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New Drug May Act Sooner to Prevent Blood Clots

Side effects not a problem in early tests

WEDNESDAY, Sept. 5, 2001 (HealthDayNews) -- A new kind of clot-preventing drug that promises to be safer and more effective for people with heart disease has passed its first test on human subjects, report Duke University cardiologists.

The drug differs from existing ones because it acts at the beginning of the molecular chain of events that leads to the formation of blood clots, explains Dr. Christopher Dyke, a senior cardiology fellow at the Duke Clinical Research Institute. He reported on the trial today at the annual meeting of the European Society of Cardiology in Stockholm.

The new drug -- called anti-Xa, pronounced "anti-10a" because the X is the Roman numeral for 10 -- gets its name because it inhibits the action of factor Xa, a molecule that starts the clotting process. Factor Xa converts a blood chemical called prothrombin into thrombin, a molecule that plays the pivotal role in creating the blood clots that are needed to stop bleeding but can be dangerous to people with narrow or damaged arteries. Existing drugs act later in the process, generally after thrombin is formed.

"The potential benefit of this class of drugs is that they provide a more efficacious background therapy, because of where it inhibits the clotting cascade, before thrombin is generated," Dyke says.

The problem with anti-clotting therapy is that current medications require extremely careful dosing because too little can allow clots to form and too much can cause unwanted bleeding. Experts hope that anti-Xa will allow a wider dosage range.

The study Dyke reported at the meeting was a small one, involving 73 people with stable coronary artery disease at 10 American medical centers. "What the study set out to do was to define the safety profile of a novel class of drugs," Dyke says. Participants were divided into five groups. Four got different doses of anti-Xa and the fifth got a placebo, an inactive substance.

"The drug was well tolerated," he says, adding that participants experienced no significant difference in bleeding complications and showed no indications of kidney or liver problems.

More than 100 people already have been enrolled for a larger test using anti-Xa to prevent problems during angioplasty, the artery-widening procedure. A third test is being planned for more than 400 people with unstable angina, the chronic pain that is a major risk factor for heart attacks. All of the studies, funded by the Daiichi Pharmaceutical Company, the Japanese firm that developed the drug, will test anti-Xa against heparin, a standard anti-clotting agent

Dr. Robert Harrington, an assistant professor of medicine at Duke and one of the senior researchers for the first human tests, describes the study as "a pretty important step," but says it's just a first step.

"Larger trials are needed to give us the answer as to whether these are steps toward reducing blood clotting while minimizing bleeding," Harrington says.

What To Do

It's early in the research game for the new medication, so people who need an anti-clotting drug because they have chronic heart disease or require angioplasty should continue to follow orders about taking their medication.

For primers on blood clots, check out offerings from the National Library of Medicine and Boston University's Community Outreach Health Information System.

SOURCES: Interviews with Christopher Dyke, M.D., senior cardiology fellow, Duke Clinical Research Institute, Durham, N.C.; and Robert Harrington, M.D., assistant professor of medicine, Duke University Medical Center, Durham, N.C.
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