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Anti-Clotting Agent Buys Time For Heart Specialists Drug Crafted Like Snake Venom Could Prevent 10,000 Deaths

Tue., March 18, 1997

A new anti-clotting agent modeled after snake venom could prevent as many as 40,000 heart attacks and 10,000 deaths each year if it were used routinely, researchers reported Monday.

The new drug, tirofiban, reduces heart attacks and deaths by half in patients with so-called unstable angina, the most common cause of hospital admissions in the United States, physicians told a meeting of the American College of Cardiology in Anaheim.

Such patients come to emergency rooms with all the symptoms of a heart attack, but their coronary vessels are not completely clogged and they do not require clot-busting drugs such as tPA.

Untreated, many of these people would have heart attacks. With the best available blood-thinning therapy now - aspirin and heparin - nearly one in 10 has a heart attack during his or her hospital stay.

Administration of the new drug, along with aspirin and heparin, prevents the clot from growing any larger, reducing the risk of a heart attack and giving physicians time to decide if angioplasty or bypass surgery is necessary.

“This is a breakthrough study,” said Dr. H. Vernon Anderson of the University of Texas in Houston. “To reduce deaths by 50 percent is very dramatic. This drug gives us a great opportunity to make meaningful reductions in the number of heart attack deaths.”

Representatives of Merck & Co., which manufactures the drug under the trade name Aggrastat, said the company plans to apply to the Food and Drug Administration later this year for permission to market the drug.

Centocor representatives said Monday that previously unreported results from their own clinical trial show that ReoPro gives at least as good a benefit in unstable angina as tirofiban.

In treating unstable angina, the anti-clotting drugs would be used almost as soon as the patient shows up at the hospital. Tirofiban “buys time” for heart specialists to determine the best treatment for the patient, said molecular biologist Rick Sax of Merck, who developed the drug.

Dr. Harvey D. White of Green Lane Hospital in Auckland, New Zealand, who headed one of the two studies presented Monday, estimated that tirofiban could save 13 lives per 1,000 unstable angina patients. The widely touted tPA, in contrast, saves 10 lives per 1,000 heart attacks.

Most heart attacks and deaths in the 1.25 million Americans who suffer unstable angina each year occur when blood platelets aggregate into a clot in a blood vessel leading to the heart, impeding blood flow or completely blocking it. Researchers know of at least 90 different biological pathways through which clots can build up. Aspirin, one of the most effective clot-preventers, blocks only one of those 90 pathways and heparin is little better.

Looking for better agents, researchers turned to snake venom. When they bite, poisonous snakes inject a very effective anti-clotting agent that allows their venom to spread throughout the victim’s body. Tirofiban, Sax said, is a “designer molecule” that incorporates some of the best features of snake venom, while eliminating those that cause adverse effects. It blocks all 90 pathways to clotting, he added.

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