FDA Approves Spinraza (nusinersen) for Spinal Muscular Atrophy

James Radke, PhD

Christmas is coming early to patients with spinal muscular atrophy (SMA).

Late on Friday afternoon, the FDA announced the approval of Spinraza (nusinersen), to treat children and adults with SMA, a rare and often fatal genetic disease affecting muscle strength and movement.
Spinraza is an injection administered into the fluid surrounding the spinal cord.

In a press release, Billy Dunn, M.D., director of the Division of Neurology Products in the FDA’s Center for Drug Evaluation and Research said, “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.”
Dr Dunn added, “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.”
SMA is a hereditary disease that causes weakness and muscle wasting because of the loss of lower motor neurons controlling movement. There is wide variability in age of onset, symptoms and rate of progression.

Spinraza is approved for use across the range of spinal muscular atrophy patients.

Watershed Moment

Kenneth Hobby, President of the advocacy group Cure SMA said, "This is a watershed moment for the entire SMA community, which has worked tirelessly to finally see the day when a therapy for SMA would be made available.  Cure SMA and our families have supported research into this terrible disease for more than 30 years, and many have participated in the critical clinical trials for Spinraza. We are excited to now have the first ever treatment option for SMA, and thank all our supporters and the dedicated researchers who made this possible." 

Efficacy and Safety

The efficacy of Spinraza was demonstrated in a clinical trial in 121 patients with infantile-onset SMA who were diagnosed before 6 months of age and who were less than 7 months old at the time of their first dose.
Patients were randomized to receive an injection of Spinraza, into the fluid surrounding the spinal cord, or undergo a mock procedure without drug injection (a skin prick). The trial assessed the percentage of patients with improvement in motor milestones, such as head control, sitting, ability to kick in supine position, rolling, crawling, standing and walking.
The FDA asked the sponsor to conduct an interim analysis as a way to evaluate the study results as early as possible; 82 of 121 patients were eligible for this analysis and they found that 40% of patients treated with Spinraza achieved improvement in motor milestones while none of the control patients did.

The most common adverse events with Spinraza were upper respiratory infection, lower respiratory infection, and constipation. The FDA approved the drug with warnings and precautions for low blood platelet count and renal toxicity. 

Spinraza is marketed by Biogen of Cambridge, Massachusetts and was developed by Ionis Pharmaceuticals of Carlsbad, California. The sponsors of the application will receive a rare pediatric disease priority review voucher which can be redeemed by a sponsor at a later date to receive priority review of a subsequent marketing application for a different product. 

 What is Spinal Muscular Atrophy?

SMA is a genetic condition that leads to a deficiency in the spinal motor neuron (SMN) protein as a result of mutations of the survival motor neuron 1 (SMN1) gene. The severity of SMA correlates with the amount of SMN protein. Generally, the muscles most affected are those near the shoulders, hips, thighs and upper back. Muscles used for breathing and swallowing may also be affected. Infants with Type I SMA produce very little SMN protein and have a life expectancy of less than two years. Children with Type II have greater amounts of SMN protein but still have a shortened lifespan and are never able to stand independently. Children with Type III have a normal lifespan but accumulate life-long physical disabilities as they grow.
Nusinersen is an antisense oligonucleotide (ASO) that is designed to alter the splicing of pre-mRNA from the SMN2 gene in order to increase production of fully functional SMN protein.  Nusinersen is being investigated in Type I, II, and III SMA populations.

Last year at the American Academy of Neurology annual meeting, we talked with Kenneth Fischbeck, MD of the National Institute of Neurological Disorders and Stroke about some of the treatments in development for SMA and he predicted that a treatment would be approved fairly soon for this devasting disease. 

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