A Study to Evaluate the Safety, Pharmacokinetics, Pharmacodynamics, and Efficacy of RO7268489 as Add-on Therapy to Ocrelizumab, in Participants With Progressive Forms of Multiple Sclerosis (MS)

The main purpose of this study is to assess the efficacy of RO7268489 in adults with progressive multiple sclerosis (PMS) receiving ocrelizumab. After the end of the double-blind period, an open-label (OL) extension may allow eligible participants to receive open-label RO7268489.

Inclusion Criteria: * PMS, in accordance with the revised 2017 McDonald criteria * Expanded disability status scale (EDSS) at screening between 3.0 and 6.0 inclusive Exclusion Criteria: * MS relapse during the 6 months preceding the randomization date * Lack of peripheral venous access * History of alcohol or other drug abuse, in the opinion of the investigator, within 5 years prior to screening * Inability to complete an magnetic resonance imaging (MRI) * Contraindications to ocrelizumab mandatory pre-medications * Treatment with intravenous immunoglobulin (IV Ig) or plasmapheresis within 12 weeks prior to screening