Ocrevus (Ocrelizumab)

What Is Ocrevus and What Is It Used For?

Ocrevus contains the active substance ocrelizumab, a type of protein known as a humanized monoclonal antibody. Monoclonal antibodies are engineered proteins designed to recognize and attach to specific targets in the body. In the case of ocrelizumab, the target is a protein called CD20, which is found on the surface of certain B lymphocytes (B cells) — a type of white blood cell that plays a key role in the immune system.

Ocrevus is used to treat adults with two forms of multiple sclerosis (MS). The first is relapsing multiple sclerosis (RMS), which includes relapsing-remitting MS and active secondary progressive MS. The second is early primary progressive multiple sclerosis (PPMS), a form where symptoms gradually worsen from the onset of the disease. Ocrevus was the first therapy ever approved specifically for PPMS, marking a significant milestone in MS treatment.

Understanding Multiple Sclerosis

Multiple sclerosis is a chronic autoimmune disease that affects the central nervous system, specifically the brain and spinal cord. In MS, the immune system mistakenly attacks the protective coating around nerve fibers called the myelin sheath. This process, known as demyelination, causes inflammation and disrupts nerve signal transmission. Over time, the damage can lead to a wide range of symptoms including difficulty walking, impaired balance, numbness, weakness, double vision, coordination problems, and bladder dysfunction.

In relapsing MS, patients experience episodes of new or worsening symptoms (called relapses or flare-ups) followed by periods of partial or complete recovery. However, nerve damage accumulates over time and may cause permanent disability. In primary progressive MS, symptoms steadily worsen from the beginning without distinct relapses. PPMS affects approximately 10–15% of people diagnosed with MS and typically presents later in life.

How Does Ocrevus Work?

Ocrevus works by selectively targeting and binding to CD20-positive B cells, which are a subset of immune cells that contribute to the inflammatory process in MS. When ocrelizumab attaches to CD20 on the surface of these B cells, it triggers a process that leads to their removal from the body through antibody-dependent cellular cytolysis (ADCC) and complement-dependent cytolysis (CDC).

By depleting these specific B cells, Ocrevus reduces the inflammatory attacks on the myelin sheath, decreasing the frequency and severity of relapses in RMS and slowing the progression of disability in both RMS and PPMS. Importantly, Ocrevus does not target all B cells — it preserves pre-existing humoral immunity and allows for eventual B-cell reconstitution after treatment discontinuation.

In landmark clinical trials (OPERA I, OPERA II for RMS, and ORATORIO for PPMS), Ocrevus demonstrated significant efficacy. In relapsing MS, it reduced annualized relapse rates by approximately 46–47% compared to high-dose interferon beta-1a. It also markedly increased the proportion of patients achieving no evidence of disease activity (NEDA). In primary progressive MS, Ocrevus was the first treatment to demonstrate a statistically significant reduction in the progression of clinical disability sustained over 12 and 24 weeks, compared with placebo.

What Should You Know Before Taking Ocrevus?

Before starting treatment with Ocrevus, your healthcare provider will conduct a thorough medical evaluation to ensure the medication is appropriate for you. Because Ocrevus modifies immune function by depleting B cells, it is essential that your doctor understands your full medical history, current infections, vaccination status, and any other medications you are taking. The following sections detail the critical considerations.

Contraindications

If any of these conditions apply to you, tell your doctor before receiving Ocrevus. Your doctor may decide to postpone treatment until the condition is resolved or determine that Ocrevus is not suitable for you.

Warnings and Precautions

Speak with your healthcare provider before receiving Ocrevus if any of the following apply to you, as your doctor may need to delay or modify your treatment plan:

Infections: Ocrevus affects the immune system, which means you may be more susceptible to infections during treatment. If you currently have an infection, your doctor will wait until it has resolved before administering Ocrevus. Before starting treatment and before subsequent injections, your doctor may request blood tests to check your immune system status. Common infections seen with Ocrevus include upper respiratory tract infections, influenza, sinusitis, bronchitis, and herpes infections (cold sores or shingles). Contact your doctor immediately if you develop fever, chills, a persistent cough, or signs of herpes during treatment.

