Bolt Biotherapeutics (BOLT) 10-K 30 Mar 22 2021 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Mar. 24, 2022	Jun. 30, 2021
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Entity Registrant Name	Bolt Biotherapeutics, Inc.
Entity Central Index Key	0001641281
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		37,466,312
Entity Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
ICFR Auditor Attestation Flag	false
Entity Public Float			$ 382.6
Title of 12(b) Security	Common Stock, $0.00001 par value
Trading Symbol	BOLT
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity File Number	001-39988
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	47-2804636
Entity Address, Address Line One	900 Chesapeake
Entity Address, Address Line Two	Drive
Entity Address, City or Town	Redwood City
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94063
City Area Code	650
Local Phone Number	665-9295
Document Annual Report	true
Document Transition Report	false
Auditor Firm ID	238
Auditor Name	PricewaterhouseCoopers LLP
Auditor Location	San Jose, California

CONDENSED BALANCE SHEETS (Unaud

CONDENSED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 27,383	$ 5,542
Short-term investments	158,836	17,296
Prepaid expenses and other current assets	2,941	2,523
Total current assets	189,160	25,361
Property and equipment, net	6,158	4,083
Operating lease right-of-use assets	24,445	12,267
Restricted cash	1,565	1,565
Deferred offering costs		2,357
Long-term investments	85,348
Other assets	1,042	909
Total assets	307,718	46,542
Current liabilities:
Accounts payable	3,574	1,598
Accrued expenses and other current liabilities	12,384	6,663
Deferred revenue	2,869	1,502
Operating lease liabilities	2,501	1,501
Total current liabilities	21,328	11,264
Operating lease liabilities, net of current portion	21,854	9,376
Deferred revenue, non-current	14,207
Convertible preferred stock purchase right liability, non-current		25,224
Other long-term liabilities	210	329
Total liabilities	57,599	46,193
Commitments and contingencies (Note 7)
Convertible preferred stock, $0.00001 par value, authorized shares-zero shares and 20,843,367 shares authorized at December 31, 2021 and 2020, respectively; zero shares and 15,232,275 shares issued and outstanding at December 31, 2021 and 2020, respectively. Liquidation preference of zero and $121,728 at December 31, 2021 and 2020, respectively		105,296
Stockholders' equity (deficit):
Preferred stock, $0.00001 par value, authorized shares-10,000,000 shares and zero shares authorized at December 31, 2021 and 2020, respectively; zero shares issued and outstanding at December 31, 2021 and 2020
Additional paid-in capital	457,430	3,452
Accumulated other comprehensive loss	(321)
Accumulated deficit	(206,990)	(108,399)
Total stockholders' equity (deficit):	250,119	(104,947)
Total liabilities, convertible preferred stock, and stockholders' equity (deficit)	$ 307,718	$ 46,542

CONDENSED BALANCE SHEETS (Una_2

CONDENSED BALANCE SHEETS (Unaudited) (Parenthetical) - USD ($)	Dec. 31, 2021	Dec. 31, 2020
Statement Of Financial Position [Abstract]
Convertible preferred stock, par value per share	$ 0.00001	$ 0.00001
Convertible preferred stock, shares authorized	0	20,843,367
Convertible preferred stock, shares issued	0	15,232,275
Convertible preferred stock, shares outstanding	0	15,232,275
Convertible preferred stock, liquidation preference	$ 0	$ 121,728,000
Preferred stock, par value	$ 0.00001	$ 0.00001
Preferred stock, shares authorized	10,000,000	0
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value per share	$ 0.00001	$ 0.00001
Common stock, shares authorized	200,000,000	198,000,000
Common stock, shares, issued	37,399,694	2,130,139
Common stock, shares, outstanding	37,399,694	2,130,139

CONDENSED STATEMENTS OF OPERATI

CONDENSED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Unaudited) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Income Statement [Abstract]
Collaboration revenue	$ 1,260	$ 231
Operating expenses:
Research and development	75,655	40,357
General and administrative	18,393	9,056
Total operating expense	94,048	49,413
Loss from operations	(92,788)	(49,182)
Other income (expense), net
Interest income	281	199
Change in fair value of convertible preferred stock purchase right liability	(6,084)	(11,745)
Total other expense, net	(5,803)	(11,546)
Net loss	(98,591)	(60,728)
Net unrealized loss on marketable securities	(321)
Comprehensive loss	$ (98,912)	$ (60,728)
Net loss per share, basic and diluted	$ (2.97)	$ (28.89)
Weighted-average shares outstanding, basic and diluted	33,196,712	2,102,328

STATEMENTS OF CONVERTIBLE PREFE

STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) $ in Thousands	Total	Convertible Preferred Stock	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit
Beginning Balance at Dec. 31, 2019	$ (45,846)			$ 1,825		$ (47,671)
Beginning Balance, Shares at Dec. 31, 2019			1,921,642
Beginning Balance at Dec. 31, 2019		$ 77,505
Beginning Balance, Shares at Dec. 31, 2019		10,070,102
Issuance of Series C-1 convertible preferred stock, net of issuance costs of $285 and convertible preferred stock purchase right liability of $13,479		$ 27,791
Issuance of Series C-1 convertible preferred stock, net of issuance costs of $285 and convertible preferred stock purchase right liability of $13,479, Shares		5,162,173
Issuance of common stock upon exercise of stock options	158			158
Issuance of common stock upon exercise of stock options, Shares			119,077
Issuance of common stock upon exercise of warrants	6			6
Issuance of common stock upon exercise of warrants, Shares			89,420
Vesting of early exercised options and restricted stock awards	43			43
Stock-based compensation	1,420			1,420
Net loss	(60,728)					(60,728)
Ending Balance at Dec. 31, 2020	$ 105,296	$ 105,296
Ending Balance, Shares at Dec. 31, 2020	15,232,275	15,232,275
Ending Balance at Dec. 31, 2020	$ (104,947)			3,452		(108,399)
Ending Balance, Shares at Dec. 31, 2020			2,130,139
Issuance of Series C-2 convertible preferred stock, net of issuance cost of $42		$ 51,902
Issuance of Series C-2 convertible preferred stock, net of issuance cost of $42, Shares		5,611,059
Reclassification of convertible preferred stock purchase right liability to equity upon issuance of convertible C-2 preferred stock		$ 31,308
Conversion of convertible preferred stock to common stock	188,506			188,506
Conversion of convertible preferred stock to common stock, Shares			20,843,334
Temporary equity, Conversion of convertible preferred stock to common stock		$ (188,506)
Temporary equity, Conversion of convertible preferred stock to common stock, Shares		(20,843,334)
Issuance of common stock upon initial public offering, net of issuance costs of $22,541	241,959			241,959
Issuance of common stock upon initial public offering, net of issuance costs of $22,541, Shares			13,225,000
Issuance of common stock upon exercise of stock options	$ 612			612
Issuance of common stock upon exercise of stock options, Shares	214,438		172,006
Issuance of common stock upon exercise of warrants, Shares			82,603
Issuance of common stock related to stock purchase agreement	$ 13,638			13,638
Issuance of common stock related to stock purchase agreement, Shares			821,045
Issuance of common stock under employee stock purchase plan	640			640
Issuance of common stock under employee stock purchase plan, Shares			125,567
Vesting of early exercised options	123			123
Stock-based compensation	8,500			8,500
Unrealized loss on available-for-sale investments	(321)				$ (321)
Net loss	$ (98,591)					(98,591)
Ending Balance, Shares at Dec. 31, 2021	0
Ending Balance at Dec. 31, 2021	$ 250,119			$ 457,430	$ (321)	$ (206,990)
Ending Balance, Shares at Dec. 31, 2021			37,399,694

STATEMENTS OF CONVERTIBLE PRE_2

STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Common Stock
Stock issuance cost	$ 22,541
Convertible Preferred Stock
Stock issuance cost	$ 42
Purchase right liability		$ 13,479
Series C-1 Convertible Preferred Stock
Stock issuance cost		$ 285

CONDENSED STATEMENTS OF CASH FL

CONDENSED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (98,591)	$ (60,728)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,193	611
Stock-based compensation expense	8,500	1,420
Accretion of premium/discount on marketable securities	2,975	34
Unrealized gain (loss) on marketable securities, net	(321)
Loss on disposal of property and equipment	108
Change in fair value of convertible preferred stock purchase right liability	6,084	11,745
Non-cash lease expense	2,479	1,893
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(568)	(1,878)
Accounts payable and accrued expenses	6,676	2,882
Operating lease liabilities	(1,179)	(3,389)
Deferred revenue	15,574	(69)
Other long-term liabilities	4	171
Net cash used in operating activities	(57,066)	(47,308)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of property and equipment	(2,338)	(3,262)
Purchases of marketable securities	(313,375)	(33,229)
Maturities of marketable securities	83,512	15,899
Net cash used in investing activities	(232,201)	(20,592)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of preferred stock, net	51,902	41,270
Proceeds from initial public offering, net of issuance cost	244,316
Proceeds from issuance of common stock related to stock purchase agreement	13,638
Proceeds from issuance of common stock	1,252	294
Payment of deferred offering costs		(1,967)
Net cash provided by financing activities	311,108	39,597
Net increase (decrease) in cash	21,841	(28,303)
Cash, cash equivalents and restricted cash at beginning of year	7,107	35,410
Cash, cash equivalents and restricted cash at end of period	28,948	7,107
Reconciliation of cash, cash equivalents and restricted cash:
Cash and cash equivalents	27,383	5,542
Restricted cash	1,565	1,565
Total cash, cash equivalents and restricted cash	28,948	7,107
Supplemental schedule of non-cash investing and financing activities:
Vesting of unvested issued common stock	123	49
Purchases of property and equipment included in accounts payable and accrued liabilities	1,021	28
Deferred offering costs in accounts payable and accrued liabilities		390
Right of use assets obtained in exchange for operating lease obligations	$ 14,657	$ 4,081

