WELLESLEY HILLS, Mass., June 11, 2026 — Leads & Copy — Climb Bio, Inc. (Nasdaq: CLYM), a clinical-stage biotechnology company focused on developing therapeutics for immune-mediated diseases, announced initial data from its Phase 1b study of budoprutug, an anti-CD19 monoclonal antibody, in adults with primary immune thrombocytopenia (ITP). The data, presented at the European Hematology Association (EHA) Congress 2026 in Stockholm, Sweden, demonstrate a favorable safety and tolerability profile, significant B-cell depletion, and encouraging platelet responses in heavily pretreated patients.
The ongoing Phase 1b/2a study is designed to evaluate budoprutug in ITP patients to determine optimal dose and regimen selection, assess safety, and measure the depth and duration of platelet response and B-cell depletion. Initial safety and efficacy data are available from the 250 mg cohort, and initial safety data from the 500 mg cohort. Enrollment is continuing in the 1000 mg cohort, with additional data anticipated by the end of 2026.
Edgar D. Charles, M.D., Chief Medical Officer of Climb Bio, stated that patients with chronic ITP often experience prolonged treatment cycles without sustained response. He noted that these initial findings suggest budoprutug’s anti-CD19 mechanism may offer a novel approach in ITP, achieving robust B-cell depletion, durable platelet responses, and an acceptable safety profile. Notably, platelet responses were observed in several patients previously treated with rituximab, indicating potential for a population with significant unmet needs and limited treatment options. These data provide proof-of-concept for budoprutug’s biological activity in ITP and its potential in non-renal autoimmune indications.
The Phase 1b portion of the study (NCT07043946) is assessing three ascending doses of intravenous budoprutug (250 mg, 500 mg, and 1000 mg), administered in two doses 14 days apart, in adults with primary ITP who have undergone at least one prior therapy. As of June 1, 2026, 15 patients were enrolled across the 250 mg (n=6) and 500 mg (n=9) cohorts. The median follow-up was 38 weeks for the 250 mg cohort and 12 weeks for the 500 mg cohort.
Patients in the study were heavily pretreated, with a median of 6 to 7.5 prior lines of therapy and disease durations ranging from 0.5 to 40 years. Budoprutug was generally well-tolerated at both the 250 mg and 500 mg dose levels. No serious adverse events, treatment discontinuations due to adverse events, or infusion-related reactions were reported; all adverse events were Grade 1 or Grade 2. In the 250 mg cohort, B-cell levels decreased by an average of over 90% by Week 4, and the mean platelet count increased by 111,000 platelets/µL at Week 24. Durable platelet responses were observed in four out of six patients in the 250 mg cohort, with two patients maintaining platelet levels above 100 x 103/µL for over 24 weeks. Among the four patients previously treated with rituximab, three responded to budoprutug, two of whom experienced durable and complete responses.
The results support the continued clinical evaluation of budoprutug in ITP. The poster presentation is available on the Pipeline & Science—Publications page of the company’s website.
Climb Bio, Inc. is a clinical-stage biotechnology company committed to delivering impactful, disease-modifying medicines for individuals with immune-mediated diseases, including those affecting kidney health. The company’s pipeline includes budoprutug, an anti-CD19 monoclonal antibody with potential applications in a wide range of B-cell mediated diseases, and CLYM116, an anti-APRIL monoclonal antibody for IgA nephropathy. For more information, visit climbbio.com.
Budoprutug is a clinical-stage anti-CD19 monoclonal antibody designed to target and deplete CD19-expressing B cells, which are implicated in various B-cell mediated immune-driven diseases. It has shown potential for durable B-cell depletion, rapid autoantibody reduction, and clinical remission in primary membranous nephropathy (pMN). Budoprutug is currently being evaluated in clinical trials for pMN, ITP, and systemic lupus erythematosus (SLE). A subcutaneous formulation is also in development. Budoprutug has received Orphan Drug Designation and Fast Track Designation from the FDA for the treatment of pMN.
Immune thrombocytopenia (ITP) is a rare autoimmune disorder characterized by low platelet counts and an increased risk of bleeding. Approximately 85,000 ITP patients are in the United States, with 40% to 50% requiring chronic therapy and about 20% failing multiple treatment lines, highlighting the need for novel approaches.
Source: Climb Bio, Inc.
