The FDA notified healthcare professionals that testing positive for anti-JC virus (JCV) antibodies has been identified as a risk factor for progressive multifocal leukoencephalopathy (PML). PML is rare but serious brain infection associated with the use of Tysabri (natalizumab) for the treatment of multiple sclerosis (MS) or Crohn’s disease.
PML is a rare but serious viral brain infection that is characterized by progressive damage or inflammation of the white matter of the brain at multiple locations. Signs and symptoms of PML may develop over the course of several weeks or months and may include changes in mood or usual behavior, confusion, thinking problems, memory loss, changes in vision, speech, or walking, and decreased strength or weakness on one side of the body.
A patient’s anti-JCV antibody status may be determined using an anti-JCV antibody detection test. Testing positive for anti-JCV antibodies means that a person has been exposed to JCV in the past.
Tysabri (natalizumab) belong to a class of medications called immunomodulators, which function by stopping certain cells of the immune system from causing damage to the body. Tysbari is approved for treatment of relapsing forms of multiple sclerosis since November 2004 and for the treatment of moderately to severely active Crohn’s disease since January 2008.
The risks and benefits of continuing treatment with Tysabri should be carefully considered in patients who are found anti-JCV antibody positive and have one or more of the other known risk factors for PML. Patients with all three known risk factors have an estimated risk of PML of 11/1,000 users.