Description of the Business

Description of the Business	12 Months Ended
	Dec. 31, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Description of the Business	1. Description of the Business Bolt Biotherapeutics, Inc. (the “Company”) is pioneering a new class of immuno-oncology agents that combine the targeting precision of antibodies with the power of both the innate and adaptive immune systems. Initial Public Offering and Related Transactions On February 9, 2021, the Company completed its initial public offering (“IPO”) pursuant to a registration statement on Form S-1 (File No. 333-252136) that was declared effective by the Securities and Exchange Commission (the “SEC”) on February 4, 2021 and sold an aggregate of 13,225,000 shares of its common stock, including the full exercise of the underwriters’ option to purchase 1,725,000 shares, at a price per share of $ 20.00 . Proceeds from the IPO, net of underwriting discounts, commissions and offering costs, were approximately $ 242.0 million. In addition, each of the following occurred on February 4, 2021, in connection with the completion of the Company’s IPO: • the conversion of all outstanding shares of convertible preferred stock into 20,843,334 shares of the Company’s common stock; and • the amendment and restatement of the Company’s certificate of incorporation, authorizing 200,000,000 shares of common stock and 10,000,000 shares of undesignated preferred stock. Basis of Presentation The Company’s financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”). Certain reclassifications on the balance sheet have been made to prior period amounts to conform to current period presentation. Risks and Uncertainties The Company is subject to a number of risks similar to other early-stage biopharmaceutical companies, including, but not limited to, changes in any of the following areas that the Company believes could have a material adverse effect on its future financial position or results of operations: risks related to the successful discovery and development of its product candidates, ability to raise additional capital, development of new technological innovations by its competitors and delay or inability to obtain chemical or biological intermediates from such suppliers required for the synthesis of the Company’s product candidates, including due to the impact of the current COVID-19 pandemic, protection of intellectual property rights, litigation or claims against the Company based on intellectual property rights, regulatory clearance and market acceptance of the Company’s products. The current COVID-19 pandemic, which is impacting worldwide economic activity, poses the risk that the Company or its employees, contractors, suppliers, and other partners may be prevented from conducting business activities for an indefinite period, including due to shutdowns that may be requested or mandated by governmental authorities. The extent to which the COVID-19 pandemic will impact the Company’s business will depend on future developments that are highly uncertain and cannot be predicted at this time. The preparation of financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. The extent to which the COVID-19 pandemic may directly or indirectly impact the Company’s financial statements is highly uncertain and subject to change. Management considered the potential impact of the COVID-19 pandemic on its estimates and assumptions and there was not a material impact to the Company’s financial statements as of and for year ended December 31, 2021; however, actual results could differ from those estimates and there may be changes to management’s estimates in future periods. The Company relies on single source manufacturers and suppliers for the supply of its product candidates. Disruption from these manufacturers or suppliers would have a negative impact on the Company’s business, financial position, and results of operations.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, and the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting period. On an ongoing basis, the Company evaluates its estimates and assumptions, including those related to revenue recognition, stock-based compensation and accrued liabilities. Management bases its estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Actual results may differ materially from those estimates. Deferred Offering Costs The Company capitalizes certain legal, accounting, and other third-party fees that are directly related to the Company’s in-process equity financings, including the IPO, until such financings are consummated. After consummation of the equity financing, these costs are recorded as a reduction of the proceeds received as a result of the offering. Should a planned equity financing be abandoned, terminated, or significantly delayed, the deferred offering costs are immediately written off to operating expenses. There were no deferred offering costs capitalized as of December 31, 2021. At December 31, 2020, deferred offering costs totaling $ 2.4 million are included as non-current assets in the accompanying balance sheet. Concentrations of Credit Risk Financial instruments that potentially subject the Company to concentration of credit risk consist of cash, cash equivalents and marketable securities. At December 31, 2021 and 2020 , most of the Company’s funds are invested with a registered investment manager and custodied at one financial institution, with working capital kept at a separate financial institution, and account balances may at times exceed federally insured limits. Management believes that the Company is not exposed to significant credit risk due to the financial strength of the depository institutions where the funds are held. Cash and Cash Equivalents The Company considers all highly liquid investments purchased with an original maturity of three months or less to be cash equivalents. As of December 31, 2021 and 2020 , cash and cash equivalents consisted primarily of bank deposits and money market funds which were unrestricted as to withdrawal or use. Marketable Securities The Company classifies its marketable securities as available-for-sale and records such assets at estimated fair value in the balance sheets, with unrealized gains and losses that are determined to be temporary, if any, reported as a component of other comprehensive income (loss) within the statements of operations and comprehensive loss and as a separate component of stockholders’ equity (deficit). The Company classifies marketable securities with remaining maturities greater than three months but less than one year as short-term investments, and those with remaining maturities greater than one year are classified as long-term investments. Investments are regularly reviewed for other-than-temporary declines in fair value. The review includes the consideration of the cause of the impairment, including the creditworthiness of the security issuers, the number of investments in an unrealized loss position, the severity and duration of the unrealized losses and whether it is more likely than not that the Company will be required to sell the investments before the recovery of their amortized cost basis. A decline in the fair value of any security below cost that is deemed other than temporary results in a charge to earnings and the establishment of a new cost basis for the security. The Company invests its excess cash balances primarily in corporate debt securities with strong credit ratings. Realized gains and losses are calculated on the specific identification method and recorded as interest income and were immaterial for all periods presented. Restricted Cash As of December 31, 2021 and 2020 , the Company had $ 1.6 million of long-term restricted cash deposited with a financial institution. The restricted cash is held in separate bank accounts to support letter of credit agreements related to the Company’s facility leases which expire in 2025 and 2031 (see Note 7). Property and Equipment Property and equipment are stated at cost, net of accumulated depreciation and amortization. Depreciation and amortization begin at the time the asset is placed in service. Depreciation and amortization are computed using the straight-line method over the estimated useful lives of the assets of five years . Leasehold improvements are amortized over the shorter of the lease term or the estimated useful lives of the assets. Maintenance and repairs are expensed as incurred. Upon sale or retirement of assets, the cost and accumulated depreciation and amortization are removed from the balance sheet and any resulting gain or loss is reflected in the statement of operations and comprehensive loss in the period realized. Impairment of Long-Lived Assets The Company reviews long-lived assets, primarily comprised of property and equipment, for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability is measured by comparison of the carrying amount to the estimated undiscounted future cash flows, which the assets or asset groups are expected to generate. If such assets are considered to be impaired, the impairment to be recognized at the amount by which the carrying amount of the assets or asset groups exceeds the estimated fair value of the assets or asset groups. There have been no such impairments of long-lived assets during the periods presented. Revenue Recognition Under Accounting Standard Codification Topic 606, Revenue from Contract with Customers (“ASC 606”), the Company recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration which the Company expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that the Company determines are within the scope of ASC 606, the following steps are performed: (i) identification of a contract to provide goods or services to a customer; (ii) determination of whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration, if any; (iv) where a contract contains multiple performance obligations, the Company must allocate the transaction price to the performance obligations based on estimated selling prices; and (v) recognition of revenue when (or as) each performance obligation is satisfied. The Company only applies the five-step model to contracts when it is probable that the Company will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. At contract inception, once the contract is determined to be within the scope of ASC 606, the Company assesses the goods or services promised within each contract and determines those that are performance obligations and assesses whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied. As part of the accounting for these arrangements, the Company develops assumptions that require judgment to determine the stand-alone selling price for each performance obligation identified in the contract. The Company uses key assumptions to determine the stand-alone selling price, which may include development timelines, reimbursement rates for personnel costs, discount rates, and probabilities of technical and regulatory success. The Company evaluates each performance obligation and determines if it is satisfied over time. In addition, variable consideration must be evaluated to determine if it is constrained and, therefore, excluded from the transaction price. If the license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes revenues allocated to the license when the license is transferred to the customer and the customer is able to use and benefit from the license. For licenses that are bundled with other promised goods or services, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. Any change made to estimated progress towards completion of a performance obligation due to changes in the estimated activities required to complete the performance obligation and, therefore, revenue recognized will be recorded as a change in estimate. The Company receives payments from its collaborators based on billing schedules established in each contract. Upfront payments and other payments may require deferral of revenue recognition to a future period until the Company performs its obligation under its collaboration arrangements. Amounts are recorded as accounts receivable when the Company’s right to consideration is unconditional. The Company does not assess whether a contract has a significant financing component if the expectation at contract inception is such that the payment by the customer is akin to a deposit for research and development services. To date, all of the Company’s revenue has been derived from its development agreement with Toray Industries, Inc. (“Toray”) and Genmab A/S (“Genmab”), as described in Note 6. Research and Development Expenses Research and development costs are charged to expense as incurred. Research and development expenses include certain payroll and personnel expenses, laboratory supplies, consulting costs, external contract research and development expenses, and allocated overhead, including rent, equipment depreciation and utilities. Advance payments for goods or services for future research and development activities are deferred and expensed as the goods are delivered or 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 trials on the Company’s behalf. In accruing service fees, the Company estimates the time period over which services will be performed and the level of effort to be expended in each period. These estimates are based on communications with the third-party service providers and the Company’s estimates of accrued expenses and on information available at each balance sheet date. If the actual timing of the performance of services or the level of effort varies from the estimate, the Company will adjust the accrual accordingly. Fair Value Measurements Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. Cash and cash equivalents, restricted cash, marketable debt securities, accounts payable, accrued expenses and other current liabilities are reported at their respective fair values in our balance sheets. The carrying amount of the remaining financial instruments approximate fair value due to their short-term nature. Refer to Note 3 for the methodologies and assumptions used in valuing financial instruments. Leases The Company determines whether an arrangement is a lease at inception. Specifically, it considers whether it controls the underlying asset and has the right to obtain substantially all the economic benefits or outputs from the asset. If the contractual arrangement contains a lease, the Company then determines the classification of the lease, operating or finance, using the classification criteria described in Accounting Standard Codification Topic 842, Leases (“ASC 842”). The Company has elected not to separate lease components from non-lease components, such as common area maintenance charges, and instead accounts for the lease and non-lease components as a single component. At the commencement date of a lease, the Company recognizes lease liabilities which represent its obligation to make lease payments, and right-of-use assets (“ROU assets”) which represent its right to use the underlying asset during the lease term. The lease liability is measured at the present value of lease payments over the lease term. As the Company’s leases typically do not provide an implicit rate, the Company uses an incremental borrowing rate based on the information available at the lease commencement date. The ROU asset is measured at cost, which includes the initial measurement of the lease liability and initial direct costs incurred by the Company and excludes lease incentives. ROU assets are recorded in operating lease ROU assets and lease liabilities are recorded in operating lease liabilities, current and noncurrent in the balance sheets. Lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Operating lease expense is recognized on a straight-line basis over the lease term. The Company does not recognize lease liabilities and ROU assets for short-term leases with terms of twelve months or less. Stock-Based Compensation Expense The Company accounts for stock-based compensation by measuring and recognizing compensation expense for all share-based payments made to employees and non-employees based on estimated grant-date fair values. For stock-based payments with service conditions only, the Company uses the straight-line method to allocate compensation cost to reporting periods over each award’s requisite service period, which is generally the vesting period. For stock-based payments with both performance and service conditions, the Company recognizes expense based on the fair value of the performance awards over the estimated service period (under the graded vesting method) to the extent the achievement of the related performance criteria is estimated to be probable. The grant date fair value is utilized for restricted stock awards and the fair value of each stock option grant is estimated on the date of grant using the Black-Scholes model. The Black-Scholes model requires the input of subjective assumptions, including expected volatility, expected dividend yield, expected term, risk-free interest rate, and the estimated fair value of the underlying common stock on the date of grant. The Company accounts for forfeitures as they occur. Income Taxes The Company accounts for income taxes using the asset and liability method. Under this method, deferred tax assets and liabilities are determined based on differences between financial reporting and tax reporting bases of assets and liabilities and are measured using enacted tax rates and laws that are expected to be in effect when the differences are expected to reverse. Changes in deferred tax assets and liabilities are recorded in the provision for income taxes. Realization of deferred tax assets is dependent upon future earnings, the timing and amount of which are uncertain. A valuation allowance is provided against deferred tax assets unless it is more likely than not that they will be realized. The Company utilizes a two-step approach to recognize and measure uncertain tax positions. The first step is to evaluate the tax position for recognition by determining if the weight of available evidence indicates that it is more likely than not that the position will be sustained upon tax authority examination, including resolution of related appeals or litigation processes, if any. The second step is to measure the tax benefit as the largest amount that is more than 50% likely of being realized upon 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. Net Loss Per Share Basic net loss per share is calculated by dividing the net loss by the weighted-average number of shares of common stock outstanding during the period, without consideration for potentially dilutive securities. Diluted net loss per share is computed by dividing the net loss by the weighted-average number of common stock and potentially dilutive securities outstanding for the period. For purposes of the diluted net loss per share calculation, convertible preferred stock, stock options, common stock subject to repurchase related to unvested restricted stock awards and early exercise of stock options are considered potentially dilutive securities. Basic and diluted net loss per share is presented in conformity with the two-class method required for participating securities as the convertible preferred stock is considered a participating security because it participates in dividends with common stock. The Company also considers the shares issued upon the early exercise of stock options subject to repurchase to be participating securities because holders of such shares have non-forfeitable dividend rights in the event a dividend is paid on common stock. The holders of all series of convertible preferred stock and the holders of early exercised shares subject to repurchase do not have a contractual obligation to share in the Company’s losses. As such, the net loss was attributed entirely to common stockholders. Because the Company has reported a net loss for all periods presented, diluted net loss per share is the same as basic net loss per share for all periods presented as potentially dilutive securities were anti-dilutive. Comprehensive Loss Comprehensive loss includes all changes in equity (net assets) during a period from non-owner sources, including unrealized gains and losses on marketable securities. The Company incurred net unrealized loss on marketable securities of $ 0.3 million during the year ended December 31, 2021. During the year ended December 31, 2020 , the items qualifying as other comprehensive loss was not significant, and, therefore, the Company’s comprehensive loss was the same as its reported net loss for the period. Segment Reporting The Company has one operating segment. Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. Recent Accounting Standards From time to time, new accounting standards are issued by the Financial Accounting Standards Board (the “FASB”), or other standard setting bodies and adopted by the Company as of the specified effective date. Unless otherwise discussed, the impact of recently issued standards that are not yet effective will not have a material impact on the Company’s financial position or results of operations upon adoption. Recently Adopted Accounting Pronouncements In November 2018, the Financial Accounting Standards Board (“FASB”) issued Accounting Standard Update (“ASU”) No. 2018-18 , Collaborative Arrangements (Topic 808): Clarifying the Interaction Between Topic 808 and Topic 606 . This ASU clarifies that certain transactions between participants in a collaborative arrangement should be accounted for under ASC 606, Revenue from Contracts with Customers, when the counterparty is a customer. This ASU also precludes an entity from presenting consideration received from a transaction as revenue from contracts with customers if the counterparty is not a customer for that transaction. This ASU is effective for fiscal years beginning after December 15, 2020, and interim periods within fiscal years beginning after December 15, 2021. Early adoption is permitted for entities that have adopted ASC 606, Revenue from Contracts with Customers. The Company adopted this ASU on January 1, 2021 . The adoption of this ASU did no t result in a material impact on the Company’s financial statements and related disclosures.

Fair Value Measurements and Fai

Fair Value Measurements and Fair Value of Financial Instruments	12 Months Ended
	Dec. 31, 2021
Fair Value Disclosures [Abstract]
Fair Value Measurements and Fair Value of Financial Instruments	3. Fair Value Measurements and Fair Value of Financial Instruments The authoritative guidance on fair value measurements establishes a three-tier fair value hierarchy for disclosure of fair value measurements as follows: Level 1 —Quoted prices in active markets for identical assets or liabilities. Level 2 —Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3 —Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. Assets and liabilities measured at fair value are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. The Company’s assessment of the significance of a particular input to the fair value measurement in its entirety requires management to make judgments and consider factors specific to the asset or liability. During the years ended December 31, 2021 and 2020, financial assets measured on a recurring basis consist of cash invested in money market accounts, short-term investments, and long-term investments. The fair value of short-term and long-term investments is based upon market prices quoted on the last day of the fiscal period or other observable market inputs. The Company obtains pricing information from its investment manager and generally determines the fair value of investment securities using standard observable inputs, including reported trades, broker/dealer quotes, bids and/or offers. Financial liabilities measured at fair value on a recurring basis include the convertible preferred stock purchase right liability described below. There were no transfers within the hierarchy during the years ended December 31, 2 0 21 and 2 0 2 0 . Marketable securities, all of which are classified as available-for-sale securities, consisted of the following at December 31, 2021 and 2020 (in thousands): December 31, 2021 Amortized Unrealized Unrealized Estimated Cost Gains Losses Fair Value Asset backed securities $ 34,058 $ — $ ( 18 ) $ 34,040 U.S. treasury securities 39,985 — ( 171 ) 39,814 Other government agency securities 5,068 ( 22 ) 5,046 Commercial paper 64,956 — — 64,956 Corporate debt securities 100,438 12 ( 122 ) 100,328 Total $ 244,505 $ 12 $ ( 333 ) $ 244,184 December 31, 2020 Amortized Unrealized Unrealized Estimated Cost Gains Losses Fair Value Asset backed securities $ 2,639 $ — $ — $ 2,639 U.S. treasury securities 1,300 — — 1,300 Commercial paper 6,795 — — 6,795 Corporate debt securities 6,562 1 ( 1 ) 6,562 Total $ 17,296 $ 1 $ ( 1 ) $ 17,296 At December 31, 2021 and 2020, the fair values of the Company’s assets and liabilities, which are measured at fair value on a recurring basis, were determined using the following inputs (in thousands): Fair Value Measurements at Reporting Date Using December 31, 2021 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Money market funds $ 22,917 $ 22,917 $ — $ — Asset backed securities 34,040 — 34,040 — U.S. treasury securities 39,814 39,814 — — Other government agency securities 5,046 — 5,046 Commercial paper 64,956 — 64,956 — Corporate debt securities 100,328 — 100,328 — Total $ 267,101 $ 62,731 $ 204,370 $ — Fair Value Measurements at Reporting Date Using December 31, 2020 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Money market funds $ 3,921 $ 3,921 $ — $ — Asset backed securities 2,640 — 2,640 — U.S. treasury securities 1,300 1,300 — — Commercial paper 6,795 — 6,795 — Corporate debt securities 6,561 — 6,561 — Total $ 21,217 $ 5,221 $ 15,996 $ — Liabilities: Preferred stock purchase right liability $ 25,224 $ — $ — $ 25,224 Level 3 liability that was measured at fair value on a recurring basis consist of the convertible preferred stock purchase right liability. The following table provides a summary of changes in the estimated fair value of the financial instruments using significant Level 3 inputs (in thousands): Series C Convertible Preferred Stock Purchase Right Liability Balance at December 31, 2020 $ 25,224 Change in fair value 6,084 Reclassification to equity ( 31,308 ) Balance at December 31, 2021 $ — The fair value of the convertible preferred stock purchase right liability was estimated using an income-based approach incorporating probability considerations for different scenarios. The main assumptions included the probability and timing of the tranche closing, and the estimated value of the Company’s equity at that time. In January 2021, the Company issued the additional shares of convertible preferred stock and accordingly, this contractual obligation was settled, and the convertible preferred stock purchase right liability was remeasured to its fair value and reclassified to permanent equity. The fair value of the convertible preferred stock purchase right liability immediately prior to settlement was increased to $ 31.3 million as a result of the estimated probability of the occurrence of the second closing of Series C convertible preferred stock increasing to 80 %, timing related to the occurrence of the second closing decreasing to 0.06 years and the increase in the future expected value of the Series C preferred shares to $ 16.25 per share.

