This month, Duke Clinical Research Institute announced the results of a study indicating that glycoprotein IIb/IIIa platelet inhibitor drugs-also known as "super aspirins"-did not significantly benefit most patients with acute coronary syndromes.
However, the researchers, who presented their findings at the American College of Cardiology's annual conference, discovered that a selective use of these drugs may in fact help a specific subset of patients in preventing a second heart attack and even death.
Patients from 29 countries participated in the trial testing the effects of lamifiban, one of three intravenous super aspirins designed to prevent circulating platelets-small, colorless blood cells-from clumping together and forming a clot at the site of the atherosclerotic plaque in coronary arteries.
The drugs are administered to patients who suffer from unstable angina or are at risk for a second heart attack. Two of the super aspirins, eptifibiatide and tirofiban, are already on the market.
The clinical trial, which enrolled 5,225 patients worldwide, found that in overall data, patients in the lamifiban trial showed only a small, statistically insignificant improvement.
Roughly half of the patients were randomly allocated a dose of lamifiban tailored to each individual's weight, gender and kidney function, while half received a placebo. In the double-blind study, patients also received heparin, a blood thinner and regular aspirin.
"The step forward would have been if this dose adjustment made a difference-and it doesn't," said Dr. Robert Harrington, the study's lead investigator and an associate professor in the Division of Cardiology.
At the end of 30 days, 11.8 percent of patients treated with lamifiban had either had a second heart attack, recurrent chest pains or died, compared with the 12.8 percent treated with a placebo.
These findings, however, led to an encouraging discovery. Although, collectively, the platelet inhibitor drugs only produced a slight benefit, a specific group of patients benefited significantly from the lamifiban.
A sub-study helped identify high-risk patients. The researchers found that administering lamifiban to patients that are "troponin T positive" reduces the risk of a second heart attack by nearly 50 percent. When troponin T, a regulatory protein, is found in the blood, it indicates that muscle tissue is dying. "Somewhere between 25 to 40 percent of patients who come in actually have troponin [T]," he said.
Harrington said identifying high-risk patients whose situation is improved by the drug is consequential. "All of the effects of [lamifiban] appear to be in that group. We've learned there is a subset of patients who are at very high risk whom these drugs seem to preferentially benefit," Harrington said.
Dr. Howard Herrmann, professor of medicine and director of interventional cardiology at University of Pennsylvania Health System, said that although the overall trial showed insignificant effects for patients as a whole, the sub-study also reveals an important finding. "I think the study supports the concept that inhibiting the platelets is important in this type of situation."
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