Climb Bio Files Lawsuit Against Alumis And Acelyrin Seeking Declaratory Judgment Over Budoprutug Milestone Payment Dispute

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.