Pharmacokinetics and pharmacodynamics of dasatinib in the chronic phase of newly diagnosed chronic myeloid leukemia.

PURPOSE: Dasatinib is a novel, oral, multi-targeted kinase inhibitor of breakpoint cluster region-abelson (BCR-ABL) and Src family kinases. The study investigated pharmacokinetic (PK) and pharmacodynamic (PD) analyses of dasatinib in 51 newly diagnosed, chronic phase, chronic myeloid leukemia patients.

METHODS: The dasatinib concentration required to inhibit 50 % of the CrkL (CT10 regulator of kinase like) phosphorylation in bone marrow CD34+ cells (half maximal (50 %) inhibitory concentration (IC50)CD34+cells) was calculated from each patient's dose-response curve using flow cytometry. PK parameters were obtained from the population pharmacokinetic analysis of dasatinib concentrations in plasma on day 28 after administration.

RESULTS: Early molecular responses were not significantly associated with PK or PD (IC50 CD34+cells) parameters. However, the PK/PD parameter-time above IC50 CD34+cells-significantly correlated with BCR-ABL transcript level at 3 months (correlation coefficient (CC) = -0.292, P = 0.0375) and the reduction of BCR-ABL level at 1 or 3 months (CC = -0.404, P = 0.00328 and CC = -0.356, P = 0.0104, respectively). Patients with more than 12.6 h at time above IC50 CD34+cells achieved a molecular response of 3.0 log reduction at 3 months and those more than 12.8 h achieved a deep molecular response less than 4.0 log reduction at 6 months at a significantly high rate (P = 0.013, odds ratio = 4.8 and P = 0.024, odds ratio = 4.3, respectively).

CONCLUSION: These results suggest that the anti-leukemic activity of dasatinib exhibits in a time-dependent manner and that exposure for more than 12.8 h at time above IC50 CD34+cells could significantly improve prognosis.