0001785530-26-000006 | 10-K | XBRL Viewer | Werewolf Therapeutics INC

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Financial Instruments and Fair Value Measurements - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	May 31, 2024	Dec. 31, 2025	Dec. 31, 2024
Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Change in fair value		$ 2,070	$ 1,621
Loan Agreement
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loan agreement, amount	$ 60,000
Conversion of outstanding principal	$ 5,000
Conversion price (in dollars per share)	$ 6.3182
Loan Agreement \| Minimum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Adjustment rate (percent)	9.99%
Loan Agreement \| Maximum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Adjustment rate (percent)	19.99%

Nature of Business	12 Months Ended
Nature of Business	Dec. 31, 2025
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Business	1. Nature of Business Werewolf Therapeutics, Inc. was incorporated in the state of Delaware in October 2017. As used throughout these consolidated financial statements, the terms “Werewolf,” “we,” “us,” and “our” refer to the business of Werewolf Therapeutics, Inc., and its wholly owned subsidiary. We are an innovative biopharmaceutical company pioneering the development of therapeutics engineered to stimulate the body’s immune system for the treatment of cancer and other immune mediated conditions. Our headquarters are located in Watertown, Massachusetts. Since inception, we have devoted substantially all of our efforts and financial resources to organizing and staffing the company; business planning; raising capital; developing and optimizing our platform technology; identifying potential product candidates; enhancing our intellectual property portfolio; undertaking research, preclinical studies, and clinical trials; and enabling manufacturing for our development programs. We are 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 our product development efforts are successful, it is uncertain when, if ever, we will realize significant revenue from product sales.

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Operating activities:
Net loss	$ (60,822)	$ (70,515)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	6,245	8,826
Depreciation expense	1,634	1,814
Non-cash interest expense	2,141	1,342
Non-cash lease expense	785	887
Loss on extinguishment of debt	0	553
Change in fair value of derivative liability	(2,070)	(1,621)
Changes in operating assets and liabilities:
Prepaid expenses and other assets	850	669
Other receivables	0	1,350
Accounts payable, accrued expenses and other liabilities	(7,498)	3,455
Deferred revenue	0	(1,340)
Operating lease liability	(1,557)	(1,608)
Net cash used in operating activities	(60,292)	(56,188)
Investing activities:
Purchases of property and equipment	0	(254)
Net cash used in investing activities	0	(254)
Financing activities:
Proceeds from at the market offering of common stock, net of issuance costs	5,939	23,576
Proceeds from drawdown of term loans	0	30,000
Payment of debt issuance costs	0	(673)
Repayment of term loan	0	(40,000)
Proceeds from issuances under Employee Stock Purchase Plan	89	142
Proceeds from stock option exercises	0	35
Net cash provided by financing activities	6,028	13,080
Net decrease in cash, cash equivalents and restricted cash and cash equivalents	(54,264)	(43,362)
Cash, cash equivalents and restricted cash and cash equivalents—beginning of period	112,215	155,577
Cash, cash equivalents and restricted cash and cash equivalents—end of period	57,951	112,215
Supplemental disclosure of cash flow information:
Cash paid for interest	3,133	3,358
Supplemental disclosure of non-cash investing and financing activities:
Issuance costs in accounts payable and accrued expenses	120	84
Fair value of derivative liability issued with term loan	$ 0	$ 4,450

Commitments and Contingencies - Summarizes The Lease Term and Discount Rate For Operating Leases (Details)	Dec. 31, 2025	Dec. 31, 2024
Commitments and Contingencies Disclosure [Abstract]
Weighted-average remaining lease term (years)	4 years 4 months 24 days	5 years 4 months 24 days
Weighted-average discount rate	8.00%	8.00%

Net Loss Attributable to Common Stockholders per Share - Common Stockholder (Details) - shares	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	10,040,240	7,761,286
Outstanding stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	9,954,872	7,634,937
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)	0	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)	85,368	67,445

Financial Instruments and Fair Value Measurements - Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation (Details) - Level 3 - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	May 31, 2024	Dec. 31, 2025	Dec. 31, 2024
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period		$ 2,829	$ 0
Fair value of derivative liability at issuance of term loan	$ 4,500	0	4,450
Change in fair value		(2,070)	(1,621)
Balance at end of period		$ 759	$ 2,829

Property and Equipment, Net

12 Months Ended

Dec. 31, 2025

Property, Plant and Equipment [Abstract]

Property and Equipment, Net

6. Property and Equipment, Net

Property and equipment, net was comprised as follows:


	December 31,
	2025		2024
	(in thousands)
Leasehold improvements	$	7,971	$	7,971
Laboratory equipment	2,485		2,485
Computer equipment	539		539
Furniture and fixtures	311		311

Total property and equipment, gross	11,306		11,306
Less: accumulated depreciation	(6,618)		(4,984)
Total property and equipment, net	$	4,688	$	6,322

Insider Trading Arrangements	3 Months Ended
Insider Trading Arrangements	Dec. 31, 2025
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

Financial Instruments and Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2025

Fair Value Disclosures [Abstract]

Assets Measured at Fair Value on a Recurring Basis

Assets and liabilities measured at fair value on a recurring basis as of December 31, 2025 were as follows:


	Level 1		Level 2		Level 3		Total
	(in thousands)
Assets:
Money market funds	$	56,548	$	—	$	—	$	56,548
Total assets	$	56,548	$	—	$	—	$	56,548

Liabilities:
Derivative liability	$	—	$	—	$	759	$	759
Total liabilities	$	—	$	—	$	759	$	759

Assets and liabilities measured at fair value on a recurring basis as of December 31, 2024 were as follows:


	Level 1		Level 2		Level 3		Total
	(in thousands)
Assets:
Money market funds	$	105,526	$	—	$	—	$	105,526
Total assets	$	105,526	$	—	$	—	$	105,526

Liabilities:
Derivative liability	$	—	$	—	$	2,829	$	2,829
Total liabilities	$	—	$	—	$	2,829	$	2,829

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

The following table reconciles the change in fair value of the derivative liability based on Level 3 inputs:




	Year Ended December 31,
	2025		2024
	(in thousands)
Balance at beginning of period	$	2,829	$	—

Fair value of derivative liability at issuance of term loan	—		4,450
Change in fair value	(2,070)		(1,621)
Balance at end of period	$	759	$	2,829

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

The fair value of the derivative liability in the term loan was estimated using the Monte Carlo model. A summary of the weighted-average significant unobservable inputs (Level 3 inputs) used in measuring the derivative liability in the term loan is as follows:


	December 31,
	2025	2024
Stock Price	$0.63	$1.48
Volatility	105.0%	103.0%
Risk-free rate (continuous)	3.5%	4.2%
Expected term (in years)	0.25	0.58
Dividend yield (continuous)	—%	—%

- Definition

Tabular disclosure of the fair value measurement of assets using significant unobservable inputs (Level 3), a reconciliation of the beginning and ending balances, separately presenting changes during the period attributable to the following: (1) total gains or losses for the period (realized and unrealized), segregating those gains or losses included in earnings (or changes in net assets) and gains or losses recognized in other comprehensive income (loss), and a description of where those gains or losses included in earnings (or changes in net assets) are reported in the statement of income (or activities); (2) purchases, sales, issues, and settlements (each type disclosed separately); and (3) transfers in and transfers out of Level 3 (for example, transfers due to changes in the observability of significant inputs), by class of asset.

+ References + Details

Basis of Presentation and Summary of Significant Accounting Policies - Cash, Cash Equivalents and Restricted Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Accounting Policies [Abstract]
Cash and cash equivalents	$ 57,050	$ 110,995
Restricted cash and cash equivalents	901	1,220
Cash, cash equivalents and restricted cash	$ 57,951	$ 112,215	$ 155,577

Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2025

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,
	2025		2024
	(in thousands)
Research and development	$	3,201	$	4,606
General and administrative	3,044		4,220
Total stock-based compensation	$	6,245	$	8,826

Weighted -average Valuation Assumptions

The fair value of stock options granted during the years ended December 31, 2025 and 2024 was calculated on the date of grant using the following weighted-average assumptions:


	Year Ended December 31,
	2025		2024
Risk-free interest rate	4.4	%	4.0	%
Expected term (in years)	5.9		6.0
Expected annual dividend yield	—	%	—	%
Expected volatility	95.4	%	92.7	%

Summary of Stock Option Activity

The following table summarizes stock option activity during the year ended December 31, 2025:


	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, 2024	7,634,937	$	6.24
Granted	3,390,691	$	1.49
Exercised	—	$	—
Cancelled	(1,070,756)	$	5.43
Outstanding, December 31, 2025	9,954,872	$	4.71	7.16	$	—
Exercisable at December 31, 2025	6,203,856	$	6.19	6.26	$	—

Nature of Business (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash and cash equivalents	$ 57,050	$ 110,995

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2025

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 our effective income tax rate after the adoption of ASU No. 2023-09 is as follows:


	Year Ended December 31, 2025
	Amount		Percent
U.S. federal statutory income tax rate	$	(12,773)	21.0	%


Nontaxable or nondeductible items
Stock-based compensation	442		(0.7)
Limitation of executive compensation	165		(0.3)
Other nontaxable or nondeductible items	(425)		0.7
R&D tax credits	(1,670)		2.8
Change in valuation allowance	14,345		(23.6)
Other adjustments	(84)		0.1
Effective income tax rate	$	—	0.0	%

A reconciliation of the expected income tax expense (benefit) computed using the federal statutory income tax rate to our effective income tax rate for the period prior to the adoption of ASU No. 2023-09 is as follows:


	Year Ended December 31,
	2024
Income tax computed at federal statutory rate	21.0	%
State taxes	6.5
Change in valuation allowance	(29.4)
R&D credit carryovers	3.7

Stock-based compensation	(2.4)
Permanent differences	0.5

Other	0.1
Effective income tax rate	0.0	%

Schedule of Deferred Tax Assets and Liabilities

Our deferred tax assets and liabilities consist of the following:


	As of December 31,
	2025		2024
	(in thousands)
Deferred tax assets:
Net operating losses	$	57,515	$	32,781
Tax credit carryforwards	8,155		6,141
Lease liability	2,631		3,069
Other capitalized costs—net of amortization	198		219
Reserves and accruals	31		983
Stock-based compensation	2,932		1,921
Capitalized research and experimental expenditures—net of amortization	17,187		25,214
Deferred tax assets	88,649		70,328
Valuation allowance	(86,588)		(67,756)
Deferred tax assets	2,061		2,572
Deferred tax liabilities:
Right of use asset	(1,455)		(1,676)
Fixed assets and depreciation	(606)		(896)


Deferred tax liabilities	(2,061)		(2,572)
Net deferred taxes	$	—	$	—

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2025

Commitments and Contingencies Disclosure [Abstract]

Summary of Operating Lease Costs

The following table summarizes operating lease costs:


	Year Ended December 31,
	2025		2024
	(in thousands)
Operating lease costs	$	1,565	$	1,918
Variable lease costs	1,073		1,280

Sublease income	—		(398)
Total	$	2,638	$	2,800

Cash paid for amounts included in the measurement of lease liabilities were $2.3 million and $2.5 million for the years ended December 31, 2025 and 2024, respectively.

