Indirect systemic and direct oral factor Xa and direct oral factor IIa 
inhibitors with improved pharmacologic profiles compared with heparins and 
vitamin K antagonists are currently in clinical development. This overview 
focuses on the indirect antithrombin dependent pentasaccharide derivatives of 
idraparinux and on the most advanced oral direct inhibitors to factor Xa 
(rivaroxaban and apixaban) and IIa (dabigatran). Specifically, the results of 
dose-finding studies for the prevention of venous thromboembolism after elective 
orthopedic surgery, the results of dose-finding studies for treatment of acute 
venous thromboembolism including prolonged prophylaxis of recurrent events, and 
the designs of ongoing clinical trials are reviewed.