Ocrelizumab is the first treatment to be licensed for Primary Progressive MS (PPMS), and also can be used to treat relapsing remitting MS (RRMS).  It acts by targeting a marker (CD20) on a type of white blood cell (B cell) thought to be involved in the abnormal immune response that attacks the myelin coating of nerve cells.  

In both forms of the disease, it is given as an intravenous infusion, initially split over 2 weeks, and then every 6 months.

Ocrelizumab infographic

Ocrelizumab in clinical trials

In clinical trials for PPMS, the group taking Ocrelizumab reduced the chance of worsening disability after 12 weeks by approximately one quarter (24%), compared with those taking a placebo.  Whilst this may not sound like a huge difference, it is the first medication ever to show a statistically significant improvement in PPMS outcomes, and it would be very interesting to see how these improvements will be borne out over the longer-term.

After 2 years of treatment, walking speed had slowed less in the treatment group than the placebo group.  There were also less brain lesions and brain shrinkage in the treatment group.

Ocrelizumab prescribing in PPMS is very dependent on location, and in the U.K. is not currently approved, due to early cost-benefit analysis.  The European Medicines Agency (EMA) has mandated it use in “early primary progressive MS, defined as people who have had symptoms of MS for 15 years or less, have an EDSS of 3.0 to 6.5 and evidence of MS activity on MRI scans​”.

When used to treat RRMS, Ocrelizumab reduced the number of relapses by 50% compared to beta-interferon and 70% compared to placebo, reduced disability progression sustained for 3 and 6 months, and significantly reduced the number of lesions seen on MRI scans compared to beta interferon. 

Brain volume loss was reduced and there were more people with no evidence of disease activity (NEDA) in the ocrelizumab treatment groups compared to beta-interferon.  

Side effects

It is generally very well-tolerated and no unexpected side effects were reported in the phase III trials.

That said, it is not without risks, and these typically include:

  • Infusion site reactions

  • Chest infections

  • Cold sores and shingles (herpes infections)

  • Opportunistic infections (caused by bacteria or viruses normally kept under control by the immune system)

  • Potentially increased risks of some cancers, as yet not confirmed and being closely monitored

All of these side effects will be monitored closely as the use of Ocrelizumab becomes more wide-spread.  

Our website also has some information on a recent piece of research comparing Ocrevus to the other disease modifying drugs (DMDs) in terms of effectiveness and side effects.

Can Ocrelizumab affect conception and pregnancy?

Pregnancy is not recommended during treatment with Ocrevus.  If you are planning to start a family you should discuss this with your MS team.  Women of child-bearing age should use an effective method of contraception during treatment and for 12 months after stopping Ocrevus.  Breastfeeding is currently not recommended.

Page last updated 03 May 2019


  1. JAMA Neurol. 2019 Feb 18. doi: 10.1001/jamaneurol.2018.4905.
  2. https://doi.org/10.1016/j.msard.2018.12.040
  3. https://www.mstrust.org.uk/a-z/ocrelizumab-ocrevus