Hepatitis B: Medications like Ocrevus can cause hepatitis B virus to become active again in people who carry the virus. Before starting treatment, your doctor will perform blood tests to check whether you are at risk of hepatitis B infection. Patients who have had hepatitis B or are carriers of the virus will be monitored for signs of reactivation throughout treatment.

Progressive Multifocal Leukoencephalopathy (PML): PML is a very rare but life-threatening brain infection caused by the JC virus. It can cause symptoms similar to MS, including memory problems, difficulty thinking, trouble walking, vision loss, and changes in speech. Although extremely rare with Ocrevus, PML has been reported. Tell your partner or caregiver about your treatment so they can notice symptoms you might not be aware of, and report any new neurological symptoms to your doctor immediately.

Cancer history: If you currently have cancer or have had cancer in the past, discuss this with your doctor. Your doctor may decide to delay or not proceed with Ocrevus treatment.

Injection reactions: Injection reactions are the most common side effect of subcutaneous Ocrevus. To minimize these reactions, you will receive pre-medication (typically a corticosteroid and an antihistamine) before each injection. You will be monitored during the injection and for at least one hour after your first injection. Reactions may occur during the injection or up to 24 hours afterward.

Vaccinations

Vaccination planning is critical before starting Ocrevus. You should not receive live or live-attenuated vaccines (such as BCG vaccine for tuberculosis or yellow fever vaccine) while on Ocrevus treatment. Your doctor may recommend the seasonal influenza vaccine. All necessary vaccinations should be completed at least 6 weeks before starting Ocrevus, as the medication depletes B cells needed for a proper immune response to vaccination.

Pregnancy and Breastfeeding

If you are pregnant, think you may be pregnant, or are planning to become pregnant, discuss this with your doctor before receiving Ocrevus. Ocrelizumab can cross the placenta and may affect the developing baby. Ocrevus should not be used during pregnancy unless the potential benefit justifies the potential risk to the fetus, as determined by your healthcare provider.

Contraception: Women of childbearing potential must use effective contraception during Ocrevus treatment and for at least 4 months after the last dose. Discuss your contraceptive options with your doctor.

Breastfeeding: Ocrelizumab may pass into breast milk. Speak with your doctor about the best approach to infant feeding if you are receiving Ocrevus. The decision should weigh the benefit of breastfeeding against the potential risk to the infant.

Driving and Using Machines

It is not known whether Ocrevus directly affects the ability to drive or operate machinery. Your doctor will advise you based on how your MS affects your functional capacity and whether any treatment-related side effects might impair your ability to perform these activities safely.

Children and Adolescents

Ocrevus is not intended for use in children and adolescents under 18 years of age, as it has not been studied in this age group. Clinical trials for Ocrevus were conducted exclusively in adult populations.

How Does Ocrevus Interact with Other Drugs?

Because Ocrevus works by depleting specific immune cells, combining it with other medications that affect the immune system can lead to additive immunosuppression. This increases the risk of serious infections and other complications. It is essential that you provide your doctor with a complete list of all medications, including prescription drugs, over-the-counter medications, and supplements.

Major Interactions

Minor Interactions

Ocrevus is not metabolized by the liver’s cytochrome P450 enzyme system, which means it has a low potential for traditional pharmacokinetic drug interactions. However, inactivated vaccines (such as the seasonal influenza vaccine) may have a reduced effectiveness during Ocrevus treatment, since the drug depletes B cells needed to mount a full immune response to vaccination. Your doctor may still recommend inactivated vaccines, as partial protection is better than no protection.

No formal drug interaction studies have identified clinically significant pharmacokinetic interactions between Ocrevus and common medications such as analgesics, antihypertensives, or antidepressants. Nevertheless, always inform your healthcare provider about any changes to your medication regimen.

What Is the Correct Dosage of Ocrevus?

Ocrevus dosing is straightforward compared to many other MS treatments. It is administered as a fixed dose at regular intervals, eliminating the need for dose adjustments based on body weight or disease severity in most cases. The medication is always administered by trained healthcare professionals in a clinical setting.

Adults

The injection is given in the abdomen, at least 5 cm away from the navel. Injections must never be given in areas where the skin is red, bruised, tender, hard, or in areas with birthmarks or scars. The injection site should be rotated with each dose.

