FDA Update on Brain Infection Risk with Tysabri


Tysabri (natalizumab) is known to put patients at risk of developing progressive multifocal leukoencephalopathy (PML). The drug was pulled off the market in 2004 soon after it was introduced into the market, then placed back on the market in 2006 because there are so few good options for Multiple Sclerosis (MS) patients.

This week the FDA notified healthcare professionals and patients that the risk of developing PML increases with the number of Tysabri infusions received. There have now been 31 confirmed cases of PML as of January 21, 2010. This new safety information will now be included in the Tysabri drug label and patient Medication Guide.

The updated drug label will also include information about the occurrence of Immune Reconstitution Inflammatory Syndrome (IRIS) in patients who have developed PML and subsequently discontinued Tysabri. IRIS is a rare condition characterized by a severe inflammatory response that can occur during or following immune system recovery, causing an unexpected decline in a patient’s condition after return of immune function.


Based on the available information, FDA believes that the clinical benefits of Tysabri continue to outweigh the potential risks. Revisions to the drug label and patient Medication Guide, with the continued use of the TOUCH Prescribing Program, are intended to maximize the safe use of Tysabri and the identification of new PML cases.

Patients with Multiple Sclerosis (MS), an auto-immune disease in which the body mistakenly attacks the fatty myelin coating surrounding nerve cells, must be enrolled in the TOUCH program to receive Tysabri. Enrollment begins with an appointment with a prescribing neurologist where the enrollment form is filled out/signed. The neurologist should explain the potential benefits and risks of TYSABRI treatment, giving the patient time to ask any questions. Upon signing the TOUCH Enrollment Form, the patient is assigned an identification number by Biogen Idec.

The TOUCH Prescribing Program includes a checklist of questions that should be reviewed and answered prior to each infusions. This is meant to help catch changes in the patients health which would make the risk of infusion too great.

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FDA News Release