Natalizumab is a humanized monoclonal antibody against the cell adhesion molecule α4-integrin. Natalizumab is used in the treatment of multiple sclerosis and Crohn’s disease. It is co-marketed by Biogen Idec and Élan as Tysabri, and was previously namedAntegren. Natalizumab is administered by intravenous infusion every 28 days. The drug is believed to work by reducing the ability of inflammatory immune cells to attach to and pass through the cell layers lining the intestines and blood–brain barrier. Natalizumab has proven effective in treating the symptoms of both diseases, preventing relapse, vision loss, cognitive decline and significantly improving quality of life in people with multiple sclerosis, as well as increasing rates of remission and preventing relapse in Crohn’s disease.
Natalizumab was approved in 2004 by the U.S. Food and Drug Administration (FDA). It was subsequently withdrawn from the market by its manufacturer after it was linked with three cases of the rare neurological condition progressive multifocal leukoencephalopathy(PML) when administered in combination with interferon beta-1a, anotherimmunosuppressive drug often used in the treatment of multiple sclerosis. After a review of safety information and no further deaths, the drug was returned to the US market in 2006 under a special prescription program. As of June 2009, ten cases of PML were known. However, twenty-four cases of PML had been reported since its reintroduction by October 2009, showing a sharp rise in the number of fatalities and prompting a review of the chemical for human use by the European Medicines Agency. By January 2010, 31 cases of PML were attributed to natalizumab. The FDA did not withdraw the drug from the market because its clinical benefits outweigh the risks involved. In the European Union, it has been approved for human use only for the treatment of multiple sclerosis and only then as a monotherapy because the initial cases of PML, and later the fatalities, were said by the manufacturers to be linked to the use of previous medicines by the patients.
Biogen Idec announced the initiation of the first clinical trial of natalizumab as a potential cancer treatment as of September 5, 2008.
- Meeting highlights from the Committee for Medicinal Products for Human Use” (pdf). European Medicines Agency. 2009-10-22. Retrieved 2010-08-31.
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- Jeffrey, S (2010-02-05). “PML Risk Increases With Repeated Natalizumab Infusions: FDA”. Medscape. Retrieved 2010-08-31.
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- “Biogen Idec testing Tysabri as a cancer treatment”. The Boston Globe. 2008-09-05. Retrieved 2008-09-05.