Scholar Rock Marks 'Defining Moment' with First Muscle-Targeted Treatment for Spinal Muscular Atrophy

The U.S. Food and Drug Administration on Friday approved ISEMBYLD (apitegromab-mstn) from Scholar Rock (NASDAQ:SRRK) for spinal muscular atrophy (SMA) in adults and pediatric patients aged 2 years and older.

The decision makes ISEMBYLD the first muscle-targeted therapy to demonstrate motor function improvement in individuals already taking an SMN2-targeted drug.

The FDA also awarded Scholar Rock a Rare Pediatric Disease Priority Review Voucher following the decision.

Mechanism Of Action And Disease Impact

SMA is a severe, rare neuromuscular disorder that causes irreversible loss of motor neurons and progressive muscle wasting.

The decline reduces motor function and limits personal independence. As a fully human monoclonal IgG4 antibody, ISEMBYLD targets promyostatin and latent myostatin to inhibit myostatin activation and block its signaling pathway.

Phase 3 SAPPHIRE Study Delivers Robust Results

Patients aged 2 to 12 years receiving 10 mg/kg (recommended dose) of ISEMBYLD alongside SMN2-targeted therapy achieved a 2.2-point improvement on the Hammersmith Functional Motor Scale-Expanded (HFMSE) at 1 year, compared to those receiving SMN2-targeted therapy alone.

Furthermore, 34.2% of ISEMBYLD-treated participants experienced a 3-point or greater HFMSE increase, versus 13.5% in the control group.

Safety Profile And Long-Term Extension

More than 500 individuals participated in global clinical studies for apitegromab, with some receiving treatment for over 7 years.

98% of SAPPHIRE participants chose to join the ONYX long-term extension study.

ISEMBYLD U.S. commercial launch underway, with product available to ship in the coming days.

SRRK Stock Price Activity: Scholar Rock Holding shares were up 6.48% at $59.00 during premarket trading Monday, according to Benzinga Pro data.

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