The label of multiple sclerosis drug Tysabri, sold by Biogen Idec Inc. and Elan Corp., has been changed to include the updated incidence of a rare brain infection.
A Biogen spokeswoman said the company worked with the Food and Drug Administration on the change, which includes a table that details the incidence of progressive multifocal leukoencephalopathy, or PML.
The included data shows the risk of getting the infection is 0.3 patients per 1,000 when using the drug for less than two years. That rate rises when using the drug for two to three years, to 1.5 cases, but notably drops to 0.9 cases for the period of three to four years. The data is current as of January, and Biogen said the label will be updated as needed.
Although the company provides monthly updates on the number of PML cases, the incidence rates for patients within the fixed duration ranges of treatment have remained relatively stable.
As of early March, 102 cases of the infection were confirmed, including 21 deaths. The FDA receives information on new cases in real-time and has previously said that benefits of Tysabri outweigh the risk of PML.
The drug is generally regarded as highly effective, but is mostly used for patients that have stopped responding to other drugs or have aggressive cases of the disease.
Biogen is developing a blood test that may better determine the chances of patients contracting PML. The test recently received CE Mark approval for use in Europe and the companies are conducting large studies of its effectiveness.
Biogen and Elan has proposed updating the label of Tysabri to include information about certain antibodies in the blood being a risk factor for acquiring the infection.
Tysabri was withdrawn from the market in 2005 and relaunched in 2006—because of its effectiveness—with a strict access plan that monitors patients.
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