Cangrelorは一次エンドポイントでは有益性を示さなかったがいくつかの二次エンドポイントにおいては有意な結果を示した

A new reversible blood thinner for angioplasty patients wasn't superior over placebo for its primary combined endpoint of heart attack, all-cause mortality and need for revascularization, but it reduced mortality and in-stent blood clots, researchers reported in a late-breaking clinical trial presentation at the American Heart Association's Scientific Sessions 2009.

CHAMPION PLATFORM, a phase III trial, included 5,362 angioplasty-plus-stent patients randomized to receive either a placebo or the investigational drug cangrelor during procedures to reopen coronary artery blockages. Cangrelor is a potent, fast-acting and reversible anti-clotting drug delivered intravenously.

After their procedures, all patients received 600 milligrams (mg) of the oral, nonreversible anti-clotting drug clopidogrel, which is routinely used in such procedures.

The trial, which enrolled patients beginning in 2006, ended when an interim review committee concluded that cangrelor would fail to show superiority over clopidogrel for its primary endpoint: a composite of all-cause death, heart attack and the need for coronary revascularization procedures.

"There was no statistically significant difference between the two arms of the trial at our 48-hour endpoint," said Deepak L. Bhatt, M.D., M.P.H., chief of cardiology at the VA Boston Healthcare System. "However, a number of secondary endpoints had very interesting and informative findings. For instance, all-cause death as a stand-alone endpoint was reduced significantly from 0.7 percent in controls to 0.2 percent (67% reduction) in the cangrelor group.

"It is intriguing, of course, but it is a secondary endpoint and needs to be interpreted with some caution given that the primary endpoint was not met and the number of deaths overall was low."

Furthermore, acute stent thrombosis was significantly reduced in the test group.

"That's something that interventional cardiologists really worry about because stent thrombosis is often associated with a recurrent heart attack or death," said Bhatt, who is also director of the integrated interventional cardiovascular program at Brigham and Women's Hospital and the VA Boston Healthcare System and a faculty member at Harvard Medical School in Boston, Mass. "Acute stent thrombosis was reduced from 0.6 percent in controls to 0.2 percent in the test group (69% reduction), again a significant benefit. So there seems to be a plausible mechanism by which mortality may have been reduced since stent thrombosis was reduced."

Researchers found no difference in endpoints between test and control groups for severe bleeding and need for blood transfusion. However, less severe bleeding was significantly higher with the new agent, 5.4 percent vs. 3.4 percent in controls, an indication of the investigational drug's potency, Bhatt said. Because it's reversible and is delivered through an intravenous line, bleeding events can be ended quickly after the drug is no longer administered.

Clopidogrel is given orally and is irreversible - once it binds to a platelet it remains for the life of that blood cell, usually 7 to 10 days. That puts clopidogrel patients at higher risk of bleeding complications if they need emergency surgery, he said.

"At least in theory, cangrelor has all the attributes that an interventional cardiologist would want: Its onset of action is very quick and it's very potent, but on the back end you can turn it off," Bhatt said.

The Medicines Company funded the study.

Co-authors of the study are the CHAMPION executive committee members.

isclosure: Dr. Bhatt receives grant support from the study sponsor.