PRN473 inhibits IVC thrombosis in mice. (A) WT mice were gavaged daily with vehicle or PRN473 (80 mg/kg) for 4 days, then had platelet activation measured in citrated whole blood by flow cytometry, as indicated by activated integrin αIIbβ3 (JON/A) and P-selectin surface expression, after stimulation with snake venom toxin rhodocytin (100 and 300 nM), CRP (3 and 10 μg/mL), or thrombin (0.03 and 0.1 U/mL). GPRP was added to thrombin stimulation to prevent fibrin clot formation. Mean ± SEM (n = 3). Statistical analysis by 2-way ANOVA with Sídák correction for multiple comparisons. (B) IVC stenosis model of DVT was performed on WT mice gavaged with vehicle or PRN473 (80 mg/kg) for 4 days. Mice were euthanized 6 hours after IVC ligation and had spleens harvested for Btk occupancy analysis (i) and citrated plasma taken for drug concentration measurements (ii), and assessment for thrombus prevalence (iii), length (iv), and weight (v). Median: n = 16-18 mice per condition for splenic Btk occupancy and thrombus analysis; n = 17-21 mice per condition for plasma drug concentration measurements. Statistical analysis by Mann-Whitney test. ∗P < .01; ∗∗∗P = .0002; ∗∗∗∗P < .0001. GPRP, Gly-Pro-Arg-Pro; Veh, vehicle; WT, wild type.