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U.S. warns of infection

drug Tysabri brain



Reuters 22/04/2011
Risk brain infection caused by the drug Tysabri, Biogen Idec against MS is highest during the third year of treatment, health officials said the United States in an updated warning issued on Friday.

potentially fatal infection known as leuco encephalopathy leukoencephalopathy (PML, for its acronym in English) occurs in approximately 1.5 per 1,000 patients treated with Tysabri during the months 25 to 36, said the Food and Drug Administration (FDA, for its acronym in English .)

The drug is given monthly by oral infusion.

Biogen withdrew the drug in 2005 after the first reports of infection in the brain, but Tysabri returned to the market with restrictions in 2006.

Fears of brain infection have limited the use of the drug, which generates sales of more than 1,000 million dollars per year.

The FDA said Friday that the risk of brain infection was 0.3 per 1,000 patients during the first two years of treatment.

estimates were added to the prescription instructions for Tysabri, which Biogen occurs with the Irish drug maker Elan Corp Plc.

The FDA said it was the first time I had considered the possibilities of progressive multifocal leuko encephalopathy at specified intervals rather than providing a cumulative risk for years.

A new estimate "will allow those who prescribe a better assessment of risk based on the duration of treatment," the agency said.

The FDA said 102 cases of PML had been reported in the world to 28 February. The agency "continues considered the benefits of taking Tysabri outweigh the potential risks," according to a notice posted on its website.

Annual sales of Tysabri, the brand of the drug natalizumab, would reach almost 1,500 billion in 2015, according to consensus forecasts Thomson Reuters.