0001785530-24-000012 | 10-K | XBRL Viewer | Werewolf Therapeutics INC

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Basis of Presentation and Summary of Significant Accounting Policies - Schedule of Property, Plant and Equipment (Details)	Dec. 31, 2023
Laboratory equipment
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	5 years
Furniture and office equipment
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	5 years
Computer equipment
Property, Plant and Equipment [Line Items]
Estimated useful life (in years)	3 years

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Revenue:
Collaboration revenue	$ 19,943	$ 16,401
Operating expenses:
Research and development	41,776	53,761
General and administrative	18,670	18,696
Total operating expenses	60,446	72,457
Operating loss	(40,503)	(56,056)
Other income:
Interest income	7,416	1,908
Interest expense	(3,139)	0
Other (expense) income, net	(1,142)	338
Total other income	3,135	2,246
Net loss	$ (37,368)	$ (53,810)
Net loss per share attributable to common stockholders, basic and diluted
Net loss per share attributable to common stockholders, basic (in usd per share)	$ (1.05)	$ (1.86)
Net loss per share attributable to common stockholders, diluted (in usd per share)	$ (1.05)	$ (1.86)
Weighted-average common shares outstanding, basic and diluted
Weighted average common shares outstanding, basic (in shares)	35,646,572	28,863,935
Weighted average common shares outstanding, diluted (in shares)	35,646,572	28,863,935

Accrued Expenses and Other Current Liabilities

12 Months Ended

Dec. 31, 2023

Payables and Accruals [Abstract]

Accrued Expenses and Other Current Liabilities

6. Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities were comprised as follows:


	December 31,
	2023		2022
	(in thousands)
Employee compensation and benefits	$	3,627	$	3,135
Manufacturing	2,772		6,674
Contract research	1,049		2,990
Professional fees	655		613
Accrued interest	310		—
Success payment liability	—		570
Other	447		170
Total accrued expenses and other current liabilities	$	8,860	$	14,152

Common and Preferred Stock (Tables)

12 Months Ended

Dec. 31, 2023

Equity [Abstract]

Schedule of Common Stock Reserved for Issuance

The Company had reserved shares of common stock for issuance as follows:


	As of December 31,
	2023	2022
Shares reserved for exercises of outstanding stock options	5,700,070	5,244,121
Shares reserved for vesting of restricted stock units	361,500	322,725
Shares reserved for exercises of warrants	58,904	58,904
Shares reserved for issuance under the 2021 Employee Stock Purchase Plan	507,113	244,000
Shares reserved for future issuance under the 2021 Stock Incentive Plan	1,911,660	938,587
Total shares reserved for future issuance	8,539,247	6,808,337

Commitments and Contingencies - Summarizes Operating Lease Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Commitments and Contingencies Disclosure [Abstract]
Operating lease costs	$ 2,442	$ 2,537
Variable lease costs	1,210	837
Short-term lease costs	0	228
Sublease income	(1,562)	(834)
Total	$ 2,090	$ 2,768

Financial Instruments and Fair Value Measurements - Unobservable Inputs (Details) - Recurring	Dec. 31, 2023	Dec. 31, 2022
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Probability of Success Fee Event	1	0.75
Discount rate	0	0.071
Minimum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Expected term (in years)		3 months 29 days
Maximum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Expected term (in years)		9 months

Common and Preferred Stock - Narrative (Details)		2 Months Ended	12 Months Ended
Common and Preferred Stock - Narrative (Details)	Feb. 09, 2024 USD ($)	Mar. 01, 2024 USD ($) shares	Dec. 31, 2023 USD ($) $ / shares shares	Dec. 31, 2022 USD ($) $ / shares shares	May 10, 2022 USD ($)
Class of Stock [Line Items]
Common stock authorized (in shares) \| shares			200,000,000	200,000,000
Dividends payable			$ 0
Proceeds from at the market offering of common stock, net of issuance costs			$ 18,329,000	$ 15,740,000
Preferred stock authorized (in shares) \| shares			5,000,000	5,000,000
Preferred stock outstanding (in shares) \| shares			0	0
Preferred stock issued (in shares) \| shares			0	0
ATM Offering
Class of Stock [Line Items]
Sales commissions, percentage					0.030
Issuance of common stock from initial public offering, net of issuance costs (in shares) \| shares			7,431,981	3,827,567
Price per share (in usd per share) \| $ / shares			$ 2.56	$ 4.36
Proceeds from at the market offering of common stock, net of issuance costs			$ 18,300,000	$ 15,700,000
ATM Offering \| Subsequent Event
Class of Stock [Line Items]
Issuance of common stock from initial public offering, net of issuance costs (in shares) \| shares		3,629,060
Proceeds from at the market offering of common stock, net of issuance costs		$ 17,700,000
Sale of stock increase in offering amount	$ 25,000,000
Sale of stock, total offering price	$ 75,000,000
Maximum \| ATM Offering
Class of Stock [Line Items]
Common stock, amount authorized					$ 50,000,000

Stock-based Compensation - Weighted Average Assumptions (Details) - Stock options	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Risk-free interest rate	3.90%	2.30%
Expected term (in years)	6 years	6 years
Expected annual dividend yield	0.00%	0.00%
Expected volatility	82.70%	77.00%

Nature of Business (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash and cash equivalents	$ 134,343	$ 129,315

Commitments and Contingencies - Future Minimum Lease Payment (Details) $ in Thousands	Dec. 31, 2023 USD ($)
Commitments and Contingencies Disclosure [Abstract]
2024	$ 2,505
2025	2,337
2026	2,403
2027	2,471
2028	2,542
Thereafter	3,716
Total future minimum lease payments	15,974
Less: imputed interest	(3,374)
Total lease liability	$ 12,600

Commitments and Contingencies - Narrative (Details) $ in Thousands		1 Months Ended		12 Months Ended
	Dec. 20, 2019 USD ($)	May 31, 2022 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2019 USD ($)	Nov. 30, 2022 USD ($)	Jun. 30, 2021 USD ($) ft²	Mar. 31, 2021 ft²	Apr. 30, 2019 ft²
Loss Contingencies [Line Items]
Sublease income				$ 1,562	$ 834
Cash paid for amounts included in measurement of lease liabilities				3,000	2,100
Research and development				41,776	53,761
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
Exercised option fee			500				$ 500
Adimab \| Development and Option Agreement \| Minimum
Loss Contingencies [Line Items]
Research program milestone fees			150				500
Exercised option milestone fee			1,000				1,000
Adimab \| Development and Option Agreement \| Maximum
Loss Contingencies [Line Items]
Research program milestone fees			200				1,500
Exercised option milestone fee			$ 4,000				$ 2,000
Lease commenced in April 2019
Loss Contingencies [Line Items]
Laboratory and office space to be rented (in sqft) \| ft²										9,949
Sublease Agreement, Year One
Loss Contingencies [Line Items]
Sublease income		$ 2,100
Lease commenced in March 2021
Loss Contingencies [Line Items]
Laboratory and office space to be rented (in sqft) \| ft²									7,500
Lease commencing June 2021
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	$ 1,000

Stock-based Compensation - Expense Recognized (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	$ 8,008	$ 7,400
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	4,003	3,410
General and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	$ 4,005	$ 3,990

Term Loan

12 Months Ended

Dec. 31, 2023

Debt Disclosure [Abstract]

Term Loan

7. Term Loan

In April 2022, the Company entered into the Loan Agreement with PWB. Under the terms of the Loan Agreement, PWB made available a term loan in an aggregate principal amount of up to $20.0 million (“Tranche I Loan”) available at any time after the closing date until February 28, 2024 as extended to August 31, 2024 upon the satisfaction of certain conditions set forth in the Loan Agreement (such date, the “Amortization Date”). 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 aggregate principal amount of up to $20.0 million (“Tranche II Loan”, or collectively with the Tranche I Loan, the “Term Loans”) available at any time after the closing date until the Amortization Date upon the acceptance by the FDA of two IND submissions on or before March 31, 2023. The Company had not drawn down any of the Term Loans as of December 31, 2022 and had no outstanding borrowings under the Loan Agreement. During the year ended December 31, 2023, the Company drew down the entire $40.0 million available through the Term Loans.

The outstanding notes payable balance under the Term Loans consists of the following:


	December 31, 2023
	(in thousands)
Note payable	$	40,000
Unamortized debt discount and issuance costs	(677)
Net carrying amount of note payable	39,323
Less: current portion of note payable	(6,667)
Note payable, net, less current portion	$	32,656

Subsequent to the interest-only period, which ends on August 31, 2024, the Company is required to make equal monthly principal payments plus interest until the Term Loans mature on August 31, 2026. The Term Loans will bear interest on the outstanding daily balance at a floating annual rate equal to greater of: (i) 0.5% above the prime rate then in effect or (ii) 4.5%. If the prime rate changes throughout the term, the interest rate will be adjusted effective on the date of the prime rate change. All interest chargeable under the Loan Agreement is computed on a 360-day year for the actual number of days elapsed, with interest payable monthly. The Company recognized interest expense related to the Loan Agreement of $2.9 million during the year ended December 31, 2023. No interest expense related to the Loan Agreement was incurred during the year ended December 31, 2022.

The following table presents the total principal payments scheduled to become due during each of the years ended December 31:


	Principal Payments
	(in thousands)
2024	$	6,667
2025	20,000
2026	13,333
	$	40,000

The Company was obligated to pay PWB a one-time fee in the event of certain corporate transactions equal to either (i) the greater of (a) $0.2 million and (b) 2.0% of the amount drawn under the Term Loans, for a transaction occurring on or before March 31, 2023, or (ii) for any transaction occurring thereafter, the greater of (a) $0.4 million and (b) 4.0% of the amount drawn under the Term Loans (the “Success Fee”). The Company determined that the Success Fee constituted a freestanding financial instrument that was required to be accounted for as a liability in connection with ASC Topic 815, Derivatives and Hedging. The Company determined the fair value of the Success Fee upon the closing date of the Loan Agreement and then marked to market the fair value of the Success Fee as of December 31, 2022. The Success Fee Event (as defined in the Loan Agreement) occurred during the second quarter of 2023, resulting in the immediate payment in full of the $1.6 million required Success Fee.

All outstanding obligations under the Loan Agreement are secured by the Company’s personal property (exclusive of any intellectual property) and are subject to acceleration in the event of default. In the event of a late payment or default, the Company is obligated to pay a fee equal to 5.0% of such unpaid amounts. In connection with the Loan Agreement, the Company is required to comply with certain negative covenants, which among other things, restrict the Company from (i) incurring future debt or granting liens, (ii) effectuating a merger or consolidation with or into any other business organization, (iii) paying dividends or making certain other distributions, (iv) selling or otherwise transferring its assets, (v) making investments in any entities or instruments other than certain investments specified in the Loan Agreement and (vi) making capitalized expenditures in excess of 125% of the amount provided for in the annual budget approved by the board of directors. The Loan Agreement also contains 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. On or before September 30, 2023, the Company was required to raise aggregate gross cash process of at least $50.0 million from the sale or issuance of its equity or from strategic partnerships or any similar transaction. From after receipt of those proceeds, the Company is required to maintain at all times at least $20.0 million of unrestricted cash in accounts with PWB, which is included within restricted cash and cash equivalents, net of current portion on the Company’s consolidated balance sheet as of December 31, 2023. On April 17, 2023, the Company achieved the $50.0 million funding milestone, triggering the corresponding $20.0 million cash covenant, full payment of the Success Fee of $1.6 million, and the updated Amortization Date of August 31, 2024.

