AZD1152 (barasertib) is a pro-drug that rapidly undergoes phosphatase-mediated cleavage in serum to release barasertib-hQPA, a selective Aurora B kinase inhibitor that has shown preliminary activity in clinical studies of patients with acute myeloid leukemia (AML). The MTDs （the maximum-tolerated dose ） were 150 mg as a 48-h continuous infusion and 220 mg administered as two 2-h infusions (110 mg/day, days 1, 2, 15 and 16), with neutropenia the dose-limiting toxicity (DLT) of each schedule. Common Terminology Criteria of Adverse Events The pharmacokinetic (PK), metabolic and excretion profiles of barasertib and barasertib-hQPA were characterized in this open-label Phase I study. Pgp and BCRP positive primary samples were less sensitive to barasertib-hQPA induced pHH3 inhibition (p = <0.001) than samples without these transporters. IC50inhibition of pHH3 by barasertib-hQPA was achieved in 94.6% of these samples after 1 hour drug treatment, in contrast to the resistance of the cell lines. Common Terminology Criteria of Adverse Events (CTCAE) grade?≥?3 neutropenia (with or without fever) occurred in 34 % of patients overall. Barasertib-hQPA was extensively distributed to tissues, with a slow rate of total clearance (CL = 31.4 L/h). Overall, 72-82 % of radioactivity was recovered, with approximately double the amount recovered in feces (mean = 51 %) compared with urine (mean = 27 %).