The FDA has updated the Tysabri (natalizumab; Biogen Idec) labeling to provide new information about the size of the risk of progressive multifocal leukoencephalopathy (PML) associated with use of Tysabri for the treatment of multiple sclerosis and Crohn’s disease. The revised label includes a table summarizing the rates of PML with Tysabri use according to the number of infusions. Additionally, the labeling now includes data demonstrating that patients who received immunosuppressant therapy (eg, mitoxantrone, azathioprine, methotrexate, cyclophosphamide, mycophenolate) prior to taking Tysabri are at an increased risk for developing PML. The Tysabri labeling already warned that using immunosuppressants at the same time as Tysabri may increase the risk of developing PML.

Healthcare professionals are advised to monitor their patients for symptoms suggestive of PML (eg, progressive weakness on one side of the body or clumsiness of limbs; disturbance of vision; and changes in thinking, memory and orientation, leading to confusion and personality changes). Based on the available information, the FDA believes that the clinical benefits of Tysabri continue to outweigh the potential risks.

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