A Study of Multiple Doses of Nusinersen (ISIS 396443) Delivered to Infants With Genetically Diagnosed and Presymptomatic Spinal Muscular Atrophy

The primary objective of the study is to examine the efficacy of multiple doses of Nusinersen administered intrathecally in preventing or delaying the need for respiratory intervention or death in infants with genetically diagnosed and presymptomatic spinal muscular atrophy (SMA). Secondary objectives of this study are to examine the effects of Nusinersen in infants with genetically diagnosed and presymptomatic SMA.