0001785530-26-000012 | 10-Q | XBRL Viewer | Werewolf Therapeutics INC

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Net Loss Attributable to Common Stockholders per Share - Schedule of Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Numerator
Net loss	$ (13,532)	$ (18,089)
Less: change in fair value of derivative liability	(674)	0
Plus: interest expense on converted term loan	199	0
Adjusted net loss	$ (14,007)	$ (18,089)
Denominator
Weighted-average common stock outstanding, basic (in shares)	48,596,817	44,827,159
Dilutive effect of common stock issuable from assumed conversion of convertible term loan (in shares)	791,364	0
Weighted-average common stock outstanding, diluted (in shares)	49,388,181	44,827,159
Net loss per share
Basic (in usd per share)	$ (0.28)	$ (0.40)
Diluted (in usd per share)	$ (0.28)	$ (0.40)

Summary of Significant Accounting Policies	3 Months Ended
Summary of Significant Accounting Policies	Mar. 31, 2026
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	3. Summary of Significant Accounting Policies Basis of Presentation and Consolidation The accompanying condensed consolidated financial statements as of March 31, 2026 and December 31, 2025, and for the three months ended March 31, 2026 and 2025, 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”) for condensed consolidated financial information. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, these condensed consolidated financial statements reflect all normal recurring adjustments which are necessary for a fair presentation of our financial position and results of our operations, as of and for the periods presented. These condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes thereto contained in our Annual Report on Form 10-K for the year ended December 31, 2025 filed with the SEC on March 27, 2026 (the “2025 Annual Report”). The information presented in the condensed consolidated financial statements and related notes as of March 31, 2026, and for the three months ended March 31, 2026 and 2025, is unaudited. The December 31, 2025 condensed consolidated balance sheet included herein was derived from the audited financial statements as of that date, but does not include all disclosures, including notes, required by GAAP for complete financial statements. Interim results for the three months ended March 31, 2026 are not necessarily indicative of the results that may be expected for the fiscal year ending December 31, 2026, or any future period. The accompanying condensed 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. Summary of Significant Accounting Policies The significant accounting policies and estimates used in the preparation of the condensed consolidated financial statements are described in our audited financial statements as of and for the year ended December 31, 2025, and the notes thereto, which are included in our 2025 Annual Report. Other than as set forth below, there have been no material changes in our significant accounting policies during the three months ended March 31, 2026. 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 condensed 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. 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. We are currently evaluating the impact that this standard will have on our consolidated financial statements. Other accounting standards that have been issued or proposed by the FASB or other standards-setting bodies that do not require adoption until a future date are not expected to have a material impact on 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 Note 12, we did not identify any subsequent events that require adjustment or disclosure in the condensed consolidated financial statements.

Strategic Review and Liquidity

3 Months Ended

Mar. 31, 2026

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 (the “2026 Restructuring”) 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 include the asset purchase agreement described in Note 12, and may also include, among other options, a sale of 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 2026 Restructuring, 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. See Note 11 for further discussion of the impact of the 2026 Restructuring.

We had cash and cash equivalents of $46.5 million at March 31, 2026. The outcome of our strategic review process will inform future development plans and the costs associated with those efforts. We expect to incur substantial operating losses and negative cash flows from operations for the foreseeable future as we continue to execute on our strategic review process. Our ability to maintain ongoing operations is dependent on our ability to obtain additional financing, as to which we can make no assurance. These conditions raise substantial doubt about our ability to continue as a going concern for at least twelve months from the date these condensed consolidated financial statements are issued in this Quarterly 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 condensed 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 condensed consolidated financial statements do not include any adjustments that might result from the outcome of the conditions described above.

11. Restructuring

In February 2026, we initiated a strategic review process and the 2026 Restructuring. The 2026 Restructuring is expected to be completed by the end of 2026.

We estimate that we will incur approximately $6.4 million in costs associated with the 2026 Restructuring, consisting of severance payments, retention bonuses, employee benefits and related taxes, stock-based compensation, and contract termination costs. Our estimate of costs we expect to incur and the expected timing of when the 2026 Restructuring will be

completed are subject to a number of assumptions, and actual results may differ. We may also incur additional costs, including, but not limited to, potential impairment charges and debt extinguishment costs related to the subsequent events described in Note 12, and other events not currently contemplated that may occur as a result of, or that are associated with the 2026 Restructuring.

The following table summarizes the restructuring costs incurred and the total estimated costs expected to be incurred in connection with the 2026 Restructuring:


	Three Months Ended March 31, 2026		Cumulative Costs to Date		Total Estimated Costs
	(in thousands)
Employee severance, benefits and related taxes	$	2,557	$	2,557	$	2,557
Employee retention bonuses, benefits and related taxes	783		783		2,865
Stock-based compensation	615		615		615
Contract termination costs	350		350		350
Total restructuring costs	$	4,305	$	4,305	$	6,387

Total restructuring costs recognized in our condensed consolidated statements of operations were as follows:


	Three Months Ended March 31,
	2026		2025
	(in thousands)
Research and development	$	3,058	$	—
General and administrative	1,247		—
Total restructuring costs	$	4,305	$	—

Accrued restructuring costs, which are included in accrued expenses and other current liabilities on our condensed consolidated balance sheets, were as follows:


	Three Months Ended March 31,
	2026		2025
	(in thousands)
Balance at beginning of period	$	—	$	—
Restructuring costs recognized during the period	4,305		—
Cash payments made during the period	(3,971)		—
Employee retention bonuses paid in advance	724		—
Non-cash charges recognized during the period	(615)		—
Balance at end of period	$	443	$	—

Segment Information (Details) $ in Thousands	3 Months Ended
Segment Information (Details) $ in Thousands	Mar. 31, 2026 USD ($) segment	Mar. 31, 2025 USD ($)
Segment Reporting [Abstract]
Number of reportable segments \| segment	1
Segment Reporting Information [Line Items]
Interest income	$ 433	$ 997
Interest expense	(1,368)	(1,263)
Other income, net	674	168
Net loss	(13,532)	(18,089)
Reportable Segment
Segment Reporting Information [Line Items]
General and administrative support	4,572	3,823
Clinical development	3,643	4,329
Research and discovery	2,155	3,319
Manufacturing	1,574	4,088
Other segment expenses	1,327	2,432
Interest income	433	997
Interest expense	(1,368)	(1,263)
Other income, net	674	168
Net loss	$ (13,532)	$ (18,089)

Stock-based Compensation

3 Months Ended

Mar. 31, 2026

Share-Based Payment Arrangement [Abstract]

Stock-based Compensation

8. 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, restricted stock awards (“RSAs”), restricted stock units (“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 shares of outstanding common stock on such date and (ii) such amount as determined by our board of directors. As of March 31, 2026, a cumulative total of 9,582,699 additional shares have been added to the total shares authorized for issuance under the 2021 Plan in accordance with these terms.