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


	As of December 31,
	2025		2024
Weighted-average remaining lease term (years)	4.4		5.4
Weighted-average discount rate	8.0	%	8.0	%

Future Minimum Lease Payments

As of December 31, 2025, the future minimum lease payments due under our lease for each of the next five years ended December 31, and thereafter are as follows (in thousands):




2026	$	2,403
2027	2,471
2028	2,542
2029	2,614
2030	1,102

Total future minimum lease payments	11,132
Less: imputed interest	(1,697)
Total lease liability	$	9,435

Strategic Review and Liquidity	12 Months Ended
Strategic Review and Liquidity	Dec. 31, 2025
Restructuring and Related Activities [Abstract]
Strategic Review and Liquidity	2. Strategic Review and Liquidity In February 2026, we adopted a restructuring plan to extend our capital resources in connection with initiating a process to explore a full range of strategic alternatives to advance our promising platform and drug development pipeline to maximize stockholder value. We have engaged Piper Sandler & Co. (“Piper Sandler”) to serve as exclusive financial advisor to assist in the strategic review process. Measures contemplated during the strategic review process may include, among other options, a sale the Company, a business combination or merger, a sale of our assets, licensing or collaboration arrangements, or other strategic transactions. There can be no assurance that the strategic review process will result in any agreement or transaction that will enhance stockholder value, or any agreement or transaction at all. As part of the restructuring plan, our board of directors approved a reduction in force, representing 64% of our workforce, to better align our resources with our pursuit of strategic alternatives. As a result of the reduction in force, we estimate that we will incur a one-time charge in the first quarter of 2026 related to employee separation benefits, including severance and related benefits, of approximately $4.1 million, most of which is anticipated to result in cash expenditures to be incurred in the first quarter of 2026. We may also incur additional costs, including, but not limited to, potential impairment charges not currently contemplated due to events that may occur as a result of, or that are associated with, the restructuring plan. The estimated charges that we expect to incur are subject to a number of assumptions, and actual results may differ materially from these estimates. We had cash and cash equivalents of $57.1 million at December 31, 2025. The outcome of our strategic review process will inform future development plans and the costs associated with those efforts. The conditions described above raise substantial doubt about our ability to continue as a going concern for at least twelve months from the date these consolidated financial statements are issued in this Annual Report. There can be no assurance that the strategic review process will result in any agreement or transaction that will mitigate the conditions which raise substantial doubt about our ability to continue as a going concern, or at all. Our consolidated financial statements have been prepared on a going concern basis, which contemplates the realization of assets and settlement of liabilities and commitments in the ordinary course of business. Our consolidated financial statements do not include any adjustments that might result from the outcome of the conditions described above.

Accrued Expenses and Other Current Liabilities (Tables)

12 Months Ended

Dec. 31, 2025

Payables and Accruals [Abstract]

Accrued Expenses

Accrued expenses and other current liabilities were comprised as follows:


	December 31,
	2025		2024
	(in thousands)
Contract research	$	2,376	$	820
Professional fees	1,388		747
Manufacturing	928		4,783
Employee compensation and benefits	302		3,616
Accrued interest	266		266
Other	147		356
Total accrued expenses and other current liabilities	$	5,407	$	10,588

Strategic Review and Liquidity (Details) - USD ($) $ in Thousands	1 Months Ended
	Feb. 28, 2026	Mar. 31, 2026	Dec. 31, 2025	Dec. 31, 2024
Restructuring Cost and Reserve [Line Items]
Cash and cash equivalents			$ 57,050	$ 110,995
Subsequent Event
Restructuring Cost and Reserve [Line Items]
Reduction in workforce ((percent)	64.00%
Subsequent Event \| Forecast
Restructuring Cost and Reserve [Line Items]
Employee separation benefits		$ 4,100

- 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.

+ References + Details

Financial Instruments and Fair Value Measurements - Assets Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Assets:
Total assets	$ 56,548	$ 105,526
Liabilities:
Derivative liability	759	2,829
Total liabilities	759	2,829
Money market funds
Assets:
Money market funds	56,548	105,526
Level 1
Assets:
Total assets	56,548	105,526
Liabilities:
Derivative liability	0	0
Total liabilities	0	0
Level 1 \| Money market funds
Assets:
Money market funds	56,548	105,526
Level 2
Assets:
Total assets	0	0
Liabilities:
Derivative liability	0	0
Total liabilities	0	0
Level 2 \| Money market funds
Assets:
Money market funds	0	0
Level 3
Assets:
Total assets	0	0
Liabilities:
Derivative liability	759	2,829
Total liabilities	759	2,829
Level 3 \| Money market funds
Assets:
Money market funds	$ 0	$ 0

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

12 Months Ended

Dec. 31, 2025

Accounting Policies [Abstract]

Schedule of Cash and Cash Equivalents

The following table provides a reconciliation of cash, cash equivalents, and restricted cash and cash equivalents reported within the consolidated balance sheets that sum to the total of the same amounts shown in the consolidated statements of cash flows:


	December 31,
	2025		2024
	(in thousands)
Cash and cash equivalents	$	57,050	$	110,995

Restricted cash and cash equivalents	901		1,220
Total cash, cash equivalents and restricted cash and cash equivalents	$	57,951	$	112,215

Restrictions on Cash and Cash Equivalents


	December 31,
	2025		2024
	(in thousands)
Cash and cash equivalents	$	57,050	$	110,995

Restricted cash and cash equivalents	901		1,220
Total cash, cash equivalents and restricted cash and cash equivalents	$	57,951	$	112,215

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,
	2025		2024
	(in thousands)
Leasehold improvements	$	7,971	$	7,971
Laboratory equipment	2,485		2,485
Computer equipment	539		539
Furniture and fixtures	311		311

Total property and equipment, gross	11,306		11,306
Less: accumulated depreciation	(6,618)		(4,984)
Total property and equipment, net	$	4,688	$	6,322

Commitments and Contingencies - Summarizes Operating Lease Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Commitments and Contingencies Disclosure [Abstract]
Operating lease costs	$ 1,565	$ 1,918
Variable lease costs	1,073	1,280
Sublease income	0	(398)
Total	$ 2,638	$ 2,800

Income Taxes - Schedule of Effective Income Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Amount
U.S. federal statutory income tax rate	$ (12,773)
Nontaxable or nondeductible items
Stock-based compensation	442
Limitation of executive compensation	165
Other nontaxable or nondeductible items	(425)
R&D tax credits	1,670
Change in valuation allowance	14,345
Other adjustments	(84)
Income Tax Expense (Benefit)	$ 0
Percent
U.S. federal statutory income tax rate	21.00%	21.00%
Nontaxable or nondeductible items
State taxes		6.50%
Stock-based compensation	(0.70%)	(2.40%)
Limitation of executive compensation	(0.003)
Other nontaxable or nondeductible items	0.70%
R&D credit carryovers	2.80%	3.70%
Permanent differences		0.005
Change in valuation allowance	(23.60%)	(29.40%)
Other adjustments	0.10%	0.10%
Effective income tax rate	0.00%	0.00%

Segment Information

12 Months Ended

Dec. 31, 2025

Segment Reporting [Abstract]

Segment Information

16. Segment Information

We have one reportable segment which focuses on the discovery and development of cancer therapeutics. The segment derives its revenues from the Collaboration Agreement with Jazz (see Note 4, Collaboration and License Agreement).

Our CODM manages our operations on an integrated basis for the purpose of allocating resources. When evaluating our financial performance, our CODM regularly reviews total expenses and expenses by function and makes decisions using this information based on the performance of the enterprise as a whole. Our CODM primarily evaluates the performance of the enterprise based on results that have a direct impact on our available cash and cash equivalents and accordingly places less significance on non-cash expenses such as stock-based compensation and depreciation expenses in determining how to allocate resources.

Segment assets regularly reviewed by our CODM include measures of liquidity, primarily available cash and cash equivalents, and are consistent with the presentation of cash and cash equivalents reported in our consolidated balance sheets.

The following is a summary of our segment and consolidated net loss, including significant segment expenses:


	Year Ended December 31,
	2025		2024
	(in thousands)
Collaboration revenue	$	—	$	1,885
Less:
Clinical development	19,187		16,361
Research and discovery	12,660		14,389
General and administrative support	12,428		14,330
Manufacturing	8,523		19,759
Other segment expenses(a)	7,879		10,640



Interest income	3,108		6,673
Interest expense	(5,274)		(4,656)
Loss on extinguishment of debt	—		(553)
Other income, net	2,021		1,615
Segment and consolidated net loss	$	(60,822)	$	(70,515)

(a) Other segment expenses includes non-cash expenses for stock-based compensation and depreciation expenses.

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
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-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-21

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
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-Name Accounting Standards Codification
-Section 50
-Paragraph 21
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
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-Section 50
-Paragraph 32
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
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-Name Accounting Standards Codification
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
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-Section 50
-Paragraph 15
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-URI https://asc.fasb.org/1943274/2147482810/280-10-50-15

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
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Reference 7: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
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-Name Accounting Standards Codification
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-URI https://asc.fasb.org/1943274/2147482785/280-10-55-48

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
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+ Details

Segment Information (Tables)

12 Months Ended

Dec. 31, 2025

Segment Reporting [Abstract]

Schedule of Segment Reporting Information, by Segment

The following is a summary of our segment and consolidated net loss, including significant segment expenses:


	Year Ended December 31,
	2025		2024
	(in thousands)
Collaboration revenue	$	—	$	1,885
Less:
Clinical development	19,187		16,361
Research and discovery	12,660		14,389
General and administrative support	12,428		14,330
Manufacturing	8,523		19,759
Other segment expenses(a)	7,879		10,640



Interest income	3,108		6,673
Interest expense	(5,274)		(4,656)
Loss on extinguishment of debt	—		(553)
Other income, net	2,021		1,615
Segment and consolidated net loss	$	(60,822)	$	(70,515)

(a) Other segment expenses includes non-cash expenses for stock-based compensation and depreciation expenses.

Commitments and Contingencies - Future Minimum Lease Payment (Details) $ in Thousands	Dec. 31, 2025 USD ($)
Future Minimum Lease Payments
2026	$ 2,403
2027	2,471
2028	2,542
2029	2,614
2030	1,102
Total future minimum lease payments	11,132
Less: imputed interest	(1,697)
Total lease liability	$ 9,435

Property and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 11,306	$ 11,306
Less: accumulated depreciation	(6,618)	(4,984)
Total property and equipment, net	4,688	6,322
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	2,485	2,485
Computer equipment
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	539	539
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 311	$ 311

Common and Preferred Stock

12 Months Ended

Dec. 31, 2025

Equity [Abstract]

Common and Preferred Stock

9. Common and Preferred Stock

Common Stock

We are authorized to issue 200,000,000 shares of common stock. Common stockholders are entitled to dividends if and when declared by our board of directors. As of December 31, 2025, no dividends on common stock had been declared by us.

On May 10, 2022, we entered into a Sales Agreement (the “Sales Agreement”) with Leerink Partners, LLC (“Leerink Partners”), pursuant to which we are entitled to offer and sell shares of our 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. We were initially entitled to offer and sell shares of our common stock having an aggregate offering price of up to $50.0 million in the ATM Offering, which was subsequently increased in February 2024 to $75.0 million. On May 8, 2025, we filed a new Registration Statement on Form S-3 and filed a new prospectus covering the ATM Offering (the “Prospectus”) for the offer and sale of shares of our common stock with an aggregate offering price of up to $12.5 million in the ATM Offering as a result of being subject to General Instruction I.B.6 of Form S-3 (the “Baby Shelf Limitation”). As of December 31, 2025, we remain subject to the Baby Shelf Limitation. During the year ended December 31, 2025, we sold an aggregate of 3,626,701 shares under the ATM Offering at an average price of $1.77 per share for net proceeds of $5.9 million after deducting sales commissions and offering expenses. During the year ended December 31, 2024, we sold an aggregate of 5,272,538 shares under the ATM Offering at an average price of $4.71 per share for net proceeds of $23.5 million after deducting sales commissions and offering expenses.

