A Study Evaluating the Effectiveness and Safety of Risdiplam Administered as an Early Intervention in Pediatric Participants With Spinal Muscular Atrophy After Gene Therapy

Inclusion Criteria:

• <2 years of age at the time of informed consent

• Confirmed diagnosis of 5q-autosomal recessive SMA, including genetic confirmation ofhomozygous deletion or compound heterozygosity predictive of loss of function of theSurvival of Motor Neuron 1 (SMN1) gene

• Confirmed presence of two SMN2 gene copies as documented through laboratory testing

• Administration of onasemnogene abeparvovec pre-symptomatically orpost-symptomatically

• Has received onasemnogene abeparvovec for SMA no less than 13 weeks, but not morethan months 30 weeks, prior to enrollment

• If treated with risdiplam prior to onasemnogene abeparvovec, risdiplam treatmentmust not have exceeded 3 weeks and must be discontinued 1 day prior to onasemnogeneabeparvovec administration

• Has, in the opinion of the investigator, not experienced clinically significantdecline in function from the time of onasemnogene abeparvovec administration

Exclusion Criteria:

• Previous or current enrolment in investigational study prior to initiation of studytreatment

• Any unresolved standard-of-care laboratory abnormalities per the onasemnogeneabeparvovec prescribing information

• Concomitant or previous administration of an SMN2-targeting antisenseoligonucleotide

• Concomitant or previous use of an anti-myostatin agent

• Participants requiring invasive ventilation or tracheostomy

• Participants requiring awake non-invasive ventilation or with awake hypoxemia (Arterial Oxygen Saturation [SaO2] <95%) with or without ventilator support

• Presence of feeding tube and an OrSAT score of 0

• Hospitalization for pulmonary event within the last 2 months, or any plannedhospitalization at the time of screening

• Any major illness requiring hospitalization within 1 month before the screeningexamination or any febrile illness within 1 week prior to screening and up to firstdose administration.