2021 Employee Stock Purchase Plan

The 2021 Employee Stock Purchase Plan (“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 three months ended March 31, 2026 and 2025, no shares of our common stock were purchased by participants of the 2021 ESPP.

Stock-Based Compensation Expense

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


	Three Months Ended March 31,
	2026		2025
	(in thousands)
Research and development	$	503	$	1,055
General and administrative	426		951
Total stock-based compensation	$	929	$	2,006

As part of the severance benefits offered to former employees impacted by the 2026 Restructuring described in Note 2 (the “Former Employees”), the forfeiture conditions of outstanding stock options belonging to the Former Employees were modified such that the Former Employees will retain their rights to exercise their stock options through the original expiration dates of each respective stock option to the extent that such stock options had become vested at the time that the Former Employees’ employment with us was terminated. Absent this modification, the impacted stock options would have been forfeited by the Former Employees after a period of 90 days following the termination of their employment with us, if not exercised sooner. The expiration date for all stock options impacted by this modification will occur on the tenth anniversary of the grant date of each respective stock option. For the three months ended March 31, 2026, the stock-based compensation expense above includes $0.6 million of expense recognized as a one-time charge related to this modification.

Stock Option Activity

No stock options were granted during the three months ended March 31, 2026. The fair value of stock options granted during the three months ended March 31, 2025 was calculated on the date of grant using the following weighted-average assumptions:




Risk-free interest rate	4.4	%
Expected term (in years)	5.9
Expected annual dividend yield	—	%
Expected volatility	95.3	%

Using the Black-Scholes option pricing model, the weighted-average grant date fair value of stock options granted during the three months ended March 31, 2025 was $1.22 per share.

The following table summarizes stock option activity during the three months ended March 31, 2026:


	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, 2025	9,954,872	$	4.71
Granted	—	$	—
Exercised	—	$	—
Cancelled	(1,514,639)	$	2.38
Outstanding at March 31, 2026	8,440,233	$	5.13	6.66	$	—
Exercisable at March 31, 2026	6,600,515	$	5.97	6.15	$	—

No stock options were exercised during the three months ended March 31, 2026 and 2025.

As of March 31, 2026, we had unrecognized stock-based compensation expense related to unvested stock options of $2.6 million, which we expect to recognize over a weighted-average period of approximately 1.9 years.

Stock-based Compensation (Tables)

3 Months Ended

Mar. 31, 2026

Share-Based Payment Arrangement [Abstract]

Schedule of Stock-based Compensation Expense Recognized

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


	Three Months Ended March 31,
	2026		2025
	(in thousands)
Research and development	$	503	$	1,055
General and administrative	426		951
Total stock-based compensation	$	929	$	2,006

Schedule of Weighted -average Valuation Assumptions

The fair value of stock options granted during the three months ended March 31, 2025 was calculated on the date of grant using the following weighted-average assumptions:




Risk-free interest rate	4.4	%
Expected term (in years)	5.9
Expected annual dividend yield	—	%
Expected volatility	95.3	%

Schedule of Stock Option Activity

The following table summarizes stock option activity during the three months ended March 31, 2026:


	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, 2025	9,954,872	$	4.71
Granted	—	$	—
Exercised	—	$	—
Cancelled	(1,514,639)	$	2.38
Outstanding at March 31, 2026	8,440,233	$	5.13	6.66	$	—
Exercisable at March 31, 2026	6,600,515	$	5.97	6.15	$	—

Financial Instruments and Fair Value Measurements - Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025
Assets:
Total assets	$ 46,276	$ 56,548
Liabilities:
Derivative liability	85	759
Total liabilities	85	759
Money market funds
Assets:
Money market funds	46,276	56,548
Level 1
Assets:
Total assets	46,276	56,548
Liabilities:
Derivative liability	0	0
Total liabilities	0	0
Level 1 \| Money market funds
Assets:
Money market funds	46,276	56,548
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	85	759
Total liabilities	85	759
Level 3 \| Money market funds
Assets:
Money market funds	$ 0	$ 0

Stock-based Compensation - Schedule of Weighted Average Assumptions (Details) - Outstanding stock options	3 Months Ended
	Mar. 31, 2025
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Risk-free interest rate	4.40%
Expected term (in years)	5 years 10 months 24 days
Expected annual dividend yield	0.00%
Expected volatility	95.30%

Term Loan - Narrative (Details) - USD ($) $ in Millions	1 Months Ended
Term Loan - Narrative (Details) - USD ($) $ in Millions	May 31, 2024	Mar. 31, 2026
Level 3
Debt Instrument [Line Items]
Fair value of derivative liability at issuance of term loan	$ 4.5
Common stock to be issued upon exercise of the K2HV Loan Agreement conversion feature
Debt Instrument [Line Items]
Loan agreement, amount	60.0
Proceeds from drawdown of term loans	30.0
Amount of net cash proceeds from certain financing activities	60.0
Minimum amount of offering of common stock	$ 50.0
Debt instrument variable rate floor (percent)	10.30%
Floating rate spread in effect (greater than) (percent)	1.80%
Final fee, percentage	6.95%
Conversion of outstanding principal	$ 5.0
Additional interest rate (percent)	0.050
Allowable amount to invest in future offerings	$ 5.0
Common stock to be issued upon exercise of the K2HV Loan Agreement conversion feature \| Minimum
Debt Instrument [Line Items]
Adjustment rate (percent)	9.99%
Common stock to be issued upon exercise of the K2HV Loan Agreement conversion feature \| Maximum
Debt Instrument [Line Items]
Adjustment rate (percent)	19.99%
Common stock to be issued upon exercise of the K2HV Loan Agreement conversion feature \| Period One
Debt Instrument [Line Items]
Proceeds from drawdown of term loans	$ 25.0
Period for interest only payments (in months)	24 months
Common stock to be issued upon exercise of the K2HV Loan Agreement conversion feature \| Period Two
Debt Instrument [Line Items]
Proceeds from drawdown of term loans	$ 5.0
Common stock to be issued upon exercise of the K2HV Loan Agreement conversion feature \| Period Three
Debt Instrument [Line Items]
Capacity available to draw on the term loans	10.0
Common stock to be issued upon exercise of the K2HV Loan Agreement conversion feature \| Period Four
Debt Instrument [Line Items]
Capacity available to draw on the term loans	20.0
Term Loans
Debt Instrument [Line Items]
Payment of debt issuance costs	0.7
Facility fee	0.4
Payments for other fees and expenses	0.2
Debt instrument, final fee amount	0.1
Debt discount	$ 5.1
Long-term debt, fair value		$ 29.7

