Background: Guidelines recommend warfarin as the standard of care for patients with atrial fibrillation (AF) at moderate or high risk for stroke. This phase II study assessed the effects of 2 doses of the factor Xa inhibitor apixaban vs. warfarin in Japanese patients with non-valvular AF. The composite primary endpoint was major and clinically relevant non-major (CRNM) bleeding.
Methods and results: Two hundred and twenty-two patients with AF and 1 or more additional risk factors for stroke were randomized (1:1:1) to double-blind apixaban 2.5 or 5mg b.i.d. or open-label warfarin (target international normalized ratio 2.0-3.0; 2.0-2.6 if age ≥ 70 years) for 12 weeks. The primary endpoint occurred in 1 patient (1.4%) in each apixaban group and 4 (5.3%) warfarin patients. There were no strokes, systemic emboli, myocardial infarctions, or deaths in either apixaban group. The warfarin group had 2 ischemic strokes and 1 subarachnoid hemorrhage, but there were no deaths. Major and CRNM bleeds each occurred with higher frequency in the warfarin group vs. either apixaban group. Most adverse events were mild or moderate. No patients had hepatic aminotransferase elevations greater than 3 times the upper limit of normal.
Conclusions: In Japanese patients with AF, apixaban 2.5 and 5mg b.i.d. were well tolerated over 12 weeks. A global phase III trial, which includes Japanese patients, is ongoing (ClinicalTrials.gov Identifier NCT00787150).