ARTICLE | Clinical News

Tysabri patient with PML tests negative for anti-JCV antibodies

July 16, 2011 12:37 AM UTC

Biogen Idec Inc. (NASDAQ:BIIB) said one patient receiving autoimmune drug Tysabri natalizumab monotherapy who was diagnosed with progressive multifocal leukoencephalopathy tested negative for anti-JCV antibodies, which are believed to be a risk factor for developing PML. The company said the patient was tested within 24 hours of receiving plasma-exchange (PLEX) therapy, which removes large molecules from the patient's blood to facilitate the removal of Tysabri and improve the immune system's response to PML infection. The patient was not tested for anti-JCV antibodies prior to receiving PLEX, nor did the company have any information on the patient's baseline anti-JCV antibody levels. The company added that internal research indicates that PLEX therapy reduces anti-JCV antibody levels by 2-5 fold.

Biogen Idec said it has no information on whether the patient's anti-JC virus antibody status has been or will be retested. The company said the decision to test for anti-JCV antibodies prior to receiving PLEX is made by the treating physician. ...