The Food and Drug Administration on Friday alerted public that the risk of developing PML, or, progressive multifocal leukoencephalopathy , a rare but serious brain infection associated with the use of multiple sclerosis drug Tysabri increases with the use of the drug.
Tysabri is administered as a single intravenous infusion every four weeks and according to the FDA, the risk of developing PML increases with the number of Tysabri infusions received.
Tysabri is co-marketed by Biogen Idec Inc. (BIIB) and Elan Pharmaceuticals Inc., a subsidiary of Elan Corp plc (ELN). The drug, which was given FDA approval for multiple sclerosis in November 2004, was voluntarily withdrawn from the market in February 2005, after it was found that three patients taking the drug developed PML.
The drug was allowed back on the U.S. market by the FDA in July 2006, and launched in several European countries, but with certain restrictions and enhanced safety warnings. In January 2008, Tysabri was also approved for the treatment of moderate to severe Crohn's disease.
The FDA in a statement said that since the launch of Tysabri in 2006, through January 21, 2010, there have been 31 confirmed cases of PML worldwide in patients using the drug, proving fatal in eight cases. All the eight patients were receiving Tysabri as monotherapy for the treatment of multiple sclerosis. However, there have been no postmarketing reports of PML in patients treated with Tysabri for Crohn's disease.
The regulatory agency said that the clinical benefits of Tysabri continue to outweigh the potential risks and the new safety information about Tysabri will now be included in the drug label and patient Medication Guide.
Last month, Biogen Idec revealed that sales of Tysabri achieved "blockbuster" status in 2009. As of the end of December 2009, about 48,800 patients were on commercial and clinical Tysabri therapy worldwide, according to Biogen Idec. In 2009, the number of patients on the therapy grew by 30% over the prior year and sales of the drug topped $1 billion, compared to $813 million in 2008.
The FDA in its statement said that about 66,000 people, worldwide, have received at least one dose of Tysabri since marketing resumption through December 31, 2009.
BIIB closed Friday's trading at $53.53, up 0.81% while ELN closed the day's trade at $7.15, up 0.14%.
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