According to an analysis of data from the RAINBOWFISH clinical trial (NCT03779334), treatment with Evrysdi (risdiplam; Genentech, South San Francisco, CA) in infants with presymptomatic spinal muscular atrophy (SMA) resulted in favorable outcomes. The new results were presented at the 28th World Muscle Society (WMS) Congress and showed that the majority of infants treated with Evrysdi met the primary outcome of the study and were able to sit without support for at least 5 seconds. In 2022, the Food and Drug Administration (FDA) expanded the approval of Evrysdi to treat SMA in children under 2 months of age based on interim data from RAINBOWFISH.

RAINBOWFISH is a phase 2 open-label, single-arm, multicenter clinical study investigating the efficacy, safety, pharmacokinetics, and pharmacodynamics of Evrysdi in 26 infant participants aged less than 6 weeks who had presymptomatic SMA. The primary outcome measure was percentage of participants able to sit without support for 5 seconds, with the primary efficacy population including participants with 2 copies of the SMN2 gene and a compound muscle action potential (CMAP) of at least 1.5 mV at baseline. In individuals diagnosed with SMA, fewer copies of SMN2 and a lower CMAP amplitude is associated with more severe disease and worse functional outcomes.

After 12 months, 80% of participants in the primary efficacy population (n=5) were able to sit without support for 5 seconds, and 81% of participants in the overall study population (N=26) were able to sit independently for 30 seconds, including those with a CMAP amplitude lower than 1.5 mV. As a secondary outcome measure, participants showed cognitive skills equivalent to those found in normal child development after 1 year according to the Bayley Scales of Infant and Toddler Development (BSID III). Additionally, according to Genentech, the majority of participants were able to stand and walk, all participants were able to swallow and feed orally, and no participant required permanent ventilation.

“Evrysdi is the only non-invasive SMA treatment and can be used within hours of birth, potentially allowing these babies to sit, stand and walk, similar to healthy individuals,” said Levi Garraway, MD, PhD, Chief Medical Officer and head of Global Product Development at Genentech. “Evrysdi has now demonstrated its safety and efficacy in babies, children and adults, and these compelling data continue to reinforce our confidence in this treatment.’’