Common and Preferred Stock - Schedule of Common Stock Reserved for Issuance (Details) - shares	Mar. 31, 2026	Dec. 31, 2025
Class of Stock [Line Items]
Common stock available for issuance (in shares)	16,266,036	13,346,191
Shares reserved for exercises of outstanding stock options
Class of Stock [Line Items]
Common stock available for issuance (in shares)	8,440,233	9,954,872
Shares reserved for issuance under the 2021 Employee Stock Purchase Plan
Class of Stock [Line Items]
Common stock available for issuance (in shares)	1,046,897	560,929
Shares reserved for issuance under the 2021 Stock Incentive Plan
Class of Stock [Line Items]
Common stock available for issuance (in shares)	5,987,542	2,039,026
Shares reserved for 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

Term Loan - Schedule of Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Debt Disclosure [Abstract]
Coupon rate (percent)	10.30%
Accretion of debt discount (percent)	8.94%
Effective interest rate (percent)	19.24%
Interest expense based on coupon interest rate (10.3%) of outstanding term loans	$ 773	$ 773
Amortization of debt discount and accretion of Final Fee (8.94%)	595	490
Total interest expense on effective rate (19.24%)	$ 1,368	$ 1,263

Term Loan - Schedule of Outstanding Term Loans Payable (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025
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	(1,169)	(1,764)
Net carrying amount of note payable	$ 28,831	$ 28,236

- 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

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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

Financial Instruments and Fair Value Measurements

3 Months Ended

Mar. 31, 2026

Fair Value Disclosures [Abstract]

Financial Instruments and Fair Value Measurements

4. 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 and cash equivalents on our condensed consolidated balance sheets as of March 31, 2026 and December 31, 2025.

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 6, Term Loan) on our condensed consolidated balance sheets as of March 31, 2026 and December 31, 2025.

The carrying amounts reflected in the condensed 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 March 31, 2026 were as follows:


	Level 1		Level 2		Level 3		Total
	(in thousands)
Assets:
Money market funds	$	46,276	$	—	$	—	$	46,276
Total assets	$	46,276	$	—	$	—	$	46,276

Liabilities:
Derivative liability	$	—	$	—	$	85	$	85
Total liabilities	$	—	$	—	$	85	$	85

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

There were no changes in valuation techniques used during the three months ended March 31, 2026.

Derivative Liability

In May 2024, we entered into the K2HV Loan Agreement, as further described in Note 6, which provided up to $60.0 million principal in term loans. Pursuant to the terms of the K2HV Loan Agreement, the lenders thereto could 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 were required to be bifurcated as a single compound embedded derivative carried at fair value, with subsequent changes in fair value recognized in the condensed consolidated statements of operations.

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


	Three Months Ended March 31,
	2026		2025
	(in thousands)
Balance at beginning of period	$	759	$	2,829

Change in fair value	(674)		(171)
Balance at end of period	$	85	$	2,658

The change in fair value of the derivative liability is included in other income, net in the accompanying condensed consolidated statements of operations. We recognized gains of $0.7 million and $0.2 million related to change in fair value of the derivative liability during the three months ended March 31, 2026 and 2025, respectively.

The fair value of the derivative liability in the term loan was estimated using the Monte Carlo and the Black-Scholes models, each weighted based on the probable outcomes of various scenarios. 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:


	March 31, 2026	December 31, 2025
Stock Price	$0.83	$0.63
Volatility	99.7%	105.0%
Risk-free rate (continuous)	3.8%	3.5%
Expected term (in years)	2.09	0.25
Dividend yield (continuous)	—%	—%

On May 6, 2026, we repaid all amounts owed under the K2HV Loan Agreement, as described further in Note 12. No portion of the Fixed Price Conversion or the Variable Price Conversion had been exercised prior to the repayment of the term loans.

- 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

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-Section 50
-Paragraph 2
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Reference 2: http://www.xbrl.org/2003/role/exampleRef
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Reference 3: http://www.xbrl.org/2003/role/exampleRef
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+ Details

Financial Instruments and Fair Value Measurements - Schedule of Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation (Details) - Level 3 - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
beginning of period	$ 759	$ 2,829
Change in fair value	(674)	(171)
end of period	$ 85	$ 2,658

Stock-based Compensation - Narrative (Details) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended		12 Months Ended	59 Months Ended
	Apr. 30, 2021 shares	Mar. 31, 2026 USD ($) shares	Mar. 31, 2025 $ / shares shares	Dec. 31, 2021	Mar. 31, 2026 USD ($) shares
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Granted (in shares)		0
Weighted-average grant date fair value of awards (in usd per share) \| $ / shares			$ 1.22
Stock option exercises (in shares)		0	0
Share-based compensation expense not yet recognized \| $		$ 2.6			$ 2.6
2026 Restructuring Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
One-time charge related to modification \| $		$ 0.6
Shares reserved for issuance under the 2021 Stock Incentive Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock option expiration period upon termination		90 days
Share-based compensation not yet recognized, recognition period		1 year 10 months 24 days
Shares reserved for issuance under the 2021 Stock Incentive Plan \| 2026 Restructuring Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Stock option expiration period		10 years
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)	5.00%
2021 Stock Incentive Plan \| Common stock to be issued upon exercise of the K2HV Loan Agreement conversion feature
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Common stock authorized to be issued (in shares)	477,725
2021 Stock Employee Stock Purchase Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Offering period				6 months
Purchase period				6 months
ESPP purchase price, percent				0.85
Shares purchased by employees (in shares)		0	0
Common Stock
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Common stock authorized to be issued (in shares)	3,352,725
Common Stock \| 2021 Stock Incentive Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Common stock authorized to be issued (in shares)	2,843,116
Maximum number of shares to be added annually, as a percentage of outstanding shares (in shares)					9,582,699
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

Net Loss Attributable to Common Stockholders per Share - Narrative (Details) - shares	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	8,456,461	10,420,984
Common stock to be issued upon exercise of the K2HV Loan Agreement conversion feature
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)		791,364

