The Hurler On The Ditch

The Food and Drug Administration said yesterday that it would allow some patients in a clinical trial to resume treatment with Tysabri, a multiple sclerosis drug that was abruptly withdrawn from the market a year ago because of safety risks.

The decision appears to strengthen the probability that Tysabri, developed by Biogen Idec and Elan, will be allowed to return to the market. The F.D.A. is scheduled to decide on that question by the end of March.

"You can certainly deduce that we've concluded that there are at least some people for whom the risk is worth it," Dr. Robert Temple, director of medical policy for the drug division of F.D.A., said in an interview.

Still, he said, the decision yesterday was to allow the drug to be used only under the controlled conditions of a clinical trial and only by patients who had previously benefited from it in a clinical trial. "That's not at all the same as making it available for marketing," he said.