(A) Systemic concentration of SCE5-TAP over time with i.v. or s.c. delivery. Concentrations were characterized based on circulating anti-FXa activity and compared with a standard curve. (B–H) SCE5-TAP targets and reduces venous thrombosis after laser injury of cremaster venules. (B) Platelet-specific Dylight 649–labeled anti-CD42b was infused with AF488-labeled SCE5-TAP (top row), AF488-labeled MUT-TAP (middle row), or AF488 control (bottom row) prior to laser injury of cremaster venules. Representative images illustrate that SCE5-TAP targets platelets within the venous thrombus. Colocalization of MUT-TAP or AF488 control was not observed. (C–D) SCE5-TAP efficiently reduces venous thrombus at a dose administration of 0.1 μg/g s.c. (solid green, thrombus inhibition characterized 4 hours after s.c. administration). Results are compared with equivalent doses of MUT-TAP (s.c.) or LMWH (enoxaparin, 4 μg/g s.c.), 4 hours after s.c. administration. Results are plotted as median integrated platelet fluorescence (C) or platelet accumulation quantified as AUC (D); n = 20–34 vessels in 4–5 mice/group. (E) Circulating anti-FXa activity was measured for each agent (data collected 4 hours after s.c. administration). Data represent mean ± SD, n = 4 per group. (F and G) SCE5-TAP reduces venous thrombus formation 24 hours after s.c. administration. The dose of SCE5-TAP was increased to 0.5 μg/g s.c. (dark green), and laser injury of cremaster venules was performed 24 hours later. Results are compared with equivalent doses of MUT-TAP (blue, 0.5 μg/g s.c.), equimolar SCE5 (yellow, 0.3 μg/g s.c.), or LMWH (black, 4 μg/g s.c.). Results are plotted as median integrated platelet fluorescence (F) or platelet accumulation quantified as AUC (G); n = 20–34 vessels in 4–5 mice/group. (H) Circulating anti-FXa activity was measured for each s.c. dose 4 hours after administration. Data represent mean ± SD, n = 4 per group. All P values were determined by ANOVA and Bonferroni’s multiple comparison test, **P ≤ 0.01, and ***P ≤ 0.001.