We have reserved shares of common stock for issuance as follows:


	As of December 31,
	2025	2024
Shares reserved for exercises of outstanding stock options	9,954,872	7,634,937

Shares reserved for exercises of warrants	—	58,904
Shares reserved for issuance under the 2021 Employee Stock Purchase Plan	560,929	433,264
Shares reserved for future issuance under the 2021 Stock Incentive Plan	2,039,026	1,919,921
Shares reserved for future issuance as part of the K2HV Loan Agreement conversion feature	791,364	791,364
Total shares reserved for future issuance	13,346,191	10,838,390

Preferred Stock

We are authorized to issue 5,000,000 shares of undesignated preferred stock in one or more series. As of December 31, 2025, no shares of preferred stock were issued or outstanding.

- Definition

The entire disclosure for equity.

+ References

+ Details

Basis of Presentation and Summary of Significant Accounting Policies - Schedule of Property, Plant and Equipment (Details)	Dec. 31, 2025
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

Stock-based Compensation - Weighted Average Assumptions (Details) - Outstanding stock options	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Risk-free interest rate	4.40%	4.00%
Expected term (in years)	5 years 10 months 24 days	6 years
Expected annual dividend yield	0.00%	0.00%
Expected volatility	95.40%	92.70%

Term Loan - Schedule of Interest Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Debt Disclosure [Abstract]
Interest expense	$ 3,133	$ 2,094
Amortization of debt discount and accretion of Final Fee	2,141	1,217
total interest expense	$ 5,274	$ 3,311
Coupon rate (percent)	10.30%
Accretion of debt discount (percent)	8.94%
Effective interest rate (percent)	19.24%

Stock-based Compensation - Narrative (Details)		12 Months Ended
Stock-based Compensation - Narrative (Details)	Apr. 30, 2021 shares	Dec. 31, 2025 USD ($) $ / shares shares	Dec. 31, 2024 USD ($) $ / shares shares	Dec. 31, 2021
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Common stock available for issuance (in shares)		13,346,191	10,838,390
Exercised (in shares)		0
Share-based compensation expense not yet recognized \| $		$ 5,400,000
Inducement Stock Option
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Options granted (shares)		201,720	0
Unvested RSUs
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Aggregate fair value of awards that vested \| $			$ 1,000,000.0
Shares reserved for future issuance under the 2021 Stock Incentive Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Options granted (shares)		3,390,691
Expected annual dividend yield		0.00%	0.00%
Weighted-average grant date fair value of awards (in usd per share) \| $ / shares		$ 1.16	$ 3.43
Exercised (in shares)		0
Aggregate intrinsic fair value of options exercised \| $			$ 0
Share-based compensation not yet recognized, recognition period		1 year 10 months 24 days
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)		2,039,026
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 Incentive Plan \| Unvested RSUs
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Granted (in shares)		0
Share-based compensation expense not yet recognized \| $		$ 0
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
Exercised (in shares)			(17,224)
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)		7,152,859
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)		96,470	73,849
Shares purchased by employees, value \| $		$ 100,000	$ 100,000

Term Loan - Narrative (Details) $ in Thousands		1 Months Ended		12 Months Ended
Term Loan - Narrative (Details) $ in Thousands	May 02, 2024	May 31, 2024 USD ($)	Apr. 30, 2022 USD ($)	Dec. 31, 2025 USD ($)	Dec. 31, 2024 USD ($)
Debt Instrument [Line Items]
Floating rate spread in effect (greater than) (percent)			0.50%
Debt instrument, interest rate, stated percentage			4.50%
Interest expense				$ 5,274	$ 3,311
Proceeds from drawdown of term loans				0	30,000
Loss on extinguishment of debt				0	553
Payment of debt issuance costs				0	673
Level 3
Debt Instrument [Line Items]
Fair value of derivative liability at issuance of term loan		$ 4,500		0	4,450
Term loan
Debt Instrument [Line Items]
Interest expense					1,300
Proceeds from drawdown of term loans		29,500
Cash used to repay debt		10,500
Loss on extinguishment of debt					$ 600
Term Loans
Debt Instrument [Line Items]
Payment of debt issuance costs		700
Facility fee		400
Payments for other fees and expenses		200
Debt instrument, final fee amount		100
Debt discount		$ 5,100
Long-term debt, fair value				$ 29,500
Term Loans \| Term loan
Debt Instrument [Line Items]
Term loan available			$ 40,000
Loan Agreement
Debt Instrument [Line Items]
Floating rate spread in effect (greater than) (percent)		1.80%
Proceeds from drawdown of term loans		$ 30,000
Loan agreement, amount		60,000
Amount of net cash proceeds from certain financing activities		60,000
Minimum amount of offering of common stock		$ 50,000
Debt instrument variable rate floor (percent)		10.30%
Final fee, percentage		6.95%
Conversion of outstanding principal		$ 5,000
Additional interest rate (percent)	0.050
Allowable amount to invest in future offerings		$ 5,000
Loan Agreement \| Minimum
Debt Instrument [Line Items]
Adjustment rate (percent)		9.99%
Loan Agreement \| Maximum
Debt Instrument [Line Items]
Adjustment rate (percent)		19.99%
Loan Agreement \| Period One
Debt Instrument [Line Items]
Proceeds from drawdown of term loans		$ 25,000
Period for interest only payments (in months)		24 months
Loan Agreement \| Period Two
Debt Instrument [Line Items]
Proceeds from drawdown of term loans		$ 5,000
Loan Agreement \| Tranche three
Debt Instrument [Line Items]
Capacity available to draw on the term loans		10,000
Loan Agreement \| Tranche four
Debt Instrument [Line Items]
Capacity available to draw on the term loans		$ 20,000

Term Loan

12 Months Ended

Dec. 31, 2025

Debt Disclosure [Abstract]

Term Loan

8. Term Loan

PWB Loan Agreement

In April 2022, we entered into the PWB Loan Agreement with PWB and subsequently drew down an aggregate of $40.0 million in term loans. The term loans accrued 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 changed throughout the term, the interest rate would have been adjusted effective on the date of the prime rate change. All interest chargeable under the PWB Loan Agreement was computed on a 360-day year for the actual number of days elapsed, with interest payable monthly. We recognized interest expense related to the PWB Loan Agreement of $1.3 million during the year ended December 31, 2024.

In May 2024, we repaid all amounts outstanding under the PWB Loan Agreement, using $29.5 million in net loan proceeds received under the K2HV Loan Agreement, as described below, together with $10.5 million in existing cash. We recognized a total loss on extinguishment of debt in the amount of $0.6 million during the year ended December 31, 2024 primarily due to the write off of unamortized debt issuance costs.

K2HV Loan Agreement

In May 2024, we, as borrower, entered into the K2HV Loan Agreement with K2HV (together with any other lender from time to time, the “Lenders”); K2HV, as administrative agent for the Lenders; and Ankura Trust Company, LLC, as collateral trustee for the Lenders. The K2HV Loan Agreement provides up to $60.0 million principal in term loans. We received $30.0 million in gross loan proceeds at closing; $25.0 million from the first tranche commitment and $5.0 million from the second tranche commitment. A third tranche commitment of up to $10.0 million was available to be drawn at our option through June 30, 2025, subject to the achievement, as determined by the administrative agent in its discretion, of certain time-based, clinical and regulatory milestones and receipt of not less than $60.0 million in net cash proceeds from certain financing activities, with at least $50.0 million from a single offering of common stock. Our ability to draw upon the third tranche commitment expired on June 30, 2025 without being drawn upon. A fourth tranche commitment of up to $20.0 million is available to be drawn down at our option through May 1, 2026, subject to Lender’s review of our clinical, financial and operating plan and subject to the Lender’s consent in its sole and absolute discretion.

The term loan matures on May 1, 2028, and we are obligated to make interest only payments for the first 24 months, followed by interest and equal principal payments each month thereafter through the maturity date. The term loan bears a variable interest rate equal to the greater of (i) 10.3%, and (ii) the sum of (A) the prime rate last quoted in The Wall Street Journal (or a comparable replacement rate if The Wall Street Journal ceases to quote such rate) and (B) 1.8%. We may prepay, at our option, all, but not less than all, of the outstanding principal balance and all accrued and unpaid interest with respect to the principal balance being prepaid of the term loans, subject to a prepayment premium to which the Lenders are entitled and certain notice requirements. We are obligated to pay a final fee equal to 6.95% of the aggregate amount of the term loans funded, or the Final Fee, to occur upon the earliest of (i) the maturity date, (ii) the acceleration of the term loans, and (iii) the prepayment of the term loans. The Final Fee is being accreted to interest expense using the effective interest method over the life of the debt.

The Lenders may elect prior to the full repayment of the term loans to convert up to $5.0 million of outstanding principal of the term loans into shares of our common stock, pursuant to the Fixed Price Conversion or the Variable Price Conversion, subject to customary adjustments and 9.99% and 19.99% beneficial ownership limitations. There will be no prepayment penalty for any principal amount converted into common stock. We determined that the Fixed Price Conversion and the Variable Price Conversion within the K2HV Loan Agreement are required to be bifurcated as an embedded derivative under ASC 815, Derivatives and Hedging (“ASC 815”), at fair value, and recorded as a discount on the debt on the date of issuance, with subsequent changes in fair value recognized in the accompanying consolidated statements of operations. See Note 5 for further discussion on this derivative instrument.

As security for our obligations under the K2HV Loan Agreement, we granted the Lenders a first priority security interest on substantially all of our assets (other than intellectual property), subject to certain exceptions. The K2HV Loan Agreement contains customary representations and warranties, events of default and affirmative and negative covenants, including covenants that limit or restrict our ability to, among other things, dispose of assets, make changes to our business, management, ownership or business locations, merge or consolidate, incur additional indebtedness, incur additional liens, pay dividends or other distributions or repurchase equity, make investments, and enter into certain transactions with affiliates, in each case subject to certain exceptions. Upon the occurrence of an event of default, a default interest rate of an additional 5.0% per annum may be applied to the outstanding loan balances, and the Lenders may declare all outstanding obligations immediately due and payable and exercise all of their rights and remedies as set forth in the K2HV Loan Agreement and under applicable law. As of December 31, 2025, we are in compliance with all covenants.

Subject to certain conditions, we granted the Lenders the right, prior to repayment of the term loans, to invest up to $5.0 million in the aggregate in future offerings of capital stock, at market terms, subject to certain exceptions and conditions.

We incurred debt issuance costs of $0.7 million in connection with the term loans, composed of the facility fee of $0.4 million and other expenses paid to the Lenders of $0.2 million and external legal fees of $0.1 million. These debt issuance costs, together with the fair value of the embedded derivative of $4.5 million at inception of the K2HV Loan Agreement, resulted in a debt discount of $5.1 million which is being amortized to interest expense over the term of the K2HV Loan Agreement using the effective interest method. As of December 31, 2025, the fair value of the term loan was estimated to be approximately $29.5 million. The fair value was measured using a discounted cash flow analysis, specifically the yield method, which requires the use of Level 3 inputs in the fair value hierarchy.

The outstanding term loans payable consists of the following:


	December 31,
	2025		2024
	(in thousands)
Note payable	$	30,000	$	30,000
Unamortized debt discount and issuance costs	(1,764)		(3,905)
Net carrying amount of note payable	28,236		26,095
Less: current portion of note payable	(28,236)		—
Note payable, net, less current portion	$	—	$	26,095

The following table provides the components of interest expense related to the K2HV Loan Agreement:


	Year Ended December 31,
	2025		2024
	(in thousands)
Interest expense based on coupon interest rate (10.3%) of outstanding term loans	$	3,133	$	2,094
Amortization of debt discount and accretion of Final Fee (8.94%)	2,141		1,217
Total interest expense on effective rate (19.24%)	$	5,274	$	3,311

The following table presents the total principal payments and Final Fee contractually scheduled to become due during each of the years ended December 31 (in thousands):





2026	$	9,600
2027	14,400
2028	8,085
Total principal payments and Final Fee	$	32,085

We have presented the full amount of the term loan payable, net of discount and issuance costs, as a current liability as of December 31, 2025, given the potential that the loan may be repaid in the subsequent twelve months.

