WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

Compared with standard dual antiplatelet therapy, adjunctive cilostazol to dual antiplatelet therapy ('triple antiplatelet therapy') has a potential to reduce ischemic event occurrence after percutaneous coronary intervention. The pharmacokinetic and pharmacodynamic effects of clopidogrel have been significantly influenced by the enzyme activity of the ABCB1 C3435T and the CYP2C19 system. • For the pharmacokinetics of cilostazol, genetic polymorphisms of the CYP3A5 and CYP2C19 have been associated with the substantial interindividual variability in healthy volunteers.

WHAT THIS STUDY ADDS

Loss-of-function polymorphism of the CYP2C19 gene, but not the ABCB1 C3435T and CYP3A5*3 genes, affects the antiplatelet effect of triple antiplatelet therapy. Most of extensive and intermediate East Asian metabolizers (0 or 1 CYP2C19 loss-of-function allele) show adequate platelet inhibition when treated with triple antiplatelet therapy after percutaneous coronary intervention. However, carriage of 2 CYP2C19 loss-of-function alleles is still associated with the risk of high platelet reactivity (defined by by 5 µM ADP-induced maximal platelet aggregation >46%), which clinical impact needs to be validated in future clinical trials. AIMS Although adjunctive cilostazol to dual antiplatelet therapy can reduce the risks of clinical events after percutaneous coronary intervention (PCI), whether genetic polymorphism can influence the pharmacodynamics of this regimen has not been evaluated.

METHODS

One hundred and twenty-seven patients treated with PCI and taking triple antiplatelet therapy (≥1 month) were enrolled. Platelet reactivity was assessed by conventional aggregometry and the VerifyNow P2Y12 assay. High on-treatment platelet reactivity (HPR) was defined as 5 µm ADP-induced maximal platelet reactivity (Agg(max) ) >46%. CYP3A53, CYP2C192/*3 and ABCB1 3435C > T were genotyped.

RESULTS

CYP3A5*3 and ABCB1 3435C > T variants did not affect the antiplatelet effect of triple antiplatelet therapy. For non-carriers, one and two carriers of the CYP2C19 loss-of-function (LOF) allele, Agg(max) consecutively increased after the addition of 5 µm[mean (95% confidence intervals): 24.6% (20.8 to 28.5%) vs. 28.7% (25.4 to 32.0%) vs. 32.3% (25.8 to 38.7%), P = 0.062, respectively] and 20 µm ADP [34.2% (29.3 to 39.0%) vs. 41.7% (37.8 to 45.6%) vs. 44.9% (37.9 to 51.9%), P = 0.007, respectively]. Likewise, late platelet reactivity and P2Y12 reaction units proportionally changed according to the number of CYP2C19 LOF alleles. HPRs were observed in 9.2% of subjects: 6.3%, 7.4% and 20.0% with 0, 1 and 2 carriers of CYP2C19 LOF allele(s) (P = 0.099). In multivariate analysis, carriage of two CYP2C19 LOF alleles was a significant predictor for the prevalence of HPR (odds ratio 5.78, 95% CI 1.21, 27.78, P = 0.028).

CONCLUSION

Among PCI-treated patients, the effect of triple antiplatelet therapy is influenced by the CYP2C19 LOF allele. Its clinical benefit needs to be validated according to the CYP2C19 metabolic phenotype in future clinical trials. [Adjunctive Cilostazol Versus High Maintenance dose ClopidogrEL in Acute Myocardial Infarction Patients According to CYP2C19 Polymorphism (ACCEL-AMI-2C19), NCT00915733 and Adjunctive Cilostazol Versus High Maintenance-dose Clopidogrel According to Cytochrome 2C19 Polymorphism (ACCEL-2C19), NCT01012193].