New studies have confirmed that testing positive for anti-JC virus (JCV) antibodies is a risk factor for progressive multifocal leukoencephalopathy (PML), a rare brain infection that has been associated with the multiple sclerosis drug Tysabri (natalizumab). Signs and symptoms of PML include headaches, loss of coordination, memory loss, and progressive weakness in the arms and legs. The risks and benefits of taking Tysabri should be carefully considered in patients who are found to be anti-JCV antibody positive and have one or more of the other known risk factors of progressive multifocal leukoencephalopathy.
What’s the problem?
January 20, 2012 – An individual’s anti-JCV status may be determined by using the Stratify JCV Antibody ELISA test2, which was cleared for use today by the U.S. Food & Drug Administration (FDA). Testing positive for anti-JCV antibodies means that the patient has been exposed to JCV at some point in the past.
Tysabri belongs to a class of drugs known as immunomodulators that are designed to work by stopping cells in the immune system from causing damage to the body. The drug was approved by the FDA for the treatment of multiple sclerosis in November 2004, and for Crohn’s disease in January 2008.
The FDA is recommending that the risks and benefits of using Tysabri be carefully considered by individuals who are anti-JCV antibody positive, and have one or more of the other known risk factors for progressive multifocal leukoencephalopathy. According to the administration, patients with all three known risk factors have an approximate risk of PML of 11/1,000 users.
Progressive Multifocal Leukoencephalopathy (PML)
Progressive multifocal leukoencephalopathy is a rare disease that destroys the protective covering (myelin) in the white matter of the brain. PML is most often found in patients undergoing chronic corticosteroid or immunosuppressive therapy for organ transplant, in patients with Hodgkin’s disease, lymphoma, or human immunodeficiency virus (HIV). Signs and symptoms of Tysabri-induced progressive multifocal leukoencephalopathy may include:
- loss of coordination, clumsiness
- loss of language ability (aphasia)
- memory loss
- vision problems
- weakness of the legs and arms that gets worse
Progressive multifocal leukoencephalopathy usually has a mortality rate between 30 and 50 percent in the first few months following the initial diagnosis, but the long-term prognosis depends heavily on the severity of the underlying disease and the effectiveness of treatment received. Unfortunately, many of the patients who survive PML are left with severe lifelong neurological disabilities.