A Study to Evaluate the Efficacy, Safety, Pharmacokinetics, and Pharmacodynamics of Ocrelizumab in Participants With Relapsing Multiple Sclerosis and Primary Progressive Multiple Sclerosis

The main purpose of this study is to evaluate the efficacy of ocrelizumab in participants with relapsing multiple sclerosis (RMS) and to characterize the ocrelizumab pharmacodynamic (PD) profile in Chinese participants with primary progressive multiple sclerosis (PPMS).

Inclusion Criteria: * Diagnosis of RMS/PPMS in accordance with the revised 2017 McDonald Criteria * EDSS score from 0-5.5 (RMS) or 3.0-6.5 (PPMS), inclusive, at screening and baseline * Documented MRI of brain with abnormalities consistent with MS before screening Exclusion Criteria: * Diagnosis of PPMS or non-active secondary progressive multiple sclerosis (SPMS) (only for RMS cohort) * History of relapsing remitting multiple sclerosis (RRMS) or SPMS at screening (only for PPMS cohort) * Disease duration of more than 10 years in participants with an EDSS ≤ 2.0 at screening (only for RMS cohort) * History of confirmed or suspected progressive multifocal leukoencephalopathy (PML) * Inability to complete an MRI scan or contraindication to Gd administration * Contraindications to mandatory pre-medications (i.e., corticosteroids and antihistamines) * Known presence of other neurologic disorders if they could interfere with the diagnosis of MS or assessments of efficacy and/or safety during the study * Any concomitant disease that may require chronic treatment with systemic corticosteroids or immunosuppressants during the course of the study * Known history of human immunodeficiency virus (HIV) infection * Lack of peripheral venous access * Previous treatment with B-cell targeted therapies (i.e., rituximab, ocrelizumab, atacicept, belimumab, or ofatumumab), unless the last infusion was at least 6 months prior to screening * Positive screening tests for hepatitis B virus (HBV) and/or hepatitis C virus (HCV)