Late-onset neutropenia following ocrelizumab therapy for multiple sclerosis

Ocrelizumab is a monoclonal antibody directed at CD20, a membrane glycosylated phosphoprotein found predominately on B-lymphocytes, but not plasma cells or neutrophils, which has shown efficacy in treatment of relapsing and primary progressive multiple sclerosis (MS). In phase 3 clinical trials, infusion reactions, infections, and a small number of malignancies were found more frequently with ocrelizumab than placebo. IV administration results in rapid depletion of pre-B and mature B-lymphocytes.1 Ocrelizumab, administered every 6 months, was approved for treatment of MS in the United States in March 2017, and is closely related in structure and mechanism of action to rituximab, used for many years in treatment of rheumatoid arthritis. As of August 2018, the manufacturer reports >61,800 people have received ocrelizumab postmarketing, and >3,800 in clinical trials.