0001785530-26-000019 | 10-Q | XBRL Viewer | Werewolf Therapeutics INC

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Net Income (Loss) Attributable to Common Stockholders per Share - Schedule of Antidilutive Shares (Details) - shares	6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	8,206,431	11,323,668
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)	8,206,431	10,461,702
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)	0	70,602
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)	0	791,364

Strategic Review and Liquidity

6 Months Ended

Jun. 30, 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 4, 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 in February 2026, representing 64% of our workforce to better align our resources with our pursuit of strategic alternatives. In May 2026, an additional reduction in force occurred, representing 36% of our workforce at that time. See Note 12 for further discussion of the impact of the 2026 Restructuring.

We had cash and cash equivalents of $22.0 million at June 30, 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.

12. 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 $6.5 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 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 June 30, 2026		Six Months Ended June 30, 2026		Cumulative Costs to Date		Total Estimated Costs
	(in thousands)
Employee severance, benefits and related taxes	$	83	$	2,640	$	2,640	$	2,640
Employee retention bonuses, benefits and related taxes	1,296		2,079		2,079		2,881
Stock-based compensation	50		665		665		665
Contract termination costs	(50)		300		300		300
Total restructuring costs	$	1,379	$	5,684	$	5,684	$	6,486

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


	Three Months Ended June 30,				Six Months Ended June 30,
	2026		2025		2026		2025
	(in thousands)
Research and development	$	419	$	—	$	3,477	$	—
General and administrative	960		—		2,207		—
Total restructuring costs	$	1,379	$	—	$	5,684	$	—

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





Balance as of December 31, 2025	$	—
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 as of March 31, 2026	443
Restructuring costs recognized during the period	1,379
Cash payments made during the period	(1,229)
Amortization of employee retention bonuses paid in the prior period	(509)
Non-cash charges recognized during the period	(50)
Balance as of June 30, 2026	$	34

Nature of Business	6 Months Ended
Nature of Business	Jun. 30, 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.

Segment Information (Details) $ in Thousands	3 Months Ended				6 Months Ended
Segment Information (Details) $ in Thousands	Jun. 30, 2026 USD ($)	Mar. 31, 2026 USD ($)	Jun. 30, 2025 USD ($)	Mar. 31, 2025 USD ($)	Jun. 30, 2026 USD ($) segment	Jun. 30, 2025 USD ($)
Segment Reporting [Abstract]
Number of reportable segments \| segment					1
Segment Reporting [Line Items]
Interest income	$ 277		$ 850		$ 710	$ 1,847
Interest expense	(475)		(1,301)		(1,843)	(2,564)
Loss on extinguishment of note payable	(3,354)		0		(3,354)	0
Other income, net	64		11		738	179
Net income (loss)	3,670	$ (13,532)	(17,982)	$ (18,089)	(9,862)	(36,071)
Reportable Segment
Segment Reporting [Line Items]
Collaboration revenue	21,000		0		21,000	0
General and administrative support	6,678		3,486		11,250	7,309
Clinical development	3,047		5,710		6,690	10,039
Research and discovery	1,028		3,537		3,183	6,856
Manufacturing	218		2,610		1,792	6,698
Other segment expenses	2,871		2,199		4,198	4,631
Interest income	277		850		710	1,847
Interest expense	(475)		(1,301)		(1,843)	(2,564)
Loss on extinguishment of note payable	(3,354)		0		(3,354)	0
Other income, net	64		11		738	179
Net income (loss)	$ 3,670		$ (17,982)		$ (9,862)	$ (36,071)

Term Loan

6 Months Ended

Jun. 30, 2026

Debt Disclosure [Abstract]

Term Loan

7. 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 equal interest and 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 (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 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 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.

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.

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 $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. During the three and six months ended June 30, 2026, we recognized a loss on the extinguishment of debt in the amount of $3.4 million, primarily due to the write off of unamortized debt issuance costs and the unaccreted balance of the Final Fee.

The outstanding note payable consisted of the following as of December 31, 2025 (in thousands) :




Note payable	$	30,000
Unamortized debt discount and issuance costs	(1,764)
Net carrying amount of note payable	$	28,236

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


	Three Months Ended June 30,				Six Months Ended June 30,
	2026		2025		2026		2025
	(in thousands)
Interest expense based on coupon interest rate (10.3%) of outstanding term loans	$	299	$	781	$	1,072	$	1,554
Amortization of debt discount and accretion of Final Fee (8.94%)	176		520		771		1,010
Total interest expense on effective rate (19.24%)	$	475	$	1,301	$	1,843	$	2,564

We had presented the full amount of the term loan payable, net of discount and issuance costs, as a current liability as of December 31, 2025 based on our assessment that repayment of the loan was probable in the subsequent twelve months of December 31, 2025.

