The FDA cleared Scholar Rock’s apitegromab (branded as Isembyld) for spinal muscular atrophy, positioning the drug as a first muscle-targeting therapy alongside existing SMA treatments. The approval covers adults and children at least 2 years old receiving survival motor neuron 2-targeted therapy, after a manufacturing-related delay. Isembyld blocks myostatin, aiming to improve muscle growth and motor function when added to standard-of-care. Commercial expectations highlighted in reporting point to a potentially large addressable market for SMA, where therapies have expanded from earlier survival-focused interventions to additional functional outcomes. For the SMA field, the decision also reframes manufacturing readiness risk—underscoring how “fill-finish” constraints can delay even late-stage-ready assets while regulators preserve quality guardrails.