CAMBRIDGE, Mass. — A new study published in The Lancet Neurology reports that apitegromab, a muscle-targeted therapy developed by Scholar Rock, significantly improved motor function in children and adults with spinal muscular atrophy (SMA) who were already receiving survival motor neuron (SMN)-targeted treatments.
Results from the pivotal Phase 3 SAPPHIRE trial showed patients on apitegromab achieved statistically significant and clinically meaningful gains on the Hammersmith Functional Motor Scale Expanded (HFMSE), compared with placebo. At 52 weeks, 30.4 percent of patients taking apitegromab improved by at least three points on the HFMSE, versus 12.5 percent on placebo. For a four-point gain, the figures were 19.6 percent versus 6.3 percent. All participants were receiving ongoing SMN-targeted therapies such as nusinersen or risdiplam.
The 188-patient study, involving participants aged 2–21, also found consistent benefits across age groups, treatment types, treatment initiation ages, and geographic regions. Apitegromab was well-tolerated, with no new safety concerns observed.
“These findings reinforce the importance of addressing both motor neuron preservation and muscle function in SMA treatment,” said Dr. Akshay Vaishnaw, Scholar Rock’s president of R&D. “A comprehensive approach can support essential activities like breathing, swallowing, and walking.”
The trial’s lead author, Dr. Thomas O. Crawford of Johns Hopkins University School of Medicine, said the results support the use of muscle-targeted therapies alongside existing SMN treatments.
The U.S. Food and Drug Administration has accepted Scholar Rock’s Biologics License Application for apitegromab under priority review, with a decision expected by September 22, 2025. The therapy is also under review in Europe. If approved, the company anticipates a U.S. launch in 2025 and a European rollout in 2026.