Stock-based Compensation - Narrative (Details) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended	62 Months Ended
	Apr. 30, 2021 shares	Jun. 30, 2026 USD ($) shares	Jun. 30, 2025 $ / shares shares	Jun. 30, 2026 USD ($) shares	Jun. 30, 2025 $ / shares shares	Dec. 31, 2021	Jun. 30, 2026 USD ($) shares
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Granted (in shares)		0		0
Weighted-average grant date fair value of awards (in usd per share) \| $ / shares			$ 0.82		$ 1.17
Stock option exercises (in shares)		0	0	0	0
Share-based compensation expense not yet recognized \| $		$ 2.0		$ 2.0			$ 2.0
2026 Restructuring Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
One-time charge related to modification \| $		$ 0.1		$ 0.7
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 8 months 12 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
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
Common Stock \| 2021 Stock Employee Stock Purchase Plan
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Shares purchased by employees (in shares)				2,249	39,853

Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2026	Dec. 31, 2025
Payables and Accruals [Abstract]
Contract research	$ 3,189	$ 2,376
Professional fees	2,316	1,388
Employee compensation and benefits	211	302
Manufacturing	90	928
Restructuring costs	34	0
Accrued interest	0	266
Other	84	147
Total accrued expenses and other current liabilities	$ 5,924	$ 5,407

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

Summary of Significant Accounting Policies	6 Months Ended
Summary of Significant Accounting Policies	Jun. 30, 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 June 30, 2026 and December 31, 2025, and for the three and six months ended June 30, 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 June 30, 2026, and for the three and six months ended June 30, 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 and six months ended June 30, 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 six months ended June 30, 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 13, we did not identify any subsequent events that require adjustment or disclosure in the condensed consolidated financial statements.

Collaboration Revenue (Details) - USD ($) $ in Thousands		1 Months Ended	3 Months Ended		6 Months Ended
Collaboration Revenue (Details) - USD ($) $ in Thousands	May 06, 2026	Jun. 30, 2024	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration revenue			$ 21,000	$ 0	$ 21,000	$ 0
Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Development and regulatory milestone payments		$ 515,000
Sales-based milestone payments		$ 740,000	$ 21,000		$ 21,000
Collaboration revenue	$ 21,000
Contingent consideration	$ 2,000
Non-compete covenant period	18 months
Expected contingent payment	$ 0

Common and Preferred Stock - Narrative (Details)	6 Months Ended
Common and Preferred Stock - Narrative (Details)	Jun. 30, 2026 USD ($) shares	Jun. 30, 2025 USD ($) $ / shares 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) \| shares	200,000,000		200,000,000
Dividends declared \| $	$ 0
Proceeds from at the market offering of common stock, net of issuance costs \| $	$ 0	$ 347,000
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 at the market offering, net of issuance costs (in shares) \| shares	0	421,766
Price per share (in usd per share) \| $ / shares		$ 1.33
Proceeds from at the market offering of common stock, net of issuance costs \| $		$ 300,000
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

Term Loan - Schedule of Outstanding Term Loans Payable (Details) - Term Loans - Term loan $ in Thousands	Dec. 31, 2025 USD ($)
Debt Instrument [Line Items]
Note payable	$ 30,000
Unamortized debt discount and issuance costs	(1,764)
Net carrying amount of note payable	$ 28,236

Restructuring - Schedule of Restructuring Costs Incurred (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2026	Mar. 31, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025	Feb. 28, 2026
Restructuring Cost and Reserve [Line Items]
Total restructuring costs	$ 1,379	$ 4,305	$ 0	$ 5,684	$ 0
Total Estimated Costs	6,486			6,486		$ 6,500
Employee severance, benefits and related taxes
Restructuring Cost and Reserve [Line Items]
Total restructuring costs	83			2,640
Total Estimated Costs	2,640			2,640
Employee retention bonuses, benefits and related taxes
Restructuring Cost and Reserve [Line Items]
Total restructuring costs	1,296			2,079
Total Estimated Costs	2,881			2,881
Stock-based compensation
Restructuring Cost and Reserve [Line Items]
Total restructuring costs	50			665
Total Estimated Costs	665			665
Contract termination costs
Restructuring Cost and Reserve [Line Items]
Total restructuring costs	(50)			300
Total Estimated Costs	$ 300			$ 300

