The FDA cleared Scholar Rock’s Isembyld (apitegromab, myostatin inhibitor) for spinal muscular atrophy in adults and in children at least 2 years old who are receiving a survival motor neuron (SMN) 2-targeted therapy. The approval follows a prolonged review that included a complete response letter related to manufacturing issues at a fill-finish site. Isembyld is positioned as the first commercially approved “muscle-targeted” SMA treatment, meant to complement SMN-directed drugs rather than replace them. Scholar Rock had prepared a launch plan after earlier trial readouts that showed improved motor function versus standard care. Analysts have previously framed the product as capable of substantial peak sales, but the FDA action immediately shifts focus to commercialization execution, supply-chain readiness, and uptake alongside existing SMA standards of care.