Children

Ocrevus is not approved for use in children and adolescents under 18 years of age. There are currently no pediatric dosing recommendations, as clinical trials have not been conducted in this population. Pediatric MS is typically managed with other approved disease-modifying therapies.

Elderly

No specific dose adjustment is required for elderly patients. However, clinical trial data in patients over 55 years of age is limited. Older adults may have a higher baseline risk for infections and may require more careful monitoring during treatment. Your doctor will assess the benefit-risk ratio individually.

Missed Dose

If you miss a scheduled injection, contact your healthcare provider as soon as possible to arrange a new appointment. Do not wait until your next planned injection date. Maintaining the regular 6-month dosing schedule is important for optimal disease control. Your doctor will advise on the best timing for your next dose after a missed appointment.

Overdose

Since Ocrevus is administered by healthcare professionals in a controlled clinical setting, overdose is unlikely. There is limited experience with doses higher than 920 mg subcutaneously. In clinical development with the intravenous formulation, doses up to 2,000 mg were administered without identification of additional safety concerns beyond those seen at the approved dose. In the event of an overdose, the patient should be monitored closely for signs of injection reactions or infections, and appropriate supportive care should be provided.

What Are the Side Effects of Ocrevus?

Like all medicines, Ocrevus can cause side effects, although not everyone experiences them. The side effects are categorized below by their frequency of occurrence. Understanding these potential effects helps you recognize symptoms that should be reported to your healthcare provider promptly.

Injection Reactions

Injection reactions are the most frequently reported side effect of subcutaneous Ocrevus. In most cases, these reactions are mild to moderate in severity. They can occur during the injection or up to 24 hours afterward. Tell your doctor or nurse immediately if you experience any of the following symptoms: itching, rash, hives, skin redness, pain or swelling at the injection site, throat irritation, shortness of breath, throat swelling, flushing, low blood pressure, fever, fatigue, headache, dizziness, nausea, or rapid heartbeat.

To reduce the risk of injection reactions, you will always receive pre-medication before each Ocrevus dose. If you experience a life-threatening injection reaction, your doctor will permanently discontinue your treatment with Ocrevus.

Side Effect Frequency Overview

Serious Side Effects

Infections: You may be more susceptible to infections while on Ocrevus, because the medication depletes immune cells that also help fight pathogens. Before each dose, your doctor may check your blood to ensure your immune system is functioning adequately. If you have primary progressive MS with swallowing difficulties, Ocrevus may increase the risk of severe pneumonia.

Immunoglobulin decrease: Ocrevus can cause a reduction in immunoglobulin levels over time. Immunoglobulins are protective proteins produced by B cells that help fight infections. Your doctor will monitor your immunoglobulin levels through blood tests and may adjust your treatment if levels become too low.

Long-Term Safety Considerations

Long-term safety data from extension studies spanning over 8 years have generally been consistent with the known safety profile of ocrelizumab. The rate of serious infections has remained stable over time. However, cumulative B-cell depletion over many years of treatment may lead to progressive decreases in immunoglobulin levels. Regular monitoring and open communication with your healthcare provider are essential for safe long-term use.

How Should You Store Ocrevus?

Ocrevus is a hospital or clinic-administered medication, so storage is handled by healthcare professionals. However, it is useful to understand the storage requirements to ensure the medication is handled properly:

• Temperature: Store in a refrigerator at 2–8°C (36–46°F). Do not freeze.
• Light protection: Keep the vial in the outer carton to protect from light.
• Do not shake: The solution should not be shaken before use.
• Expiry date: Do not use after the expiration date printed on the outer carton and vial label (the last day of the stated month).
• Keep out of reach of children.

Once the solution has been drawn into a syringe, it should be administered promptly. If not used immediately, the prepared syringe can be stored at 2–8°C for up to 24 hours (or up to 30 days under validated aseptic conditions), and for an additional 8 hours at room temperature (up to 30°C) without light protection. Medicines should not be disposed of via wastewater to protect the environment.

What Does Ocrevus Contain?

Understanding the full composition of a medication is important, particularly for patients with allergies or sensitivities to specific excipients. Below is the complete list of ingredients in Ocrevus subcutaneous injection.