License and Equity Agreement

License and Equity Agreement	12 Months Ended
	Dec. 31, 2021
License And Equity Agreement [Abstract]
License and Equity Agreement	4. License and Equity Agreement License and Equity Agreement with Related Party In May 2015 and June 2018, the Company entered into license agreements (the “Stanford Agreement”), as amended, with The Board of Trustees of the Leland Stanford Junior University (“Stanford”). The Stanford Agreement provides the Company exclusive licenses to certain inventions. As consideration, the Company issued Stanford shares of its common stock and a limited right to purchase equity in future financing. Dr. Edgar G. Engleman, a founder and member of the board of directors of the Company, who is a professor at Stanford, was issued shares of common stock as part of the Company’s Series A financing in September 2016. During the years ended December 31, 2021 and 2020, the Company paid Stanford $ 40,000 and $ 50,000 , respectively, in license and milestone fees under the Stanford Agreements. In addition, the Company paid Stanford $ 80,800 and $ 0.1 million during the years ended December 31, 2021 and 2020, respectively, for reimbursement of patent maintenance costs which are included as part of general and administrative expense. Additionally, the Company is required by the Stanford Agreement to make milestone payments up to an aggregate of $ 0.4 million for the first licensed product that meets certain patent issuance, clinical and regulatory milestones, and an additional milestone payment of $ 0.2 million for each additional regulatory approval. The Company also agreed in the Stanford Agreement to pay Stanford tiered royalties on the Company’s and its sublicensees’ net sales of licensed products, if any, at low single-digit percentage rates, subject to certain reductions. Dr. Engleman is entitled to receive a share of any royalties that the Company pays to Stanford under the Stanford Agreement with respect to the covered intellectual property. No royalty payments have been made to date.

Balance Sheet Components

Balance Sheet Components	12 Months Ended
	Dec. 31, 2021
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Components	5. Balance Sheet Components Property and Equipment, net Property and equipment, net, consist of the following (in thousands): December 31, 2021 2020 Laboratory equipment $ 7,889 $ 5,253 Office equipment 369 69 Leasehold improvements 145 — Total property and equipment 8,403 5,322 Less accumulated depreciation and amortization ( 2,245 ) ( 1,239 ) Total $ 6,158 $ 4,083 Depreciation expense related to property and equipment was $ 1.2 million and $ 0.6 million for the years ended December 31, 2021 and 2020, respectively. Accrued Expenses and Other Current Liabilities Accrued expenses and other current liabilities consist of the following (in thousands): December 31, 2021 2020 Accrued research and development $ 6,300 $ 3,199 Accrued compensation 4,886 2,885 Accrued other 1,198 579 Total $ 12,384 $ 6,663

Collaborations

Collaborations	12 Months Ended
	Dec. 31, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Collaborations	6. Collaborations Joint Development and License Agreement with Toray Industries, Inc. In March 2019, the Company entered into a Joint Development and License Agreement (the “Toray Agreement”) with Toray Industries, Inc. (“Toray”) to jointly develop and commercialize a Boltbody immune-stimulating antibody conjugate (“ISAC”) containing Toray’s proprietary antibody to treat cancer. The Company determined that the Toray Agreement is a contract with a customer and should be accounted for under ASC 606. In conjunction with the Toray Agreement, the Company entered into a Series T Convertible Preferred Stock Purchase Agreement (the “Series T Agreement”) for the issuance of 717,514 shares of Series T convertible preferred stock to Toray. These contracts have been evaluated together and the consideration in excess of the fair value of the Series T convertible preferred stock of $ 1.5 million has been allocated to the Toray Agreement and included in the total consideration for collaboration revenue. In February 2021, in connection with the Company’s IPO, all outstanding shares of Series T convertible preferred stock were converted into shares of the Company’s common stock. In the Toray Agreement, the Company has identified one bundled performance obligation which includes the license rights, research and development services and services associated with participation on a joint steering committee. Collaboration revenue is recognized over time proportionate to the costs that the Company has incurred to perform the services using an input method as a measure of progress towards satisfying the performance obligation, which is based on project hours. Amounts are billed based on estimated variable consideration in the quarter ahead of performance and are trued up on the subsequent quarter’s invoice following the work performed. The cumulative effect of revisions to estimated hours to complete the Company’s performance obligation will be recorded in the period in which changes are identified and amounts can be reasonably estimated. Deferred revenue allocated to the unsatisfied performance obligation is recorded as a contract liability on the balance sheet and will be recognized over time as the services are performed. As of December 31, 2021 , contract liability totaling $ 1.5 million had been reclassified from current to long-term liabilities due to the ongoing reevaluation of the research plan by both parties and the related joint meeting in the fourth quarter of 2021. The outcome of this reevaluation may impact the scope and timing of such services. The following table presents changes in the Company’s contract liability (in thousands): Balance at December 31, 2019 $ 1,571 Addition—amount billed for research and development services 162 Revenue recognized in 2020 ( 231 ) Balance at December 31, 2020 and 2021 $ 1,502 The Toray Agreement includes both fixed and variable consideration. Under the Toray Agreement, the Company will be compensated for early-stage development and manufacturing activities based on agreed full-time equivalent rates and actual out of pocket costs incurred through the completion of the first Phase 1 clinical trial for the lead product candidate and Toray is entitled to reimbursement for 50% of such development costs from the Company’s share of revenues collected from the sale or licensing of collaboration products. Although the legal term of the agreement is until collaboration products are no longer sold in the territories covered under the agreement, the parties have present enforceable rights and obligations through the end of the first Phase 1 clinical trial, after which both parties can opt out of continued development under the agreement. As such, the accounting term of the Toray Agreement was considered to terminate upon completion of the first Phase 1 clinical trial. After the conclusion of the first Phase 1 clinical trial, the parties will share equally all costs of development activities necessary for obtaining regulatory approval of collaboration products in the indications in the territories covered under the agreement, unless either party elects to opt out of its co-funding obligations or reduce them by half, which election can be on a region-by-region basis or for the territories covered under the agreement as a whole. Such optional additional items which will be accounted for as contract modifications when development advances past certain milestones and the parties both exercise their opt-in rights. Oncology Research and Development Collaboration with Genmab A/S In May 2021, the Company entered into a License and Collaboration Agreement (the “Genmab Agreement”) with Genmab A/S (“Genmab”). Together, the companies will evaluate Genmab antibodies and bispecific antibody engineering technologies in combination with the Company’s ISAC technology platform, with the goal of discovering and developing next-generation bispecific ISACs for the treatment of cancer. Under this research collaboration, the companies will evaluate multiple bispecific ISAC concepts to identify up to three clinical candidates for development. Genmab will fund the research, along with the preclinical and clinical development of these candidates through initial clinical proof of concept. Under the Genmab Agreement, the Company received an upfront payment of $ 10.0 million. The Company determined that the Genmab Agreement is a contract with a customer and should be accounted for under ASC 606. In conjunction with the Genmab Agreement, the Company entered into a stock purchase agreement (the “Genmab SPA”) for the issuance of 821,045 shares of the Company’s common stock to Genmab for a total purchase price of $ 15.0 million. These contracts have been evaluated together and the consideration in excess of the fair value of the common stock of $ 1.4 million has been allocated to the Genmab Agreement and included in the total consideration for collaboration revenue. In the Genmab Agreement, the Company has identified one bundled performance obligation that includes the license rights, research and development services and services associated with participation on a joint research committee. The transaction price includes the $ 10.0 million upfront payment, the $ 1.4 million allocated from the Genmab SPA, and $ 6.3 million of estimated variable consideration related to compensation for research and development services at the agreed upon full-time employee rate and third-party costs. Collaboration revenue is recognized over time proportionate to the costs that the Company has incurred to perform the services using an input method as a measure of progress towards satisfying the performance obligation, which is based on project hours. Compensation for the research and development services are billed in the quarter based on actual hours incurred to satisfy the performance obligation. The cumulative effect of revisions to estimated hours to complete the Company’s performance obligation will be recorded in the period in which changes are identified and amounts can be reasonably estimated. As of December 31, 2021 , receivables of $ 0.2 million related to research and development services performed under the Genmab Agreement were recorded as part of the prepaid expenses and other current assets line item on the balance sheet. Deferred revenue allocated to the unsatisfied performance obligation is recorded as a contract liability on the balance sheet and will be recognized over time as the services are performed. As of December 31, 2021 , contract liabilities totaling $ 10.6 million were recorded in deferred revenue with $ 2.2 million in current liabilities and $ 8.4 million in non-current liabilities on the balance sheet based on the forecasted periods of performance. The following table presents changes in the Company’s contract liability (in thousands): Balance at December 31, 2020 $ — Addition—fixed consideration 11,362 Addition—amount billed for research and development services 472 Revenue recognized ( 1,260 ) Balance at December 31, 2021 $ 10,574 The Company recorded $ 1.3 million in revenue earned during the year ended December 31, 2021 , based on services performed under the Genmab Agreement during the year. Under the Genmab Agreement, the Company will be compensated for research and development services at the agreed upon full-time employee rate and third-party costs through initial clinical proof of concept of the therapeutic candidates, which also represents the period of time both parties have enforceable rights and obligations. As such, the accounting term of the Genmab Agreement was considered to terminate upon completion of the initial clinical proof of concept of the therapeutic candidates, after which both parties can exercise their respective program opt-in rights. The Genmab Agreement includes optional additional items which will be accounted for as contract modifications after initial clinical proof of concept of the therapeutic candidates. With respect to each candidate for which a party has exercised its program opt-in rights and has exclusive global rights, the other party is eligible to receive potential development and sales-based milestone payments and tiered royalties, subject to certain customary reductions, the amount of all such considerations will vary based on the market potential of the applicable territory for which such party has exercised its program opt-in rights. Under the Genmab Agreement, the Company is eligible to receive total potential milestone payments of up to $ 125.0 million in development milestones and $ 160.0 million in sale milestones per therapeutic candidate exclusively developed and commercialized by Genmab, along with tiered royalties at rates from a single digit to mid-teens percentage based on net sales of each therapeutic candidate. However, given the current phase of development of therapeutic candidates under the Genmab Agreement, the Company cannot estimate the probability or timing of achieving these milestones, and, therefore, have excluded all milestone and royalty payments from the transaction prices of the agreement. Oncology Research and Development Collaboration with Innovent Biologics, Inc. In August 2021, the Company entered into a License and Collaboration Agreement (the “Innovent Agreement”) with Innovent Biologics, Inc. (“Innovent”). Together, the companies will leverage Innovent’s proprietary therapeutic antibody portfolio and antibody discovery capability against undisclosed oncology targets in combination with the Company’s advanced ISAC technology and myeloid biology expertise to create up to three new candidates for cancer treatments. Innovent will fund the initial research, along with the preclinical and clinical development of these candidates through initial clinical proof of concept. Under the Innovent Agreement, the Company received an upfront payment of $ 5.0 million. The Company determined that the Innovent Agreement is a contract with a customer and should be accounted for under ASC 606. In conjunction with the Innovent Agreement, the Company entered into a stock purchase agreement with Innovent (the “Innovent SPA”) which contains both a put option and call option allowing Innovent and the Company to respectively initiate a market value purchase and sale of the Company’s common stock, for an aggregate investment of up to $ 10.0 million by Innovent, subject to certain share price limitations. The Innovent Agreement and Innovent SPA have been evaluated together and since the options may be exercised at market value by either party, no consideration from the Innovent SPA has been allocated to the Innovent Agreement and included in the total consideration for collaboration revenue. As of December 31, 2021 , both options remain fully outstanding and expire in May 2022 . In the Innovent Agreement, the Company has identified one bundled performance obligation that includes the license rights, research and development services and services associated with participation on a joint research committee. The transaction price includes the $ 5.0 million upfront payment and up to $ 38.2 million of estimated variable consideration related to compensation for research and development services at the agreed upon full-time employee rate and third-party costs. Collaboration revenue is recognized over time proportionate to the costs that the Company has incurred to perform the services using an input method as a measure of progress towards satisfying the performance obligation, which is based on project hours. Amounts are billed based on estimated variable consideration in the quarter ahead of performance and are trued up on the subsequent quarter’s invoice following the work performed. The cumulative effect of revisions to estimated hours to complete the Company’s performance obligation will be recorded in the period in which changes are identified and amounts can be reasonably estimated. Deferred revenue allocated to the unsatisfied performance obligation is recorded as a contract liability on the balance sheet and will be recognized over time as the services are performed. As of December 31, 2021 , contract liabilities totaling $ 5.0 million were recorded in deferred revenue with $ 0.8 million in current liabilities and $ 4.2 million in non-current liabilities on the balance sheet based on the forecasted periods of performance. There was no revenue earned during the year ended December 31, 2021, as no services had been performed under the Innovent Agreement during the period. Under the Innovent Agreement, the Company will be compensated for research and development services at the agreed upon full-time employee rate and third-party costs through initial clinical proof of concept of the therapeutic candidates, which also represents the period of time both parties have enforceable rights and obligations. As such, the accounting term of the Innovent Agreement was considered to terminate upon completion of the initial clinical proof of concept of the therapeutic candidates, after which both parties can exercise their respective license rights. The Innovent Agreement includes license options exercisable by each party to exclusively develop, manufacture and commercialize each candidate in a specific territory, which will be accounted for as contract modifications after the initial clinical proof of concept of the therapeutic candidates and the parties have exercised their respective license options with respect to each candidate. With respect to each candidate for which a party has exercised its license option, the other party is eligible to receive a license option exercise fee, potential development and sales-based milestone payments and tiered royalties, subject to certain customary reductions, the amount of all such considerations will vary based on the market potential of the applicable territory for which such party has exercised its license option. Under the Innovent Agreement, the Company is eligible to receive up to $ 28.5 million in potential license option exercise fee, $ 111.5 million in development milestone payment, $ 297.5 million in sales-based milestone payments, and tiered royalties at rates from a mid-single digit to low-teens percentage based on net sales, subject to certain customary reductions, for therapeutic candidates exclusively developed and commercialized by Innovent in specific territories. However, given the current phase of development of therapeutic candidates under the Innovent Agreement, the Company cannot estimate the probability or timing of achieving these milestones, and, therefore, have excluded all license option exercise fee, milestone and royalty payments from the transaction prices of the agreement. Oncology Clinical Trial Collaboration and Supply Agreement with Bristol-Myers Squibb In September 2021, the Company entered into a clinical collaboration and supply agreement with Bristol-Myers Squibb Company (“BMS”) to study BDC-1001 in combination with BMS’s PD-1 checkpoint inhibitor nivolumab, for the treatment of HER2-expressing solid tumors (the “BMS Agreement”). Under the BMS Agreement, BMS granted the Company a non-exclusive, non-transferrable, royalty-free license (with a right to sublicense) under its intellectual property to use nivolumab in a clinical trial for a combination therapy of nivolumab and the Company’s proprietary compound, BDC-1001, and has agreed to supply nivolumab at no cost to the Company and the Company will sponsor, fund and conduct the initial Phase 1/2 clinical trial in accordance with an agreed-upon protocol. Both parties will own the study data produced in the clinical trial, other than study data related solely to nivolumab, which will belong solely to BMS, or study data related solely to BDC-1001, which will belong solely to the Company. The parties may conduct additional clinical trials on the combined therapy which may be sponsored and funded by one party, or jointly funded. Given the terms of the BMS Agreement, the Company concluded that it is not within the scope of ASC 808 or ASC 606. Any relevant costs arising from the clinical trial will be expensed as incurred and recorded in research and development expenses. The Company initiated the clinical trial for the combination therapy of nivolumab and BDC-1001 in the fourth quarter of 2021.

