WELLESLEY HILLS, Mass. — Climb Bio, Inc. (Nasdaq: CLYM), a clinical stage biotechnology company developing therapeutics for patients with immune-mediated diseases, today announced that the U.S. Food and Drug Administration (FDA) has granted Fast Track Designation to budoprutug, the company’s investigational anti-CD19 monoclonal antibody, for the treatment of primary membranous nephropathy (pMN)—a rare kidney disease for which there are currently no FDA-approved treatments.
“Fast Track Designation recognizes both the urgent need for new therapies in pMN and the compelling early clinical activity generated to date with budoprutug,” said Edgar Charles, M.D., Chief Medical Officer of Climb Bio. “This designation provides the opportunity to support and accelerate our budoprutug development efforts and facilitate closer interaction with the FDA as we work to advance budoprutug into later-stage clinical studies for this serious immune-mediated kidney disease.”
As previously reported, administration of budoprutug in a completed Phase 1b study in pMN demonstrated complete peripheral B-cell depletion in 100% (5/5) of patients, serologic remission in all (3/3) evaluable patients, and complete or partial clinical remission in all (5/5) participants by week 48. The safety profile was favorable with no clinically significant treatment-related serious adverse events observed. Long-term follow-up data demonstrated durable reductions in proteinuria, supporting further investigation of budoprutug as a potential disease modifying therapy for pMN.
Budoprutug is currently being studied in a Phase 2 global open-label, dose-range finding study (PrisMN), which is designed to evaluate pharmacodynamics, including B cells, anti-Phospholipase A2 Receptor (PLA2R) antibody levels, and total immunoglobulin, and preliminary efficacy, including complete and partial remission, in pMN patients with persistent proteinuria despite optimized renin-angiotensin-aldosterone system (RAAS) inhibition, and to identify a dose for Phase 3 clinical development. Climb Bio anticipates sharing initial data from this study in the second half of 2026.
About Primary Membranous Nephropathy (pMN)
Primary membranous nephropathy is an autoantibody mediated disease characterized by proteinuria, nephrotic syndrome, and progressive loss of renal function. Patients with uncontrolled disease may develop chronic kidney disease or end-stage kidney disease, requiring dialysis or transplantation. There are about 75,000 people in the U.S. living with pMN. Currently, there are no FDA approved therapies for pMN.
About Climb Bio, Inc.
Climb Bio, Inc. is a clinical-stage biotechnology company developing therapeutics for patients with immune-mediated diseases. The Company’s pipeline includes, budoprutug, an anti-CD19 monoclonal antibody that has demonstrated B-cell depletion and has potential to treat a broad range of B-cell mediated diseases, and CLYM116, an anti-APRIL monoclonal antibody being developed for IgA nephropathy. For more information, please visit climbbio.com.
About Budoprutug
Budoprutug is a clinical-stage, anti-CD19 monoclonal antibody with the potential to address a broad range of B-cell mediated, immune-driven diseases. Designed with enhanced effector function and low picomolar affinity, budoprutug targets and depletes CD19-expressing B cells, including plasmablasts and certain plasma cells, key sources of pathogenic autoantibodies. Early clinical data suggest budoprutug may offer durable B-cell depletion, rapid reductions in autoantibodies, and clinical remission in primary membranous nephropathy (pMN). Budoprutug is being evaluated in clinical trials for pMN, immune thrombocytopenia (ITP), and systemic lupus erythematosus (SLE). A subcutaneous formulation is also in development to enable broader patient access. Budoprutug has been granted Orphan Drug Designation and Fast Track Designation by the FDA for the treatment of pMN.
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