The FDA approved Scholar Rock’s Isembyld (ise-mbyld) as the first therapy targeting muscle loss in spinal muscular atrophy (SMA). The approval covers adults and children age 2 years and older who are receiving SMN2-targeting SMA therapies. The approval follows a late-stage clinical trial showing that, when Isembyld was added to an SMN2-targeting drug, motor skills improved over one year versus decline in the placebo group. The program positions myostatin-pathway inhibition as an option to complement SMN-directed care in a genetically defined population. David Hallal, Scholar Rock CEO, framed the decision as a long-awaited breakthrough after decades of “failed industry-wide efforts” to unlock myostatin inhibition—an explicit acknowledgment of the bar historically faced in muscle-loss indications. For clinicians and developers, the key near-term question is durability of motor benefits and how Isembyld will be sequenced alongside existing SMN therapies in real-world practice.