Commitment and Contingencies

Commitment and Contingencies	12 Months Ended
	Dec. 31, 2021
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	7. Commitments and Contingencies Leases The Company has operating leases for its corporate office, laboratory and vivarium space in Redwood City, California. On August 7, 2020, the Company executed a non-cancellable lease agreement for 71,646 square feet of space (the “Chesapeake Master Lease”), which consists of 45,690 square feet of additional office, laboratory and vivarium space and includes an extension of 25,956 square feet under an existing lease. The Chesapeake Master Lease has an initial term of ten years from the Commencement Date, with an option to extend the lease for an additional eight-year term. The Chesapeake Master Lease contains rent escalation, and the Company is also responsible for certain operating expenses and taxes throughout the lease term. In addition, the Company is entitled to up to $ 4.8 million of tenant improvement allowance, which was paid directly by the landlord to various vendors. Upon execution of the non-cancellable lease agreement, the Company took control of 10,000 square feet of space, which is subleased as further described below. The remaining 35,690 square feet of additional office, laboratory and vivarium space commenced in June 2021 and the extension of the 25,956 square feet under an existing lease is expected to commence in 2025. As of December 31, 2021 , the operating lease right-of-use assets and operating lease liabilities for the 45,690 square feet of additional space were $ 18.0 million and $ 18.8 million, respectively. In connection with the execution of the Chesapeake Master Lease, the Company entered into two operating lease agreements to sublease portions of the premises to two unrelated third parties. The first sublease agreement, to sublease 10,000 square feet, commenced in August 2020 and will expire on July 31, 2022 . The second sublease agreement, to sublease 10,500 square feet, commenced in June 2021 and will expire on July 31, 2023 . Rent for both subleases are subject to scheduled annual increases and the subtenants are responsible for certain operating expenses and taxes throughout the term under the sublease agreements. The subtenants have no option to extend the sublease term. Sublease income under the two sublease agreements for the years ended December 31, 2021 and 2020 , was approximately $ 0.8 million and $ 0.2 million, respectively. At December 31, 2021 and 2020, finance right-of-use leases are used to finance capital equipment such as printers or ozone generators and are immaterial. The weighted-average remaining lease term and discount rate related to the Company’s lease liabilities as of December 31, 2021 were 8.0 years and 10.7 %, respectively, for the operating leases. The weighted-average remaining lease term and discount rate related to the Company’s lease liabilities as of December 31, 2020 were 6.3 years and 9.5 %, respectively, for the operating leases. The Company lease discount rates are based on estimates of its incremental borrowing rate, as the discount rates implicit in the Company’s leases cannot be readily determined. As the Company does not have any outstanding debt, the Company estimates the incremental borrowing rate based on its estimated credit rating and available market information. Cash required as security for our operation leases is secured by a letter of credit on behalf of the lessor in the amount of approximately $ 1.6 million and is recorded as restricted cash on the balance sheet as of December 31, 2021 and 2020. The components of lease expense were as follows (in thousands): Years Ended December 31, 2021 2020 Total operating lease cost $ 3,842 $ 2,508 Supplemental cash flow information related to cash paid for amounts included in the measurement of lease liabilities was as follows (in thousands): Years Ended December 31, 2021 2020 Operating cash flows from operating leases $ 3,112 $ 4,144 The following is a schedule by year for future maturities of the Company’s operating lease liabilities and sublease income to be received as of December 31, 2021 (in thousands): Operating Sublease Income 2022 $ 4,994 $ 1,048 2023 4,612 403 2024 4,772 — 2025 4,227 — 2026 3,371 — Thereafter 16,338 — Total lease payments 38,314 1,451 Less interest ( 13,959 ) Total $ 24,355 1,451 Supply Agreement The Company has entered into a supply agreement with a contract manufacturer pursuant to which the Company may be required to pay milestone payments upon the achievement of specified regulatory milestones. The agreement is cancelable by the Company upon delivering the appropriate prior written notice. At December 31, 2021 , potential future milestone payments under this agreement were up to $ 2.0 million. 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 not paid any claims or been required to defend any action related to its indemnification obligations. As of December 31, 2021, the Company does not have any material indemnification claims that were probable or reasonably possible and consequently has not recorded related liabilities. Legal Proceedings The Company is subject to claims and assessments from time to time in the ordinary course of business but is not aware of any such matters, individually or in the aggregate, that will have a material adverse effect on the Company’s financial position, results of operations or cash flows.

Convertible Preferred Stock

Convertible Preferred Stock	12 Months Ended
	Dec. 31, 2021
Equity [Abstract]
Convertible Preferred Stock	8. Convertible Preferred Stock The Company records convertible preferred stock at fair value on the dates of issuance, net of issuance costs. The convertible preferred stock is recorded outside of stockholders’ equity (deficit) because the shares contain liquidation features that are not solely within the Company’s control. The Company has elected not to adjust the carrying values of the convertible preferred stock to the liquidation preferences of such shares because it is uncertain whether or when an event would occur that would obligate the Company to pay the liquidation preferences to holders of shares of convertible preferred stock. Subsequent adjustments to the carrying values to the liquidation preferences will be made only when it becomes probable that such a liquidation event will occur. Issuance of Series T Convertible Preferred Stock On March 20, 2019, the Company entered into a convertible preferred stock purchase agreement (the “Series T Agreement”) concurrent with the Toray Agreement with a new investor (see Note 6). The Company raised a total of $ 10.0 million, net of issuance costs, from the sale of shares of Series T convertible preferred stock, including consideration allocated to the Toray Agreement. The fair value of the shares of Series T convertible preferred stock at the issuance date was $ 8.5 million, net of issuance costs. In February 2021, in connection with the Company’s IPO, all outstanding shares of Series T convertible preferred stock were converted into shares of the Company’s common stock. Issuance of Series C-1 and Series C-2 Convertible Preferred Stock In June 2020, the Company entered into a preferred stock purchase agreement (the “Series C Agreement”) with existing and new investors to raise up to $ 93.5 million in two separate tranches. The first tranche closed in June 2020 and the Company raised $ 41.3 million, net of issuance costs of $ 0.2 million, and issued 5,162,173 shares of Series C-1 convertible preferred stock at $ 8.05 per share. In addition, the investors agreed to buy, and the Company agreed to sell up to 5,611,065 shares of Series C-2 convertible preferred stock at a price per share of $ 9.2575 , for potential additional gross proceeds of $ 51.9 million, upon the achievement of certain milestones as defined in the agreement. The commitment made by the investors to invest in the second tranche of the Series C Agreement was considered a separate freestanding financial instrument and was recorded as a Convertible Preferred Stock Purchase Right Liability in the amount of $ 13.5 million upon the issuance of the first tranche of the Series C-1 convertible preferred stock in June 2020. The commitment was accounted for at fair value during the period it was outstanding with changes in fair value recorded as other income (expense) in the statement of operations and comprehensive loss. During the year ended December 31, 2021, changes in fair value of this liability totaling $ 6.1 million have been recorded in other income (expense) in the statement of operations and comprehensive loss. In January 2021, the Company issued the additional 5,611,059 shares of Series C-2 convertible preferred stock for net proceeds of $ 51.9 million and accordingly, this contractual obligation was settled, and the convertible preferred stock purchase right liability was remeasured to its fair value and reclassified to permanent equity. In February 2021, all outstanding shares of convertible preferred stock were converted into the Company’s common stock in connection with the IPO.

Common Stock

Common Stock	12 Months Ended
	Dec. 31, 2021
Equity [Abstract]
Common Stock	9. COMMON STOCK Common Stock Warrants The Company classifies common stock purchase warrants and other freestanding derivative financial instruments as equity in accordance with Accounting Standard Codification Topic 480, Distinguishing Liability from Equity . Warrants that meet the definition are classified as a component of equity and no subsequent remeasurement is required. In July 2018, the Company issued 249,218 warrants to purchase common stock in connection to the issuance of Series B convertible preferred stock. The warrants were deemed to be freestanding instruments indexed to the Company’s common stock and met the requirements for equity classification. The warrants had an expiration date of July 26, 2028 , and were exercisable at the option of the warrant holder for $ 0.07 per share. In February 2021, all outstanding warrants were exercised to purchase 82,603 shares of the Company’s common stock in connection with the IPO. Common Stock Reserved for Future Issuance The following shares of common stock were reserved for future issuance: December 31, 2021 Common stock options issued and outstanding 5,623,116 Common stock restricted stock awards issued and outstanding 336,000 Common stock available for future issuance under 1,974,700 Common stock available for future issuance under the ESPP 754,575 Total 8,688,391

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	10. STOCK-BASED COMPENSATION Approval of 2021 Equity Incentive Plan and 2021 Employee Stock Purchase Plan In January 2021, the Company’s board of directors adopted the 2021 Equity Incentive Plan (the “2021 Plan”) and the Company’s stockholders approved the 2021 Plan. The 2021 Plan authorized issuance of up to 8,075,000 shares of common stock and it became effective upon the execution of the underwriting agreement for the Company’s IPO. Stock awards granted under the 2021 Plan vest at the rate specified in the stock option agreement and shall have terms no more than ten years from the date of grant. The terms and conditions governing the stock awards under the 2021 Plan are at the sole discretion of the board of directors. In addition, in January 2021, the Company’s board of directors and stockholders adopted the 2021 Employee Stock Purchase Plan (the “ESPP”). The ESPP authorized issuance of up to 840,000 shares of common stock and it became effective upon the execution of the underwriting agreement for the Company’s IPO. The 2021 ESPP permits participants to purchase common stock through payroll deductions of up to 15 % of their eligible compensation. Employees purchase shares of common stock at a price per share equal to 85 % of the lower of the fair market value at the start or end of the six-month purchase periods within the two-year offering period. During the year ended December 31, 2021 , 85,425 shares have been issued under the 2021 ESPP. Performance and Service-Based Stock Options In September 2020, the compensation committee of the Company’s board of directors granted 526,018 options to employees that would commence vesting upon the closing of the Series C-2 financing and generally vest monthly over 48 months (the “Performance Awards”). The Company recognizes expense based on the fair value of the Performance Awards over the estimated service period (under the graded vesting method) to the extent the achievement of the related performance criteria is estimated to be probable. The Company determined that the financing milestone was achieved during January 2021. Accordingly, the Company recognized stock-based compensation expenses related to the Performance Awards of approximately $ 0.8 million and $ 0.1 million for the years ended December 31, 2021 and 2020 , respectively. The weighted-average grant date fair value of the Performance Awards was $ 3.24 per share. The following table summarizes the stock option activity during the year ended December 31, 2021: Options Outstanding Weighted-average Exercise Price Weighted-average Remaining Contractual Weighted-average Grant Date Fair Value Aggregate Intrinsic Value (in thousands) Outstanding at December 31, 2020 3,800,402 $ 3.16 9.1 $ 4,721 Granted 2,363,471 $ 14.53 $ 11.31 Exercised ( 214,438 ) $ 2.75 Canceled/forfeited ( 326,319 ) $ 7.14 Outstanding at December 31, 2021 5,623,116 $ 7.72 8.3 $ 6,075 Exercisable at December 31, 2021 1,909,810 $ 5.20 7.6 $ 3,324 Vested or expected to vest at December 31, 2021 5,623,116 $ 7.72 8.3 $ 6,075 The intrinsic value of options exercised was $ 2.7 million and $ 0.2 million during the year ended December 31, 2021 and 2020 , respectively. The fair value of options vested was $ 6.2 million and $ 1.1 million during the years ended December 31, 2021 and 2020, respectively. As of December 31, 2021 , there was approximately $ 24.2 million of unrecognized stock-based compensation related to unvested stock options, which the Company expects to recognize over a weighted-average period of 2.5 years. The fair value of each option grant was estimated on the date of grant using the Black-Scholes option-pricing model with the following assumptions: Years Ended December 31, 2021 2020 Expected volatility 89 - 95 % 90 - 97 % Risk-free interest rate 0.6 - 1.4 % 0.3 - 0.5 % Expected option life (in years) 5.8 - 6.1 5.0 - 6.3 Expected dividend yield 0.0 % 0.0 % Fair value per share of common stock $ 3.04 -$ 22.07 $ 2.80 -$ 4.41 Expected Term –The expected term of options granted represents the period of time that the options are expected to be outstanding. Due to the lack of historical exercise history, the expected term of the Company’s employee stock options has been determined utilizing the simplified method for awards that qualify as plain-vanilla options, which use the midpoint between the vesting date and the expiration date of each option. Expected Volatility –The estimated volatility was based on the historical volatility of the common stock of a group of publicly traded companies deemed comparable to the Company. Risk-Free Interest Rate –The risk-free interest rate is the implied yield in effect at the time of the option grant based on U.S. Treasury securities with contract maturities equal to the expected term of the Company’s stock options. Dividend Rate –The Company has not paid any cash dividends on common stock since inception and does not anticipate paying any dividends in the foreseeable future. Consequently, an expected dividend yield of zero was used. Fair Value of Common Stock –Prior to our IPO in February 2021, the fair value of the Company’s common stock was determined by the Company’s board of directors with assistance from management and an independent third-party valuation firm using an approach consistent with the methods outlined in the American Institute of Certified Public Accountants' Practice Aid, Valuation of Privately-Held-Company Equity Securities Issued as Compensation . Determining the best estimated fair value of the Company’s common stock required significant judgment and management considered several factors, including the Company’s stage of development, equity market conditions affecting comparable public companies, significant milestones and progress of research and development efforts. Stock-Based Compensation Expense The following table summarizes the components of stock-based compensation expense recognized in the Company’s statement of operations and comprehensive loss (in thousands): Years Ended December 31, 2021 2020 Research and development $ 4,460 $ 734 General and administrative 4,040 686 Total $ 8,500 $ 1,420 Restricted Stock Awards During the year ended December 31, 2021 , the Company granted 336,000 shares of restricted stock awards under the 2021 Plan at a grant date fair value of $ 4.51 per share. These restricted stock awards vest in equal quarterly installments over three years , subject to the employee's continued employment with, or services to, the Company on each vesting date. Each restricted stock award represents the right to receive one share of the Company's common stock when and if the applicable vesting conditions are satisfied. The following table summarizes the activity of the restricted stock awards during the year ended December 31, 2021: RSU Outstanding Weighted-average Grant Date Fair Value Outstanding at December 31, 2020 — Granted 336,000 $ 4.51 Vested — Canceled/forfeited — Outstanding at December 31, 2021 336,000 $ 4.51 As of December 31, 2021, total unrecognized stock-based compensation expense relating to unvested restricted stock awards was $ 1.5 million and the weighted-average remaining vesting period was 2.9 years. The aggregate intrinsic value of restricted stock award is calculated as the closing price per share of the Company’s common stock on the last trading day of the fiscal period, multiplied by the number of restricted stock awards expected to vest as of December 31, 2021. As of December 31, 2021, the aggregate intrinsic value of restricted stock awards was $ 1.6 million. Early Exercise Liability Some of the options granted under the prior equity incentive plan may be exercised prior to the time that the options have vested, provided that such shares remain subject to repurchase until such time as they have vested. The right to repurchase these shares lapses over the four-year vesting period. As of December 31, 2021 and 2020 , there were 1,440 and 47,180 , respectively, of unvested shares representing an early exercise liability of approximately three thousand dollars and $ 0.1 million, respectively. The unvested shares purchased by the employees are not deemed, for accounting purposes, to be outstanding. The following table summarizes the activity of the unvested stock outstanding from the early exercise of stock options: Years Ended December 31, 2021 2020 Unvested at beginning of year 47,180 16,215 Early exercised during the year — 48,412 Vested ( 45,740 ) ( 17,447 ) Unvested at end of year 1,440 47,180

