The data monitoring committee of the AVERROES study, seeing overwhelming evidence of the success of apixaban in the prevention of stroke in patients with atrial fibrillation who are unsuitable for the conventional treatment of warfarin, has recommended early termination of this study. The decision came after repeated review and careful consideration of all efficacy and safety data.
The study leaders, principal investigator Dr. Stuart J. Connolly, chairman of the steering committee Dr. Salim Yusuf, and project officer Dr. John Eikelboom, have accepted this recommendation, as have the study sponsors, Bristol-Myers Squibb and Pfizer.
Results of the study were presented by Connolly at the annual European Society of Cardiology Congress in Stockholm, Sweden, on August 31.
The AVERROES study enrolled 5,600 patients with atrial fibrillation at risk for stroke who were unsuitable for therapy with a Vitamin K antagonist such as warfarin. These patients were randomized, double-blind, to receive either apixaban or the standard therapy which is Aspirin. The primary efficacy outcome of the AVERROES study was a composite of stroke or systemic embolism and the major safety outcome was major bleeding.
The data monitoring committee observed a relative risk reduction for stroke and systemic embolism of more than 50 per cent, which was highly statistically significant and which met the highly conservative monitoring boundaries of the AVERROES study. There was only a modest increase in major hemorrhage that was not statistically significant.
"The results of AVERROES are truly impressive," said Connolly, a professor of medicine at the Michael G. DeGroote School of Medicine at McMaster University. "The reduction in stroke and systemic embolism is very important and the increased risk of hemorrhage is small. It appears that apixaban will be an excellent treatment for the many patients with atrial fibrillation who are unsuitable for warfarin. These findings will reduce the burden of stroke in society."
Atrial fibrillation is a common heart rhythm disorder, in which the upper chamber of the heart beats improperly. Patients with atrial fibrillation are at increased risk of stroke due to the formation of blood clots in the upper chamber of the heart. The standard therapy for the prevention of stroke and other embolic events in atrial fibrillation is to use a type of anticoagulant known as a Vitamin K antagonist. The most common Vitamin K antagonist is warfarin, which is very effective for reducing stroke but is a difficult drug to use because of numerous interactions with food and other drugs and due to a need for long-term monitoring each patient's blood coagulation.