Cover - shares	6 Months Ended
Cover - shares	Jun. 30, 2026	Jul. 27, 2026
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 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		48,599,066
Entity Central Index Key	0001785530
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2026
Document Fiscal Period Focus	Q2
Amendment Flag	false

Restructuring - Narrative (Details) - USD ($) $ in Thousands	Jun. 30, 2026	Feb. 28, 2026
Restructuring and Related Activities [Abstract]
Total Estimated Costs	$ 6,486	$ 6,500

Common and Preferred Stock - Schedule of Common Stock Reserved for Issuance (Details) - shares	Jun. 30, 2026	Dec. 31, 2025
Class of Stock [Line Items]
Common stock available for issuance (in shares)	15,321,133	13,346,191
Shares reserved for exercises of outstanding stock options
Class of Stock [Line Items]
Common stock available for issuance (in shares)	8,206,431	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)	1,044,648	560,929
Shares reserved for issuance under the 2021 Stock Incentive Plan
Class of Stock [Line Items]
Common stock available for issuance (in shares)	6,070,054	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)	0	791,364

Lease Termination	6 Months Ended
Lease Termination	Jun. 30, 2026
Leases [Abstract]
Lease Termination	13. Lease Termination On May 7, 2026 (the “Modification Date”), 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 (the “Lease Termination Date”). Either party may elect to accelerate the Lease Termination Date by providing 30 days’ prior written notice to the other party, provided that such notice is given no earlier than July 1, 2026 (the “Termination Option”). 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 paid the Landlord an aggregate termination fee of $2.7 million, which represented 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 have no further rent obligations to the Landlord pursuant to the Lease after the Lease Termination Date. We have assessed the Lease Termination and have concluded that it represents a modification to the Lease within the scope of ASC Topic 842, Leases (“ASC 842”). Upon the execution of the Lease Termination, we were reasonably certain that the Termination Option would be exercised, and accordingly we estimated that the lease would terminate on July 31, 2026 for purposes of measuring the modified lease liability. On the Modification Date, we measured our modified lease liability to be $2.5 million. We reduced our lease liability to the modified lease liability through an adjustment to our right-of-use asset as of the Modification Date. We have recognized a reduction to our operating expenses during the three and six months ended June 30, 2026 in the amount of $1.1 million, representing the remaining reduction in our lease liability required after our right-of-use asset was reduced to zero. The reduction to our operating expenses has been allocated between research and development and general and administrative operating expenses proportionately with how the operating lease costs have been allocated over the term of the Lease. As a result of the Lease Termination, we have determined that the estimated useful lives for the majority of our property and equipment will no longer extend beyond July 31, 2026. We have recognized additional depreciation expense during the three and six months ended June 30, 2026 as a result of the change in the estimated useful lives, and will continue to recognize higher-than-expected depreciation expense during each period until our property and equipment is fully depreciated or disposed of. On July 1, 2026, the Landlord exercised the Termination Option to terminate the Lease, effective July 31, 2026.

Strategic Review and Liquidity (Details) - USD ($) $ in Thousands	1 Months Ended
	May 31, 2026	Feb. 28, 2026	Jun. 30, 2026	Dec. 31, 2025	Jun. 30, 2025
Restructuring and Related Activities [Abstract]
Reduction in workforce (percent)	36.00%	64.00%
Cash and cash equivalents			$ 21,987	$ 57,050	$ 77,596

Lease Termination (Details) $ in Thousands		3 Months Ended	6 Months Ended
Lease Termination (Details) $ in Thousands	May 07, 2026 USD ($) ft²	Jun. 30, 2026 USD ($)	Jun. 30, 2026 USD ($)	Jun. 30, 2025 USD ($)
Leases [Abstract]
Notice period to terminate lease	30 days
Area of building space \| ft²	25,778
Lease termination	$ 2,700
Operating lease, liability	$ 2,500
Gain on modification of lease liability		$ 1,100	$ 1,142	$ 0