Net Loss Per Share

Net Loss Per Share	12 Months Ended
	Dec. 31, 2021
Earnings Per Share [Abstract]
Net Loss Per Share	11. Net Loss Per Share The following table sets forth the computation of the Company’s basic and diluted net loss per share attributable to common stockholders, which excludes shares which are legally outstanding, but subject to repurchase by the Company (in thousands, except share and per share amounts): Years Ended December 31, 2021 2020 Numerator: Net loss $ ( 98,591 ) $ ( 60,728 ) Denominator: Weighted average common shares outstanding 33,216,339 1,989,208 Common stock outstanding subject to repurchase ( 28,453 ) ( 34,430 ) Warrants to purchase common stock 8,826 147,550 Weighted average common shares outstanding - basic 33,196,712 2,102,328 Net loss per share attributable to common stockholders, $ ( 2.97 ) $ ( 28.89 ) Potentially dilutive securities not included in the calculation of diluted net loss per share because to do so would be anti-dilutive are as follows (in common stock equivalent shares): Years Ended December 31, 2021 2020 Convertible preferred stock — 15,232,275 Common stock options issued and outstanding 5,623,116 3,800,402 Common stock outstanding subject to repurchase related 337,440 47,180 Total 5,960,556 19,079,857

401(K) Savings Plan

401(K) Savings Plan	12 Months Ended
	Dec. 31, 2021
Retirement Benefits [Abstract]
401(K) Savings Plan	12. 401(K) Savings Plan The Company established a defined-contribution savings plan under Section 401(k) of the Internal Revenue Code of 1986, as amended (“Code”). The 401(k) Plan covers all employees who meet defined minimum age and service requirements and allows participants to defer a portion of their annual compensation on a pretax basis. Beginning in 2021, the Company makes matching contributions of up to 3 % of the eligible employees’ compensation to the 401(k) plan. During the years ended December 31, 2021 and 2020 , the Company made contributions to the 401(k) plan of $ 0.3 million and nil , respectively.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Income Taxes	13. Income Taxes The Company recorded a current state tax provision of zero related to state minimum taxes for each of the years ended December 31, 2021 and 2020, which is recorded in general and administrative expenses in the accompanying statement of operations and comprehensive loss. A reconciliation of the Company’s effective tax rate and federal statutory tax rate is summarized as follows (in thousands): Years Ended December 31, 2021 2020 Income tax expense (benefit) at statutory rates $ ( 20,704 ) $ ( 12,753 ) State income tax, net of federal benefit — — Permanent items 2 11 Valuation allowance 20,028 11,002 Stock-based compensation 968 192 Research and development tax credits ( 1,572 ) ( 918 ) Preferred tranche liability fair value adjustment 1,278 2,466 Provision for income taxes $ — $ — Deferred income taxes reflect the net tax effects of loss and credit carryforwards and temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Significant components of the Company’s deferred tax assets and liabilities for federal and state income taxes are summarized as follows (in thousands): December 31, 2021 2020 Deferred tax assets: Net operating loss carryforward $ 41,548 $ 23,901 Research tax credits 6,366 3,840 Intangible assets 186 210 Reserves and accruals 827 588 Stock-based compensation 1,026 190 Lease liability 7,075 3,240 Total deferred tax assets 57,028 31,969 Less valuation allowance ( 49,385 ) ( 28,050 ) Net deferred tax assets 7,643 3,919 Deferred tax liabilities: Right-of-use assets ( 7,101 ) ( 3,654 ) Property and equipment ( 366 ) ( 198 ) Prepaid assets ( 176 ) ( 67 ) Total deferred tax assets ( 7,643 ) ( 3,919 ) Net deferred tax assets $ — $ — A valuation allowance is required to be established when it is more likely than not that all or a portion of a deferred tax asset will not be realized. Realization of deferred tax assets is dependent upon future earnings, the timing and amount of which are uncertain. A full review of all positive and negative evidence needs to be considered. The Company has established a full valuation allowance against the net deferred tax assets as of December 31, 2021 and 2020 due to historical losses and uncertainty surrounding the use of such assets. The valuation allowance increased by $ 21.3 million between December 31, 2021 and December 31, 2020 due primarily to the generation of operating losses. As of December 31, 2021, the Company has net operating loss carryforwards for federal and state income tax purposes of $ 178.1 million and $ 168.5 million, respectively. The federal net operating loss carryforwards generated prior to 2018 and state net operating loss carryforwards, if not utilized, will expire beginning in 2035 . Federal net operating losses aggregating $ 173.6 million are not subject to expiration. The Company has research credit carryforwards for federal and state income tax purposes of approximately $ 4.7 million and $ 3.6 million, respectively, as of December 31, 2021. The federal credits begin to expire in 2038 and the state credits can be carried forward indefinitely . Utilization of some of the federal and state net operating loss and credit carryforwards may be subject to annual limitations due to the change in ownership provisions of the Code and similar state provisions. The annual limitation may result in the expiration of net operating losses and credits before utilization. The Company has not performed a study under Section 382 of the Code to determine if a change in control did occur and, as such, is not able to determine the impact on the net operating loss carryforwards, if any, as of the date of the financial statements. The Company files tax returns in the United States and California. The Company is not currently under examination in any of these jurisdictions and all of the Company’s tax years remain effectively open to examination due to net operating loss carryforwards. The Company recognizes a tax benefit from uncertain tax positions when it is more likely than not that the position will be sustained upon examination, including resolutions of any related appeals or litigation processes, based on the technical merits. Due to the existence of the full valuation allowance, future changes in unrecognized tax benefits will not impact the Company’s effective tax rate. The Company does not foresee material changes to its liability for uncertain tax benefits within the next 12 months. The following table summarizes the activity in the Company’s gross unrecognized tax benefits (in thousands): Years Ended December 31, 2021 2020 Balance at beginning of period $ 1,125 $ 605 Increase related to prior year positions 4,139 — Increase related to current year positions 7,395 520 Balance at end of period $ 12,659 $ 1,125 During the years ended December 31, 2021 and 2020, no interest or penalties were recorded. In the event the Company should need to recognize interest and penalties related to unrecognized income tax liabilities, this amount will be recorded as an increase to income tax expense. On March 27, 2020, the Coronavirus Aid, Relief and Economic Security (“CARES Act”) was signed into law. Among other things, the CARES Act permits net operating loss carryovers and carrybacks to offset 100% of taxable income for taxable years beginning before 2021. In addition, the CARES Act allows net operating losses incurred in 2018, 2019, and 2020 to be carried back to each of the five preceding taxable years to generate a refund of previously paid income taxes. The CARES Act also contains modifications on the limitation of business interest for tax years beginning in 2019 and 2020. The modifications to Section 163(j) increase the allowable business interest deduction from 30% of adjusted taxable income to 50% of adjusted taxable income. The CARES Act did not have a significant impact to the Company for any years. On June 29, 2020, California Governor Newsom signed into law the state’s budget package which included Assembly Bill 85 (AB 85). AB 85 contained two major tax changes: (1) it suspends the usage of net operating losses for certain taxpayers; and (2) it limits certain business tax credits for tax years 2020, 2021, and 2022. The Company is in a taxable loss position in 2021 and thus the bill has no impact on the 2021 provision. Senate Bill 113 (SB 113), which Gov. Newsom signed into law Feb. 9, 2022, contains important California tax law changes, including reinstatement of 2022 business tax credits and net operating loss deductions limited by AB 85. The Company is in a taxable loss position in 2021 and 2020 and thus the bill has no impact on the financial statements.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2021
Subsequent Events [Abstract]
Subsequent events	14. Subsequent Events During the first three months of 2022, the Company’s compensation committee and option committee of the board of directors approved option grants to its employees under the 2021 Plan. These options totaled 2,004,989 shares with a weighted-average exercise price of $ 3.08 per share and various vesting schedules.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The Company’s financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”). Certain reclassifications on the balance sheet have been made to prior period amounts to conform to current period presentation.
Risks and Uncertainties	Risks and Uncertainties The Company is subject to a number of risks similar to other early-stage biopharmaceutical companies, including, but not limited to, changes in any of the following areas that the Company believes could have a material adverse effect on its future financial position or results of operations: risks related to the successful discovery and development of its product candidates, ability to raise additional capital, development of new technological innovations by its competitors and delay or inability to obtain chemical or biological intermediates from such suppliers required for the synthesis of the Company’s product candidates, including due to the impact of the current COVID-19 pandemic, protection of intellectual property rights, litigation or claims against the Company based on intellectual property rights, regulatory clearance and market acceptance of the Company’s products. The current COVID-19 pandemic, which is impacting worldwide economic activity, poses the risk that the Company or its employees, contractors, suppliers, and other partners may be prevented from conducting business activities for an indefinite period, including due to shutdowns that may be requested or mandated by governmental authorities. The extent to which the COVID-19 pandemic will impact the Company’s business will depend on future developments that are highly uncertain and cannot be predicted at this time. The preparation of financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. The extent to which the COVID-19 pandemic may directly or indirectly impact the Company’s financial statements is highly uncertain and subject to change. Management considered the potential impact of the COVID-19 pandemic on its estimates and assumptions and there was not a material impact to the Company’s financial statements as of and for year ended December 31, 2021; however, actual results could differ from those estimates and there may be changes to management’s estimates in future periods. The Company relies on single source manufacturers and suppliers for the supply of its product candidates. Disruption from these manufacturers or suppliers would have a negative impact on the Company’s business, financial position, and results of operations.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, and the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting period. On an ongoing basis, the Company evaluates its estimates and assumptions, including those related to revenue recognition, stock-based compensation and accrued liabilities. Management bases its estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Actual results may differ materially from those estimates.
Deferred Offering Costs	Deferred Offering Costs The Company capitalizes certain legal, accounting, and other third-party fees that are directly related to the Company’s in-process equity financings, including the IPO, until such financings are consummated. After consummation of the equity financing, these costs are recorded as a reduction of the proceeds received as a result of the offering. Should a planned equity financing be abandoned, terminated, or significantly delayed, the deferred offering costs are immediately written off to operating expenses. There were no deferred offering costs capitalized as of December 31, 2021. At December 31, 2020, deferred offering costs totaling $ 2.4 million are included as non-current assets in the accompanying balance sheet.
Concentrations of Credit Risk	Concentrations of Credit Risk Financial instruments that potentially subject the Company to concentration of credit risk consist of cash, cash equivalents and marketable securities. At December 31, 2021 and 2020 , most of the Company’s funds are invested with a registered investment manager and custodied at one financial institution, with working capital kept at a separate financial institution, and account balances may at times exceed federally insured limits. Management believes that the Company is not exposed to significant credit risk due to the financial strength of the depository institutions where the funds are held.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments purchased with an original maturity of three months or less to be cash equivalents. As of December 31, 2021 and 2020 , cash and cash equivalents consisted primarily of bank deposits and money market funds which were unrestricted as to withdrawal or use.
Marketable Securities	Marketable Securities The Company classifies its marketable securities as available-for-sale and records such assets at estimated fair value in the balance sheets, with unrealized gains and losses that are determined to be temporary, if any, reported as a component of other comprehensive income (loss) within the statements of operations and comprehensive loss and as a separate component of stockholders’ equity (deficit). The Company classifies marketable securities with remaining maturities greater than three months but less than one year as short-term investments, and those with remaining maturities greater than one year are classified as long-term investments. Investments are regularly reviewed for other-than-temporary declines in fair value. The review includes the consideration of the cause of the impairment, including the creditworthiness of the security issuers, the number of investments in an unrealized loss position, the severity and duration of the unrealized losses and whether it is more likely than not that the Company will be required to sell the investments before the recovery of their amortized cost basis. A decline in the fair value of any security below cost that is deemed other than temporary results in a charge to earnings and the establishment of a new cost basis for the security. The Company invests its excess cash balances primarily in corporate debt securities with strong credit ratings. Realized gains and losses are calculated on the specific identification method and recorded as interest income and were immaterial for all periods presented.
Restricted Cash	Restricted Cash As of December 31, 2021 and 2020 , the Company had $ 1.6 million of long-term restricted cash deposited with a financial institution. The restricted cash is held in separate bank accounts to support letter of credit agreements related to the Company’s facility leases which expire in 2025 and 2031 (see Note 7).
Property and Equipment	Property and Equipment Property and equipment are stated at cost, net of accumulated depreciation and amortization. Depreciation and amortization begin at the time the asset is placed in service. Depreciation and amortization are computed using the straight-line method over the estimated useful lives of the assets of five years . Leasehold improvements are amortized over the shorter of the lease term or the estimated useful lives of the assets. Maintenance and repairs are expensed as incurred. Upon sale or retirement of assets, the cost and accumulated depreciation and amortization are removed from the balance sheet and any resulting gain or loss is reflected in the statement of operations and comprehensive loss in the period realized.
Impairment of Long-lived Assets	Impairment of Long-Lived Assets The Company reviews long-lived assets, primarily comprised of property and equipment, for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability is measured by comparison of the carrying amount to the estimated undiscounted future cash flows, which the assets or asset groups are expected to generate. If such assets are considered to be impaired, the impairment to be recognized at the amount by which the carrying amount of the assets or asset groups exceeds the estimated fair value of the assets or asset groups. There have been no such impairments of long-lived assets during the periods presented.
Revenue Recognition	Revenue Recognition Under Accounting Standard Codification Topic 606, Revenue from Contract with Customers (“ASC 606”), the Company recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration which the Company expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that the Company determines are within the scope of ASC 606, the following steps are performed: (i) identification of a contract to provide goods or services to a customer; (ii) determination of whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration, if any; (iv) where a contract contains multiple performance obligations, the Company must allocate the transaction price to the performance obligations based on estimated selling prices; and (v) recognition of revenue when (or as) each performance obligation is satisfied. The Company only applies the five-step model to contracts when it is probable that the Company will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. At contract inception, once the contract is determined to be within the scope of ASC 606, the Company assesses the goods or services promised within each contract and determines those that are performance obligations and assesses whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied. As part of the accounting for these arrangements, the Company develops assumptions that require judgment to determine the stand-alone selling price for each performance obligation identified in the contract. The Company uses key assumptions to determine the stand-alone selling price, which may include development timelines, reimbursement rates for personnel costs, discount rates, and probabilities of technical and regulatory success. The Company evaluates each performance obligation and determines if it is satisfied over time. In addition, variable consideration must be evaluated to determine if it is constrained and, therefore, excluded from the transaction price. If the license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes revenues allocated to the license when the license is transferred to the customer and the customer is able to use and benefit from the license. For licenses that are bundled with other promised goods or services, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. Any change made to estimated progress towards completion of a performance obligation due to changes in the estimated activities required to complete the performance obligation and, therefore, revenue recognized will be recorded as a change in estimate. The Company receives payments from its collaborators based on billing schedules established in each contract. Upfront payments and other payments may require deferral of revenue recognition to a future period until the Company performs its obligation under its collaboration arrangements. Amounts are recorded as accounts receivable when the Company’s right to consideration is unconditional. The Company does not assess whether a contract has a significant financing component if the expectation at contract inception is such that the payment by the customer is akin to a deposit for research and development services. To date, all of the Company’s revenue has been derived from its development agreement with Toray Industries, Inc. (“Toray”) and Genmab A/S (“Genmab”), as described in Note 6.
Research and Development Expenses	Research and Development Expenses Research and development costs are charged to expense as incurred. Research and development expenses include certain payroll and personnel expenses, laboratory supplies, consulting costs, external contract research and development expenses, and allocated overhead, including rent, equipment depreciation and utilities. Advance payments for goods or services for future research and development activities are deferred and expensed as the goods are delivered or 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 trials on the Company’s behalf. In accruing service fees, the Company estimates the time period over which services will be performed and the level of effort to be expended in each period. These estimates are based on communications with the third-party service providers and the Company’s estimates of accrued expenses and on information available at each balance sheet date. If the actual timing of the performance of services or the level of effort varies from the estimate, the Company will adjust the accrual accordingly.
Fair Value Measurements	Fair Value Measurements Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. Cash and cash equivalents, restricted cash, marketable debt securities, accounts payable, accrued expenses and other current liabilities are reported at their respective fair values in our balance sheets. The carrying amount of the remaining financial instruments approximate fair value due to their short-term nature. Refer to Note 3 for the methodologies and assumptions used in valuing financial instruments.
Leases	Leases The Company determines whether an arrangement is a lease at inception. Specifically, it considers whether it controls the underlying asset and has the right to obtain substantially all the economic benefits or outputs from the asset. If the contractual arrangement contains a lease, the Company then determines the classification of the lease, operating or finance, using the classification criteria described in Accounting Standard Codification Topic 842, Leases (“ASC 842”). The Company has elected not to separate lease components from non-lease components, such as common area maintenance charges, and instead accounts for the lease and non-lease components as a single component. At the commencement date of a lease, the Company recognizes lease liabilities which represent its obligation to make lease payments, and right-of-use assets (“ROU assets”) which represent its right to use the underlying asset during the lease term. The lease liability is measured at the present value of lease payments over the lease term. As the Company’s leases typically do not provide an implicit rate, the Company uses an incremental borrowing rate based on the information available at the lease commencement date. The ROU asset is measured at cost, which includes the initial measurement of the lease liability and initial direct costs incurred by the Company and excludes lease incentives. ROU assets are recorded in operating lease ROU assets and lease liabilities are recorded in operating lease liabilities, current and noncurrent in the balance sheets. Lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Operating lease expense is recognized on a straight-line basis over the lease term. The Company does not recognize lease liabilities and ROU assets for short-term leases with terms of twelve months or less.
Stock-Based Compensation Expense	Stock-Based Compensation Expense The Company accounts for stock-based compensation by measuring and recognizing compensation expense for all share-based payments made to employees and non-employees based on estimated grant-date fair values. For stock-based payments with service conditions only, the Company uses the straight-line method to allocate compensation cost to reporting periods over each award’s requisite service period, which is generally the vesting period. For stock-based payments with both performance and service conditions, the Company recognizes expense based on the fair value of the performance awards over the estimated service period (under the graded vesting method) to the extent the achievement of the related performance criteria is estimated to be probable. The grant date fair value is utilized for restricted stock awards and the fair value of each stock option grant is estimated on the date of grant using the Black-Scholes model. The Black-Scholes model requires the input of subjective assumptions, including expected volatility, expected dividend yield, expected term, risk-free interest rate, and the estimated fair value of the underlying common stock on the date of grant. The Company accounts for forfeitures as they occur.
Income Taxes	Income Taxes The Company accounts for income taxes using the asset and liability method. Under this method, deferred tax assets and liabilities are determined based on differences between financial reporting and tax reporting bases of assets and liabilities and are measured using enacted tax rates and laws that are expected to be in effect when the differences are expected to reverse. Changes in deferred tax assets and liabilities are recorded in the provision for income taxes. Realization of deferred tax assets is dependent upon future earnings, the timing and amount of which are uncertain. A valuation allowance is provided against deferred tax assets unless it is more likely than not that they will be realized. The Company utilizes a two-step approach to recognize and measure uncertain tax positions. The first step is to evaluate the tax position for recognition by determining if the weight of available evidence indicates that it is more likely than not that the position will be sustained upon tax authority examination, including resolution of related appeals or litigation processes, if any. The second step is to measure the tax benefit as the largest amount that is more than 50% likely of being realized upon 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.
Net Loss Per Share	Net Loss Per Share Basic net loss per share is calculated by dividing the net loss by the weighted-average number of shares of common stock outstanding during the period, without consideration for potentially dilutive securities. Diluted net loss per share is computed by dividing the net loss by the weighted-average number of common stock and potentially dilutive securities outstanding for the period. For purposes of the diluted net loss per share calculation, convertible preferred stock, stock options, common stock subject to repurchase related to unvested restricted stock awards and early exercise of stock options are considered potentially dilutive securities. Basic and diluted net loss per share is presented in conformity with the two-class method required for participating securities as the convertible preferred stock is considered a participating security because it participates in dividends with common stock. The Company also considers the shares issued upon the early exercise of stock options subject to repurchase to be participating securities because holders of such shares have non-forfeitable dividend rights in the event a dividend is paid on common stock. The holders of all series of convertible preferred stock and the holders of early exercised shares subject to repurchase do not have a contractual obligation to share in the Company’s losses. As such, the net loss was attributed entirely to common stockholders. Because the Company has reported a net loss for all periods presented, diluted net loss per share is the same as basic net loss per share for all periods presented as potentially dilutive securities were anti-dilutive.
Comprehensive Loss	Comprehensive Loss Comprehensive loss includes all changes in equity (net assets) during a period from non-owner sources, including unrealized gains and losses on marketable securities. The Company incurred net unrealized loss on marketable securities of $ 0.3 million during the year ended December 31, 2021. During the year ended December 31, 2020 , the items qualifying as other comprehensive loss was not significant, and, therefore, the Company’s comprehensive loss was the same as its reported net loss for the period.
Segment Reporting	Segment Reporting The Company has one operating segment. Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance.
Recent Accounting Standards and Recently Adopted Accounting Pronouncements	Recent Accounting Standards From time to time, new accounting standards are issued by the Financial Accounting Standards Board (the “FASB”), or other standard setting bodies and adopted by the Company as of the specified effective date. Unless otherwise discussed, the impact of recently issued standards that are not yet effective will not have a material impact on the Company’s financial position or results of operations upon adoption. Recently Adopted Accounting Pronouncements In November 2018, the Financial Accounting Standards Board (“FASB”) issued Accounting Standard Update (“ASU”) No. 2018-18 , Collaborative Arrangements (Topic 808): Clarifying the Interaction Between Topic 808 and Topic 606 . This ASU clarifies that certain transactions between participants in a collaborative arrangement should be accounted for under ASC 606, Revenue from Contracts with Customers, when the counterparty is a customer. This ASU also precludes an entity from presenting consideration received from a transaction as revenue from contracts with customers if the counterparty is not a customer for that transaction. This ASU is effective for fiscal years beginning after December 15, 2020, and interim periods within fiscal years beginning after December 15, 2021. Early adoption is permitted for entities that have adopted ASC 606, Revenue from Contracts with Customers. The Company adopted this ASU on January 1, 2021 . The adoption of this ASU did no t result in a material impact on the Company’s financial statements and related disclosures.

