FDA approves new drug for spinal muscular atrophy
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The Food and Drug Administration approved Isembyld, a medication for spinal muscular atrophy (SMA), a rare genetic disease. Scholar Rock, the drug’s manufacturer, will sell Isembyld for around $310,000 per year, with costs varying based on weight and insurance. This approval changes treatment for SMA, a condition that previously had no approved medicines as recently as ten years ago.
Before 2016, doctors could only offer supportive care for SMA, a disease causing progressive weakness and often fatal in infants.
Since then, the FDA has approved three other therapies that help patients survive and develop. However, these existing treatments don’t fully restore motor function, creating a need for additional options. Isembyld works by blocking myostatin, a protein that limits muscle growth. Clinical trials showed that Isembyld, when used with standard treatments, improved motor function more than standard care alone.
Scholar Rock invested in preparing for Isembyld’s launch after positive trial results in late 2024, including building a sales team and restructuring leadership. The FDA initially rejected Isembyld due to manufacturing issues, but Scholar Rock addressed these problems by switching to a different production facility. The agency also warned that Isembyld may increase the risk of bone fractures, though these occurred in patients with existing risk factors and did not cause anyone to stop treatment.
