Ocrevus (ocrelizumab) is a prescription infusion therapy used to treat multiple sclerosis (MS). It is one of the few MS medications approved for both relapsing forms of MS and primary progressive MS, making it unique among available treatments. The FDA first approved it in 2017, and it has since become one of the most widely prescribed higher-efficacy MS therapies.
FDA-Approved Uses
Ocrevus is approved for two broad categories of MS in adults. The first is relapsing forms of MS, which includes clinically isolated syndrome (a single episode of neurological symptoms), relapsing-remitting MS, and active secondary progressive MS. The second is primary progressive MS, the form where disability gradually worsens from the start without distinct relapses.
That second approval is particularly significant. Primary progressive MS has historically had very few treatment options, and Ocrevus was the first therapy to receive FDA approval specifically for it. In current clinical practice, ocrelizumab is commonly used as a first-line therapy for primary progressive MS, though results tend to be strongest for younger patients and those who still show new or active brain lesions on MRI.
How Ocrevus Works
In MS, the immune system mistakenly attacks the protective coating around nerve fibers in the brain and spinal cord. A specific type of white blood cell called a B cell plays a key role in driving this damage. Ocrevus is designed to selectively find and eliminate B cells that carry a surface marker called CD20.
Once Ocrevus binds to these cells, it triggers several mechanisms that destroy them. This reduces the pool of B cells available to present self-targeting signals to other immune cells, release inflammatory chemicals, produce harmful antibodies, and form clusters of immune tissue in the lining of the brain. Importantly, Ocrevus targets B cells in the middle of their life cycle. It spares the earliest stem cells (so your body can still make new B cells over time) and spares plasma cells (which produce many of the antibodies you need for everyday immunity).
How Well It Works for Relapsing MS
Ocrevus was tested against an older injectable MS therapy in two large clinical trials called OPERA I and OPERA II. Across the trials, patients on Ocrevus experienced roughly a 50% reduction in their annual relapse rate compared to those on the older treatment. Patients receiving Ocrevus were also significantly more likely to show no evidence of disease activity, meaning no relapses, no new brain lesions, and no worsening disability. In the trials, Ocrevus-treated patients were more than two and a half times as likely to reach that benchmark.
These results are part of why the American Academy of Neurology notes a growing trend toward using higher-efficacy therapies like Ocrevus early in the disease course, rather than starting with milder drugs and escalating only after a patient worsens.
How Well It Works for Primary Progressive MS
For primary progressive MS, the pivotal trial was called ORATORIO. Because this form of MS doesn’t typically produce clear relapses, the trial measured disability progression instead. After more than six and a half years of follow-up, patients who started Ocrevus from the beginning fared meaningfully better than those who initially received a placebo.
About 52% of early Ocrevus patients had confirmed worsening on a standard disability scale, compared to 65% in the group that started on placebo. Hand dexterity declined in 31% of the Ocrevus group versus 43% of the placebo group. Perhaps most striking, 11.5% of patients who started Ocrevus early reached the point of needing a wheelchair, compared to 18.9% in the placebo group. These differences don’t represent a cure, but they show a consistent slowing of the disease across multiple measures of physical function.
What the Infusion Looks Like
Ocrevus is given as an intravenous infusion at a clinic or infusion center. The first dose is split into two smaller infusions of 300 mg, given two weeks apart. After that, you receive a single 600 mg infusion every six months.
The initial infusions take about three and a half hours. If you tolerate those well without a serious reaction, your doctor can switch to a shorter protocol of about two hours for later doses. This shorter infusion time was approved by the FDA after a clinical trial at Cleveland Clinic confirmed it didn’t increase safety risks. Before each infusion, you’ll typically receive a steroid and possibly other medications to reduce the chance of a reaction.
Common Side Effects
The most frequently reported side effect is infusion-related reactions, which occurred in 34% to 40% of patients in clinical trials. These reactions are most common during the very first infusion and tend to be milder with subsequent doses. Symptoms can include itching, rash, flushing, throat irritation, and occasionally fever or changes in blood pressure. Most reactions are mild to moderate and manageable with the pre-medications given before the infusion.
Upper respiratory tract infections are the other common side effect, occurring at higher rates than in comparison groups for both relapsing and primary progressive MS. Patients with primary progressive MS also reported skin infections and lower respiratory tract infections more often than those on placebo. Because Ocrevus depletes B cells, your immune system’s ability to fight off certain infections is reduced, so staying current on vaccinations before starting treatment is important.
Key Safety Considerations
Before starting Ocrevus, your doctor will screen you for hepatitis B with blood tests. Ocrevus is contraindicated if you have an active hepatitis B infection because the drug could cause the virus to reactivate. If your blood work shows past exposure to hepatitis B, a liver specialist will typically be consulted before you begin treatment.
There is also a risk of progressive multifocal leukoencephalopathy (PML), a rare but serious brain infection. Cases have been reported in post-marketing surveillance, including in patients who had never taken other immunosuppressive MS drugs previously associated with PML. This is uncommon, but any new neurological symptoms that seem different from your typical MS symptoms should be evaluated promptly.
Pregnancy and Family Planning
If you’re considering pregnancy, the standard recommendation is to use contraception for at least six months after your last Ocrevus infusion before trying to conceive. This allows the drug to clear your system and B cells to begin recovering. In some cases, particularly for women with highly active disease who want to minimize time off treatment, neurologists may discuss attempting conception as early as one to three months after an infusion. This is a conversation to have with your neurologist, who can weigh your disease activity against the timing of conception.
Where Ocrevus Fits Among MS Treatments
MS treatments generally fall along a spectrum from lower-efficacy, lower-risk options (like some oral medications and older injectables) to higher-efficacy therapies that carry more significant immune effects. Ocrevus sits firmly in the higher-efficacy category. The traditional approach in the U.S. has been to start with milder therapies and escalate if disease activity continues, and this remains the most common strategy in many countries. However, a growing number of MS specialists favor starting with a drug like Ocrevus early, especially for patients with active disease or poor prognostic signs, based on the reasoning that preventing early damage leads to less long-term disability.
Ocrevus is also commonly chosen for patients who test positive for the JC virus antibody, which increases the risk of PML with certain other MS therapies like natalizumab. While Ocrevus carries its own small PML risk, it is considered a practical alternative for patients who cannot safely use those other options.