Ocrevus is a intravenous treatment for both primary progressive and relapsing forms of multiple sclerosis. The approval is a major breakthrough since no treatments had previously been approved for primary progressive multiple sclerosis. This monoclonal antibody treatment works by depleted B cells, a type of immune cell. Ocrevus is given intravenously with half given the first day and a second half given 2 weeks later, followed by a single infusion every 6 months.

In 2 relapsing multiple sclerosis trials (OPERA I and II), patients treated with Ocrevus had 46 to 47% less relapses than Rebif. In addition, patients treated with Ocrevus were 40% less likely to progress in disability compared to Rebif treated patients. On MRI scans, the average number of active contrast-enhancing lesions were 94-95% less with Ocrevus treatment than Rebif. In a primary progressive trial (ORATORIO) of 732 patients, treatment with Ocrevus reduced risk of disability progression by 24% compared to placebo treatment. A 29% benefit was also seen on the time to walk 25 feet.

The most common side effects in clinical trials were infusion reactions and upper respiratory tract infections, which were mostly mild to moderate in severity. Although PML (progressive multifocal leukoencephalopathy) did not occur in Ocrevus clinical trials, this brain infection, which is potentially fatal, has occurred rarely with another B-cell depleting treatment. Other serious infections including reactivation of a Hepatitis B infection are risks. A higher rate of malignancies was seen on ocrelizumab than placebo or Rebif so possible risk of treatment with Ocrevus.