FDA Grants Priority Review to Risdiplam for Spinal Muscular Atrophy Treatment in Presymptomatic Infants Under Age 2 Months

The Food and Drug Administration (FDA) granted priority review of a supplemental new drug application (sNDA) for the use of risdiplam (Evrysdi; PTC Therapeutics, South Plainfield, NJ) to treat presymptomatic infants under age 2 months with spinal muscular atrophy (SMA). 

In the RAINBOWFISH study (NCT03779334), presymptomatic infants treated with risdiplam achieved milestones such as sitting, standing, walking, and maintained the ability to swallow following 12 months of treatment. Infants (n= 5) included in the interim efficacy analysis all maintained the ability to swallow and were able to feed exclusively orally after 12 months of treatment. Out of the infants treated with risdiplam for at least 12 months, 80% (4/5) achieved milestones such as standing and walking independently within World Health Organization (WHO) windows for healthy children. All participants (n=5) met Hammersmith Infant Neurological Examination, Section 2 (HINE-2) motor milestones.

If approved, risdiplam would be the first medicine administered at home for presymptomatic babies with SMA.

“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,” said Levi Garraway, MD, PhD, Genentech’s chief medical officer and head of Global Product Development. “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.”

The most common adverse events (AEs) were abdominal pain (17%), cough (25%), teething (25%), diarrhea (17%), eczema (17%), gastroenteritis (17%), nasal congestion (33%), papule (17%) pyrexia (17%), and vomiting (25%). No treatment-related serious adverse events were reported through the interim safety analysis period (n=12). The AEs were reflective of the age of the infants rather than the underlying SMA. 

Risdiplam is designed to treat SMA by increasing and sustaining production of the survival motor neuron (SMN) protein in the central nervous system (CNS) and peripheral tissues in adults, children and infants as young as 2 months.