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

AbstractPrior knowledge of allele frequencies of cytochrome P450 polymorphisms in a population is crucial for the revision and optimization of existing medication choices and doses. In the current study, the frequency of theCYP2C9*2,CYP2C9*3,CYP2C19*2,CYP2C19*3,CYP2C19*6,CYP2C19*17, andCYP3A4(rs4646437) alleles in a Thai population across different regions of Thailand was examined. Tests for polymorphisms ofCYP2C9andCYP3A4were performed using TaqMan SNP genotyping assay andCYP2C19was performed using two different methods; TaqMan SNP genotyping assay and Luminex x Tag V3. The blood samples were collected from 1205 unrelated healthy individuals across different regions within Thailand. Polymorphisms ofCYP2C9andCYP2C19were transformed into phenotypes, which included normal metabolizer (NM), intermediate metabolizer (IM), poor metabolizer (PM), and rapid metabolizers (RM). TheCYP2C9allele frequencies among the Thai population were 0.08% and 5.27% for theCYP2C9*2andCYP2C9*3alleles, respectively. TheCYP2C19allele frequencies among the Thai population were 25.60%, 2.50%, 0.10%, and 1.80% for theCYP2C19*2,CYP2C19*3,CYP2C19*6, andCYP2C19*17alleles, respectively. The allele frequency of theCYP3A4(rs4646437) variant allele was 28.50% in the Thai population. The frequency of theCYP2C9*3allele was significantly lower among the Northern Thai population (P < 0.001). The frequency of theCYP2C19*17allele was significantly higher in the Southern Thai population (P < 0.001). Our results may provide an understanding of the ethnic differences in drug responses and support for the utilization of pharmacogenomics testing in clinical practice.