Natalizumab for the treatment of Crohn's disease.

Natalizumab (Tysabri, formerly known as Antegren, Elan Pharmaceuticals [Elan; San Francisco, CA, USA] and Biogen Idec [Biogen; Cambridge, MA, USA]) is a humanized monoclonal antibody against alpha4 integrin, which inhibits leukocyte adhesion and migration into inflamed tissue. The drug has been shown to be more efficacious than placebo in inducing response and maintaining remission in moderate-to-severe Crohn's disease. There have been reports of progressive multifocal leukoencephalopathy after treatment with natalizumab in Crohn's disease and multiple sclerosis. It has been otherwise well tolerated, although it is associated with an increased risk of infections, especially influenza and influenza-like illness. The drug is not approved in Europe for the treatment of Crohn's disease, but it is approved in the USA for the treatment of both multiple sclerosis and moderate-to-severe Crohn's disease. Owing to the risk of progressive multifocal leukoencephalopathy, it can only be given under the TOUCH program, which is a special restricted distribution program available only to prescribers, infusion centers, pharmacies associated with infusion sites and patients who are enrolled in the program.