8-K

Climb Bio, Inc.

Date: December 31, 2025

/s/ Aoife Brennan

Aoife Brennan, M.B., Ch.B.

President and Chief Executive Officer

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): December 31, 2025

CLIMB BIO, INC.

(Exact Name of Registrant as Specified in its Charter)

Delaware

001-40708

83-2273741

(State or Other Jurisdiction

of Incorporation)

(Commission

File Number)

(IRS Employer

Identification No.)

20 William Street, Suite 145

Wellesley Hills, Massachusetts

02481

(Address of Principal Executive Offices)

(Zip Code)

Registrant’s Telephone Number, Including Area Code: (866) 857-2596

Not Applicable

(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, par value $0.0001 per share

CLYM

The Nasdaq Stock Market LLC

(The Nasdaq Global 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 8.01

Other Events.

On December 31, 2025, Climb Bio, Inc. (the “Company”) filed a complaint (the “Complaint”) in Delaware Superior Court against Alumis Inc. (“Alumis”) and its wholly owned subsidiary, Acelyrin, Inc. (“Acelyrin”), relating to a dispute concerning an Asset Purchase Agreement, dated as of January 11, 2024, between Acelyrin and Tenet Medicines, Inc., a wholly owned subsidiary of the Company (the “APA”), which originally provided for the acquisition of certain assets of Acelyrin related to budoprutug, a clinical-stage anti-CD19 monoclonal antibody that the Company is developing to treat B-cell mediated diseases. The Complaint seeks a declaratory judgment that the Company’s budoprutug drug candidate is not a “Product” under the APA and the Company does not owe a milestone payment sought by Alumis in connection with its development of budoprutug. A copy of the Complaint is attached hereto as Exhibits 99.1 and is incorporated herein by reference.

Item 9.01.

Financial Statements and Exhibits.

(d) Exhibits


Exhibit No.		Description

99.1		Complaint, dated December 31, 2025

104		Cover Page Interactive Data File (embedded within the Inline XBRL document).

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

SEC Form 8-K filed by Climb Bio Inc.