PWB has the right to accelerate all outstanding obligations of the Company under the Loan Agreement or terminate any remaining Term Loan commitments 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.

- 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.

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+ Details

Financial Instruments and Fair Value Measurements - Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation (Details) - Recurring - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Contract liabilities, beginning balance	$ 570
Contract liabilities, ending balance		$ 570
Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Contract liabilities, beginning balance	570	0
Additions		1,125
Change in fair value	1,030	(555)
Payment at Success Fee Event	(1,600)
Contract liabilities, ending balance	$ 0	$ 570

Net Loss Attributable to Common Stockholders per Share

12 Months Ended

Dec. 31, 2023

Earnings Per Share [Abstract]

Net Loss Attributable to Common Stockholders per Share

14. Net Loss Attributable to Common Stockholders per Share

For purposes of the diluted net loss attributable to common stockholders per share calculation, outstanding stock options, unvested RSAs, unvested RSUs 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:


	December 31,
	2023	2022
Outstanding stock options	5,700,070	5,244,121
Unvested RSUs	361,500	322,725
Warrants to purchase common stock	58,904	58,904
Common stock to be issued under the 2021 ESPP	22,611	29,332
Unvested RSAs	—	81,343
Total	6,143,085	5,736,425

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Operating activities:
Net loss	$ (37,368)	$ (53,810)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	8,008	7,400
Depreciation expense	1,764	1,104
Non-cash interest expense	273	0
Non-cash lease expense	1,575	1,406
Change in fair value of success payment liability	(1,030)	555
Amortization of debt issuance costs	60	203
Loss on disposal of property and equipment	0	7
Changes in operating assets and liabilities:
Prepaid expenses and other assets	1,267	(262)
Other receivables	5,578	(6,928)
Accounts payable, accrued expenses and other liabilities	(4,335)	3,046
Deferred revenue	(6,320)	7,660
Operating lease liability	(2,084)	(977)
Net cash used in operating activities	(32,612)	(40,596)
Investing activities:
Purchases of property and equipment	(769)	(3,611)
Net cash used in investing activities	(769)	(3,611)
Financing activities:
Proceeds from at the market offering of common stock, net of issuance costs	18,329	15,740
Proceeds from drawdown of term loans	40,000	0
Proceeds from issuances under Employee Stock Purchase Plan	93	0
Proceeds from stock option exercises	7	254
Payment of deferred financing costs	0	(88)
Net cash provided by financing activities	58,429	15,906
Net increase (decrease) in cash and cash equivalents and restricted cash and cash equivalents	25,048	(28,301)
Cash, cash equivalents and restricted cash and cash equivalents—beginning of period	130,529	158,830
Cash, cash equivalents and restricted cash and cash equivalents—end of period	155,577	130,529
Reconciliation of cash, cash equivalents and restricted cash and cash equivalents to the consolidated balance sheets
Cash and cash equivalents	134,343	129,315
Prepaid expenses and other current assets	211	0
Restricted cash and cash equivalents, net of current portion	21,023	1,214
Cash, cash equivalents and restricted cash	155,577	130,529
Supplemental disclosure of cash flow information:
Cash paid for interest	2,556	0
Supplemental disclosure of non-cash investing and financing activities:
Purchases of property and equipment in accounts payable and accrued expenses	76	111
Issuance costs in accounts payable and accrued expenses	$ 36	$ 4

Common and Preferred Stock - Schedule of Common Stock Reserved for Issuance (Details) - shares	Dec. 31, 2023	Dec. 31, 2022
Class of Stock [Line Items]
Common stock available for issuance (in shares)	8,539,247	6,808,337
Shares reserved for exercises of outstanding stock options
Class of Stock [Line Items]
Common stock available for issuance (in shares)	5,700,070	5,244,121
Unvested RSUs
Class of Stock [Line Items]
Common stock available for issuance (in shares)	361,500	322,725
Shares reserved for exercises of warrants
Class of Stock [Line Items]
Common stock available for issuance (in shares)	58,904	58,904
Shares reserved for issuance under the 2021 Employee Stock Purchase Plan
Class of Stock [Line Items]
Common stock available for issuance (in shares)	507,113	244,000
Shares reserved for future issuance under the 2021 Stock Incentive Plan
Class of Stock [Line Items]
Common stock available for issuance (in shares)	1,911,660	938,587

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(28))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-2

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.6-03(i)(2))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479886/946-10-S99-3

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.6-03(i)(1))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479886/946-10-S99-3

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.6-03(i)(2)(i))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479886/946-10-S99-3

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.6-03(i)(2)(ii))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479886/946-10-S99-3

+ Details

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2023

Commitments and Contingencies Disclosure [Abstract]

Summary of Operating Lease Costs

The following table summarizes operating lease costs:


	Year Ended December 31,
	2023		2022
	(in thousands)
Operating lease costs	$	2,442	$	2,537
Variable lease costs	1,210		837
Short-term lease costs	—		228
Sublease income	(1,562)		(834)
Total	$	2,090	$	2,768

Cash paid for amounts included in the measurement of lease liabilities were $3.0 million and $2.1 million during the years ended December 31, 2023 and 2022, respectively.

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


	As of December 31,
	2023		2022
Weighted-average remaining lease term (years)	6.3		7.0
Weighted-average discount rate	8.0	%	8.1	%

Future Minimum Lease Payments

As of December 31, 2023, the future minimum lease payments due under the Company’s leases for each of the next five years ended December 31, and thereafter are as follows:


	Operating Leases
	(in thousands)
2024	$	2,505
2025	2,337
2026	2,403
2027	2,471
2028	2,542
Thereafter	3,716
Total future minimum lease payments	15,974
Less: imputed interest	(3,374)
Total lease liability	$	12,600

Nature of Business	12 Months Ended
Nature of Business	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Business	1. 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 Watertown, Massachusetts. Since inception, the Company has devoted substantially all of its efforts and financial resources to organizing and staffing the company; business planning; raising capital; developing and optimizing its platform technology; identifying potential product candidates; enhancing its intellectual property portfolio; undertaking research, preclinical studies, and clinical trials; and enabling manufacturing for its development programs. 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. The Company had cash and cash equivalents of $134.3 million at December 31, 2023. 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 date of issuance of the consolidated financial statements included in 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.

Jazz Collaboration and License Agreement

12 Months Ended

Dec. 31, 2023

Business Combination and Asset Acquisition [Abstract]

Jazz Collaboration and License Agreement

3. Jazz Collaboration and License Agreement

In April 2022, the Company entered into an exclusive global collaboration and license agreement (the “Collaboration Agreement”) with Jazz Pharmaceuticals Ireland Limited (“Jazz”) pursuant to which the Company granted Jazz certain licenses to develop and commercialize products containing the Company’s Interferon alpha (“IFNα”) INDUKINE™ molecule, JZP898 (formerly WTX-613), as well as products containing certain isolated recombinant polypeptides comprising IFNα that meet specified criteria (each such product, a “Licensed Product”). Under the Collaboration Agreement, the Company is responsible for certain preclinical development activities with respect to JZP898 and other development activities specified in mutually agreed upon development plans. Jazz will generally reimburse the Company for the cost of such activities. Jazz will be responsible for all other development and commercialization activities conducted to exploit the Licensed Products, including submission of an investigational new drug application (“IND”) to the U.S. Food and Drug Administration (the “FDA”). Jazz received IND application clearance for JZP898 in July 2023.

Under the terms of the Collaboration Agreement, the Company received a non-refundable upfront cash payment of $15.0 million in April 2022 and a variable consideration payment of $5.0 million in July 2023, which is included in the overall transaction price as described below.

Milestones and Royalties

As of December 31, 2023, the Company is eligible to receive up to $515.0 million in development and regulatory milestones, and up to $740.0 million in sales-based milestones for all Licensed Products. In addition, the Company is eligible to receive tiered mid-single digit royalties based on Jazz’s, and any of its affiliates’ and sublicensees’ annual net sales of Licensed Products, subject to reduction in specified circumstances.

As of December 31, 2023, the Company has not recognized any revenue related to sales-based milestones.

Accounting Analysis under ASC 606

Identification of the Contract(s)

The Company assessed the Collaboration Agreement and concluded that it represents a contract with a customer within the scope of ASC 606.

Identification of Promises and Performance Obligations

The Company has concluded that the exclusive license to its intellectual property, JZP898, and the non-exclusive corresponding “know-how” are not capable of being distinct from the other promises within the contract, and as such, the Company has determined that the license and “know-how” combined with the other research and development services and supply represent a single combined performance obligation.

Determination of Transaction Price

The overall transaction price as of the inception of the contract was determined to be $32.3 million, which was comprised of the nonrefundable upfront payment of $15.0 million and the estimated costs for research services of $17.3 million. Outside of the estimated costs for research services, there was no other variable consideration included in the transaction price at inception. The Company used the most likely amount method to estimate variable consideration and estimated that the most likely amount for each potential development and regulatory milestone payment under this agreement was zero at inception of the contract, as achievement of those milestones was uncertain and highly susceptible to factors outside the Company’s control. Accordingly, all such milestone payments were excluded from the transaction price at inception. Management re-evaluates the transaction price at the end of each reporting period and as uncertain events are resolved or other changes in circumstances occur, adjusts the transaction price as necessary. During the year ended December 31, 2023, the overall transaction price was adjusted to include $5.0 million in variable consideration that was previously excluded based on the Company’s evaluation of the variable constraint associated with the variable payment. Sales based royalties, including milestones based on the level of sales, were also excluded from the transaction price, as the license is deemed to be the predominant item to which the royalties relate. The Company will recognize such revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied).

The upfront payment of $15.0 million was recorded as deferred revenue and, along with payments related to the Company’s conduct of research services under the Collaboration Agreement or any development and regulatory milestones, will be recognized as revenue using an input-based measurement of actual costs incurred as a percentage of the estimated total costs expected to be incurred over the expected term of conduct of the research services. The Company believes this input-based method to recognize revenue best reflects the transfer of value to Jazz. The remaining deferred revenue as of December 31, 2023 is expected to be recognized as revenue over a term of approximately 2.3 years.

Recognition of Revenue

The Company uses the cost-to-cost input method, which best depicts the research services performed for the customer, to measure the revenue recognized under the Collaboration Agreement. Significant judgements used in the cost-to-cost method include estimated costs for research services and assumptions about the timing of when those costs are expected to be incurred. Differences in these estimates and assumptions can have a significant impact on the measurement and timing of when revenue under the Collaboration Agreement is recognized. For the years ended December 31, 2023 and 2022, the Company recognized $19.9 million and $16.4 million of revenue related to the Collaboration Agreement, respectively. The measurement of revenue recognized based on the cost-to-cost input method and the timing of payments received under the Collaboration Agreement directly impact the amounts reported as contract liabilities in the Company’s consolidated balance sheets as of December 31, 2023 and 2022. During the year ended December 31, 2023, the total revenue recognized included a cumulative catch-up of revenue of $4.2 million related to a variable payment that was previously excluded from the overall transaction price based on the Company’s evaluation of the variable constraint associated with the variable payment. The cumulative catch-up of revenue was recognized based on the cost-to-cost input method discussed above. Costs associated with the Collaboration Agreement are recorded in research and development expense in the consolidated statements of operations, and were $8.6 million and $9.1 million during the years ended December 31, 2023 and 2022, respectively. Revenue from the reimbursement of costs for research activities were recognized during each of the respective periods in amounts equal to the costs incurred.

