0001785530-22-000014 | 10-K | XBRL Viewer | Werewolf Therapeutics INC

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Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 157,531	$ 92,570
Prepaid expenses and other current assets	3,537	344
Total current assets	161,068	92,914
Property and equipment, net	2,913	651
Restricted cash	1,208	207
Operating lease right of use asset	13,412	2,471
Deferred financing costs	0	155
Other non-current assets	649	0
Total assets	179,250	96,398
Current liabilities:
Accounts payable	2,037	1,021
Accrued expenses and other current liabilities	8,765	3,586
Operating lease liability, current	1,072	677
Total current liabilities	11,874	5,284
Operating lease liability, net of current portion	14,589	1,864
Other liabilities	0	31
Total liabilities	26,463	7,179
Commitments and contingencies
Stockholders’ equity (deficit):
Preferred stock, $0.0001 par value, 5,000 shares and no shares authorized at December 31, 2021 and December 31, 2020, respectively; no shares issued or outstanding as of December 31, 2021 or December 31, 2020	0	0
Common stock, $0.0001 par value, 200,000 shares and 193,500 shares authorized as of December 31, 2021 and December 31, 2020, respectively; 27,608 and 1,746 shares issued as of December 31, 2021 and December 31, 2020, respectively; 27,313 and 1,184 shares outstanding as of December 31, 2021 and December 31, 2020, respectively	2	2
Additional paid-in capital	405,680	0
Accumulated deficit	(252,895)	(51,865)
Total stockholders’ equity (deficit)	152,787	(51,863)
Total liabilities, redeemable convertible preferred stock, and stockholders’ equity (deficit)	179,250	96,398
Series A Redeemable Convertible Preferred Stock
Redeemable convertible preferred stock:
Redeemable convertible preferred stock	0	69,012
Series B Redeemable Convertible Preferred Stock
Redeemable convertible preferred stock:
Redeemable convertible preferred stock	$ 0	$ 72,070

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Preferred stock par value (usd per share)	$ 0.0001	$ 0.0001
Preferred stock authorized (shares)	5,000,000	0
Preferred stock issued (shares)	0	0
Preferred stock outstanding (shares)	0	0
Common stock par value (usd per share)	$ 0.0001	$ 0.0001
Common stock authorized (shares)	200,000,000	193,500,000
Common stock issued (shares)	27,608,000	1,746,000
Common stock outstanding (shares)	27,313,000	1,184,000
Series A Redeemable Convertible Preferred Stock
Redeemable convertible preferred stock par value (usd per share)	$ 0.0001	$ 0.0001
Redeemable convertible preferred stock authorized (shares)	0	80,247,000
Redeemable convertible preferred stock issued (shares)	0	80,247,000
Redeemable convertible preferred stock outstanding (shares)	0	80,247,000
Redeemable convertible preferred stock liquidation preference		$ 69,012
Series B Redeemable Convertible Preferred Stock
Redeemable convertible preferred stock par value (usd per share)	$ 0.0001	$ 0.0001
Redeemable convertible preferred stock authorized (shares)	0	78,222,000
Redeemable convertible preferred stock issued (shares)	0	78,222,000
Redeemable convertible preferred stock outstanding (shares)	0	78,222,000
Redeemable convertible preferred stock liquidation preference		$ 72,070

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Operating expenses:
Research and development	$ 35,269	$ 16,641
General and administrative	14,818	5,763
Total operating expenses	50,087	22,404
Operating loss	(50,087)	(22,404)
Other income:
Change in fair value of preferred stock tranche liability	0	7,301
Interest income, net	104	63
Total other income	104	7,364
Net loss	(49,983)	(15,040)
Accretion of redeemable convertible preferred stock to redemption value	(151,942)	(13,177)
Net loss attributable to common stockholders	(201,925)	(28,217)
Net loss attributable to common stockholders	$ (201,925)	$ (28,217)
Net loss per share attributable to common stockholders, basic and diluted
Net loss per share attributable to common stockholders, basic (usd per share)	$ (10.94)	$ (28.08)
Net loss per share attributable to common stockholders, diluted (usd per share)	$ (10.94)	$ (28.08)
Weighted-average common shares outstanding, basic and diluted
Weighted average common shares outstanding, basic (shares)	18,455	1,005
Weighted average common shares outstanding, diluted (shares)	18,455	1,005

Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders’ (Deficit) Equity - USD ($) shares in Thousands, $ in Thousands	Total	Series A Redeemable Convertible Preferred Stock	Series B Redeemable Convertible Preferred Stock	Common Stock	Additional Paid-in Capital	Accumulated Deficit
Redeemable convertible preferred stock outstanding, beginning balance (shares) at Dec. 31, 2019		48,675	0
Redeemable convertible preferred stock outstanding, beginning balance at Dec. 31, 2019		$ 34,073	$ 0
Increase (Decrease) in Temporary Equity [Roll Forward]
Issuance of Series Preferred Stock, net of issuance costs (shares)		31,572	78,222
Issuance of Series Preferred Stock, net of issuance costs		$ 22,069	$ 71,763
Accretion of redeemable convertible preferred stock to redemption value		$ 12,870	$ 307
Redeemable convertible preferred stock outstanding, ending balance (shares) at Dec. 31, 2020		80,247	78,222
Redeemable convertible preferred stock outstanding, ending balance at Dec. 31, 2020		$ 69,012	$ 72,070
Stockholders' equity, beginning balance (shares) at Dec. 31, 2019				1,737
Stockholders' equity, beginning balance at Dec. 31, 2019	$ (24,304)			$ 2	$ 102	$ (24,408)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accretion of redeemable convertible preferred stock to redemption value	(13,177)				(760)	(12,417)
Stock-based compensation expense	632				632
Stock option exercises (shares)				16
Stock option exercises	26				26
Repurchases of restricted stock	0			$ (7)
Net loss	(15,040)					(15,040)
Stockholders' equity, ending balance (shares) at Dec. 31, 2020				1,746
Stockholders' equity, ending balance at Dec. 31, 2020	(51,863)			$ 2	0	(51,865)
Increase (Decrease) in Temporary Equity [Roll Forward]
Accretion of redeemable convertible preferred stock to redemption value		$ 79,372	$ 72,570
Conversion of redeemable convertible preferred stock to common stock upon closing of initial public offering (Shares)		(80,247)	(78,222)
Conversion of redeemable convertible preferred stock to common stock upon closing of initial public offering		$ (148,384)	$ (144,640)
Redeemable convertible preferred stock outstanding, ending balance (shares) at Dec. 31, 2021		0	0
Redeemable convertible preferred stock outstanding, ending balance at Dec. 31, 2021		$ 0	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock from initial public offering, net of issuance costs of $2,379 (shares)				7,500
Issuance of common stock from initial public offering, net of issuance costs of $2,379	109,221				109,221
Accretion of redeemable convertible preferred stock to redemption value	(151,942)				(895)	(151,047)
Conversion of redeemable convertible preferred stock to common stock upon closing of initial public offering (shares)				18,280
Conversion of redeemable convertible preferred stock to common stock upon closing of initial public offering	293,024				293,024
Stock-based compensation expense	4,095				4,095
Stock option exercises (shares)				82
Stock option exercises	235				235
Net loss	(49,983)					(49,983)
Stockholders' equity, ending balance (shares) at Dec. 31, 2021				27,608
Stockholders' equity, ending balance at Dec. 31, 2021	$ 152,787			$ 2	$ 405,680	$ (252,895)

Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders’ (Deficit) Equity (Parentheticals) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Issuance costs	$ 2,379
Series A Redeemable Convertible Preferred Stock
Issuance costs		$ 31
Series B Redeemable Convertible Preferred Stock
Issuance costs		$ 307

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Operating activities:
Net loss	$ (49,983)	$ (15,040)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	4,095	632
Depreciation expense	216	150
Non-cash lease expense	519	627
Change in fair value of preferred stock tranche liability	0	(7,301)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(3,072)	(177)
Other non-current assets	(649)	0
Accounts payable	1,007	388
Accrued expenses and other current liabilities	5,263	2,616
Right of use assets and operating lease liability	(241)	(527)
Other liabilities	(31)	8
Net cash used in operating activities	(42,876)	(18,624)
Investing activities:
Purchases of property and equipment	(498)	(560)
Net cash used in investing activities	(498)	(560)
Financing activities:
Deferred financing costs	0	(155)
Proceeds from initial public offering of common stock	111,600	0
Payment of equity issuance costs	(2,378)	(184)
Proceeds from stock option exercises	205	26
Net cash provided by financing activities	109,427	93,857
Net increase in cash and cash equivalents	66,053	74,673
Cash, cash equivalents and restricted cash—beginning of period	92,777	18,104
Cash, cash equivalents and restricted cash—end of period	158,830	92,777
Additional Cash Flow Elements and Supplemental Cash Flow Information [Abstract]
Cash paid for lease liabilities	1,035	844
Supplemental disclosure of non-cash investing and financing activities:
Stock option exercise receivables in prepaid expenses and other current assets	30	0
Purchases of property and equipment in accounts payable and accrued expenses	79	0
Issuance costs in accounts payable and accrued expenses	0	154
Right of use assets obtained in exchange for lease liabilities	13,658	0
Non-cash accretion of Series A and Series B redeemable convertible preferred stock	151,942	13,177
Series A Redeemable Convertible Preferred Stock
Financing activities:
Proceeds from issuance of Series A redeemable convertible preferred stock	0	22,100
Series B Redeemable Convertible Preferred Stock
Financing activities:
Proceeds from issuance of Series A redeemable convertible preferred stock	$ 0	$ 72,070

Nature of Business	12 Months Ended
Nature of Business	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Business	Nature of Business Werewolf Therapeutics, Inc. (“Werewolf” or the “Company”) was incorporated in the state of Delaware in October 2017. The Company is an innovative biopharmaceutical company pioneering the development of therapeutics engineered to stimulate the body’s immune system for the treatment of cancer. The Company’s headquarters are located in Cambridge, Massachusetts. Since inception, the Company has devoted substantially all of its time and efforts to performing research and development activities, raising capital and recruiting management and technical staff to support these operations. The Company is subject to risks and uncertainties common to early-stage companies in the biotechnology industry including, but not limited to, technical risks associated with the successful research, development and manufacturing of product candidates, development by competitors of new technological innovations, dependence on key personnel, protection of proprietary technology, compliance with government regulations and the ability to secure additional capital to fund operations. Current and future programs will require significant research and development efforts, including extensive preclinical and clinical testing and regulatory approval prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel and infrastructure. Even if the Company’s product development efforts are successful, it is uncertain when, if ever, the Company will realize significant revenue from product sales. On May 4, 2021, the Company closed its initial public offering (“IPO”) of 7,500,000 shares of the Company’s common stock at a public offering price of $16.00 per share. The gross proceeds from the IPO were $120.0 million and the net proceeds were approximately $109.2 million, after deducting underwriting discounts and commissions and other offering expenses payable by the Company. Upon completion of the Company’s IPO, all of the Company’s then outstanding preferred stock was automatically converted into an aggregate of 18,279,712 shares of common stock. The Company had cash and cash equivalents of $157.5 million at December 31, 2021. The Company expects that its cash and cash equivalents will enable it to fund its operating expenses and capital expenditure requirements for at least twelve months from the filing date of this Annual Report on Form 10-K. However, additional funding will be necessary beyond this point to fund future preclinical and clinical activities. The Company expects to finance its future cash needs through a combination of equity or debt financings, collaboration agreements, strategic alliances and licensing arrangements.

