Understanding What Drug Category is Ocrevus?

October 10, 2025 •

5 min read

Ocrevus (ocrelizumab) was the first and only therapy approved by the U.S. Food and Drug Administration (FDA) for both relapsing and primary progressive forms of multiple sclerosis in adults. But what drug category is Ocrevus? It belongs to a class of highly specific, targeted immunotherapies known as anti-CD20 monoclonal antibodies, which selectively deplete certain immune cells believed to drive MS pathology.

Quick Summary

Ocrevus (ocrelizumab) is an anti-CD20 monoclonal antibody, a targeted immunotherapy used to treat multiple sclerosis by depleting specific B-cells that cause nerve damage.

Key Points

Drug Category: Ocrevus (ocrelizumab) is an anti-CD20 monoclonal antibody, a type of targeted immunotherapy.
Mechanism of Action: It works by binding to the CD20 protein on the surface of B cells, leading to their depletion and reducing the inflammatory damage seen in multiple sclerosis.
Therapeutic Indications: Ocrevus is FDA-approved for treating both relapsing forms of MS and primary progressive MS in adults.
Administration and Schedule: Ocrevus is typically administered via intravenous infusion every six months, offering a less frequent dosing schedule than many other MS treatments.
Safety Profile: Common side effects include infusion-related reactions and an increased risk of infections due to its immunosuppressive effects.
Serious Risks: Rare but serious risks associated with Ocrevus include Progressive Multifocal Leukoencephalopathy (PML) and Hepatitis B virus reactivation.
Targeted vs. Traditional: As a targeted therapy, Ocrevus offers a more specific approach to immunosuppression compared to broad-spectrum drugs, leading to fewer systemic side effects.

What is a Monoclonal Antibody?

To understand the specific classification of Ocrevus, it's helpful to first grasp the concept of a monoclonal antibody (mAb). Monoclonal antibodies are lab-produced proteins designed to mimic the natural antibodies our immune systems produce to fight off pathogens. However, unlike natural antibodies which target a wide range of invaders, a monoclonal antibody is engineered to specifically target one particular substance, or a single 'epitope'. In the case of autoimmune diseases like multiple sclerosis (MS), these lab-made antibodies can be used to target specific components of the immune system that are mistakenly attacking the body's own healthy cells.

Monoclonal antibodies are a cornerstone of modern targeted therapy, offering a more precise approach compared to older, broader-acting immunosuppressants. By focusing on a specific part of the immune response, they can minimize collateral damage to healthy cells and reduce the systemic side effects often associated with less specific treatments.

The Anti-CD20 Subcategory: How Ocrevus Works

Ocrevus (ocrelizumab) falls into the specific category of anti-CD20 monoclonal antibodies. This subcategory is defined by its target: the CD20 protein, a marker found on the surface of pre-B cells, mature B cells, and memory B cells. B cells are a type of white blood cell and are key players in the immune system. While they are crucial for fighting infections, in MS, certain B cells are thought to contribute to the inflammatory process that damages the myelin sheath protecting nerve fibers.

Ocrevus functions as a "CD20-directed cytolytic antibody". It binds to the CD20 protein, marking the B cells for destruction by other parts of the immune system. This targeted action leads to a depletion of the specific B-cell population involved in the MS disease process. Because the drug does not target the B-cell progenitors (stem cells) or terminally differentiated plasma cells, the body can still regenerate new, healthy B cells over time, and pre-existing immunity is largely preserved.

The precise mechanisms through which Ocrevus depletes B cells include:

Antibody-Dependent Cellular Cytotoxicity (ADCC): The antibody's Fc region recruits natural killer (NK) cells to destroy the targeted B cells.
Antibody-Dependent Cellular Phagocytosis (ADCP): Phagocytes, such as macrophages, engulf and destroy the antibody-coated B cells.
Complement-Dependent Cytotoxicity (CDC): The antibody activates the complement system, leading to the formation of a membrane attack complex that ruptures the B cell.
Apoptosis: The binding of the antibody can directly trigger programmed cell death in the B cell.

Therapeutic Role in Multiple Sclerosis

By depleting the population of pathogenic B cells, Ocrevus helps reduce the inflammatory activity that characterizes MS. This therapeutic effect translates into several key clinical benefits for patients with both relapsing and primary progressive forms of the disease.

In Relapsing-Remitting MS (RRMS): Ocrevus has been shown in clinical trials to significantly reduce the annual relapse rate compared to traditional interferon therapy. It also reduces disability progression and suppresses new or enlarging lesions on MRI scans.
In Primary Progressive MS (PPMS): Ocrevus was the first disease-modifying therapy approved for PPMS. In clinical studies, it demonstrated a reduced risk of confirmed disability progression compared to placebo. This provides a valuable treatment option for a form of MS that previously had limited therapeutic options.

