Today, the U.S. Food and Drug Administration allowed marketing of the first test to help determine the risk for a rare brain infection called progressive multifocal leukoencephalopathy (PML) in people using the drug Tysabri (natalizumab) to treat multiple sclerosis (MS) or Crohn's disease (CD).
The Stratify JCV Antibody ELISA test, when used with other clinical data from the patient, can help health care providers determine the risk for developing PML in MS and CD patients.
The John Cunningham virus (JCV) is a common virus that many people have been exposed to at some point in their lives, and is generally harmless. However, people with weakened immune systems, such as patients using immunomodulatory therapies like Tysabri, have an increased chance of developing PML from JCV. PML usually causes death or severe disability.
Currently, there is no treatment, prevention, or cure for PML, and no certain way to predict who will develop it. This test in conjunction with other factors listed below will allow the physicians and patients to carefully assess the risks and benefits of continuing Tysabri treatment depending on the complete clinical information for the particular patient. The following risk factors have been identified that increase the chance of Tysabri-treated patients developing PML:
- the presence of anti-JCV antibodies, which reflects prior exposure to JCV
- treatment with Tysabri for a significant period of time (longer than 2 years)
- treatment with certain medicines that can weaken a patient's immune system (immunosuppressants such as mitoxantrone, azathioprine, methotrexate, cyclophosphamide, and mycophenolate mofetil) before receiving Tysabri.
The risk of getting PML is greatest (about 11/1000 patients treated) if the patient has all three of these risk factors.
"PML is a fatal infection reported in patients undergoing immunomodulatory therapy," said Alberto Gutierrez, Ph.D., director of the Office of In Vitro Diagnostics in FDA's Center for Devices and Radiological Health. "This test gives doctors an additional means to determine if MS or CD patients undergoing Tysabri therapy are at increased risk for developing PML."
The FDA reviewed data for the Stratify JCV Antibody ELISA test through the de novo reclassification process, a regulatory pathway for low- to moderate-risk medical devices that are novel and not comparable to an already legally marketed device.
In a separate action, the FDA also announced updates to the drug label for Tysabri. The change includes information that testing positive for anti-JCV antibodies is a recently identified risk factor for developing PML in patients treated with Tysabri for MS or CD.
The Stratify JCV Antibody ELISA test should not be used on its own as a basis for determining the risk for developing PML in patients on immunomodulatory therapy or for making clinical decisions. The test cannot be used to diagnose PML.
The test is for professional use and by prescription only and is to be performed only at Focus Diagnostics' Reference Laboratory. The test is not intended for blood donor screening. The performance of this test has not been established for use in neonates, pediatric patients or any other immunocompromised patient populations.
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