Condensed Consolidated Balance Sheets (unaudited) - USD ($) $ in Thousands	Jun. 30, 2026	Dec. 31, 2025
Current assets:
Cash and cash equivalents	$ 21,987	$ 57,050
Prepaid expenses and other current assets	905	1,536
Total current assets	22,892	58,586
Property and equipment, net	1,263	4,688
Restricted cash and cash equivalents	0	901
Operating lease right of use asset	0	5,216
Other assets	0	5
Total assets	24,155	69,396
Current liabilities:
Accounts payable	1,939	754
Accrued expenses and other current liabilities	5,924	5,407
Operating lease liability, current	0	1,751
Note payable, net of discount and issuance costs	0	28,236
Total current liabilities	7,863	36,148
Operating lease liability, net of current portion	0	7,684
Derivative liability	0	759
Total liabilities	7,863	44,591
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $0.0001 par value, 5,000,000 shares authorized as of June 30, 2026 and December 31, 2025; no shares issued or outstanding as of June 30, 2026 and December 31, 2025	0	0
Common stock, $0.0001 par value, 200,000,000 shares authorized as of June 30, 2026 and December 31, 2025; 48,599,066 and 48,596,817 shares issued and outstanding as of June 30, 2026 and December 31, 2025, respectively	5	5
Additional paid-in capital	501,559	500,210
Accumulated deficit	(485,272)	(475,410)
Total stockholders’ equity	16,292	24,805
Total liabilities and stockholders’ equity	$ 24,155	$ 69,396

Term Loan - Narrative (Details) - USD ($) $ in Millions		1 Months Ended	3 Months Ended	6 Months Ended
Term Loan - Narrative (Details) - USD ($) $ in Millions	May 06, 2026	May 31, 2024	Jun. 30, 2026	Jun. 30, 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
Repayments of notes payable	$ 31.4
Loss on extinguishment of debt			$ 3.4	$ 3.4
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

Collaboration Revenue	6 Months Ended
Collaboration Revenue	Jun. 30, 2026
Business Combination, Asset Acquisition, Transaction between Entities under Common Control, and Joint Venture Formation [Abstract]
Collaboration Revenue	4. Collaboration Revenue 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 (the “898 Program”), 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”). 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. We were 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 upon meeting certain conditions. On May 6, 2026 (the “Closing”), we entered into an asset purchase agreement (the “Purchase Agreement”) with Jazz. Subject to the terms and conditions of the Purchase Agreement, we sold to Jazz 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 all material assets, properties, rights and interests used or held for use in the conduct of the 898 Program, Jazz paid us upfront consideration of $21.0 million, and has agreed to pay an additional $2.0 million upon the consent to the partial assignment of 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, and as a result, we are no longer eligible to receive payment for meeting the conditions of the development and regulatory milestones or sales-based milestones for any Licensed Products. Concurrently with the Purchase Agreement, we also entered into a license agreement (the “New License Agreement”) with Jazz to license to them certain patents and “know-how” (the “Licensed Patents” and “Licensed Know-How,” respectively). The Licensed Patents and the Licensed Know-How are necessary in the development of the 898 Program, however are not exclusive to the 898 Program. Accounting Analysis under ASC 606 Identification of the Contracts(s) We have previously concluded that the Collaboration Agreement represents a contract with a customer within the scope of ASC Topic 606, Revenue from Contracts with Customers (“ASC 606”). We have assessed the Purchase Agreement and the New License Agreement, and have concluded that they represent a single combined arrangement due to the fact that they were negotiated as a package with a single commercial objective. We have further concluded that the Purchase Agreement and the New License Agreement represent a modification to the Collaboration Agreement within the scope of ASC 606. Identification of Promises and Performance Obligations Previously, we have concluded that the license granted to Jazz under the Collaboration Agreement, and the corresponding “know-how” are not capable of being distinct from the other promises within the contract, and as such, determined that the license and the “know-how” combined with the other research and development services and supply represent a single combined performance obligation. Under the Purchase Agreement and the New License Agreement, Jazz continues to have rights to the same patents and “know-how” that were granted under the Collaboration Agreement. However, under the Purchase Agreement, we transferred ownership of certain patents and “know-how” to Jazz. At the time of the Closing, our performance obligation to Jazz had been fulfilled. Determination of Transaction Price We have assessed the Purchase Agreement and the New License Agreement, and have concluded that they represent a modification that results in an increase in the overall transaction price of the contract with Jazz. We’ve determined that the upfront consideration included in the Purchase Agreement of $21.0 million should be added to the overall transaction price. The Purchase Agreement also includes a $2.0 million contingent payment that is payable to us upon the successful partial assignment of a certain license agreement. We’ve determined that this contingent payment represents variable consideration that should not be included in the transaction price. We used the most likely amount method to estimate variable consideration and estimated that the most likely amount of the contingent payment was zero at the Closing as the success of completing the partial assignment of the license agreement is highly susceptible to factors outside of our control. The Collaboration Agreement included various development and regulatory and sales-based milestones. The payments associated with these milestones represented variable consideration that were excluded from the overall transaction price at the inception of the Collaboration Agreement. As of the Closing, we are no longer entitled to receipt of payment for any of the unpaid milestones included in the Collaboration Agreement. Accordingly, the unpaid milestone payments are no longer considered for inclusion in the overall transaction price as of the Closing. 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 period from the Closing through June 30, 2026, we did not recognize any adjustment to the transaction price associated with the contingent payment. Revenue Recognition As noted above, we have no remaining performance obligation to Jazz as of the Closing. Accordingly, we have recognized revenue of $21.0 million during the three and six months ended June 30, 2026 related to the increase in the overall transaction price described above. As of June 30, 2026, all consideration included in the overall transaction price has been recognized as revenue.

