FDA Approves First Spinal Muscular Atrophy Drug

The FDA recently approved nusinersen (Spinraza), the first and only drug to treat both children and adults with spinal muscular atrophy. Nusinersen is indicated to treat all patients with this disease.

The novel treatment is administered via injection into the fluid surrounding the spinal cord, according to a press release from the FDA.

Spinal muscular atrophy is a rare genetic disease that affects muscle strength and movement, and is also fatal for many patients. Due to the loss of lower motor neurons that control movement, patients experience weakness and muscle-wasting. Symptoms, rate of disease progression, and age of onset vary for each patient.

The FDA reported that they worked with the manufacturer during drug development to aid in design and implementation of the study that the recent approval is based on, according to the press release.

Included in the trial were 121 patients with infantile-onset spinal muscular atrophy who were diagnosed prior to 6 months old, and were no more than 7-months-old when they received their first treatment.

Patients were randomized to receive an injection of the drug or a placebo in the form of a skin prick without any drug treatment. There were twice as many patients receiving the drug compared with those receiving the placebo.

The trial assessed efficacy by the percentage of patients with improved motor milestones, such as head control, sitting, ability to kick in supine position, rolling, crawling, standing, and walking, the FDA reported.

The manufacturer was asked to conduct an interim analysis to evaluate the drug’s efficacy as early as possible. There were 82 patients included in this analysis.

The investigators discovered that 40% of patients treated with nusinersen who were included in the interim analysis had improvements in motor milestones compared with no patients in the placebo group, according to the press release.

Other clinical trials included symptomatic patients aged from 30-days to 15-years-old at the time of the first dose of nusinersen, and presymptomatic patients who ranged from 8- to 42-days-old.

These studies did not include a control group, and the data were difficult to interpret. However, the results of these additional studies typically appeared to be supportive of the findings from the infantile-onset study, according to the FDA.

Common side effects included upper respiratory infection, lower respiratory infection, and constipation. The manufacturer also warns that low blood platelet count and renal toxicity can occur in some patients.

This drug application was previously granted fast track designation, priority review, and orphan drug designation, the FDA reported.

“There has been a long-standing need for a treatment for spinal muscular atrophy, the most common genetic cause of death in infants, and a disease that can affect people at any stage of life,” said Billy Dunn, MD, director of the Division of Neurology Products in the FDA’s Center for Drug Evaluation and Research. “As shown by our suggestion to the sponsor to analyze the results of the study earlier than planned, the FDA is committed to assisting with the development and approval of safe and effective drugs for rare diseases and we worked hard to review this application quickly; we could not be more pleased to have the first approved treatment for this debilitating disease.”