A Study of Ocrelizumab Administered Subcutaneously in Participants With Multiple Sclerosis Who Switch From an Approved Anti-CD20 Therapy

Inclusion Criteria: * Diagnosis of RMS or PPMS according to the revised McDonald 2017 criteria * Documented Expanded Disability Status Scale (EDSS) score of 0-6.5, inclusive, at screening (or within 6 months of screening) * Participants discontinuing aCD20 therapy for reasons including, but not limited to, physician/participant preference, access to commercial drug (e.g., insurance coverage issues), or other logistical reasons (such as geographical relocation, travel, etc.) are eligible for this study * Prior treatment with ofatumumab SC, ublituximab-xiiy IV, or ocrelizumab IV aCD20 therapy Exclusion Criteria: * Participants who have demonstrated suboptimal response to aCD20 therapy * Discontinuing aCD20 therapy because of any of the following treatment emergent adverse events (TEAEs): 1) Grade ≥3 severe infusion-related reaction (IRRs) or injection reactions (IRs); 2) Recurrent Grade ≥3 infections, or the need for ≥2 courses of antibiotics after starting aCD20 therapy, if the investigator believes infection is related to therapy * Participants with contraindication to Gd+ and participants who for any reason cannot tolerate MRI procedure * Known presence of active, recurrent, or chronic infection (e.g., human immunodeficiency virus \[HIV\], syphilis, human papillomavirus \[HPV\], tuberculosis \[TB\]) * History of confirmed or suspected progressive multifocal leukoencephalopathy (PML) * Known presence of neurologic disorders that may interfere with the diagnosis of RMS or PPMS * Any concomitant disease that may require treatment with systemic corticosteroids (e.g., mineralocorticoids and glucocorticoids) or immunosuppressants during the study * Known allergy or hypersensitivity to ocrelizumab, rHuPH20, or excipients of the OCR SC formulation * Any previous treatment with bone marrow transplantation and hematopoietic stem cell transplantation * Treatment with any live-attenuated vaccine within 6 weeks prior to baseline * Treatment with any experimental procedures for RMS or PPMS (e.g., treatment for chronic cerebrospinal venous insufficiency) * Previous treatment with cladribine, atacicept, alemtuzumab or mitoxantrone * Positive hepatitis B virus (HBV) and hepatitis C virus (HCV) antibody test at screening Other protocol defined inclusion and exclusion criteria may apply.