Four More Brain Infections Found in Tysabri Users, Biogen Says

Four more cases of a rare but potentially fatal brain infection have been found among patients taking the multiple sclerosis drug Tysabri, the drug’s maker said.

That brings to 28 the total number of cases of progressive multifocal leukoencephalopathy (PML) found among Tysabri users since July 2008, according to a Boston Business Journal report.

Tysabri was approved by the Food and Drug Administration in November 2004, but was removed from the market within a few months after some users developed PML. The drug was allowed back on the market in July 2006 after stronger warning labels about the risks of PML were added to the drug’s labeling.

Tysabri is FDA approved to treat relapsing forms of multiple sclerosis and moderate to severe cases of Crohn’s disease, a form of inflammatory bowel disease. However, the vast majority of patients taking the drug are being treated for multiple sclerosis. Virtually no cases of PML have been reported in Crohn’s disease patients.

The risks of PML increase the longer a patient takes the drug, so the number of cases is expected to continue to rise. Many of the PML cases have been found in patients living outside the United States, officials said.

FDA Warnings

The FDA has repeatedly warned about the risks of PML from taking Tysabri. In April 2009, the FDA slapped the drug’s maker, Biogen Idec Inc., over Internet advertisements for Tysabri. The FDA said the ads falsely promoted the drug without emphasizing the risks of PML and other serious health complications.

In September 2009, a new study concluded that Tysabri put patients at greater risk of developing PML by awakening the virus that causes the disease and making the virus even stronger.

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