Pharmacokinetics of Gefitinb: Roles of Drug Metabolizing Enzymes and Transporters

Gefitinib (Iressa, AstraZeneca) has been widely used for the treatment of locally advanced or metastatic non-small cell lung cancer. A number of studies have been reported on its pharmacokinetics profiles, especially on the metabolism. In this review, we have comprehensively summarized the pharmacokinetic characteristics of gefitinib: absorption, distribution, metabolism and excretion (ADME). Overall, gefitinib reached the maximum plasma level relatively fast and distributed extensively. It underwent extensive biotransformation and predominantly excreted in feces, with less than 7% in the urine. CYP450 enzymes played critical roles in the process of gefitinib metabolism. The major enzyme involved in the metabolism was CYP3A4, with other CYP450 enzymes playing a secondary role. A high clearance of gefitinib might result in drug resistance by lowering drug concentration. The enhanced efflux and decreased uptake by transporters were important resistance mechanisms. The transporters involved in pharmacokinetics of gefitinib consist of the ATP-binding cassette and the solute carrier superfamily. Understanding the pharmacokinetics property of gefitinib may provide valuable and new information for dealing with drug resistance and making personalized therapy regarding their interindividual variability. Keywords: Enzymes, gefitinib, metabolism, pharmacokinetics, transporters.