The following table presents the activity in the Company’s contract liabilities during the year ended December 31, 2023:


	Beginning of Period Balance		Additions		Reductions		End of Period Balance
	(in thousands)





Contract liabilities:
Deferred revenue	$	7,660	$	5,000	$	(11,320)	$	1,340
Total contract liabilities	$	7,660	$	5,000	$	(11,320)	$	1,340

The following table presents the activity in the Company’s contract liabilities during the year ended December 31, 2022:


	Beginning of Period Balance		Additions		Reductions		End of Period Balance
	(in thousands)





Contract liabilities:
Deferred revenue	$	—	$	15,000	$	(7,340)	$	7,660
Total contract liabilities	$	—	$	15,000	$	(7,340)	$	7,660

Unbilled receivables related to the Collaboration Agreement of $0.4 million and $4.1 million is included in other receivables in the accompanying consolidated balance sheets as of December 31, 2023 and 2022, respectively. Receivables related to the Collaboration Agreement of $0.9 million and $2.8 million are included in other receivables in the accompanying consolidated balance sheets as of December 31, 2023 and 2022, respectively. Revenue recognized during the year ended December 31, 2023 includes $6.7 million of revenue that was included in deferred revenue as of December 31, 2022. No revenue recognized during the year ended December 31, 2022 was included in deferred revenue as of December 31, 2021.

As of December 31, 2023, the Company has not received any royalty payments under the Collaboration Agreement.

Basis of Presentation and Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2023

Accounting Policies [Abstract]

Schedule of Property, Plant and Equipment

Property and equipment are depreciated over the following periods:


Laboratory equipment			5 years
Furniture and office equipment			5 years
Computer equipment			3 years
Leasehold improvements			Shorter of lease term or useful life of asset

Property and equipment, net was comprised as follows:


	December 31,
	2023		2022
	(in thousands)
Leasehold improvements	$	7,971	$	7,971
Laboratory equipment	2,339		1,635
Computer equipment	512		418
Furniture and fixtures	306		264
Construction in progress	—		106
Total property and equipment, gross	11,128		10,394
Less: accumulated depreciation	(3,170)		(1,406)
Total property and equipment, net	$	7,958	$	8,988

Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2023

Share-Based Payment Arrangement [Abstract]

Stock-based Compensation Expense Recognized

Total stock-based compensation expense recognized in the consolidated statements of operations was as follows:


	Year Ended December 31,
	2023		2022
	(in thousands)
Research and development	$	4,003	$	3,410
General and administrative	4,005		3,990
Total stock-based compensation	$	8,008	$	7,400

Restricted Stock Awards Activity

The following table summarizes RSA activity during the year ended December 31, 2023:


	Shares/Units	Weighted-Average Grant Date Fair Value Per Share
Unvested at December 31, 2022	81,343	$	1.38
Granted	—	$	—
Vested	(81,343)	$	1.38
Forfeited	—	$	—
Unvested at December 31, 2023	—	$	—

The following table summarizes RSU activity during the year ended December 31, 2023:


	Shares/Units	Weighted-Average Grant Date Fair Value Per Share
Unvested at December 31, 2022	322,725	$	4.32
Granted	150,000	$	2.45
Vested	(105,000)	$	2.96
Forfeited	(6,225)	$	4.97
Unvested at December 31, 2023	361,500	$	3.92

Weighted -average Valuation Assumptions

The fair value of stock options granted during the years ended December 31, 2023 and 2022 was calculated on the date of grant using the following weighted-average assumptions:


	Year Ended December 31,
	2023		2022
Risk-free interest rate	3.9	%	2.3	%
Expected term (in years)	6.0		6.0
Expected annual dividend yield	—	%	—	%
Expected volatility	82.7	%	77.0	%

Summary of Stock Option Activity

The following table summarizes stock option activity during the year ended December 31, 2023:


	Options Outstanding
	Number of Options	Weighted-Average Exercise Price per Share		Weighted-Average Remaining Contractual Life (in years)	Aggregate Intrinsic Value (in millions)
Outstanding at December 31, 2022	5,244,121	$	7.86
Granted	1,618,780	$	2.16
Exercised	(2,956)	$	1.98
Cancelled	(1,159,875)	$	4.68
Outstanding, December 31, 2023	5,700,070	$	6.89	7.81	$	3.6
Exercisable at December 31, 2023	3,169,212	$	7.60	7.43	$	1.5

Financial Instruments and Fair Value Measurements - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Jun. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Success fee liability paid	$ 1,600
Level 3 \| Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Change in fair value		$ 1,030	$ (555)

Stock-based Compensation

12 Months Ended

Dec. 31, 2023

Share-Based Payment Arrangement [Abstract]

Stock-based Compensation

9. 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 RSAs, including vesting requirements, are determined by the board of directors, subject to the provisions of the 2017 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 initial public offering (the “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 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, 2023, a total of 2,956,150 additional shares have been added to the total shares authorized for issuance under the 2021 Plan in accordance with these terms.

As of December 31, 2023, there were 1,911,660 shares available for future issuance under the 2021 Plan.

2021 Employee Stock Purchase Plan

The 2021 ESPP permits eligible employees to purchase shares of the Company’s common stock at a discount and consists of consecutive six-month offering periods, each containing a single six-month purchase period. On the first day of each offering period, each employee who is enrolled in the 2021 ESPP will automatically receive an option to purchase up to a whole number of shares of the Company’s common stock. The purchase price of each of the shares purchased, in a given purchase period, will be equal to 85% of the lesser of the closing price of a share of the Company’s common stock on (i) the first day of the offering period, or (ii) the last day of the offering period. During the year ended December 31, 2023, 52,037 shares of the Company’s common stock were purchased by participants of the 2021 ESPP for total proceeds of $0.1 million. No shares of the Company’s common stock were purchased by participants of the 2021 ESPP during year ended December 31, 2022.

Stock-Based Compensation Expense

Total stock-based compensation expense recognized in the consolidated statements of operations was as follows:


	Year Ended December 31,
	2023		2022
	(in thousands)
Research and development	$	4,003	$	3,410
General and administrative	4,005		3,990
Total stock-based compensation	$	8,008	$	7,400

RSA 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 RSA activity during the year ended December 31, 2023:


	Shares/Units	Weighted-Average Grant Date Fair Value Per Share
Unvested at December 31, 2022	81,343	$	1.38
Granted	—	$	—
Vested	(81,343)	$	1.38
Forfeited	—	$	—
Unvested at December 31, 2023	—	$	—

The aggregate fair value of RSAs that vested during the years ended December 31, 2023 and 2022, based upon the fair value of the stock underlying the RSAs on the day of vesting, was $0.2 million and $1.2 million, respectively.

RSU Activity

The Company has also granted RSUs to its employees under the 2021 Plan. The following table summarizes RSU activity during the year ended December 31, 2023:


	Shares/Units	Weighted-Average Grant Date Fair Value Per Share
Unvested at December 31, 2022	322,725	$	4.32
Granted	150,000	$	2.45
Vested	(105,000)	$	2.96
Forfeited	(6,225)	$	4.97
Unvested at December 31, 2023	361,500	$	3.92

As of December 31, 2023, there was unrecognized stock-based compensation expense related to unvested RSUs of $0.6 million, which the Company expects to recognize over a weighted-average period of approximately 0.63 years.

The aggregate fair value of RSUs that vested during the year ended December 31, 2023, based upon the fair value of the stock underlying the RSUs on the day of vesting was $0.2 million. No RSUs vested during the year ended December 31, 2022.

Stock Option Activity

During the year ended December 31, 2022, the Company granted performance-based stock options to certain executive officers for the purchase of an aggregate of 883,352 shares of common stock with a grant date fair value of $3.36 per share. These stock options would have vested only upon achievement of specified performance targets related to certain business objectives prior to December 31, 2023. These performance targets were not achieved, and accordingly these awards expired without vesting on December 31, 2023. No stock-based compensation expense has been recognized during the year ended December 31, 2023 or 2022 based on the Company’s assessment about the probability that the performance targets would be achieved prior to expiration.

The fair value of stock options granted during the years ended December 31, 2023 and 2022 was calculated on the date of grant using the following weighted-average assumptions:


	Year Ended December 31,
	2023		2022
Risk-free interest rate	3.9	%	2.3	%
Expected term (in years)	6.0		6.0
Expected annual dividend yield	—	%	—	%
Expected volatility	82.7	%	77.0	%

The valuation assumptions were determined as follows:

•Risk-free interest rate: The yield on zero-coupon U.S. Treasury securities for a period that was commensurate with the expected term of the awards.

•Expected term (in years): The expected term of the awards represents the period of time that the awards were expected to be outstanding. The Company uses the simplified method to estimate the expected term due to a lack of sufficient historical exercise data to provide a reasonable basis on which to estimate the expected term. Under this method, the expected term equals the average of the vesting term and the original contractual term of the option.

•Expected annual dividend yield: The estimated dividend yield was zero because the Company has no history of paying dividends, and does not intend to do so in the foreseeable future.

•Expected volatility: The expected term of stock options granted by the Company is generally longer than the trading history of the Company’s common stock since the IPO on April 30, 2021. Accordingly, the Company estimated the expected volatility based on the historical volatility of a group of publicly-traded companies with similar characteristics to the Company, including stage of product development and therapeutic focus within the life sciences industry. The historical volatility of these companies was calculated over a period of time commensurate with the expected term of the stock option.

Using the Black-Scholes option pricing model, the weighted-average grant date fair value of stock options granted during the years ended December 31, 2023 and 2022 was $1.56 and $5.98 per share, respectively.

The following table summarizes stock option activity during the year ended December 31, 2023:


	Options Outstanding
	Number of Options	Weighted-Average Exercise Price per Share		Weighted-Average Remaining Contractual Life (in years)	Aggregate Intrinsic Value (in millions)
Outstanding at December 31, 2022	5,244,121	$	7.86
Granted	1,618,780	$	2.16
Exercised	(2,956)	$	1.98
Cancelled	(1,159,875)	$	4.68
Outstanding, December 31, 2023	5,700,070	$	6.89	7.81	$	3.6
Exercisable at December 31, 2023	3,169,212	$	7.60	7.43	$	1.5

The aggregate intrinsic fair value of stock options exercised during the year ended December 31, 2023 was nominal. The aggregate intrinsic fair value of stock options exercised during the year ended December 31, 2022 was $0.4 million.

As of December 31, 2023, there was unrecognized stock-based compensation expense related to unvested stock options of $9.9 million, which the Company expects to recognize over a weighted-average period of approximately 2.0 years.

