Biogen Idec Inc. and Elan Corp. PLC said Wednesday that European Union regulators have expanded the warning label on their multiple sclerosis drug Tysabri to help identify patients who are at risk for a dangerous brain inflammation.
The companies said the European Commission approved a warning that says patients who have an antibody to a common virus called JC Virus. The antibody indicates they have been infected with the virus. Patients who have JC Virus and severe immune deficiencies have a greater risk of developing a potentially deadly brain infection called progressive multifocal leukoencephalopathy. Tysabri also increases the risk of that infection.
The new label also says patients who have JC Virus antibodies, have been treated with drugs that suppress the immune system, and have been treated with Tysabri for more than two years have the greatest risk of developing PML. The companies said about 55 percent of MS patients are JC-antibody positive.
European Union regulators approved Tysabri in June 2006. Use of Tysabri is closely supervised because of its link to PML. Biogen said 83,300 people had been treated with Tysabri at the end of the first quarter, including 58,400 on active treatment.
Shares of Biogen Idec picked up $1.15 to $99.80 in morning trading, and Elan shares gained a penny to $10.70.