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FDA Confirms 13 Cases of PML with MS Drug
By Peggy Peck, Executive Editor, MedPage TodayPublished: September 17, 2009

WASHINGTON -- The FDA said it has confirmed 13 cases of progressive multifocal leukoencephalopathy (PML) in patients receiving natalizumab (Tysabri) monotherapy for multiple sclerosis.
Four of the cases were patients in the U.S.
The FDA said there have been no confirmed cases in patients receiving natalizumab for Crohn's disease, an indication the FDA approved in January 2008. But in its safety update, the FDA noted that less than 2% of natalizumab use in the U.S. has been for Crohn's patients.
The FDA is not changing natalizumab labeling or prescribing information, or altering the TOUCH prescribing program, which is a risk management effort that oversees all natalizumab prescribing in the U.S.
A paper published online last week by the New England Journal of Medicine put the total number of PML cases at 14, but that paper included cases reported since November 2004, when natalizumab was first approved for treatment of relapsing forms of MS.
When reports of PML surfaced in 2005 the drug was withdrawn and was then reintroduced in July 2006.
The FDA said the risk for developing PML appears to increase with the number of natalizumab infusions received. The 13 patients who developed PML received an average of 12 to 35 monthly infusions per patient. The average number of infusions received before the diagnosis of PML was 25.
Among patients who have received at least one natalizumab infusion, the overall rate of developing PML was less than one case per 1,000.
"Based on available data from the U.S. and outside of the U.S., the current rate of PML in patients who have received at least 24 infusions ranges from 0.4 to 1.3 per 1,000 patients," the FDA said.