The US Food and Drug Administration (FDA) has approved ISEMBYLD (apitegromab-mstn) for adults and children aged two years and older with spinal muscular atrophy (SMA) who are receiving a survival motor neuron 2 (SMN2)-targeted treatment. Developed by Scholar Rock, ISEMBYLD is the first muscle-targeted treatment approved for people with SMA.
SMA causes progressive loss of motor neurons and muscle wasting, leading to declining motor function and reduced independence. ISEMBYLD is designed to address the muscular component of the disease by inhibiting myostatin signalling, potentially helping to improve motor function alongside existing SMN2-targeted therapies.
The approval was supported by results from the Phase 3 SAPPHIRE study, a randomised, double-blind, placebo-controlled trial. At one year, participants receiving the recommended 10 mg/kg dose of ISEMBYLD alongside an SMN2-targeted treatment had a 2.2-point improvement in the Hammersmith Functional Motor Scale-Expanded (HFMSE) compared with those receiving background treatment and placebo. The study’s main efficacy population included 103 participants aged two to 12 years.
A clinically meaningful increase of at least three HFMSE points was observed in 34.2% of patients receiving ISEMBYLD, compared with 13.5% receiving placebo. The reported nominal p-value for the primary analysis was 0.0121.
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The safety database includes more than 500 people treated with apitegromab across clinical studies. Common adverse reactions in SAPPHIRE included upper respiratory tract infections, vomiting, cough, viral infections, headache, gastroenteritis, pharyngitis and hypersensitivity. Fractures occurred in 9% of patients receiving 10 mg/kg, compared with 2% in the placebo group.
This news item has been summarised using AI and checked by humans before publication.
Sources
US Food and Drug Administration
FDA Orphan Drug Designations and Approvals
ISEMBYLD prescribing information
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