Key Inclusion Criteria:  The participant is diagnosed with possible or probable MSA of the multiple system atrophy parkinsonian type (MSA-P) or multiple system atrophy cerebellar type (MSA-C) sub-type at the Screening Visit. The participant had onset of motor and/or autonomic (orthostatic or urinary) MSA symptoms within 5 years prior to the Screening Visit in the judgement of the investigator. The participant has an UMSARS Part I score ≤16 (omitting question 11 on sexual function) at the Screening Visit. The participant has a cognitive performance evaluated by the Montreal Cognitive Assessment (MoCA) with a score ≥22 at the Screening Visit.  Key Exclusion Criteria:  The participant has been treated with an anti-α-synuclein monoclonal antibody, mesenchymal stem cells or an inhibitor of α-synuclein aggregation within the last 12 months. The participant has any past or current treatment with an active vaccine targeting α-synuclein. The participant has 2 or more blood relatives with a history of MSA. The participant has evidence (clinically or on MRI) and/or history of any clinically significant disease or condition other than MSA (for example, serious neurological disorder, other intracranial disease, or systemic disease). The participant has a current diagnosis of movement disorders that could mimic MSA (for example, Parkinson' disease, dementia with Lewy bodies, essential tremor, progressive supranuclear palsy, spinocerebellar ataxia, spastic paraparesis, corticobasal degeneration, or vascular, pharmacological, or post-encephalitic parkinsonism), per investigator discretion.  Other inclusion and exclusion criteria may apply.