s Committee for Medicinal Products for Human Use, known as CHMP, reported 23 cases of progressive multifocal leukoencephalopathy, or PML, a number that the Food and Drug
Administration later confirmed, adding that those cases were after
Tysabri returned to the market in 2006. The FDA said it is continuing to assess the situation.
A Biogen spokeswoman, citing company policy, declined to comment on the number of PML cases.