After obtaining positive results on the motor development of 15 infants with type I SMA, aged less than 6 months and symptomatic during the first gene therapy trial lasting two years (START study), Zolgensma (onasemnogene abeparvovec) will be evaluated over the next 15 years (START long-term follow-up study).
The results published after five years of follow-up in 13 participants (3 under low dose and 10 under therapeutic dose) show that they are all alive and that 12 of them do not need permanent ventilation. Two of them are able to stand without assistance.
Sixty-two percent of them experienced serious adverse effects independent of treatment and not leading to study terminaition. These were mainly acute respiratory failure, pneumonia, dehydration, respiratory distress and bronchiolitis. No elevation of liver function enzymes or malignant tumors or hematologic disorders have been reported.
Five-Year Extension Results of the Phase 1 START Trial of Onasemnogene Abeparvovec in Spinal Muscular Atrophy. J R Mendell, S A Al-Zaidy, K J Lehman et al. JAMA Neurol. 2021 (Mai).