Financial Instruments and Fair Value Measurements - Assets Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Liabilities
Success payment liability	$ 0	$ 570
Recurring
Assets:
Total assets	149,294	128,812
Liabilities
Success payment liability		570
Total liabilities		570
Money market funds \| Recurring
Assets:
Money market funds	149,294	128,812
Level 1 \| Recurring
Assets:
Total assets	149,294	128,812
Liabilities
Success payment liability		0
Total liabilities		0
Level 1 \| Money market funds \| Recurring
Assets:
Money market funds	149,294	128,812
Level 2 \| Recurring
Assets:
Total assets	0	0
Liabilities
Success payment liability		0
Total liabilities		0
Level 2 \| Money market funds \| Recurring
Assets:
Money market funds	0	0
Level 3 \| Recurring
Assets:
Total assets	0	0
Liabilities
Success payment liability		570
Total liabilities	0	570	$ 0
Level 3 \| Money market funds \| Recurring
Assets:
Money market funds	$ 0	$ 0

Commitments and Contingencies - Summarizes The Lease Term and Discount Rate For Operating Leases (Details)	Dec. 31, 2023	Dec. 31, 2022
Commitments and Contingencies Disclosure [Abstract]
Weighted-average remaining lease term (years)	6 years 3 months 18 days	7 years
Weighted-average discount rate	8.00%	8.10%

Audit Information	12 Months Ended
Audit Information	Dec. 31, 2023
Audit Information [Abstract]
Auditor Firm ID	42
Auditor Name	Ernst & Young LLP
Auditor Location	Boston, Massachusetts

Commitment and Contingencies

12 Months Ended

Dec. 31, 2023

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

10. 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. In May 2022, the Company entered into a sublease agreement with Crossbow Therapeutics, Inc. (“Crossbow”), to sublease the entirety of this space. The total rent due to the Company for the subleased premises over the term of the sublease is approximately $2.1 million, which is greater than the annual rent paid by the Company to the landlord for the leased premises over the same term. Rent expense associated with the April 2019 operating lease is recognized net of the lease income generated from the sublease agreement. Lease income is allocated to either research and development expense or general and administrative expense in the same manner that the associated rent expense is allocated. Crossbow is obligated to pay all real estate taxes and costs related to the subleased premises, including cost of operations, maintenance, repair, replacement, and property management.

•A March 2021 short-term lease for approximately 7,500 square feet of office and laboratory space which commenced in April 2021 and terminated 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 the short-term lease was recognized as incurred.

•A June 2021 operating lease for approximately 25,778 square feet of office and laboratory space, which commenced in May 2022 and terminates in May 2030. The lease is subject to fixed-rate rent escalations and provided for $5.7 million in tenant improvements, which the Company fully utilized, 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 and cash equivalents, net of current portion as of December 31, 2023 and 2022.

The following table summarizes operating lease costs:


	Year Ended December 31,
	2023		2022
	(in thousands)
Operating lease costs	$	2,442	$	2,537
Variable lease costs	1,210		837
Short-term lease costs	—		228
Sublease income	(1,562)		(834)
Total	$	2,090	$	2,768

Cash paid for amounts included in the measurement of lease liabilities were $3.0 million and $2.1 million during the years ended December 31, 2023 and 2022, respectively.

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


	As of December 31,
	2023		2022
Weighted-average remaining lease term (years)	6.3		7.0
Weighted-average discount rate	8.0	%	8.1	%

As of December 31, 2023, the future minimum lease payments due under the Company’s leases for each of the next five years ended December 31, and thereafter are as follows:


	Operating Leases
	(in thousands)
2024	$	2,505
2025	2,337
2026	2,403
2027	2,471
2028	2,542
Thereafter	3,716
Total future minimum lease payments	15,974
Less: imputed interest	(3,374)
Total lease liability	$	12,600

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 2018 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. In July 2021, the Company and Adimab entered into the First Amended and Restated Development and Option Agreement to extend the target selection time period and to allow for the Company to add additional antibody discovery programs to be covered under the agreement, but otherwise retaining all other material provisions of the Adimab License.

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, 2023, the Company has not exercised any options and has not made any payments for clinical or sales-based milestones or royalties pursuant to the Adimab Agreement.

Adimab 2022 Collaboration

In November 2022, the Company entered into a Collaboration Agreement (the “Adimab Collaboration Agreement”) with Adimab. Under the terms of the Adimab Collaboration Agreement, Adimab has agreed to provide the Company with services to help discover, generate, optimize and/or engineer specified proteins. In addition, Adimab will provide the Company with a license to certain Adimab core technologies, patents and products applicable to certain targets (“Adimab Collaboration License”), separate from those provided in the 2018 Adimab Agreement.

Under the terms of the Adimab Collaboration Agreement, the Company must pay Adimab milestone fees with respect to each research program ranging from $500,000 to $1.5 million based on the achievement of certain clinical milestones by the Company. The Adimab Collaboration Agreement provides the Company with an option to obtain any development and commercialization licenses from Adimab used in products. To exercise an option, the Company must pay a $500,000 fee for each product option exercised.

For each product sold, the Company is also obligated to pay certain milestones ranging from $1.0 million to $2.0 million based on the achievement of the first commercial sale in certain countries. 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 Collaboration 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, 2023, the Company has not exercised any options and has not made any payments for clinical or sales-based milestones or royalties pursuant to the Adimab Collaboration Agreement.

Defined Contribution Benefit Plan (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Retirement Benefits [Abstract]
Employer matching contribution, percent of match	50.00%
Employer matching contribution, percent of employees' gross pay	6.00%
Defined contribution plan expense	$ 0.2	$ 0.2

Basis of Presentation and Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2023

Accounting Policies [Abstract]

Basis of Presentation

Basis of Presentation and Consolidation

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

The Company operates in one business segment, which focuses on the discovery and development of cancer therapeutics. The Company’s chief operating decision maker, its Chief Executive Officer, makes operating decisions based upon the performance of the enterprise as a whole and utilizes the Company’s consolidated financial statements for decision making.

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. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, those related to revenue recognition, accrued expenses, assumptions used in the valuation of stock-based compensation expense and income taxes. Actual results could differ from those estimates.

Fair Value of Financial Instruments

ASC Topic 820, 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 defines 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-tiered fair value hierarchy that distinguishes between the following:

•Level 1 - Observable inputs such as quoted prices (unadjusted) in active markets for identical assets or liabilities.

•Level 2 - Inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly, including quoted prices for similar assets or liabilities in active markets; quoted prices for identical or similar assets or liabilities in markets that are not active; inputs other than quoted prices that are observable for the asset or liability (e.g., interest rates); and inputs that are derived principally from or corroborated by observable market data by correlation or other means.

•Level 3 - Unobservable inputs for which little or no market data exists and that are significant to the fair value measurement, such as the Company’s own assumptions used to measure assets and liabilities at fair value.

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. The classification of a financial asset or liability 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 and Restricted Cash and Cash Equivalents

The Company’s cash and cash equivalents consist of cash maintained within standard checking accounts. The Company also maintains cash sweep accounts in which cash from its main operating cash accounts are 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.

The Company maintained restricted cash and cash equivalents of $21.2 million and $1.2 million at December 31, 2023 and December 31, 2022, respectively. At December 31, 2023, $20.0 million of the restricted cash and cash equivalents balance represents an obligation under the term loan facility to maintain a minimum cash balance in the Company’s accounts with Pacific Western Bank (“PWB”). This obligation became effective upon imminent achievement of the funding goal as required by the terms of an amended and restated loan and security agreement (the “Loan Agreement”) with PWB (see Note 7, Term Loan). The remaining restricted cash and cash equivalents balance as of December 31, 2023 and the entire restricted cash and cash equivalents balance as of December 31, 2022 are comprised solely of letters of credit required pursuant to the Company’s leased office spaces (see Note 10, Commitments and Contingencies). Restricted cash and cash equivalents are presented as current or non-current assets based on when the restrictions are expected to expire. The current portion of restricted cash and cash equivalents is included in prepaid expenses and other current assets in the accompanying consolidated balance sheets.

Property and Equipment

Property and equipment are stated at cost. Depreciation is recorded using the straight-line method over the estimated useful lives of the applicable assets. Upon the sale or retirement of an asset, the cost and related accumulated depreciation are eliminated from the respective account, and the resulting gain or loss, if any, is included in current operations. Amortization of leasehold improvements is recorded as depreciation expense using the straight-line method over the shorter of the remaining lease term or the estimated useful life of the related asset. The Company capitalizes property and equipment that are acquired for research and development activities and that have an 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. Property and equipment are depreciated over the following periods:


Laboratory equipment			5 years
Furniture and office equipment			5 years
Computer equipment			3 years
Leasehold improvements			Shorter of lease term or useful life of asset

Costs for property and equipment not yet placed into service are classified as construction in progress and depreciated in accordance with the above guidelines once placed into service.

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. If such events or changes in circumstances arise, the Company compares the carrying amount of the long-lived assets to the estimated future undiscounted cash flows expected to be generated by the long-lived assets. If the estimated aggregate undiscounted cash flows are less than the carrying amount of the long-lived assets, an impairment charge, calculated as the amount by which the carrying amount of the assets exceeds the fair value of the assets, is recorded. The fair value of long-lived assets is determined based on the

estimated discounted cash flows expected to be generated from the long-lived assets. The Company has not recorded any material impairment charges during the years ended December 31, 2023 or 2022.

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 twelve months are recognized on the balance sheet as right-of-use assets and current or non-current lease liabilities, as applicable. The Company does not recognize leases with terms of twelve months or less on the balance sheet. The lease term is determined at lease commencement, and includes the noncancellable period during which the Company has the right to use the underlying asset. Any period covered by an option to extend or terminate a lease is included in the lease term if the Company is reasonably certain that the option to extend will be exercised or the option to terminate will not be exercised. The Company monitors its plans to renew its material leases on a quarterly basis.

The Company combines lease and non-lease components for its leases. Lease payments included in determining the right-of-use asset and lease liability recognized include fixed payments to be paid over the term of the lease, less any lease incentives to be paid or payable to the Company by the lessor. Variable lease payments are included if they are based on an index or rate. Variable lease payments that are not based on an index or rate are recognized as expense in the period incurred.

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 lease liability is measured as the value of the remaining lease payments, discounted to present value using the IBR for the lease.

All of the Company’s leases are classified as operating leases. Operating lease expense is recognized over the lease term using the straight-line method.

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 ASC 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. 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 considers the milestones 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.

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 issues stock-based awards to employees and directors, generally in the form of stock options, restricted stock units (“RSUs”), restricted stock awards (“RSAs”), or as awards under the 2021 Employee Stock Purchase Plan (the “2021 ESPP”). Stock-based compensation is measured at the grant date based on the estimated fair value of the award and recognized as expense over the requisite service period of the award on a straight-line basis. For awards with performance conditions, the Company estimates the likelihood of satisfaction of the performance condition, which affects the period over which the expense is recognized. When the likelihood of satisfying the performance conditions related to an award is determined to be probable, the expense is recognized over the requisite service period. The Company has not granted any awards with market conditions. The Company recognizes forfeitures of stock-based awards as they occur.

