Spinal Muscular Atrophy (SMA) is a genetic condition that affects muscles, making them weak. In this study, doctors are testing a medicine called risdiplam as an early treatment for young children under 2 years old who have SMA and have 2 copies of a specific gene called SMN2. These children have already received a gene therapy called onasemnogene abeparvovec which is given to help their muscles before or after symptoms start showing.

The study is open-label, meaning everyone knows what treatment is given, and single-arm, meaning all participants get the same treatment. To join, children must have had the gene therapy 3-7 months before starting this study. They should not have any serious new symptoms after the gene therapy.

• The study is for children under 2 years old.
• They must have already had gene therapy (onasemnogene abeparvovec).
• Participants should not have serious breathing or feeding issues.