Condensed Consolidated Statements of Stockholders’ Equity (unaudited) (Parenthetical) $ in Thousands	3 Months Ended
	Jun. 30, 2025 USD ($)
Market Offering
Statement [Line Items]
Issuance costs	$ 255

Condensed Consolidated Balance Sheets (unaudited) (Parenthetical) - $ / shares	Jun. 30, 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)	48,599,066	48,596,817
Common stock outstanding (in shares)	48,599,066	48,596,817

Condensed Consolidated Statements of Stockholders’ Equity (unaudited) - 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, 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 income (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, 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]
Net income (loss)	(36,071)
Stockholders' equity, ending balance (in shares) at Jun. 30, 2025			45,335,265
Stockholders' equity, ending balance at Jun. 30, 2025	41,464		$ 5		492,118		(450,659)
Stockholders' equity, beginning balance (in shares) at Mar. 31, 2025			44,827,159
Stockholders' equity, beginning balance at Mar. 31, 2025	57,307		$ 5		489,979		(432,677)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock from at the market offering, net of issuance costs (in shares)			86,340	421,766
Issuance of common stock from at the market offering, net of issuance costs	41	$ 305			41	$ 305
Stock-based compensation expense	1,793				1,793
Net income (loss)	(17,982)						(17,982)
Stockholders' equity, ending balance (in shares) at Jun. 30, 2025			45,335,265
Stockholders' equity, ending balance at Jun. 30, 2025	$ 41,464		$ 5		492,118		(450,659)
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 income (loss)	(13,532)						(13,532)
Stockholders' equity, ending balance (in shares) at Mar. 31, 2026			48,596,817
Stockholders' equity, ending balance at Mar. 31, 2026	$ 12,202		$ 5		501,139		(488,942)
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]
Net income (loss)	$ (9,862)
Stockholders' equity, ending balance (in shares) at Jun. 30, 2026	48,599,066		48,599,066
Stockholders' equity, ending balance at Jun. 30, 2026	$ 16,292		$ 5		501,559		(485,272)
Stockholders' equity, beginning balance (in shares) at Mar. 31, 2026			48,596,817
Stockholders' equity, beginning balance at Mar. 31, 2026	12,202		$ 5		501,139		(488,942)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock from at the market offering, net of issuance costs (in shares)			2,249
Issuance of common stock from at the market offering, net of issuance costs	1				1
Stock-based compensation expense	419				419
Net income (loss)	$ 3,670						3,670
Stockholders' equity, ending balance (in shares) at Jun. 30, 2026	48,599,066		48,599,066
Stockholders' equity, ending balance at Jun. 30, 2026	$ 16,292		$ 5		$ 501,559		$ (485,272)

Financial Instruments and Fair Value Measurements - Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2026	Dec. 31, 2025
Assets:
Total assets	$ 21,489	$ 56,548
Liabilities:
Derivative liability		759
Total liabilities		759
Money market funds
Assets:
Money market funds	21,489	56,548
Level 1
Assets:
Total assets	21,489	56,548
Liabilities:
Derivative liability		0
Total liabilities		0
Level 1 \| Money market funds
Assets:
Money market funds	21,489	56,548
Level 2
Assets:
Total assets	0	0
Liabilities:
Derivative liability		0
Total liabilities		0
Level 2 \| Money market funds
Assets:
Money market funds	0	0
Level 3
Assets:
Total assets	0	0
Liabilities:
Derivative liability		759
Total liabilities		759
Level 3 \| Money market funds
Assets:
Money market funds	$ 0	$ 0

Insider Trading Arrangements	3 Months Ended
Insider Trading Arrangements	Jun. 30, 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