The grant date fair value of stock options, and awards granted under the 2021 ESPP are measured using the Black-Scholes valuation model, which requires the Company to make assumptions about the fair value of the underlying common stock on the date of grant. The grant date fair value of RSUs and RSAs is estimated to be equal to the closing price of the Company’s common stock on the date of grant. In the event that stock-based awards are granted in contemplation of or shortly before a planned release of material non-public information, and such information is expected to result in a material increase in the share price of the Company’s common stock, the Company may consider whether an adjustment to the observable market price is required when estimating the grant date fair value.

Debt Issuance Costs

Certain costs associated with the issuance of debt instruments are capitalized and amortized over the term of the respective debt instrument using the effective interest method through the maturity date of the related debt instrument and are recognized as a non-cash component of interest expense. The carrying value of the Company’s debt instruments are presented net of debt issuance costs.

Equity Issuance Costs

Equity issuance costs represent costs paid to third parties to secure equity financing and generally consist of sales agent commissions, incremental legal fees and other professional fees. Equity issuance costs are capitalized as other assets until the associated equity financing is consummated. Upon consummation of an equity financing, these costs are recorded as a reduction of additional paid-in capital. In the event that a planned equity financing is abandoned, any capitalized equity issuance costs are immediately expensed to operating expenses in the consolidated statement of operations.

Income Taxes

Income taxes are recorded in accordance with ASC Topic 740, Income Taxes (“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. The Company recognizes any material interest and penalties related to unrecognized tax benefits in income tax expense.

Comprehensive Loss

The Company does not have items of other comprehensive loss for the years ended December 31, 2023 and 2022, and therefore does not present a consolidated statement of comprehensive loss. The Company’s comprehensive loss equals its net loss.

Basic and Diluted Net Loss per Common Share

Basic net loss per share is calculated based upon the weighted-average number of common shares outstanding during the period, excluding outstanding stock options and RSUs that have been issued but are not yet vested. Diluted net loss per share is calculated based upon the weighted-average number of common shares outstanding during the period plus the dilutive impact of weighted-average common equivalent shares outstanding during the period. The potentially dilutive shares of common stock resulting from the assumed exercise of outstanding stock options and the assumed vesting of RSUs are determined under the treasury stock method.

Concentration of Credit Risk

Concentration of Credit Risk and Off-Balance Sheet Risk

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

In December 2023, the FASB issued ASU No. 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures (“ASU No. 2023-09”), which enhances the transparency and decision usefulness of income tax disclosures primarily related to rate reconciliation and income taxes paid. The provisions of ASU No. 2023-09 are effective for fiscal years beginning after December 15, 2024, with early adoption permitted, and are required to be applied on a prospective basis. The Company is currently evaluating the impact that this standard will have on its consolidated financial statements.

Other accounting standards that have been issued or proposed by the FASB or other standards-setting bodies that do not require adoption until a future date are not expected to have a material impact on the Company’s consolidated financial statements upon adoption.

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.

Consolidated Statements of Stockholders’ Equity - USD ($) $ in Thousands	Total	Market Offering	Common Stock	Common Stock Market Offering	Additional Paid-in Capital	Additional Paid-in Capital Market Offering	Accumulated Deficit
Stockholders' equity, beginning balance (in shares) at Dec. 31, 2021			27,607,954
Stockholders' equity, beginning balance at Dec. 31, 2021	$ 152,787		$ 2		$ 405,680		$ (252,895)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock from initial public offering, net of issuance costs (in shares)				3,827,567
Issuance of common stock from at the market offering, net of issuance costs		$ 15,736		$ 1		$ 15,735
Stock-based compensation expense	7,400				7,400
Stock option exercises (in shares)			79,553
Stock option exercises	224				224
Net loss	(53,810)						(53,810)
Stockholders' equity, ending balance (in shares) at Dec. 31, 2022			31,515,074
Stockholders' equity, ending balance at Dec. 31, 2022	122,337		$ 3		429,039		(306,705)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock from initial public offering, net of issuance costs (in shares)			157,037	7,431,981
Issuance of common stock from at the market offering, net of issuance costs	93	$ 18,297		$ 1	93	$ 18,296
Stock-based compensation expense	8,008				8,008
Stock option exercises (in shares)			2,956
Stock option exercises	7				7
Net loss	(37,368)						(37,368)
Stockholders' equity, ending balance (in shares) at Dec. 31, 2023			39,107,048
Stockholders' equity, ending balance at Dec. 31, 2023	$ 111,374		$ 4		$ 455,443		$ (344,073)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(g)(1)(ii))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 323
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-Name Accounting Standards Codification
-Section 50
-Paragraph 3
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-URI https://asc.fasb.org//1943274/2147481687/323-10-50-3

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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-Section 50
-Paragraph 28
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482907/825-10-50-28

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482765/220-10-50-6

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483443/250-10-50-3

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
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-Paragraph 1
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 65
-Paragraph 1
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480175/815-40-65-1

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
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-Paragraph 8
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-URI https://asc.fasb.org//1943274/2147483443/250-10-50-8

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483443/250-10-50-9

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483443/250-10-50-11

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483443/250-10-50-11

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483443/250-10-50-4

Reference 13: http://www.xbrl.org/2003/role/exampleRef
-Topic 946
-SubTopic 830
-Name Accounting Standards Codification
-Section 55
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480167/946-830-55-10

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section 45
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483581/946-220-45-7

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(18))
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Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
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Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
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+ Details

- Definition

Equity impact of the value of new stock issued during the period. Includes shares issued in an initial public offering or a secondary public offering.

+ References + Details

- Definition

Amount of equity (deficit) attributable to parent. Excludes temporary equity and equity attributable to noncontrolling interest.

+ References

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+ Details

Net Loss Attributable to Common Stockholders per Share (Details) - shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	6,143,085	5,736,425
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	5,700,070	5,244,121
Unvested RSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	361,500	322,725
Warrants to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	58,904	58,904
Common stock to be issued under the 2021 ESPP
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	22,611	29,332
Unvested RSAs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	0	81,343

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2023	Dec. 31, 2022
Statement of Financial Position [Abstract]
Preferred stock par value (in usd per share)	$ 0.0001	$ 0.0001
Preferred stock authorized (in shares)	5,000,000	5,000,000
Preferred stock issued (in shares)	0	0
Preferred stock outstanding (in shares)	0	0
Common stock par value (in usd per share)	$ 0.0001	$ 0.0001
Common stock authorized (in shares)	200,000,000	200,000,000
Common stock issued (in shares)	39,107,048	31,515,074
Common stock outstanding (in shares)	39,107,048	31,433,731

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2023

Income Tax Disclosure [Abstract]

Schedule of Effective Income Tax Rate Reconciliation

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


	Year Ended December 31,
	2023		2022
Income tax computed at federal statutory rate	21.0	%	21.0	%
State taxes	9.4		8.3
Change in valuation allowance	(12.4)		(30.4)
R&D credit carryovers	4.5		2.4

Stock-based compensation	(3.0)		(1.5)
Permanent differences	(0.6)		0.2
Section 382 net operating loss adjustments	(20.2)		0.0
Other	1.3		0.0
Effective income tax rate	0.0	%	0.0	%

Schedule of Deferred Tax Assets and Liabilities

The Company’s deferred tax assets and liabilities consist of the following:


	As of December 31,
	2023			2022
	(in thousands)
Deferred tax assets:
Net operating losses	$	23,873		$	26,234
Tax credit carryforwards	3,168			3,819
Lease liability	3,645			4,180
Other capitalized costs—net of amortization	95			103
Reserves and accruals	1,295			950
Stock-based compensation	2,021			1,448
Capitalized research and experimental expenditures—net of amortization	16,162			9,474
Deferred tax assets	50,259		—	46,208
Valuation allowance	(47,058)			(42,417)
Deferred tax assets recognized	3,201		—	3,791
Deferred tax liabilities:
Right of use asset	(1,993)			(2,358)
Fixed assets and depreciation	(1,208)			(1,433)


Deferred tax liabilities	(3,201)			(3,791)
Net deferred taxes	$	—		$	—

Defined Contribution Benefit Plan	12 Months Ended
Defined Contribution Benefit Plan	Dec. 31, 2023
Retirement Benefits [Abstract]
Defined Contribution Benefit Plan	13. Defined Contribution Benefit Plan The Company sponsors a defined contribution benefit 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 contribute a portion of their annual compensation, subject to statutory limitations. The Company matches 50% of each participant’s contribution up to a maximum of 6% of such participant’s eligible compensation paid in a calendar year. During each of the years ended December 31, 2023 and 2022, the Company recognized expense of $0.2 million related to matching contributions.

Basis of Presentation and Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2023

Accounting Policies [Abstract]

Basis of Presentation and Summary of Significant Accounting Policies

2. 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

Use of Estimates

Fair Value of Financial Instruments

assumptions in fair value measurements, ASC 820 establishes a three-tiered fair value hierarchy that distinguishes between the following:

•Level 1 - Observable inputs such as quoted prices (unadjusted) in active markets for identical assets or liabilities.

Cash and Cash Equivalents and Restricted Cash and Cash Equivalents

Property and Equipment


Laboratory equipment			5 years
Furniture and office equipment			5 years
Computer equipment			3 years
Leasehold improvements			Shorter of lease term or useful life of asset

Costs for property and equipment not yet placed into service are classified as construction in progress and depreciated in accordance with the above guidelines once placed into service.

Impairment of Long-lived Assets

estimated discounted cash flows expected to be generated from the long-lived assets. The Company has not recorded any material impairment charges during the years ended December 31, 2023 or 2022.

Leases

All of the Company’s leases are classified as operating leases. Operating lease expense is recognized over the lease term using the straight-line method.

Revenue Recognition

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

Intellectual Property Expenses

Stock-based Compensation

Debt Issuance Costs

Equity Issuance Costs

Income Taxes

Comprehensive Loss

Basic and Diluted Net Loss per Common Share

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 and cash equivalents are primarily held with three reputable financial institutions in the United States. 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

Subsequent Events

Income Taxes -Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets:
Net operating losses	$ 23,873	$ 26,234
Tax credit carryforwards	3,168	3,819
Lease liability	3,645	4,180
Other capitalized costs—net of amortization	95	103
Reserves and accruals	1,295	950
Stock-based compensation	2,021	1,448
Capitalized research and experimental expenditures—net of amortization	16,162	9,474
Deferred tax assets	50,259	46,208
Valuation allowance	(47,058)	(42,417)
Deferred tax assets recognized	3,201	3,791
Deferred tax liabilities:
Right of use asset	(1,993)	(2,358)
Fixed assets and depreciation	(1,208)	(1,433)
Deferred tax liabilities	(3,201)	(3,791)
Net deferred taxes	$ 0	$ 0

Income Taxes

12 Months Ended

Dec. 31, 2023

Income Tax Disclosure [Abstract]

Income Taxes

11. Income Taxes

During the years ended December 31, 2023 and 2022, 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 expense (benefit) computed using the federal statutory income tax rate to the Company’s effective income tax rate is as follows:


	Year Ended December 31,
	2023		2022
Income tax computed at federal statutory rate	21.0	%	21.0	%
State taxes	9.4		8.3
Change in valuation allowance	(12.4)		(30.4)
R&D credit carryovers	4.5		2.4

Stock-based compensation	(3.0)		(1.5)
Permanent differences	(0.6)		0.2
Section 382 net operating loss adjustments	(20.2)		0.0
Other	1.3		0.0
Effective income tax rate	0.0	%	0.0	%

The Company’s deferred tax assets and liabilities consist of the following:


	As of December 31,
	2023			2022
	(in thousands)
Deferred tax assets:
Net operating losses	$	23,873		$	26,234
Tax credit carryforwards	3,168			3,819
Lease liability	3,645			4,180
Other capitalized costs—net of amortization	95			103
Reserves and accruals	1,295			950
Stock-based compensation	2,021			1,448
Capitalized research and experimental expenditures—net of amortization	16,162			9,474
Deferred tax assets	50,259		—	46,208
Valuation allowance	(47,058)			(42,417)
Deferred tax assets recognized	3,201		—	3,791
Deferred tax liabilities:
Right of use asset	(1,993)			(2,358)
Fixed assets and depreciation	(1,208)			(1,433)


Deferred tax liabilities	(3,201)			(3,791)
Net deferred taxes	$	—		$	—

The Tax Cuts and Jobs Act (“TCJA”) requires taxpayers to capitalize and amortize research and experimental (“R&E”) expenditures under Section 174 for tax years beginning after December 31, 2021. This rule became effective for the Company during 2022 and resulted in the capitalization of R&E expenditures of $27.9 million and $36.1 million during the years ended December 31, 2023 and 2022, respectively. The Company amortizes these costs for tax purposes over 5 years for research and development (“R&D”) performed in the U.S. and over 15 years for R&D performed outside the U.S.

