Biogen Idec Inc.'s CEO, James Mullen, said in an interview with the Associated Press that the Cammbridge, Mass., company will recommend that the drug, Tysabri, include warnings about three cases of progressive multifocal leukoencephalopathy (PML), that were confirmed after clinical trials. Tysabri was withdrawn from the market on Feb. 28, three months after receiving U.S. Food and Drug Administration approval and despite hopes that it would become an important new tool in treating MS.

Mullen said the revised label that the company will propose to the FDA also will warn about risks for patients who have weak immune systems, and therefore could be more susceptible to contracting the disease.

However, Mullen added that the label language his company will suggest will acknowledge that scientists don't understand precisely how the bioengineered drug put the three patients who contracted PML at risk of contracting the rare disease, the AP reported. Two of those patients died.

Mullen said Biogen Idec and its Irish partner on Tysabri, Elan Corp., plan to submit findings from their review of the drug's safety to the FDA by the end of September.

After reviewing one year of data from planned two-year trials, federal regulators in November had approved Tysabri for sale to the 350,000 American sufferers of MS, a debilitating and incurable disease in which the body's immune system turns rebellious, attacking, inflaming and damaging its own nerve tissue.

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