Tysabri has been linked to a rare condition called progressive
multifocal leukoencephalopathy (PML), where the white matter in the brain
becomes inflamed. The drug was taken off the market briefly following its 2004
Food and Drug Administration approval, when it was linked to three deaths from
PML.
Tysabri was allowed back on the market in 2006 after no other cases
had been identified.
In a regulatory filing late Thursday, Biogen and Elan said they've
notified regulatory agencies Friday that they recently received notifications of
two diagnoses of PML in multiple sclerosis patients "in the European Union."
The companies said they will host a conference call Friday to
discuss the matter.
Biogen and Elan earlier this month announced that Tysabri was being
used on more than 31,800 patients as of the end of June, two years after the
drug was re-launched following a safety recall.
See
related story. Tysabri was withdrawn from the market in Feb. 2005, just three
months after its launch in the U.S.
Earlier this week, Elan reported that study results for its
Bapineuzumab Alzheimer's disease drug provided mixed results, sending its shares
sharply lower.
