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What is Ocrevus? Your Questions About Ocrelizumab Answered

Ocrevus is Used to Treat Relapsing Multiple Sclerosis & Primary Progressive MS

Ocrevus is a medicine used to treat several relapsing forms of multiple sclerosis (MS), including clinically isolated syndrome, relapse-remitting MS, and active secondary progressive disease. Additionally, it is approved for the treatment of primary progressive MS. Ocrevus contains the active ingredient ocrelizumab. In this article, we answer some of the most common questions about Ocrevus.

The content on this page is provided for informational purposes only. If you have any questions or concerns about your treatment, you should talk to your doctor, pharmacist, or healthcare professional. This is particularly important if you are taking multiple medications or have any existing medical conditions.

  1. What is Ocrevus (ocrelizumab)?
  2. How does Ocrevus (ocrelizumab) work?
  3. What does Ocrevus (ocrelizumab) do for MS?
  4. What are Ocrevus (ocrelizumab) side effects?
  5. How long does Ocrevus (ocrelizumab) take to work?
  6. How is Ocrevus (ocrelizumab) administered?

1. What is Ocrevus (ocrelizumab)?

Ocrevus is the brand name for ocrelizumab, a drug approved for the treatment of relapsing forms of multiple sclerosis (MS) and primary progressive MS. It was approved by the FDA (in the US) and EMA (in the EU) in 2017, along with several other markets around the world.

Ocrevus is administered through an intravenous infusion, meaning it is slowly injected into a vein, which is carried out by a healthcare professional. Infusions are given once every 6 months, with the very first dose being split into two infusions that are given two weeks apart.

The active ingredient in Ocrevus, ocrelizumab, is a monoclonal antibody, meaning it is a laboratory-produced agent that mimics natural antibodies created by your immune system. Ocrevus is designed to specifically target an antigen that has been linked to the progression of multiple sclerosis. By doing so, and by destroying the cells on which the antigen is found, Ocrevus is believed to reduce demyelination and slow disease progression.

2. How does Ocrevus (ocrelizumab) work?

Although the exact way Ocrevus works is not known, its active ingredient is a monoclonal antibody called ocrelizumab. Monoclonal antibodies are laboratory-produced molecules that mimic natural antibodies produced by your immune system. Monoclonal antibodies are designed to target specific antigens (molecules that stimulate an immune response) depending on the desired therapeutic effect.

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Ocrevus is designed to bind to an antigen called CD20, which is present on specific B cells (a type of white blood cell). The specific role of these B cells in multiple sclerosis is not entirely known, but researchers have found that they may be as significant in disease progression as T cells (another type of white blood cell that has long been linked to MS).

Ocrevus destroys the CD20+ cells to which it binds, which is believed to reduce the damage done to myelin (demyelination).

3. What does Ocrevus (ocrelizumab) do for MS?

Ocrevus is approved for the treatment of both relapsing forms of multiple sclerosis and primary progressive, with clinical trials demonstrating its efficacy for both.

Ocrevus (ocrelizumab) for relapsing MS

Ocrevus was compared to another drug for relapsing forms of multiple sclerosis called Rebif, the active ingredient of which is interferon beta-1a. You can read about Rebif here: Interferon Beta-1a (Rebif & Avonex): Your Most Common Questions

The drugs were compared in two large, identical clinical trials studying 1656 people living with MS.

In both studies, Ocrevus was found to be more effective at reducing the number of relapses than Rebif. In study 1, 83% of people taking Ocrevus had no relapses in two years, while in study 2 that figure was 82%.

Furthermore, Ocrevus proved effective at reducing disability progression; 9.8% of participants had disability progression in two years (based on the Expanded Disability Status Scale).

Ocrevus also had positive results in reducing brain lesions, while 48% of participants in each study showed no evidence of disease activity. You can read more about the studies here: Ocrevus for relapsing forms of MS.

Ocrevus (ocrelizumab) for primary progressive MS

Ocrevus is (at the time of writing) the only drug approved by the FDA to treat primary progressive multiple sclerosis (PPMS).

Ocrevus was compared to a placebo (a substance that has no active ingredient) in a trial of 732 people living with PPMS.

People taking Ocrevus were 24% less likely to have disability progression (based on the Expanded Disability Status Scale) compared to people taking the placebo and disability progression was delayed. Similarly, those taking Ocrevus were 25% less likely to slow down on a time walking speed test than those taking the placebo (49% compared to 59%).

You can read more about the study here: Ocrevus for primary progressive MS.

