Evaluation of antidote effect of AT-N135Q-Pro394 in heparin derivative–overdosed plasma on the basis of anti-FXa activity measurement. Antidote potential of AT-N135Q-Pro393 was estimated according to its ability to decrease heparin-induced anti-FXa activity in plasma containing fondaparinux 3 mg/L (A), LMWH 3 U/mL (B), or UFH 1.8 U/mL (C). These heparin derivative concentrations correspond to approximately 3-fold the maximal curative dose. AT-N135Q-Pro394 was added to tested plasma at 0, 75, 150, 300, and 600 mg/L, which corresponded to ratios variant to pAT of 0, 0.5, 1, 2, and 4, respectively. Dashed lines indicate maximal and minimal curative concentration for each heparin derivative.