Tysabri re-enters clinical trial program

USA-based Biogen Idec and Irish drugmaker Elan say they have dosed the first patients in a monotherapy safety extension study of their drug Tysabri (natalizumab), used in the treatment of multiple sclerosis. Previously, the firms withdrew the drug from the US market and all clinical trials following reports of links to the potentially-fatal brain disease progressive multifocal leukoencephalopathy, which emerged early last year (Marketletter March 7, 2005).

In the second half of 2005, Elan and Biogen, in collaboration with experts in MS and PML, completed a 3,000 patient safety evaluation of Tysabri (Marketletter August 15, 2005), which revealed no new cases of PML associated with the drug's use beyond the three which had been reported.

On March 8 this year, the US Food and Drug Administration's Peripheral and Central Nervous System Drugs Advisory Committee recommended the re-introduction of the product as a treatment for relapsing forms of the condition. Elan and Biogen say they expect a decision from the FDA before June 28 this year.