Satellos Bioscience announced on November 6 that, following feedback from the US Food and Drug Administration, it has selected change in vastus lateralis fat fraction measured by magnetic resonance imaging as the primary efficacy endpoint in BASECAMP, its Phase 2 study in Duchenne muscular dystrophy. The imaging measure replaces dynamometry, a test of muscle force, as the study’s primary endpoint, and the company has submitted a protocol amendment to implement the change.
BASECAMP is a global, randomised, double blind, placebo controlled proof of concept study of forazapadin, an oral AAK1 inhibitor also known as SAT-3247, in 53 ambulatory boys aged 7, 8 or 9. The design pairs a 12 week placebo controlled period with a 36 week period in which all participants receive the drug. Topline data from the placebo controlled period are expected in the first quarter of 2027.
The supporting evidence comes from TRAILHEAD, the company’s open label Phase 2 study in adults. In four adults treated for about five months, MRI measured fat fraction in the biceps brachii fell by a mean of 3.7 percentage points, from 49.7 percent at baseline to 46.0 percent at day 140. That is a small, uncontrolled observation in a different muscle from the thigh muscle BASECAMP will measure, and the company presents it as rationale for the endpoint rather than as evidence of efficacy.
Two limits frame the announcement. The FDA discussion addressed the relationship between fat fraction and clinical endpoints without specifying a required degree of change, and the release does not report FDA acceptance of fat fraction as a surrogate endpoint capable of supporting approval. Functional outcomes remain in the study as secondary and exploratory measures. The first quarter 2027 readout will therefore show whether the drug moves the imaging measure against placebo, a cleaner question than the one dynamometry posed, but not yet the approval question.