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 8A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-8A

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480738/235-10-S50-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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-Paragraph 1
-Subparagraph (SX 210.4-08(c))
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-Publisher FASB
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-Section 50
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+ Details

Cover - USD ($)	12 Months Ended
Cover - USD ($)	Dec. 31, 2025	Mar. 20, 2026	Jun. 30, 2025
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2025
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			$ 39,559,339
Entity Common Stock, Shares Outstanding		48,596,817
Documents Incorporated by Reference	None
Entity Central Index Key	0001785530
Document Fiscal Year Focus	2025
Document Fiscal Period Focus	FY
Amendment Flag	false

Financial Instruments and Fair Value Measurements - Unobservable Inputs (Details)	Dec. 31, 2025 $ / shares year	Dec. 31, 2024 $ / shares year
Stock Price (in dollars per share)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Measurement input \| $ / shares	0.63	1.48
Volatility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Measurement input	1.050	1.030
Risk-free rate (continuous)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Measurement input	0.035	0.042
Expected term (in years)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Measurement input \| year	0.25	0.58
Dividend yield (continuous)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Measurement input	0	0

Commitment and Contingencies

12 Months Ended

Dec. 31, 2025

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

11. Commitments and Contingencies

Leases

Our 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 terminated in March 2024. The lease was subject to fixed-rate rent escalations and provided for a term extension option, which was not reasonably certain of exercise. In May 2022, we entered into a sublease agreement with Crossbow Therapeutics, Inc. (“Crossbow”), to sublease the entirety of this space. The total rent due to us for the subleased premises over the term of the sublease was approximately $2.1 million, which is greater than the annual rent paid by us to the landlord for the leased premises over the same term. Rent expense associated with the April 2019 operating lease was recognized net of the lease income generated from the sublease agreement. Lease income was allocated to either research and development expense or general and administrative expense in the same manner as the associated rent expense was allocated. Crossbow was obligated to pay all real estate taxes and costs related to the subleased premises, including cost of operations, maintenance, repair, replacement, and property management. The sublease with Crossbow terminated in March 2024 concurrently with the termination of the lease.

•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 we fully utilized, and a term extension option, which was not reasonably certain of exercise. We provided the landlord with a security deposit in the form of a letter of credit in the amount of $1.0 million upon signing. In May 2025, the letter of credit was reduced to $0.7 million in accordance with the terms of the lease. The balance of the letter of credit is included in restricted cash and cash equivalents as of December 31, 2025 and 2024.

The following table summarizes operating lease costs:


	Year Ended December 31,
	2025		2024
	(in thousands)
Operating lease costs	$	1,565	$	1,918
Variable lease costs	1,073		1,280

Sublease income	—		(398)
Total	$	2,638	$	2,800

Cash paid for amounts included in the measurement of lease liabilities were $2.3 million and $2.5 million for the years ended December 31, 2025 and 2024, respectively.

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


	As of December 31,
	2025		2024
Weighted-average remaining lease term (years)	4.4		5.4
Weighted-average discount rate	8.0	%	8.0	%

As of December 31, 2025, the future minimum lease payments due under our lease for each of the next five years ended December 31, and thereafter are as follows (in thousands):




2026	$	2,403
2027	2,471
2028	2,542
2029	2,614
2030	1,102

Total future minimum lease payments	11,132
Less: imputed interest	(1,697)
Total lease liability	$	9,435

License Agreements

Harpoon License

In March 2018, we entered into an 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 us 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 us (the “Harpoon License”).

On October 19, 2018, we entered into the First Amended and Restated Assignment and License Agreement with Harpoon, which amended certain terms of the original agreement, but did not change the terms of the license to us, 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 us or by us to Harpoon. In exchange for these additional terms, Harpoon agreed to reimburse up to $75,000 of our legal costs. Additionally, we agreed to pay to Harpoon royalties on future net sales and pay minimum annual royalties of $250,000 upon achievement of our first commercial sale.

Under the terms of the Harpoon License, we paid an upfront fee of $500,000 in 2018 and are obligated to reimburse Harpoon for certain legal costs incurred by Harpoon. In addition, we are obligated to pay Harpoon royalties based on future net sales and have agreed to pay a minimum annual royalty payment at an amount in the low hundreds of thousands of dollars upon achievement of our first commercial sale. In 2018, we 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, we 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. We have 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, we 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 us the rights to initiate certain research initiatives on a specified number of targets. Adimab also granted us a license to certain Adimab core technologies, antibodies and products applicable to certain targets (“Adimab License”).

In August 2020, we entered into Amendment One to the Development and Option Agreement with Adimab, which extended the period of time for us 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 us 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, we entered into the First Amended and Restated Development and Option Agreement with Adimab to extend the target selection time period and to allow for us 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, we must pay both an upfront fee and final fee of $200,000 for all research programs. We 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, we must pay a $500,000 fee for each target option exercised.

For each target option exercised, we are 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, we 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, 2025, we have exercised the target option for one target covered under the Adimab Agreement. As

of December 31, 2025, we have not made any payments for clinical or sales-based milestones or royalties pursuant to the Adimab Agreement.

Adimab 2022 Collaboration

In November 2022, we entered into a Collaboration Agreement (the “Adimab Collaboration Agreement”) with Adimab. Under the terms of the Adimab Collaboration Agreement, Adimab has agreed to provide us with services to help discover, generate, optimize and/or engineer specified proteins. In addition, Adimab will provide us 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, we 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 us. The Adimab Collaboration Agreement provides us with an option to obtain any development and commercialization licenses from Adimab used in products. To exercise an option, we must pay a $500,000 fee for each product option exercised.

For each product sold, we are 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, we 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, 2025, we have not exercised any options and have not made any payments for clinical or sales-based milestones or royalties pursuant to the Adimab Collaboration Agreement.

Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Payables and Accruals [Abstract]
Contract research	$ 2,376	$ 820
Professional fees	1,388	747
Manufacturing	928	4,783
Employee compensation and benefits	302	3,616
Accrued interest	266	266
Other	147	356
Total accrued expenses and other current liabilities	$ 5,407	$ 10,588

Net Loss Attributable to Common Stockholders per Share

12 Months Ended

Dec. 31, 2025

Earnings Per Share [Abstract]

Net Loss Attributable to Common Stockholders per Share

15. 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, the conversion option derivative under the K2HV Loan Agreement, common stock to be issued under the 2021 ESPP, 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,
	2025	2024
Outstanding stock options	9,954,872	7,634,937

Warrants to purchase common stock	—	58,904
Common stock to be issued under the 2021 ESPP	85,368	67,445

Total	10,040,240	7,761,286

Basic net loss per share is computed by dividing net loss by the weighted-average number of shares of common stock outstanding during the applicable period. In computing diluted net loss per share, only potential shares of common stock that are dilutive are included. We considered each issue or series of issues of potential shares of common stock separately when determining whether potential shares of common stock are dilutive or anti-dilutive. We made such determination in sequence from the most dilutive to the least dilutive and concluded that the conversion option derivative under the K2HV Loan Agreement is dilutive to net loss per share for the years ended December 31, 2025 and 2024. Pursuant to FASB ASC Topic 260, Earnings Per Share, we applied the if-converted method to determine the effect of the conversion option derivative under the K2HV Loan Agreement on the diluted earnings per share calculations. Pursuant to such method, we adjusted the numerator for the gain recognized during each period in net loss due to the change in the fair value of the conversion option derivative liability under the K2HV Loan Agreement and the interest expense recognized during each period that is attributable to the portion of the term loan that is subject to the conversion option. We also increased the denominator to include the weighted-average number of additional shares of common stock that would have been outstanding if the conversion option derivative under the K2HV Loan Agreement were converted at the beginning of the period or at the inception of the K2HV Loan Agreement for the years ended December 31, 2025 and 2024, respectively. The following table summarizes the computations of basic and diluted net loss per share as presented in our consolidated statements of operations:


	Year Ended December 31,
	2025		2024
	(in thousands, except share and per share amounts)
Numerator
Net loss	$	(60,822)	$	(70,515)
Less: change in fair value of derivative liability	(2,070)		(1,621)
Plus: interest expense on converted term loan	776		493
Adjusted net loss	$	(62,116)	$	(71,643)
Denominator
Weighted-average common stock outstanding, basic	46,018,888		43,332,088
Dilutive effect of common stock issuable from assumed conversion of convertible term loan	791,364		527,576
Weighted-average common stock outstanding, diluted	46,810,252		43,859,664
Net loss per share
Basic	$	(1.32)	$	(1.63)
Diluted	$	(1.33)	$	(1.63)

Basis of Presentation and Summary of Significant Accounting Policies - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2025 USD ($) segment institution	Dec. 31, 2024 USD ($)
Property, Plant and Equipment [Line Items]
Number of operating segments \| segment	1
Restricted cash and cash equivalents \| $	$ 0.9	$ 1.2
Number of financial institutions \| institution	1

Collaboration and License Agreement - Narrative (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Apr. 30, 2022	Dec. 31, 2025	Dec. 31, 2024
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue		$ 0	$ 1,885
Revenue recognized that was included in prior period deferred revenue			1,300
Collaborative Arrangement
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Development and regulatory milestones (up to)		515,000
Sales-based milestones (up to)		740,000
Transaction price	$ 32,300
Non-refundable upfront cash payment received	15,000
Estimated future reimbursable costs	$ 17,300
Revenue		$ 0	$ 0

Income Taxes

12 Months Ended

Dec. 31, 2025

Income Tax Disclosure [Abstract]

Income Taxes

12. Income Taxes

During the years ended December 31, 2025 and 2024, we recorded no current or deferred income tax expenses or benefits as we have incurred losses since inception and have provided a full valuation allowance against our deferred tax assets.


	Year Ended December 31, 2025
	Amount		Percent
U.S. federal statutory income tax rate	$	(12,773)	21.0	%


Nontaxable or nondeductible items
Stock-based compensation	442		(0.7)
Limitation of executive compensation	165		(0.3)
Other nontaxable or nondeductible items	(425)		0.7
R&D tax credits	(1,670)		2.8
Change in valuation allowance	14,345		(23.6)
Other adjustments	(84)		0.1
Effective income tax rate	$	—	0.0	%


	Year Ended December 31,
	2024
Income tax computed at federal statutory rate	21.0	%
State taxes	6.5
Change in valuation allowance	(29.4)
R&D credit carryovers	3.7

Stock-based compensation	(2.4)
Permanent differences	0.5

Other	0.1
Effective income tax rate	0.0	%

Our deferred tax assets and liabilities consist of the following:


	As of December 31,
	2025		2024
	(in thousands)
Deferred tax assets:
Net operating losses	$	57,515	$	32,781
Tax credit carryforwards	8,155		6,141
Lease liability	2,631		3,069
Other capitalized costs—net of amortization	198		219
Reserves and accruals	31		983
Stock-based compensation	2,932		1,921
Capitalized research and experimental expenditures—net of amortization	17,187		25,214
Deferred tax assets	88,649		70,328
Valuation allowance	(86,588)		(67,756)
Deferred tax assets	2,061		2,572
Deferred tax liabilities:
Right of use asset	(1,455)		(1,676)
Fixed assets and depreciation	(606)		(896)


Deferred tax liabilities	(2,061)		(2,572)
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. For tax years prior to the year ended December 31, 2025, we amortized 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. On July 4, 2025, the One Big Beautiful Bill Act (“OBBBA”) was signed into law. The legislation includes significant corporate tax reforms, including the permanent reinstatement of the ability to deduct domestic R&D expenditures as incurred beginning in tax year 2025, replacing the previous requirement to amortize these such expenditures over 5 years. The requirement to amortize R&D expenditure incurred outside the U.S. over a period of 15 years was unchanged by the OBBBA. With respect to domestic R&D expenditures capitalized prior to the enactment of the OBBBA, we have elected to amortize these costs for tax purposes at a rate of 50% of the total capitalized costs during the year ended December 31, 2025, and the remaining 50% is expected to be amortized during tax year 2026.