The Company evaluated the positive and negative evidence bearing upon its ability to realize the deferred tax assets as of December 31, 2023 and 2022. Management considered the Company’s cumulative net losses and concluded as of December 31, 2023 and 2022, 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, 2023 and 2022. The valuation allowance increased by $4.6 million during the year ended December 31, 2023 primarily due to an increase in deferred tax assets related to capitalized R&E expenditures, and as the result of operating losses generated with no corresponding financial statement benefit. These increases were offset by a decrease in deferred tax assets as the result of the Company’s Section 382 study that was completed for the period of January 22, 2018, through December 31, 2022, which resulted in limitations being identified on historical net operating losses and research and development tax credits. The valuation allowance increased by $16.3 million during the year ended December 31, 2022. primarily due to the change in the

tax regulation described above resulting in the capitalization of R&E expenditures that previously were fully deductible in the year incurred, and as a result of operating losses generated with no corresponding financial statement benefit.

The Company has incurred net operating losses since inception. As of December 31, 2023 and 2022, the Company had federal net operating loss carryforwards of $96.6 million and $92.1 million, respectively, available to reduce future federal taxable income. The carryforwards generated from losses incurred prior to January 1, 2018 will expire in 2037. The carryforwards generated from losses incurred after December 31, 2017 do not expire. As of December 31, 2023, federal net operating loss carryforwards includes $96.5 million of carryforwards that do not expire. The TCJA enacted on December 22, 2017 limits a taxpayer’s ability to utilize a net operating loss deduction in a year to 80% taxable income for federal net operating losses arising in tax years beginning after December 31, 2017. As of December 31, 2023 and 2022, the Company had state net operating loss carryforwards of $44.9 million and $86.1 million, respectively, available to reduce future state taxable income, which expire at various dates beginning in 2037.

As of December 31, 2023 and 2022, the Company had federal research and development tax credit carryforwards of $2.3 million and $2.6 million, respectively, available to reduce future federal tax liabilities, which expire at various dates beginning in 2042. The Company also had state research and development tax credit carryforwards as of December 31, 2023 and 2022 of $0.9 million and $1.2 million, respectively, available to reduce future state tax liabilities, which expire at various dates beginning in 2037.

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 completed a Section 382 study for the period of January 22, 2018, through December 31, 2022 and identified three ownership changes that occurred on June 10, 2019, August 2, 2019, and August 31, 2022 for Section 382 purposes. As the Company experienced these ownership changes, all pre-change net operating loss and research and development tax credit carryforwards are subject to limitation. Due to the unlimited carryover period for net operating losses generated after December 31, 2017, none of the Company’s federal net operating losses will expire unused. A portion of the Company’s state net operating losses, and federal and state research and development tax credits are expected to expire unused. The Company has analyzed the impact of these limitations on its attributes and included the impact of these limitations in its deferred tax assets as of December 31, 2023.

The Company has not recorded any reserves for uncertain tax positions as of December 31, 2023 and 2022. The Company has conducted a study of research and development tax credit for tax years 2018 through 2020. 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 statute of limitations for assessment by the Internal Revenue Service, or IRS, and state tax authorities is closed for tax years prior to 2020, although carryforward attributes that were generated prior to 2020 may still be adjusted upon examination by the IRS or state tax authorities if they either have been or will be used in a future period.

- 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
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480990/946-20-50-13

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
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-Name Accounting Standards Codification
-Section S99
-Paragraph 1
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-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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-Topic 740
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Reference 10: http://www.xbrl.org/2003/role/disclosureRef
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-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482603/740-30-50-2

+ Details

Insider Trading Arrangements	3 Months Ended
Insider Trading Arrangements	Dec. 31, 2023
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Property and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 11,128	$ 10,394
Less: accumulated depreciation	(3,170)	(1,406)
Total property and equipment, net	7,958	8,988
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	7,971	7,971
Laboratory equipment
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	2,339	1,635
Computer equipment
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	512	418
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	306	264
Construction in progress
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 0	$ 106

Income Taxes - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
Income Taxes - Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Operating Loss Carryforwards [Line Items]
Current income tax expenses	$ 0	$ 0
Deferred income tax expenses (benefits)	0	0
Capitalized research and experimentation expenses	27,900	36,100
Valuation allowance, deferred tax asset, increase amount	(4,600)	16,300
Deferred tax assets, operating loss carryforwards not subject to expiration	96,500
Domestic Tax Authority
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	96,600	92,100
Domestic Tax Authority \| Research Tax Credit Carryforward
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	2,300	2,600
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	44,900	86,100
Tax credit carryforwards	$ 900	$ 1,200
UNITED STATES \| Research And Experimentation
Operating Loss Carryforwards [Line Items]
Amortization of R&E expenses, period	5 years
Non-US \| Research And Experimentation
Operating Loss Carryforwards [Line Items]
Amortization of R&E expenses, period	15 years

Common and Preferred Stock

12 Months Ended

Dec. 31, 2023

Equity [Abstract]

Common and Preferred Stock

8. Common and Preferred Stock

Common Stock

The Company is authorized to issue 200,000,000 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, 2023, no dividends on common stock had been declared by the Company.

On May 10, 2022, the Company entered into a Sales Agreement (the “Sales Agreement”) with Leerink Partners, LLC (“Leerink Partners”), formerly known as SVB Securities LLC, pursuant to which the Company is entitled to offer and sell shares of its common stock (the “ATM Offering”). The Sales Agreement provides that Leerink Partners will be entitled to a sales commission equal to 3.0% of the gross sales price per share of all shares sold under the ATM Offering. In accordance with the terms of the Sales Agreement and a sales agreement prospectus included in the registration statement on Form S-3 that the Company filed with the SEC on May 10, 2022, which was declared effective on May 20, 2022, the Company was initially entitled to offer and sell shares of its common stock having an aggregate offering price of up to $50.0 million in the ATM Offering. During the year ended December 31, 2023, the Company sold an aggregate of 7,431,981 shares under the ATM Offering at an average price of $2.56 per share for net proceeds of $18.3 million after deducting sales commissions and offering

expenses. During the year ended December 31, 2022, the Company sold an aggregate of 3,827,567 shares under the ATM Offering at an average price of $4.36 per share for net proceeds of $15.7 million after deducting sales commissions and offering expenses.

On February 9, 2024, the Company filed a prospectus supplement (the “Prospectus Supplement”) under its shelf registration statement for the offer and sale of shares of its common stock having an aggregate offering price of up to $25.0 million. Following the Company’s filing of the Prospectus Supplement, the Company is entitled to offer and sell shares of its common stock with an offering price of up to $75.0 million pursuant to the Sales Agreement.

During the period beginning January 1, 2024 and ending March 1, 2024, the Company sold 3,629,060 shares of its common stock under the ATM Offering, for gross proceeds of $17.7 million before deducting sales commissions and issuance costs.

The Company had reserved shares of common stock for issuance as follows:


	As of December 31,
	2023	2022
Shares reserved for exercises of outstanding stock options	5,700,070	5,244,121
Shares reserved for vesting of restricted stock units	361,500	322,725
Shares reserved for exercises of warrants	58,904	58,904
Shares reserved for issuance under the 2021 Employee Stock Purchase Plan	507,113	244,000
Shares reserved for future issuance under the 2021 Stock Incentive Plan	1,911,660	938,587
Total shares reserved for future issuance	8,539,247	6,808,337

Preferred Stock

The Company is authorized to issue 5,000,000 shares of undesignated preferred stock in one or more series. As of December 31, 2023, no shares of preferred stock were issued or outstanding.

- Definition

The entire disclosure for equity.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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-Section 50
-Paragraph 14
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-14

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481062/946-235-50-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481062/946-235-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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-Name Accounting Standards Codification
-Section S99
-Paragraph 1
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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-Paragraph 1
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Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
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-URI https://asc.fasb.org//505/tableOfContent

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
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Reference 12: http://www.xbrl.org/2003/role/disclosureRef
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-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
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-Paragraph 13
-Subparagraph (i)
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-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
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Reference 15: http://www.xbrl.org/2003/role/disclosureRef
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Reference 16: http://www.xbrl.org/2003/role/disclosureRef
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Reference 17: http://www.xbrl.org/2003/role/disclosureRef
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Reference 18: http://www.xbrl.org/2003/role/disclosureRef
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Reference 19: http://www.xbrl.org/2003/role/disclosureRef
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-Paragraph 18
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-18

+ Details

Stock-based Compensation - Stock Option Activity (Details) - Stock options $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($) $ / shares shares
Number of Options
Outstanding at beginning of period (in shares) \| shares	5,244,121
Granted (in shares) \| shares	1,618,780
Exercised (in shares) \| shares	(2,956)
Cancelled (in shares) \| shares	(1,159,875)
Outstanding at end of period (in shares) \| shares	5,700,070
Exercisable at end of period (shares) \| shares	3,169,212
Weighted-Average Exercise Price per Share
Weighted-Average Exercise Price - Outstanding at beginning of period (in usd per share) \| $ / shares	$ 7.86
Weighted-Average Exercise Price - Granted (in usd per share) \| $ / shares	2.16
Weighted-Average Exercise Price - Exercised (in usd per share) \| $ / shares	1.98
Weighted-Average Exercise Price - Cancelled (in usd per share) \| $ / shares	4.68
Weighted-Average Exercise Price - Outstanding at end of period (in usd per share) \| $ / shares	6.89
Weighted-Average Exercise Price - Exercisable at end of period (in usd per share) \| $ / shares	$ 7.60
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Additional Disclosures [Abstract]
Weighted Average Remaining Contractual Life - Outstanding	7 years 9 months 21 days
Weighted Average Remaining Contractual Life - Exercisable	7 years 5 months 4 days
Outstanding, Aggregate Intrinsic Value \| $	$ 3.6
Exercisable, Aggregate Intrinsic Value \| $	$ 1.5

Net Loss Attributable to Common Stockholders per Share (Tables)

