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

Inclusion Criteria:

General Inclusion Criteria:

- 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

Inclusion Criteria Specific to RMS Participants:

- 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

Inclusion Criteria Specific to RMS Cohort Arm 4 Participants:

- Must meet inclusion criteria for the RMS cohort

- Separate signed Informed Consent Form for the RMS Delayed Time to Start Control Arm
(Arm 4)

- Must be willing to remain on the same dose and regimen of current standard of care, or
no treatment if treatment-naïve, for 12 weeks after study enrollment The treating
and/or study physician must agree that the participant is eligible to remain on the
same dose and regimen of their current standard of care at Screening, or to receive no
treatment if the participant is treatment-naïve, for 12 weeks after study enrollment

Inclusion Criteria Specific to PPMS Participants:

- Diagnosis of PPMS in accordance with the 2010 revised McDonald criteria

- EDSS score of 3.0 - 6.5 points, inclusive, at Screening

- Disease duration from the onset of multiple sclerosis symptoms <10 years in
participants with an EDSS at Screening less than or equal to (
- Documented history of either elevated immunoglobulin G (IgG) Index or one or more IgG
oligoclonal bands (OCBs) detected by isoelectric focusing

Exclusion Criteria:

- Diagnosis of secondary progressive multiple sclerosis 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 multiple sclerosis (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

Exclusion Criteria Specific to RMS Participants:

Diagnosis of PPMS or secondary progressive multiple sclerosis without relapses