Multiple Sclerosis Society of Canada



  • Brand name: Ocrevus (Genentech/Roche)
  • Route of Administration: Intravenous infusion (every 6 months)
  • Type: Humanized monoclonal antibody
  • Emerging treatment for: RRMS and progressive MS
  • Status: In Phase III of clinical trials

Ocrelizumab is believed to influence the immune system response by binding to CD20 on the surface of B cells, leading to cell lysis (breaking down of a cell).

How it Works

Ocrelizumab is the humanized form of Rituximab, a mouse antibody to CD20 that has been met with some success in the treatment of RRMS. The humanized ocrelizumab is expected to be less immunogenic and therefore less likely to cause infusion reactions.

B cells are believed to be involved in the abnormal immune response in MS. Ocrelizumab is thought to influence the immune system response in MS through its involvement with B cells. Ocrelizumab binds to CD20, found on the surface of B cells, and causes cell lysis leading to a dose-dependent depletion of B cells.

Research and Results

A phase II trial conducted by Dr. Ludwig Kappos and team was conducted in RRMS patients spanning 24 weeks. Participants received either placebo, low dose (600mg) ocrelizumab, high dose (2000mg) ocrelizumab, or interferon beta-1a treatment (an approved treatment for MS). At the end of the 24 weeks participants in both ocrelizumab groups had lower numbers of active brain lesions compared to the placebo group (89% lower in low dose ocrelizumab group and 96% lower in high dose ocrelizumab group). Both ocrelizumab groups were better than the interferon beta-1a group for reducing active lesions. Annualized relapse rates over the 24 weeks were 80% lower in the low dose ocrelizumab group and 73% lower in the high dose ocrelizumab group compared to the placebo group. Findings also showed that both doses of ocrelizumab were effective in reducing MRI and clinical disease activity.

Currently, two phase III studies (OPERA I: NCT01412333; OPERA II: NCT01247324) are ongoing to explore the effect of ocrelizumab treatment (600mg every 24 weeks) compared to interferon beta-1a treatment over 96 weeks (two years) on several clinical outcomes on patients with RRMS and secondary progressive MS with relapses. A total of 1,656 participants are enrolled in both trials across 40 countries. Preliminary results show that ocrelizumab significantly reduced the annualized relapse rate during the two-year period compared to interferon beta-1a, thus meeting its primary endpoint. Ocrelizumab also reduced the progression of clinical disability, as measured by the Expanded Disability Status Scale (EDSS) and reduced the number of brain lesions.

Adverse Effects Reported

In clinical trials, serious adverse effects were reported to be rare. More people administered ocrelizumab had infusion-related adverse events compared to those in the placebo group at first infusion. Of note, one patient taking ocrelizumab (2000mg) died as a result of brain edema following a systemic inflammatory response with multi-organ failure. The connection between this death and ocrelizumab is unclear.


Kappos L et al. Ocrelizumab in relapsing-remitting multiple sclerosis: a phase 2, randomised, placebo-controlled, multicentre trial. Lancet. 2011; 378 1779-87.