Strategic Review and Liquidity (Details) - USD ($) $ in Thousands	1 Months Ended
	Feb. 28, 2026	Mar. 31, 2026	Dec. 31, 2025	Mar. 31, 2025
Restructuring and Related Activities [Abstract]
Reduction in workforce (percent)	64.00%
Cash and cash equivalents		$ 46,450	$ 57,050	$ 92,042

Common and Preferred Stock (Tables)

3 Months Ended

Mar. 31, 2026

Equity [Abstract]

Schedule of Common Stock Reserved for Issuance

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


	As of March 31, 2026	As of December 31, 2025
Shares reserved for exercises of outstanding stock options	8,440,233	9,954,872


Shares reserved for issuance under the 2021 Employee Stock Purchase Plan	1,046,897	560,929
Shares reserved for issuance under the 2021 Stock Incentive Plan	5,987,542	2,039,026
Shares reserved for issuance as part of the K2HV Loan Agreement conversion feature	791,364	791,364
Total shares reserved for future issuance	16,266,036	13,346,191

Common and Preferred Stock - Narrative (Details)	3 Months Ended
Common and Preferred Stock - Narrative (Details)	Mar. 31, 2026 USD ($) shares	Mar. 31, 2025 shares	Dec. 31, 2025 shares	May 08, 2025 USD ($)	Feb. 29, 2024 USD ($)	May 10, 2022 USD ($)
Class of Stock [Line Items]
Common stock authorized (in shares)	200,000,000		200,000,000
Dividends declared \| $	$ 0
Preferred stock authorized (in shares)	5,000,000		5,000,000
Preferred stock outstanding (in shares)	0		0
Preferred stock issued (in shares)	0		0
ATM Offering
Class of Stock [Line Items]
Sales commissions, percentage						0.030
Issuance of common stock from at the market offering, net of issuance costs (in shares)	0	0
ATM Offering \| Maximum
Class of Stock [Line Items]
Common stock, amount authorized \| $					$ 75,000,000.0	$ 50,000,000.0
ATM Offering - Baby Shelf Limitation \| Maximum
Class of Stock [Line Items]
Common stock, amount authorized \| $				$ 12,500,000

Restructuring - Schedule of Restructuring Costs Incurred (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Feb. 28, 2026
Restructuring Cost and Reserve [Line Items]
Total restructuring costs	$ 4,305	$ 0
Total Estimated Costs	6,387		$ 6,400
Employee severance, benefits and related taxes
Restructuring Cost and Reserve [Line Items]
Total restructuring costs	2,557
Total Estimated Costs	2,557
Employee retention bonuses, benefits and related taxes
Restructuring Cost and Reserve [Line Items]
Total restructuring costs	783
Total Estimated Costs	2,865
Stock-based compensation
Restructuring Cost and Reserve [Line Items]
Total restructuring costs	615
Total Estimated Costs	615
Contract termination costs
Restructuring Cost and Reserve [Line Items]
Total restructuring costs	350
Total Estimated Costs	$ 350

- 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

Restructuring

3 Months Ended

Mar. 31, 2026

Restructuring and Related Activities [Abstract]

Restructuring

2. Strategic Review and Liquidity

11. Restructuring

In February 2026, we initiated a strategic review process and the 2026 Restructuring. The 2026 Restructuring is expected to be completed by the end of 2026.

The following table summarizes the restructuring costs incurred and the total estimated costs expected to be incurred in connection with the 2026 Restructuring:


	Three Months Ended March 31, 2026		Cumulative Costs to Date		Total Estimated Costs
	(in thousands)
Employee severance, benefits and related taxes	$	2,557	$	2,557	$	2,557
Employee retention bonuses, benefits and related taxes	783		783		2,865
Stock-based compensation	615		615		615
Contract termination costs	350		350		350
Total restructuring costs	$	4,305	$	4,305	$	6,387

Total restructuring costs recognized in our condensed consolidated statements of operations were as follows:


	Three Months Ended March 31,
	2026		2025
	(in thousands)
Research and development	$	3,058	$	—
General and administrative	1,247		—
Total restructuring costs	$	4,305	$	—

Accrued restructuring costs, which are included in accrued expenses and other current liabilities on our condensed consolidated balance sheets, were as follows:


	Three Months Ended March 31,
	2026		2025
	(in thousands)
Balance at beginning of period	$	—	$	—
Restructuring costs recognized during the period	4,305		—
Cash payments made during the period	(3,971)		—
Employee retention bonuses paid in advance	724		—
Non-cash charges recognized during the period	(615)		—
Balance at end of period	$	443	$	—

Stock-based Compensation - Schedule of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Number of Options
Outstanding at beginning of period (in shares)	9,954,872
Granted (in shares)	0
Exercised (in shares)	0	0
Cancelled (in shares)	(1,514,639)
Outstanding at end of period (in shares)	8,440,233
Exercisable at end of period (in shares)	6,600,515
Weighted-Average Exercise Price per Share
Outstanding at beginning of period (in usd per share)	$ 4.71
Granted (in usd per share)	0
Exercised (in usd per share)	0
Cancelled (in usd per share)	2.38
Outstanding at end of period (in usd per share)	5.13
Exercisable at end of period (in usd per share)	$ 5.97
Weighted-Average Remaining Contractual Life (in years)
Outstanding	6 years 7 months 28 days
Exercisable	6 years 1 month 24 days
Outstanding, Aggregate Intrinsic Value	$ 0.0
Exercisable, Aggregate Intrinsic Value	$ 0.0

Restructuring - Schedule of Accrued Restructuring Costs (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Restructuring Reserve [Roll Forward]
Balance at beginning of period	$ 0	$ 0
Restructuring costs recognized during the period	4,305	0
Cash payments made during the period	(3,971)	0
Employee retention bonuses paid in advance	724	0
Non-cash charges recognized during the period	(615)	0
Balance at end of period	$ 443	$ 0

Segment Information

3 Months Ended

Mar. 31, 2026

Segment Reporting [Abstract]

Segment Information

10. Segment Information

We have one reportable segment which focuses on the discovery and development of cancer therapeutics. Our chief operating decision maker (“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 condensed consolidated balance sheets.

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


	Three Months Ended March 31,
	2026		2025
	(in thousands)


General and administrative support	$	4,572	$	3,823
Clinical development	3,643		4,329
Research and discovery	2,155		3,319
Manufacturing	1,574		4,088
Other segment expenses(a)	1,327		2,432

Interest income	433		997
Interest expense	(1,368)		(1,263)

Other income, net	674		168
Segment and consolidated net loss	$	(13,532)	$	(18,089)

(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.

