New anticoagulants for atrial fibrillation

Atrial fibrillation is already the most common clinically significant cardiac arrhythmia and a common cause of stroke. Vitamin K antagonists are very effective for the prevention of cardioembolic stroke but have numerous limitations that limit their uptake in eligible patients with AF and reduce their effectiveness in treated patients. Multiple new anticoagulants are under development as potential replacements for vitamin K antagonists. Most are small synthetic molecules that target factor IIa (e.g., dabigatran etexilate, AZD-0837) or factor Xa (e.g., rivaroxaban, apixaban, betrixaban, DU176b, idrabiotaparinux). These drugs have minimal protein binding and predictable pharmacokinetics that allow fixed dosing without laboratory monitoring and are being compared with vitamin K antagonists or aspirin in phase III clinical trials. A new vitamin K antagonist (ATI-5923) with improved pharmacological properties compared with warfarin is also being evaluated in a phase III trial. None of the new agents have as yet been approved for clinical use.