Fair Value Measurements and F_2

Fair Value Measurements and Fair Value of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2021
Fair Value Disclosures [Abstract]
Schedule of Marketable Securities Classified as Available-for-sale Securities	Marketable securities, all of which are classified as available-for-sale securities, consisted of the following at December 31, 2021 and 2020 (in thousands): December 31, 2021 Amortized Unrealized Unrealized Estimated Cost Gains Losses Fair Value Asset backed securities $ 34,058 $ — $ ( 18 ) $ 34,040 U.S. treasury securities 39,985 — ( 171 ) 39,814 Other government agency securities 5,068 ( 22 ) 5,046 Commercial paper 64,956 — — 64,956 Corporate debt securities 100,438 12 ( 122 ) 100,328 Total $ 244,505 $ 12 $ ( 333 ) $ 244,184 December 31, 2020 Amortized Unrealized Unrealized Estimated Cost Gains Losses Fair Value Asset backed securities $ 2,639 $ — $ — $ 2,639 U.S. treasury securities 1,300 — — 1,300 Commercial paper 6,795 — — 6,795 Corporate debt securities 6,562 1 ( 1 ) 6,562 Total $ 17,296 $ 1 $ ( 1 ) $ 17,296
Schedule of Fair Values of Assets and Liabilities Measured at Fair Value on Recurring Basis	At December 31, 2021 and 2020, the fair values of the Company’s assets and liabilities, which are measured at fair value on a recurring basis, were determined using the following inputs (in thousands): Fair Value Measurements at Reporting Date Using December 31, 2021 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Money market funds $ 22,917 $ 22,917 $ — $ — Asset backed securities 34,040 — 34,040 — U.S. treasury securities 39,814 39,814 — — Other government agency securities 5,046 — 5,046 Commercial paper 64,956 — 64,956 — Corporate debt securities 100,328 — 100,328 — Total $ 267,101 $ 62,731 $ 204,370 $ — Fair Value Measurements at Reporting Date Using December 31, 2020 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Money market funds $ 3,921 $ 3,921 $ — $ — Asset backed securities 2,640 — 2,640 — U.S. treasury securities 1,300 1,300 — — Commercial paper 6,795 — 6,795 — Corporate debt securities 6,561 — 6,561 — Total $ 21,217 $ 5,221 $ 15,996 $ — Liabilities: Preferred stock purchase right liability $ 25,224 $ — $ — $ 25,224
Schedule of Changes in Estimated Fair Value of Financial Instruments	The following table provides a summary of changes in the estimated fair value of the financial instruments using significant Level 3 inputs (in thousands): Series C Convertible Preferred Stock Purchase Right Liability Balance at December 31, 2020 $ 25,224 Change in fair value 6,084 Reclassification to equity ( 31,308 ) Balance at December 31, 2021 $ —

Balance Sheet Components (Table

Balance Sheet Components (Tables)	12 Months Ended
	Dec. 31, 2021
Balance Sheet Related Disclosures [Abstract]
Property and Equipment, Net	Property and equipment, net, consist of the following (in thousands): December 31, 2021 2020 Laboratory equipment $ 7,889 $ 5,253 Office equipment 369 69 Leasehold improvements 145 — Total property and equipment 8,403 5,322 Less accumulated depreciation and amortization ( 2,245 ) ( 1,239 ) Total $ 6,158 $ 4,083
Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities consist of the following (in thousands): December 31, 2021 2020 Accrued research and development $ 6,300 $ 3,199 Accrued compensation 4,886 2,885 Accrued other 1,198 579 Total $ 12,384 $ 6,663

Collaborations (Tables)

Collaborations (Tables)	12 Months Ended
	Dec. 31, 2021
Toray Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Schedule of Changes in Contract Liability	The following table presents changes in the Company’s contract liability (in thousands): Balance at December 31, 2019 $ 1,571 Addition—amount billed for research and development services 162 Revenue recognized in 2020 ( 231 ) Balance at December 31, 2020 and 2021 $ 1,502
Genmab Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Schedule of Changes in Contract Liability	The following table presents changes in the Company’s contract liability (in thousands): Balance at December 31, 2020 $ — Addition—fixed consideration 11,362 Addition—amount billed for research and development services 472 Revenue recognized ( 1,260 ) Balance at December 31, 2021 $ 10,574

Commitment and Contingencies (T

Commitment and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2021
Commitments And Contingencies Disclosure [Abstract]
Components of Lease Expense	The components of lease expense were as follows (in thousands): Years Ended December 31, 2021 2020 Total operating lease cost $ 3,842 $ 2,508
Supplemental Cash Flow Information Related to Cash Paid for Amounts Included in Measurement of Lease Liabilities	Supplemental cash flow information related to cash paid for amounts included in the measurement of lease liabilities was as follows (in thousands): Years Ended December 31, 2021 2020 Operating cash flows from operating leases $ 3,112 $ 4,144
Schedule by Year for Future Maturities of Operating Lease Liabilities and Sublease Income to be Received	The following is a schedule by year for future maturities of the Company’s operating lease liabilities and sublease income to be received as of December 31, 2021 (in thousands): Operating Sublease Income 2022 $ 4,994 $ 1,048 2023 4,612 403 2024 4,772 — 2025 4,227 — 2026 3,371 — Thereafter 16,338 — Total lease payments 38,314 1,451 Less interest ( 13,959 ) Total $ 24,355 1,451

Common Stock (Tables)

Common Stock (Tables)	12 Months Ended
	Dec. 31, 2021
Equity [Abstract]
Schedule of Common Stock Reserved for Future Issuance	The following shares of common stock were reserved for future issuance: December 31, 2021 Common stock options issued and outstanding 5,623,116 Common stock restricted stock awards issued and outstanding 336,000 Common stock available for future issuance under 1,974,700 Common stock available for future issuance under the ESPP 754,575 Total 8,688,391