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+ Details

Cover - shares	3 Months Ended
Cover - shares	Mar. 31, 2026	May 01, 2026
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2026
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 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
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		48,596,817
Entity Central Index Key	0001785530
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2026
Document Fiscal Period Focus	Q1
Amendment Flag	false

Restructuring - Narrative (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Feb. 28, 2026
Restructuring and Related Activities [Abstract]
Total Estimated Costs	$ 6,387	$ 6,400

Insider Trading Arrangements	3 Months Ended
Insider Trading Arrangements	Mar. 31, 2026
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

Restructuring - Schedule of Restructuring Costs Recognized (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Restructuring Cost and Reserve [Line Items]
Total restructuring costs	$ 4,305	$ 0
Research and development
Restructuring Cost and Reserve [Line Items]
Total restructuring costs	3,058	0
General and administrative
Restructuring Cost and Reserve [Line Items]
Total restructuring costs	$ 1,247	$ 0

- 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

Term Loan (Tables)

3 Months Ended

Mar. 31, 2026

Debt Disclosure [Abstract]

Schedule of Outstanding Term Loans Payable

The outstanding term loans payable consists of the following:


	March 31, 2026		December 31, 2025
	(in thousands)
Note payable	$	30,000	$	30,000
Unamortized debt discount and issuance costs	(1,169)		(1,764)
Net carrying amount of note payable	$	28,831	$	28,236

Schedule of Interest Expense

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


	Three Months Ended March 31,
	2026		2025
	(in thousands)
Interest expense based on coupon interest rate (10.3%) of outstanding term loans	$	773	$	773
Amortization of debt discount and accretion of Final Fee (8.94%)	595		490
Total interest expense on effective rate (19.24%)	$	1,368	$	1,263

Schedule of Total Principal Payments Maturities

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


	Principal Payments and Final Fee
	(in thousands)
2026 (remaining as of March 31, 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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+ Details

Stock-based Compensation - Schedule of Expense Recognized (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	$ 929	$ 2,006
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	503	1,055
General and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	$ 426	$ 951

Net Loss Attributable to Common Stockholders per Share - Schedule of Antidilutive Shares (Details) - shares	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	8,456,461	10,420,984
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)	8,440,233	10,282,640
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	46,487
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)	16,228	91,857

Summary of Significant Accounting Policies (Policies)	3 Months Ended
Summary of Significant Accounting Policies (Policies)	Mar. 31, 2026
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation and Consolidation The accompanying condensed consolidated financial statements as of March 31, 2026 and December 31, 2025, and for the three months ended March 31, 2026 and 2025, 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”) for condensed consolidated financial information. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, these condensed consolidated financial statements reflect all normal recurring adjustments which are necessary for a fair presentation of our financial position and results of our operations, as of and for the periods presented. These condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes thereto contained in our Annual Report on Form 10-K for the year ended December 31, 2025 filed with the SEC on March 27, 2026 (the “2025 Annual Report”).
Consolidation	The accompanying condensed 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.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Significant estimates and assumptions reflected in these condensed 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.
Recent Accounting Pronouncements	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. We are currently evaluating the impact that this standard will have on our consolidated financial statements. Other accounting standards that have been issued or proposed by the FASB or other standards-setting bodies that do not require adoption until a future date are not expected to have a material impact on our consolidated financial statements upon adoption.
Subsequent Events	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 Note 12, we did not identify any subsequent events that require adjustment or disclosure in the condensed consolidated financial statements.

- Definition

Disclosure of accounting policy for the use of estimates in the preparation of financial statements in conformity with generally accepted accounting principles.

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+ Details

Financial Instruments and Fair Value Measurements - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended
	May 31, 2024	Mar. 31, 2026	Mar. 31, 2025
Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Gains recognized related to the change in fair value of the derivative liability		$ 674	$ 171
Common stock to be issued upon exercise of the K2HV Loan Agreement conversion feature
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loan agreement, amount	$ 60,000
Conversion of outstanding principal	$ 5,000
Conversion price (in usd per share)	$ 6.3182
Common stock to be issued upon exercise of the K2HV Loan Agreement conversion feature \| Minimum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Adjustment rate (percent)	9.99%
Common stock to be issued upon exercise of the K2HV Loan Agreement conversion feature \| Maximum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Adjustment rate (percent)	19.99%

Term Loan

3 Months Ended

Mar. 31, 2026

Debt Disclosure [Abstract]

Term Loan

6. Term Loan

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 (in such capacity, together with its successors, the “Administrative Agent”); and Ankura Trust Company, LLC, as collateral trustee for the Lenders (the “Collateral Trustee”). The K2HV Loan Agreement provided 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 was available to be drawn 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. Our ability to draw upon the fourth tranche commitment expired on May 1, 2026 without being drawn upon.

The term loan was scheduled to mature on May 1, 2028, and we were 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 bore 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 could 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 were entitled and certain notice requirements. We were 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 was being accreted to interest expense using the effective interest method over the life of the debt.

The Lenders had the option, 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 would have been 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 were required to be bifurcated as an embedded derivative under ASC Topic 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 condensed consolidated statements of operations. See Note 4 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 contained customary representations and warranties, events of default and affirmative and negative covenants, including covenants that limited or restricted 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 have been applied to the outstanding loan balances, and the Lenders may have declared all outstanding obligations immediately due and payable and exercised all of their rights and remedies as set forth in the K2HV Loan Agreement and under applicable law. As of March 31, 2026, we were 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 was being amortized to interest expense over the term of the K2HV Loan Agreement using the effective interest method. As of March 31, 2026, the fair value of the term loan was estimated to be approximately $29.7 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:


	March 31, 2026		December 31, 2025
	(in thousands)
Note payable	$	30,000	$	30,000
Unamortized debt discount and issuance costs	(1,169)		(1,764)
Net carrying amount of note payable	$	28,831	$	28,236

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


	Three Months Ended March 31,
	2026		2025
	(in thousands)
Interest expense based on coupon interest rate (10.3%) of outstanding term loans	$	773	$	773
Amortization of debt discount and accretion of Final Fee (8.94%)	595		490
Total interest expense on effective rate (19.24%)	$	1,368	$	1,263

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


	Principal Payments and Final Fee
	(in thousands)
2026 (remaining as of March 31, 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 March 31, 2026 and December 31, 2025 given the potential that the loan may be repaid in the subsequent twelve months of each period. On May 6, 2026, we entered into a letter agreement discussed in more detail in Note 12, that resulted in the satisfaction of all obligations under the K2HV Loan Agreement.

