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 (HINALEA 2)

Inclusion Criteria: <2 years of age at the time of informed consent Confirmed diagnosis of 5q-autosomal recessive SMA Confirmed presence of two SMN2 gene copies Administration of onasemnogene abeparvovec pre-symptomatically or post-symptomatically Has received onasemnogene abeparvovec for SMA no less than 3 months prior to enrollment In the opinion of the investigator, has demonstrated a plateau or decline in function post-gene therapy (with a duration of 6 months or less) documented by 2 individual time points in the functions as follows: swallowing AND one additional function/ability (respiratory, motor function, other) per appropriate expectation. Exclusion Criteria: Treatment with investigational therapy prior to initiation of study treatment Any unresolved standard-of-care laboratory abnormalities per the onasemnogene abeparvovec prescribing information Concomitant or previous administration of a SMN2-targeting antisense oligonucleotide or SMN2 splicing modifier either in a clinical study or as part of medical care 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 planned hospitalization at the time of screening Any major illness requiring hospitalization within 1 month before the screening examination or any febrile illness within 1 week prior to screening and up to first dose administration.