Oral IIa and Xa inhibitors for prevention of stroke in atrial fibrillation: clinical studies and regulatory considerations.

Atrial fibrillation (AF), the most common, clinically significant, cardiac arrhythmia affects 1% of the general population and has important hemodynamic and thromboembolic complications that contribute to elevated morbidity and mortality. AF increases the overall risk of stroke five-fold, accounting for approximately 15% of all strokes and is associated with particularly severe stroke. For the last 50 years, long-term anticoagulation with vitamin K antagonists has been the most effective therapy for preventing stroke and systemic embolism in patients with AF and other risk factors, but their use has a lot of limitations and drawbacks (frequent monitoring and dose adjustment, food and drug interactions, delayed onset of action etc). Nowadays, new oral anticoagulants have emerged that seem to overcome those limitations. Direct thrombin inhibitor dabigatran and factor Xa inhibitors rivaroxaban and apixaban have proven, in large, multicenter, randomized, phase III, clinical studies, to be at least as efficient as warfarin in stroke prevention in patients with AF. RELY and ROCKET AF trials have contributed to market approval of dabigatran and rivaroxaban, respectively and made them available to clinical practice. Another factor Xa inhibitor, edoxaban, is under evaluation in an ongoing phase III clinical trial and others such as AZD0837, betrixaban and darexaban are still in safety and tolerability phase II studies. The oral anticoagulation landscape is changing rapidly and these new agents seem to be very promising. However future post-marketing studies and registries will help clarify their efficacy and safety.