A Study Evaluating the Effectiveness and Safety of Risdiplam Administered in Pediatric Patients With Spinal Muscular Atrophy Who Experienced a Plateau or Decline in Function 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 prior toenrollment

• 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.

• In the opinion of the investigator, has demonstrated a plateau or decline infunction post-gene therapy (with a duration of 26 weeks or less) documented by 2individual time points in the functions as follows: swallowing AND one additionalfunction/ability (respiratory, motor function, other) per appropriate expectation.

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

• 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.