Material Event (Form 8-K)

On October 17, 2025, Climb Bio, Inc. (the "Company") issued a press release announcing the publication of an abstract providing new long-term follow-upclinical data for budoprutug, a novel anti-CD19 monoclonal antibody in development for B-cellmediated diseases. The follow-upclinical data from the previously conducted Phase 1b clinical trial (NCT04652570) of budoprutug in primary membranous nephropathy demonstrated long-term control of proteinuria for up to three years after initial dosing in four patients who received up to four doses of budoprutug. Additionally, in three of the patients, no further immunosuppressive treatment was required. In the trial, no treatment-related adverse events grade 3 or higher were observed.