Basis of Presentation and Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Basis of Presentation and Summary of Significant Accounting Policies	Basis of Presentation and Summary of Significant Accounting Policies Basis of Presentation and Consolidation The accompanying consolidated financial statements have been prepared in accordance with the rules and regulations of the Securities and Exchange Commission (the “SEC”) and generally accepted accounting principles in the United States of America (“GAAP”) as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Updates (“ASU”) of the Financial Accounting Standards Board (“FASB”). The accompanying consolidated financial statements include the accounts of Werewolf Therapeutics, Inc. and its wholly-owned subsidiary, Werewolf Therapeutics Mass Securities, Inc. All intercompany transactions and balances have been eliminated in consolidation. Segment Information Operating segments are identified as components of an enterprise for which separate discrete financial information is available for evaluation by the Company’s Chief Operating Decision Maker (“CODM”) to make decisions with respect to resource allocation and assessment of performance. The CODM is the Company’s Chief Executive Officer. The CODM manages the Company’s operations as a single segment for the purposes of assessing performance and making operating decisions. The Company’s singular concentration is focused on the discovery and development of cancer therapeutics by advancing a novel class of conditionally activated proinflammatory immune modulators. Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. On an ongoing basis, the Company’s management evaluates its estimates which include, but are not limited to, the fair values of common stock and redeemable convertible preferred stock and the fair value of the preferred stock tranche rights. Actual results could differ from those estimates. Fair Value of Financial Instruments ASU No. 2018-13, Fair Value Measurement (Topic 820): Disclosure for Fair Value Measurement (“ASC 820”), establishes a fair value hierarchy for instruments measured at fair value that distinguishes between assumptions based on market data (observable inputs) and the Company’s own assumptions (unobservable inputs). Observable inputs are inputs that market participants would use in pricing the asset or liability based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the inputs that market participants would use in pricing the asset or liability and are developed based on the best information available in the circumstances. ASC 820 identifies fair value as the exchange price, or exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As a basis for considering market participant assumptions in fair value measurements, ASC 820 establishes a three-tier fair value hierarchy that distinguishes between the following: •Level 1 inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities. •Level 2 inputs are inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly. •Level 3 inputs are unobservable inputs that reflect the Company’s own assumptions about the assumptions market participants would use in pricing the asset or liability. Financial assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. Cash and Cash Equivalents The Company’s cash and cash equivalents consist of cash maintained within a standard checking account. The Company also maintains a cash sweep account in which cash from its main operating cash account is invested overnight in highly liquid, short-term investments. The Company considers all highly liquid investments with a maturity date of 90 days or less at the date of purchase to be cash equivalents. Property and Equipment Property and equipment is recorded at cost and consists of laboratory equipment, furniture and office equipment, computer equipment, and leasehold improvements. The Company capitalizes property and equipment that is acquired for research and development activities and that has alternate future use. Expenditures for maintenance and repairs are recorded to expense as incurred, whereas major betterments are capitalized as additions to property and equipment. Leasehold improvements are depreciated over the lesser of their useful life or the term of the lease. Depreciation is calculated over the estimated useful lives of the assets using the straight-line method. Impairment of Long-lived Assets Long-lived assets consist of property and equipment. The Company reviews its property and equipment whenever events or changes in circumstances indicate that the carrying value of certain assets might not be recoverable and recognizes an impairment loss when it is probable that an asset’s realizable value is less than the carrying value. Leases At the inception of an arrangement, the Company determines whether the arrangement is or contains a lease based on the unique facts and circumstances present in the arrangement. Leases with a term greater than one year are recognized on the balance sheet as right-of-use assets and short-term and long-term lease liabilities, as applicable. The Company does not recognize leases with terms of one year or less on the balance sheet. Options to renew a lease are not included in the Company’s initial lease term assessment unless there is reasonable certainty that the Company will renew. The Company monitors its plans to renew its material leases on a quarterly basis. Operating lease liabilities and their corresponding right-of-use assets are recorded based on the present value of lease payments over the expected remaining lease term. Certain adjustments to the right-of-use asset may be required for items such as incentives received. The interest rate implicit in lease contracts is typically not readily determinable. As a result, the Company utilizes its incremental borrowing rate (“IBR”), which reflects the fixed rate at which the Company could borrow on a collateralized basis the amount of the lease payments in the same currency, for a similar term, and in a similar economic environment. The Company subsequently measures its lease liability at the present value of remaining lease payments, discounted using the IBR for the lease. The right-of-use asset is subsequently measured at the amount of the lease liability, adjusted for prepaid or accrued lease payments and the remaining balance of lease incentives received. The Company recognizes operating lease expense on a straight-line basis over the lease term. Revenue Recognition The Company analyzes its collaborations to assess whether such arrangements involve joint operating activities performed by parties that are both active participants in the activities and exposed to significant risks and rewards dependent on the commercial success of such activities and therefore within the scope of ASC Topic 808, Collaborative Arrangements (“ASC 808”). This assessment is performed throughout the life of the arrangement based on changes in the responsibilities of all parties in the arrangement. For arrangements within the scope of ASC 808 that contain multiple elements, the Company first determines which elements of the collaboration are deemed to be within the scope of ASC 808 and which elements of the collaboration are more reflective of a vendor-customer relationship and therefore within the scope of ASC Topic 606, Revenue from Contracts with Customers (“ASC 606”). For elements of collaboration arrangements that are accounted for pursuant to Topic 808, an appropriate recognition method is determined and applied consistently, either by analogy to authoritative accounting literature or by applying a reasonable and rational policy election. For those elements of the arrangement that are accounted for pursuant to ASC 606, the Company recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration that the entity expects to receive in exchange for those goods or services. In applying ASC 606, the Company performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the promises and performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the Company satisfies the performance obligations. The Company only applies the five-step model to contracts when it is probable that it will collect the consideration to which it is entitled 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, 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 assessment, the Company must develop assumptions that require judgment to determine the standalone selling price for each performance obligation identified in the contract. The Company uses key assumptions to determine the standalone selling price, which may include reimbursement rates for personnel costs, development timelines and probabilities of regulatory success. The Company does not assess whether a contract has a significant financing component if the expectation at contract inception is that the period between payment by the customer and the transfer of promised goods or services to the customer will be one year or less. Arrangements that include upfront payments may require deferral of revenue recognition to a future period until obligations under these arrangements are fulfilled. The event-based milestone payments represent variable consideration, and the Company uses the “most likely amount” method to estimate this variable consideration. Given the high degree of uncertainty around the occurrence of these events, the Company determined the milestone and other contingent amounts to be fully constrained until the uncertainty associated with these payments is resolved. Revenue will be recognized from sales-based royalty payments when or as the sales occur. The Company will re-evaluate the transaction price in each reporting period as uncertain events are resolved and other changes in circumstances occur. Research and Development Expenses Expenditures relating to research and development are expensed as incurred. Research and development expenses include external expenses incurred under arrangements with third parties, academic and non-profit institutions and consultants; salaries and personnel-related costs, including non-cash stock-based compensation expense; license fees to acquire in-process technology and other expenses, which include direct and allocated expenses for laboratory, facilities and other costs. Non‑refundable advance payments for goods and services that will be used in future research and development activities are expensed when the activity has been performed or when the goods have been received rather than when the payment is made. As part of the process of preparing the consolidated financial statements, the Company is required to estimate its accrued research and development expenses as of each balance sheet date. 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. This process involves reviewing open contracts and purchase orders, communicating with internal personnel to identify services that have been performed on the Company’s behalf and estimating the level of service performed and the associated cost incurred for the service when the Company has not yet been invoiced or otherwise notified of the actual cost. The Company periodically confirms the accuracy of its estimates with its service providers and makes adjustments if necessary. The majority of the Company’s service providers invoice monthly in arrears for services performed or when contractual milestones are met. The financial terms of agreements with these service providers are subject to negotiation, vary from contract to contract and may result in uneven payment flows. In circumstances where amounts have been paid in excess of costs incurred, the Company records a prepaid expense. Intellectual Property Expenses The Company expenses costs associated with intellectual property-related matters as incurred and classifies such costs as general and administrative expenses within the consolidated statements of operations. Stock-based Compensation The Company accounts for stock-based payments in accordance with ASU No. 2018-07, Compensation—Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting (“ASC 718”). This guidance requires all stock-based payments to employees, including grants of employee stock options and restricted stock awards (“RSAs”), to be recognized as expense in the consolidated statements of operations and comprehensive (loss) income based on their grant date fair values. For stock options granted to employees and to members of the Company’s board of directors for their services on the board of directors, the Company estimates the grant date fair value of each stock option using the Black-Scholes option-pricing model. For restricted stock units (“RSUs”) and RSAs granted to employees, the Company estimates the grant date fair value of each award using intrinsic value, which is based on the value of the underlying common stock less any purchase price. For stock-based payments subject to service-based vesting conditions, the Company recognizes stock-based compensation expense equal to the grant date fair value of stock-based payment on a straight-line basis over the requisite service period. The Black‑Scholes option pricing model requires the input of certain subjective assumptions, including (i) the calculation of expected term of the stock-based payment, (ii) the risk‑free interest rate, (iii) the expected stock price volatility and (iv) the expected dividend yield. The Company uses the simplified method as proscribed by SEC Staff Accounting Bulletin No. 107 to calculate the expected term for stock options granted to employees as the Company does not have sufficient historical exercise data to provide a reasonable basis upon which to estimate the expected term. The Company determines the risk‑free interest rate based on a treasury instrument whose term is consistent with the expected term of the stock options. Because there had been no public market for the Company’s common stock prior to the Company’s IPO, there is a lack of Company‑specific historical and implied volatility data. Accordingly, the Company bases its estimates of expected volatility on the historical volatility of a group of publicly-traded companies with similar characteristics to itself, including stage of product development and therapeutic focus within the life sciences industry. Historical volatility is calculated over a period of time commensurate with the expected term of the stock-based payment. The Company uses an assumed dividend yield of zero as the Company has never paid dividends on its common stock, nor does it expect to pay dividends on its common stock in the foreseeable future. The Company accounts for forfeitures of all stock-based payments when such forfeitures occur. Income Taxes Income taxes are recorded in accordance with ASU No. 2019-12, Income Taxes (Topic 740) (“ASC 740”) which provides for deferred taxes using an asset and liability approach. The Company recognizes deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the consolidated financial statements or tax returns. Deferred tax assets and liabilities are determined based on the difference between the financial statement and tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. A valuation allowance against deferred tax assets is recorded if, based on the weight of the available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized. The Company accounts for uncertain tax positions using a more-likely-than-not threshold for recognizing and resolving uncertain tax positions. The evaluation of uncertain tax positions is based on factors, including, but not limited to, changes in the law, the measurement of tax positions taken or expected to be taken in tax returns, the effective settlement of matters subject to audit, new audit activity and changes in facts or circumstances related to a tax position. Comprehensive Loss The Company does not have items of other comprehensive loss for the years ended December 31, 2021 and 2020, and therefore does not present a consolidated statement of comprehensive loss. The Company’s comprehensive loss equals its net loss. Net Loss per Common Share Basic net loss per share is computed using the “two-class” method, which includes the weighted average number of shares of common stock outstanding during the period and other securities that participate in undistributed earnings (a participating security). The Company’s redeemable convertible preferred stock and restricted stock awards are participating securities as defined by ASU No. 2017-10, Earnings per Share (Topic 260) (“ASC 260-10”). During the periods where the Company incurs net losses, the Company allocates no loss to participating securities because these securities have no contractual obligation to share in the losses of the Company. Under the two-class method, basic net loss per share applicable to common stockholders is computed by dividing the net loss applicable to common stockholders by the weighted average number of common shares outstanding for the period. Diluted net loss per share is computed similar to basic net loss per share except that the denominator is increased to include the number of additional shares for the potential dilutive effects of warrants, redeemable convertible preferred stock and stock options outstanding during the period calculated in accordance with the treasury stock method, or the two-class method, whichever is more dilutive. The Company allocates net earnings on a pari passu (equal) basis to both common and preferred stockholders. Net losses are not allocated to preferred stockholders as they do not have an obligation to share in the Company’s net losses. For all periods presented, basic and diluted net loss per share are the same, as any additional share equivalents would be anti-dilutive. Concentration of Credit Risk and Off-Balance Sheet Risk Financial instruments that potentially subject the Company to significant concentrations of credit risk consist of cash and cash equivalents. Cash is held in a checking account at two financial institutions. At times, such deposits may be in excess of insured limits. The Company has not experienced any losses on its deposits of cash and cash equivalents. The Company has no significant off-balance sheet concentrations of credit risk, such as foreign currency exchange contracts, option contracts or other hedging arrangements. Recent Accounting Pronouncements In October 2020, the FASB issued ASU No. 2020-10, Codification Improvements (“ASU 2020-10”), which updates various codification topics by clarifying or improving disclosure requirements to align with the SEC’s regulations. The Company adopted ASU 2020-10 as of the reporting period beginning January 1, 2021 and the adoption did not have material impact on the Company’s consolidated balance sheets, consolidated statements of operations or related disclosures. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments—Credit Losses (Topic 326), Measurement of Credit Losses on Financial Instruments. This guidance amends the impairment model by requiring entities to use a forward-looking approach based on expected losses to estimate credit losses for most financial assets and certain other instruments that aren’t measured at fair value through net income. The Company has adopted the new guidance effective January 1, 2021 and the adoption did not have any material impact on the Company’s consolidated balance sheets, consolidated statements of operations or related disclosures. In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740), Simplifying the Accounting for Income Taxes (“ASU 2019-12”), which is intended to simplify various areas related to accounting for income taxes. ASU 2019-12 removes certain exceptions to the general principles in ASC 740 and also clarifies and amends existing guidance to improve consistent application. For public business entities, the guidance is effective for annual reporting periods beginning after December 15, 2020 and for interim periods within those fiscal years. The Company adopted the standard effective January 1, 2021 and the adoption did not have a material impact on the Company’s consolidated financial statements. Subsequent Events The Company has evaluated subsequent events and transactions that occurred after the balance sheet date up to the date that the financial statements were issued. Other than as described in these financial statements, the Company did not identify any subsequent events that would have required adjustment to or disclosure in the financial statements.

