A 10th patient taking Biogen Idec's multiple sclerosis drug Tysabri has developed a potentially deadly brain infection since it was reintroduced to the market in July 2006. The drug is developed in conjunction with Ireland's Elan.
The Massachusetts-based biotech company released the news on its website on Friday night. Tysabri is considered critical to the future growth of both companies.
The drug was temporarily withdrawn from the market in 2005 after it was linked with a brain infection known as progressive multifocal leukoencephalopathy, or PML. It was brought back in 2006 with stricter safety warnings.
Sales of the drug have failed to live up to expectations. It generated $227m in the first quarter of 2009, less than the $246m analysts had expected. They expect it to generate $1 billion in sales for the full year.
Elan shares were down two cent at €5.06 in Dublin this afternoon.
