The FDA has notified healthcare professionals and patients that the risk of developing progressive multifocal leukoencephalopathy (PML) increases with the number of Tysabri (natalizumab, from Biogen Idec) infusions received. This new safety information, based on reports of 31 confirmed cases of PML, will be included in the Tysabri Prescribing Information and the patient Medication Guide. The Tysabri labeling will also include information about the occurrence of immune reconstitution syndrome (IRIS) in patients who have developed PML.

Tysabri is indicated to reduce the frequency of clinical exacerbations and delay accumulation of physical disability in relapsing forms of multiple sclerosis (MS). It is also indicated in moderately-to-severely active Crohn's disease: to induce and maintain clinical response and remission in adult patients with evidence of inflammation who have had inadequate response to or are intolerant to conventional therapy and TNF-α inhibitors.

For more information visit www.fda.gov/Safety/MedWatch/SafetyInformation/SafetyAlertsforHumanMedicalProducts/ucm199965.htm.