Evaluation of antidote effect of AT-N135Q-Pro394 in UFH-overdosed plasma on the basis of anti–thrombin activity measurement. Antidote efficacy of AT-N135Q-Pro394 was estimated in UFH (1.8 U/mL) containing plasma for its ability to decrease heparin-induced anti–thrombin activity. AT variant 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 dose of UFH.