No association of ABCB1 C3435T genotype with clopidogrel response or risk of stent thrombosis in patients undergoing coronary stenting.

BACKGROUND: The prodrug clopidogrel requires intestinal absorption by the efflux pump P-glycoprotein MDR1 (multidrug resistant-1), encoded by the ABCB1 gene. Prior studies suggested that a common and functional genetic variant (C3435T, rs1045642) within ABCB1 influences clopidogrel treatment efficacy; however, existing data are highly inconsistent, because other studies failed to replicate this postulated association. Thus, the aim of this study was to assess the association of ABCB1 C3435T genotypes with the antiplatelet efficacy of clopidogrel and the risk of stent thrombosis (ST) in large cohorts of clopidogrel-treated patients undergoing percutaneous coronary intervention. METHODS AND RESULTS: DNA samples from 1524 clopidogrel-treated patients undergoing percutaneous coronary intervention were genotyped for ABCB1 C3435T, and ADP-induced platelet aggregation was assessed in whole blood on a Multiplate analyzer. The clinical impact of the genetic variant was investigated by comparison of genotype frequencies in a registry of 66 cases with definite drug-eluting stent ST versus an ST-free control cohort (n=1408). Platelet aggregation values were similar across ABCB1 C3435T genotypes (P=0.73). No significant influence of ABCB1 C3435T genotypes on the occurrence of ST was found when ST case subjects were compared with control subjects (P=0.89). CONCLUSIONS: ABCB1 C3435T genotypes did not influence the antiplatelet response to clopidogrel or the risk of ST in clopidogrel-treated patients undergoing percutaneous coronary intervention. Routine genotyping of ABCB1 C3435T polymorphisms should not be recommended for risk stratification in clopidogrel-treated patients undergoing percutaneous coronary intervention who are similar to those evaluated in the present study.

Cytochrome 2C19*17 allelic variant, platelet aggregation, bleeding events, and stent thrombosis in clopidogrel-treated patients with coronary stent placement.

BACKGROUND: The cytochrome P450 (CYP) 2C19 isoenzyme plays an important role in clopidogrel metabolization. A recently explored CYP2C19*17 allelic variant has been linked to increased transcriptional activity, resulting in extensive metabolization of CYP2C19 substrates, which may lead to an enhanced platelet response to clopidogrel treatment. The aim of this study was to assess the impact of CYP2C19*17 on ADP-induced platelet aggregation, the risk of bleeding, and stent thrombosis in clopidogrel-treated patients undergoing percutaneous coronary intervention. METHODS AND RESULTS: The study population included 1524 patients undergoing percutaneous coronary intervention after pretreatment with 600 mg clopidogrel. Genotypes were determined with a TaqMan assay. ADP-induced platelet aggregation was assessed on a Multiplate analyzer. The primary clinical safety end point was the 30-day incidence of bleeding defined according to Thrombolysis in Myocardial Infarction criteria, and the primary clinical efficacy end point was the 30-day incidence of stent thrombosis. For both heterozygous (*wt/*17; n=546) and homozygous (*17/*17; n=76) allele carriers, significantly lower ADP-induced platelet aggregation values were found compared with wild-type homozygotes (*wt/*wt; n=902; P=0.039 and P=0.008, respectively). CYP2C19*17 allele carriage was significantly associated with an increased risk of bleeding; the highest risk was observed for CYP2C19*17 homozygous patients (P=0.01, chi(2) test for trend). Multivariate analysis confirmed the independent association of CYP2C19*17 allele carriage with platelet aggregation values (P<0.001) and the occurrence of bleeding (P=0.006). No significant influence of CYP2C19*17 on the occurrence of stent thrombosis was found (P=0.79). CONCLUSIONS: CYP2C19*17 carrier status is significantly associated with enhanced response to clopidogrel and an increased risk of bleeding.