Functional Analysis of Wild-Type and 27 CYP3A4 Variants on Dronedarone Metabolism In vitro

Background: Cytochrome P450 (P450) is the largest family of enzymatic proteins in the human liver, and its features have been studied in physiology, medicine, biotechnology, and phytoremediation. Objective: The aim of this study was to assess the catalytic activities of 28 human CYP3A4 alleles by using dronedarone as a probe drug in vitro, including 7 novel alleles recently found in the Han Chinese population. Methods: We expressed 28 CYP3A4 alleles in insect microsomes and incubated them with 1-100 μM of dronedarone at 37 °C for 40 minutes to obtain the metabolites of N-debutyl-dronedarone. Results: Compared with the wild type of CYP3A4, the 27 defective alleles can be classified into four categories. Three alleles had no detectable enzyme activity leading to a lack of kinetic parameters of N-debutyl-dronedarone; the other three alleles slightly despaired when it comes to intrinsic clearance values compared with the features of the wild type. Sixteen alleles exhibited 35.91%~79.70% relative values (in comparison to the wild-type) and could be defined as the “moderate decrease group”. The rest of the alleles showed a considerable decrease in intrinsic clearance values, ranging from 11.88%~23.34%. Therefore they were classified as a “significantly decreased group”. More specifically, 18 CYP3A4 alleles exhibited a substrate inhibition trend toward dronedarone when the concentration rises to 20 μM. Conclusion: The outcomes of this novel study on the metabolism of dronedarone by CYP3A4 alleles can be used as experimental data support for the individualized use of this modern drug.