Genotyping, Platelet Activation, and Cardiovascular Outcome in Patients after Percutaneous Coronary Intervention: Two Pieces of the Puzzle of Clopidogrel Resistance

Association of CYP2C19 Loss-of-Function Alleles with Major Adverse Cardiovascular Events of Clopidogrel in Stable Coronary Artery Disease Patients Undergoing Percutaneous Coronary Intervention: Meta-analysis

PURPOSE

It was aimed to determine the aggregated risk of MACE (major adverse cardiovascular events) in stable CAD patients carrying CYP2C19 LoF alleles taking clopidogrel.

METHODS

Literature was searched in different databases for relevant studies. Aggregated risk was estimated using a fixed/random effect model where p-value<0.05 was considered statistically significant.

RESULTS

In total, 21 studies with 16,194 stable CAD patients were assessed. It was found that patients treated with clopidogrel carrying either one or two CYP2C19 LoF alleles who underwent PCI were associated with significantly increased risk of MACE compared to non-carriers (OR: 1.71, 95% CI: 1.51-1.94, p<0.00001) that was driven from cardiovascular death (OR: 1.43, 95% CI: 1.02-1.99, p=0.04), myocardial infarction (OR: 1.75, 95% CI: 1.42-2.16, p<0.00001), stroke (OR: 2.30, 95% CI: 1.52-3.47, p<0.0001), and stent thrombosis (OR: 4.08, 95% CI: 2.52-6.61, p<0.00001). It was also found that carriers of two CYP2C19 LoF alleles were associated with a significantly marked risk of MACE than non-carriers (OR: 2.22, 95% CI: 1.60-3.09, p<0.00001). Furthermore, the increased risk of MACE remained markedly significant in Asian patients (OR: 2.03, 95% CI: 1.72-2.40, p<0.00001) and was less significant in western patients (OR: 1.35, 95% CI: 1.11-1.63, p=0.002). Bleeding events were not significantly different in carriers of CYP2C19 LoF alleles compared to non-carriers (OR: 1.11, 95% CI: 0.85-1.45, p=0.43).

CONCLUSION

Stable CAD patients treated with clopidogrel and carried CYP2C19 LoF alleles undergoing PCI were associated with significantly increased risk of MACE compared to non-carriers, even markedly significant for Asian patients.

Coronary Artery Disease and Endothelial Dysfunction: Novel Diagnostic and Therapeutic Approaches

Coronary artery disease is the leading cause of morbidity and mortality worldwide. The most common pathophysiologic substrate is atherosclerosis which is an inflammatory procedure that starts at childhood and develops throughout life. Endothelial dysfunction is associated with the initiation and progression of atherosclerosis and is characterized by the impaired production of nitric oxide. In general, endothelial dysfunction is linked to poor cardiovascular prognosis and different methods, both invasive and non-invasive, have been developed for its evaluation. Ultrasound evaluation of flow mediated dilatation of the branchial artery is the most commonly used method to assessed endothelial function while intracoronary administration of vasoactive agents may be also be used to test directly endothelial properties of the coronary vasculature. Endothelial dysfunction has also been the subject of therapeutic interventions. This review article summarizes the knowledge about evaluation of endothelial function in acute coronary syndromes and stable coronary artery disease and demonstrates the current therapeutic approaches against endothelial dysfunction.

Investigating the Effect of Demographics, Clinical Characteristics, and Polymorphism of MDR-1, CYP1A2, CYP3A4, and CYP3A5 on Clopidogrel Resistance

Clopidogrel is an antiplatelet agent that is indicated for cardiovascular emergencies and procedures. The drug, however, is subject to response variability leading to therapy resistance. In this research, we explored the demographic, clinical, and genetic factors associated with clopidogrel resistance. Data analysis among our 280 subjects receiving clopidogrel showed some risk factors that are significantly associated with clopidogrel resistance compared with responders. Those were: female sex (P = 0.021), advanced age (P = 0.011), obesity (P = 0.002), and higher body mass index (P = 0.008) and higher platelets count (P = 0.002). However, known polymorphisms of MDR-1, CYP1A2, CYP3A4, and CYP3A5 were not associated with treatment resistance when compared to responders to clopidogrel therapy. Knowledge about such risk factors might provide recommendation in the future about starting doses or monitoring recommendations.

CYP2C19 Genotype is an Independent Predictor of Adverse Cardiovascular Outcome in Iraqi Patients on Clopidogrel After Percutaneous Coronary Intervention

To determine the impact of CYP2C19 genotyping on the occurrence of major adverse cardiovascular events (MACE), in cohort of Iraqi patients on clopidogrel after percutaneous coronary intervention (PCI), a total of 201 Iraqi patients undergoing the latter procedure were enrolled. All enrollees had their CYP2C19 genotyped using polymerase chain reaction and reverse hybridization. Genotyping revealed that CYP2C19 *1, *17, *2, and *8 allele frequencies were, respectively, 0.604, 0.276, 0.117, and 0.0026. After the exclusion of those with 2 loss of function alleles, 186 patients were available for follow-up as long as they were on clopidogrel, or until MACE occurred, which was encountered in 8.6% after a median of 12 months. Among predictors associated with MACE was the carriage of one CYP2C19 loss of function allele {hazard ratio (HR) 8.6 [confidence interval (CI) 3.15-23.4]; P < 0.0005}, hypertension [HR 3.74 (CI 1.06-13.16); P = 0.04], reduced ventricular function [HR 3.88 (1.43-10.54); P = 0.008], and history of previous myocardial infarction [HR 4.9 (CI 1.48-11.33); P = 0.007] by univariate analysis, although only CYP2C19 genotype remained significant by multivariate analysis [HR 11.88 (CI 3.25-43.44); P < 0.0005]. The latter observation favors CYP2C19 genotype-guided antiplatelet therapy and extending the use of alternative antiplatelet drugs to those with single loss of function allele after percutaneous coronary intervention.

Pharmacogenomic Impact of CYP2C19 Variation on Clopidogrel Therapy in Precision Cardiovascular Medicine

Variability in response to antiplatelet therapy can be explained in part by pharmacogenomics, particularly of the CYP450 enzyme encoded by CYP2C19. Loss-of-function and gain-of-function variants help explain these interindividual differences. Individuals may carry multiple variants, with linkage disequilibrium noted among some alleles. In the current pharmacogenomics era, genomic variation in CYP2C19 has led to the definition of pharmacokinetic phenotypes for response to antiplatelet therapy, in particular, clopidogrel. Individuals may be classified as poor, intermediate, extensive, or ultrarapid metabolizers, based on whether they carry wild type or polymorphic CYP2C19 alleles. Variant alleles differentially impact platelet reactivity, concentration of plasma clopidogrel metabolites, and clinical outcomes. Interestingly, response to clopidogrel appears to be modulated by additional factors, such as sociodemographic characteristics, risk factors for ischemic heart disease, and drug-drug interactions. Furthermore, systems medicine studies suggest that a broader approach may be required to adequately assess, predict, preempt, and manage variation in antiplatelet response. Transcriptomics, epigenomics, exposomics, miRNAomics, proteomics, metabolomics, microbiomics, and mathematical, computational, and molecular modeling should be integrated with pharmacogenomics for enhanced prediction and individualized care. In this review of pharmacogenomic variation of CYP450, a systems medicine approach is described for tailoring antiplatelet therapy in clinical practice of precision cardiovascular medicine.