Inhibition of platelet thrombus formation on atherosclerotic plaque, but not collagen, under arterial flow in patients treated with ibrutinib. Representative micrographs show platelet coverage of plaque homogenate (A), plaque tissue sections (B), and collagen (C) at 0 and 6 minutes after the start of flow (shear rate 600/s) with blood from ibrutinib-treated patients and control patients (left panels). Effects of ibrutinib treatment on the kinetics of plaque- and collagen-induced platelet deposition (right panels). Data are mean + SD (n = 5). (D) Effect of oral ibrutinib treatment on bleeding time in vitro (PFA-100). Blood samples from 5 patients treated with ibrutinib and 5 control patients were transferred to epinephrine/collagen (Epi/Coll) or ADP/collagen (ADP/Coll) cartridges, and the in vitro CT was measured with a PFA-100 platelet function analyzer. Data are mean + SD (n = 5). *P < .05, **P < .01, ***P < .001.