Efficacy and Safety of Intrathecal OAV101 (AVXS-101) in Pediatric Patients With Type 2 Spinal Muscular Atrophy (SMA)

Eligible participants received a single administration of OAV101B at the dose of 1.2 x 10\^14 vector genomes intrathecally or the sham procedure on Day 1 (Treatment Period 1), and were followed for a period of 52 weeks for Period 1. In Period 2, participants who received the sham treatment in Period 1 were administered OAV101B, and participants who received OAV101B in Period 1 underwent the sham procedure. Participants were followed up for 12 weeks in Period 2. The study consisted of a Screening and Baseline Period followed by two Treatment and Follow-up Periods. Participants were admitted to the hospital on Day 1 (or Day -1 as per local standards of care). After receiving OAV101B or the sham procedure on Day 1, participants underwent in-patient safety monitoring through Day 2 and optionally for Day 3. After Period 1, eligible participants could continue to Period 2 subsequently entering Period 2 in a rolling seamless fashion as participants completed Follow-up Period 1. In Treatment Period 2, eligible participants who received a sham procedure on Study Day 1 of Treatment Period 1 were hospitalized to receive OAV101B on Week 52 + 1 day and participants who received OAV101B on Study Day 1 of Treatment Period 1 were hospitalized to receive a sham procedure on the Week 52 + 1 Day. The total duration of the study including both Period 1 and Period 2 was 64 weeks. At the end of the study, all participants who received OAV101B were eligible to enroll in a long-term follow-up study to monitor long-term safety and efficacy. Approximately 125 participants were planned to be randomized in a 3:2 ratio to receive OAV101B (N= \~75) or a sham procedure (N= \~50). The unequal randomization ratio allowed more participants to receive active treatment in Period 1. It was anticipated that approximately 65 randomized participants would be aged 2 to \<5 years and approximately 60 randomized participants would be aged 5 to \<18 years.