Lowering Risk in Taking Tysabri

An antibody blood test is being developed to tell whether you have been exposed to the virus that can cause the brain viral infection called PML, progressive multifocal leukoencephalopathy.   Biogen Idec and Elan are working on an antibody test to the JC virus. The JC virus is detected in 50-60% of adults.  Eleven MS patients treated with Tysabri who developed PML had previous blood samples stored.  All of these patients did have JC virus antibodies in the blood which means that they had been previously been exposed to the virus before developing the brain viral infection PML. 

Further verification of the test will be required.  If you do not have antibodies to the virus, your PML risk should be extremely low if the preliminary result hold true.  There have been 31 cases of PML reported in over 48,000 currently treated patients.

Biogen Idec Inc. at JPMorgan Healthcare Conference Tuesday, January 12, 2010 http://investor.biogenidec.com