Scholar Rock receives first FDA approval for rare muscle-wasting disease therapy

The U.S. FDA has approved Scholar Rock's Isembyld (apitegromab) for patients aged 2 and older with spinal muscular atrophy (SMA), marking the company's first regulatory approval. As the first muscle-targeted therapy designed to block myostatin and improve motor function, Isembyld addresses a rare genetic disorder affecting 10,000 Americans. Clinical trials show significant motor improvements when combined with existing SMN2-targeting drugs. Scholar Rock shares surged 23% on the news, with analysts forecasting peak sales of $2.1 billion by 2035.

Isembyld FDA approval

• ▪Scholar Rock shares rose over 23% in after-market trading following the announcement of the Food and Drug Administration approval of Isembyld on September 11, 2026
• ▪The U.S. Food and Drug Administration approved Isembyld for use in adults and children aged 2 years and older who are currently receiving spinal muscular atrophy therapies that target the SMN2 gene
• ▪The U.S. Food and Drug Administration approved Scholar Rock's injectable therapy, sold as Isembyld, on September 11, 2026, marking the company's first regulatory approval

Spinal muscular atrophy treatment

• ▪According to the Muscular Dystrophy Association, spinal muscular atrophy is estimated to affect roughly 10,000 children and adults in the United States
• ▪Spinal muscular atrophy is a genetic disorder that damages motor neurons, causing progressive muscle weakness and problems with movement, breathing, and swallowing

Myostatin inhibition mechanism

• ▪Isembyld, chemically known as apitegromab, selectively blocks the activation of myostatin, a protein that limits muscle growth, with the aim of increasing muscle mass and strength
• ▪Scholar Rock is testing apitegromab to preserve muscle in obesity, competing with more than a dozen companies developing treatments aimed at minimizing muscle loss during weight loss

Clinical trial motor function

• ▪A late-stage clinical trial found that, when combined with an SMN2-targeting drug, Isembyld caused young patients' motor skills to improve after a year, while those in a placebo group declined
• ▪The Food and Drug Administration approval of Isembyld was based on late-stage clinical trial data showing that the therapy significantly improved motor function for patients with spinal muscular atrophy compared with a placebo

Competitive SMA therapy market

• ▪Scholar Rock plans to manufacture Isembyld using a manufacturing facility located in the United States
• ▪Isembyld will compete in the spinal muscular atrophy treatment market with Biogen's Spinraza, Novartis' gene therapy Zolgensma, and Roche's oral Evrysdi

Commercial sales projections

• ▪Cantor analysts stated that the approval of Isembyld positions Scholar Rock to be one of the best long-term growth stories in biotechnology based on geographic, indication, and product line expansions
• ▪BMO Capital Markets analyst Evan Seigerman forecasts 2035 adjusted worldwide peak sales of $2.1 billion for Scholar Rock's Isembyld