CYP2C19 phenotype in South-East Asian Acute Coronary Syndrome patients and impact on major adverse cardiovascular events.

WHAT IS KNOWN AND OBJECTIVE: Several Caucasian cohort studies have associated at least one loss-of-function CYP2C19 on Clopidogrel (LoF-Clopidogrel) with major adverse cardiovascular events (MACE), and only a couple have used Clinical Pharmacogenetics Implementation Consortium (CPIC® ) phenotype grouping to study the associations. We primarily aimed to study the impact of use of platelet reactivity testing to escalate antiplatelet therapy and secondarily to study the association of CPIC phenotype with MACE outcomes in South-East Asian Acute Coronary Syndrome (ACS) subjects. METHOD: A retrospective genotype study was performed on 238 percutaneous coronary intervention subjects, originally planned for escalation of antiplatelets using platelet reactivity testing. RESULTS AND DISCUSSION: There was no difference in MACE between the switched and unswitched groups; however, 'all bleeds' and 'clinically significant bleeds' (CSB) were statistically higher in the patients who were switched to prasugrel. The subgroup of patients who remained on clopidogrel (n = 199) were analysed using phenotype categories and MACE. Eleven percent (11.4%) of CYP2C19 poor metabolizers (PM) suffered MACE, compared with 1.3% of extensive metabolizers (EM). LoF-Clopidogrel patients are significantly more likely to experience MACE compared with non-LoF subjects (8.0% vs 5.4%, P: .041). WHAT IS NEW AND CONCLUSION: In our multivariate analysis, LoF-Clopidogrel, malay ethnicity, diabetics and use of proton pump inhibitors were independent predictors of MACE. There were numerically more bleeds in LoF subjects who were on prasugrel compared with Clopidogrel (23.5% vs 11%, P = .082). Our data corroborate with current findings on platelet reactivity testing, suggesting that the assay would not be sensitive enough to pick up sufficient 'at-risk' subjects as compared to the use of CYP2C19 genotyping.

Comparison of rivaroxaban concentrations between Asians and Caucasians and their correlation with PT/INR.

The objectives of this study are to compare steady-state trough (Cmin,ss) and peak (Cmax,ss) concentrations of rivaroxaban between Asians and Caucasians and to evaluate the relationship between rivaroxaban concentrations and prothrombin time/international normalized ratio (PT/INR). Recruited patients were advised on the time to take rivaroxaban. Cmin,ss and PT/INR were taken when patients arrived. Cmax,ss and PT/INR were drawn between 2 and 4 h later after the patient took rivaroxaban with food. Thirty patients were included in the analyses: 57% (n = 17) males and 43% (n = 13) females, 77% (n = 23) on 20 mg and 23% (n = 7) on 15 mg. Median PTtrough and PTpeak are moderately correlated with Cmin,ss (r2 = 0.43) and Cmax,ss (r2 = 0.49), respectively. Patients on 15 mg have lower Cmin,ss and Cmax,ss versus Caucasians [12 ng/ml vs. 57 ng/ml (Cmin,ss); 87 ng/ml vs. 229 ng/ml (Cmax,ss), p < 0.01 for both]. Patients on 20 mg also have lower Cmin,ss and Cmax,ss versus Caucasians [14 ng/ml vs. 44 ng/ml (Cmin,ss); 101 ng/ml vs. 249 ng/ml (Cmax,ss), p < 0.01 for both]. Subgroup analysis shows patients with BMI ≥ 30 have lower Cmax,ss than patients with BMI < 30 [80.47 ng/ml vs. 124 (p = 0.014)]. Cmin,ss and Cmax,ss were lower in Singaporeans than Caucasians. This may have an impact on the effectiveness of rivaroxaban in Singaporeans. Patients with higher BMI may not benefit similarly as patients with lower BMI. Lastly, the Dade Innovin reagent's measure of PT/INR is not sensitive towards changes in rivaroxaban concentrations.