Apixaban 'better than aspirin' in atrial fibrillation

Researchers have stopped a Phase III trial of a new anticoagulant in patients with atrial fibrillation after a predefined interim analysis revealed overwhelming evidence of efficacy.

During atrial fibrillation, blood tends to pool in the atria – increasing the risk of thrombosis and stroke
During atrial fibrillation, blood tends to pool in the atria – increasing the risk of thrombosis and stroke

Compared with aspirin, apixaban more than halved the risk of stroke in patients with atrial fibrillation enrolled in the AVERROES trial, researchers reported at the European Society of Cardiology congress in Stockholm on 31 August. Like rivaroxaban, apixaban is a direct inhibitor of Factor Xa.

"The results of AVERROES are truly impressive," said lead investigator Stuart Connolly, a professor of medicine at McMaster University in Canada. "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."

The randomised, double-blind trial recruited 5,600 patients who were unsuitable for treatment with vitamin K antagonists such as warfarin. Participants received apixaban at a dose of 5mg twice daily or aspirin at a dose of 81–324mg once daily.

A prespecified analysis of interim data showed that the relative risk of stroke or systemic embolism (the combined primary end point) was 54% lower in the apixaban-treated patients than in the aspirin-treated patients (p<0.001). The relative risk reduction for stroke alone was 52% (p<0.001).

Importantly, rates of major bleeding events were comparable in the two groups.

Apixaban has already shown promising results in patients with deep vein thrombosis, and for thromboprophylaxis following orthopaedic surgery and acute coronary syndromes.

The ongoing ARISTOTLE trial is comparing apixaban with warfarin in patients with atrial fibrillation who are suitable for treatment with the vitamin K antagonist.

Bristol-Myers Squibb and Pfizer are co-developing the drug.

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