Lisbon, Portugal – March 26, 2026
Abcuro presented results from its Phase 2/3 MUSCLE clinical trial evaluating ulviprubart (ABC008) in patients with inclusion body myositis (IBM) at the Global Conference on Myositis (GCOM) 2026, highlighting a favorable safety profile and encouraging efficacy signals in specific patient subgroups despite not meeting primary endpoints. The findings underscore both the challenges and progress in developing therapies for rare autoimmune muscle diseases with high unmet medical need.
Phase 2/3 Trial Shows Safety but Misses Primary Endpoints
The global Phase 2/3 MUSCLE trial, a randomized, double-blind, placebo-controlled study involving approximately 272 patients with inclusion body myositis, evaluated the efficacy and safety of ulviprubart over a 76-week treatment period. The study, however, did not meet its primary endpoint, measured by changes in the IBM Functional Rating Scale (IBMFRS), nor did it achieve key secondary endpoints.
Despite this outcome, ulviprubart demonstrated a favorable safety and tolerability profile compared to placebo, with no major safety signals identified. This is particularly significant in the context of autoimmune disease therapies, where balancing efficacy with safety remains a critical challenge. The results reinforce the potential of ulviprubart as a well-tolerated therapeutic candidate, supporting continued investigation in future studies.
Subgroup Analysis Reveals Promising Clinical Signals
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Importantly, pre-specified subgroup analyses revealed clinically meaningful trends in patients with mild to moderate disease, suggesting that ulviprubart may have disease-modifying potential in earlier stages of IBM. In these patients, improvements were observed in functional outcomes and disease progression markers, indicating that targeting cytotoxic T cells earlier in the disease course could yield greater therapeutic benefit.
Ulviprubart is a first-in-class monoclonal antibody targeting KLRG1, designed to selectively deplete highly cytotoxic T cells while preserving essential immune function. This targeted mechanism addresses a key driver of muscle damage in IBM, where overactive immune cells attack muscle tissue, leading to progressive weakness and disability.
The subgroup findings provide valuable insights into patient stratification and personalized treatment approaches, which are increasingly important in rare diseases where heterogeneity in disease progression can impact clinical outcomes.
Advancing Development Strategy in Rare Disease Space
Following the MUSCLE study results, Abcuro plans to engage with regulatory authorities, including the FDA, to refine its clinical development strategy, with a focus on targeting earlier-stage patients and optimizing trial design. The company is expected to continue evaluating ulviprubart in ongoing and future studies, including open-label extension trials to assess long-term safety and efficacy.
Inclusion body myositis is a rare, progressive autoimmune disease with no approved pharmacologic treatments, affecting tens of thousands of patients globally. The condition leads to gradual muscle degeneration, loss of mobility, and reduced quality of life, making it a critical area for therapeutic innovation.
The MUSCLE trial represents one of the most advanced clinical efforts to address this disease, and while the overall results were mixed, the data provide a foundation for future development and refinement of targeted immunotherapies. The continued focus on precision medicine, immune modulation, and patient-specific treatment strategies is expected to drive progress in this challenging therapeutic area.
Overall, the presentation of MUSCLE trial data at GCOM 2026 highlights the evolving landscape of autoimmune disease research and late-stage clinical development, where even partial successes contribute valuable insights toward achieving effective treatments. Ulviprubart’s safety profile and subgroup efficacy signals position it as a potential future option for patients with early-stage IBM, reinforcing the importance of continued innovation in rare disease therapeutics.
Source: Abcuro press release