4. What are Ocrevus (ocrelizumab) side effects?

Ocrevus can cause side effects including:

  • Infusion reactions
  • Increased risk of infections
  • Risk of malignancies including breast cancer

Infusion reactions

These most common side effects caused by Ocrevus are infusion reactions, including:

  • Itchy skin
  • Rash
  • Hives
  • Tiredness
  • Coughing or wheezing
  • Trouble breathing
  • Throat irritation or pain
  • Feeling faint
  • Fever
  • Redness on your face (flushing)
  • Nausea
  • Headache
  • Swelling of the throat
  • Dizziness
  • Shortness of breath
  • Fatigue
  • Fast heartbeat

It’s customary for you to be premedicated with corticosteroids and antihistamines to reduce the risk and severity of infusion reactions. Nonetheless, up to 40% of people receiving Ocrevus experienced infusion reactions, particularly after the first infusion. In clinical trials, most infusion reactions were mild to moderate; 0.3% of infusion reactions were serious, some of which required hospitalization.

Your healthcare provider will usually observe you for at least one hour after the completion of each infusion for signs of infusion reactions. However, they can occur up to 24 hours after the infusion, so you should contact your healthcare provider right away if you experience any of the previously mentioned side effects after your infusion.

Increased risk of infection

Because it acts on your immune system, Ocrevus increases your risk of infections, including upper respiratory tract infections, lower respiratory tract infections, skin infections, and herpes-related infections.

You should tell your healthcare provider if you have signs of infection, including:

  • Fever
  • Chills
  • Persistent cough

Signs of herpes include:

  • Cold sores
  • Shingles
  • Genital sores

More serious signs of herpes infections include:

  • Persistent headache
  • Confusion
  • Change in vision
  • Eye redness
  • Eye pain

Your healthcare provider will also do a blood test to check for hepatitis B before you begin taking this medication. If you’ve ever had hepatitis B, anti-CD20 drugs, such as Ocrevus, may reactivate the virus.

Ocrevus may also increase the risk of a serious opportunistic viral infection of the brain called progressive multifocal leukoencephalopathy (PML), which has been linked to other anti-CD20 and MS medications. Although PML is rare and usually only occurs in people with a weakened immune system, you should contact your healthcare provider immediately if you experience new or worsening neurologic signs and symptoms, including:

  • Problems thinking, balance, or eyesight
  • Weakness on one side of your body
  • Lack of strength or problems using your arms or legs

Risk of malignancies including breast cancer

In clinical trials, six of 781 females taking Ocrevus were diagnosed with breast cancer while there were no cases among 668 women taking Rebif or a placebo, suggesting Ocrevus might increase the risk.

It is therefore recommended that women taking Ocrevus follow breast cancer screening guidelines, such as those provided by the American Cancer Society.

This is not a complete list of the possible side effects of Ocrevus. It is important to speak to your healthcare provider to gain information about the risk of side effects and steps you can take to help prevent or control them. Furthermore, Ocrevus is a relatively new drug to the market (having been first approved in 2017), so previously unknown risks may emerge in post-market surveillance.

5. How long does Ocrevus (ocrelizumab) take to work?

There is no defined length of time that it takes for Ocrevus to work. However, researchers did make observations at defined moments in time during the phase 3 trials that compared Ocrevus to Rebif. Observations included:

  • After 12 and 24 weeks, the percentage of patients with disability progression was reduced
  • Reduced brain lesions in people taking Ocrevus were observed after 24, 48, and 96 weeks
  • Among patients with relapsing MS, disease activity and progression were lower over a period of 96 weeks

This suggests that Ocrevus begins working within 12 weeks of the first dose.

6. How is Ocrevus (ocrelizumab) administered?

Ocrevus (ocrelizumab) is given as an intravenous infusion, meaning it is slowly injected into your veins.

The first infusion is split into two separate infusions (each of 300mg) that are given two weeks apart, each of which usually lasts around 2.5 hours.

All future doses (of 600mg) are given in one infusion every six months, with each infusion usually lasting around 3.5 hours. Infusions can take longer if reactions occur. Your healthcare team will monitor you throughout the infusion and help make sure you are comfortable.

Prior to receiving your infusion, your healthcare provider will perform a checkup that includes checking for active infections and checking your vital signs. You will usually be given medications that help reduce the risk and severity of infusions reactions, such as corticosteroids and antihistamines, 30-60 minutes before the infusion.

After receiving the infusion, your healthcare team will monitor you for at least an hour and check for any signs of infusion reactions. It is important to be aware that reactions can occur for up to 24 hours after the infusion. Check question 4, What are Ocrevus (ocrelizumab) side effects?, for more information about infusion reactions.

As of May 2020, a shorter infusion time of 2 hours was approved for use in Europe by the EMA. At the time of writing, the FDA is still reviewing the application for the two-hour infusion and is expected to decide whether or not to approve it by December 2020.


The content on this page is provided for informational purposes only. If you have any questions or concerns about your treatment, you should talk to your doctor, pharmacist, or healthcare professional. This is particularly important if you are taking multiple medications or have any existing medical conditions.

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  • Keep track of your Ocrevus infusion appointments
  • Track symptoms and side effects
  • Health report you can share with your MS healthcare team

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