B cells play a central role in the pathogenesis in multiple sclerosis (MS), 
being involved in the activation of proinflammatory T cells, secretion of 
proinflammatory cytokines, and production of autoantibodies directed against 
myelin. Hence, the usage of B-cell-depleting monoclonal antibodies as therapy 
for autoimmune diseases including MS lay near at hand. Rituximab was the first 
therapeutic B-cell-depleting chimeric monoclonal antibody to be used 
successfully in MS. Ocrelizumab, a second-generation humanized anti-CD20 
antibody, was explored in a large phase II, randomized, placebo-controlled 
multicentre trial in patients with relapsing-remitting disease. Compared with 
placebo, two doses of ocrelizumab (600 and 2000 mg on days 1 and 15) showed a 
pronounced effect on disease activity seen in magnetic resonance imaging (MRI) 
as gadolinium-enhanced lesions (89% and 96% relative reduction, both p < 0.001) 
and also had a significant effect on relapses. In exploratory analyses, both 
doses of ocrelizumab had better effect on gadolinium-enhanced lesions than 
interferon beta-1a intramuscularly that was used as a reference arm. Adverse 
effects were mainly infusion-related reactions, in particular during the first 
infusion. Serious infections occurred at similar rates in ocrelizumab and 
placebo-treated patients, and no opportunistic infections were reported. 
However, progressive multifocal leukoencephalopathy (PML) has been reported in 
patients treated with anti-CD20 monoclonal antibodies for other indications. 
Other anti-CD20 monoclonal antibodies have been tested as treatments for MS, 
including ofatumumab that has shown beneficial results in placebo-controlled 
phase II trials in patients with relapsing-remitting MS. Ocrelizumab is now in 
phase III development for the treatment of relapsing-remitting MS, as well as 
primary progressive MS, and the results of ongoing clinical trials are eagerly 
awaited and will determine the place of ocrelizumab in the armamentarium of MS 
therapies.