A Pharmacokinetic-Pharmacodynamic Model of Tamoxifen and Endoxifen to Predict Their Distribution and Effects on Inhibition of Tumor Growth
Background: Tamoxifen is widely used in the therapy for breast cancer and has three major metabolites, N-desmethyltamoxifen, 4-hydroxytamoxifen, and endoxifen. Endoxifen has played a major role in the inhibition of tumor growth of breast cancer and the tumor growth is related to endoxifen
concentration.
Objectives: The aim of this study was to develop a pharmacokinetic-pharmacodynamic model to predict the distribution of tamoxifen and endoxifen quantitatively, and to discover the anti-tumor effect patterns of tamoxifen and endoxifen.
Methods: The pharmacokinetic-pharmacodynamic model was established by integrating a four compartments pharmacokinetics model and a pharmacodynamic model, the first one include central compartment and peripheral compartment both of which contain tamoxifen and endoxifen. The parameters of the model were calculated by the values of plasma concentrations and the tumor growth data before and after the administration of tamoxifen.
Results: The transport rate k42 (6.0003) of endoxifen from the peripheral compartment to the central compartment and the metabolism rate k34 (0.0031) from tamoxifen to endoxifen in the peripheral compartment were proven to be significant, which showed that tamoxifen and endoxifen are mainly distributed in the central compartment. The model provided reasonable predictions of tumor growth, which was inhibited after the administration and varies with the concentration of endoxifen.
Conclusion: We established a PK-PD model of tamoxifen and endoxifen to predict the tumor growth. The parameters of the pharmacodynamic model, which characterized the tumor growth, revealed the patterns of tamoxifen's anti-tumor functions. The PK-PD model successfully provided illustration for the pharmacokinetics of tamoxifen and endoxifen, and predicted the inhibition effect of endoxifen on the tumor growth.
Objectives: The aim of this study was to develop a pharmacokinetic-pharmacodynamic model to predict the distribution of tamoxifen and endoxifen quantitatively, and to discover the anti-tumor effect patterns of tamoxifen and endoxifen.
Methods: The pharmacokinetic-pharmacodynamic model was established by integrating a four compartments pharmacokinetics model and a pharmacodynamic model, the first one include central compartment and peripheral compartment both of which contain tamoxifen and endoxifen. The parameters of the model were calculated by the values of plasma concentrations and the tumor growth data before and after the administration of tamoxifen.
Results: The transport rate k42 (6.0003) of endoxifen from the peripheral compartment to the central compartment and the metabolism rate k34 (0.0031) from tamoxifen to endoxifen in the peripheral compartment were proven to be significant, which showed that tamoxifen and endoxifen are mainly distributed in the central compartment. The model provided reasonable predictions of tumor growth, which was inhibited after the administration and varies with the concentration of endoxifen.
Conclusion: We established a PK-PD model of tamoxifen and endoxifen to predict the tumor growth. The parameters of the pharmacodynamic model, which characterized the tumor growth, revealed the patterns of tamoxifen's anti-tumor functions. The PK-PD model successfully provided illustration for the pharmacokinetics of tamoxifen and endoxifen, and predicted the inhibition effect of endoxifen on the tumor growth.
Keywords: PK-PD model; Tamoxifen; endoxifen; plasma concentration; tumor growth; tumor growth model
Document Type: Research Article
Publication date: 01 June 2017
- Drug Metabolism Letters publishes short papers on major advances in all areas of drug metabolism and disposition. The emphasis will be on publishing quality papers very rapidly. Letters will be processed rapidly by taking full advantage of the Internet technology for both the submission and review of manuscripts. The journal covers the following areas:
In vitro systems including CYP-450; enzyme induction and inhibition; drug-drug interactions and enzyme kinetics; pharmacokinetics, toxicokinetics, species scaling and extrapolations; P-glycoprotein and transport carriers; target organ toxicity and interindividual variability; drug metabolism and disposition studies; extrahepatic metabolism; phase I and phase II metabolism; recent developments for the identification of drug metabolites, reactive intermediate and glutathione conjugates. - Editorial Board
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