Expert opinion: guidelines for the use of natalizumab in multiple sclerosis patients previously treated with immunomodulating therapies.

Natalizumab (Tysabri) (anti-VLA4) is a novel agent for treatment of relapsing multiple sclerosis (MS) [Polman C.H., O'Connor P.W., Havrdova E. et al., 2006. A randomized, placebo-controlled trial of natalizumab for relapsing multiple sclerosis. N. Engl. J. Med. 354, 899-910.]. Controlled trials have shown considerable efficacy in preventing relapses, in excess of that seen for other EMEA-approved disease modulating drugs. While well-tolerated and generally safe, three cases of progressive multifocal leukoencephalopathy (PML) occurred in the context of 3 clinical trials encompassing some 3300 patients using this drug in multiple sclerosis and Crohn's disease. Immune compromised patients, such as those receiving immunosuppressive medications, are at a higher risk of developing PML. Natalizumab was recently approved for the treatment of relapsing forms of MS. This includes patients who had an inadequate response to other therapies and some of these patients will have already received immunosuppressants. These agents have the potential to cause prolonged effects on the immune system, even after dosing has been discontinued. Determining that these patients are not immunocompromised will be an important safety issue to consider prior to the initiation of natalizumab therapy. This short report summarizes interdisciplinary practical recommendations from specialists in neuroimmunology, rheumatology, transplantation medicine and clinical immunology.