A drug that keeps hemophiliacs (search) from bleeding to death could also prove to be the first treatment for the most lethal and crippling type of stroke, the kind caused by a burst blood vessel in the brain.

In a promising international study, stroke victims given the drug were one-third less likely to die and three times more likely to survive without severe disability.

"What was really startling was how well this drug worked," said Dr. Stephan Mayer, a stroke specialist at the Columbia University Medical Center (search) in New York who led the study. "I was fairly amazed."

The drug needs more study, and Mayer said it will be at least two years before the maker applies for Food and Drug Administration (search) approval for this purpose.

Most of the 700,000 strokes in the United States each year are caused by a clot that cuts off the flow of blood to the brain. Over the past decade, the clot-busting drug TPA (search) has proved extraordinarily effective at treating many of these victims.

But there has been no effective treatment for the 10 percent to 15 percent of strokes caused by bleeding in the brain. More than half of victims die within a year, and only one in five recovers well enough to regain mobility.

Researchers tested recombinant activated factor VIIa, a clot-forming drug sold as NovoSeven since 1999 for hemophilia, against bleeding strokes. The findings were reported in Thursday's New England Journal of Medicine. The study was funded by the drug's maker, Novo Nordisk, and Mayer gets consulting fees from the company.

The study was conducted at 73 hospitals in 20 countries. Researchers assigned 399 patients to get the drug or fake medication. Patients who took the drug within four hours of the onset of a stroke had about half the amount of bleeding in their brain.

After three months, 18 percent of those who took the drug had died, versus 29 percent of those in the comparison group.

The drug had side effects: Seven percent of patients who received it suffered heart attacks or strokes caused by blood clots, compared with 2 percent of those in the comparison group. But most recovered.

"The benefit definitely outweighs the risk," said Dr. Marc Mayberg, chairman of the American Heart Association's Stroke Council. He had no role in the study.

Patients can usually recover from a heart attack with early medical help, but the debilitating effects of a bleeding stroke are often irreversible.

"It is possible that we are on the brink of having a successful targeted treatment," Dr. Devin Brown of the University of Michigan Health System's Stroke Program said in an accompanying editorial.

But Brown noted that the groups in the study were not necessarily equal because researchers did not take into account possible differences in patients' blood pressure, which affects how well they recover from stroke.

Mayer plans to conduct begin a two-year study this summer involving 580 patients. He said the drug could cost $6,000 for a single dose.