Financial Instruments and Fair Value Measurements

12 Months Ended

Dec. 31, 2021

Fair Value Disclosures [Abstract]

Financial Instruments and Fair Value Measurements

The Company measures the fair value of money market funds based on quoted prices in active markets for identical securities.

The carrying amounts reflected in the consolidated balance sheets for cash, prepaid expenses and other current assets, accounts payable and accrued expenses approximate their fair values, due to their short-term nature.

Assets measured at fair value on a recurring basis as of December 31, 2021 were as follows (in thousands):


	Quoted Price in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Total
Assets:
Money market funds	$	157,531	$	—	$	—	$	157,531
Total assets	$	157,531	$	—	$	—	$	157,531

Assets measured at fair value on a recurring basis as of December 31, 2020 were as follows (in thousands):


	Quoted Price in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Total
Assets:
Money market funds	$	92,570	$	—	$	—	$	92,570
Total assets	$	92,570	$	—	$	—	$	92,570

There were no changes in valuation techniques during the years ended December 31, 2021 and 2020. There were no liabilities measured at fair value on a recurring basis as of December 31, 2021 or 2020.

Preferred Stock Tranche Liability—During 2019, the Company issued 48,675,140 shares of Series A redeemable convertible preferred stock (“Series A Preferred Stock”) which contained the preferred stock tranche liability. The fair value of the preferred stock tranche liability was $7.8 million upon issuance and was remeasured to $7.3 million as of December 31, 2019. The preferred stock tranche liability was settled in June 2020 upon the closing of the second tranche of the Series A Preferred Stock.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Restricted Cash	12 Months Ended
Restricted Cash	Dec. 31, 2021
Cash and Cash Equivalents [Abstract]
Restricted Cash	Restricted CashThe Company maintained restricted cash of $1.3 million and $0.2 million at December 31, 2021 and December 31, 2020, respectively. At December 31, 2021, $0.1 million of the Company’s restricted cash balance is included within “Prepaid expenses and other current assets” in the accompanying consolidated balance sheets. These amounts are comprised solely of letters of credit required pursuant to the Company’s leased office spaces.

Property and Equipment, Net

12 Months Ended

Dec. 31, 2021

Property, Plant and Equipment [Abstract]

Property and Equipment, Net

Property and equipment, net as of December 31, 2021 and 2020 was comprised as follows (in thousands):


		December 31,
	Estimated Useful Life (in years)	2021		2020
Laboratory equipment	5	$	839	$	606
Furniture and office equipment	5	9		13
Computer equipment	3	221		19
Leasehold improvements	Shorter of 7 years or remaining lease term	274		188
Construction in progress		1,961		—
Total property and equipment, gross		3,304		826
Less: accumulated depreciation		(391)		(175)
Total property and equipment, net		$	2,913	$	651

Depreciation expense for the years ended December 31, 2021 and 2020 was $216,000 and $150,000, respectively.

Accrued Expenses and Other Current Liabilities

12 Months Ended

Dec. 31, 2021

Payables and Accruals [Abstract]

Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities as of December 31, 2021 and 2020 were comprised as follows (in thousands):


	December 31,
	2021		2020
Manufacturing	$	3,427	$	1,741
Employee compensation and benefits	2,200		990
Professional fees	433		654
Contract research	2,542		107
Other	163		94
Total accrued expenses and other current liabilities	$	8,765	$	3,586

Term Loan	12 Months Ended
Term Loan	Dec. 31, 2021
Debt Disclosure [Abstract]
Term Loan	Term Loan In May 2020, the Company entered into a Loan and Security Agreement (the “Loan Agreement”) with Pacific Western Bank (“PWB”). Under the terms of the Loan Agreement, PWB made available a term loan up to $6.0 million (“Term Loan A”). Based on the satisfaction of certain conditions defined in the Loan Agreement, PWB was also obligated to make available an additional term loan in the amount of up to $8.0 million until November 29, 2021 (“Term Loan B”, or collectively with Term Loan A, the “Term Loans”). The Company satisfied the conditions to draw Term Loan B in June 2020. Although Term Loan A was made available to the Company at the closing date, the Company elected to forgo making a draw, thereby incurring a delayed draw fee of $25,000 with PWB. The Term Loans would have borne interest on the outstanding daily balance at a floating annual rate equal to greater of: (i) 1.75% above the prime rate then in effect or (ii) 5.00%. If the prime rate changed throughout the term, the interest rate would have been adjusted effective on the date of the prime rate change. All interest chargeable under the Loan Agreement would have been computed on a 360-day year for the actual number of days elapsed, with interest payable monthly. The Company would have been obligated to pay PWB a fee of 5.00% of the amount drawn under the Term Loans upon the occurrence of the Company achieving certain conditions defined in the Loan Agreement (the “Success Fee”). The Success Fee would have survived ten years from the date of payment of the Term Loan in full, such that, if the Loan Agreement was terminated prior to the payment of the Success Fee, the Company would have remained obligated to pay the Success Fee upon the occurrence of a Success Fee Event (as described in the Loan Agreement). The Company determined that the Success Fee constituted a freestanding financial instrument that should be accounted for as a liability in connection with ASC 480—Distinguishing Liabilities from Equity. The Company determined that the fair value of the Success Fee was immaterial at both issuance and through the expiration of the Loan Agreement. Borrowings under the Loan Agreement would have been secured by the Company’s personal property (exclusive of any intellectual property) and were subject to acceleration in the event of default. In the event of a late payment or default, the Company would have been obligated to pay a fee equal to 5.0% of such unpaid amounts. In connection with the Loan Agreement, the Company was required to comply with certain covenants, which among other things, restricted the Company from (i) effectuating a merger or consolidation with or into any other business organization, (ii) paying dividends or making certain other distributions and (iii) making investments in any entities or instruments other than certain investments specified in the Loan Agreement. In addition, the Loan Agreement contained standard affirmative covenants, including with respect to the issuance of audited consolidated financial statements, insurance, and maintenance of good standing and government compliance in the Company’s state of formation. The Company was also required to maintain unrestricted cash balances of at least 2.5 times its monthly cash burn, and had covenanted not to make any capital expenditures in excess of $0.4 million in the aggregate in any fiscal year without the prior written consent of PWB. In December 2020, the Loan Agreement was amended to allow the Company to make investments in its subsidiary, Werewolf Therapeutics Mass Securities, Inc., subject to certain conditions described in the Loan Agreement. In February 2021, the Loan Agreement was amended such that the Company may not make any capital expenditures in excess of $2.0 million in the aggregate in 2021 and $0.5 million in the aggregate in any fiscal year thereafter without the prior written consent of PWB. PWB would have had the right to accelerate all obligations of the Company in the event of a material adverse effect on (i) the operations, business or financial condition of the Company, (ii) the Company’s ability to repay any portion of the Term Loans or perform any of its other obligations under the Loan Agreement and (iii) the Company’s interest in, or the value, perfection or priority of PWB’s security interest in the collateral. The Company did not draw down any Term Loans, and as a result, the Loan Agreement expired on November 29, 2021.

- Definition

The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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+ Details

Common and Preferred Stock

12 Months Ended

Dec. 31, 2021

Equity [Abstract]

Common and Preferred Stock

Common Stock

The Company is authorized to issue 200.0 million shares of common stock. Common stockholders are entitled to dividends if and when declared by the Company’s board of directors. As of December 31, 2021, no dividends on common stock had been declared by the Company.

The Company had reserved shares of common stock for issuance as follows (in thousands):


	As of December 31,
	2021	2020
Redeemable convertible preferred stock outstanding	—	18,280
Options issued and outstanding	3,266	2,059
Warrants issued and outstanding	59	59
Total	3,325	20,398

Redeemable Convertible Preferred Stock

The Company’s Series A and Series B redeemable convertible preferred stock, together referred to as “Preferred Stock,” was classified as temporary equity on the accompanying consolidated balance sheets in accordance with authoritative guidance for the classification and measurement of redeemable securities as the preferred stock was redeemable upon the occurrence of a deemed liquidation event. Upon completion of the Company’s IPO, all of the Company’s then outstanding preferred stock was automatically converted into an aggregate of 18.3 million shares of common stock.

Series A Preferred Stock

The Series A Preferred Stock shares were issued at various closing dates between 2019 and 2020 for a purchase price of $0.70 per share. The shares were issued in exchange for cash proceeds of $44.0 million, net of issuance costs of $0.2 million, and the exchange of approximately $12.0 million in outstanding convertible notes, including accrued interest.

Tranche Rights Issued with Series A Preferred Stock

Included in the terms of the Series A Preferred Stock purchase agreement (the “Series A Stock Purchase Agreement”) were certain tranche rights (the “Tranche Rights”). The Tranche Rights obligated the Series A Preferred Stock investors to purchase, and the Company to sell, an additional 31,571,425 shares of Series A Preferred Stock for a purchase price of $0.70 per share (the “Second Closing”) on November 1, 2020 or based on the election of each investor prior to the Second Closing. On May 12, 2020, the Series A Stock Purchase Agreement was amended such that the Second Closing would occur on June 1, 2020 or on an earlier date at the election of each investor.

The Company concluded that the Tranche Rights met the definition of a freestanding financial instrument, as the Tranche Rights were legally detachable and separately exercisable from the Series A Preferred Stock. Therefore, the Company allocated the net proceeds between the Tranche Rights and the Series A Preferred Stock. The trigger for the Second Closing was based on the passage of time or the election of the holders of Series A Preferred Stock. Based on the contractual terms, and the fact that the issuance was based on an event that was not within the control of the Company (i.e., written consent or passage of time), the Tranche Rights imposed an obligation on the Company to issue shares. Since the Series A Preferred Stock was contingently redeemable, the Tranche Rights were classified as a liability under ASC 480, Distinguishing Liabilities from Equity, and were initially recorded at fair value. The Tranche Rights were measured at fair value at each reporting period. Since the Tranche Rights were subject to fair value accounting, the Company allocated the proceeds to the Tranche Rights based on the fair value at the date of issuance with the remaining proceeds being allocated to the Series A Preferred Stock.

The estimated fair value of the Tranche Rights was determined using a probability-weighted present value model that considered the probability of closing a tranche, the estimated future value of Series A redeemable convertible preferred stock at each closing and the investment required at each closing. Future values were converted to present value using a discount rate appropriate for probability-adjusted cash flows. The Tranche Rights were initially recorded as a liability of $7.8 million. The Company remeasured the liability on each subsequent balance sheet date and prior to settlement and issuance of shares in connection with the Second Closing, which occurred on June 1, 2020.

Series B Preferred Stock

The Series B Preferred Stock shares were issued for a purchase price of $0.92 per share. The issuance resulted in cash proceeds of $71.8 million, net of issuance costs of $0.3 million.

Redemption

Upon certain change in control events that are outside of the Company’s control, including liquidation, sale or transfer of control of the Company, the Preferred Stock was contingently redeemable. In addition, the Preferred Stock was redeemable at any time on or after the fifth anniversary of the original issue date. The Preferred Stock was redeemable at a price equal to the greater of (i) the original issue price of $0.70 per share for Series A Preferred stock and the original issue price of $0.92 per share for Series B Preferred Stock, respectively, or (ii) the fair market value of the Series A Preferred Stock and Series B Preferred Stock, as applicable, as of the redemption request date. As the Preferred Stock approached becoming redeemable due to the passage of time, the Company recorded changes in the redemption value and accreted the Preferred Stock immediately to redemption value as it occurred.