Following the enactment of the OBBBA, we capitalized R&E expenditures totaling $6.8 million during the year ended December 31, 2025. Prior to the enactment of the OBBBA, we capitalized R&E expenditures totaling $50.2 million during the year ended December 31, 2024.

We evaluated the positive and negative evidence bearing upon our ability to realize the deferred tax assets as of December 31, 2025 and 2024. We considered our cumulative net losses and concluded as of December 31, 2025 and 2024, that it was more likely than not that we 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, 2025 and 2024. The valuation allowance increased by $18.8 million during the year ended December 31, 2025 as the result of operating losses generated with no corresponding financial statement benefit and partially offset by a decrease in deferred assets related to capitalized R&E expenditures as a result of the enactment of the OBBBA described above. The valuation allowance increased by $20.7 million during the year ended December 31, 2024 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.

We have incurred net operating losses since inception. As of December 31, 2025 and 2024, we had federal net operating loss carryforwards of $215.3 million and $126.8 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, 2025, federal net operating loss carryforwards includes $215.2 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, 2025 and 2024, we had state net operating loss carryforwards of $153.7 million and $76.8 million, respectively, available to reduce future state taxable income, which expire at various dates beginning in 2037.

As of December 31, 2025 and 2024, we had federal research and development tax credit carryforwards of $6.5 million and $4.9 million, respectively, available to reduce future federal tax liabilities, which expire at various dates beginning in 2042. We had state research and development tax credit carryforwards as of December 31, 2025 and 2024 of $1.6 million and $1.3 million, respectively, available to reduce future state tax liabilities, which expire at various dates beginning in 2034.

Utilization of our 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.

We 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 we 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 our federal net operating losses will expire unused. A portion of our state net operating losses, and federal and state research and development tax credits are expected to expire unused. We have analyzed the impact of these limitations on our attributes and included the impact of these limitations in our deferred tax assets as of December 31, 2025 and 2024.

We have not recorded any reserves for uncertain tax positions as of December 31, 2025 and 2024. We have conducted a study of research and development tax credits 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 our research and development credits.

We file tax returns as prescribed by the tax laws of the jurisdictions in which we operate. In the normal course of business, we are 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 2022, although carryforward attributes that were generated prior to 2022 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 tax.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-Section 50
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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

Property and Equipment, Net (Tables)

12 Months Ended

Dec. 31, 2025

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,
	2025		2024
	(in thousands)
Leasehold improvements	$	7,971	$	7,971
Laboratory equipment	2,485		2,485
Computer equipment	539		539
Furniture and fixtures	311		311

Total property and equipment, gross	11,306		11,306
Less: accumulated depreciation	(6,618)		(4,984)
Total property and equipment, net	$	4,688	$	6,322

Collaboration and License Agreement	12 Months Ended
Collaboration and License Agreement	Dec. 31, 2025
Business Combination, Asset Acquisition, Transaction between Entities under Common Control, and Joint Venture Formation [Abstract]
Collaboration and License Agreement	4. Collaboration and License Agreement In April 2022, we entered into an exclusive global collaboration and license agreement (the “Collaboration Agreement”) with Jazz Pharmaceuticals Ireland Limited (“Jazz”) pursuant to which we granted Jazz certain licenses to develop and commercialize products containing our 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, we were responsible for certain preclinical development activities with respect to JZP898 and other development activities specified in mutually agreed upon development plans. Jazz had generally reimbursed us for the cost of such activities. Jazz is 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 and initiated a Phase 1 clinical trial of JZP898 in the fourth quarter of 2023. In June 2024, we executed a transfer agreement (the “Transfer Agreement”) to assign our rights in a development agreement with a contract manufacturer of JZP898 to Jazz. The execution of this Transfer Agreement was the last material performance obligation required of us under the Collaboration Agreement. Milestones and Royalties As of December 31, 2025, we are 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, we are 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, 2025, we have not recognized any revenue related to sales-based milestones. Accounting Analysis under ASC 606 Identification of the Contract(s) We 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 We have concluded that the exclusive license to our 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, we have 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 a nonrefundable upfront payment of $15.0 million and 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. We 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 of our control. Accordingly, all such milestone payments were excluded from the transaction price at inception. We re-evaluate the transaction price at the end of each reporting period and as uncertain events are resolved or other changes in circumstances occur, and adjust the transaction price as necessary. During the years ended December 31, 2025 and 2024, we did not recognize any adjustment to the transaction price associated with variable consideration previously excluded from the transaction price. 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. We 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). Recognition of Revenue We use 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 judgments 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 year ended December 31, 2024, we recognized $1.9 million of revenue related to the Collaboration Agreement. Revenue recognized during the year ended December 31, 2024 includes $1.3 million of revenue that was included in deferred revenue as of December 31, 2023. Revenue from the reimbursement of costs for research activities was recognized during the year ended December 31, 2024 in an amount equal to the costs incurred. As of December 31, 2025, we have not received any royalty payments under the Collaboration Agreement.

Income Taxes - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
Income Taxes - Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Operating Loss Carryforwards [Line Items]
Current income tax expenses	$ 0	$ 0
Deferred income tax expenses (benefits)	0	0
Capitalized research and experimentation expenses	6,800	50,200
Valuation allowance, deferred tax asset, increase	18,800	20,700
Deferred tax assets, operating loss carryforwards not subject to expiration	215,200
UNITED STATES
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	215,300	126,800
UNITED STATES \| Research Tax Credit Carryforward
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	6,500	4,900
State and Local Tax Jurisdiction, Other
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	153,700	76,800
Tax credit carryforwards	$ 1,600	$ 1,300

Term Loan - Schedule of Outstanding Term Loans Payable (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Debt Instrument [Line Items]
Net carrying amount of note payable	$ 32,085
Term Loans \| Term loan
Debt Instrument [Line Items]
Note payable	30,000	$ 30,000
Unamortized debt discount and issuance costs	(1,764)	(3,905)
Net carrying amount of note payable	28,236	26,095
Less: current portion of note payable	(28,236)	0
Net carrying amount of note payable	$ 0	$ 26,095

- 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 of unamortized debt discount (premium) and debt issuance costs.

+ References + Details

- Definition

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

+ References

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+ Details

Income Taxes -Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Deferred tax assets:
Net operating losses	$ 57,515	$ 32,781
Tax credit carryforwards	8,155	6,141
Lease liability	2,631	3,069
Other capitalized costs—net of amortization	198	219
Reserves and accruals	31	983
Stock-based compensation	2,932	1,921
Capitalized research and experimental expenditures—net of amortization	17,187	25,214
Deferred tax assets	88,649	70,328
Valuation allowance	(86,588)	(67,756)
Deferred tax assets	2,061	2,572
Deferred tax liabilities:
Right of use asset	(1,455)	(1,676)
Fixed assets and depreciation	(606)	(896)
Deferred tax liabilities	(2,061)	(2,572)
Net deferred taxes	$ 0	$ 0

Term Loan - Schedule of Total Principle Payments Maturities (Details) $ in Thousands	Dec. 31, 2025 USD ($)
Long-Term Debt, Fiscal Year Maturity [Abstract]
2026	$ 9,600
2027	14,400
2028	8,085
Net carrying amount of note payable	$ 32,085

- Definition

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

+ References

+ Details

Common and Preferred Stock - Narrative (Details)	12 Months Ended
Common and Preferred Stock - Narrative (Details)	Dec. 31, 2025 USD ($) $ / shares shares	Dec. 31, 2024 USD ($) $ / shares shares	May 08, 2025 USD ($)	Feb. 29, 2024 USD ($)	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 \| $	$ 5,939,000	$ 23,576,000
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	3,626,701	5,272,538
Price per share (in usd per share) \| $ / shares	$ 1.77	$ 4.71
Proceeds from at the market offering of common stock, net of issuance costs \| $	$ 5,900,000	$ 23,500,000
Maximum \| ATM Offering
Class of Stock [Line Items]
Common stock, amount authorized \| $				$ 75,000,000.0	$ 50,000,000.0
Maximum \| ATM Offering - Baby Shelf Limitation
Class of Stock [Line Items]
Common stock, amount authorized \| $			$ 12,500,000

Audit Information	12 Months Ended
Audit Information	Dec. 31, 2025
Audit Information [Abstract]
Auditor Firm ID	42
Auditor Name	Ernst & Young LLP
Auditor Location	Boston, Massachusetts

Stock-based Compensation - Expense Recognized (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	$ 6,245	$ 8,826
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	3,201	4,606
General and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	$ 3,044	$ 4,220

Defined Contribution Benefit Plan (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
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	$ 0.3	$ 0.3

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2025	Dec. 31, 2024
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)	48,596,817	44,827,159
Common stock outstanding (in shares)	48,596,817	44,827,159

Accrued Expenses and Other Current Liabilities

12 Months Ended

Dec. 31, 2025

Payables and Accruals [Abstract]

Accrued Expenses and Other Current Liabilities

7. Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities were comprised as follows:


	December 31,
	2025		2024
	(in thousands)
Contract research	$	2,376	$	820
Professional fees	1,388		747
Manufacturing	928		4,783
Employee compensation and benefits	302		3,616
Accrued interest	266		266
Other	147		356
Total accrued expenses and other current liabilities	$	5,407	$	10,588

Financial Instruments and Fair Value Measurements

12 Months Ended

Dec. 31, 2025

Fair Value Disclosures [Abstract]

Financial Instruments and Fair Value Measurements

5. Financial Instruments and Fair Value Measurements

Our 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 our consolidated balance sheets as of December 31, 2025 and 2024.

Our liabilities that are required to be measured at fair value on a recurring basis consist of a derivative liability pursuant to a loan and security agreement (the “K2HV Loan Agreement”) with K2 HealthVentures LLC (“K2HV”) (see Note 8, Term Loan) on our consolidated balance sheet as of December 31, 2025 and 2024.

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 and liabilities measured at fair value on a recurring basis as of December 31, 2025 were as follows:


	Level 1		Level 2		Level 3		Total
	(in thousands)
Assets:
Money market funds	$	56,548	$	—	$	—	$	56,548
Total assets	$	56,548	$	—	$	—	$	56,548

Liabilities:
Derivative liability	$	—	$	—	$	759	$	759
Total liabilities	$	—	$	—	$	759	$	759

Assets and liabilities measured at fair value on a recurring basis as of December 31, 2024 were as follows:


	Level 1		Level 2		Level 3		Total
	(in thousands)
Assets:
Money market funds	$	105,526	$	—	$	—	$	105,526
Total assets	$	105,526	$	—	$	—	$	105,526

Liabilities:
Derivative liability	$	—	$	—	$	2,829	$	2,829
Total liabilities	$	—	$	—	$	2,829	$	2,829

There were no changes in valuation techniques during the year ended December 31, 2025.

Derivative Liability

In May 2024, we entered into the K2HV Loan Agreement, as further described in Note 8, which provides up to $60.0 million principal in term loans. Pursuant to the terms of the K2HV Loan Agreement, the lenders thereto may elect, prior to the full repayment of the term loans, to convert up to $5.0 million of the outstanding principal of the term loans into shares of our common stock at a conversion price of the lesser of $6.3182 per share (the “Fixed Price Conversion”) and the lowest effective price per share of our first equity financing following the closing of the K2HV Loan Agreement (the “Variable Price Conversion”), subject to customary adjustments and 9.99% and 19.99% beneficial ownership limitations. The Fixed Price Conversion and Variable Price Conversion within the K2HV Loan Agreement are required to be bifurcated as a single compound embedded derivative carried at fair value, with subsequent changes in fair value recognized in the consolidated statements of operations.

