A Study to Investigate the Safety, Tolerability, and Processing by the Body of Intravenous and Subcutaneous RO7121932 Administration in Participants With Multiple Sclerosis

Inclusion Criteria: * Expanded Disability Status Scale (EDSS) score ≤7.0 at Screening * Participants with relapsing multiple sclerosis (RMS) or progressive multiple sclerosis (PMS) who fulfil international panel criteria for diagnosis (McDonald 2017 criteria) * Participants not treated with any approved MS treatment at Screening and not planning to start on any MS therapy during the study (including follow-up) * Biological male and female participants * Female participants must practice abstinence or otherwise use contraception Exclusion Criteria: * Evidence of clinical disease activity as defined by any clinical relapse within 3 months prior to screening, or by \>1 clinical relapse within 12 months prior to screening * Evidence of brain magnetic resonance imaging (MRI) activity as defined by the presence of ≥ 1 Gadolinium (Gd)-enhancing T1 lesion in the screening MRI scan or by ≥ 4 new or enlarging T2 lesions in the screening scan as compared to a reference scan * Participants who have active progressive multifocal leukoencephalopathy (PML), have had confirmed PML, or have a high degree of suspicion for PML * Known presence of other neurological disorders that may mimic MS including but not limited to: neuromyelitis optica spectrum disease, Lyme disease, untreated Vitamin B12 deficiency, neurosarcoidosis, cerebrovascular disorders, and untreated hypothyroidism * Known active or uncontrolled bacterial, viral, fungal, mycobacterial infection or other infection, excluding fu…