Annals of Long Term Care

On January 20, 2012, the FDA allowed marketing of the first test to help determine the risk of progressive multifocal leukoencephalopathy (PML) in patients taking Tysabri (natalizumab) to treat multiple sclerosis (MS) or Crohn’s disease (CD). Currently, there is no treatment, prevention, or cure for PML, a disease of the white matter of the brain that usually causes death or severe disability. There is no certain way to predict who will develop PML, but the disease is thought to be caused by the John Cunningham virus (JCV), which targets cells that make myelin, the material that insulates nerve cells. People with weakened immune systems, including those using immunomodulatory therapies such as Tysabri, are at higher risk of developing PML from JCV.

FDA researchers hope that the new test—Stratify JCV Antibody ELISA (enzyme-linked immunosorbent assay)—when used with other clinical data from patients, will help healthcare providers assess the risks and benefits of continuing Tysabri in patients with MS or CD. Risk factors for PML include: the presence of anti-JCV antibodies, indicating previous exposure to JCV; treatment with Tysabri for longer than 2 years; and treatment with other immunomodulatory medications before receiving Tysabri. The test is manufactured by Focus Diagnostics, Cypress, CA.