What is ocrelizumab?

Ocrelizumab (Ocrevus) is a prescription medication that targets certain B cells in your body’s immune system. The Food and Drug Administration (FDA) has approved ocrelizumab to treat relapse-remitting multiple sclerosis (RRMS) and primary progressive multiple sclerosis (PPMS).

Its structure is similar to that of rituximab (Rituxan), which is sometimes used as an off-label MS treatment. That means rituximab isn’t FDA-approved for the treatment of MS, but some doctors still use it for this.

Read on to learn more about this new drug and whether it can help with your symptoms.

Ocrelizumab is a type of drug called a monoclonal antibody. This means that it specifically targets one substance. The substance ocrelizumab targets and binds to is called the CD20 protein, which is found on B cells. When ocrelizumab binds to CD20-positive B cells, the B cells burst and die.

This is helpful because experts believe that B cells might play an important role in MS by:

  • activating other immune cells to attack the body’s nerve cells
  • increasing inflammation in the brain and spinal cord

By destroying certain B cells, ocrelizumab helps to reduce inflammation and reduce attacks by your immune system on your nerve cells.

Ocrelizumab offers other benefits as well, depending on the type of MS you have.


A 2016 study compared ocrelizumab to interferon beta-1a (Rebif), another FDA-approved drug for treatment of RRMS.

Compared to interferon beta-1a, ocrelizumab was more effective at:

  • reducing the annual relapse rate
  • slowing disability progression
  • reducing inflammation
  • reducing the size of new and existing brain lesions


Ocrelizumab is the first medication that’s FDA-approved for the treatment of PPMS. During the clinical trial phase, researchers ran a study comparing ocrelizumab to a placebo to see how well it worked for people with PPMS.

The results, which were published in 2016, show that ocrelizumab was more effective than a placebo at:

  • slowing disability progression
  • reducing the size of new and existing brain lesions
  • reducing the risk of declining walking speed
  • reducing loss of brain volume

Ocrelizumab is administered through an infusion, which involves slowly injecting the medication into a vein. This is done in a healthcare facility.

But before administering ocrelizumab, your doctor will want to first make sure that you:

  • don’t have hepatitis B
  • are up-to-date on all of your immunizations at least six weeks before starting treatment
  • don’t have an active infection of any kind

Ocrelizumab can weaken your immune system. This is why your doctor will want to make sure you’re in good health and not at risk of developing any serious conditions before the transfusion.

They may also give you an antihistamine, sometimes with a steroid, to prevent your body from having an infusion reaction. This is a negative reaction that can happen after someone receives an infusion.

You’ll also be monitored for at least an hour after an infusion to ensure that any reaction you do have can be quickly treated.

The recommended dosage of ocrelizumab is the same for both RRMS and PPMS.

You’ll receive the first dose of ocrelizumab in two 300 milligram (mg) infusions spread apart by two weeks. Each infusion will take at least 2.5 hours. For most of this time, you’ll just be sitting, so consider bringing a book to help pass the time.

Your next infusion will happen six months later, followed by another one every six months. During these infusions, you’ll receive 600 mg of ocrelizumab. Due to the larger dose, these sessions will take at least 3.5 hours.

There’s no standard timeline for how long ocrelizumab takes to work. But the 2016 study comparing ocrelizumab to interferon beta-1a (Rebif) found that:

  • slowed disability progression was seen within 12 weeks of treatment
  • reduced size of brain lesions was seen within 24 weeks of treatment
  • decreased annual relapse rate was seen within 96 weeks of treatment

Based on these results, ocrelizumab may start working within a few months, but you might not see the full results for a few years.

Keep in mind that the researchers involved in this study determined beforehand when they would evaluate the study’s participants. So some people may have noticed an improvement sooner.

If you decide to try ocrelizumab, your doctor will regularly check in with you about your symptoms to determine how well the drug is working.

Ocrelizumab is a promising treatment method for RRMS and PPMS, but it does come with some potential side effects, including an infusion reaction. This is a potential side effect of many monoclonal antibodies.

An infusion reaction can become a medical emergency if not treated quickly. Again, this is why you’ll likely be monitored for at least an hour after the infusion. But contact your doctor right away if you notice any of the following symptoms when you get home:

Other possible side effects of ocrelizumab include:

As well, it’s thought that the drug may reactivate the hepatitis B virus, although this hasn’t yet been observed as a side effect.

Ocrelizumab may also be associated with a serious condition called progressive multifocal leukoencephalopathy, which causes:

  • weakness on one side of the body
  • clumsiness
  • visual changes
  • memory changes
  • personality changes

Ocrelizumab may increase the risk of breast cancer. It’s recommended that those taking the drug get screened for breast cancer on a regular basis.

Before trying ocrelizumab, your doctor will go over these potential side effects with you to help you weight the benefits and risks.

Ocrelizumab is a relatively new treatment option for RRMS and PPMS. If you’re looking for a new way to manage MS symptoms, it may be a good option for you.

Ask your doctor about whether you’d be a good candidate for it. They can also walk you through the potential side effects and help you lower your risk of having a bad reaction.