Preferred Stock

The Company is authorized to issue 5.0 million shares of undesignated preferred stock in one or more series. As of December 31, 2021, no shares of preferred stock were issued or outstanding.

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Stock-based Compensation

12 Months Ended

Dec. 31, 2021

Share-based Payment Arrangement [Abstract]

Stock-based Compensation

2017 Stock Incentive Plan

In December 2017, the Company adopted the 2017 Stock Incentive Plan (the “2017 Plan”), as amended and restated, under which it could grant incentive stock options (“ISOs”), non-qualified stock options, RSAs, RSUs, stock appreciation rights and other stock-based awards to eligible employees, officers, directors and consultants. The terms of stock options and restricted stock awards, including vesting requirements, are determined by the board of directors, subject to the provisions of the Plan.

2021 Stock Incentive Plan

In April 2021, the board of directors adopted and the Company’s stockholders approved the 2021 Stock Incentive Plan (the “2021 Plan”), which became effective immediately prior to the effectiveness of the Company’s IPO. As a result of the adoption of the 2021 Plan, no further awards will be made under the 2017 Plan.

The 2021 Plan provides for the grant of ISOs, non-qualified stock options, RSAs, RSUs, stock appreciation rights and other stock-based awards. The Company’s employees, officers, directors, consultants and advisors are eligible to receive awards under the 2021 Plan. The terms of awards, including vesting requirements, are determined by the board of directors, subject to the provisions of the 2021 Plan.

The Company initially registered 3,352,725 shares of common stock under the 2021 Plan, pursuant to a Registration Statement on Form S-8 filed with the SEC on April 30, 2021, which was comprised of (i) 2,843,116 shares of common stock reserved for issuance under the 2021 Plan, (ii) 31,884 shares of common stock originally reserved for issuance under the 2017 Plan that became available for issuance under the

2021 Plan upon the completion of the Company’s IPO, and (iii) 477,725 shares of unvested restricted stock subject to repurchase by us that may become issuable under the 2021 Stock Incentive Plan following such repurchase. The 2021 Plan also provides that an additional number of shares will be added annually to the shares authorized for issuance under the 2021 Plan on the first day of each fiscal year, beginning with the fiscal year ending December 31, 2022 and continuing until, and including, the fiscal year ended December 31, 2031. The number of shares added each year will be equal to the lesser of (i) 5% of the number of outstanding common stock on such date and (ii) such amount as determined by the board of directors.

As of December 31, 2021, there were 1,938,895 shares available for future issuance under the 2021 Plan.

2021 Employee Stock Purchase Plan

In April 2021, the board of directors adopted and the Company’s stockholders approved the 2021 Employee Stock Purchase Plan (the “2021 ESPP”), which became effective immediately prior to the effectiveness of the Company’s IPO. The Company initially reserved 244,000 shares of common stock for future issuance under the 2021 ESPP. The 2021 ESPP provides that an additional number of shares will automatically be added to the shares reserved for issuance on the first day of each fiscal year, beginning with the fiscal year ending December 31, 2022 and continuing for each fiscal year until, and including, the fiscal year ending on December 31, 2032. The number of shares added each year will be equal to the lowest of (i) 488,000 shares of common stock, (ii) 1% of the number of shares of outstanding common stock on such date, and (iii) such amount as determined by the board of directors. The Company had not initiated any offering periods under the 2021 ESPP as of December 31, 2021.

Stock-Based Compensation Expense

Total stock-based compensation expense recognized in the consolidated statements of operations for the years ended December 31, 2021 and 2020 was as follows (in thousands):


	Year Ended December 31,
	2021		2020
Research and development	$	1,524	$	192
General and administrative	2,571		440
Total stock-based compensation	$	4,095	$	632

Restricted Stock Activity

The Company may, at its discretion, repurchase unvested shares of restricted stock issued pursuant to the 2017 Plan at the initial purchase price if the employees or non-employees terminate their service relationship with the Company. The shares are recorded in stockholders’ deficit as they vest.

The following table summarizes restricted stock award activity during the year ended December 31, 2021 (in thousands, except per share amounts):


	Shares/Units	Weighted-Average Grant Date Fair Value Per Share
Unvested at December 31, 2020	562	$	1.54
Granted	—	$	—
Vested	(267)	$	1.87
Forfeited	—	$	—
Unvested at December 31, 2021	295	$	1.35

As of December 31, 2021, there was unrecognized stock-based compensation expense related to unvested restricted stock awards of $0.4 million, which the Company expects to recognize over a weighted-average period of approximately 1.3 years.

The aggregate fair value of restricted stock awards that vested during the years ended December 31, 2021 and 2020, based upon the fair values of the stock underlying the restricted stock awards on the day of vesting, was $3.6 million and $0.6 million, respectively.

Stock Option Activity

The fair value of stock options granted during the years ended December 31, 2021 and 2020 was calculated on the date of grant using the following weighted-average assumptions:


	Year Ended December 31,
	2021		2020
Risk-free interest rate	1.0	%	0.5	%
Expected term (in years)	6.0		6.1
Dividend yield	—	%	—	%
Expected volatility	78.7	%	82.8	%

Using the Black-Scholes option pricing model, the weighted-average grant date fair value of stock options granted during the years ended December 31, 2021 and 2020 was $9.72 and $2.73 per share, respectively.

The following table summarizes stock option activity during the year ended December 31, 2021 (in thousands, except per share amounts):


	Options Outstanding
	Number of Options	Weighted-Average Exercise Price		Weighted-Average Remaining Contractual Life (in years)
Outstanding at December 31, 2020	2,059	$	3.79	9.76
Granted	1,383	$	14.38
Exercised	(82)	$	2.86
Cancelled	(94)	$	5.58
Outstanding, December 31, 2021	3,266	$	8.24	9.02
Exercisable at December 31, 2021	593	$	5.07	8.76

The aggregate intrinsic fair value of stock options exercised during the years ended December 31, 2021 and 2020 was $0.8 million and less than $0.1 million, respectively.

As of December 31, 2021, there was unrecognized stock-based compensation expense related to unvested stock options of $14.8 million, which the Company expects to recognize over a weighted-average period of approximately 2.9 years.

Commitment and Contingencies

12 Months Ended

Dec. 31, 2021

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

Leases

The Company’s leases are as follows:

•An April 2019 operating lease for approximately 9,949 square feet of office and laboratory space which commenced in April 2019 and terminates in March 2024. The lease is subject to fixed-rate rent escalations and provided for a term extension option, which was not reasonably certain of exercise.

•A March 2021 short-term lease for approximately 7,500 square feet of office and laboratory space which commenced in April 2021 and terminates in May 2022. The Company did not recognize an operating lease right of use asset or a lease liability upon lease commencement. Rent expense for our short-term lease is recognized as incurred.

•A June 2021 operating lease for approximately 25,778 square feet of office and laboratory space which is targeted for occupancy in April 2022 and terminates in April 2030. The lease is subject to fixed-rate rent escalations and provided for $5.7 million in tenant improvements and a term extension option, which was not reasonably certain of exercise. The Company provided the landlord with a security deposit in the form of a letter of credit in the amount of $1.0 million upon signing, which is included in restricted cash as of December 31, 2021.

Accounting under ASC 842:

•Expected lease term: The expected lease term includes noncancelable lease periods and, when applicable, periods covered by an option to extend the lease if the Company is reasonably certain to exercise that option, as well as periods covered by an option to terminate the lease if the Company is reasonably certain not to exercise that option.

•Incremental borrowing rate: As the discount rates in the Company’s lease are not implicit, management estimated the incremental borrowing rate based on the rate of interest the Company would have to pay to borrow a similar amount on a collateralized basis over a similar term.

•Lease and non-lease components: The Company is required to pay fees for operating expenses in addition to monthly base rent for certain operating leases (non-lease components). The Company has elected the practical expedient which allows non-lease components to be combined with lease components for all asset classes. Variable non-lease components are not included within the lease right-of-use asset and lease liability on the consolidated balance sheet, and instead are reflected as expense in the period they are paid.

The following table summarizes operating lease costs (in thousands):


	Year Ended December 31,
	2021		2020
Operating lease costs	$	1,312	$	877
Variable lease costs	398		208
Short-term lease costs	411		—
Total	$	2,121	$	1,085

The following table summarizes the lease term and discount rate for operating leases:


	As of December 31,
	2021		2020
Weighted-average remaining lease term (years)	7.6		3.3
Weighted-average discount rate	8.1	%	9.3	%

As of December 31, 2021, the future minimum lease payments due under the Company’s leases are as follows (in thousands):


	Amount
2022	$	2,494
2023	3,138
2024	2,511
2025	2,343
2026	2,409
Thereafter	8,527
Total remaining minimum rental payments	21,422
Less: effect of discounting	(5,761)
Total lease liability	$	15,661

License Agreements

Harpoon License

In March 2018, the Company entered into a Patent Assignment and License Agreement (the “Harpoon Agreement”) with Harpoon Therapeutics, Inc. (“Harpoon”), a clinical-stage immune-oncology company developing a novel class of T-cell engagers to fight cancer and other diseases. Under the terms of the Harpoon Agreement, Harpoon granted the Company a license to use its intellectual property, solely to make, have made, use, sell, offer for sale and import covered products in the licensed field and Harpoon sold, assigned and transferred other specific patents to the Company (the “Harpoon License”).

On October 19, 2018, the Company and Harpoon entered into the First Amended and Restated Assignment and License Agreement which amended certain terms of the original agreement, but did not change the terms of the license to the Company, patent assignments between the parties or payments due to Harpoon. Further, on December 20, 2019, the companies entered into the Second Amended and Restated Assignment and License Agreement, which also amended certain terms of the original agreement to expand the licenses and assignments for specific patents granted to the Company or by the Company to Harpoon. In exchange for these additional terms, Harpoon agreed to reimburse up to $75,000 of the Company’s legal costs. Additionally, the Company agreed to pay to Harpoon royalties on future net sales and pay minimum annual royalties of $250,000 upon achievement of its first commercial sale.

Under the terms of the Harpoon License, the Company paid an upfront fee of $500,000 in 2018 and is obligated to reimburse Harpoon for certain legal costs incurred by Harpoon. In addition, the Company is obligated to pay Harpoon royalties based on future net sales and has agreed to pay a minimum annual royalty payment at an amount in the low hundreds of thousands of dollars upon achievement of its first commercial sale. In 2018, the Company recorded the upfront fee as research and development expense upon payment as the intellectual property was acquired prior to regulatory approval and does not have an alternative future use. The royalty payments are contingent upon sales and, as such, the royalty payments made to Harpoon will be considered probable and estimable and treated as cost of sales when incurred. Accordingly, at the commencement of sales, the Company will account for the royalty payments as cost of sales equal to the greater of a percentage in the low-single digits of the net sales of the patent-covered products or a minimum annual royalty payment at an amount in the low hundreds of thousands of dollars. Any legal fees incurred in connection with the Harpoon Agreement will be expensed as incurred.

The Harpoon License will expire on a country-by-country basis upon the expiration of the last to expire patent or patent application included in the licensed patents within the applicable country. The Company has the right to terminate the Harpoon License upon 30 days prior written notice to Harpoon, and either party may terminate for a material breach if such breach is not cured within a specified number of days.

Adimab License

In March 2018, the Company entered into a Development and Option Agreement (the “Adimab Agreement”) with Adimab LLC (“Adimab”), a company specializing in antibody discovery, humanization and optimization. Under the terms of the Adimab Agreement, Adimab granted the Company the rights to initiate certain research initiatives on a specified number of targets. Adimab also granted to the Company a license to certain Adimab core technologies, antibodies and products applicable to certain targets (“Adimab License”).

In August 2020, the Company and Adimab entered into Amendment One to the Development and Option Agreement, which extended the period of time for the Company to evaluate candidate antibodies in advance of electing to exercise the option to acquire exclusive rights to licensed antibodies (the “Evaluation Term”), but did not otherwise change the terms of the Adimab License. The Evaluation Term was then further extended in December 2020 by entering into Amendment Two to the Development and Option Agreement, through delivery of a non-refundable payment of $100,000 by the Company to Adimab, which was creditable toward the option fee. The non-refundable payment was recorded immediately as research and development expense in the consolidated statements of operations.

