Climb Bio, Inc. (Nasdaq: CLYM) announced on October 24, 2026, initial data from the PrisMN Phase 2 trial for its anti-CD19 monoclonal antibody, budoprutug, in patients with primary membranous nephropathy (pMN). The data were presented at the American Society of Nephrology (ASN) Kidney Week 2026 in Denver, Colorado.

The PrisMN trial is a dose-escalation study evaluating budoprutug at three dose levels: 200 mg, 600 mg, and 1000 mg. Patients enrolled in the reported cohorts were treatment-experienced and had high proteinuria and elevated anti-phospholipase A2 receptor (PLA2R) antibody levels at baseline.

At Week 12, the 200 mg cohort demonstrated B-cell depletion, reductions in PLA2R antibody levels, and immunologic remission. The mean reduction in PLA2R antibody levels was 70%. Among 13 patients in this cohort, five (38%) achieved immunologic remission. Patients with a baseline PLA2R antibody level below 175 RU/mL showed a mean reduction of 80% at Week 12.

Initial data from the ongoing 600 mg cohort indicate greater drug exposure and deeper peripheral B-cell depletion compared to the 200 mg cohort. At Week 4, the mean suppression of peripheral CD20+ B-cells was 98% at 600 mg, compared to 74% at 200 mg.

A population pharmacokinetic analysis across all budoprutug studies (approximately 120 patients) found that individuals with high proteinuria (median urine protein-to-creatinine ratio of 6.8 g/g) clear the drug at least two-fold faster than non-proteinuric individuals. This supports the evaluation of higher doses in pMN.

Budoprutug has been generally well tolerated in the 200 mg and 600 mg cohorts. Follow-up data are available through Week 12 for the 200 mg cohort and through Week 6 for the 600 mg cohort. Most adverse events were mild to moderate (Grade 1 or 2), and no treatment-related serious adverse events, adverse events leading to treatment discontinuation, or deaths were reported.

In a separate case study presented at the conference, a patient with frequently relapsing minimal change disease (MCD) received 100 mg of budoprutug. The patient achieved three-year steroid-free remission and remained in remission for one year following B-cell reconstitution.

Enrollment is ongoing in the 1000 mg cohort. Climb Bio anticipates sharing additional data from the PrisMN Phase 2 trial in 2027.