FDA approves apitegromabe to combat muscle loss in SMA patients

The U.S. Food and Drug Administration (FDA) has approved apitegromabe, marketed as Isembyld, as the first treatment for spinal muscular atrophy (SMA) that acts directly against muscle loss. Developed by Scholar Rock, the monoclonal antibody works by blocking myostatin, a protein that naturally limits muscle growth by reducing protein production and inhibiting repair. Unlike existing SMA therapies that target genetic mechanisms, apitegromabe acts directly on the muscle tissue.

In a 52-week study of 188 SMA patients, those receiving a 10 mg/kg dose showed improved motor function compared to the placebo group, though the treatment was associated with an increased risk of fractures.

Beyond SMA, the drug is being studied for its potential to preserve lean muscle mass during weight loss induced by medications such as tirzepatide (Mounjaro). A phase 2 trial published in Nature Medicine involving adults with overweight or obesity found that while total weight loss was similar between groups, participants receiving apitegromabe lost less lean mass. This application for obesity management has not yet been approved.