The influence of the CYP2C19*10 allele on clopidogrel activation and CYP2C19*2 genotyping

BACKGROUND/OBJECTIVES: The polymorphic hepatic enzyme CYP2C19 catalyzes the metabolism of clinically important drugs such as clopidogrel, proton-pump inhibitors, and others and clinical pharmacogenetic testing for clopidogrel is increasingly common. The CYP2C19*10 single-nucleotide polymorphism (SNP) is located 1 bp upstream the CYP2C19*2 SNP. Despite the low frequency of the CYP2C19*10 allele, its impact on metabolism of CYP2C19 substrates and CYP2C19*2 genotyping makes it an important SNP to consider for pharmacogenetic testing of CYP2C19. However, the effect of the CYP2C19*10 allele on clopidogrel metabolism has not been explored to date. METHODS: We measured the enzymatic activity of the CYP2C19.10 protein against clopidogrel. DNA samples from two clinical studies were genotyped for CYP2C19*2 and *10 by pyrosequencing genotyping method. RESULTS: The catalytic activity of CYP2C19.10 in the biotransformation of clopidogrel and 2-oxo-clopidogrel was significantly decreased relative to the wild-type CYP2C19.1B. We also reported that the CYP2C19*10 SNP interferes with the CYP2C19*2 TaqMan genotyping assay, resulting in miscalling of CYP2C19*10/*2 as CYP2C19*2/*2. CONCLUSIONS: Our data provide evidence that CYP2C19.10 variant partially metabolizes clopidogrel and 2-oxo-clopidogrel, and the presence of CYP2C19*10 allele affects the CY2C19*2 TaqMan genotyping assay and results in misclassification of CYP2C19*10/*2 as CYP2C19*2/*2.