There has been another case of a rare brain disease in a patient who had been taking Tysabri, withdrawn in February after a patient suffered a fatal reaction to the drug, once seen as having major potential for treating multiple sclerosis.
The latest discovery makes it highly unlikely the drug will return to the market, analysts said.
Tysabri is sold in the U.S. by Biogen Idec Corp. and Elan Corp., based in Ireland.
The companies said the latest case involved a patient who died in 2003. The patient had been participating in a clinical trial of Tysabri and the death had originally been attributed to a different condition.
The patient was taking Tysabri in a trial to test its effectiveness for Crohn's disease, an intestinal illness. The new diagnosis was made in recent days by a pathologist who re-examined the patient's brain tissue.
An Elan spokeswoman said the company's goal was "to bring Tysabri back to patients if and when appropriate."
