LR04 delays whole blood clotting without affecting platelet aggregation. (A-D) Effect of LR04 on whole blood clotting using rotational thromboelastometry. Freshly drawn blood of healthy individuals (n = 11) was incubated for 20 minutes with 25 µg/mL of either LR04 or an isotype (iso) control antibody before initiating rotational thromboelastometry in the nonactivated method mode. (A) Clotting time, (B) clot formation time, (C) time of maximum clot firmness, and (D) maximum clot firmness. Bars represent the mean of each group. **P < .01, ***P < .005, Wilcoxon matched-pairs signed-rank test. (E-G) Effect of LR04 on platelet aggregation. Washed platelets isolated from healthy volunteers (n = 11-15) were preincubated for 20 minutes with LR04 or an IgM control antibody (25 µg/mL) before activation with thrombin (E), collagen (F), or adenosine 5′-diphosphate (ADP) (G). Shown are representative aggregation curves. au, arbitrary units.