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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of The Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): August 21, 2026

WEREWOLF THERAPEUTICS, INC.

(Exact name of registrant as specified in its charter)

Delaware

001-40366

82-3523180

(State or Other Jurisdiction

of Incorporation)

(Commission

File Number)

(IRS Employer

Identification No.)


303 Wyman Street, Suite 300
Waltham MA		02451
(Address of Principal Executive Offices)		(Zip Code)

Registrant’s telephone number, including area code: (617) 952-0555

(Former Name or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

☒	Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐	Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐	Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐	Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class

Trading
Symbol(s)

Name of each exchange

on which registered

Common Stock, $0.0001 par value per share

HOWL

The Nasdaq Capital Market

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company ☒

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☒

Item 1.01

Entry into a Material Definitive Agreement

Merger Agreement

On August 21, 2026, Werewolf Therapeutics, Inc., a Delaware corporation (“Werewolf”), entered into an Agreement and Plan of Merger (the “Merger Agreement”) by and among Ambros Therapeutics, Inc., a Delaware corporation (“Ambros”), Werewolf, and Wave Atlantis Merger Sub, Inc., a Delaware corporation and a direct, wholly owned subsidiary of Werewolf (“Merger Sub”).

Pursuant to the Merger Agreement, and upon the terms and subject to the satisfaction of the conditions described therein, Merger Sub will be merged with and into Ambros, with Ambros surviving as a wholly owned subsidiary of Werewolf (the “Merger” and, together with the other transactions contemplated by the Merger Agreement, the “Contemplated Transactions”). The Merger is intended to qualify as a tax-free reorganization for U.S. federal income tax purposes.

Subject to the terms and conditions of the Merger Agreement, (i) immediately prior to the effective time of the Merger (the “Effective Time”), the then-outstanding shares of Ambros preferred stock, par value $0.00001 per share, will be converted into shares of Ambros common stock, par value $0.00001 per share (“Ambros Common Stock”) and (ii) at the Effective Time, each then-outstanding share of Ambros Common Stock (excluding shares held by stockholders who have exercised and perfected appraisal rights for such shares) will be converted into the right to receive a number of shares of Werewolf common stock, par value $0.0001 per share (“Werewolf Common Stock”), calculated in accordance with the exchange ratio as set forth in the Merger Agreement and subject to any election pursuant to the terms of the Merger Agreement to receive pre-funded warrants to acquire Werewolf Common Stock with an exercise price of $0.0001 per share (“Merger Pre-Funded Warrants”) in lieu of any shares of Werewolf Common Stock in excess of the Beneficial Ownership Limitation (as defined in the Merger Agreement). In addition, at the Effective Time, each then-outstanding option to purchase shares of Ambros Common Stock will be assumed by Werewolf and converted into an option to acquire Werewolf Common Stock, with the number of underlying shares and exercise price adjusted in accordance with the exchange ratio as set forth in the Merger Agreement.

At the closing of the Merger (the “Closing” and such date, the “Closing Date”), on a pro forma basis and based upon the number of shares of Werewolf Common Stock and Merger Pre-Funded Warrants and pre-funded warrants to purchase shares of Werewolf Common Stock with an exercise price of $0.001 per share expected to be issued in connection with the Concurrent PIPE Financing (as defined below) (“PIPE Pre-Funded Warrants” and, together with the Merger Pre-Funded Warrants, the “Pre-Funded Warrants”), pre-merger equityholders of Werewolf, other than those participating in the private placement, are expected to own approximately 6.8% of the combined company, pre-merger Ambros stockholders are expected to own approximately 71.7% of the combined company and Investors (as defined below) participating in the private placement are expected to own approximately 21.5% of the combined company, in each case, calculated on a fully diluted basis, using the treasury stock method, and subject to certain assumptions, including (i) an implied valuation for Werewolf of $47.5 million, (ii) a valuation for Ambros of $500.0 million, and (iii) the relative capitalization of Werewolf and Ambros. The percentage of the combined company that each party’s equity holders will own following the Closing is subject to certain adjustments as described in the Merger Agreement.

The Merger Agreement contains representations and warranties of the parties regarding their respective businesses. The Merger Agreement also contains certain covenants made by each of Werewolf and Ambros, including non-solicitation restrictions binding each party and its representatives (subject to certain exceptions as further described in the Merger Agreement) and restrictions on the operation of each party’s business between the date of the Merger Agreement and the Closing.

In connection with the Merger, Werewolf, in cooperation with Ambros, will prepare and file with the Securities and Exchange Commission (the “SEC”) a registration statement on Form S-4 (the “Form S-4”), which will contain a proxy statement to be used by Werewolf to solicit approval of the applicable stockholder matters at a special meeting of Werewolf stockholders (the “Werewolf Stockholder Meeting”). Promptly after the Form S-4 is declared effective, Ambros will, in cooperation with Werewolf, solicit an action by written consent from the requisite Ambros stockholders to approve the Merger Agreement and Contemplated Transactions. At the Werewolf

Stockholder Meeting, Werewolf stockholders will be asked to approve, among other matters, (i) the issuance of Werewolf Common Stock in the Merger and the resulting change of control for purposes of The Nasdaq Stock Market (“Nasdaq”) rules, (ii) if required, the issuance of securities in the Concurrent PIPE Financing pursuant to Nasdaq Listing Rule 5635(d) (clauses (i) and (ii), the “Nasdaq Proposals”), and (iii) amendments to Werewolf’s certificate of incorporation (including a name change (the “Name Change Proposal”), a reverse stock split (the “Reverse Stock Split Proposal” and, together with the Nasdaq Proposals and the Name Change Proposal, the “Werewolf Stockholder Matters”) and an increase in authorized Werewolf Common Stock), and (iv) the equity plan proposals described in the Merger Agreement. Werewolf’s obligation to call, give notice of and hold the Werewolf Stockholder Meeting is not limited or otherwise affected by the commencement, disclosure, announcement or submission of any Superior Offer, any Acquisition Pro