Onasemnogene-abeparvovec administration to premature infants with spinal muscular atrophy.

Twin girls born at 30 weeks' gestation with spinal muscular atrophy (SMA) received onsasemnogene-abeparvovec (OA) at 3.5 weeks of life. They had no treatment-related adverse events, normal acquisition of motor milestones, and normal neurological examination at 19 months. Genotyping revealed 0 copies of SMN1 and a single, hybrid SMN2 gene containing the positive genetic modifier c.835-44A>G. This was associated with full-length SMN2 blood mRNA expression levels similar to a 2 copy SMA infant. The observed favorable outcomes are likely due to the genetic modifier combined with early drug administration enabled by prematurity.