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Stock Option Activity	The following table summarizes the stock option activity during the year ended December 31, 2021: Options Outstanding Weighted-average Exercise Price Weighted-average Remaining Contractual Weighted-average Grant Date Fair Value Aggregate Intrinsic Value (in thousands) Outstanding at December 31, 2020 3,800,402 $ 3.16 9.1 $ 4,721 Granted 2,363,471 $ 14.53 $ 11.31 Exercised ( 214,438 ) $ 2.75 Canceled/forfeited ( 326,319 ) $ 7.14 Outstanding at December 31, 2021 5,623,116 $ 7.72 8.3 $ 6,075 Exercisable at December 31, 2021 1,909,810 $ 5.20 7.6 $ 3,324 Vested or expected to vest at December 31, 2021 5,623,116 $ 7.72 8.3 $ 6,075
Summary of Fair Value of Option Grant Estimated Using Black-Scholes Option-Pricing Model	The fair value of each option grant was estimated on the date of grant using the Black-Scholes option-pricing model with the following assumptions: Years Ended December 31, 2021 2020 Expected volatility 89 - 95 % 90 - 97 % Risk-free interest rate 0.6 - 1.4 % 0.3 - 0.5 % Expected option life (in years) 5.8 - 6.1 5.0 - 6.3 Expected dividend yield 0.0 % 0.0 % Fair value per share of common stock $ 3.04 -$ 22.07 $ 2.80 -$ 4.41
Summary of Components of Stock-Based Compensation Expense Recognized	The following table summarizes the components of stock-based compensation expense recognized in the Company’s statement of operations and comprehensive loss (in thousands): Years Ended December 31, 2021 2020 Research and development $ 4,460 $ 734 General and administrative 4,040 686 Total $ 8,500 $ 1,420
Summary of Restricted Stock Awards Activity	The following table summarizes the activity of the restricted stock awards during the year ended December 31, 2021: RSU Outstanding Weighted-average Grant Date Fair Value Outstanding at December 31, 2020 — Granted 336,000 $ 4.51 Vested — Canceled/forfeited — Outstanding at December 31, 2021 336,000 $ 4.51
Summary of Activity of Unvested Stock Outstanding from Early Exercise of Stock Options	The following table summarizes the activity of the unvested stock outstanding from the early exercise of stock options: Years Ended December 31, 2021 2020 Unvested at beginning of year 47,180 16,215 Early exercised during the year — 48,412 Vested ( 45,740 ) ( 17,447 ) Unvested at end of year 1,440 47,180

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	12 Months Ended
	Dec. 31, 2021
Earnings Per Share [Abstract]
Computation of Basic and Diluted Net Loss per Share Attributable to Common Stockholders, which excludes Shares Legally Outstanding	The following table sets forth the computation of the Company’s basic and diluted net loss per share attributable to common stockholders, which excludes shares which are legally outstanding, but subject to repurchase by the Company (in thousands, except share and per share amounts): Years Ended December 31, 2021 2020 Numerator: Net loss $ ( 98,591 ) $ ( 60,728 ) Denominator: Weighted average common shares outstanding 33,216,339 1,989,208 Common stock outstanding subject to repurchase ( 28,453 ) ( 34,430 ) Warrants to purchase common stock 8,826 147,550 Weighted average common shares outstanding - basic 33,196,712 2,102,328 Net loss per share attributable to common stockholders, $ ( 2.97 ) $ ( 28.89 )
Potentially Dilutive Securities not Included in the Calculation of Diluted Net Loss per Share	Potentially dilutive securities not included in the calculation of diluted net loss per share because to do so would be anti-dilutive are as follows (in common stock equivalent shares): Years Ended December 31, 2021 2020 Convertible preferred stock — 15,232,275 Common stock options issued and outstanding 5,623,116 3,800,402 Common stock outstanding subject to repurchase related 337,440 47,180 Total 5,960,556 19,079,857

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Summary of Reconciliation of Effective Tax Rate and Federal Statutory Tax Rate	A reconciliation of the Company’s effective tax rate and federal statutory tax rate is summarized as follows (in thousands): Years Ended December 31, 2021 2020 Income tax expense (benefit) at statutory rates $ ( 20,704 ) $ ( 12,753 ) State income tax, net of federal benefit — — Permanent items 2 11 Valuation allowance 20,028 11,002 Stock-based compensation 968 192 Research and development tax credits ( 1,572 ) ( 918 ) Preferred tranche liability fair value adjustment 1,278 2,466 Provision for income taxes $ — $ —
Summary of Significant Components of Deferred Tax Assets and Liabilities for Federal and State Income Taxes	Significant components of the Company’s deferred tax assets and liabilities for federal and state income taxes are summarized as follows (in thousands): December 31, 2021 2020 Deferred tax assets: Net operating loss carryforward $ 41,548 $ 23,901 Research tax credits 6,366 3,840 Intangible assets 186 210 Reserves and accruals 827 588 Stock-based compensation 1,026 190 Lease liability 7,075 3,240 Total deferred tax assets 57,028 31,969 Less valuation allowance ( 49,385 ) ( 28,050 ) Net deferred tax assets 7,643 3,919 Deferred tax liabilities: Right-of-use assets ( 7,101 ) ( 3,654 ) Property and equipment ( 366 ) ( 198 ) Prepaid assets ( 176 ) ( 67 ) Total deferred tax assets ( 7,643 ) ( 3,919 ) Net deferred tax assets $ — $ —
Summary of Gross Unrecognized Tax Benefits	The following table summarizes the activity in the Company’s gross unrecognized tax benefits (in thousands): Years Ended December 31, 2021 2020 Balance at beginning of period $ 1,125 $ 605 Increase related to prior year positions 4,139 — Increase related to current year positions 7,395 520 Balance at end of period $ 12,659 $ 1,125

Description of the Business - A

Description of the Business - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	Feb. 09, 2021	Feb. 04, 2021	Dec. 31, 2021	Dec. 31, 2020
Subsidiary Sale Of Stock [Line Items]
Proceeds from stock sold, net of underwriting discounts, commissions and offering costs			$ 244,316
Common stock, shares authorized		200,000,000	200,000,000	198,000,000
Preferred stock, shares authorized		10,000,000	10,000,000	0
Common Stock
Subsidiary Sale Of Stock [Line Items]
Aggregate stock sold			13,225,000
Outstanding shares of convertible preferred stock converted into common stock		20,843,334	20,843,334
IPO | Common Stock
Subsidiary Sale Of Stock [Line Items]
Aggregate stock sold	13,225,000
Sale of stock, price per share	$ 20
Proceeds from stock sold, net of underwriting discounts, commissions and offering costs	$ 242,000
Underwriters' Option | Common Stock
Subsidiary Sale Of Stock [Line Items]
Aggregate stock sold	1,725,000

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Details)	12 Months Ended
	Dec. 31, 2021USD ($)Segment	Dec. 31, 2020USD ($)
Summary Of Significant Accounting Policies [Line Items]
Deferred offering costs capitalized	$ 0
Deferred offering costs noncurrent		$ 2,400,000
Restricted cash	$ 1,565,000	1,565,000
Estimated useful life	5 years
Impairments of long-lived assets	$ 0	0
Unrecognized tax benefits, interest or penalties	0	$ 0
Net unrealized loss on marketable securities	$ (321,000)
Number of operating segment | Segment	1
Change in accounting principle, accounting standards update, adopted [true false]	true
Change in accounting principle, accounting standards update, adoption date	Jan. 1, 2021
Change in Accounting Principle, Accounting Standards Update, Immaterial Effect [true false]	true
Accounting standards update [Extensible Enumeration]	us-gaap:AccountingStandardsUpdate201818Member

Fair Value Measurements and F_3

Fair Value Measurements and Fair Value of Financial Instruments - Additional Information (Details) - USD ($)	1 Months Ended	12 Months Ended
	Jan. 31, 2021	Dec. 31, 2021	Dec. 31, 2020
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value, assets, level 1 to level 2 transfers		$ 0	$ 0
Fair value, assets, level 2 to level 1 transfers		0	0
Fair value, liabilities, level 1 to level 2 transfers		0	0
Fair value, liabilities, level 2 to level 1 transfers		0	0
Fair value, asset, transfers into level 3		0	0
Fair value, asset, transfers out of level 3		0	0
Fair value, liability, transfers into level 3		0	0
Fair value, liability, transfers out of level 3		$ 0	$ 0
Series C Convertible Preferred Stock
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of convertible preferred stock purchase right liability	$ 31,300,000
Percentage of increase in convertible preferred stock	80.00%
Period of timing related to occurrence	21 days
Increase in future expected value of share	$ 16.25

Fair Value Measurements and F_4

Fair Value Measurements and Fair Value of Financial Instruments - Schedule of Marketable Securities Classified as Available-for-sale Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	$ 244,505	$ 17,296
Unrealized Gains	12	1
Unrealized Losses	(333)	(1)
Estimated Fair Value	244,184	17,296
Asset Backed Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	34,058	2,639
Unrealized Losses	(18)
Estimated Fair Value	34,040	2,639
U.S. Treasury Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	39,985	1,300
Unrealized Losses	(171)
Estimated Fair Value	39,814	1,300
Other Government Agency Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	5,068
Unrealized Losses	(22)
Estimated Fair Value	5,046
Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	64,956	6,795
Estimated Fair Value	64,956	6,795
Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	100,438	6,562
Unrealized Gains	12	1
Unrealized Losses	(122)	(1)
Estimated Fair Value	$ 100,328	$ 6,562

Fair Value Measurements and F_5

Fair Value Measurements and Fair Value of Financial Instruments - Schedule of Fair Values of Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - Recurring Basis - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total asset	$ 267,101	$ 21,217
Liabilities:
Preferred stock purchase right liability		25,224
Money Market Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total asset	22,917	3,921
Asset Backed Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total asset	34,040	2,640
U.S. Treasury Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total asset	39,814	1,300
Other Government Agency Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total asset	5,046
Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total asset	64,956	6,795
Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total asset	100,328	6,561
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total asset	62,731	5,221
Quoted Prices in Active Markets for Identical Assets (Level 1) | Money Market Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total asset	22,917	3,921
Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Treasury Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total asset	39,814	1,300
Significant Other Observable Inputs (Level 2)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total asset	204,370	15,996
Significant Other Observable Inputs (Level 2) | Asset Backed Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total asset	34,040	2,640
Significant Other Observable Inputs (Level 2) | Other Government Agency Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total asset	5,046
Significant Other Observable Inputs (Level 2) | Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total asset	64,956	6,795
Significant Other Observable Inputs (Level 2) | Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total asset	$ 100,328	6,561
Significant Unobservable Inputs (Level 3)
Liabilities:
Preferred stock purchase right liability		$ 25,224

Fair Value Measurements and F_6

Fair Value Measurements and Fair Value of Financial Instruments - Schedule of Changes in Estimated Fair Value of Financial Instruments (Details) - Recurring Basis $ in Thousands	12 Months Ended
	Dec. 31, 2021USD ($)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Balance at December 31, 2020	$ 25,224
Change in fair value	6,084
Reclassification to equity	$ (31,308)

License and Equity Agreement -

License and Equity Agreement - Additional Information (Details) - Stanford Agreement - USD ($)	12 Months Ended		80 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2021
License And Equity Agreement [Line Items]
License and milestone fees paid	$ 40,000	$ 50,000
Additional milestone payment	200,000		$ 200,000
Royalty payments			0
General and Administrative Expense
License And Equity Agreement [Line Items]
Payments for reimbursement of patent maintenance costs	80,800	$ 100,000
Maximum
License And Equity Agreement [Line Items]
Aggregate millstone payments	$ 400,000		$ 400,000

Balance Sheet Components - Prop

Balance Sheet Components - Property and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 8,403	$ 5,322
Less accumulated depreciation and amortization	(2,245)	(1,239)
Total	6,158	4,083
Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	7,889	5,253
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross	145
Office Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 369	$ 69

Balance Sheet Components - Addi

Balance Sheet Components - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Balance Sheet Related Disclosures [Abstract]
Depreciation expense	$ 1.2	$ 0.6

Balance Sheet Components - Accr

Balance Sheet Components - Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Balance Sheet Related Disclosures [Abstract]
Accrued research and development	$ 6,300	$ 3,199
Accrued compensation	4,886	2,885
Accrued other	1,198	579
Total	$ 12,384	$ 6,663

Collaborations - Additional Inf

Collaborations - Additional Information (Details) - USD ($)	1 Months Ended			12 Months Ended
	Aug. 31, 2021	May 31, 2021	Mar. 31, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Consideration in excess of fair value				$ 241,959,000
Collaboration revenue				$ 1,260,000	$ 231,000
Common Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Issuance of shares				13,225,000
Toray Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contract liability				$ 1,502,000	$ 1,502,000	$ 1,571,000
Genmab Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contract liability				10,574,000
Upfront payment received		$ 10,000,000
Allocated from stock purchase agreement		1,400,000
Variable consideration related to reimbursements for research and development services		6,300,000
Contract liability, current				2,200,000
Contract liability, non-current				8,400,000
Collaboration revenue				1,300,000
Potential future sale milestone payments		$ 160,000,000
Genmab Agreement | Prepaid Expenses and Other Current Assets
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development services receivables				200,000
Genmab Agreement | Common Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Issuance of shares		821,045
Consideration in excess of fair value		$ 1,400,000
Purchase price under Stock Purchase Agreement		15,000,000
Genmab Agreement | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Potential future development milestone payments		$ 125,000,000
Innovent Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contract liability				5,000,000
Upfront payment received	$ 5,000,000
Allocated from stock purchase agreement	0
Contract liability, current				800,000
Contract liability, non-current				4,200,000
Collaboration revenue				$ 0
Potential future development milestone payments	111,500,000
Potential future sale milestone payments	297,500,000
Stock purchase agreement expiration date				2022-05
Innovent Agreement | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Variable consideration related to reimbursements for research and development services	38,200,000
Potential license option exercise fee	28,500,000
Innovent Agreement | Maximum | Common Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Aggregate investment under stock purchase agreement	$ 10,000,000
Series T Convertible Preferred Stock | Toray Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Issuance of shares			717,514
Consideration in excess of fair value			$ 1,500,000

Collaborations - Schedule of Ch

Collaborations - Schedule of Changes in Contract Liability (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Toray Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Beginning Balance	$ 1,502	$ 1,571
Addition - amount billed for research and development services		162
Revenue recognized in 2020 and 2021		(231)
Ending Balance	1,502	$ 1,502
Genmab Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Addition-fixed consideration	11,362
Addition - amount billed for research and development services	472
Revenue recognized in 2020 and 2021	(1,260)
Ending Balance	$ 10,574

