In a Drug Safety Communication issued Tuesday, the U.S. Food and Drug Administration warned that the multiple sclerosis drug Gilenya was linked to two cases of rare brain infection. One definite case of progressive multifocal leukoencephalopathy (PML) and one probable case of PML were reported in patients taking the drug, the agency said. The label on Gilenya is being revised to include this information, as these are the first PML cases linked to Gilenya patients not taking immunosuppressants.
This is not the first time PML has been reported in a Gilenya patient. In August 2013, the FDA reported that a patient taking Gilenya developed PML. Since the patient had been taking immunosuppressant drugs prior to treatment, however, PML could not be definitively linked to Gilenya.
Gilenya is used to treat patients with relapsing forms of MS, where symptoms worsen for periods of time. The cause of PML is the John Cunningham (JC) virus, which is harmless in most people. In individuals with weakened immune systems, such as those taking immunosuppressants, however, the JC virus can cause PML. Gilenya patients should seek medical attention immediately if they experience symptoms such as new or worsening weakness; increased trouble using their arms or legs; or changes in thinking, eyesight, strength, or balance.