FDA: Tysabri users may have increased risk of developing deadly brain infection

NEW YORK New cases of a deadly brain infection have turned up in patients using a multiple sclerosis drug.

The Food and Drug Administration announced late last week that several patients using the drug Tysabri (natalizumab) had developed progressive multifocal leukoencephalopathy. Also known as PML, the disease results from a brain infection caused by the JC virus, which is present in most adults but kept in check by the immune system. PML most often occurs in patients with advanced AIDS and those taking some immunosuppressant drugs, causing irreversible decline in brain function and death.

Tysabri, made by Elan Corp. and Biogen Idec, is approved for treating MS and Crohn’s disease, though no cases of PML have occurred in Crohn’s disease patients. The FDA approved the drug in 2004, but has confirmed 13 cases of PML worldwide in patients using it, though the FDA said it would not require changes to Tysabri’s prescribing information or risk management plan.