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details)	Aug. 07, 2020USD ($)ft²	Jun. 30, 2021ft²	Dec. 31, 2021USD ($)ft²	Dec. 31, 2020USD ($)
Commitments And Contingencies [Line Items]
Operating lease right-of-use assets			$ 24,445,000	$ 12,267,000
Operating lease liabilities			24,355,000
Sublease income			$ 1,451,000
Weighted-average remaining lease term			8 years	6 years 3 months 18 days
Weighted-average discount rate			10.70%	9.50%
Cash collateral of operation leases recorded as restricted cash			$ 1,565,000	$ 1,565,000
Maximum
Commitments And Contingencies [Line Items]
Potential future milestone payments			$ 2,000,000
Chesapeake Master Lease
Commitments And Contingencies [Line Items]
Operating lease, area of property available | ft²	71,646
Operating lease, area of property, additional space available | ft²	45,690		45,690
Operating lease, area of property, extension space available | ft²	25,956	25,956
Operating lease, initial term of contract	10 years
Operating lease, option to extend	true
Operating lease, extended additional term	8 years
Tenant improvement allowance	$ 4,800,000
Operating lease, area of property subleased | ft²	10,000
Operating lease, area of property, additional space remaining | ft²		35,690
Operating lease right-of-use assets			$ 18,000,000
Operating lease liabilities			$ 18,800,000
Sublease, area of property leased | ft²	10,000
Sublease expiration date	Jul. 31, 2022		Jul. 31, 2023
Sublease, area of property expected to be leased | ft²			10,500
Operating sublease, option to extend, description			The subtenants have no option to extend the sublease term.
Operating sublease, option to extend	false
Sublease income			$ 800,000	$ 200,000

Commitments and Contingencies_2

Commitments and Contingencies - Components of Lease Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Commitments And Contingencies Disclosure [Abstract]
Total operating lease cost	$ 3,842	$ 2,508

Commitments and Contingencies_3

Commitments and Contingencies - Supplemental Cash Flow Information Related to Cash Paid for Amounts Included in the Measurement of Lease Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Commitments And Contingencies Disclosure [Abstract]
Operating cash flows from operating leases	$ 3,112	$ 4,144

Commitments and Contingencies_4

Commitments and Contingencies - Schedule by Year for Future Maturities of Operating Lease Liabilities and Sublease Income to be Received (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021USD ($)
Operating Leases
Operating Leases, 2022	$ 4,994
Operating Leases, 2023	4,612
Operating Leases, 2024	4,772
Operating Leases, 2025	4,227
Operating Leases, 2026	3,371
Operating Leases, Thereafter	16,338
Operating Leases, Total minimum lease payments	38,314
Less imputed interest	(13,959)
Operating lease liabilities	24,355
Sublease Income
Sublease Income, 2022	1,048
Sublease Income, 2023	403
Total Sublease Income	1,451
Sublease Income, Total	$ 1,451

Convertible Preferred Stock - A

Convertible Preferred Stock - Additional Information (Details)	1 Months Ended		12 Months Ended
	Jan. 31, 2021USD ($)shares	Jun. 30, 2020USD ($)Tranche$ / sharesshares	Dec. 31, 2021USD ($)shares	Dec. 31, 2020USD ($)shares	Mar. 20, 2019USD ($)
Class Of Stock [Line Items]
Convertible preferred stock value				$ 105,296,000
Convertible preferred stock, shares issued | shares			0	15,232,275
Proceeds from issuance of preferred stock, net of issuance cost			$ 51,902,000	$ 41,270,000
Series T Convertible Preferred Stock
Class Of Stock [Line Items]
Fair value of convertible preferred stock purchase right liability					$ 8,500,000
Series C Agreement
Class Of Stock [Line Items]
Convertible preferred stock, authorized amount		$ 93,500,000
Number of tranches | Tranche		2
First Tranche Series C Agreement
Class Of Stock [Line Items]
Convertible preferred stock value		$ 41,300,000
Net of issuance costs		$ 200,000
First Tranche Series C Agreement | Series C-1 Convertible Preferred Stock
Class Of Stock [Line Items]
Convertible preferred stock, shares issued | shares		5,162,173
Stock issued, price per share | $ / shares		$ 8.05
First Tranche Series C Agreement | Series C-2 Convertible Preferred Stock
Class Of Stock [Line Items]
Convertible preferred stock, shares issuable | shares		5,611,065
Stock price per share | $ / shares		$ 9.2575
Potential gross proceeds from issuance		$ 51,900,000
Second Tranche Series C Agreement
Class Of Stock [Line Items]
Changes in fair value of this liability			$ 6,100,000
Second Tranche Series C Agreement | Series C-1 Convertible Preferred Stock
Class Of Stock [Line Items]
Fair value of convertible preferred stock purchase right liability		$ 13,500,000
Second Tranche Series C Agreement | Series C-2 Convertible Preferred Stock
Class Of Stock [Line Items]
Convertible preferred stock, shares issued | shares	5,611,059
Proceeds from issuance of preferred stock, net of issuance cost	$ 51,900,000
Toray Agreement | Series T Convertible Preferred Stock
Class Of Stock [Line Items]
Convertible preferred stock value					$ 10,000,000

Common Stock - Additional Infor

Common Stock - Additional Information (Details) - USD ($)	1 Months Ended
	Jul. 31, 2018	Feb. 28, 2021
Class Of Warrant Or Right [Line Items]
Warrants issued to purchase common stock	$ 249,218
Warrants expiration date	Jul. 26, 2028
Warrant exercise price	$ 0.07
Common Stock
Class Of Warrant Or Right [Line Items]
Number of common stock purchased upon exercise of warrants		82,603

Common Stock - Schedule of Comm

Common Stock - Schedule of Common Stock Reserved for Future Issuance (Details)	Dec. 31, 2021shares
Class Of Stock [Line Items]
Common stock reserved for future issuance	8,688,391
Common Stock Options Issued and Outstanding
Class Of Stock [Line Items]
Common stock reserved for future issuance	5,623,116
Common Stock Restricted Stock Awards Issued and Outstanding
Class Of Stock [Line Items]
Common stock reserved for future issuance	336,000
Common Stock Available for Future Issuance under 2021 Plan
Class Of Stock [Line Items]
Common stock reserved for future issuance	1,974,700
Common Stock Available for Future Issuance under ESPP
Class Of Stock [Line Items]
Common stock reserved for future issuance	754,575

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		12 Months Ended
	Jan. 31, 2021	Sep. 30, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option agreement			Stock awards granted under the 2021 Plan vest at the rate specified in the stock option agreement and shall have terms no more than ten years from the date of grant. The terms and conditions governing the stock awards under the 2021 Plan are at the sole discretion of the board of directors.
Stock-based compensation expense			$ 8,500	$ 1,420
Intrinsic value of options exercised			2,700	200
Fair value of options vested			6,200	1,100
Unrecognized stock-based compensation related to unvested stock options			24,200
Performance and Service Based Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares granted		526,018
Vesting period		48 months
Stock-based compensation expense			$ 800	$ 100
Weighted-average grant date fair value of awards		$ 3.24
Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average period			2 years 6 months
Repurchase right vesting period			4 years
Unvested shares			1,440	47,180	16,215
Early exercise liability			$ 3	$ 100
Restricted Stock Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares granted			336,000
Vesting period			3 years
Weighted-average grant date fair value of awards			$ 4.51
Unrecognized stock-based compensation expense relating to unvested restricted stock awards			$ 1,500
Weighted-average period			2 years 10 months 24 days
Aggregate intrinsic value			$ 1,600
Common Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Issuance of common stock under employee stock purchase plan, Shares			125,567
2021 Plan | Common Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares authorized for issuance	8,075,000
2021 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Purchase price of stock as percentage of fair market value	85.00%
2021 Employee Stock Purchase Plan | Common Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares authorized for issuance	840,000
Plan offering period	2 years
Issuance of common stock under employee stock purchase plan, Shares			85,425
2021 Employee Stock Purchase Plan | Common Stock | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of eligible compensation for payroll deductions to purchase stock	15.00%

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Options Outstanding, Beginning balance	3,800,402
Options Outstanding, Granted	2,363,471
Options Outstanding, Exercised	(214,438)
Options Outstanding, Canceled/forfeited	(326,319)
Options Outstanding, Ending balance	5,623,116	3,800,402
Options Outstanding, Exercisable at December 31, 2021	1,909,810
Options Outstanding, Vested or expected to vest at December 31, 2021	5,623,116
Weighted-average Exercise Price, Beginning balance	$ 3.16
Weighted-average Exercise Price, Granted	14.53
Weighted-average Exercise Price, Exercised	2.75
Weighted-average Exercise Price, Canceled/forfeited	7.14
Weighted-average Exercise Price, Ending balance	7.72	$ 3.16
Weighted-average Exercise Price, Exercisable at December 31, 2021	5.20
Weighted-average Exercise Price, Vested or expected to vest at December 31, 2021	$ 7.72
Weighted-average Remaining Contractual Term (in years), Outstanding	8 years 3 months 18 days	9 years 1 month 6 days
Weighted-average Remaining Contractual Term (in years), Exercisable at December 31, 2021	7 years 7 months 6 days
Weighted-average Remaining Contractual Term (in years), Vested or expected to vest at December 31, 2021	8 years 3 months 18 days
Weighted-average Grant Date Fair Value, Granted	$ 11.31
Aggregate Intrinsic Value, Outstanding	$ 6,075	$ 4,721
Aggregate Intrinsic Value, Exercisable at December 31, 2021	3,324
Aggregate Intrinsic Value, Vested or expected to vest at December 31, 2021	$ 6,075

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of Fair Value of Option Grant Estimated Using Black-Scholes Option-Pricing Model (Details) - $ / shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility, Minimum	89.00%	90.00%
Expected volatility, Maximum	95.00%	97.00%
Risk-free interest rate, Minimum	0.60%	0.30%
Risk-free interest rate, Maximum	1.40%	0.50%
Expected dividend yield	0.00%	0.00%
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected option life (in years)	5 years 9 months 18 days	5 years
Fair value per share of common stock	$ 3.04	$ 2.80
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected option life (in years)	6 years 1 month 6 days	6 years 3 months 18 days
Fair value per share of common stock	$ 22.07	$ 4.41

Stock-Based Compensation - Su_3

Stock-Based Compensation - Summary of Components of Stock-Based Compensation Expense Recognized (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 8,500	$ 1,420
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	4,460	734
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 4,040	$ 686

Stock-Based Compensation - Su_4

Stock-Based Compensation - Summary of Restricted Stock Awards Activity (Details) - Restricted Stock Awards	12 Months Ended
	Dec. 31, 2021$ / sharesshares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
RSU Outstanding, Granted | shares	336,000
RSU Outstanding, Ending balance | shares	336,000
Weighted-average Grant Date Fair Value, Granted | $ / shares	$ 4.51
Weighted-average Grant Date Fair Value, Ending balance | $ / shares	$ 4.51

Stock-Based Compensation - Su_5

Stock-Based Compensation - Summary of Activity of Unvested Stock Outstanding from Early Exercise of Stock Options (Details) - Employee Stock Option - shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unvested at beginning of year	47,180	16,215
Early exercised during the year		48,412
Vested	(45,740)	(17,447)
Unvested at end of year	1,440	47,180

Net Loss Per Share - Computatio

Net Loss Per Share - Computation of Basic and Diluted Net Loss per Share Attributable to Common Stockholders, which excludes Shares Legally Outstanding (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Numerator:
Net loss	$ (98,591)	$ (60,728)
Denominator:
Weighted average common shares outstanding	33,216,339	1,989,208
Common stock outstanding subject to repurchase related to unvested early exercised stock options and restricted stock awards	(28,453)	(34,430)
Warrants to purchase common stock	8,826	147,550
Weighted average common shares outstanding - basic and diluted	33,196,712	2,102,328
Net loss per share attributable to common stockholders, basic and diluted	$ (2.97)	$ (28.89)

Net Loss Per Share - Potentiall

Net Loss Per Share - Potentially Dilutive Securities not Included in the Calculation of Diluted Net Loss per Share (Details) - shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities not included in the calculation of diluted net loss per share	5,960,556	19,079,857
Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities not included in the calculation of diluted net loss per share		15,232,275
Common Stock Options Issued and Outstanding
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities not included in the calculation of diluted net loss per share	5,623,116	3,800,402
Common Stock Outstanding Subject to Repurchase Related to Unvested Early Exercised Stock Options and Restricted Stock Awards
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities not included in the calculation of diluted net loss per share	337,440	47,180

401(K) Savings Plan - Additiona

401(K) Savings Plan - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Defined Contribution Plan Disclosure [Line Items]
Contributions made to savings plan	$ 0.3
Maximum
Defined Contribution Plan Disclosure [Line Items]
Percentage of matching contributions made for eligible employees	3.00%

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Operating Loss Carryforwards [Line Items]
Current state tax provision related to state minimum taxes	$ 0	$ 0
Increase in valuation allowance	21,300,000
Unrecognized tax benefits, interest or penalties	0	$ 0
Federal
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	$ 178,100,000
Net operating loss carryforwards expiration year	2035
Net operating losses not subject to expiration	$ 173,600,000
Federal | Research Credit Carryforwards
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	$ 4,700,000
Tax credit carryforwards expiration year	2038
State
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	$ 168,500,000
Net operating loss carryforwards expiration year	2035
State | Research Credit Carryforwards
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	$ 3,600,000
Tax credit carryforward expiration	indefinitely

Income Taxes - Summary of Recon

Income Taxes - Summary of Reconciliation of Effective Tax Rate and Federal Statutory Tax Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Income tax expense (benefit) at statutory rates	$ (20,704)	$ (12,753)
Permanent items	2	11
Valuation allowance	20,028	11,002
Stock-based compensation	968	192
Research and development tax credits	(1,572)	(918)
Preferred tranche liability fair value adjustment	1,278	2,466
Provision for income taxes	$ 0	$ 0

Income Taxes - Summary of Signi

Income Taxes - Summary of Significant Components of Deferred Tax Assets and Liabilities for Federal and State Income Taxes (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Net operating loss carryforward	$ 41,548	$ 23,901
Research tax credits	6,366	3,840
Intangible assets	186	210
Reserves and accruals	827	588
Stock-based compensation	1,026	190
Lease liability	7,075	3,240
Total deferred tax assets	57,028	31,969
Less valuation allowance	(49,385)	(28,050)
Net deferred tax assets	7,643	3,919
Deferred tax liabilities:
Right-of-use assets	(7,101)	(3,654)
Property and equipment	(366)	(198)
Prepaid assets	(176)	(67)
Total deferred tax assets	(7,643)	(3,919)
Net deferred tax assets	$ 0	$ 0

Income Taxes - Summary of Gross

Income Taxes - Summary of Gross Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Balance at beginning of period	$ 1,125	$ 605
Increase related to prior year positions	4,139
Increase related to current year positions	7,395	520
Balance at end of period	$ 12,659	$ 1,125

Subsequent Events - Additional

Subsequent Events - Additional Information (Details) - $ / shares	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Subsequent Event [Line Items]
Options granted		2,363,471
Weighted-average Exercise price		$ 14.53
Forecast | 2021 Plan
Subsequent Event [Line Items]
Options granted	2,004,989
Weighted-average Exercise price	$ 3.08