The following table reconciles the change in fair value of the derivative liability based on Level 3 inputs:




	Year Ended December 31,
	2025		2024
	(in thousands)
Balance at beginning of period	$	2,829	$	—

Fair value of derivative liability at issuance of term loan	—		4,450
Change in fair value	(2,070)		(1,621)
Balance at end of period	$	759	$	2,829

The change in fair value of the derivative liability is included in other income, net in the accompanying consolidated statements of operations. We recognized gains of $2.1 million and $1.6 million related to change in fair value of the derivative liability during the years ended December 31, 2025 and 2024, respectively.


	December 31,
	2025	2024
Stock Price	$0.63	$1.48
Volatility	105.0%	103.0%
Risk-free rate (continuous)	3.5%	4.2%
Expected term (in years)	0.25	0.58
Dividend yield (continuous)	—%	—%

- 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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 107
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482078/820-10-55-107

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 100
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482078/820-10-55-100

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6A
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-6A

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2E
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2E

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6A
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-6A

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6A
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-6A

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6A
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-6A

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6A
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-6A

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 940
-SubTopic 820
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478119/940-820-50-1

+ Details

Defined Contribution Benefit Plan	12 Months Ended
Defined Contribution Benefit Plan	Dec. 31, 2025
Retirement Benefits [Abstract]
Defined Contribution Benefit Plan	14. Defined Contribution Benefit Plan We sponsor 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. We match 50% of each participant’s contribution up to a maximum of 6% of such participant’s eligible compensation paid in a calendar year. We recognized expenses of $0.3 million related to matching contributions during each of the years ended December 31, 2025 and 2024.

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 ($)	Dec. 31, 2025 USD ($)	Dec. 31, 2024 USD ($)	Dec. 31, 2018 USD ($)	May 31, 2025 USD ($)	Nov. 30, 2022 USD ($)	Jun. 30, 2021 USD ($) ft²	Apr. 30, 2019 ft²
Loss Contingencies [Line Items]
Sublease income				$ 0	$ 398
Cash paid for amounts included in measurement of lease liabilities				2,300	2,500
Research and development				$ 44,830	$ 56,434
Harpoon \| Assignment and License Agreement
Loss Contingencies [Line Items]
Reimbursable legal costs	$ 75
Minimum annual royalties	$ 250
License agreement termination, prior written notice required	30 days
Upfront fee paid						$ 500
Adimab \| Development and Option Agreement
Loss Contingencies [Line Items]
Upfront fee paid			$ 100
Research and development			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 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							$ 700		$ 1,000

Net Loss Attributable to Common Stockholders per Share (Tables)

12 Months Ended

Dec. 31, 2025

Earnings Per Share [Abstract]

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

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,
	2025	2024
Outstanding stock options	9,954,872	7,634,937

Warrants to purchase common stock	—	58,904
Common stock to be issued under the 2021 ESPP	85,368	67,445

Total	10,040,240	7,761,286

Schedule of Earnings Per Share, Basic and Diluted

The following table summarizes the computations of basic and diluted net loss per share as presented in our consolidated statements of operations:


	Year Ended December 31,
	2025		2024
	(in thousands, except share and per share amounts)
Numerator
Net loss	$	(60,822)	$	(70,515)
Less: change in fair value of derivative liability	(2,070)		(1,621)
Plus: interest expense on converted term loan	776		493
Adjusted net loss	$	(62,116)	$	(71,643)
Denominator
Weighted-average common stock outstanding, basic	46,018,888		43,332,088
Dilutive effect of common stock issuable from assumed conversion of convertible term loan	791,364		527,576
Weighted-average common stock outstanding, diluted	46,810,252		43,859,664
Net loss per share
Basic	$	(1.32)	$	(1.63)
Diluted	$	(1.33)	$	(1.63)

Common and Preferred Stock (Tables)

12 Months Ended

Dec. 31, 2025

Equity [Abstract]

Schedule of Common Stock Reserved for Issuance

We have reserved shares of common stock for issuance as follows:


	As of December 31,
	2025	2024
Shares reserved for exercises of outstanding stock options	9,954,872	7,634,937

Shares reserved for exercises of warrants	—	58,904
Shares reserved for issuance under the 2021 Employee Stock Purchase Plan	560,929	433,264
Shares reserved for future issuance under the 2021 Stock Incentive Plan	2,039,026	1,919,921
Shares reserved for future issuance as part of the K2HV Loan Agreement conversion feature	791,364	791,364
Total shares reserved for future issuance	13,346,191	10,838,390

Stock-based Compensation - Stock Option Activity (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2025 USD ($) $ / shares shares
Number of Options
Exercised (in shares)	0
Outstanding stock options
Number of Options
Outstanding at beginning of period (in shares)	7,634,937
Granted (in shares)	3,390,691
Exercised (in shares)	0
Cancelled (in shares)	(1,070,756)
Outstanding at end of period (in shares)	9,954,872
Exercisable at end of period (shares)	6,203,856
Weighted-Average Exercise Price per Share
Weighted-Average Exercise Price - Outstanding at beginning of period (in usd per share) \| $ / shares	$ 6.24
Weighted-Average Exercise Price - Granted (in usd per share) \| $ / shares	1.49
Weighted-Average Exercise Price - Exercised (in usd per share) \| $ / shares	0
Weighted-Average Exercise Price - Cancelled (in usd per share) \| $ / shares	5.43
Weighted-Average Exercise Price - Outstanding at end of period (in usd per share) \| $ / shares	4.71
Weighted-Average Exercise Price - Exercisable at end of period (in usd per share) \| $ / shares	$ 6.19
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Additional Disclosures [Abstract]
Weighted Average Remaining Contractual Life - Outstanding	7 years 1 month 28 days
Weighted Average Remaining Contractual Life - Exercisable	6 years 3 months 3 days
Outstanding, Aggregate Intrinsic Value \| $	$ 0.0
Exercisable, Aggregate Intrinsic Value \| $	$ 0.0

Basis of Presentation and Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2025

Accounting Policies [Abstract]

Basis of Presentation and Summary of Significant Accounting Policies

3. 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

We operate in one business segment, which focuses on the discovery and development of cancer therapeutics. Our chief operating decision maker (“CODM”), our Chief Executive Officer, makes operating decisions based upon the performance of the enterprise as a whole and utilizes our 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 accrued expenses and assumptions used in the valuation of stock-based compensation expense and the fair value of the derivative liability. 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 our 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 from us. Unobservable inputs are inputs that reflect our 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 our 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 us 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

Our cash and cash equivalents consist of cash maintained within standard checking accounts. We also maintain cash sweep accounts in which cash from our main operating cash accounts are invested overnight in highly liquid, short-term investments. We consider all highly liquid investments with a maturity date of 90 days or less at the date of purchase to be cash equivalents.

We maintained restricted cash and cash equivalents of $0.9 million and $1.2 million at December 31, 2025 and 2024, respectively. The restricted cash and cash equivalents balances as of December 31, 2025 and 2024 are comprised solely of a letter of credit required pursuant to our leased office spaces (see Note 11, 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, if any, is included in prepaid expenses and other current assets in the accompanying consolidated balance sheets.


	December 31,
	2025		2024
	(in thousands)
Cash and cash equivalents	$	57,050	$	110,995

Restricted cash and cash equivalents	901		1,220
Total cash, cash equivalents and restricted cash and cash equivalents	$	57,951	$	112,215

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. We capitalize 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. We review our 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, we compare 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. We have not recorded any material impairment charges during the years ended December 31, 2025 or 2024.

Leases

At the inception of an arrangement, we determine 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. We do 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 we have 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 we are reasonably certain that the option to extend will be exercised or the option to terminate will not be exercised. We monitor our plans to renew material leases on a quarterly basis.

We combine lease and non-lease components for our 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 us 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, we utilize our incremental borrowing rate (“IBR”), which reflects the fixed rate at which we 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 our leases are classified as operating leases. Operating lease expense is recognized over the lease term using the straight-line method.

Revenue Recognition

We analyze our 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, we first determine 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, we recognize revenue when our 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, we perform 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) we satisfy the performance obligations. We only apply the five-step model to contracts when it is probable that we will collect the consideration to which we are entitled in exchange for the goods or services we provide to the customer. At contract inception, once the contract is determined to be within the scope of ASC 606, we assess the goods or services promised within each contract, determine those that are performance obligations and assess whether each promised good or service is distinct. We then recognize 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, we must develop assumptions that require judgment to determine the standalone selling price for each performance obligation identified in the contract. We use key assumptions to determine the standalone selling price, which may include reimbursement rates for personnel costs, development timelines and probabilities of regulatory success. We do 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 we use the “most likely amount” method to estimate this variable consideration. Given the high degree of uncertainty around the occurrence of these events, we consider 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. We 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

We expense costs associated with intellectual property-related matters as incurred and classify such costs as general and administrative expenses within the consolidated statements of operations.

Stock-based Compensation

We issue 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”). Occasionally, we may also grant inducement equity awards in the form of non-qualified stock options to purchase shares of our common stock to newly hired employees pursuant to Nasdaq Listing Rule 5635(c)(4) (“Inducement Awards”). 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, we estimate 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. We have not granted any awards with market conditions. We recognize forfeitures of stock-based awards as they occur.

The grant date fair value of stock options, Inducement Awards, and awards granted under the 2021 ESPP are measured using the Black-Scholes valuation model, which requires us 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 our 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 our common stock, we 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 our debt instruments is 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. We recognize 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.

We account 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. We recognize any material interest and penalties related to unrecognized tax benefits in income tax expense.

Comprehensive Loss

We do not have items of other comprehensive loss for the years ended December 31, 2025 and 2024, and therefore do not present a consolidated statement of comprehensive loss. Our comprehensive loss equals our 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. The potentially dilutive shares of common stock resulting from the assumed conversion of the currently outstanding convertible term loan is determined using the if-converted method.

Concentration of Credit Risk and Off-Balance Sheet Risk

Financial instruments that potentially subject us to significant concentrations of credit risk consist of cash and cash equivalents. Cash and cash equivalents are primarily held with one reputable financial institution in the United States. At times, such deposits may be in excess of insured limits. We have not experienced any losses on our deposits of cash and cash equivalents. We have no significant off-balance sheet concentrations of credit risk, such as foreign currency exchange contracts, option contracts or other hedging arrangements.

Recently Adopted 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. We adopted ASU No. 2023-09 on January 1, 2025 and have applied the amendments in this update on a prospective basis. The adoption of ASU No. 2023-09 did not have a material impact on our consolidated financial statements. The income tax disclosures required by ASU No. 2023-09 have been included in Note 12.

Recent Accounting Pronouncements

In November 2024, the FASB issued ASU No. 2024-03, Income Statement—Reporting Comprehensive Income—Expense Disaggregation Disclosures (Subtopic 220-04) (“ASU No. 2024-03”), which requires the disclosure of additional information about specific expense categories in the notes to the consolidated financial statements at interim and annual reporting periods. The provisions of ASU No. 2024-03 are effective for annual reporting periods beginning after December 31, 2026, with early adoption permitted, and may be applied on a prospective or retrospective basis. We are currently evaluating the impact that this standard will have on our consolidated financial statements and have not yet selected a transition method.

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 our consolidated financial statements upon adoption.

Subsequent Events

We have 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 consolidated financial statements, we did not identify any subsequent events that would have required adjustment to or disclosure in the consolidated financial statements.

