The US Food and Drug Administration (FDA) granted priority review of a supplemental New Drug Application for the use of risdiplam (Evrysdi®) in the treatment of presymptomatic babies with spinal muscular atrophy (SMA) aged less than 2 months.

In a press release from Genentech, the makers of risdiplam, chief medical officer and head of global product development Levi Garraway, MD, PhD, said, “Treating very young babies with Evrysdi before SMA symptoms arise may help them to achieve milestones such as standing and walking within timeframes typical of healthy infants.”

The application contains data from the phase 2 clinical trial called RAINBOWFISH, which showed that most presymptomatic babies treated with risdiplam achieved the key milestones of sitting, standing, and walking after 1 year of treatment. Moreover, all babies could still swallow and were able to feed exclusively by mouth after 1 year.

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The trial’s aim is to investigate the safety, efficacy, pharmacokinetics, and pharmacodynamics of risdiplam in an estimated 25 babies, aged 0 to 6 months, with genetically diagnosed SMA but no symptoms yet. It is currently recruiting participants in the United States, Australia, Belgium, Brazil, Canada, China, Italy, Poland, Russia, Saudi Arabia, and Taiwan.

Based on the interim safety analysis, there were no treatment-related serious adverse events during the trial. The most common adverse events were nasal congestion, cough, teething, vomiting, eczema, stomach pain, diarrhea, gastroenteritis, papules, and fever.

Risdiplam is also being tested in 4 other clinical trials, 2 of which met their primary endpoints. It is a disease-modifying treatment administered orally that works by increasing the amount of functional survival motor neuron (SMN) protein made from the SMN2 gene. Patients with SMA cannot make enough SMN protein due to a mutation in the SMN1 gene, the main gene from which most of the SMN protein is made.

The FDA already approved risdiplam to treat SMA patients aged 2 months and older. Dr. Garraway stated, “Extending treatment access for the youngest members of the SMA community is crucial and we look forward to working with the FDA on this application.”


Genentech’s Evrysdi (risdiplam) granted FDA priority review for treatment of pre-symptomatic babies under 2 months of age with spinal muscular atrophy (SMA). News release. Genentech; January 24, 2022.

A study of risdiplam in infants with genetically diagnosed and presymptomatic spinal muscular atrophy (Rainbowfish). December 19, 2018. Updated January 27, 2022. Accessed February 1, 2022.