The Food and Drug Administration ( FDA ) issued a public health advisory to inform patients and health care providers about the suspended marketing of Tysabri ( Nataluzimab ) while the agency and the manufacturer evaluate two serious adverse events reported with its use.

Tysabri, which received accelerated approval from FDA in November 2004, is an innovative treatment that represents a new approach to treating patients with relapsing forms of multiple sclerosis .

“ FDA continues to believe Tysabri offers great hope to MS patients, " said Dr. Steven Galson, Acting Director, FDA's Center for Drug Evaluation and Research ( CDER ).

FDA received a report from Biogen Idec, the manufacturer of Tysabri, of one confirmed fatal case and one possible case of progressive multifocal leukoencephalopathy ( PML ) in patients receiving Tysabri for multiple sclerosis.

PML is a rare, serious progressive neurologic disease usually occurring in immunosuppressed patients.
There is no known effective treatment for PML.

Although the relationship between Tysabri and PML is not known at this time, because of the serious and often fatal nature of PML, FDA concurred with the company that the drug be voluntarily withdrawn from marketing and that the use of Tysabri in clinical trials be suspended until more is known.

During the review of Tysabri for marketing approval, FDA conducted an intensive analysis of possible adverse events that might be related to effects of the drug on the immune system.
No cases of PML were seen in the clinical trials.

According to Biogen Idec, outside of the approximately 3,000 patients who received the drug in clinical trials, approximately 5,000 additional patients with multiple sclerosis have received Tysabri through their primary physician.
Because Tysabri was just recently approved, these patients have only received at most a few doses of Tysabri.

Source: FDA,2005

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