Edgewise Therapeutics Announces Long-Term Sevasemten Data in Becker Muscular Dystrophy

Key Findings

The headline result is that participants treated with sevasemten showed stabilisation of function over the follow-up period, in contrast to the decline that natural history studies predict for Becker:

• CANYON participants (2 years): scores remained stable at +0.1 on the NSAA vs. a predicted decline of 2.9 points
• ARCH participants (3.5 years): scores remained stable at +0.1 on the NSAA vs. a predicted decline of 5.3 points
• Participants who had been on placebo during CANYON and then switched to sevasemten in MESA showed NSAA scores trending upward in their first year on treatment

Published natural history data suggest Becker typically causes NSAA scores to fall by 1.0–1.7 points per year, meaning a loss of 3.0 to 5.1 points over three years would be expected without treatment. Sevasemten appears to have positively altered that trajectory.

Sevasemten also continued to show a favourable safety profile with more than 3 years of exposure.

Understanding the Language

What is Becker muscular dystrophy? Becker is a rare, genetic condition that primarily affects males. Like Duchenne, it is caused by mutations in the dystrophin gene, leading to progressive muscle damage and loss of function. Unlike Duchenne, symptoms can begin at any age and progress more slowly, and there are currently no approved treatments for the underlying disease.

What is MESA? MESA is an open-label extension study, meaning all participants receive the active treatment (sevasemten) and results are tracked over the long-term. It follows on from earlier sevasemten trials (ARCH, CANYON, and DUNE). Notably, 99% of eligible participants from those earlier studies chose to continue into MESA.

What is an open-label extension? Once the initial blinded phase of a trial ends, participants are often offered the chance to continue receiving the study drug in an open-label extension. This allows researchers to gather longer-term safety and efficacy data.

What is the NSAA? The North Star Ambulatory Assessment measures walking ability and physical function through 17 movement-based tasks. It is one of the primary tools used to track disease progression (and treatment response) in muscular dystrophies.

What is sevasemten and how does it work? Sevasemten is an orally administered therapy which works by reducing the force of fast skeletal muscle contractions, this in turn limits the contraction-induced damage that occurs when dystrophin is absent or functionally reduced. Rather than replacing the missing protein, it takes a different approach: protecting the muscle from the damaging forces it is no longer equipped to withstand.