Data demonstrate favorable safety and tolerability profile, robust B–cell depletion, and encouraging platelet responses in heavily pretreated patients with primary immune thrombocytopenia
Enrollment ongoing in the high dose cohort, with additional data anticipated by year-end 2026
WELLESLEY HILLS, Mass., June 11, 2026 (GLOBE NEWSWIRE) — Climb Bio, Inc. (Nasdaq: CLYM), a clinical stage biotechnology company developing therapeutics for patients with immune-mediated diseases, today announced initial data from the ongoing Phase 1b portion of its Phase 1b/2a study evaluating budoprutug, an anti-CD19 monoclonal antibody, in adults with primary immune thrombocytopenia (ITP) demonstrating an encouraging safety and tolerability profile, robust B-cell depletion, and meaningful platelet responses in heavily pretreated patients. The initial data are being presented at the European Hematology Association (EHA) Congress 2026, which is being held on June 11-14, 2026, in Stockholm, Sweden.
The ongoing Phase 1b/2a study is evaluating budoprutug in patients with primary ITP to inform dose and regimen selection and assess safety and 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 are available from the 500 mg cohort. Enrollment in the 1000 mg cohort is ongoing.
“Patients with chronic ITP often cycle through multiple therapies without achieving a sustained response,” said Edgar D. Charles, M.D., Chief Medical Officer of Climb Bio. “These initial data suggest that targeting CD19 with budoprutug may offer a differentiated approach in ITP, enabling robust B-cell depletion, durable platelet responses, and an acceptable safety and tolerability profile. Importantly, we observed platelet responses in several patients who had been previously treated with rituximab, highlighting the potential to address a high unmet need population where available treatment options remain limited. Taken together, these data demonstrate biological activity of budoprutug in ITP, and importantly, provide proof-of-concept in a non-renal autoimmune indication. We look forward to sharing additional data from this study later in the year.”
Study Design and Data Highlights
- The Phase 1b portion of the Phase 1b/2a study (NCT07043946) is evaluating three ascending doses (250 mg, 500 mg and 1000 mg) of intravenous budoprutug, administered in two doses 14 days apart, in adults with primary ITP who have received at least one prior therapy
- As of June 1, 2026, 15 patients had been enrolled across the 250 mg (n=6) and 500 mg (n=9) dose cohorts, median follow-up was 38 weeks and 12 weeks for the 250 mg and 500 mg cohorts respectively.
- Patients enrolled were heavily pretreated, with a median of 6 to 7.5 prior lines of therapy and disease duration ranging from 0.5 to 40 years
- Budoprutug was generally well tolerated at both the 250 mg and 500 mg dose levels, with no serious adverse events, no treatment discontinuations due to adverse events, and no infusion related reactions; all adverse events were Grade 1 to Grade 2
- In the 250 mg dose cohort, B-cell levels were depleted by an average of over 90% by Week 4 and mean platelet count increased by 111,000 platelets/µL at Week 24
- Durable platelet responses were achieved in four out of six patients in the 250 mg dose cohort, with two out of six patients experiencing platelet levels >100 x 103/µL for over 24 weeks
- Of the four patients who had previously been treated with rituximab, three responded to treatment with budoprutug, two with durable and complete responses
- Results to date support continued clinical evaluation of budoprutug in ITP; enrollment in the 1000 mg cohort is ongoing
The poster presentation is available on the Pipeline & Science—Publications page of the Company’s website here.
About Climb Bio, Inc.
Climb Bio, Inc. is a clinical-stage biotechnology company with a mission to deliver high impact, disease-modifying medicines for individuals living with immune-mediated diseases, including those affecting kidney health. The Company’s pipeline includes, budoprutug, an anti-CD19 monoclonal antibody that 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.
About Immune Thrombocytopenia
Immune thrombocytopenia (“ITP”) is a rare autoimmune disorder characterized by low platelet counts and an increased risk of bleeding, which can include serious mucosal, gastrointestinal and intracranial bleeding events. There are approximately 85,000 ITP patients in the United States alone. Approximately 40% to 50% of patients require chronic therapy over time, and approximately 20% fail multiple lines of therapy, underscoring the need for novel disease-modifying approaches with the potential to deliver durable responses while maintaining a favorable safety and tolerability profile.
Forward-Looking Statements
This press release contains “forward-looking statements” within the meaning of the Private Securities Litigation Reform Act of 1995, including without limitation statements regarding: future expectations, plans and prospects for Climb Bio; expectations regarding the therapeutic benefits, clinical potential and clinical development of budoprutug; the anticipated timelines for announcing data from Climb Bio’s ongoing and planned clinical trials; the anticipated timelines for enrolling patients in Climb Bio’s ongoing and planned clinical trials; plans for the development strategy for budoprutug; potential commercial opportunity for budoprutug in immune thrombocytopenia; and other statements containing the words “anticipate,” “believe,” “continue,” “could,” “estimate,” “expect,” “intend,” “may,” “plan,” “potential,” “predict,” “project,” “should,” “suggest,” “target,” “would,” “will,” “working” and similar expressions. Forward-looking statements are based on management’s current expectations of future events and are subject to a number of risks and uncertainties that could cause actual results to differ materially and adversely from those set forth in, or implied by, such forward-looking statements. Climb Bio may not actually achieve the plans, intentions or expectations disclosed in these forward-looking statements, and you should not place undue reliance on these forward-looking statements. These risks and uncertainties include, but are not limited to, important risks and uncertainties associated with: the ability of Climb Bio to timely and successfully achieve or recognize the anticipated benefits of its acquisition of Tenet Medicines, Inc. and its technology transfer and exclusive license agreement with Beijing Mabworks Biotech Co., Ltd.; Climb Bio’s ability to advance budoprutug and CLYM116 on the timelines expected or at all and to obtain and maintain necessary approvals from the U.S. Food and Drug Administration and other regulatory authorities; obtaining and maintaining the necessary approvals from investigational review boards at clinical trial sites and independent data safety monitoring boards; replicating in clinical trials positive results found in early-stage clinical trials or nonclinical studies; competing successfully with other companies that are seeking to develop treatments for primary membranous nephropathy, immune thrombocytopenia, systemic lupus erythematosus, IgA nephropathy and other immune-mediated diseases; maintaining or protecting intellectual property rights related to budoprutug, CLYM116 and/or its other product candidates; managing expenses; changes in applicable laws or regulation; the possibility that Climb Bio may be adversely affected by other economic, business and/or competitive factors; and raising the substantial additional capital needed, on the timeline necessary, to continue development of budoprutug, CLYM116 and any other product candidates Climb Bio may develop. For a discussion of other risks and uncertainties, and other important factors, any of which could cause Climb Bio’s actual results to differ materially from those contained in the forward-looking statements, see the “Risk Factors” section, as well as discussions of potential risks, uncertainties and other important factors, in Climb Bio’s most recent filings with the U.S. Securities and Exchange Commission. In addition, the forward-looking statements included in this press release represent Climb Bio’s views as of the date hereof and should not be relied upon as representing Climb Bio’s views as of any date subsequent to the date hereof. Climb Bio anticipates that subsequent events and developments will cause Climb Bio’s views to change. However, while Climb Bio may elect to update these forward-looking statements at some point in the future, Climb Bio specifically disclaims any obligation to do so, except as required by law.
Investors and Media
Carlo Tanzi, Ph.D.
Kendall Investor Relations
ctanzi@kendallir.com
