8-K: Climb Bio Reports Promising Budoprutug Data in ITP Study

Climb Bio announced initial data from its Phase 1b study of budoprutug for primary immune thrombocytopenia (ITP), showing good tolerability and positive platelet responses.

Summary

• Climb Bio has released initial data from the Phase 1b portion of its Phase 1b/2a study evaluating budoprutug, an anti-CD19 monoclonal antibody, for adults with primary immune thrombocytopenia (ITP).
• The study is assessing three ascending doses of budoprutug (250 mg, 500 mg, and 1000 mg) administered intravenously in two doses 14 days apart.
• As of June 1, 2026, 15 patients were enrolled in the 250 mg (n=6) and 500 mg (n=9) dose cohorts, with median follow-up of 38 weeks and 12 weeks, respectively.
• Patients were heavily pretreated, with a median of 6 to 7.5 prior therapies and disease duration ranging from 0.5 to 40 years.
• Budoprutug was well-tolerated at 250 mg and 500 mg doses, with no serious adverse events, treatment discontinuations, or infusion reactions; all adverse events were Grade 1 or 2.
• In the 250 mg cohort, B-cell levels decreased by over 90% by Week 4, and mean platelet count increased by 111,000 platelets/L at Week 24.
• Four out of six patients in the 250 mg cohort achieved durable platelet responses, with two experiencing platelet levels above 100 x 10^3/L for over 24 weeks.
• Three out of four patients previously treated with rituximab responded to budoprutug, with two achieving durable and complete responses.

Sentiment

Score: 7

Explanation: StockSavvy.ai views this as a positive development due to the promising initial safety and efficacy data for budoprutug in ITP, supporting further clinical development.

Positives

• Budoprutug was generally well-tolerated at 250 mg and 500 mg dose levels.
• No serious adverse events (SAEs) were reported.
• No treatment discontinuations due to adverse events were observed.
• No infusion-related reactions were reported.
• All reported adverse events were Grade 1 to Grade 2.
• In the 250 mg cohort, B-cell levels were depleted by an average of over 90% by Week 4.
• Mean platelet count increased by 111,000 platelets/L at Week 24 in the 250 mg cohort.
• Durable platelet responses were achieved in four out of six patients in the 250 mg cohort, with two patients maintaining levels above 100 x 10^3/L for over 24 weeks.

Negatives

• The study is ongoing, and the 1000 mg cohort is still enrolling.
• Patients enrolled were heavily pretreated, indicating a challenging patient population.
• While three out of four rituximab-experienced patients responded, not all achieved durable or complete responses.

Risks

• The Company may not be able 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.
• The Company's ability to advance budoprutug and CLYM116 on expected timelines or at all.
• Obtaining and maintaining necessary approvals from the U.S. Food and Drug Administration and other regulatory authorities.
• Replicating positive early-stage clinical trial results in larger trials.
• Competing successfully with other companies developing treatments for immune-mediated diseases.
• Maintaining or protecting intellectual property rights related to budoprutug, CLYM116, and other product candidates.
• Raising the substantial additional capital needed to continue development.

Future Outlook

The Company expects to announce additional data from the ongoing Phase 1b/2a study by the end of 2026. The results to date support continued clinical evaluation of budoprutug in ITP, and enrollment in the 1000 mg cohort is ongoing.

Management Comments

• Results to date support continued clinical evaluation of budoprutug in ITP.

Industry Context

StockSavvy.ai notes that the positive initial data for budoprutug in ITP, particularly regarding tolerability and platelet response, is encouraging in a therapeutic area with significant unmet needs. The anti-CD19 mechanism targeting B-cells is a known approach in autoimmune diseases, and successful demonstration of efficacy and durability in ITP could position Climb Bio competitively.

Stakeholder Impact

• Shareholders: Potential positive impact if budoprutug proves successful in later-stage trials, leading to a new therapeutic option and potential commercialization.
• Patients with ITP: Potential for a new, well-tolerated treatment option with durable platelet responses.
• Healthcare Providers: May consider budoprutug as a treatment option for ITP patients, especially those refractory to prior therapies.

Next Steps

• Continue enrollment in the 1000 mg dose cohort.
• Announce additional data from the study by year-end 2026.
• Continue clinical evaluation of budoprutug in ITP.

Key Dates

Recommendation

The initial data is promising, demonstrating good tolerability and positive early efficacy signals in a difficult-to-treat patient population. However, it is still early-stage data from a Phase 1b study. Further validation in larger, later-stage trials is required to confirm these findings and assess the full potential of budoprutug. Therefore, a 'hold' recommendation is appropriate pending more comprehensive clinical data.

Keywords

Climb Bio, Budoprutug, Immune Thrombocytopenia, ITP, Anti-CD19 Monoclonal Antibody, Phase 1b Study, Platelet Response, B-cell Depletion