ESC: Apixaban trial stopped, cuts AF stroke risk in half

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Members of the AVERROES trial data monitoring committee ordered that the trial be halted after interim results found a 50 percent stroke reduction for apixaban (Bristol-Myers Squibb/Pfizer) compared to aspirin in patients with atrial fibrillation (AF) who were not suitable for warfarin, according to a presentation during the European Society of Cardiology (ESC) congress Aug. 31 in Stockholm.

Apixaban, an anticoagulant known as a factor Xa inhibitor, works to block the coagulation system and has been shown to decrease the symptoms of deep vein thrombosis after acute coronary syndrome in previous clinical trials.

The AVERROES (Apixaban versus Acetylsalicylic Acid to Prevent Strokes) trial results, presented by lead investigator Stuart J. Connolly, MD, from McMaster University in Hamilton, Ontario, showed that apixaban resulted in a “statistically significant” risk reduction of stroke and systemic embolism, and with only a modest increase in bleeding that was not statistically significant, 1.4 percent versus 1.2 percent in the aspirin arm.

The randomized, double-blind trial enrolled 5,600 patients with AF who were at risk for stroke and unable to be treated with warfarin (Coumadin, Bristol-Myers Squibb). Event rates for stroke or systemic embolic events were significantly lower in the study arm administered apixaban compared to those administered aspirin, 1.6 percent versus 3.6 percent, respectively.

Additionally, rates of stroke, embolic event, MI or vascular death for those administered apixaban were 4.1 percent versus the 6.2 percent reported in patients administered aspirin.

The rates for vascular death, cardiovascular hospitalizations and total death for patients administered apixaban were 2.5 percent, 11.8 percent and 3.4 percent, respectively. These same rates for those patients receiving aspirin therapy were 2.9 percent, 14.9 percent and 4.4 percent, respectively.

Rates of minor bleeding and clinical relevant nonmajor bleeding events were 5.2 percent and 3 percent for the apixaban group compared to 4.1 and 2.6 in the aspirin arm.

"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 AF who are unsuitable for warfarin. These findings will reduce the burden of stroke in society," Connolly said.

The investigators of the AVERROES trial have been notified of the recommendations and patients enrolled in the trial will be offered a long-term, open-label extension of the trial where they could continue to recieve apixaban.