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:

- For Part 1: Type 2 or 3 SMA ambulant or non-ambulant. For Part 2: Type 2 or 3 SMA
non-ambulant

- Confirmed diagnosis of 5q-autosomal recessive SMA For Part 2: 1) RULM entry item A
greater than or equal to [>=] 2; 2) ability to sit independently as assessed by item 9
of the MFM

- Negative blood pregnancy test at screening and agreement to comply with measures to
prevent pregnancy and restrictions on sperm donation

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 examination or any febrile
illness within one week prior to screening and up to first dose administration

- Recently initiated treatment (within less than [<] 6 months prior to randomization)
with oral salbutamol or another beta 2-adrenergic agonist taken orally

- Any prior use of chloroquine, hydroxychloroquine, retigabin, vigabatrin or
thioridazine, is not allowed

- Ascertained or presumptive hypersensitivity (e.g., anaphylactic reaction) to Risdiplam
or to the constituents of its formulation

- Recent history (less than one year) of ophthalmological diseases

- Participants requiring invasive ventilation or tracheostomy