The U.S. FDA approved Scholar Rock’s Isembyld (apitegromab-mstn), the myostatin inhibitor designed to increase muscle growth, for spinal muscular atrophy (SMA) in adults and children aged at least 2 who are receiving SMN-based therapy. The approval follows a manufacturing-related hold and earlier delays tied to a complete response letter. Analysts and executives highlighted that Isembyld is the first commercial product for SMA that directly targets muscle tissue, shifting treatment strategy beyond survival/SMN augmentation toward motor-function preservation. The clearance reconfigures the rare-disease treatment landscape that has evolved rapidly since 2016. Commercially, the drug’s list price was cited as about $310,000 per year for a typical patient, though actual cost varies by weight and insurance. The immediate industrial implication is that SMA manufacturers will face heightened scrutiny on fill-finish performance and continuity of supply as a new product category starts scaling.