Tysabri Update: No New Cases of PML Reported

Concluding their safety evaluation of natalizumab (Tysabri), Elan Corporation and Biogen-Idec, the drug's manufacturers, have found no new confirmed cases of progressive multifocal leukoencephalopathy (PML). The drug was voluntarily pulled from the market in late February based on reports of its association with several cases of PML, a rare and potentially fatal demyelinating disease of the central nervous system.

 The Food and Drug Administration (FDA) had previously approved Tysabri for use in multiple sclerosis (MS) in November 2004. Tysabri also was under study as a potential treatment for Crohn's disease and rheumatoid arthritis.

The drug's suspension occurred after two MS patients, who had been treated with Tysabri in combination with Avonex® (Interferon beta-1a), developed PML. Subsequently, a third patient, who was enrolled in a Crohn's disease clinical trial of Tysabri, also contracted PML.

In its most recent public health advisory, the FDA stated that although the relationship between Tysabri and PML is not yet known, all clinical testing of the drug has been suspended. The FDA has urged patients formerly treated with Tysabri or enrolled in clinical trials of the drug to consult their physician to explore alternative treatments.

There are no further recommendations to patients at this time other than to discontinue all use of Tysabri. Discussions between the FDA, Biogen Idec, and scientific experts are underway to assess the potential link between Tysabri and PML; evaluate methods for early diagnosis; and address ways to identify those at particular risk for developing PML

For more information, please visit FDA.