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FDA Approves First Therapy to Target Muscle Loss in

Spinal Muscular Atrophy

The U.S. Food and Drug Administration has approved Isembyld (apitegromab-mstn) for the treatment of spinal muscular atrophy (SMA) in adults and pediatric patients 2 years of age and older who are currently receiving an SMN2-targeted treatment.

Isembyld is the first approved SMA therapy to directly target muscle loss. Isembyld works by blocking myostatin, a protein that limits muscle growth, helping patients stabilize muscle and maintain greater muscle strength and function alongside their current treatment.

In a 52-week phase 3 clinical trial, patients treated with Isembyld showed statistically significant improvements in motor function compared to placebo and were more than twice as likely to achieve a clinically meaningful improvement in their ability to move and function (34.2% vs. 13.5%).

Isembyld carries a warning for an increased risk of fractures, including serious fractures. It may also cause fetal harm and affect reproductive function.

Isembyld was given Fast Track, Orphan Drug and Rare Pediatric Disease designations. The approval of Isembyld was granted to Scholar Rock, Inc.

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