SMA Drug Approval a Huge Windfall for Biogen

James Radke, PhD

As we reported on Friday, the FDA approved Spinraza (nusinersen) for the children and adults with spinal muscular atrophy (SMA), a rare and often fatal genetic disease affecting muscle strength and movement. The data presented to the FDA showed that 40% of SMA patients had improved motor milestones while taking the drug (compared to 0% in the placebo group). 

Priority Review Voucher Worth Millions

The approval also came with a rare pediatric disease priority review voucher for Biogen, the sponsor of the application. This voucher can be used by Biogen for ANY new drug application (NDA) and gives that drug a priority review with the FDA.  A priority review means the drug will be reviewed within 6 months instead of the standard 10 months. And that extra 4 months is worth a small fortune.
The Priority Review Voucher program was introduced to encourage companies to develop drugs for rare pediatric conditions or neglected tropical diseases. If the company’s drug gets approved, the FDA can give them a voucher that they can use for future drug applications. The Priority Review Voucher is also transferable.
Last year, Retrophin sold their voucher to Sanofi for $245 million and Abbvie bought one for $350 million from United Therapeutics. In other words, with the approval of Spinraza, the value of Biogen jumped upwards of $300 million.   

Efficacy and Safety

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

In the study, 23% of SMA patients taking Spinraza died in the study compared to 43% in the control group.  

Spinraza is marketed by Biogen and was developed by Ionis Pharmaceuticals.

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.
Spinraza (nusinersen) is an antisense oligonucleotide (ASO) designed to alter the splicing of pre-mRNA from the SMN2 gene in order to increase production of fully functional SMN protein. Spinraza is approved for Type I, II, and III SMA populations. The drug is expected to cost $200,000 - $250,000 per patient per year.

Patient Support

Biogen has launched SMA360 to provide certain services that address nonmedical barriers to access in the United States (i.e., logistical assistance, product education, insurance benefits investigations and financial assistance. For more information, visit

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