12 Months Ended

Dec. 31, 2023

Earnings Per Share [Abstract]

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


	December 31,
	2023	2022
Outstanding stock options	5,700,070	5,244,121
Unvested RSUs	361,500	322,725
Warrants to purchase common stock	58,904	58,904
Common stock to be issued under the 2021 ESPP	22,611	29,332
Unvested RSAs	—	81,343
Total	6,143,085	5,736,425

Stock-based Compensation - Restricted Stock Award Activity (Details) - $ / shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Unvested RSAs \| 2017 Stock Incentive Plan
Shares/Units
Unvested at beginning of period (in shares)	81,343
Granted (in shares)	0
Vested (in shares)	(81,343)
Forfeited (in shares)	0
Unvested at end of period (in shares)	0	81,343
Weighted-Average Grant Date Fair Value Per Share
Weighted Average Grant Date Fair Value - Unvested at beginning of period (in usd per share)	$ 1.38
Weighted Average Grant Date Fair Value - Granted (in usd per share)	0
Weighted Average Grant Date Fair Value - Vested (in usd per share)	1.38
Weighted Average Grant Date Fair Value - Forfeited (in usd per share)	0
Weighted Average Grant Date Fair Value - Unvested at end of period (in usd per share)	$ 0	$ 1.38
RSU Activity
Shares/Units
Vested (in shares)		0
RSU Activity \| 2021 Stock Incentive Plan
Shares/Units
Unvested at beginning of period (in shares)	322,725
Granted (in shares)	150,000
Vested (in shares)	(105,000)
Forfeited (in shares)	(6,225)
Unvested at end of period (in shares)	361,500	322,725
Weighted-Average Grant Date Fair Value Per Share
Weighted Average Grant Date Fair Value - Unvested at beginning of period (in usd per share)	$ 4.32
Weighted Average Grant Date Fair Value - Granted (in usd per share)	2.45
Weighted Average Grant Date Fair Value - Vested (in usd per share)	2.96
Weighted Average Grant Date Fair Value - Forfeited (in usd per share)	4.97
Weighted Average Grant Date Fair Value - Unvested at end of period (in usd per share)	$ 3.92	$ 4.32

Pay vs Performance Disclosure - USD ($) $ in Thousands	12 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Pay vs Performance Disclosure
Net loss	$ (37,368)	$ (53,810)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

+ Details

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 134,343	$ 129,315
Prepaid expenses and other current assets	2,677	3,957
Other receivables	1,350	6,928
Total current assets	138,370	140,200
Property and equipment, net	7,958	8,988
Restricted cash and cash equivalents, net of current portion	21,023	1,214
Operating lease right of use asset	6,888	8,463
Other assets	594	1,380
Total assets	174,833	160,245
Current liabilities:
Accounts payable	1,336	1,221
Accrued expenses and other current liabilities	8,860	14,152
Operating lease liability, current	1,608	2,084
Deferred revenue, current	907	6,532
Note payable, current	6,667	0
Total current liabilities	19,378	23,989
Operating lease liability, net of current portion	10,992	12,600
Deferred revenue, net of current portion	433	1,128
Note payable, net of discount, issuance costs, and current portion	32,656	0
Other liabilities	0	191
Total liabilities	63,459	37,908
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $0.0001 par value, 5,000,000 shares authorized as of December 31, 2023 and December 31, 2022; no shares issued or outstanding as of December 31, 2023 and December 31, 2022	0	0
Common stock, $0.0001 par value, 200,000,000 shares authorized as of December 31, 2023 and December 31, 2022; 39,107,048 and 31,515,074 shares issued as of December 31, 2023 and December 31, 2022, respectively; 39,107,048 and 31,433,731 shares outstanding as of December 31, 2023 and December 31, 2022, respectively	4	3
Additional paid-in capital	455,443	429,039
Accumulated deficit	(344,073)	(306,705)
Total stockholders’ equity	111,374	122,337
Total liabilities and stockholders’ equity	$ 174,833	$ 160,245

Cover - USD ($)	12 Months Ended
Cover - USD ($)	Dec. 31, 2023	Mar. 01, 2024	Jun. 30, 2023
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2023
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	001-40366
Entity Registrant Name	WEREWOLF THERAPEUTICS, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	82-3523180
Entity Address, Address Line One	200 Talcott Ave
Entity Address, Address Line Two	2nd Floor
Entity Address, City or Town	Watertown
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02472
City Area Code	617
Local Phone Number	952‑0555
Title of 12(b) Security	Common Stock, $0.0001 par value per share
Trading Symbol	HOWL
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
ICFR Auditor Attestation Flag	false
Document Financial Statement Error Correction	false
Entity Shell Company	false
Entity Public Float			$ 67,355,166
Entity Common Stock, Shares Outstanding		42,737,191
Documents Incorporated by Reference	Portions of the registrant’s Definitive Proxy Statement on Schedule 14A relating to its 2024 Annual Meeting of Stockholders to be filed within 120 days of the registrant’s fiscal year ended December 31, 2023 are incorporated by reference into Part III of this Annual Report on Form 10-K to the extent stated herein.
Entity Central Index Key	0001785530
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Amendment Flag	false

Basis of Presentation and Summary of Significant Accounting Policies - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($) operating_segment institution	Dec. 31, 2022 USD ($)
Accounting Policies [Abstract]
Number of operating segments \| operating_segment	1
Restricted cash and cash equivalents \| $	$ 21.2	$ 1.2
Number of financial institutions \| institution	3

Property and Equipment, Net

12 Months Ended

Dec. 31, 2023

Property, Plant and Equipment [Abstract]

Property and Equipment, Net

5. Property and Equipment, Net

Property and equipment, net was comprised as follows:


	December 31,
	2023		2022
	(in thousands)
Leasehold improvements	$	7,971	$	7,971
Laboratory equipment	2,339		1,635
Computer equipment	512		418
Furniture and fixtures	306		264
Construction in progress	—		106
Total property and equipment, gross	11,128		10,394
Less: accumulated depreciation	(3,170)		(1,406)
Total property and equipment, net	$	7,958	$	8,988

Stock-based Compensation - Narrative (Details) $ / shares in Units, $ in Thousands			12 Months Ended
	Dec. 31, 2023 USD ($) shares	Apr. 30, 2021 shares	Dec. 31, 2023 USD ($) $ / shares shares	Dec. 31, 2022 USD ($) $ / shares shares	Dec. 31, 2021
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Common stock available for issuance (in shares)	8,539,247		8,539,247	6,808,337
Share-based compensation expense not yet recognized \| $	$ 9,900		$ 9,900
Total stock-based compensation \| $			8,008	$ 7,400
Unvested RSAs \| 2017 Stock Incentive Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Aggregate fair value of awards that vested \| $			$ 200	$ 1,200
Vested (in shares)			81,343
Unvested RSUs
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Aggregate fair value of awards that vested \| $			$ 200
Vested (in shares)				0
Unvested RSUs \| 2021 Stock Incentive Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-based compensation expense not yet recognized \| $	$ 600		$ 600
Share-based compensation not yet recognized, recognition period			7 months 17 days
Vested (in shares)			105,000
Performance Shares
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Options granted (shares)				883,352
Weighted-average grant date fair value of awards (in usd per share) \| $ / shares				$ 3.36
Total stock-based compensation \| $			$ 0	$ 0
Shares reserved for future issuance under the 2021 Stock Incentive Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-based compensation not yet recognized, recognition period			2 years
Options granted (shares)			1,618,780
Weighted-average grant date fair value of awards (in usd per share) \| $ / shares			$ 1.56	$ 5.98
Aggregate intrinsic fair value of options exercised \| $			$ 0	$ 400
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
Common stock available for issuance (in shares)	1,911,660		1,911,660
2021 Stock Incentive Plan \| Unvested RSAs
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Common stock authorized to be issued (in shares)		477,725
2021 Stock Employee Stock Purchase Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Offering period					6 months
Purchase period					6 months
ESPP purchase price, percent					0.85
Common Stock
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Common stock authorized to be issued (in 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 (in shares)		2,843,116
Maximum number of shares to be added annually, as a percentage of outstanding shares (in shares)	2,956,150
Common Stock \| 2017 Stock Incentive Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Common stock authorized to be issued (in shares)		31,884
Common Stock \| 2021 Stock Employee Stock Purchase Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Shares purchased by employees (in shares)			52,037	0
Shares purchased by employees, value \| $			$ 100

Financial Instruments and Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2023

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, 2023 were as follows:


	Level 1		Level 2		Level 3		Total
	(in thousands)
Assets:
Money market funds	$	149,294	$	—	$	—	$	149,294
Total assets	$	149,294	$	—	$	—	$	149,294

Assets and liabilities measured at fair value on a recurring basis as of December 31, 2022 were as follows:


	Level 1		Level 2		Level 3		Total
	(in thousands)
Assets:
Money market funds	$	128,812	$	—	$	—	$	128,812
Total assets	$	128,812	$	—	$	—	$	128,812
Liabilities
Success payment liability	$	—	$	—	$	570	$	570
Total liabilities	$	—	$	—	$	570	$	570

Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation

The following table reconciles the change in fair value of the success payment liability during the years ended December 31, 2023 and 2022 based on Level 3 inputs (in thousands):


Balance at December 31, 2021	$	—
Additions	1,125
Change in fair value	(555)
Balance at December 31, 2022	570

Change in fair value	1,030
Payment at Success Fee Event	(1,600)
Balance at December 31, 2023	$	—

Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation

Management determined the fair value of the success payment liability immediately prior to the completion of the Success Fee Event and as of December 31, 2022 using the following significant unobservable inputs:


	Immediately prior to completion of the Success Fee Event		As of December 31, 2022
Probability of Success Fee Event	100	%	75	%
Expected term (in years)	0.00		0.33 - 0.75
Discount rate	—	%	7.1	%

Consolidated Statements of Stockholders’ Equity (Parentheticals) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Market Offering
Issuance costs	$ 762	$ 956

Financial Instruments and Fair Value Measurements

12 Months Ended

Dec. 31, 2023

Fair Value Disclosures [Abstract]

Financial Instruments and Fair Value Measurements

4. Financial Instruments and Fair Value Measurements

The Company’s assets that are required to be measured at fair value on a recurring basis consist of money market funds, classified as cash, cash equivalents and restricted cash and cash equivalents on the Company’s consolidated balance sheets as of December 31, 2023 and 2022 . The Company’s liabilities that were required to be measured at fair value on a recurring basis consist of a success payment liability pursuant to the Loan Agreement with PWB (see Note 7, Term Loan) as of December 31, 2022. The Company did not have any liabilities that are required to be measured at fair value on a recurring basis as of December 31, 2023.

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, 2023 were as follows:


	Level 1		Level 2		Level 3		Total
	(in thousands)
Assets:
Money market funds	$	149,294	$	—	$	—	$	149,294
Total assets	$	149,294	$	—	$	—	$	149,294

Assets and liabilities measured at fair value on a recurring basis as of December 31, 2022 were as follows:


	Level 1		Level 2		Level 3		Total
	(in thousands)
Assets:
Money market funds	$	128,812	$	—	$	—	$	128,812
Total assets	$	128,812	$	—	$	—	$	128,812
Liabilities
Success payment liability	$	—	$	—	$	570	$	570
Total liabilities	$	—	$	—	$	570	$	570

The success payment liability was included within accrued expenses and other current liabilities in the accompanying consolidated balance sheet as of December 31, 2022. There were no changes in valuation techniques during the year ended December 31, 2023.

