['Tissue factor pathway inhibitor (TFPI) is the major inhibitor of tissue factor-initiated coagulation, making it an interesting and novel therapeutic target in hemophilia treatment. The aptamer BAX499 (formerly ARC19499) is designed to improve hemostasis by specifically inhibiting TFPI.', 'The aim of the study was to examine the concentration-dependent augmentation of clotting by BAX499.', 'Whole blood clot formation was quantified by rotational thromboelastometry and thromboelastography, and thrombin generation in platelet-poor plasma was assessed with the calibrated automated thrombogram, in samples from patients with congenital hemophilia A (N=55) and B (N=11), patients with acquired hemophilia A (N=1), and healthy controls (N=37).', 'BAX499 significantly improved clotting of samples from hemophilic patients in a concentration-dependent manner, resulting in clotting profiles in samples from patients with severe hemophilia that were similar to those of healthy controls.'] Does inhibition of tissue factor pathway inhibitor by the aptamer BAX499 improve clotting of hemophilic blood and plasma?