ACP-5862 is a major active, circulating, pyrrolidine ring-opened metabolite of Acalabrutinib with an IC 50 of 5.0 nM for Bruton tyrosine kinase (BTK). ACP‐5862 is a weak time‐dependent inactivator of CYP3A4 and CYP2C8. Acalabrutinib is an orally active, irreversible, and highly selective BTK inhibitor , with an IC 50 of 3 nM and EC 50 of 8 nM. In Vivo Following a single oral dose of 100 mg Acalabrutinib, the half‐life of ACP‐5862 is 6.9 hours and the mean exposure is approximately twofold to threefold higher than that of Acalabrutinib. ACP-5862 (M27) is the major single metabolite in the systemic circulation and accountes for 57.4% and 42.1% of the AUC 0-t total radioactivity in male and female rat plasma, respectively. ACP-5862, the major human metabolite, is a relatively minor component in the systemic circulation and accountes for 6.1% and 8.1% of the AUC 0-t total radioactivity in male and female dog plasma, respectively . ACP-5862 (1 or 10 μM) has reversible protein binding of 98.6%, 99.8%, 94.3%, 98.6% in mouse, rat, dog, and human plasma . MCE has not independently confirmed the accuracy of these methods. They are for reference only. Form:Solid