuation allowance	$ 31,600,000	$ 24,400,000
Uncertain tax position	0
Unrecognized tax benefits, interest or penalty accruals	$ 0	0
Earliest Tax Year [Member]
Income Tax [Line Items]
Open tax year examination	2011
Latest Tax Year [Member]
Income Tax [Line Items]
Open tax year examination	2022
Federal [Member]
Income Tax [Line Items]
NOLs do not expire	$ 243,400,000	286,400,000
Tax credit carryforwards	$ 10,900,000
Federal carryforward losses expiration beginning year	2031
NOLs do not expire		100,000
Federal credits		3,700,000
State [Member]
Income Tax [Line Items]
NOLs do not expire		36,400,000
Tax credit carryforwards	$ 6,700,000
NOLs do not expire		$ 34,700,000

Income Taxes - Unrecognized Tax

Income Taxes - Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Beginning balance	$ 1,794	$ 1,576
Decreases based on tax positions related to prior year		(789)
Additions based on tax positions related to current year	932	1,007
Ending balance	$ 2,726	$ 1,794

Net Loss Per Share Attributab_3

Net Loss Per Share Attributable to Common Stockholders - Additional Information (Detail) - Pre-funded Warrants [Member]	Dec. 31, 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	12 Months Ended
	Dec. 31, 2022	Dec. 31, 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	17,176,134	5,728,748
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	46,297	15,924
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	8,152,093	5,662,824
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	550,236	50,000
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