Climb Bio’s anti-CD19 antibody budoprutug received FDA Fast Track designation for primary membranous nephropathy following Phase 1b data showing B-cell depletion and clinical remission; Phase 2 PrisMN study is ongoing.
Written By: Dillikumari A. BPharm
Reviewed By: Pharmacally Editorial Team
Fast Track Designation for Anti-CD19 Therapy
Climb Bio, Inc. announced that the U.S. Food and Drug Administration has granted Fast Track Designation to budoprutug, an investigational anti-CD19 monoclonal antibody, for the treatment of primary membranous nephropathy (pMN), a rare autoimmune kidney disease with no currently approved therapies. The designation is intended to support accelerated development and enable more frequent regulatory interactions.
Climb Bio’s Chief Medical Officer Edgar Charles stated that the Fast Track status reflects the unmet need in pMN and the early clinical activity observed with budoprutug, and is expected to help advance the therapy into later-stage studies.
Phase 1b Data Show B-Cell Depletion and Clinical Responses
In a completed Phase 1b study (NCT04652570) in patients with pMN, budoprutug demonstrated complete peripheral B-cell depletion in 100% (5/5) of treated participants. Serologic remission was observed in all evaluable patients (3/3), while complete or partial clinical remission occurred in all participants (5/5) by week 48.
The therapy showed a favorable safety profile, with no clinically significant treatment-related serious adverse events reported. Long-term follow-up also demonstrated durable reductions in proteinuria, supporting continued clinical development as a potential disease-modifying therapy.
Ongoing Phase 2 PrisMN Study
Budoprutug is currently being evaluated in the global Phase 2 open-label dose-range finding PrisMN study (NCT07096843). The trial is designed to assess pharmacodynamic markers including B-cell depletion, anti-PLA2R antibody levels, and total immunoglobulin. The study will also evaluate preliminary efficacy, including complete and partial remission, in patients with persistent proteinuria despite optimized renin-angiotensin-aldosterone system inhibition.
The study aims to identify a dose for Phase 3 development. Climb Bio expects to report initial data in the second half of 2026.
About Primary Membranous Nephropathy
Primary membranous nephropathy is an autoantibody-mediated kidney disease characterized by proteinuria, nephrotic syndrome, and progressive loss of renal function. Uncontrolled disease can lead to chronic kidney disease or end-stage kidney disease requiring dialysis or transplantation. Approximately 75,000 people in the United States are living with pMN, and no FDA-approved treatments are currently available.
About Budoprutug
Budoprutug is a clinical-stage anti-CD19 monoclonal antibody designed with enhanced effector function and low picomolar affinity. The therapy targets CD19-expressing B cells, including plasmablasts and certain plasma cells, which are key sources of pathogenic autoantibodies.
Early clinical findings suggest the therapy may provide durable B-cell depletion, rapid reduction in autoantibodies, and clinical remission in pMN. Budoprutug is also being evaluated in immune thrombocytopenia and systemic lupus erythematosus, and a subcutaneous formulation is under development. The therapy has received both Orphan Drug Designation and Fast Track Designation from the FDA for pMN.
Reference
Climb Bio Announces FDA Fast Track Designation for Budoprutug for the Treatment of Primary Membranous Nephropathy, 07 April 2026, https://ir.climbbio.com/news-releases/news-release-details/climb-bio-announces-fda-fast-track-designation-budoprutug
A Phase 2 Study of Budoprutug in Subjects with Primary Membranous Nephropathy (PrisMN), ClinicalTrials.gov ID NCT07096843, https://clinicaltrials.gov/study/NCT07096843
Efficacy and Safety of VB119 in Subjects with Membranous Nephropathy, ClinicalTrials.gov ID NCT04652570, https://clinicaltrials.gov/study/NCT04652570
About the Writer
DilliKumari is a Pharmacy graduate based in Ariyur, Puducherry. She has a strong interest in pharmacovigilance and is particularly drawn to data analysis within the healthcare field. She is known for her willingness to learn and continuously improve, with a keen attention to detail that sometimes leads her to spend extra time refining her work.