Consolidated Statements of Stockholders’ Equity (Parentheticals) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Market Offering
Issuance costs	$ 534	$ 1,283

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, 2023			39,107,048
Stockholders' equity, beginning balance at Dec. 31, 2023	$ 111,374		$ 4		$ 455,443		$ (344,073)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock from at the market offering, net of issuance costs (in shares)			430,349	5,272,538
Issuance of common stock from at the market offering, net of issuance costs	142	$ 23,528		$ 1	142	$ 23,527
Stock-based compensation expense	8,826				8,826
Stock option exercises (in shares)			17,224
Stock option exercises	35				35
Net loss	$ (70,515)						(70,515)
Stockholders' equity, ending balance (in shares) at Dec. 31, 2024	44,827,159		44,827,159
Stockholders' equity, ending balance at Dec. 31, 2024	$ 73,390		$ 5		487,973		(414,588)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock from at the market offering, net of issuance costs (in shares)			142,957	3,626,701
Issuance of common stock from at the market offering, net of issuance costs	89	$ 5,903			89	$ 5,903
Stock-based compensation expense	$ 6,245				6,245
Stock option exercises (in shares)	0
Net loss	$ (60,822)						(60,822)
Stockholders' equity, ending balance (in shares) at Dec. 31, 2025	48,596,817		48,596,817
Stockholders' equity, ending balance at Dec. 31, 2025	$ 24,805		$ 5		$ 500,210		$ (475,410)

- Definition

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

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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.

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+ Details

Segment Information (Details) $ in Thousands	12 Months Ended
Segment Information (Details) $ in Thousands	Dec. 31, 2025 USD ($) segment	Dec. 31, 2024 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments \| segment	1
Interest income	$ 3,108	$ 6,673
Interest expense	(5,274)	(4,656)
Loss on extinguishment of debt	0	(553)
Other income, net	2,021	1,615
Net loss	(60,822)	(70,515)
Reportable Segment
Segment Reporting Information [Line Items]
Collaboration revenue	0	1,885
Clinical development	19,187	16,361
Research and discovery	12,660	14,389
General and administrative support	12,428	14,330
Manufacturing	8,523	19,759
Other segment expenses	7,879	10,640
Interest income	3,108	6,673
Interest expense	(5,274)	(4,656)
Loss on extinguishment of debt	0	(553)
Other income, net	2,021	1,615
Net loss	$ (60,822)	$ (70,515)

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Current assets:
Cash and cash equivalents	$ 57,050	$ 110,995
Prepaid expenses and other current assets	1,536	2,071
Total current assets	58,586	113,066
Property and equipment, net	4,688	6,322
Restricted cash and cash equivalents	901	1,220
Operating lease right of use asset	5,216	6,001
Other assets	5	320
Total assets	69,396	126,929
Current liabilities:
Accounts payable	754	3,035
Accrued expenses and other current liabilities	5,407	10,588
Operating lease liability, current	1,751	1,557
Note payable, current, net of discount and issuance costs	28,236	0
Total current liabilities	36,148	15,180
Operating lease liability, net of current portion	7,684	9,435
Note payable, net of discount, issuance costs, and current portion	0	26,095
Derivative liability	759	2,829
Total liabilities	44,591	53,539
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $0.0001 par value, 5,000,000 shares authorized as of December 31, 2025 and 2024; no shares issued or outstanding as of December 31, 2025 and 2024	0	0
Common stock, $0.0001 par value, 200,000,000 shares authorized as of December 31, 2025 and 2024; 48,596,817 and 44,827,159 shares issued and outstanding as of December 31, 2025 and 2024, respectively	5	5
Additional paid-in capital	500,210	487,973
Accumulated deficit	(475,410)	(414,588)
Total stockholders’ equity	24,805	73,390
Total liabilities and stockholders’ equity	$ 69,396	$ 126,929
Common stock outstanding (in shares)	48,596,817	44,827,159

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

12 Months Ended

Dec. 31, 2025

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

Use of Estimates

Fair Value of Financial Instruments

•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

Leases

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

Revenue Recognition

Research and Development Expenses

Intellectual Property Expenses

We expense costs associated with intellectual property-related matters as incurred and classify such costs as general and administrative expenses within the consolidated statements of operations.

Stock-based Compensation

recognized over the requisite service period. We have not granted any awards with market conditions. We recognize forfeitures of stock-based awards as they occur.

Debt Issuance Costs

Equity Issuance Costs

Income Taxes

Comprehensive Loss

Basic and Diluted Net Loss per Common Share

Concentration of Credit Risk

Concentration of Credit Risk and Off-Balance Sheet Risk

Off-Balance Sheet Risk

We have no significant off-balance sheet concentrations of credit risk, such as foreign currency exchange contracts, option contracts or other hedging arrangements.

Recently Adopted Accounting Pronouncements and Recent Accounting Pronouncements

Recently Adopted Accounting Pronouncements

Recent Accounting Pronouncements

Subsequent Events

Insider Trading Policies and Procedures	12 Months Ended
Insider Trading Policies and Procedures	Dec. 31, 2025
Insider Trading Policies and Procedures [Line Items]
Insider Trading Policies and Procedures Adopted	true

Stock-based Compensation

12 Months Ended

Dec. 31, 2025

Share-Based Payment Arrangement [Abstract]

Stock-based Compensation

10. Stock-based Compensation

2017 Stock Incentive Plan

In December 2017, we adopted the 2017 Stock Incentive Plan (the “2017 Plan”), as amended and restated, pursuant to which we have outstanding stock options. No future awards may be granted under the 2017 Plan.

2021 Stock Incentive Plan

In April 2021, our board of directors adopted and our stockholders approved the 2021 Stock Incentive Plan (the “2021 Plan”), which became effective immediately prior to the effectiveness of our 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 incentive stock options (“ISOs”), non-qualified stock options, RSAs, RSUs, stock appreciation rights and other stock-based awards. Our 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 our board of directors, subject to the provisions of the 2021 Plan.

We 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 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 ending 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, 2025, a total of 7,152,859 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, 2025, there were 2,039,026 shares available for future issuance under the 2021 Plan.

2021 Employee Stock Purchase Plan

The 2021 ESPP permits eligible employees to purchase shares of our 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 our 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 our 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, 2025, 96,470 shares of our common stock were purchased by participants of the 2021 ESPP for total proceeds of $0.1 million. During the year ended December 31, 2024, 73,849 shares of our common stock were purchased by participants of the 2021 ESPP for total proceeds of $0.1 million.

Inducement Stock Option Awards

During the year ended December 31, 2025, we granted 201,720 Inducement Awards. No Inducement Awards were granted during the year ended December 31, 2024. The valuation assumptions and activity associated with Inducement Awards are included in the stock option activity described below.

Stock-Based Compensation Expense

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


	Year Ended December 31,
	2025		2024
	(in thousands)
Research and development	$	3,201	$	4,606
General and administrative	3,044		4,220
Total stock-based compensation	$	6,245	$	8,826

RSU Activity

We have granted RSUs to our employees under the 2021 Plan. As of December 31, 2024, all RSUs granted to employees or non-employees had become fully vested or had been previously forfeited. No RSUs were granted during the year ended December 31, 2025. Accordingly, we had no unrecognized stock-based compensation expense related to unvested RSUs as of

December 31, 2025. The aggregate fair value of RSUs that vested during the year ended December 31, 2024, based upon the fair value of the stock underlying the RSUs on the day of vesting was $1.0 million.

Stock Option Activity

The fair value of stock options granted during the years ended December 31, 2025 and 2024 was calculated on the date of grant using the following weighted-average assumptions:


	Year Ended December 31,
	2025		2024
Risk-free interest rate	4.4	%	4.0	%
Expected term (in years)	5.9		6.0
Expected annual dividend yield	—	%	—	%
Expected volatility	95.4	%	92.7	%

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. We use 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 we have no history of paying dividends, and do not intend to do so in the foreseeable future.

•Expected volatility: The expected term of stock options granted by us is generally longer than the trading history of our common stock since the IPO on April 30, 2021. Accordingly, we estimated the expected volatility based on the historical volatility of a group of publicly-traded companies with similar characteristics to us, 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, 2025 and 2024 was $1.16 and $3.43 per share, respectively.

The following table summarizes stock option activity during the year ended December 31, 2025:


	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, 2024	7,634,937	$	6.24
Granted	3,390,691	$	1.49
Exercised	—	$	—
Cancelled	(1,070,756)	$	5.43
Outstanding, December 31, 2025	9,954,872	$	4.71	7.16	$	—
Exercisable at December 31, 2025	6,203,856	$	6.19	6.26	$	—

No stock options were exercised during the year ended December 31, 2025. The aggregate intrinsic fair value of stock options exercised during the year ended December 31, 2024 was nominal.

As of December 31, 2025, we had unrecognized stock-based compensation expense related to unvested stock options of $5.4 million, which we expect to recognize over a weighted-average period of approximately 1.9 years.

