Enzymatic Activities of CYP3A4 Allelic Variants on Quinine 3-Hydroxylation In Vitro

Abstract

Cytochrome P450 3A4 (CYP3A4) enzyme activity is known to show considerable ethnic heterogeneity and inter-individual differences, affecting the outcome of drug treatment. CYP3A4 genetic polymorphisms are believed to be one of the important causes, leading to inter-individual variability in drug metabolism. Quinine is an antipyretic drug with antimalarial properties that is metabolized primarily by CYP3A4. Quinine 3-hydroxylation has been proven as a biomarker reaction for evaluating CYP3A4 ability. Quinine has frequent adverse effects and there are distinct inter-individual differences in quinine sensitivity. The open reading frame for 30 CYP3A4 allelic variants were constructed from wild-type CYP3A4*1A by an overlap extension polymerase chain reaction. Recombinant CYP3A4 variants were expressed using baculovirus-insect cell expression system, and their catalytic activities towards quinine hydroxylation were determined and evaluated. Of the 30 CYP3A4 allelic variants, 23 variants exhibited significantly reduced intrinsic clearance towards quinine, 2 variants showed increased intrinsic clearance for quinine, 2 variants possessed no significant differences towards quinine, compared with CYP3A4*1A, and 3 variants had no detected expression and enzyme activity. Our assessment on the enzymatic activities of CYP3A4 variants towards quinine may contribute to laying an experimental foundation for further clinical studies so as to accelerate the process of determining the associations between genetic variations and clinical phenotypes.

Allele frequencies of single nucleotide polymorphisms of clinically important drug-metabolizing enzymes CYP2C9, CYP2C19, and CYP3A4 in a Thai population

“…CYP3A4 is responsible for the metabolism of ∼50% of drugs used therapeutically such as clarithromycin, erythromycin, diltiazem, itraconazole, ketoconazole, ritonavir. There is considerable interindividual variability in CYP3A4 activity 10 . CYP3A4 rs4646437 polymorphism was related to the risk of hypertension in the Chinese population 11 .…”

Functional Characterization of 40 CYP3A4 Variants by Assessing Midazolam 1′-Hydroxylation and Testosterone 6β-Hydroxylation

“…Several CYP3A4 genetic variations may contribute to inter-individual differences in drug efficacy and adverse effect rates (Lamba et al, 2002a). Several studies have identified CYP3A4 variants, including rare and region-specific variants, and characterized the associated in vitro enzyme kinetics, including previous studies of CYP3A4 variants among the Han Chinese population using numerous substrates (Supplementary Table 3) (Fang et al, 2017;Xu et al, 2018;Lin et al, 2019a;Lin et al, 2019b;Yang et al, 2019;Zhou et al, 2019a;Chen et al, 2020). However, the underlying causes for functional differences produced by the amino acid alterations are not fully understood and require further research.…”

Physiologically‐Based Pharmacokinetic Modeling for Optimal Dosage Prediction of Quinine Coadministered With Ritonavir‐Boosted Lopinavir

“…The age range of patients used in renal and hepatic insufficiency conditions were 30–60 years. CYP3A4 variants resulted in the changes in intrinsic metabolism of quinine to 0.226‐fold (CYP3A4*3: M44T5), 0.058‐fold (CYP3A4*13: P416L), 0.176‐fold (CYP3A4*18: L293P), and 0.43‐fold (CYP3A4*19: P467S) …”

“…Cytochrome P450 3A4/5 (CYP3A4/5) enzyme has been recognized as a significant human drug‐metabolizing enzyme with high interindividual variations across different ethnicities . An in vitro study demonstrated a reduction of quinine intrinsic clearance in the 23 CYP3A4 variants compared to the wild‐type CYP3A4*1 . Clinical relevance of this association remains to be clarified.…”