Under the terms of the Adimab License, the Company must pay both an upfront fee and final fee of $200,000 for all research programs. The Company must also pay Adimab milestone fees with respect to each research program ranging from $150,000 to $200,000 based on the

achievement of technical milestones by Adimab for the applicable research program. In order to exercise any options in the Adimab Agreement, the Company must pay a $500,000 fee for each target option exercised.

For each target option exercised, the Company is also obligated to pay certain milestones ranging from $1.0 million to $4.0 million for certain clinical and commercialization achievements. Additionally, for licensed products sold during the applicable royalty term, the Company must pay Adimab royalties at percentages in the low-to-mid single digits.

The Adimab Agreement will expire upon the expiration of any options or if an option is exercised, on a country-by-country and licensed product-by-licensed product basis on the expiration of the last royalty term for a licensed product in the particular country. As of December 31, 2021, the Company exercised one target option, but has not recorded any milestone or royalty payments pursuant to the Adimab Agreement.

Clinical Trial Collaboration and Supply Agreement

In August 2021, the Company entered into a Clinical Trial Collaboration and Supply Agreement, or Clinical Supply Agreement, with Merck & Co., Inc., or Merck, to evaluate WTX-124 in combination with KEYTRUDA® (pembrolizumab), Merck’s anti-PD-1 therapy. The planned clinical trial will be conducted by the Company and is designed to evaluate the safety and preliminary efficacy of WTX-124 as a monotherapy and in combination with pembrolizumab in patients with solid tumors. Under the terms of the Clinical Supply Agreement, the Company will sponsor the study and Merck will supply the Company with pembrolizumab in exchange for jointly owning any inventions or discoveries relative to the combined use of WTX-124 and pembrolizumab. Each party is responsible for its own internal costs and expenses to support the trial.

Income Taxes

12 Months Ended

Dec. 31, 2021

Income Tax Disclosure [Abstract]

Income Taxes

During the years ended December 31, 2021 and 2020, the Company recorded no current or deferred income tax expenses or benefits as the Company has incurred losses since inception and has provided a full valuation allowance against its deferred tax assets.

A reconciliation of the expected income tax (benefit) computed using the federal statutory income tax rate to the Company’s effective income tax rate is as follows:


	Year Ended December 31,
	2021		2020
Income tax computed at federal statutory rate	21.0	%	21.0	%
State taxes, net of federal benefit	5.7		9.9
Change in valuation allowance	(27.2)		(42.0)
R&D credit carryovers	1.8		1.7
Interest expense	0.0		0.0
Stock-based compensation	(0.9)		(0.8)
Cancellation of tranche rights	0.0		10.2
Permanent differences	(0.4)		0.0
Effective income tax rate	0.0	%	0.0	%

The Company’s deferred tax assets consist of the following (in thousands):


	As of December 31,
	2021		2020
Deferred tax assets:
Net operating losses	$	22,831	$	10,363
Tax credit carryforwards	1,918		1,021
Lease liability	4,393		731
Capitalized costs—net of amortization	111		124
Reserves and accruals	658		264
Stock-based compensation	500		—

Deferred tax assets	30,411		12,503
Valuation allowance	(26,110)		(11,776)
Deferred tax assets recognized	4,301		727
Deferred tax liabilities:
Right of use asset	(3,762)		(711)
Fixed assets and depreciation	(6)		(12)
Construction in progress	(533)		—
Other	—		(4)
Deferred tax liabilities	(4,301)		(727)
Net deferred tax assets	$	—	$	—

The Company evaluated the positive and negative evidence bearing upon its ability to realize the deferred tax assets as of December 31, 2021 and 2020. Management considered the Company’s cumulative net losses and concluded as of December 31, 2021 and 2020, that it was more likely than not that the Company would not realize the benefits of the deferred tax assets. Accordingly, a full valuation allowance was established against the net deferred tax assets as of December 31, 2021 and 2020. The valuation allowance increased by $14.3 million and $6.7 million for the years ended December 31, 2021 and 2020, respectively, primarily as a result of operating losses generated with no corresponding financial statement benefit.

The Company has incurred net operating losses (“NOL”) since inception. As of December 31, 2021 and 2020, the Company had federal net operating loss carryforwards of $80.3 million and $35.9 million, respectively, available to reduce future federal taxable income. The carryforwards generated in 2017 expire in 2037. $80.2 million of carryforwards generated post 2017 do not expire. The TCJA enacted on December 22, 2017 limits a taxpayer’s ability to utilize NOL deduction in a year to 80% taxable income for federal net operating losses arising in tax years beginning after 2017. The Coronavirus Aid, Relief, and Economic Security Act enacted on March 27, 2020 removes the 80% taxable income limitation for NOL deductions in taxable years beginning prior to January 1, 2021. As of December 31, 2021 and 2020, the Company had state net operating loss carryforwards of $74.5 million and $35.3 million, respectively, available to reduce future state taxable income, which expire at various dates beginning in 2037.

As of December 31, 2021 and 2020, the Company had federal research and development tax credit carryforwards of $1.3 million and $0.6 million, respectively, available to reduce future federal tax liabilities, which expire at various dates beginning in 2038. The Company also had state research and development tax credit carryforwards as of December 31, 2021 and 2020 of $0.6 million and $0.4 million, respectively, available to reduce future state tax liabilities, which expire at various dates beginning in 2033.

Utilization of the Company’s net operating loss carryforwards and research and development tax credit carryforwards may be subject to a substantial annual limitation under Section 382 of the Internal Revenue Code of 1986 due to ownership changes that have occurred previously or that could occur in the future. These ownership changes may limit the amount of carryforwards that can be utilized annually to offset future taxable income. In general, an ownership change, as defined by Section 382, results from transactions increasing the ownership of certain stockholders or public groups in the stock of a corporation by more than 50% over a three-year period. The Company is in the process of performing a Section 382 study to assess whether a change of control has occurred or whether there have been multiple changes of control since inception. If the Company has experienced a change of control, as defined by Section 382, at any time since inception, utilization of the net operating loss carryforwards or research and development tax credit carryforwards would be subject to an annual limitation under Section 382, which is determined by first multiplying the value of the Company’s stock at the time of the ownership change by the applicable long-term tax-exempt rate, and then could be subject to additional adjustments, as required. Any limitation may result in expiration of a portion of the net operating loss carryforwards or research and development tax credit carryforwards before utilization. Further, until the Section 382 study is completed, and any limitation is known, no amounts are being presented as an uncertain tax position.

The Company has not recorded any reserves for uncertain tax positions as of December 31, 2021 and 2020. The Company has conducted a study of research and development tax credit. The amounts of federal and state research and development tax credit carryforwards presented above have reflected the results from the study. A full valuation allowance has been provided against the Company’s research and development credits.

The Company files tax returns as prescribed by the tax laws of the jurisdictions in which it operates. In the normal course of business, the Company is subject to examination by federal and state jurisdictions, where applicable. There are currently no pending tax examinations. The Company’s tax years are still open under statute from inception to the present.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 21
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32857-109319

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 11.C)
-URI http://asc.fasb.org/extlink&oid=122134291&loc=d3e330215-122817

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 17
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32809-109319

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I.5.Q1)
-URI http://asc.fasb.org/extlink&oid=122134291&loc=d3e330036-122817

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 14
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32705-109319

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 270
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6424409&loc=d3e44925-109338

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-URI http://asc.fasb.org/topic&trid=2144680

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6424122&loc=d3e41874-109331

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(2))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

+ Details

Related Parties	12 Months Ended
Related Parties	Dec. 31, 2021
Related Party Transactions [Abstract]
Related Parties	Related Parties During the year ended December 31, 2020, the Company recorded $31,000 of general and administrative expense in the accompanying consolidated statements of operations related to management services provided by MPM Capital. Additionally, as of December 31, 2020, the Company recorded $8,000 in accounts payable in the accompanying consolidated balance sheets related to the provision of management services by MPM Capital. The Company did not incur any expense with MPM Capital for the year ended December 31, 2021. In December 2019, the Company entered into a consulting agreement with Briggs Morrison, M.D., a member of the Company’s board of directors, for the provision of consulting, advisory and related services. Pursuant to the consulting agreement, in December 2019, the Company issued Dr. Morrison a stock option grant for 46,570 shares of common stock at an aggregate grant date fair value of $50,000, and agreed to reimburse certain of Dr. Morrison’s expenses in connection with the performance of services under the agreement. The stock options have an exercise price of $1.56 per share and are scheduled to vest with respect to 2.0833% of the shares underlying the grant in equal monthly installments over four years following November 2019, subject to continuous service. The Company recognized $13,000 of expense related to this award in the research and development line in the consolidated statements of operations for each of the years ended December 31, 2021 and 2020.

401(k) Savings Plan	12 Months Ended
401(k) Savings Plan	Dec. 31, 2021
Retirement Benefits [Abstract]
401(k) Savings Plan	401(k) Savings PlanThe Company has a defined-contribution savings plan under Section 401(k) of the Internal Revenue Code (the "401(k) Plan"). 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. As currently established, the Company is not required to make and has not made any contributions to the 401(k) Plan to date.

Net Loss Attributable to Common Stockholders per Share

12 Months Ended

Dec. 31, 2021

Earnings Per Share [Abstract]

Net Loss Attributable to Common Stockholders per Share

Net Loss Attributable to Common Stockholders per ShareFor purposes of the diluted net loss attributable to common stockholders per share calculation, redeemable convertible preferred stock, outstanding stock options, unvested restricted stock awards and warrants to purchase common stock are considered to be potentially dilutive

securities, however the following weighted-average amounts were excluded from the calculation of diluted net loss attributable to common stockholders per share because their effect would be anti-dilutive (in thousands):


	December 31,
	2021	2020
Redeemable convertible preferred stock (as converted)	—	18,280
Outstanding stock options	3,266	2,059
Unvested restricted common stock	295	562
Warrants to purchase common stock	59	59
Total	3,620	20,960

