At the annual meeting of the European Society of Cardiology today, scientists from the Duke Clinical Research Institute (DCRI) are announcing promising results from a small Phase I trial of a new type of drug to prevent blood clots. Many current anticoagulants act on a clotting factor called thrombin. But the new drug, dubbed DX-9065a, acts earlier in the chain of biochemical events that lead to clot formation in the body. DX-9065a inhibits the action of Factor Xa, which itself normally converts prothrombin in the blood into thrombin. "Because of its location in the cascade, Factor Xa has long been seen as an attractive target for anticoagulation therapy," DCRI senior cardiologist Christopher Dyke says. The researchers hope the drug may present fewer complications than current treatments.

Unlike most Phase I trials, which test a drug's safety on healthy volunteers, this trial looked at DX-9065a's effects in 73 patients with clinically stable coronary artery disease at 10 U.S. academic medical centers. The subjects were 63 years old, on average. Some 68 percent had had a prior heart attack, and 86 percent had undergone either angioplasty or a coronary artery bypass surgery. Over the course of the study, they received a placebo or one of four different doses of DX-9065a. "We found no statistically significant difference in bleeding complications among all five groups," Dyke says. "Also, there were no adverse changes in kidney or liver function, and the hemoglobin and platelet counts remained stable across all groups."

The scientists are cautiously enthusiastic about these results. "This is truly the first experience in real patients who have coronary artery disease with a novel class of drug, so it is a pretty important step moving along our knowledge of anticoagulation therapy," DCRI's Robert Harrington notes. "Even if this proves to be a modest advance, modest steps forward in treating a disease that effects millions of people every year is pretty good. Larger trials will be required to give us the answer as to whether these are steps forward in reducing blood clotting while minimizing bleeding." To answer those questions, two Phase II trials are already underway.