Risdiplam in Presymptomatic Spinal Muscular Atrophy

BACKGROUND: Risdiplam, an oral pre-messenger RNA splicing modifier, is an efficacious treatment for persons with symptomatic spinal muscular atrophy (SMA). The safety and efficacy of risdiplam in presymptomatic disease are unclear. METHODS: copies who are untreated would have a severe SMA phenotype (type 1), would never sit independently, would receive permanent ventilation and feeding support, or would die by 13 months of age. Secondary outcomes that were assessed over a period of 24 months included survival, ventilatory support, motor milestones, the development of clinically manifested SMA, feeding, and growth. RESULTS: copies and a baseline ulnar CMAP amplitude of at least 1.5 mV were able to sit without support for at least 5 seconds. Three infants were withdrawn from the study by a parent or caregiver after the month 12 visit. Of 23 infants who completed 24 months of treatment, all were alive without the use of permanent ventilation or feeding support. Over a period of 24 months, nine treatment-related adverse events were reported in 7 infants; none of these events were serious. CONCLUSIONS: Infants up to 6 weeks of age with genetically diagnosed SMA who were treated with risdiplam before the development of clinical signs or symptoms appeared to have better functional and survival outcomes at 12 and 24 months than untreated infants in natural history studies. Larger, controlled studies with longer follow-up are needed to further understand the relative efficacy and safety of presymptomatic treatment of SMA with risdiplam. (Funded by F. Hoffmann-La Roche; RAINBOWFISH ClinicalTrials.gov number, NCT03779334.).