A Study to Evaluate the Efficacy and Safety of Ocrelizumab in Adults With Primary Progressive Multiple Sclerosis

The screening phase will last up to 24 weeks. In the double-blind treatment phase, participants will undergo at least 144 weeks of study treatment. Study drug (ocrelizumab or placebo) will be administered every 24 weeks. All participants who discontinue prematurely from the double-blind treatment phase will enter the FU1 phase, including participants receiving other immunomodulatory or immunosuppressive treatment(s) for MS, commercial ocrelizumab, or no treatment. The FU1 phase will run in parallel with the double-blind treatment phase for 144 weeks or until the primary analysis is performed, whichever occurs first. An optional OLE phase is planned for eligible participants who either have either completed 144 weeks of the double-blind treatment phase or are ongoing in the double-blind treatment phase at the time of the primary analysis and, in the opinion of the investigator, could benefit from ocrelizumab treatment. The following participants will move into the FU2 phase: participants who are ongoing in the FU1 at 144 weeks from randomization or at the time of the primary analysis; participants who have either completed 144 weeks of the double-blind treatment phase or are ongoing in the double-blind treatment phase at the time of the primary analysis and will not enter the OLE phase; participants who have completed or withdrawn from the OLE phase or from PDP OCR treatment phase.