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Medline ® Abstract for Reference 48

of 'Clinical use of tyrosine kinase inhibitors for chronic myeloid leukemia'

Pharmacokinetics and pharmacodynamics of imatinib in a phase I trial with chronic myeloid leukemia patients.
Peng B, Hayes M, Resta D, Racine-Poon A, Druker BJ, Talpaz M, Sawyers CL, Rosamilia M, Ford J, Lloyd P, Capdeville R
J Clin Oncol. 2004;22(5):935.
PURPOSE: To evaluate the basic pharmacokinetic (PK) characteristics of imatinib mesylate and assess the relationship between the PK and pharmacodynamic (PD) properties of the drug.
PATIENTS AND METHODS: The PK and PD properties of imatinib were investigated during a phase I trial that included 64 adult patients with Philadelphia chromosome-positive leukemias. Patients received imatinib orally once or twice daily. PK parameters of imatinib, derived from the plasma concentration-time curves, were determined. PD response, defined as the WBC after 1 month of treatment with imatinib, was used to develop an efficacy model. A maximum inhibition-effect model was used to describe the relationship between reduction in WBC and drug exposure parameters.
RESULTS: Imatinib exposure was dose proportional after oral administration for the dose range of 25 to 1,000 mg. There was a 1.5- to three-fold drug accumulation after repeated once-daily dosing. Mean plasma trough concentration was 0.57 microg/mL (approximately 1 micromol/L) 24 hours after administration of 350 mg of imatinib at steady-state, which exceeds the 50% inhibitory concentration required to inhibit proliferation of Bcr-Abl-positive leukemic cells. Analysis of PK/PD relationships indicates that the initial hematologic response depends on the administered dose for patients with chronic myeloid leukemia.
CONCLUSION: Drug exposure (area under the concentration-time curve) is dose proportional for the dose range of 25 to 1,000 mg, and there is a 1.5- to three-fold drug accumulation at steady-state after once-daily dosing. Analysis of the relationship between PD (WBC reduction) and PK parameters at steady-state indicates that a dose of 400 mg or greater is required for maximal PD effect.
Clinical Pharmacology, Novartis, One Health Plaza, Building 419, Room 2368, East Hanover, NJ 07936-1080, USA. bin.peng@pharma.novartis.com