BOSTON (AP) _ The makers of Tysabri, a new drug used to treat multiple sclerosis, announced Monday they are voluntarily suspending sales of the drug after one patient died and another developed a serious disease of the central nervous system.
Stocks of both Biogen Idec Inc. and Elan Corp. tumbled in premarket trading.
The companies said in a news release that they have suspended supplying and marketing the drug and advised doctors to suspend prescribing it. The companies also have stopped using the drug in clinical trials.
The Food and Drug Administration approved Tysabri, which was called Antegren during clinical trials, in November in an accelerated process after a late-stage study showed that it reduced MS relapses by 66 percent compared with a placebo.
The companies said the decision came after recent reports of two cases of serious effects among patients who used the drug along with Avonex, Biogen Idec's older MS treatment, in clinical trials. A study had showed that it improved the performance of Avonex significantly compared with Avonex alone.
In one case, the patient died, while in another, the person developed a suspected case of a rare, frequently fatal disease of the central nervous system called progressive multifocal leukoencephalopathy.
Both patients had taken Tysabri for more than two years in combination with Avonex, the companies said.
``Because we believe in the promising therapeutic benefit of Tysabri, we are working to evaluate this situation thoroughly and expeditiously,'' said Dr. Burt Adelman, executive vice president of Development at Biogen Idec. ``While we work through this matter, we must place patient safety above all other considerations.''
The companies said they took the action after consulting with the FDA.