Scholar Rock Clears FDA Hurdle With First Muscle-Targeted SMA Drug

Scholar Rock shares climbed 9.1% to $60.45 in premarket trading Monday after the FDA approved ISEMBYLD, giving the biotechnology company its first commercial product and clearing a regulatory obstacle that had shadowed the stock for a year.

The approval, announced Friday, September 11, arrived ahead of the agency’s September 30 action deadline. It covers adults and children at least 2 years old with spinal muscular atrophy who are already receiving an SMN2-targeted treatment, including therapies such as Spinraza and Evrysdi that help preserve motor neurons.

ISEMBYLD, or apitegromab-mstn, takes a different approach. It inhibits myostatin, a protein that restrains muscle growth, aiming to address the muscle wasting that can continue even when SMN2-directed medicines slow the underlying nerve damage. The FDA described it as the first approved SMA therapy to directly target muscle loss.

The decision rested on Scholar Rock’s 52-week SAPPHIRE trial, in which all participants received background SMN2 therapy. Among patients aged 2 to 12, the recommended 10-milligram-per-kilogram dose produced a 2.2-point improvement over placebo on the Hammersmith Functional Motor Scale-Expanded. A clinically meaningful improvement of at least three points occurred in 34.2% of treated patients, compared with 13.5% on placebo.

That efficacy profile now faces the harder commercial test. Scholar Rock said product shipments would begin within days, while management told investors Monday that the annual list price for a typical patient would be about $310,000. Coverage decisions, infusion-center logistics and the need for combination treatment will shape how quickly physicians adopt the drug.

Manufacturing had already forced the company to navigate a difficult path. The FDA rejected the original application in September 2025 after raising concerns at a fill-finish facility formerly operated by Catalent and now owned by Novo Nordisk. Scholar Rock later removed that site from its filing and advanced a second U.S. facility, reducing the supply risk before this year’s approval.

The company also received a rare pediatric disease priority review voucher, an asset that may accelerate a future application or carry financial value if transferred. For investors, the FDA action converts Scholar Rock from a clinical-stage biotech into a launch-stage drugmaker. Execution now matters as much as science.