Effects of the reversible BTKi fenebrutinib on platelet aggregation in blood after stimulation by FcγRIIA activation, TRAP, AA, and ADP and on bleeding time in vitro. Blood samples were preincubated for 15 minutes with solvent (DMSO, 0.1%) or fenebrutinib before stimulation with AT10 (2 µg/mL; 3 minutes) plus Fab2 (30 µg/mL), anti-CD9 antibody (1 µg/mL), ristocetin (0.5 mg/mL), TRAP (15 µM), AA (0.6 mM), ADP (5 µM), or collagen (coll) (0.25 µg/mL or 2.5 µg/mL). (A) Dose-response curve of fenebrutinib on platelet aggregation after CD32 cross-linking. (B) Effects of fenebrutinib (50 nM) on anti-CD9 antibody-, ristocetin-, TRAP-, AA-, ADP-, and collagen-induced platelet aggregation and spontaneous platelet aggregation (no stimulus). Values are mean ± SD (n = 5). (C) Effects of fenebrutinib on bleeding time in vitro. Blood samples preincubated for 15 minutes with solvent (DMSO, 0.1%) or increasing concentrations of fenebrutinib were transferred to collagen/epinephrine cartridges, and the in vitro closure time was measured with the PFA-200. Values are mean ± SD (n = 6). *P < .05; ***P < .001.