Ibrutinib induces shedding of platelet surface GPIbα and integrin α_IIbβ₃with production of soluble GPIbα and soluble integrin α_IIbfrom mouse platelets in vivo. (A-B) Whole blood was collected from C57BL/6 mice treated with 10 mg/kg ibrutinib or 10 mg/kg zanubrutinib or vehicle control after 2 hours of ingestion by oral gavage. Washed murine platelets (100 × 10⁹/L) were then labeled with anti-mouse CD42b (GPIbα) or anti-mouse CD41a (integrin α_IIbβ₃) PE-conjugated antibodies. Flow cytometric analysis was used to determine the respective platelet glycoprotein expression. Statistical analysis was performed with the Student t test. Results are represented as mean fluorescence intensity (MFI) ± SEM from 3 independent experiments. ****P ≤ .0001. (C-D) Plasma obtained from C57BL/6 mice treated with 10 mg/kg ibrutinib, 10 mg/kg zanubrutinib, or vehicle control was collected after 2 hours of ingestion by oral gavage. Levels of plasma soluble GPIbα (A) and soluble integrin α_IIb (B) were determined for vehicle control vs Btk inhibitor-treated C57BL/6 mice using ELISA-based assays. Results represent 3 independent experiments and are plotted as the mean ± SEM, by unpaired Student t test. **P ≤ .01, ***P ≤ .005.