Success Payment Liability

The Company was obligated to pay to PWB a one-time success payment of up to $1.6 million upon the occurrence of the Company achieving certain conditions defined in the Loan Agreement. The Success Fee Event (as defined in the Loan Agreement) occurred during the second quarter of 2023, resulting in the immediate payment in full of the required Success Fee (as defined in Note 7 below).

The following table reconciles the change in fair value of the success payment liability during the years ended December 31, 2023 and 2022 based on Level 3 inputs (in thousands):


Balance at December 31, 2021	$	—
Additions	1,125
Change in fair value	(555)
Balance at December 31, 2022	570

Change in fair value	1,030
Payment at Success Fee Event	(1,600)
Balance at December 31, 2023	$	—

The success payment liability is stated at fair value and is considered Level 3 because its fair value measurement is based, in part, on significant inputs not observed in the market. Upon completion of the Success Fee Event, the Company paid the total $1.6 million success payment and removed the corresponding success payment liability. The Company remeasured the success payment liability at each reporting date and immediately prior to the Success Fee Event. Changes in the fair value of the success payment liability are included in other (expense) income, net in the accompanying consolidated statements of operations.

The fair value of the success payment liability was determined using a probability weighted expected return method, in which the probability and timing of potential future events was considered in order to estimate the fair value of the success payment liability as of each valuation date. Management determined the fair value of the success payment liability immediately prior to the completion of the Success Fee Event and as of December 31, 2022 using the following significant unobservable inputs:


	Immediately prior to completion of the Success Fee Event		As of December 31, 2022
Probability of Success Fee Event	100	%	75	%
Expected term (in years)	0.00		0.33 - 0.75
Discount rate	—	%	7.1	%

- 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

Jazz Collaboration and License Agreement (Tables)

12 Months Ended

Dec. 31, 2023

Business Combination and Asset Acquisition [Abstract]

Contract with Customer, Contract Asset, Contract Liability, and Receivable

The following table presents the activity in the Company’s contract liabilities during the year ended December 31, 2023:


	Beginning of Period Balance		Additions		Reductions		End of Period Balance
	(in thousands)





Contract liabilities:
Deferred revenue	$	7,660	$	5,000	$	(11,320)	$	1,340
Total contract liabilities	$	7,660	$	5,000	$	(11,320)	$	1,340

The following table presents the activity in the Company’s contract liabilities during the year ended December 31, 2022:


	Beginning of Period Balance		Additions		Reductions		End of Period Balance
	(in thousands)





Contract liabilities:
Deferred revenue	$	—	$	15,000	$	(7,340)	$	7,660
Total contract liabilities	$	—	$	15,000	$	(7,340)	$	7,660

Income Taxes - Schedule of Effective Income Tax Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
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	9.40%	8.30%
Change in valuation allowance	(12.40%)	(30.40%)
R&D credit carryovers	4.50%	2.40%
Stock-based compensation	(3.00%)	(1.50%)
Permanent differences	(0.006)	0.002
Section 382 net operating loss adjustments	(0.202)	0.000
Other	1.30%	0.00%
Effective income tax rate	(0.00%)	(0.00%)

Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Payables and Accruals [Abstract]
Employee compensation and benefits	$ 3,627	$ 3,135
Manufacturing	2,772	6,674
Contract research	1,049	2,990
Professional fees	655	613
Accrued interest	310	0
Success payment liability	0	570
Other	447	170
Total accrued expenses and other current liabilities	$ 8,860	$ 14,152

Property and Equipment, Net (Tables)

12 Months Ended

Dec. 31, 2023

Property, Plant and Equipment [Abstract]

Schedule of Property, Plant and Equipment

Property and equipment are depreciated over the following periods:


Laboratory equipment			5 years
Furniture and office equipment			5 years
Computer equipment			3 years
Leasehold improvements			Shorter of lease term or useful life of asset

Property and equipment, net was comprised as follows:


	December 31,
	2023		2022
	(in thousands)
Leasehold improvements	$	7,971	$	7,971
Laboratory equipment	2,339		1,635
Computer equipment	512		418
Furniture and fixtures	306		264
Construction in progress	—		106
Total property and equipment, gross	11,128		10,394
Less: accumulated depreciation	(3,170)		(1,406)
Total property and equipment, net	$	7,958	$	8,988

Related Parties	12 Months Ended
Related Parties	Dec. 31, 2023
Related Party Transactions [Abstract]
Related Parties	12. Related Parties In May 2022, the Company entered into a sublease agreement with Crossbow, for which entities affiliated with MPM Capital (“MPM Capital”) are also beneficial owners, to sublease the entirety of its office and laboratory space in Cambridge, Massachusetts. Luke Evnin, Ph.D., the chair of the Company’s board of directors, co-founded MPM Capital and serves as Managing Director of MPM Capital. Briggs Morrison, who serves on the Company’s board of directors, serves as Executive Partner of MPM Capital and Chief Executive Officer of Crossbow. The term of the sublease agreement commenced in June 2022 and ends in March 2024, with no option to extend (see Note 10, Commitments and Contingencies). The Company received cash payments under its sublease of $1.6 million and $0.8 million during the years ended December 31, 2023 and 2022, respectively. In addition, the Company received $0.2 million from Crossbow in June 2022 as a security deposit. The security deposit is included within accrued expenses and other current liabilities in the accompanying consolidated balance sheet as of December 31, 2023 and is included within other liabilities in the accompanying consolidated balance sheet as of December 31, 2022.

- Definition

The entire disclosure for related party transactions. Examples of related party transactions include transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners; and (d) affiliates.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480990/946-20-50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Term Loan - Narrative (Details) - USD ($)	1 Months Ended	3 Months Ended	12 Months Ended
Term Loan - Narrative (Details) - USD ($)	Apr. 30, 2022	Jun. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Outstanding borrowings			$ 40,000,000
Floating rate spread in effect (greater than) (percent)	4.50%
Interest expense			3,139,000	$ 0
Success fee liability paid		$ 1,600,000
Proceeds from at the market offering of common stock, net of issuance costs			18,329,000	15,740,000
Prime Rate
Debt Instrument [Line Items]
Floating rate spread in effect (greater than) (percent)	0.50%
Term loan
Debt Instrument [Line Items]
Outstanding borrowings				0
Interest expense			2,900,000	$ 0
Term loan \| In FY 2021
Debt Instrument [Line Items]
Delayed draw fee	$ 200,000
Success fee (percent)	2.00%
Term loan \| After FY 2021
Debt Instrument [Line Items]
Delayed draw fee	$ 400,000
Success fee (percent)	4.00%
Tranche I Loan \| Term loan
Debt Instrument [Line Items]
Term loan available	$ 20,000,000
Tranche II Loan \| Term loan
Debt Instrument [Line Items]
Term loan available	$ 20,000,000
Term Loans \| Term loan
Debt Instrument [Line Items]
Outstanding borrowings			39,323,000
Drawings on term loans			40,000,000
Default payment fee (percent)	5.00%
Maximum annual capital expenditures	1.25
Proceeds from at the market offering of common stock, net of issuance costs			50,000,000
Non-current restricted cash			$ 20,000,000

Term Loan - Schedule of Total Principal Payments Maturities (Details) $ in Thousands	Dec. 31, 2023 USD ($)
Principal Payments
2024	$ 6,667
2025	20,000
2026	13,333
Net carrying amount of note payable	$ 40,000

- Definition

Amount, after deduction of unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation.

+ References + Details

Accrued Expenses and Other Current Liabilities (Tables)

12 Months Ended

Dec. 31, 2023

Payables and Accruals [Abstract]

Accrued Expenses

Accrued expenses and other current liabilities were comprised as follows:


	December 31,
	2023		2022
	(in thousands)
Employee compensation and benefits	$	3,627	$	3,135
Manufacturing	2,772		6,674
Contract research	1,049		2,990
Professional fees	655		613
Accrued interest	310		—
Success payment liability	—		570
Other	447		170
Total accrued expenses and other current liabilities	$	8,860	$	14,152

Jazz Collaboration and License Agreement - Contract with Customer, Contract Asset, Contract Liability, and Receivable (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Contract liabilities:
Deferred revenue liabilities, beginning balance	$ 7,660	$ 0
Additions	5,000	15,000
Reductions	(11,320)	(7,340)
Deferred revenue liabilities, ending balance	$ 1,340	$ 7,660

Term Loan (Tables)

12 Months Ended

Dec. 31, 2023

Debt Disclosure [Abstract]

Schedule of Long-Term Debt Instruments

The outstanding notes payable balance under the Term Loans consists of the following:


	December 31, 2023
	(in thousands)
Note payable	$	40,000
Unamortized debt discount and issuance costs	(677)
Net carrying amount of note payable	39,323
Less: current portion of note payable	(6,667)
Note payable, net, less current portion	$	32,656

Schedule of Total Principal Payments Maturities

The following table presents the total principal payments scheduled to become due during each of the years ended December 31:


	Principal Payments
	(in thousands)
2024	$	6,667
2025	20,000
2026	13,333
	$	40,000

- Definition

Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer.

+ References

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+ Details

Term Loan - Schedule of Long-Term Debt Instruments (Details) - USD ($)	Dec. 31, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Net carrying amount of note payable	$ 40,000,000
Term loan
Debt Instrument [Line Items]
Net carrying amount of note payable		$ 0
Term Loans \| Term loan
Debt Instrument [Line Items]
Note payable	40,000,000
Unamortized debt discount and issuance costs	(677,000)
Net carrying amount of note payable	39,323,000
Less: current portion of note payable	(6,667,000)
Note payable, net, less current portion	$ 32,656,000

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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+ Details

- Definition

Amount, after deduction of unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation.

+ References + Details

Jazz Collaboration and License Agreement - Narrative (Details) - USD ($)	1 Months Ended		12 Months Ended
	Jul. 31, 2023	Apr. 30, 2022	Dec. 31, 2023	Dec. 31, 2022
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Collaboration revenue			$ 19,943,000	$ 16,401,000
Cumulative catch-up revenue			4,200,000
Research and development			41,776,000	53,761,000
Revenue recognized that was included in prior period deferred revenue			6,700,000	0
Unbilled Accounts Receivables
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Contract liabilities:			400,000	4,100,000
Accounts Receivable
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Contract liabilities:			900,000	2,800,000
Jazz Collaboration Agreement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Non-refundable upfront cash payment received		$ 15,000,000
Collaboration revenue	$ 5,000,000
Development and regulatory milestones (up to)			515,000,000
Sales-Based Milestones (up to)			$ 740,000,000
Transaction price		32,300,000
Estimated future reimbursable costs		$ 17,300,000
Collaboration agreement, term			2 years 3 months 18 days
Research and development			$ 8,600,000	$ 9,100,000

Related Parties (Details) - USD ($) $ in Millions	12 Months Ended
Related Parties (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Related Party Transactions [Abstract]
Sublease cash payments received	$ 1.6	$ 0.8
Security deposit liability	$ 0.2	$ 0.2