Abstract
Ocrelizumab is a monoclonal antibody directed against the differentiation antigen CD20, which leads to an effective long-term depletion of lymphocytes, in particular B cells. Recently published phase 3 studies confirmed that ocrelizumab is effective in the treatment of both relapsing multiple sclerosis (RMS) and primary progressive multiple sclerosis (PPMS). Based on these results, ocrelizumab was the first drug to be approved for primary chronic progressive MS. To place this therapeutic breakthrough in the context of the current MS therapeutic landscape, it is worthwhile taking a look back at the development of antibody-mediated CD20 depletion, the studies underlying the approval of ocrelizumab and their open extension phases. This review article discusses the available data on the efficacy and safety of long-term B‑cell depletion in MS patients and reviews current knowledge on the role of B‑lymphocytes in the immunopathogenesis of MS.