The multiple sclerosis drug Tysabri will return to the market, with limitations, over one year after it was withdrawn following the development of a rare viral brain disease in two patients from the drug’s clinical trials. Tysabri was approved for marketing in November 2004 by the FDA. However, three months later, the drug was withdrawn. Later, a third patient was discovered to have the same disease, called progressive multifocal leukoencephalopathy. One of the patients is disabled and the other two died.
With Tysabri’s return to the market, the FDA has acknowledged that there will likely be additional deaths from the drug. However, many people with multiple sclerosis testified to a federal advisory panel that they would accept the drug’s risks based on the hope that it would slow the progression of their disease. Under the limitations of the drug’s return to the market, Tysabri will only be available through authorized infusion centers, and a monitoring program will track all patients who take the drug.