A Phase 3, Randomized, Double-blind, Sham-Procedure Controlled Study to Assess the Clinical Efficacy and Safety of ISIS 396443 Administered Intrathecally in Patients With Later-onset Spinal Muscular Atrophy

The primary objective of this study is to examine the clinical efficacy of nusinersen (ISIS 396443) administered intrathecally to participants with later-onset Spinal Muscular Atrophy (SMA). The secondary objective is to examine the safety and tolerability of nusinersen administered intrathecally to participants with later-onset SMA.