Study to Explore the Mechanism of Action of Ocrelizumab and B-Cell Biology in Participants With Relapsing Multiple Sclerosis (RMS)

This is an open-label, multicenter, biomarker study designed to be hypothesis-generating in order to better understand the mechanism of action of ocrelizumab and B-cell biology in RMS. The dose level of ocrelizumab administered in this study is 600 mg.

Inclusion Criteria:

• Diagnosis of RMS in accordance with the 2010 revised McDonald criteria
• Expanded Disability Status Scale (EDSS) score of 0 to 5.5 points, inclusive, at Screening
• Disease duration from the onset of multiple sclerosis symptoms less than (<) 15 years in participants with an EDSS score greater than (>) 5.0 at Screening
• Either treatment-naive or receiving treatment with disease-modifying therapies, including prior use of interferon (IFN)-beta-1a (Avonex®, Rebif®), IFN-beta-1b (Betaseron®/Betaferon), or glatiramer acetate (Copaxone®).
• At least one clinically documented relapse in the past year and/or at least one T1-weighted Gadolinium (Gd)-enhancing lesion in the past year and/or at least one new T2 lesion in the past year at the time of enrollment
• For women of childbearing potential: agreement to remain abstinent (refrain from heterosexual intercourse) or use contraceptive methods that result in a failure rate of <1 percent (%) per year during the treatment period and for at least 24 weeks after the last dose of study treatment or until their B-cells have repleted, whichever is longer

Exclusion Criteria:

• Diagnosis of primary progressive multiple sclerosis (PPMS)
• Diagnosis of secondary progressive multiple sclerosis (MS) without relapses for at least 1 year
• History or known presence of recurrent or chronic infection (human immunodeficiency virus [HIV], syphilis, tuberculosis)
• History of cancer, including solid tumors and hematological malignancies (except basal cell, in situ squamous cell carcinomas of the skin, and in situ carcinoma of the cervix of the uterus that have been excised and resolved with documented clean margins on pathology)
• Known presence or history of other neurologic disorders
• Contraindications or intolerance to oral or IV corticosteroids, including IV methylprednisolone, according to the country label
• Contraindication for LP
• Previous treatment with B cell-targeted therapies (such as rituximab, ocrelizumab, atacicept, belimumab, or ofatumumab)
• Previous treatment with natalizumab/Tysabri®, alemtuzumab, anti-CD4 agents, cladribine, teriflunomide, cyclophosphamide, mitoxantrone, azathioprine, mycophenolate mofetil, cyclosporine, methotrexate, total body irradiation, or bone marrow transplantation
• Treatment with fingolimod/Gilenya®, dimethyl fumarate/Tecfidera®, or similar treatment within 6 months prior to enrollment
• Systemic corticosteroid therapy within 4 weeks prior to Baseline
• Previous or concurrent treatment with any investigational agent or treatment with any experimental procedure for MS (such as treatment for chronic cerebrospinal venous insufficiency)
• Certain laboratory abnormalities or findings at Screening
• Pregnant or lactating, or intending to become pregnant during the study