Apitegromab Improves Motor Function in Spinal Muscular Atrophy

MONDAY, Aug. 25, 2025 (HealthDay News) — For patients with nonambulatory type 2 or type 3 spinal muscular atrophy, apitegromab, a monoclonal antibody that inhibits myostatin activation, improves motor function versus placebo, according to a study published online Aug. 13 in the Lancet Neurology.

Thomas O. Crawford, M.D., from Johns Hopkins Medicine in Baltimore, and colleagues examined the safety and efficacy of apitegromab in patients with nonambulatory type 2 or type 3 spinal muscular atrophy receiving nusinersen or risdiplam in a double-blind, phase 3 trial conducted at 48 hospitals. Eligible participants aged 2 to 12 years were randomly assigned to receive apitegromab 20 mg/kg, apitegromab 10 mg/kg, or placebo every four weeks, and those aged 13 to 21 years were randomly assigned to receive apitegromab 20 mg/kg or placebo every four weeks.

A total of 188 patients were enrolled (156 aged 2 to 12 years; 32 aged 13 to 21 years); 128 and 60 participants received apitegromab and placebo, respectively. The researchers found that the least-squares mean difference in the Hammersmith Functional Motor Scale-Expanded (HFMSE) change from baseline at 12 months was 1.8 points for participants aged 2 to 12 years receiving apitegromab versus placebo (95 percent confidence interval [CI], 0.30 to 3.32). For apitegromab 20 mg/kg versus placebo, the least-squares mean difference in HFMSE change from baseline was 1.4 (95 percent CI, –0.34 to 3.13). Similar incidence and severity were seen for adverse events between apitegromab and placebo, consistent with spinal muscular atrophy and background spinal muscular atrophy therapy.

“Apitegromab improved motor function and was generally well tolerated, supporting the use of muscle-targeting therapy for individuals with spinal muscular atrophy,” the authors write.

The study was funded by Scholar Rock, which is developing apitegromab.

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