Basis of Presentation and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation and ConsolidationThe accompanying consolidated financial statements have been prepared in accordance with the rules and regulations of the Securities and Exchange Commission (the “SEC”) and generally accepted accounting principles in the United States of America (“GAAP”) as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Updates (“ASU”) of the Financial Accounting Standards Board (“FASB”).
Consolidation	The accompanying consolidated financial statements include the accounts of Werewolf Therapeutics, Inc. and its wholly-owned subsidiary, Werewolf Therapeutics Mass Securities, Inc. All intercompany transactions and balances have been eliminated in consolidation.
Segment Information	Segment Information Operating segments are identified as components of an enterprise for which separate discrete financial information is available for evaluation by the Company’s Chief Operating Decision Maker (“CODM”) to make decisions with respect to resource allocation and assessment of performance. The CODM is the Company’s Chief Executive Officer. The CODM manages the Company’s operations as a single segment for the purposes of assessing performance and making operating decisions. The Company’s singular concentration is focused on the discovery and development of cancer therapeutics by advancing a novel class of conditionally activated proinflammatory immune modulators.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. On an ongoing basis, the Company’s management evaluates its estimates which include, but are not limited to, the fair values of common stock and redeemable convertible preferred stock and the fair value of the preferred stock tranche rights. Actual results could differ from those estimates.
Fair Value of Financial Instruments	Fair Value of Financial Instruments ASU No. 2018-13, Fair Value Measurement (Topic 820): Disclosure for Fair Value Measurement (“ASC 820”), establishes a fair value hierarchy for instruments measured at fair value that distinguishes between assumptions based on market data (observable inputs) and the Company’s own assumptions (unobservable inputs). Observable inputs are inputs that market participants would use in pricing the asset or liability based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the inputs that market participants would use in pricing the asset or liability and are developed based on the best information available in the circumstances. ASC 820 identifies fair value as the exchange price, or exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As a basis for considering market participant assumptions in fair value measurements, ASC 820 establishes a three-tier fair value hierarchy that distinguishes between the following: •Level 1 inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities. •Level 2 inputs are inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly. •Level 3 inputs are unobservable inputs that reflect the Company’s own assumptions about the assumptions market participants would use in pricing the asset or liability. Financial assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company’s cash and cash equivalents consist of cash maintained within a standard checking account. The Company also maintains a cash sweep account in which cash from its main operating cash account is invested overnight in highly liquid, short-term investments. The Company considers all highly liquid investments with a maturity date of 90 days or less at the date of purchase to be cash equivalents.
Property and Equipment	Property and Equipment Property and equipment is recorded at cost and consists of laboratory equipment, furniture and office equipment, computer equipment, and leasehold improvements. The Company capitalizes property and equipment that is acquired for research and development activities and that has alternate future use. Expenditures for maintenance and repairs are recorded to expense as incurred, whereas major betterments are capitalized as additions to property and equipment. Leasehold improvements are depreciated over the lesser of their useful life or the term of the lease. Depreciation is calculated over the estimated useful lives of the assets using the straight-line method.
Impairment of Long-lived Assets	Impairment of Long-lived Assets Long-lived assets consist of property and equipment. The Company reviews its property and equipment whenever events or changes in circumstances indicate that the carrying value of certain assets might not be recoverable and recognizes an impairment loss when it is probable that an asset’s realizable value is less than the carrying value.
Leases	Leases At the inception of an arrangement, the Company determines whether the arrangement is or contains a lease based on the unique facts and circumstances present in the arrangement. Leases with a term greater than one year are recognized on the balance sheet as right-of-use assets and short-term and long-term lease liabilities, as applicable. The Company does not recognize leases with terms of one year or less on the balance sheet. Options to renew a lease are not included in the Company’s initial lease term assessment unless there is reasonable certainty that the Company will renew. The Company monitors its plans to renew its material leases on a quarterly basis. Operating lease liabilities and their corresponding right-of-use assets are recorded based on the present value of lease payments over the expected remaining lease term. Certain adjustments to the right-of-use asset may be required for items such as incentives received. The interest rate implicit in lease contracts is typically not readily determinable. As a result, the Company utilizes its incremental borrowing rate (“IBR”), which reflects the fixed rate at which the Company could borrow on a collateralized basis the amount of the lease payments in the same currency, for a similar term, and in a similar economic environment. The Company subsequently measures its lease liability at the present value of remaining lease payments, discounted using the IBR for the lease. The right-of-use asset is subsequently measured at the amount of the lease liability, adjusted for prepaid or accrued lease payments and the remaining balance of lease incentives received. The Company recognizes operating lease expense on a straight-line basis over the lease term.
Revenue Recognition	Revenue Recognition The Company analyzes its collaborations to assess whether such arrangements involve joint operating activities performed by parties that are both active participants in the activities and exposed to significant risks and rewards dependent on the commercial success of such activities and therefore within the scope of ASC Topic 808, Collaborative Arrangements (“ASC 808”). This assessment is performed throughout the life of the arrangement based on changes in the responsibilities of all parties in the arrangement. For arrangements within the scope of ASC 808 that contain multiple elements, the Company first determines which elements of the collaboration are deemed to be within the scope of ASC 808 and which elements of the collaboration are more reflective of a vendor-customer relationship and therefore within the scope of ASC Topic 606, Revenue from Contracts with Customers (“ASC 606”). For elements of collaboration arrangements that are accounted for pursuant to Topic 808, an appropriate recognition method is determined and applied consistently, either by analogy to authoritative accounting literature or by applying a reasonable and rational policy election. For those elements of the arrangement that are accounted for pursuant to ASC 606, the Company recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration that the entity expects to receive in exchange for those goods or services. In applying ASC 606, the Company performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the promises and performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the Company satisfies the performance obligations. The Company only applies the five-step model to contracts when it is probable that it will collect the consideration to which it is entitled 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, 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 assessment, the Company must develop assumptions that require judgment to determine the standalone selling price for each performance obligation identified in the contract. The Company uses key assumptions to determine the standalone selling price, which may include reimbursement rates for personnel costs, development timelines and probabilities of regulatory success. The Company does not assess whether a contract has a significant financing component if the expectation at contract inception is that the period between payment by the customer and the transfer of promised goods or services to the customer will be one year or less. Arrangements that include upfront payments may require deferral of revenue recognition to a future period until obligations under these arrangements are fulfilled. The event-based milestone payments represent variable consideration, and the Company uses the “most likely amount” method to estimate this variable consideration. Given the high degree of uncertainty around the occurrence of these events, the Company determined the milestone and other contingent amounts to be fully constrained until the uncertainty associated with these payments is resolved. Revenue will be recognized from sales-based royalty payments when or as the sales occur. The Company will re-evaluate the transaction price in each reporting period as uncertain events are resolved and other changes in circumstances occur.
Research and Development Expenses	Research and Development Expenses Expenditures relating to research and development are expensed as incurred. Research and development expenses include external expenses incurred under arrangements with third parties, academic and non-profit institutions and consultants; salaries and personnel-related costs, including non-cash stock-based compensation expense; license fees to acquire in-process technology and other expenses, which include direct and allocated expenses for laboratory, facilities and other costs. Non‑refundable advance payments for goods and services that will be used in future research and development activities are expensed when the activity has been performed or when the goods have been received rather than when the payment is made. As part of the process of preparing the consolidated financial statements, the Company is required to estimate its accrued research and development expenses as of each balance sheet date. 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. This process involves reviewing open contracts and purchase orders, communicating with internal personnel to identify services that have been performed on the Company’s behalf and estimating the level of service performed and the associated cost incurred for the service when the Company has not yet been invoiced or otherwise notified of the actual cost. The Company periodically confirms the accuracy of its estimates with its service providers and makes adjustments if necessary. The majority of the Company’s service providers invoice monthly in arrears for services performed or when contractual milestones are met. The financial terms of agreements with these service providers are subject to negotiation, vary from contract to contract and may result in uneven payment flows. In circumstances where amounts have been paid in excess of costs incurred, the Company records a prepaid expense.
Intellectual Property Expenses	Intellectual Property Expenses The Company expenses costs associated with intellectual property-related matters as incurred and classifies such costs as general and administrative expenses within the consolidated statements of operations.
Stock-based Compensation	Stock-based Compensation The Company accounts for stock-based payments in accordance with ASU No. 2018-07, Compensation—Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting (“ASC 718”). This guidance requires all stock-based payments to employees, including grants of employee stock options and restricted stock awards (“RSAs”), to be recognized as expense in the consolidated statements of operations and comprehensive (loss) income based on their grant date fair values. For stock options granted to employees and to members of the Company’s board of directors for their services on the board of directors, the Company estimates the grant date fair value of each stock option using the Black-Scholes option-pricing model. For restricted stock units (“RSUs”) and RSAs granted to employees, the Company estimates the grant date fair value of each award using intrinsic value, which is based on the value of the underlying common stock less any purchase price. For stock-based payments subject to service-based vesting conditions, the Company recognizes stock-based compensation expense equal to the grant date fair value of stock-based payment on a straight-line basis over the requisite service period. The Black‑Scholes option pricing model requires the input of certain subjective assumptions, including (i) the calculation of expected term of the stock-based payment, (ii) the risk‑free interest rate, (iii) the expected stock price volatility and (iv) the expected dividend yield. The Company uses the simplified method as proscribed by SEC Staff Accounting Bulletin No. 107 to calculate the expected term for stock options granted to employees as the Company does not have sufficient historical exercise data to provide a reasonable basis upon which to estimate the expected term. The Company determines the risk‑free interest rate based on a treasury instrument whose term is consistent with the expected term of the stock options. Because there had been no public market for the Company’s common stock prior to the Company’s IPO, there is a lack of Company‑specific historical and implied volatility data. Accordingly, the Company bases its estimates of expected volatility on the historical volatility of a group of publicly-traded companies with similar characteristics to itself, including stage of product development and therapeutic focus within the life sciences industry. Historical volatility is calculated over a period of time commensurate with the expected term of the stock-based payment. The Company uses an assumed dividend yield of zero as the Company has never paid dividends on its common stock, nor does it expect to pay dividends on its common stock in the foreseeable future. The Company accounts for forfeitures of all stock-based payments when such forfeitures occur.
Income Taxes	Income Taxes Income taxes are recorded in accordance with ASU No. 2019-12, Income Taxes (Topic 740) (“ASC 740”) which provides for deferred taxes using an asset and liability approach. The Company recognizes deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the consolidated financial statements or tax returns. Deferred tax assets and liabilities are determined based on the difference between the financial statement and tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. A valuation allowance against deferred tax assets is recorded if, based on the weight of the available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized. The Company accounts for uncertain tax positions using a more-likely-than-not threshold for recognizing and resolving uncertain tax positions. The evaluation of uncertain tax positions is based on factors, including, but not limited to, changes in the law, the measurement of tax positions taken or expected to be taken in tax returns, the effective settlement of matters subject to audit, new audit activity and changes in facts or circumstances related to a tax position.
Comprehensive Loss	Comprehensive Loss The Company does not have items of other comprehensive loss for the years ended December 31, 2021 and 2020, and therefore does not present a consolidated statement of comprehensive loss. The Company’s comprehensive loss equals its net loss.
Net Loss per Common Share	Net Loss per Common Share Basic net loss per share is computed using the “two-class” method, which includes the weighted average number of shares of common stock outstanding during the period and other securities that participate in undistributed earnings (a participating security). The Company’s redeemable convertible preferred stock and restricted stock awards are participating securities as defined by ASU No. 2017-10, Earnings per Share (Topic 260) (“ASC 260-10”). During the periods where the Company incurs net losses, the Company allocates no loss to participating securities because these securities have no contractual obligation to share in the losses of the Company. Under the two-class method, basic net loss per share applicable to common stockholders is computed by dividing the net loss applicable to common stockholders by the weighted average number of common shares outstanding for the period. Diluted net loss per share is computed similar to basic net loss per share except that the denominator is increased to include the number of additional shares for the potential dilutive effects of warrants, redeemable convertible preferred stock and stock options outstanding during the period calculated in accordance with the treasury stock method, or the two-class method, whichever is more dilutive. The Company allocates net earnings on a pari passu (equal) basis to both common and preferred stockholders. Net losses are not allocated to preferred stockholders as they do not have an obligation to share in the Company’s net losses. For all periods presented, basic and diluted net loss per share are the same, as any additional share equivalents would be anti-dilutive.
Concentration of Credit Risk	Concentration of Credit Risk and Off-Balance Sheet RiskFinancial instruments that potentially subject the Company to significant concentrations of credit risk consist of cash and cash equivalents. Cash is held in a checking account at two financial institutions. At times, such deposits may be in excess of insured limits. The Company has not experienced any losses on its deposits of cash and cash equivalents.
Off-Balance Sheet Risk	The Company has no significant off-balance sheet concentrations of credit risk, such as foreign currency exchange contracts, option contracts or other hedging arrangements.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In October 2020, the FASB issued ASU No. 2020-10, Codification Improvements (“ASU 2020-10”), which updates various codification topics by clarifying or improving disclosure requirements to align with the SEC’s regulations. The Company adopted ASU 2020-10 as of the reporting period beginning January 1, 2021 and the adoption did not have material impact on the Company’s consolidated balance sheets, consolidated statements of operations or related disclosures. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments—Credit Losses (Topic 326), Measurement of Credit Losses on Financial Instruments. This guidance amends the impairment model by requiring entities to use a forward-looking approach based on expected losses to estimate credit losses for most financial assets and certain other instruments that aren’t measured at fair value through net income. The Company has adopted the new guidance effective January 1, 2021 and the adoption did not have any material impact on the Company’s consolidated balance sheets, consolidated statements of operations or related disclosures. In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740), Simplifying the Accounting for Income Taxes (“ASU 2019-12”), which is intended to simplify various areas related to accounting for income taxes. ASU 2019-12 removes certain exceptions to the general principles in ASC 740 and also clarifies and amends existing guidance to improve consistent application. For public business entities, the guidance is effective for annual reporting periods beginning after December 15, 2020 and for interim periods within those fiscal years. The Company adopted the standard effective January 1, 2021 and the adoption did not have a material impact on the Company’s consolidated financial statements.
Subsequent Events	Subsequent EventsThe Company has evaluated subsequent events and transactions that occurred after the balance sheet date up to the date that the financial statements were issued. Other than as described in these financial statements, the Company did not identify any subsequent events that would have required adjustment to or disclosure in the financial statements

Financial Instruments and Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2021

Fair Value Disclosures [Abstract]

Assets Measured at Fair Value on a Recurring Basis

Assets measured at fair value on a recurring basis as of December 31, 2021 were as follows (in thousands):


	Quoted Price in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Total
Assets:
Money market funds	$	157,531	$	—	$	—	$	157,531
Total assets	$	157,531	$	—	$	—	$	157,531

Assets measured at fair value on a recurring basis as of December 31, 2020 were as follows (in thousands):


	Quoted Price in Active Markets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Total
Assets:
Money market funds	$	92,570	$	—	$	—	$	92,570
Total assets	$	92,570	$	—	$	—	$	92,570

- Definition

Tabular disclosure of financial instruments measured at fair value, including those classified in shareholders' equity measured on a recurring or nonrecurring basis. Disclosures include, but are not limited to, fair value measurements recorded and the reasons for the measurements, level within the fair value hierarchy in which the fair value measurements are categorized and transfers between levels 1 and 2. Nonrecurring fair value measurements are those that are required or permitted in the statement of financial position in particular circumstances.

