ocrelizumab

Ocrelizumab is a humanized monoclonal antibody that binds the CD20 antigen on B lymphocytes. By depleting circulating CD20-positive B cells, it modulates immune activity and reduces inflammatory processes in the central nervous system. It is approved for the treatment of multiple sclerosis, including relapsing forms and primary progressive MS.

It is administered by intravenous infusion in a two-dose first cycle (600 mg on day 0 and at week 2), followed by 600 mg every six months. Premedication with an antihistamine, acetaminophen, and sometimes corticosteroids is commonly used to lessen infusion reactions. Before starting therapy, patients are screened for hepatitis B infection, and vaccination status is reviewed.

Common adverse effects include infusion-related reactions during or after infusions and increased risk of infections, such as upper respiratory tract infections. Because B cells are depleted, there is potential for serious infections and reduced vaccine responses. Rare cases of malignancy have been reported in long-term use. Clinicians monitor blood counts and immunoglobulin levels; treatment is withheld during active infection.

Contraindications include active infections and known hypersensitivity to ocrelizumab or its excipients. Live vaccines should be avoided during therapy; non-live vaccines may be given but responses can be diminished. Pregnancy safety has not been fully established; women may be advised to avoid pregnancy during treatment and for an interval after the last dose, with decisions individualized.