Important Safety Considerations

Like all powerful medications, Ocrevus comes with a range of side effects and safety warnings that patients and healthcare providers must consider. Due to its immunosuppressive action, a primary concern is an increased risk of infection.

Infusion Reactions: These are common, especially with the first infusion, and can include symptoms like flushing, rash, headache, fever, and nausea. Patients are premedicated with corticosteroids and antihistamines to mitigate these reactions, and are monitored for at least an hour after the infusion.
Increased Risk of Infections: By depleting B cells, Ocrevus weakens the immune system's ability to fight off infections. Common infections include upper respiratory tract infections, while more serious or rare infections can occur. Patients should report any signs of infection to their doctor immediately.
Progressive Multifocal Leukoencephalopathy (PML): PML is a rare, severe brain infection that can lead to death or severe disability and has been reported in patients treated with Ocrevus. This risk must be weighed against the benefits of treatment.
Hepatitis B Reactivation: Screening for Hepatitis B is necessary before starting Ocrevus, as the drug can cause a dormant virus to become active.
Vaccination Response: Ocrevus can reduce the effectiveness of vaccines. Live vaccines should be avoided, and inactivated vaccines should be given well before starting treatment.

Ocrevus vs. Other Anti-CD20 Monoclonal Antibodies

While Ocrevus is a key therapy in the anti-CD20 class, it's part of a broader family of drugs that have evolved over time. Understanding the distinctions between these agents is important for grasping the nuances of treatment. Other notable anti-CD20 antibodies include Rituximab, which is chimeric (part mouse, part human), and Ofatumumab, which is fully human.


Feature	Ocrevus (Ocrelizumab)	Rituximab	Ofatumumab (Kesimpta)
Drug Type	Humanized IgG1 monoclonal antibody	Chimeric (mouse/human) IgG1 monoclonal antibody	Fully human IgG1 monoclonal antibody
Mechanism	Targets CD20, leads to B-cell depletion via ADCC, CDC, ADCP, apoptosis.	Targets CD20, similar mechanisms but with potential differences in potency or specific pathways.	Targets CD20, higher CDC activity due to different binding site closer to cell surface.
Administration	Intravenous (IV) infusion every 6 months. A subcutaneous option exists (Ocrevus Zunovo).	Intravenous (IV) infusion (often weekly or monthly). Also available subcutaneously.	Subcutaneous (SC) injection, self-administered monthly.
MS Indications	Relapsing Forms and Primary Progressive MS.	Used off-label for MS.	Relapsing Forms of MS.

Conclusion

Ocrevus is a targeted immunotherapy in the anti-CD20 monoclonal antibody drug category. Its mechanism of selectively depleting B cells that drive inflammation in multiple sclerosis has made it a highly effective treatment for both relapsing and primary progressive forms of the disease. While offering significant therapeutic benefits, it is a powerful medication with notable risks, primarily related to infection, that require careful monitoring. Its bi-annual infusion schedule offers a convenient option for many patients compared to more frequent treatments. The development of Ocrevus represents a significant advancement in MS treatment, moving toward more precise and effective immunomodulation.

For more detailed information on ocrelizumab, visit the Cleveland Clinic website.

Frequently Asked Questions

No, Ocrevus is not a chemotherapy drug. It is a targeted immunotherapy that specifically depletes CD20-positive B cells rather than acting on all rapidly dividing cells, which is the hallmark of traditional chemotherapy.

After the initial two doses, which are given two weeks apart, Ocrevus is typically administered as a single intravenous infusion every six months. A shorter, subcutaneous injection option called Ocrevus Zunovo is also available.

The specific target of Ocrevus is the CD20 protein, which is found on the surface of certain B-lymphocytes. By binding to this protein, Ocrevus marks the B cells for destruction.

Common side effects include infusion-related reactions (such as rash, fever, and headache), upper and lower respiratory tract infections, skin infections, and depression.

Yes, Ocrevus is FDA-approved for the treatment of primary progressive multiple sclerosis (PPMS) in adults and was the first drug to receive approval for this indication.

Ocrevus increases the risk of infection because it weakens the immune system by depleting CD20-positive B cells. These cells normally help fight off infections, so their reduction can make a patient more vulnerable.

Ocrevus is a humanized monoclonal antibody, whereas Rituximab is a chimeric (part human, part mouse) antibody. The engineering of Ocrevus may result in different binding properties and a potentially lower risk of immunogenicity.