Scholar Rock wins FDA approval for ISEMBYLD SMA therapy after year-long manufacturing delay

Scholar Rock said on September 11, 2026, that the U.S. FDA approved ISEMBYLD (apitegromab-mstn), its muscle-targeted therapy for spinal muscular atrophy (SMA).

The treatment is approved for adults and children aged 2 and older with SMA who are already receiving an SMN2-targeted therapy.

The approval came nearly a year after the FDA issued a Complete Response Letter on September 22, 2025. The delay was tied to manufacturing-compliance problems at Catalent Indiana, a fill-finish facility acquired by Novo Nordisk—not to concerns about apitegromab’s safety or efficacy.

In the pivotal study, the recommended 10 mg/kg dose improved HFMSE motor-function scores by 2.2 points versus placebo, a statistically significant result.

Scholar Rock said commercial launch preparations were underway, with product expected to become available for shipment within days. The company also received an FDA Rare Pediatric Disease Priority Review Voucher.