MS drug linked to 31 cases of brain illness
Biogen Idec's and Elan's multiple sclerosis (MS) drug Tysabri has been linked to 31 cases of a deadly brain infection and eight deaths since it returned to the market in 2006, US regulators said.
That number of infections and deaths won't change the one in 1,000 infection rate currently on the drug's label, the US Food and Drug Administration (FDA) said yesterday.
The prescribing information will be updated, including a new comparison with infection rates overseas.
Tysabri, cleared for sale in 2004, was temporarily recalled in February 2005 after the drug was linked to progressive multifocal leukoencephalopathy (PML) infections.
About 48,800 patients were taking Tysabri as of the end of January, Biogen said last month. The medicine is Massachusetts-based Biogen's fastest-growing product, with 2008 sales of $588.6m (€432m).
"There have been no reports in patients treated for less than 12 months since Tysabri's re-marketing," the FDA said. After 24 to 36 infusions, the worldwide PML rate is one case per 1,000 patients.
The rate of PML infection is higher outside the US, with two of every 1,000 patients on therapy contracting the illness. The reason for the difference is unknown, the FDA said.
"We think that heavy use of prior immunosuppressants is a risk factor," said Naomi Aoki, a Biogen spokeswoman.
"That's the one thing we've seen as a difference that seems like it might be contributing, but we're not really sure."
Dublin-based Elan's spokeswoman, Niamh Lyons, did not immediately return a call seeking comment.
About 66,000 people worldwide have taken at least one dose of Tysabri from June 2006 through December 31, 2009.