In vivo antithrombotic activity of E149A-APC. Antithrombotic effects of wt-mAPC, E149A-mAPC, and 5A-mAPC in a murine model of carotid artery thrombosis induced by FeCl₃ injury were based on the time to first occlusion. (A) Doppler tracing of carotid artery blood flow after FeCl₃ injury. PBS buffer control or wt-mAPC (1.8 mg/kg) in the presence and absence of a blocking rat monoclonal anti-mAPC antibody (TVM1) was administered in the jugular vein just before the thrombotic insult. Carotid artery blood flow was monitored for 30 minutes after application of FeCl₃. Occlusion was defined as a flow less than 0.2 mL/min. (B) Time to first occlusion in mice treated with increasing doses of wt-mAPC or E149A-mAPC (0.6 mg/kg, 1.2 mg/kg, or 1.8 mg/kg) shown as a box-and-whiskers graph with median, 25th percentile, 75th percentile, and range. Points on discontinuous part of the y-axis above 1500 seconds indicate no occlusion within the 30 minutes experimental period. Statistical analysis was performed using analysis of variance with Bonferroni correction: * P < .05 APC versus PBS; # P < .05 E149A-APC versus wt-APC. (C) Occurrence of first occlusion versus time in mice treated with PBS (×), wt-mAPC (□) or E149A-mAPC (◇; both 1.8 mg/kg), or 5A-mAPC (○; 8.0 mg/kg) shown as a modified Kaplan-Meier plot. Statistical analysis was performed using the log-rank test: * P < .05 APC versus PBS; # P < .05 E149A-APC versus wt-APC. (B,C) Animals per group: PBS, n = 18; wt-mAPC, n = 6-7; E149A-mAPC, n = 4-6; and 5A-mAPC, n = 5.