+ References + Details

Property and Equipment, Net (Tables)

12 Months Ended

Dec. 31, 2021

Property, Plant and Equipment [Abstract]

Schedule of Property, Plant and Equipment

Property and equipment, net as of December 31, 2021 and 2020 was comprised as follows (in thousands):


		December 31,
	Estimated Useful Life (in years)	2021		2020
Laboratory equipment	5	$	839	$	606
Furniture and office equipment	5	9		13
Computer equipment	3	221		19
Leasehold improvements	Shorter of 7 years or remaining lease term	274		188
Construction in progress		1,961		—
Total property and equipment, gross		3,304		826
Less: accumulated depreciation		(391)		(175)
Total property and equipment, net		$	2,913	$	651

Accrued Expenses and Other Current Liabilities (Tables)

12 Months Ended

Dec. 31, 2021

Payables and Accruals [Abstract]

Accrued Expenses

Accrued expenses and other current liabilities as of December 31, 2021 and 2020 were comprised as follows (in thousands):


	December 31,
	2021		2020
Manufacturing	$	3,427	$	1,741
Employee compensation and benefits	2,200		990
Professional fees	433		654
Contract research	2,542		107
Other	163		94
Total accrued expenses and other current liabilities	$	8,765	$	3,586

Common and Preferred Stock (Tables)

12 Months Ended

Dec. 31, 2021

Equity [Abstract]

Schedule of Common Stock Reserved for Issuance

The Company had reserved shares of common stock for issuance as follows (in thousands):


	As of December 31,
	2021	2020
Redeemable convertible preferred stock outstanding	—	18,280
Options issued and outstanding	3,266	2,059
Warrants issued and outstanding	59	59
Total	3,325	20,398

Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2021

Share-based Payment Arrangement [Abstract]

Stock-based Compensation Expense Recognized

Total stock-based compensation expense recognized in the consolidated statements of operations for the years ended December 31, 2021 and 2020 was as follows (in thousands):


	Year Ended December 31,
	2021		2020
Research and development	$	1,524	$	192
General and administrative	2,571		440
Total stock-based compensation	$	4,095	$	632

Restricted Stock Awards Activity

The following table summarizes restricted stock award activity during the year ended December 31, 2021 (in thousands, except per share amounts):


	Shares/Units	Weighted-Average Grant Date Fair Value Per Share
Unvested at December 31, 2020	562	$	1.54
Granted	—	$	—
Vested	(267)	$	1.87
Forfeited	—	$	—
Unvested at December 31, 2021	295	$	1.35

Weighted -average Valuation Assumptions

The fair value of stock options granted during the years ended December 31, 2021 and 2020 was calculated on the date of grant using the following weighted-average assumptions:


	Year Ended December 31,
	2021		2020
Risk-free interest rate	1.0	%	0.5	%
Expected term (in years)	6.0		6.1
Dividend yield	—	%	—	%
Expected volatility	78.7	%	82.8	%

Summary of Stock Option Activity

The following table summarizes stock option activity during the year ended December 31, 2021 (in thousands, except per share amounts):


	Options Outstanding
	Number of Options	Weighted-Average Exercise Price		Weighted-Average Remaining Contractual Life (in years)
Outstanding at December 31, 2020	2,059	$	3.79	9.76
Granted	1,383	$	14.38
Exercised	(82)	$	2.86
Cancelled	(94)	$	5.58
Outstanding, December 31, 2021	3,266	$	8.24	9.02
Exercisable at December 31, 2021	593	$	5.07	8.76

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2021

Commitments and Contingencies Disclosure [Abstract]

Summary of Operating Lease Costs

The following table summarizes operating lease costs (in thousands):


	Year Ended December 31,
	2021		2020
Operating lease costs	$	1,312	$	877
Variable lease costs	398		208
Short-term lease costs	411		—
Total	$	2,121	$	1,085

The following table summarizes the lease term and discount rate for operating leases:


	As of December 31,
	2021		2020
Weighted-average remaining lease term (years)	7.6		3.3
Weighted-average discount rate	8.1	%	9.3	%

Future Minimum Lease Payments

As of December 31, 2021, the future minimum lease payments due under the Company’s leases are as follows (in thousands):


	Amount
2022	$	2,494
2023	3,138
2024	2,511
2025	2,343
2026	2,409
Thereafter	8,527
Total remaining minimum rental payments	21,422
Less: effect of discounting	(5,761)
Total lease liability	$	15,661

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2021

Income Tax Disclosure [Abstract]

Schedule of Effective Income Tax Rate Reconciliation

A reconciliation of the expected income tax (benefit) computed using the federal statutory income tax rate to the Company’s effective income tax rate is as follows:


	Year Ended December 31,
	2021		2020
Income tax computed at federal statutory rate	21.0	%	21.0	%
State taxes, net of federal benefit	5.7		9.9
Change in valuation allowance	(27.2)		(42.0)
R&D credit carryovers	1.8		1.7
Interest expense	0.0		0.0
Stock-based compensation	(0.9)		(0.8)
Cancellation of tranche rights	0.0		10.2
Permanent differences	(0.4)		0.0
Effective income tax rate	0.0	%	0.0	%

Schedule of Deferred Tax Assets and Liabilities

The Company’s deferred tax assets consist of the following (in thousands):


	As of December 31,
	2021		2020
Deferred tax assets:
Net operating losses	$	22,831	$	10,363
Tax credit carryforwards	1,918		1,021
Lease liability	4,393		731
Capitalized costs—net of amortization	111		124
Reserves and accruals	658		264
Stock-based compensation	500		—

Deferred tax assets	30,411		12,503
Valuation allowance	(26,110)		(11,776)
Deferred tax assets recognized	4,301		727
Deferred tax liabilities:
Right of use asset	(3,762)		(711)
Fixed assets and depreciation	(6)		(12)
Construction in progress	(533)		—
Other	—		(4)
Deferred tax liabilities	(4,301)		(727)
Net deferred tax assets	$	—	$	—

Net Loss Attributable to Common Stockholders per Share (Tables)

12 Months Ended

Dec. 31, 2021

Earnings Per Share [Abstract]

Schedule of Antidilutive Securities Excluded from Computation of (Loss) Income per Share

For purposes of the diluted net loss attributable to common stockholders per share calculation, redeemable convertible preferred stock, outstanding stock options, unvested restricted stock awards and warrants to purchase common stock are considered to be potentially dilutive


	December 31,
	2021	2020
Redeemable convertible preferred stock (as converted)	—	18,280
Outstanding stock options	3,266	2,059
Unvested restricted common stock	295	562
Warrants to purchase common stock	59	59
Total	3,620	20,960

Nature of Business (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	May 04, 2021	Dec. 31, 2021	Dec. 31, 2020
Subsidiary, Sale of Stock [Line Items]
Proceeds from initial public offering of common stock		$ 111,600	$ 0
Cash and cash equivalents		$ 157,531	$ 92,570
Common Stock
Subsidiary, Sale of Stock [Line Items]
Aggregate shares converted (shares)		18,280,000
IPO
Subsidiary, Sale of Stock [Line Items]
Proceeds from initial public offering of common stock	$ 120,000
Net proceeds from the IPO	$ 109,200
Aggregate shares converted (shares)	18,279,712
IPO \| Common Stock
Subsidiary, Sale of Stock [Line Items]
Shares issued in IPO (shares)	7,500,000
Price per share (in usd per share)	$ 16.00
Aggregate shares converted (shares)	18,300,000

Basis of Presentation and Summary of Significant Accounting Policies (Details)	12 Months Ended
	Dec. 31, 2021 institution
Accounting Policies [Abstract]
Expected dividend yield	0.00%
Number of financial institutions	2

Financial Instruments and Fair Value Measurements (Details) - USD ($)	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 30, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Redeemable convertible preferred stock issued (shares)			48,675,140
Preferred stock tranche liability			$ 7,300,000	$ 7,800,000
Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	$ 157,531,000	$ 92,570,000
Liabilities measured at fair value on recurring basis	0	0
Money market funds \| Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Money market funds	157,531,000	92,570,000
Quoted Price in Active Markets (Level 1) \| Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	157,531,000	92,570,000
Quoted Price in Active Markets (Level 1) \| Money market funds \| Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Money market funds	157,531,000	92,570,000
Significant Other Observable Inputs (Level 2) \| Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	0	0
Significant Other Observable Inputs (Level 2) \| Money market funds \| Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Money market funds	0	0
Significant Unobservable Inputs (Level 3) \| Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	0	0
Significant Unobservable Inputs (Level 3) \| Money market funds \| Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Money market funds	$ 0	$ 0

Restricted Cash (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Cash and Cash Equivalents [Abstract]
Non-current restricted cash	$ 1.3	$ 0.2
Restricted cash included in "Prepaid expenses and other current assets"	$ 0.1

Property and Equipment, Net - Schedule of Property, Plant and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	$ 3,304	$ 826
Less: accumulated depreciation	(391)	(175)
Total property and equipment, net	$ 2,913	651
Laboratory equipment
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	5 years
Total property, plant and equipment, gross	$ 839	606
Furniture and office equipment
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	5 years
Total property, plant and equipment, gross	$ 9	13
Computer equipment
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	3 years
Total property, plant and equipment, gross	$ 221	19
Leasehold improvements
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	7 years
Total property, plant and equipment, gross	$ 274	188
Construction in progress
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, gross	$ 1,961	$ 0

Property and Equipment, Net - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 216	$ 150

Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Payables and Accruals [Abstract]
Manufacturing	$ 3,427	$ 1,741
Employee compensation and benefits	2,200	990
Professional fees	433	654
Contract research	2,542	107
Other	163	94
Total accrued expenses and other current liabilities	$ 8,765	$ 3,586

Term Loan (Details) - Term loan - USD ($)	1 Months Ended	11 Months Ended
Term Loan (Details) - Term loan - USD ($)	May 31, 2020	Nov. 29, 2021	Feb. 28, 2021
Term Loan A
Debt Instrument [Line Items]
Term loan available	$ 6,000,000
Delayed draw fee	25,000
Term Loan B
Debt Instrument [Line Items]
Term loan available	$ 8,000,000
Term Loans
Debt Instrument [Line Items]
Floating rate spread in effect (greater than) (percent)	5.00%
Success Fee (percent)	5.00%
Success Fee survival term	10 years
Default payment fee (percent)	5.00%
Unrestricted cash balance ratio to monthly cash burn	2.5
Maximum annual capital expenditures	$ 400,000
Drawings on Term Loans		$ 0
Term Loans \| In FY 2021
Debt Instrument [Line Items]
Maximum annual capital expenditures			$ 2,000,000
Term Loans \| After FY 2021
Debt Instrument [Line Items]
Maximum annual capital expenditures			$ 500,000
Term Loans \| Prime Rate
Debt Instrument [Line Items]
Floating rate spread in effect (greater than) (percent)	1.75%

