Climb Bio Secures FDA Fast Track for Budoprutug After 100% B-Cell Depletion
The FDA granted Fast Track Designation to Climb Bio’s anti-CD19 antibody budoprutug for treating primary membranous nephropathy, a rare kidney disease with no approved therapies. Phase 1b results showed 100% B-cell depletion in 5 patients and serologic remission in 3 evaluable by week 48; Phase 2 readouts expected H2 2026.
1. FDA Fast Track Designation
The FDA has granted Fast Track Designation to budoprutug, Climb Bio’s investigational anti-CD19 monoclonal antibody, for primary membranous nephropathy. This status aims to accelerate development and review by enabling more frequent interactions with regulators and eligibility for rolling submissions.
2. Phase 1b Efficacy and Safety Data
In a completed Phase 1b study, budoprutug achieved 100% peripheral B-cell depletion in all 5 patients and induced serologic remission in 3 evaluable subjects by week 48. Clinical outcomes included complete or partial remission in all participants and a favorable safety profile with no treatment-related serious adverse events.
3. Ongoing Phase 2 Trial Plans
Climb Bio is conducting a global Phase 2 open-label trial (PrisMN) to evaluate pharmacodynamics, antibody levels and preliminary efficacy in patients with persistent proteinuria despite optimized RAAS inhibition. Initial data from this dose-ranging study are anticipated in the second half of 2026, guiding Phase 3 dose selection.