Cybersecurity Risk Management and Strategy Disclosure	12 Months Ended
Cybersecurity Risk Management and Strategy Disclosure	Dec. 31, 2025
Cybersecurity Risk Management, Strategy, and Governance [Line Items]
Cybersecurity Risk Management Processes for Assessing, Identifying, and Managing Threats [Text Block]	We have certain processes for the identification, assessment, and mitigation of cybersecurity risks which are incorporated into our overall risk management processes in coordination with our information technology function. Such processes include physical, procedural and technical safeguards, and routine review of our policies and procedures to identify risks and improve our practices. We conduct cybersecurity training and testing for all of our employees covering timely and relevant topics, including social engineering, phishing, password protection, confidential data protection, and mobile security, and we educate employees on the importance of reporting all incidents immediately. We also use technology-based tools to mitigate cybersecurity risks and to bolster our employee-based cybersecurity programs. We engage third-party consultants to enhance our cybersecurity oversight and conduct penetration testing and vulnerability assessments. Further, we consider the cybersecurity practices of our third-party service providers, including through a general security assessment and contractual requirements, as appropriate, before engaging them in order to help protect us from any related vulnerabilities. We do not believe that there are currently any risks from known cybersecurity threats that are reasonably likely to materially affect us or our business strategy, results of operations or financial condition. For more information about the cybersecurity risks we face, see the risk factors entitled “Our business could be negatively affected by cyberattacks or a deficiency in our cybersecurity” and “Our internal computer systems, or those used by our third-party research institution collaborators, CROs or other contractors or consultants, may fail or suffer security breaches” in the section titled “Risk Factors” in Part 1, Item 1A of this Annual Report.
Cybersecurity Risk Management Processes Integrated [Flag]	true
Cybersecurity Risk Management Processes Integrated [Text Block]	We have certain processes for the identification, assessment, and mitigation of cybersecurity risks which are incorporated into our overall risk management processes in coordination with our information technology function. Such processes include physical, procedural and technical safeguards, and routine review of our policies and procedures to identify risks and improve our practices. We conduct cybersecurity training and testing for all of our employees covering timely and relevant topics, including social engineering, phishing, password protection, confidential data protection, and mobile security, and we educate employees on the importance of reporting all incidents immediately. We also use technology-based tools to mitigate cybersecurity risks and to bolster our employee-based cybersecurity programs. We engage third-party consultants to enhance our cybersecurity oversight and conduct penetration testing and vulnerability assessments. Further, we consider the cybersecurity practices of our third-party service providers, including through a general security assessment and contractual requirements, as appropriate, before engaging them in order to help protect us from any related vulnerabilities.
Cybersecurity Risk Management Third Party Engaged [Flag]	true
Cybersecurity Risk Third Party Oversight and Identification Processes [Flag]	true
Cybersecurity Risk Materially Affected or Reasonably Likely to Materially Affect Registrant [Flag]	false
Cybersecurity Risk Board of Directors Oversight [Text Block]	Our Director of Operations leads the operational oversight of the company-wide cybersecurity strategy, policy, standards and processes. The Director of Operations role is currently held by an individual who has over two decades of professional IT management experience and possesses the requisite education, skills and experience expected to perform such a duty. In addition, our Director of Operations as well as leaders from our operations, finance, and legal departments, are responsible for documenting, reviewing, and assessing our cybersecurity processes, monitoring for cybersecurity incidents, and periodically reporting on cybersecurity risks and risk management to the audit committee of our board of directors. The audit committee of the board of directors provides oversight of our cybersecurity risk as part of its periodic review of enterprise risk management. The audit committee provides regular updates to our board of directors regarding such oversight, including updates on the status of ongoing cybersecurity projects, the results of cybersecurity risk assessments, and the emerging cybersecurity threat landscape. Additionally, the board of directors reviews our enterprise risk management processes periodically and is notified by management between management updates regarding significant new cybersecurity threats or incidents.
Cybersecurity Risk Board Committee or Subcommittee Responsible for Oversight [Text Block]	Our Director of Operations leads the operational oversight of the company-wide cybersecurity strategy, policy, standards and processes. The Director of Operations role is currently held by an individual who has over two decades of professional IT management experience and possesses the requisite education, skills and experience expected to perform such a duty. In addition, our Director of Operations as well as leaders from our operations, finance, and legal departments, are responsible for documenting, reviewing, and assessing our cybersecurity processes, monitoring for cybersecurity incidents, and periodically reporting on cybersecurity risks and risk management to the audit committee of our board of directors. The audit committee of the board of directors provides oversight of our cybersecurity risk as part of its periodic review of enterprise risk management. The audit committee provides regular updates to our board of directors regarding such oversight, including updates on the status of ongoing cybersecurity projects, the results of cybersecurity risk assessments, and the emerging cybersecurity threat landscape. Additionally, the board of directors reviews our enterprise risk management processes periodically and is notified by management between management updates regarding significant new cybersecurity threats or incidents.
Cybersecurity Risk Process for Informing Board Committee or Subcommittee Responsible for Oversight [Text Block]	Our Director of Operations leads the operational oversight of the company-wide cybersecurity strategy, policy, standards and processes. The Director of Operations role is currently held by an individual who has over two decades of professional IT management experience and possesses the requisite education, skills and experience expected to perform such a duty. In addition, our Director of Operations as well as leaders from our operations, finance, and legal departments, are responsible for documenting, reviewing, and assessing our cybersecurity processes, monitoring for cybersecurity incidents, and periodically reporting on cybersecurity risks and risk management to the audit committee of our board of directors. The audit committee of the board of directors provides oversight of our cybersecurity risk as part of its periodic review of enterprise risk management. The audit committee provides regular updates to our board of directors regarding such oversight, including updates on the status of ongoing cybersecurity projects, the results of cybersecurity risk assessments, and the emerging cybersecurity threat landscape. Additionally, the board of directors reviews our enterprise risk management processes periodically and is notified by management between management updates regarding significant new cybersecurity threats or incidents.
Cybersecurity Risk Role of Management [Text Block]	Our Director of Operations leads the operational oversight of the company-wide cybersecurity strategy, policy, standards and processes. The Director of Operations role is currently held by an individual who has over two decades of professional IT management experience and possesses the requisite education, skills and experience expected to perform such a duty. In addition, our Director of Operations as well as leaders from our operations, finance, and legal departments, are responsible for documenting, reviewing, and assessing our cybersecurity processes, monitoring for cybersecurity incidents, and periodically reporting on cybersecurity risks and risk management to the audit committee of our board of directors. The audit committee of the board of directors provides oversight of our cybersecurity risk as part of its periodic review of enterprise risk management. The audit committee provides regular updates to our board of directors regarding such oversight, including updates on the status of ongoing cybersecurity projects, the results of cybersecurity risk assessments, and the emerging cybersecurity threat landscape. Additionally, the board of directors reviews our enterprise risk management processes periodically and is notified by management between management updates regarding significant new cybersecurity threats or incidents.
Cybersecurity Risk Management Positions or Committees Responsible [Flag]	true
Cybersecurity Risk Management Positions or Committees Responsible [Text Block]	Our Director of Operations leads the operational oversight of the company-wide cybersecurity strategy, policy, standards and processes. The Director of Operations role is currently held by an individual who has over two decades of professional IT management experience and possesses the requisite education, skills and experience expected to perform such a duty. In addition, our Director of Operations as well as leaders from our operations, finance, and legal departments, are responsible for documenting, reviewing, and assessing our cybersecurity processes, monitoring for cybersecurity incidents, and periodically reporting on cybersecurity risks and risk management to the audit committee of our board of directors. The audit committee of the board of directors provides oversight of our cybersecurity risk as part of its periodic review of enterprise risk management. The audit committee provides regular updates to our board of directors regarding such oversight, including updates on the status of ongoing cybersecurity projects, the results of cybersecurity risk assessments, and the emerging cybersecurity threat landscape. Additionally, the board of directors reviews our enterprise risk management processes periodically and is notified by management between management updates regarding significant new cybersecurity threats or incidents.
Cybersecurity Risk Management Expertise of Management Responsible [Text Block]	The Director of Operations role is currently held by an individual who has over two decades of professional IT management experience and possesses the requisite education, skills and experience expected to perform such a duty. In addition, our Director of Operations as well as leaders from our operations, finance, and legal departments, are responsible for documenting, reviewing, and assessing our cybersecurity processes, monitoring for cybersecurity incidents, and periodically reporting on cybersecurity risks and risk management to the audit committee of our board of directors.
Cybersecurity Risk Process for Informing Management or Committees Responsible [Text Block]	Our Director of Operations leads the operational oversight of the company-wide cybersecurity strategy, policy, standards and processes. The Director of Operations role is currently held by an individual who has over two decades of professional IT management experience and possesses the requisite education, skills and experience expected to perform such a duty. In addition, our Director of Operations as well as leaders from our operations, finance, and legal departments, are responsible for documenting, reviewing, and assessing our cybersecurity processes, monitoring for cybersecurity incidents, and periodically reporting on cybersecurity risks and risk management to the audit committee of our board of directors. The audit committee of the board of directors provides oversight of our cybersecurity risk as part of its periodic review of enterprise risk management. The audit committee provides regular updates to our board of directors regarding such oversight, including updates on the status of ongoing cybersecurity projects, the results of cybersecurity risk assessments, and the emerging cybersecurity threat landscape. Additionally, the board of directors reviews our enterprise risk management processes periodically and is notified by management between management updates regarding significant new cybersecurity threats or incidents.
Cybersecurity Risk Management Positions or Committees Responsible Report to Board [Flag]	true

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Revenue:
Collaboration revenue	$ 0	$ 1,885
Operating expenses:
Research and development	44,830	56,434
General and administrative	15,847	19,045
Total operating expenses	60,677	75,479
Operating loss	(60,677)	(73,594)
Other (expense) income:
Interest income	3,108	6,673
Interest expense	(5,274)	(4,656)
Loss on extinguishment of debt	0	(553)
Other income, net	2,021	1,615
Total other (expense) income	(145)	3,079
Net loss	$ (60,822)	$ (70,515)
Net loss per share attributable to common stockholders, basic and diluted
Net loss per common share, basic (in usd per share)	$ (1.32)	$ (1.63)
Net loss per common share, diluted (in usd per share)	$ (1.33)	$ (1.63)
Weighted-average common shares outstanding, basic and diluted
Weighted average common shares outstanding, basic (in shares)	46,018,888	43,332,088
Weighted average common shares outstanding, diluted (in shares)	46,810,252	43,859,664

Term Loan (Tables)

12 Months Ended

Dec. 31, 2025

Debt Disclosure [Abstract]

Schedule of Long-Term Debt Instruments

The outstanding term loans payable consists of the following:


	December 31,
	2025		2024
	(in thousands)
Note payable	$	30,000	$	30,000
Unamortized debt discount and issuance costs	(1,764)		(3,905)
Net carrying amount of note payable	28,236		26,095
Less: current portion of note payable	(28,236)		—
Note payable, net, less current portion	$	—	$	26,095

The following table provides the components of interest expense related to the K2HV Loan Agreement:


	Year Ended December 31,
	2025		2024
	(in thousands)
Interest expense based on coupon interest rate (10.3%) of outstanding term loans	$	3,133	$	2,094
Amortization of debt discount and accretion of Final Fee (8.94%)	2,141		1,217
Total interest expense on effective rate (19.24%)	$	5,274	$	3,311

Schedule of Principal Payments and Final Fee

The following table presents the total principal payments and Final Fee contractually scheduled to become due during each of the years ended December 31 (in thousands):





2026	$	9,600
2027	14,400
2028	8,085
Total principal payments and Final Fee	$	32,085

- 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.

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Reference 12: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Section 50
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-URI https://asc.fasb.org/1943274/2147481112/505-10-50-7

+ Details

Net Loss Attributable to Common Stockholders per Share - Summary of Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Earnings Per Share [Abstract]
Net loss	$ (60,822)	$ (70,515)
Less: change in fair value of derivative liability	(2,070)	(1,621)
Plus: interest expense on converted term loan	776	493
Adjusted net loss	$ (62,116)	$ (71,643)
Weighted average common shares outstanding, basic (in shares)	46,018,888	43,332,088
Dilutive effect of common stock issuable from assumed conversion of convertible term loan (in shares)	791,364	527,576
Weighted average common shares outstanding, diluted (in shares)	46,810,252	43,859,664
Net loss per common share, basic (in usd per share)	$ (1.32)	$ (1.63)
Net loss per common share, diluted (in usd per share)	$ (1.33)	$ (1.63)

Common and Preferred Stock - Schedule of Common Stock Reserved for Issuance (Details) - shares	Dec. 31, 2025	Dec. 31, 2024
Class of Stock [Line Items]
Common stock available for issuance (in shares)	13,346,191	10,838,390
Shares reserved for exercises of outstanding stock options
Class of Stock [Line Items]
Common stock available for issuance (in shares)	9,954,872	7,634,937
Shares reserved for exercises of warrants
Class of Stock [Line Items]
Common stock available for issuance (in shares)	0	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)	560,929	433,264
Shares reserved for future issuance under the 2021 Stock Incentive Plan
Class of Stock [Line Items]
Common stock available for issuance (in shares)	2,039,026	1,919,921
Shares reserved for future issuance as part of the K2HV Loan Agreement conversion feature
Class of Stock [Line Items]
Common stock available for issuance (in shares)	791,364	791,364

- 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.

+ References

+ Details

Related Parties (Details) - USD ($) $ in Millions	12 Months Ended
Related Parties (Details) - USD ($) $ in Millions	Dec. 31, 2024	Jun. 30, 2022
Related Party Transactions [Abstract]
Sublease cash payments received	$ 0.4
Security deposit liability		$ 0.2

Related Parties	12 Months Ended
Related Parties	Dec. 31, 2025
Related Party Transactions [Abstract]
Related Parties	13. Related Parties In May 2022, we 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 our office and laboratory space in Cambridge, Massachusetts. Luke Evnin, Ph.D., the chair of our board of directors, co-founded MPM Capital and serves as Managing Director of MPM Capital. Briggs Morrison, who serves on our 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 ended in March 2024, with no option to extend (see Note 11, Commitments and Contingencies). We received cash payments under our sublease of $0.4 million during the year ended December 31, 2024. In addition, we received $0.2 million from Crossbow in June 2022 as a security deposit, which was remitted to Crossbow following the termination of the sublease.

- 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

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+ Details