It may be possible to make an early diagnosis of a deadly infection linked to the multiple-sclerosis drug Tysabri and to stop treatment in time to allow patients to recover.

Dublin-based Elan's American depositary receipts closed up 77 cents, or 12 percent, at $7.37 on the New York Stock Exchange. Biogen shares closed up $1.78, or 5.3 percent, at $35.13.

Deadly Infection

Doctors at Biogen in Cambridge, Mass., said in the medical journal that it may be possible to make an early diagnosis of a deadly infection linked to the drug and stop Tysabri treatment in time to allow patients to recover.

Tysabri was pulled from the market earlier this year after two patients from clinical trials were diagnosed with progressive multifocal leukoencephalopathy, or PML, a debilitating and often deadly brain infection. One of those patients died, and a third, who had taken part in testing the drug for Crohn's disease and died, also was later found to have had PML.

The drug had won accelerated approval from the Food and Drug Administration and had been expected to be a blockbuster. The companies' shares have slipped dramatically in the past few months.

Need for a New Therapy

"We continue to believe it is still possible that Tysabri will be back on the market, given the strength of the efficacy data in MS patients and the need for a new therapy," said Elise Wang, an analyst at Smith Barney Citigroup, in a research note.

Wang said Tysabri likely will carry a "black box" warning if it is brought back, which could limit its sales.

Citigroup Global Markets is a market maker in Biogen's stock and owns 1 percent or more of the company's shares. It couldn't immediately be determined if Wang owns shares.

The New England Journal of Medicine posted the comments online as part of a group of reports and editorials about Tysabri. The journal published them early after a report last week that a fourth patient on the drug may have developed PML.