- 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
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-Name Accounting Standards Codification
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-Paragraph 1
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(c))
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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Reference 10: http://www.xbrl.org/2003/role/disclosureRef
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Reference 11: http://www.xbrl.org/2003/role/disclosureRef
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Reference 12: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 470
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-URI https://asc.fasb.org/470/tableOfContent

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
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-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482925/835-30-45-2

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
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Reference 15: http://www.xbrl.org/2003/role/disclosureRef
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Reference 16: http://www.xbrl.org/2003/role/disclosureRef
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Reference 17: http://www.xbrl.org/2003/role/disclosureRef
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Reference 18: http://www.xbrl.org/2003/role/disclosureRef
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Reference 19: http://www.xbrl.org/2003/role/disclosureRef
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Reference 20: http://www.xbrl.org/2003/role/disclosureRef
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Reference 21: http://www.xbrl.org/2003/role/disclosureRef
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Reference 22: http://www.xbrl.org/2003/role/disclosureRef
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Reference 23: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Subsequent Events (Details) - Subsequent Event $ in Millions	May 06, 2026 USD ($)	May 07, 2026 USD ($) ft²
Subsequent Event [Line Items]
Upfront consideration	$ 21.0
Additional amount receivable	$ 2.0
Non-compete covenant period	18 months
Area of building space \| ft²		25,778
Lease termination fee payable		$ 2.7
Loan Agreement
Subsequent Event [Line Items]
Repayment of loan agreement	$ 31.4

Condensed Consolidated Balance Sheets (unaudited) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025
Current assets:
Cash and cash equivalents	$ 46,450	$ 57,050
Prepaid expenses and other current assets	2,284	1,536
Total current assets	48,734	58,586
Property and equipment, net	4,290	4,688
Restricted cash and cash equivalents, net of current portion	0	901
Operating lease right of use asset	4,998	5,216
Other assets	0	5
Total assets	58,022	69,396
Current liabilities:
Accounts payable	3,569	754
Accrued expenses and other current liabilities	4,515	5,407
Operating lease liability, current	1,604	1,751
Note payable, net of discount and issuance costs	28,831	28,236
Total current liabilities	38,519	36,148
Operating lease liability, net of current portion	7,216	7,684
Derivative liability	85	759
Total liabilities	45,820	44,591
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $0.0001 par value, 5,000,000 shares authorized as of March 31, 2026 and December 31, 2025; no shares issued or outstanding as of March 31, 2026 and December 31, 2025	0	0
Common stock, $0.0001 par value, 200,000,000 shares authorized as of March 31, 2026 and December 31, 2025; 48,596,817 shares issued and outstanding as of March 31, 2026 and December 31, 2025	5	5
Additional paid-in capital	501,139	500,210
Accumulated deficit	(488,942)	(475,410)
Total stockholders’ equity	12,202	24,805
Total liabilities and stockholders’ equity	$ 58,022	$ 69,396

Condensed Consolidated Statements of Operations (unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Operating expenses:
Research and development	$ 8,181	$ 13,120
General and administrative	5,090	4,871
Total operating expenses	13,271	17,991
Operating loss	(13,271)	(17,991)
Other expense:
Interest income	433	997
Interest expense	(1,368)	(1,263)
Other income, net	674	168
Total other expense	(261)	(98)
Net loss	$ (13,532)	$ (18,089)
Net loss per common share, basic (in usd per share)	$ (0.28)	$ (0.40)
Net loss per common share, diluted (in usd per share)	$ (0.28)	$ (0.40)
Weighted-average common shares outstanding, basic (in shares)	48,596,817	44,827,159
Weighted-average common shares outstanding, diluted (in shares)	49,388,181	44,827,159

Net Loss Attributable to Common Stockholders per Share

3 Months Ended

Mar. 31, 2026

Earnings Per Share [Abstract]

Net Loss Attributable to Common Stockholders per Share

9. 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, and warrants to purchase common stock are considered to be potentially dilutive securities; however, the following amounts were excluded from the weighted-average common stock outstanding in the calculation of diluted net loss attributable to common stockholders per share because their effect would be anti-dilutive:


	March 31,
	2026	2025
Outstanding stock options	8,440,233	10,282,640

Warrants to purchase common stock	—	46,487
Common stock to be issued under the 2021 ESPP	16,228	91,857

Total	8,456,461	10,420,984

As described below, the conversion option derivative under the K2HV Loan Agreement was determined to be dilutive for the three months ended March 31, 2026. For the three months ended March 31, 2025, the effect of the conversion option derivative would have been anti-dilutive. Accordingly, for the three months ended March 31, 2025, we have excluded 791,364 shares of common stock equivalents that are available to be issued in conjunction with the conversion option derivative from the calculation of diluted net loss attributable to common stockholders per share.

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 three months ended March 31, 2026. Pursuant to 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 the period in net loss due to the change in fair value of the conversion option derivative liability under the K2HV Loan Agreement and the interest expense recognized during the 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.


	Three Months Ended March 31,
	2026		2025
	(in thousands)
Numerator
Net loss	$	(13,532)	$	(18,089)
Less: change in fair value of derivative liability	(674)		—
Plus: interest expense on converted term loan	199		—
Adjusted net loss	$	(14,007)	$	(18,089)
Denominator
Weighted-average common stock outstanding, basic	48,596,817		44,827,159
Dilutive effect of common stock issuable from assumed conversion of convertible term loan	791,364		—
Weighted-average common stock outstanding, diluted	49,388,181		44,827,159
Net loss per share
Basic	$	(0.28)	$	(0.40)
Diluted	$	(0.28)	$	(0.40)

Common and Preferred Stock

3 Months Ended

Mar. 31, 2026

Equity [Abstract]

Common and Preferred Stock

7. 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 March 31, 2026, 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 March 31, 2026, we remain subject to the Baby Shelf Limitation. During the three months ended March 31, 2026 and 2025, we did not sell any shares of our common stock under the ATM Offering.

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


	As of March 31, 2026	As of December 31, 2025
Shares reserved for exercises of outstanding stock options	8,440,233	9,954,872


Shares reserved for issuance under the 2021 Employee Stock Purchase Plan	1,046,897	560,929
Shares reserved for issuance under the 2021 Stock Incentive Plan	5,987,542	2,039,026
Shares reserved for issuance as part of the K2HV Loan Agreement conversion feature	791,364	791,364
Total shares reserved for future issuance	16,266,036	13,346,191

Preferred Stock

We are authorized to issue 5,000,000 shares of undesignated preferred stock in one or more series. As of March 31, 2026, no shares of preferred stock were issued or outstanding.

