Infants with spinal muscular atrophy (SMA) receiving risdiplam (Evrysdi®) once daily for 2 years showed improvement in motor functions. They were capable of reaching important developmental milestones, according to a recently published study in the Lancet Neurology.
SMA is a genetic condition in which a mutation in the 5q chromosome causes a deficiency in the SMN protein, which in turn leads to a decrease in important neurological functions. Risdiplam is an orally administered drug that acts as a splicing modifier of the survival motor neuron (SMN) and is currently approved for the treatment of SMA.
The efficacy and safety of risdiplam have already been tested in the second part of the FIREFISH study, which assessed patients until 5 months of treatment. That study reported that infants receiving treatment were able to sit without support after receiving risdiplam. The authors now report the results after 24 months of treatment.
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In this part of the study, 38 infants are still being assessed. The study is taking place in 14 different hospitals in South America, North America, Europe, and Asia. The administered dose was decided by the results of the first trial. It is 0.2 mg/kg for infants between 5 months and 24 months of age and 0.04 for infants younger than 5 months of age.
The endpoints for this part of the study were the ability to sit for 30 seconds without support, the ability to stand alone, and the ability to walk alone. All endpoints were assessed using the Bayley Scales of Infant and Toddler Development, third edition gross motor subscale.
“These three endpoints were compared with a performance criterion of 5% that was defined based on the natural history of type 1 spinal muscular atrophy; the results were considered statistically significant if the lower limit of the two-sided 90% CI was above the 5% threshold,” the authors wrote.
Approximately 44% of patients could stay seated without support for 30 seconds, but none could stand alone or walk. Over 20% of patients presented with respiratory tract infections, making it the most common adverse event.
“The FIREFISH open-label extension phase will provide additional evidence regarding long-term safety and efficacy of risdiplam,” the authors wrote.
Masson R, Mazurkiewicz-Bełdzińska M, Rose K, et al. Safety and efficacy of risdiplam in patients with type 1 spinal muscular atrophy (Firefish Part 2): secondary analyses from an open-label trial. Lancet Neurol. Published online October 13, 2022. doi:10.1016/s1474-4422(22)00339-8