Active Ingredient

Ocrelizumab — 920 mg per vial (40 mg/mL concentration in 23 mL solution). Ocrelizumab is a recombinant humanized monoclonal antibody produced in Chinese hamster ovary (CHO) cells.

Inactive Ingredients (Excipients)

• Recombinant human hyaluronidase (rHuPH20) — facilitates subcutaneous absorption
• Sodium acetate trihydrate — buffer component
• Glacial acetic acid — pH adjustment
• α,α-Trehalose dihydrate — stabilizer
• Polysorbate 20 — surfactant
• L-Methionine — antioxidant
• Water for injections — solvent

Appearance and Packaging

Ocrevus is a clear to slightly opalescent, colorless to slightly brown solution for injection. It is supplied as a single glass vial containing 23 mL of solution. Each carton contains one vial. The solution should be visually inspected for particulate matter and discoloration before administration. Do not use if the solution is cloudy, discolored, or contains visible particles.

What Happens When You Stop Taking Ocrevus?

If you and your doctor decide to discontinue Ocrevus treatment, it is important to understand that the effects of the medication do not stop immediately. Because Ocrevus depletes CD20-positive B cells, your body needs time to regenerate these immune cells. B-cell levels in the blood typically begin to recover within 6 months after the last dose and generally return to normal levels within 6 months to two and a half years. In rare cases, full recovery may take longer.

During the B-cell recovery period, you may remain at increased risk for infections. Your doctor will continue to monitor your immunoglobulin levels and overall immune function. Before starting any new MS therapy or other immunosuppressive treatment, inform your new doctor about when you received your last dose of Ocrevus, as an adequate washout period may be necessary to avoid excessive immunosuppression.

It is crucial to maintain communication with your healthcare team throughout the transition period. Do not discontinue Ocrevus without first discussing with your doctor, as stopping treatment may lead to return of MS disease activity.

References

This article is based on the following peer-reviewed sources and regulatory documents:

1. European Medicines Agency (EMA). Ocrevus (ocrelizumab) – Summary of Product Characteristics. Last updated 2025. Available at: www.ema.europa.eu
2. Hauser SL, Bar-Or A, Comi G, et al. Ocrelizumab versus Interferon Beta-1a in Relapsing Multiple Sclerosis (OPERA I and OPERA II). N Engl J Med. 2017;376(3):221-234. doi:10.1056/NEJMoa1601277
3. Montalban X, Hauser SL, Kappos L, et al. Ocrelizumab versus Placebo in Primary Progressive Multiple Sclerosis (ORATORIO). N Engl J Med. 2017;376(3):209-220. doi:10.1056/NEJMoa1606468
4. U.S. Food and Drug Administration (FDA). Ocrevus Prescribing Information. Reference ID: 4981053. Available at: www.fda.gov
5. Rae-Grant A, Day GS, Marrie RA, et al. Practice guideline recommendations summary: Disease-modifying therapies for adults with multiple sclerosis. Neurology. 2018;90(17):777-788. doi:10.1212/WNL.0000000000005347
6. Montalban X, Gold R, Thompson AJ, et al. ECTRIMS/EAN guideline on the pharmacological treatment of people with multiple sclerosis. Mult Scler. 2018;24(2):96-120. doi:10.1177/1352458517751049
7. World Health Organization (WHO). Multiple sclerosis fact sheet. Available at: www.who.int
8. Wolinsky JS, Arnold DL, Brochet B, et al. Long-term follow-up from the ORATORIO trial of ocrelizumab for primary progressive multiple sclerosis: a post-hoc analysis from the ongoing open-label extension of the randomised, placebo-controlled, phase 3 trial. Lancet Neurol. 2020;19(12):998-1009.
9. British National Formulary (BNF). Ocrelizumab. National Institute for Health and Care Excellence (NICE). Available at: bnf.nice.org.uk

Editorial Team

This article has been written and reviewed by the iMedic Medical Editorial Team, comprising licensed physicians and pharmacologists with expertise in neurology, immunology, and clinical pharmacology. Our editorial process follows the GRADE evidence framework, ensuring all medical claims are supported by the highest available level of evidence.

Last medical review: January 29, 2026
Next scheduled review: July 2026
Evidence level: 1A (systematic reviews and randomized controlled trials)