- Definition

The entire disclosure for equity.

+ References

+ Details

Accrued Expenses and Other Current Liabilities (Tables)

3 Months Ended

Mar. 31, 2026

Payables and Accruals [Abstract]

Schedule of Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities were comprised as follows:


	March 31, 2026		December 31, 2025
	(in thousands)
Professional fees	$	1,719	$	1,388
Contract research	1,633		2,376
Restructuring costs	443		—
Accrued interest	266		266
Employee compensation and benefits	190		302
Manufacturing	50		928
Other	214		147
Total accrued expenses and other current liabilities	$	4,515	$	5,407

Term Loan - Schedule of Total Principle Payments Maturities (Details) $ in Thousands	Mar. 31, 2026 USD ($)
Principal Payments and Final Fee
2026 (remaining as of March 31, 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

Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025
Payables and Accruals [Abstract]
Professional fees	$ 1,719	$ 1,388
Contract research	1,633	2,376
Restructuring costs	443	0
Accrued interest	266	266
Employee compensation and benefits	190	302
Manufacturing	50	928
Other	214	147
Total accrued expenses and other current liabilities	$ 4,515	$ 5,407

Accrued Expenses and Other Current Liabilities

3 Months Ended

Mar. 31, 2026

Payables and Accruals [Abstract]

Accrued Expenses and Other Current Liabilities

5. Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities were comprised as follows:


	March 31, 2026		December 31, 2025
	(in thousands)
Professional fees	$	1,719	$	1,388
Contract research	1,633		2,376
Restructuring costs	443		—
Accrued interest	266		266
Employee compensation and benefits	190		302
Manufacturing	50		928
Other	214		147
Total accrued expenses and other current liabilities	$	4,515	$	5,407

Nature of Business	3 Months Ended
Nature of Business	Mar. 31, 2026
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 unaudited, condensed consolidated financial statements, the terms “Werewolf,” the “Company,” “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.

Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Operating activities:
Net loss	$ (13,532)	$ (18,089)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	929	2,006
Depreciation expense	398	426
Non-cash interest expense	595	490
Non-cash lease expense	218	188
Change in fair value of derivative liability	(674)	(171)
Changes in operating assets and liabilities:
Prepaid expenses and other assets	161	131
Accounts payable, accrued expenses and other liabilities	1,923	(3,366)
Operating lease liability	(615)	(563)
Net cash used in operating activities	(10,597)	(18,948)
Net decrease in cash, cash equivalents and restricted cash and cash equivalents	(10,597)	(18,948)
Cash, cash equivalents and restricted cash and cash equivalents—beginning of period	57,951	112,215
Cash, cash equivalents and restricted cash and cash equivalents—end of period	47,354	93,267
Reconciliation of cash, cash equivalents and restricted cash and cash equivalents to the condensed consolidated balance sheets
Cash and cash equivalents	46,450	92,042
Prepaid expenses and other current assets	904	334
Restricted cash and cash equivalents, net of current portion	0	891
Total cash, cash equivalents and restricted cash and cash equivalents	47,354	93,267
Supplemental disclosure of cash flow information:
Cash paid for interest	773	773
Supplemental disclosure of non-cash investing and financing activities:
Issuance costs in accounts payable and accrued expenses	$ 75	$ 0

Condensed Consolidated Balance Sheets (unaudited) (Parenthetical) - $ / shares	Mar. 31, 2026	Dec. 31, 2025
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	48,596,817
Common stock outstanding (in shares)	48,596,817	48,596,817

Restructuring (Tables)

3 Months Ended

Mar. 31, 2026

Restructuring and Related Activities [Abstract]

Schedule of Restructuring and Related Costs

The following table summarizes the restructuring costs incurred and the total estimated costs expected to be incurred in connection with the 2026 Restructuring:


	Three Months Ended March 31, 2026		Cumulative Costs to Date		Total Estimated Costs
	(in thousands)
Employee severance, benefits and related taxes	$	2,557	$	2,557	$	2,557
Employee retention bonuses, benefits and related taxes	783		783		2,865
Stock-based compensation	615		615		615
Contract termination costs	350		350		350
Total restructuring costs	$	4,305	$	4,305	$	6,387

Total restructuring costs recognized in our condensed consolidated statements of operations were as follows:


	Three Months Ended March 31,
	2026		2025
	(in thousands)
Research and development	$	3,058	$	—
General and administrative	1,247		—
Total restructuring costs	$	4,305	$	—

Accrued restructuring costs, which are included in accrued expenses and other current liabilities on our condensed consolidated balance sheets, were as follows:


	Three Months Ended March 31,
	2026		2025
	(in thousands)
Balance at beginning of period	$	—	$	—
Restructuring costs recognized during the period	4,305		—
Cash payments made during the period	(3,971)		—
Employee retention bonuses paid in advance	724		—
Non-cash charges recognized during the period	(615)		—
Balance at end of period	$	443	$	—

Net Loss Attributable to Common Stockholders per Share (Tables)

3 Months Ended

Mar. 31, 2026

Earnings Per Share [Abstract]

Schedule of Antidilutive Securities Excluded from Computation of Loss per Share


	March 31,
	2026	2025
Outstanding stock options	8,440,233	10,282,640

Warrants to purchase common stock	—	46,487
Common stock to be issued under the 2021 ESPP	16,228	91,857

Total	8,456,461	10,420,984

Schedule of Earnings Per Share, Basic and Diluted


	Three Months Ended March 31,
	2026		2025
	(in thousands)
Numerator
Net loss	$	(13,532)	$	(18,089)
Less: change in fair value of derivative liability	(674)		—
Plus: interest expense on converted term loan	199		—
Adjusted net loss	$	(14,007)	$	(18,089)
Denominator
Weighted-average common stock outstanding, basic	48,596,817		44,827,159
Dilutive effect of common stock issuable from assumed conversion of convertible term loan	791,364		—
Weighted-average common stock outstanding, diluted	49,388,181		44,827,159
Net loss per share
Basic	$	(0.28)	$	(0.40)
Diluted	$	(0.28)	$	(0.40)

