Phase IIIb, Open-label, Multi-center Study to Evaluate Safety, Tolerability and Efficacy of OAV101 Administered Intrathecally to Participants With SMA Who Discontinued Treatment With Nusinersen or Risdiplam

During the Screening period and on Day -1 (Baseline), eligibility will be assessed, including confirmation that nusinersen (Spinraza®) or risdiplam (Evrysdi®) have not been used for the defined period (4 month and 15 days prior to Day -1 respectively). On Day - 1 (Baseline) participants will be admitted to the hospital for pre-treatment baseline procedures. Prednisolone (or equivalent) will be given and continued as per the study protocol.

Participants who meet eligibility criteria at Screening and Baseline will receive a single dose of OAV101 (1.2 x 10^14 vector genomes) by lumbar intrathecal injection on Day 1 (Treatment) and will then undergo in-patient safety monitoring atleast the next 48 hours, after which the participant may be discharged according to Investigator judgement.

During Follow-up, safety monitoring will continue as per the visits defined in the Assessment Schedule. Safety for participants enrolled will be evaluated by the study team together with the Data Monitoring Committee (DMC).

Final analysis will be performed after all participants have completed Week 52 or discontinued prior to Week 52. At the end of study, participants will be invited to enroll in a Novartis-sponsored long-term follow-up study to monitor long-term safety and efficacy.