Common and Preferred Stock (Details) - USD ($) $ / shares in Units, $ in Thousands			12 Months Ended		36 Months Ended
	May 04, 2021	Jun. 01, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2021	Dec. 31, 2019	Dec. 30, 2019
Class of Stock [Line Items]
Common stock authorized (shares)			200,000,000	193,500,000	200,000,000
Common stock available for issuance (shares)			3,325,000	20,398,000	3,325,000
Issuance costs			$ 2,378	$ 184
Convertible notes exchanged upon issuance of preferred stock shares			$ 293,024
Preferred stock tranche liability						$ 7,300	$ 7,800
Preferred stock authorized (shares)			5,000,000	0	5,000,000
Preferred stock issued (shares)			0	0	0
Preferred stock outstanding (shares)			0	0	0
Common Stock
Class of Stock [Line Items]
Aggregate shares converted (shares)			18,280,000
IPO
Class of Stock [Line Items]
Aggregate shares converted (shares)	18,279,712
IPO \| Common Stock
Class of Stock [Line Items]
Aggregate shares converted (shares)	18,300,000
Price per share (in usd per share)	$ 16.00
Additional shares issued in IPO (shares)	7,500,000
Redeemable convertible preferred stock outstanding
Class of Stock [Line Items]
Common stock available for issuance (shares)			0	18,280,000	0
Options issued and outstanding
Class of Stock [Line Items]
Common stock available for issuance (shares)			3,266,000	2,059,000	3,266,000
Warrants issued and outstanding
Class of Stock [Line Items]
Common stock available for issuance (shares)			59,000	59,000	59,000
Series A Preferred Stock
Class of Stock [Line Items]
Price per share (in usd per share)			$ 0.70		$ 0.70
Series A Preferred Stock \| IPO
Class of Stock [Line Items]
Price per share (in usd per share)				$ 0.70
Proceeds from issuance of preferred stock					$ 44,000
Issuance costs					200
Convertible notes exchanged upon issuance of preferred stock shares					$ 12,000
Series A Redeemable Convertible Preferred Stock \| Second Closing
Class of Stock [Line Items]
Additional shares issued in IPO (shares)		31,571,425
Purchase price per share (in usd per share)		$ 0.70
Preferred stock tranche liability		$ 7,800
Series B Preferred Stock
Class of Stock [Line Items]
Price per share (in usd per share)			0.92		$ 0.92
Series B Preferred Stock \| IPO
Class of Stock [Line Items]
Price per share (in usd per share)			$ 0.92		$ 0.92
Proceeds from issuance of preferred stock					$ 71,800
Issuance costs					$ 300

Stock-based Compensation - Narrative (Details) $ / shares in Units, $ in Millions		12 Months Ended
	Apr. 30, 2021 shares	Dec. 31, 2021 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) $ / shares shares
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Common stock available for issuance (shares)		3,325,000	20,398,000
Share-based compensation expense not yet recognized \| $		$ 14.8
2021 Stock Incentive Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Maximum number of shares to be added annually, as a percentage of outstanding shares (percent)	0.05
2017 Stock Incentive Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Common stock available for issuance (shares)		1,938,895
Common Stock
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Common stock authorized to be issued (shares)	3,352,725
Common Stock \| 2021 Stock Incentive Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Common stock authorized to be issued (shares)	2,843,116
Common Stock \| 2017 Stock Incentive Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Common stock authorized to be issued (shares)	31,884
Unvested restricted common stock
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-based compensation expense not yet recognized \| $		$ 0.4
Share-based compensation not yet recognized, recognition period		1 year 3 months 18 days
Aggregate fair value of awards that vested \| $		$ 3.6	$ 0.6
Unvested restricted common stock \| 2021 Stock Incentive Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Common stock authorized to be issued (shares)	477,725
Employee stock \| 2021 Stock Employee Stock Purchase Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Common stock authorized to be issued (shares)	244,000
Maximum number of shares to be added annually, as a percentage of outstanding shares (percent)	0.01
Employee stock \| 2021 Stock Employee Stock Purchase Plan \| Minimum
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Maximum number of shares to be added annually, as a percentage of outstanding shares (shares)	488,000
Stock options
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-based compensation not yet recognized, recognition period		2 years 10 months 24 days
Weighted-average grant date fair value of awards (in usd per share) \| $ / shares		$ 9.72	$ 2.73
Aggregate intrinsic fair value of options exercised \| $		$ 0.8	$ 0.1

Stock-based Compensation - Expense Recognized (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	$ 4,095	$ 632
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	1,524	192
General and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	$ 2,571	$ 440

Stock-based Compensation - Restricted Stock Award Activity (Details) - Unvested restricted common stock shares in Thousands	12 Months Ended
	Dec. 31, 2021 $ / shares shares
Shares/Units
Unvested at beginning of period (shares) \| shares	562
Granted (shares) \| shares	0
Vested (shares) \| shares	(267)
Forfeited (shares) \| shares	0
Unvested at end of period (shares) \| shares	295
Weighted-Average Grant Date Fair Value Per Share
Weighted Average Grant Date Fair Value - Unvested at beginning of period (in usd per share) \| $ / shares	$ 1.54
Weighted Average Grant Date Fair Value - Granted (in usd per share) \| $ / shares	0
Weighted Average Grant Date Fair Value - Vested (in usd per share) \| $ / shares	1.87
Weighted Average Grant Date Fair Value - Forfeited (in usd per share) \| $ / shares	0
Weighted Average Grant Date Fair Value - Unvested at end of period (in usd per share) \| $ / shares	$ 1.35

Stock-based Compensation - Weighted Average Assumptions (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Dividend yield	0.00%
Stock options
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Risk-free interest rate	1.00%	0.50%
Expected term (in years)	6 years	6 years 1 month 6 days
Dividend yield	0.00%	0.00%
Expected volatility	78.70%	82.80%

Stock-based Compensation - Stock Option Activity (Details) - Stock options - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Number of Options
Outstanding at beginning of period (shares)	2,059
Granted (shares)	1,383
Exercised (shares)	(82)
Cancelled (shares)	(94)
Outstanding at end of period (shares)	3,266	2,059
Exercisable at end of period (shares)	593
Weighted-Average Exercise Price
Weighted-Average Exercise Price - Outstanding at beginning of period (in usd per share)	$ 3.79
Weighted-Average Exercise Price - Granted (in usd per share)	14.38
Weighted-Average Exercise Price - Exercised (in usd per share)	2.86
Weighted-Average Exercise Price - Cancelled (in usd per share)	5.58
Weighted-Average Exercise Price - Outstanding at end of period (in usd per share)	8.24	$ 3.79
Weighted-Average Exercise Price - Exercisable at end of period (in usd per share)	$ 5.07
Weighted-Average Remaining Contractual Life (in years)
Weighted Average Remaining Contractual Life - Outstanding	9 years 7 days	9 years 9 months 3 days
Weighted Average Remaining Contractual Life - Exercisable	8 years 9 months 3 days

Commitments and Contingencies - Narrative (Details) $ in Thousands		1 Months Ended	12 Months Ended			46 Months Ended
	Dec. 20, 2019 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2021 targetOption	Jun. 30, 2021 USD ($) ft²	Mar. 31, 2021 ft²	Apr. 30, 2019 ft²
Loss Contingencies [Line Items]
Research and development			$ 35,269	$ 16,641
Lease commenced in April 2019
Loss Contingencies [Line Items]
Laboratory and office space to be rented (in sqft) \| ft²									9,949
Lease commenced in April 2021
Loss Contingencies [Line Items]
Laboratory and office space to be rented (in sqft) \| ft²								7,500
Lease commencing April 2022
Loss Contingencies [Line Items]
Laboratory and office space to be rented (in sqft) \| ft²							25,778
Tenant improvements							$ 5,700
Security deposit provided							$ 1,000
Harpoon \| Assignment and License Agreement
Loss Contingencies [Line Items]
Reimbursable legal costs	$ 75
Minimum annual royalties	$ 250
Research and development					$ 500
Upfront fee paid					$ 500
License agreement termination, prior written notice required	30 days
Adimab \| Development and Option Agreement
Loss Contingencies [Line Items]
Research and development		$ 100
Upfront fee paid		100
Upfront and final fee		200		200
Exercised option fee		500		500
Adimab \| Development and Option Agreement \| Minimum
Loss Contingencies [Line Items]
Research program milestone fees		150		150
Exercised option milestone fee		1,000		1,000
Target options exercised \| targetOption						1
Adimab \| Development and Option Agreement \| Maximum
Loss Contingencies [Line Items]
Research program milestone fees		200		200
Exercised option milestone fee		$ 4,000		$ 4,000

Commitments and Contingencies - Summarizes Operating Lease Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Operating lease costs	$ 1,312	$ 877
Variable lease costs	398	208
Short-term lease costs	411	0
Total	$ 2,121	$ 1,085

Commitments and Contingencies - Summarizes The Lease Term and Discount Rate For Operating Leases (Details)	Dec. 31, 2021	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Weighted-average remaining lease term (years)	7 years 7 months 6 days	3 years 3 months 18 days
Weighted-average discount rate	8.10%	9.30%

Commitments and Contingencies - Future Minimum Lease Payment (Details) $ in Thousands	Dec. 31, 2021 USD ($)
Commitments and Contingencies Disclosure [Abstract]
2022	$ 2,494
2023	3,138
2024	2,511
2025	2,343
2026	2,409
Thereafter	8,527
Total remaining minimum rental payments	21,422
Less: effect of discounting	(5,761)
Total lease liability	$ 15,661

Income Taxes - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
Income Taxes - Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Operating Loss Carryforwards [Line Items]
Current income tax expenses	$ 0	$ 0
Deferred income tax expenses	0	0
Valuation allowance, deferred tax asset, increase amount	14,300	6,700
Deferred tax assets, operating loss carryforwards not subject to expiration	80,200
Domestic Tax Authority
Operating Loss Carryforwards [Line Items]
Deferred tax assets, operating loss carryforwards subject to expiration	80,300	35,900
Domestic Tax Authority \| Research Tax Credit Carryforward
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	1,300	600
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	74,500	35,300
Tax credit carryforwards	$ 600	$ 400

Income Taxes - Schedule of Effective Income Tax Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Total income tax expense (benefit) differs from the U.S. federal income tax rate to pre-tax income (loss)
Income tax computed at federal statutory rate	21.00%	21.00%
State taxes, net of federal benefit	5.70%	9.90%
Change in valuation allowance	(27.20%)	(42.00%)
R&D credit carryovers	1.80%	1.70%
Interest expense	0.00%	0.00%
Stock-based compensation	(0.90%)	(0.80%)
Cancellation of tranche rights	0.00%	10.20%
Permanent differences	(0.40%)	0.00%
Effective income tax rate	(0.00%)	0.00%

Income Taxes -Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Net operating losses	$ 22,831	$ 10,363
Tax credit carryforwards	1,918	1,021
Lease liability	4,393	731
Capitalized costs—net of amortization	111	124
Reserves and accruals	658	264
Stock-based compensation	500	0
Deferred tax assets	30,411	12,503
Valuation allowance	(26,110)	(11,776)
Deferred tax assets recognized	4,301	727
Deferred tax liabilities:
Right of use asset	(3,762)	(711)
Fixed assets and depreciation	(6)	(12)
Construction in progress	(533)	0
Other	0	(4)
Deferred tax liabilities	(4,301)	(727)
Net deferred tax assets	$ 0	$ 0

Related Parties (Details) - USD ($)	1 Months Ended	12 Months Ended
Related Parties (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2021	Dec. 31, 2020
Related Party Transaction [Line Items]
Total stock-based compensation		$ 4,095,000	$ 632,000
Options issued and outstanding
Related Party Transaction [Line Items]
Options granted (shares)		1,383,000
Exercise price (in usd per share)		$ 14.38
MPM Capital \| MPM Capital \| Management Services
Related Party Transaction [Line Items]
General and administrative expenses		$ 0	31,000
Accounts payable			8,000
Briggs Morrison, M.D. \| Consulting, Advisory and Related Services
Related Party Transaction [Line Items]
Options granted (shares)	46,570
Grant date fair value	$ 50,000
Briggs Morrison, M.D. \| Director \| Consulting, Advisory and Related Services
Related Party Transaction [Line Items]
Exercise price (in usd per share)	$ 1.56
Briggs Morrison, M.D. \| Director \| Consulting, Advisory and Related Services \| Options issued and outstanding
Related Party Transaction [Line Items]
Vesting period	4 years
Total stock-based compensation		$ 13,000	$ 13,000
Briggs Morrison, M.D. \| Director \| Consulting, Advisory and Related Services \| Options issued and outstanding \| Monthly installments
Related Party Transaction [Line Items]
Shares underlying stock options scheduled to vest in monthly installments (percent)	2.0833%

Net Loss Attributable to Common Stockholders per Share - Antidilutive Shares (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	3,620	20,960
Redeemable convertible preferred stock (as converted)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	0	18,280
Options issued and outstanding
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	3,266	2,059
Unvested restricted common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	295	562
Warrants to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	59	59