Subsequent Events	3 Months Ended
Subsequent Events	Mar. 31, 2026
Subsequent Events [Abstract]
Subsequent Events	12. Subsequent Events Asset Purchase Agreement; Termination of Collaboration Agreement On May 6, 2026 (the “Closing”), we entered into an asset purchase agreement (the “Purchase Agreement”) with Jazz Pharmaceuticals Ireland Limited, a corporation organized under the laws of Ireland (“Jazz”). In April 2022, we entered into a global collaboration and license agreement (the “Collaboration Agreement”) with Jazz under which Jazz acquired exclusive global development and commercialization rights to JZP898, as well as products containing certain isolated recombinant polypeptides comprising IFNα that meet specified criteria (each such product, a Licensed Product). Subject to the terms and conditions of the Purchase Agreement, we sold to Jazz (the “Asset Sale”) its program (the “898 Program”) for the development, manufacturing, commercialization, use and other exploitation of the Licensed Product. Pursuant to the Purchase Agreement and related ancillary agreements, in consideration for the Transferred Assets, Jazz paid to us upfront consideration of $21.0 million, and has agreed to pay an additional $2.0 million upon the consent to the partial assignment a certain license agreement, as and to the extent such agreement relates to the conduct of the 898 Program. Jazz also assumed certain liabilities of ours relating to the 898 Program arising after the Closing. The Purchase Agreement contains customary representations, warranties and covenants of each of us and Jazz. The Purchase Agreement further provides that, subject to certain limitations, we and Jazz will each indemnify the other for certain losses arising from such breaches of representations, warranties and covenants and liabilities allocated to such party pursuant to the terms of the Purchase Agreement. In addition, the Purchase Agreement contains a non-competition covenant pursuant to which we agreed not to exploit any IFNα or variant thereof, or any product containing any IFNα or variant thereof, for a period of eighteen (18) months after the Closing, subject to customary exceptions for change of control transactions. Effective as of the Closing, the Collaboration Agreement was terminated. Loan Repayment On May 6, 2026, we entered into a letter agreement providing for the repayment by us of all amounts owed under the K2HV Loan Agreement. On May 6, 2026, upon payment by us of approximately $31.4 million, all of our indebtedness and obligations to the Collateral Trustee and the Lenders under the K2HV Loan Agreement and any other related loan and collateral security documents was deemed paid and discharged in full. Lease Termination On May 7, 2026, we entered into an Agreement for Termination of Lease and Voluntary Surrender of Premises (the “Lease Termination”) with ARE-770/784/790 Memorial Drive, LLC (the “Landlord”), pursuant to which we and the Landlord agreed to terminate that certain lease, dated June 1, 2021, as amended, by and between us and the Landlord (the “Lease”), effective October 31, 2026 or such sooner date as a party provides notices in accordance with the Lease Termination (the “Lease Termination Date”). Under the Lease, we leased approximately 25,778 square feet of space, consisting of the entire building located at 200 Talcott Avenue, Watertown, Massachusetts. Pursuant to the Lease Termination, we will pay the Landlord an aggregate termination fee of $2.7 million, which shall represent full satisfaction of all remaining payments and other financial obligations due from us to the Landlord under the Lease including, without limitation, Base Rent (as defined in the Lease) for the months of May 2026 through October 2026. We will have no further rent obligations to the Landlord pursuant to the Lease after the Lease Termination Date.

Segment Information (Tables)

3 Months Ended

Mar. 31, 2026

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:


	Three Months Ended March 31,
	2026		2025
	(in thousands)


General and administrative support	$	4,572	$	3,823
Clinical development	3,643		4,329
Research and discovery	2,155		3,319
Manufacturing	1,574		4,088
Other segment expenses(a)	1,327		2,432

Interest income	433		997
Interest expense	(1,368)		(1,263)

Other income, net	674		168
Segment and consolidated net loss	$	(13,532)	$	(18,089)

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

Condensed Consolidated Statements of Stockholders’ Equity (unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit
Stockholders' equity, beginning balance (in shares) at Dec. 31, 2024		44,827,159
Stockholders' equity, beginning balance at Dec. 31, 2024	$ 73,390	$ 5	$ 487,973	$ (414,588)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	2,006		2,006
Net loss	(18,089)			(18,089)
Stockholders' equity, ending balance (in shares) at Mar. 31, 2025		44,827,159
Stockholders' equity, ending balance at Mar. 31, 2025	$ 57,307	$ 5	489,979	(432,677)
Stockholders' equity, beginning balance (in shares) at Dec. 31, 2025	48,596,817	48,596,817
Stockholders' equity, beginning balance at Dec. 31, 2025	$ 24,805	$ 5	500,210	(475,410)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	929		929
Net loss	$ (13,532)			(13,532)
Stockholders' equity, ending balance (in shares) at Mar. 31, 2026	48,596,817	48,596,817
Stockholders' equity, ending balance at Mar. 31, 2026	$ 12,202	$ 5	$ 501,139	$ (488,942)

- Definition

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

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-Subparagraph (SX 210.4-08(g)(1)(ii))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 15: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 323
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481687/323-10-50-3

Reference 16: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 4.E)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480418/310-10-S99-2

+ Details

Financial Instruments and Fair Value Measurements - Schedule of Unobservable Inputs (Details)	Mar. 31, 2026 $ / shares year	Dec. 31, 2025 $ / shares year
Stock price (in usd per share)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input \| $ / shares	0.83	0.63
Volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.997	1.050
Risk-free rate (continuous)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.038	0.035
Expected term (in years)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input \| year	2.09	0.25
Dividend yield (continuous)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0	0

Financial Instruments and Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2026

Fair Value Disclosures [Abstract]

Schedule of Assets Measured at Fair Value on a Recurring Basis

Assets and liabilities measured at fair value on a recurring basis as of March 31, 2026 were as follows:


	Level 1		Level 2		Level 3		Total
	(in thousands)
Assets:
Money market funds	$	46,276	$	—	$	—	$	46,276
Total assets	$	46,276	$	—	$	—	$	46,276

Liabilities:
Derivative liability	$	—	$	—	$	85	$	85
Total liabilities	$	—	$	—	$	85	$	85

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

Schedule of Weighted-Average Significant Unobservable Inputs

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


	Three Months Ended March 31,
	2026		2025
	(in thousands)
Balance at beginning of period	$	759	$	2,829

Change in fair value	(674)		(171)
Balance at end of period	$	85	$	2,658


	March 31, 2026	December 31, 2025
Stock Price	$0.83	$0.63
Volatility	99.7%	105.0%
Risk-free rate (continuous)	3.8%	3.5%
Expected term (in years)	2.09	0.25
Dividend yield (continuous)	—%	—%