A Study to Investigate the Safety, Tolerability, Pharmacokinetics, Pharmacodynamics and Efficacy of Risdiplam (RO7034067) in Type 2 and 3 Spinal Muscular Atrophy (SMA) Participants

Inclusion Criteria: * Confirmed diagnosis of 5q-autosomal recessive SMA * Negative blood pregnancy test at screening and agreement to comply with measures to prevent pregnancy and restrictions on sperm donation * For Part 1: Type 2 or 3 SMA ambulant or non-ambulant * For Part 2: 1) Type 2 or 3 SMA non-ambulant; 2) RULM entry item A greater than or equal to 2; 3) ability to sit independently as assessed by item 9 of the MFM Exclusion Criteria: * Concomitant or previous participation in any investigational drug or device study within 90 days prior to screening, or 5 half-lives of the drug, whichever is longer * Concomitant or previous administration of a SMN2-targeting antisense oligonucleotide, SMN2 splicing modifier or gene therapy either in a clinical study or as part of medical care * Any history of cell therapy * Hospitalization for a pulmonary event within the last 2 months or planned at time of screening * Surgery for scoliosis or hip fixation in the one year preceding screening or planned within the next 18 months * Unstable gastrointestinal, renal, hepatic, endocrine, or cardiovascular system diseases as considered to be clinically significant by the Investigator * Presence of clinically significant electrocardiogram abnormalities before study drug administration from average of triplicate measurement or cardiovascular disease indicating a safety risk for participants as determined by the Investigator * Any major illness within one month before the screening examina…