Biogen Idec was pleased to announce last week that the FDA has approved an update to the prescription labeling of the drug Tysabri (natalizumab), their monthly IV monoclonal antibody medication for MS. The prescription label now includes information regarding the increased risk of developing progressive multifocal leukoencephalopathy (PML) in patients who test positive for antibodies of the JC virus (JCV). PML is a rare but serious brain infection associated with use of Tysabri and some other medical treatments (including the Rituxan I use for rheumatoid arthritis).
A patient who tests negative for JC virus antibodies and who uses Tysabri may feel like jumping for joy at this negative test result. However, the the FDA stresses that “patients who test negative for anti-JCV antibodies are still at risk for the development of PML due to the potential for a new JCV infection or a false negative test result.” It seems obvious that doctors should consider testing patients prior to beginning treatment or during treatment if the antibody status is unknown. Patients should also consider periodic re-testing for those who previously tested negative for the anti-JCV antibody as a person might later become exposed to the virus.
For the past couple of years, discussions of Tysabri, PML, and the JC virus have been common in the MS community. Medical professionals have known that a reactivation of the JC virus is responsible for the development of PML in some patients. But until now there had not been a commercially-available laboratory test which would reliably test for the presence of anti-JC virus antibodies in a person’s blood. Now available through Quest Diagnostics, the Stratify JCV Antibody ELISA test is manufactured by Focus Diagnostics of Cypress, Calif. The test is for professional use and by prescription only and is to be performed only at Focus Diagnostics’ Reference Laboratory.
Last summer I, along with a small group of MS advocates, spoke with an employee at Biogen Idec who discussed their ongoing STRATIFY II study. The purpose of the study is to define the serological prevalence of JCV Antibody in the MS population and potentially stratify patients into lower or higher risk for developing PML based on antibody status. The Biogen employee suggested that if any of us at the meeting were interested in participating in the study that we should contact our doctors soon as they were about to close the study to new participants.
At my next neurology appointment, I asked to participate in the study and donate a sample of blood. One benefit of participating in the study is that I would learn my JCV antibody status. I tested NEGATIVE!! This was good news, especially since I use a drug which increases one’s risk of developing PML. My blood will be tested again next October and once more in the following year. One thing which will be measured in the study is the number of patients who test negative initially and later test positive.
