April 22, 2009 – The makers of Natalizumab [Tysabri], Biogen Idec, on April 20, 2009, have revealed yet another new case of progressive multifocal leukoencephalopathy (PML) in a multiple sclerosis patient being treated with Natalizumab [Tysabri].
That means that six patients have developed the potentially deadly brain infection since Natalizumab [Tysabri] was reintroduced to the market in July 2006. In the latest case, the patient had been on the drug for 31 months, the longest duration so far. The previous high had been 26 months and the average now is 19 months. Biogen added that 6,800 patients have been on Natalizumab [Tysabri] over 24 months, 14,400 over 18 months and 24,900 at least one year.
Progressive multifocal leukoencephalopathy (PML) is caused by the reactivation of a common virus in the central nervous system of immune-compromised individuals. Polyomavirus JC (often called JC virus) is carried by a majority of people and is harmless except among those with lowered immune defenses. The disease occurs, rarely, in organ transplant patients, people undergoing chronic corticosteroid or immunosuppressive therapy; and individuals with cancer, such as Hodgkin’s disease, lymphoma, and sarcoidosis. PML is most common among individuals with acquired immune deficiency syndrome (AIDS). Studies estimate that prior to effective antiretroviral therapy, as many as 5 percent of people with AIDS eventually developed PML. For them, the disease was most often rapidly fatal.
Besides Natalizumab [Tysabri], there are other pharmacological agents associated with case reports of PML, including Tacrolimus [Prograf], Rituximab [Rituxan], Mycophenolate Mofetil [CellCept], and Mycophenolic Acid [Myfortic]. Most prominently, Efalizumab [Raptiva] is just being withdrawn from the market based on its association with progressive multifocal leukoencephalopathy (PML).
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