SMN2 and proximal spinal muscular atrophy: The SPR1NT study of onasemnogene abeparvovec (gene therapy) is a phase 3, multicentre, open-label, single-arm study which enrolled 29 babies with presymptomatic SMA, i.e., no clinical evidence of neuromuscular disease (14 with two SMN2 copies and 15 with three SMN2 copies) [7,15].