Joanne Donavan, MD, PhD, Chief Medical Officer at Edgewise Therapeutics, discusses the MESA extension study of sevasemten for the treatment of patients with Becker muscular dystrophy (BMD).
BMD is a genetic condition characterized by a lack of working dystrophin protein resulting in the gradual damage and loss of muscle fibers in the heart and skeletal muscles. Symptoms of this disease may begin in childhood to adulthood and slowly worsen over time. Complications of BMD may include cardiomyopathy, difficulty or inability to walk, cognitive changes, kidney, lung, and liver problems, scoliosis, contractures, arrhythmia, and heart failure. BMD is caused by a genetic change in the DMD gene and primarily affects males.
Sevasemten is an investigational fast skeletal myosin inhibitor designed to protect muscle from contraction-induced damage. MESA (NCT06066580) is an open-label extension study evaluating sevasemten long-term safety, tolerability, and efficacy in adults and adolescents with BMD previously treated in sevasemten clinical trials. Patients enrolled in the extension included those previously enrolled in ARCH, CANYON/GRAND CANYON, and DUNE. Long-term data was presented at the 2026 MDA Clinical and Scientific Conference.
North Star Ambulatory Assessment (NSAA) functional scores of ARCH and CANYON trial participants treated with sevasemten remained stable after 3.5 years and 2 years, respectively. CANYON participants on placebo who rolled into the MESA study also had increasing NSAA functional scores during the first year after switching to sevasemten.
This stabilization in function contrasts with natural history data that shows once functional decline begins, its course typically continues along that downward trajectory. Multiple natural history studies in BMD report NSAA scores declining by an average of 1.0 to 1.7 points annually, equating to an expected average functional decline of 3.0 to 5.1 points over 3 years.
Additionally, in MESA, the NSAA scores observed in the sevasemten treatment arm diverged from predicted natural history declines:
- CANYON over 2 years: +0.1 improvement (treated) vs. -2.9 decline (predicted natural history)
- ARCH over 3.5 years: +0.1 improvement (treated) vs. -5.3 decline (predicted natural history)
Top-line results of the sevasemten placebo-controlled pivotal cohort, GRAND CANYON in is expected to be announced in quarter four of 2026. If data is positive, the goal is to advance sevasemten toward a marketing application to seek approval as the first targeted therapy for patients with BMD.
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To learn more about BMD and other rare musculoskeletal conditions, visit https://checkrare.com/diseases/musculoskeletal-diseases/