Newton, Massachusetts, August 18, 2026
Abcuro, Inc. has announced the closing of a $66 million Series D financing to advance the clinical development of ulviprubart, its investigational first-in-class monoclonal antibody for inclusion body myositis (IBM). The financing was led by New Leaf Venture Partners, with participation from existing investors and new investor Rock Springs Capital. The funding is primarily intended to support a new potentially registrational clinical study in patients with less severe IBM, which Abcuro expects to initiate in Q4 2026. The company’s latest financing represents an important development for its IBM program as it prepares for another clinical evaluation of ulviprubart in a disease with no approved pharmacologic treatment. Abcuro said preparations for the upcoming study are already underway following discussions with the U.S. Food and Drug Administration (FDA). If the study generates positive results, the company plans to advance toward submission of a Biologics License Application (BLA).
Abcuro Advances Uleiprubart Toward Registrational Study
The central focus of the financing is the planned ulviprubart clinical study, which is expected to evaluate patients with less severe IBM. Ulviprubart is designed to selectively target KLRG1-positive cytotoxic T cells, a highly differentiated population of immune cells believed to contribute to chronic muscle damage in IBM. Rather than broadly suppressing the immune system, the antibody is intended to selectively deplete these pathogenic KLRG1+ T cells while sparing other immune-cell populations. This targeted mechanism forms the scientific basis of Abcuro’s approach to developing a potential disease-modifying therapy for IBM. The company expects the new study to begin during Q4 2026, with topline results anticipated in the second half of 2028, subject to study execution and development timelines. The program is therefore moving toward a potentially important clinical milestone following the company’s previous Phase 2/3 evaluation.
Previous IBM Data Support Further Clinical Development
The decision to advance ulviprubart follows findings from the Phase 2/3 MUSCLE study, which evaluated the therapy in patients with IBM. Results presented at the 6th Global Conference on Myositis in March 2026 showed that the study did not achieve statistical significance for its overall analysis, an important limitation that should not be overlooked. However, a predefined analysis in patients with less severe IBM, identified by an IBM Functional Rating Scale score greater than 29, showed a reported 50% slowing of disease progression compared with placebo. Ulviprubart also demonstrated a favorable safety and tolerability profile relative to placebo. These findings have encouraged Abcuro to focus its next clinical study on the less severe IBM population. The company believes this patient group could provide an opportunity to further evaluate whether selective targeting of KLRG1+ cytotoxic T cells can translate into clinically meaningful slowing of disease progression. The upcoming study will be important in determining whether the earlier signal can be replicated in a potentially registrational setting.
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$66M Financing Strengthens Abcuro’s IBM Development Strategy
The $66 million Series D financing provides Abcuro with resources to execute its next major clinical development stage while maintaining focus on its lead program. IBM is a rare, progressive autoimmune muscle disease characterized by worsening muscle weakness and functional decline, including difficulties with grip, dexterity and mobility. Abcuro estimates that approximately 40,000 people in the United States have diagnosed IBM and that approximately 35,000 patients are affected across major European countries and Japan. Patients with less severe disease are estimated to represent nearly half of the overall IBM population. With no approved pharmacologic therapy currently available, the development of targeted treatments remains an area of significant unmet medical need. Abcuro’s strategy is centered on using precision immunotherapy to address pathogenic cytotoxic T cells while potentially reducing the broader immune suppression associated with less selective approaches. The new financing and planned Q4 2026 study initiation therefore mark a significant step in the company’s effort to establish ulviprubart as a potential treatment option for IBM and advance the program toward a possible BLA submission.
Source:Abcuro, press relese
