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Tailoring Use of Platelet Inhibitors.

Researchers at Duke University Medical Center, Durham, N.C., think they know why glycoprotein IIb/IIIa platelet inhibitor drugs, collectively known as "super aspirins," produce only modest benefits for patients with acute coronary syndromes--they are often being used on patients who only can gain very little benefit. In the process of tabulating results on a trial on lamifiban, one of three intravenous super aspirins that have been tested, they discovered that a simple blood test identified patients who benefited markedly when the drug was used. In those individuals, improvement in the risk of death and a second heart attack was about 50%, compared to patients who received a placebo.

In contrast, data on all patients in the lamifiban trial show just a modest, statistically insignificant improvement, similar to that seen in tests of eptifibatide and tirofiban, two other intravenous-use GP IIb/IIIa receptor inhibitors already on the market.

"This is good news. It shows us that we can potentially refine the use of IIb/IIIa inhibitors and direct them to the patients who can really benefit from them," indicates the study's lead investigator, Robert Harrington of the Duke Clinical Research Institute. He maintains that use of the super aspirins in the U.S. is tepid, with only about 15% of eligible patients put on them. "But with this new information, we may have the ability to target the power of these drugs."

The three super aspirins attempt to prevent platelets circulating in the blood from clumping together and forming a clot at the site of atherosclerotic plaque. The drugs are delivered intravenously over a three-day period to patients who suffer from unstable angina or are at risk for a second heart attack. (They are not used on patients who are receiving thrombolytic therapy to break up existing blood clots.) Oral forms of these super aspirins have not shown any benefit over aspirin use.

The Duke Clinical trial enrolled 5,225 patients in 29 countries and gave them either a dose of lamifiban that was tailored to their weight, sex, and kidney function or a placebo. All patients received aspirin and heparin as well. At the end of 30 days, 11.8% of those treated with lamifiban had either a second heart attack, recurrent ischemia, or died, compared to 12.8% treated with a placebo. "This is a lukewarm response," Harrington notes.

The research team then conducted a substudy to look at which patients were most at risk and obtained blood samples for further analysis. As part of the analysis, they looked at the level in patients' blood of a protein known as troponin T, which is a marker of dying muscle tissue. It is a regulatory protein that helps heart muscle contract and, once this muscle starts dying, cell membranes break down and internal cellular material, including proteins, is released and carried away by the blood. A test that measures troponin levels is available, and previous studies have indicated that 25-40% of typical unstable angina patients test positive when they are admitted into the hospital, Harrington says.

Of the patients in the study who had a positive troponin level at admission, 11% had an adverse event within 30 days when treated with lamifiban, compared to 19.4% treated with a placebo. That's a 49% reduction, Harrington indicates. "This shows us that troponin T-positive patients are at much increased risk of adverse events, and that they are also the patients who benefit most from what lamifiban or other GP IIb/IIIa drugs can offer"
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Title Annotation:research into super aspirins
Publication:USA Today (Magazine)
Article Type:Brief Article
Geographic Code:1USA
Date:Oct 1, 2000
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