Natalizumab in relapsing-remitting multiple sclerosis.

Natalizumab is the first humanized moclonal antibody indicated in the treatment of relapsing-remitting multiple sclerosis (RRMS). Based on its remarkable efficacy in reducing disease activity and reducing the risk of disability progession in RRMS, and the risk of a serious adverse event (progressive multifocal leukoencephalopathy [PML]), natalizumab was indicated in active RRMS, mostly as a second-line therapy. With natalizumab and other recent anti-inflammatory therapies, the concept of no evidence of disease activity has emerged and may sometimes be achievable. Use of natalizumab in other inflammatory diseases of the nervous system has been less encouraging than in MS. PML remains the main serious adverse event occuring during natalizumab therapy. PML risk stratification according to JCV serology and JCV index is now being applied more often. Other PML risk biomarkers are being evaluated. If stopping natalizumab is planned, the wash-out period needs to be less than 12 weeks and probably closer to 4-8 weeks with efficient validated immunomodulatory or immunosuppressive therapies in RRMS.