Tailored Thienopyridine therapy: no urgency for CYP2C19 genotyping

Current Strategies to Guide the Antiplatelet Therapy in Acute Coronary Syndromes

The role of antiplatelet therapy in patients with acute coronary syndromes is a moving target with considerable novelty in the last few years. The pathophysiological basis of the treatment depends on platelet biology and physiology, and the interplay between these aspects and clinical practice must guide the physician in determining the best therapeutic options for patients with acute coronary syndromes. In the present narrative review, we discuss the latest novelties in the antiplatelet therapy of patients with acute coronary syndromes. We start with a description of platelet biology and the role of the main platelet signal pathways involved in platelet aggregation during an acute coronary syndrome. Then, we present the latest evidence on the evaluation of platelet function, focusing on the strengths and weaknesses of each platelet's function test. We continue our review by describing the role of aspirin and P2Y12 inhibitors in the treatment of acute coronary syndromes, critically appraising the available evidence from clinical trials, and providing current international guidelines and recommendations. Finally, we describe alternative therapeutic regimens to standard dual antiplatelet therapy, in particular for patients at high bleeding risk. The aim of our review is to give a comprehensive representation of current data on antiplatelet therapy in patients with acute coronary syndromes that could be useful both for clinicians and basic science researchers to be up-to-date on this complex topic.

Contribution of exome sequencing to the identification of genes involved in the response to clopidogrel in cardiovascular patients

BACKGROUND

On-clopidogrel platelet reactivity (PR) is associated with the risk of thrombotic or bleeding event in selected populations of high-risk patients. PR is a highly heritable phenotype and a few variants of cytochrome genes, essentially CYP2C19, are associated with PR but only explain 5% to 12% of the variability.

OBJECTIVE

The aim of this study is to delineate genetic determinants of on-clopidogrel PR using high-throughput sequencing.

METHODS

We performed a whole exome sequencing of 96 low- and matched high-PR patients in a discovery cohort. Exomes from genes with variants significantly associated with PR were sequenced in 96 low- and matched high-PR patients from an independent replication cohort.

RESULTS

We identified 585 variants in 417 genes with an adjusted P value < .05. In the replication cohort, all top variants including CYP2C8, CYP2C18, and CYP2C19 from the discovery population were found again. An original network analysis identified several candidate genes of potential interest such as a regulator of PI3K, a key actor in the downstream signaling pathway of the P2Y12 receptor.

CONCLUSION

This study emphasizes the role of CYP-related genes as major regulators of clopidogrel response, including the poorly investigated CYP2C8 and CYP2C18.

Platelet Function Test Use for Patients with Coronary Artery Disease in the Early 2020s

In the field of antithrombotics, precision medicine is of particular interest, as it may lower the incidence of potentially life-threatening side effects. Indeed, antiplatelet drugs such as P2Y₁₂ inhibitors are one of the most common causes of emergency admissions for drug-related adverse events. The last ten years have seen a continuous debate on whether platelet function tests (PFTs) should be used to tailor antiplatelet drugs to cardiovascular patients. Large-scale randomized studies investigating the escalation of antiplatelet therapies according to the results of PFTs were mostly negative. Potent P2Y₁₂ inhibitors are recommended as a first-line treatment in acute coronary syndrome patients, bringing the bleeding risk at the forefront. De-escalation from prasugrel or ticagrelor to clopidogrel is now considered, with or without the use of a PFT. This review covers recent advances in escalation and de-escalation strategies based on PFTs in various clinical settings. It also describes the main features of the most popular platelet function tests as well as the potential added value of genetic testing. Finally, we detail practical suggestions on how PFTs could be used in clinical practice.

Complex Drug-Drug-Gene-Disease Interactions Involving Cytochromes P450: Systematic Review of Published Case Reports and Clinical Perspectives

Drug pharmacokinetics (PK) is influenced by multiple intrinsic and extrinsic factors, among which concomitant medications are responsible for drug-drug interactions (DDIs) that may have a clinical relevance, resulting in adverse drug reactions or reduced efficacy. The addition of intrinsic factors affecting cytochromes P450 (CYPs) activity and/or expression, such as genetic polymorphisms and diseases, may potentiate the impact and clinical relevance of DDIs. In addition, greater variability in drug levels and exposures has been observed when such intrinsic factors are present in addition to concomitant medications perpetrating DDIs. This variability results in poor predictability of DDIs and potentially dramatic clinical consequences. The present review illustrates the issue of complex DDIs using systematically searched published case reports of DDIs involving genetic polymorphisms, renal impairment, cirrhosis, and/or inflammation. Current knowledge on the impact of each of these factors on drug exposure and DDIs is summarized and future perspectives for the management of such complex DDIs in clinical practice are discussed, including the use of advanced Computerized Physician Order Entry (CPOE) systems, the development of model-based dose optimization strategies, and the education of healthcare professionals with respect to personalized medicine.

High On-Treatment Platelet Reactivity to Adenosine Diphosphate Predicts Ischemic Events of Minor Stroke and Transient Ischemic Attack

BACKGROUND

This study aimed to evaluate the relationship between thromboelastography adenosine diphosphate maximum amplitude (TEG-ADP_MA) and recurrent ischemic events in patients with minor ischemic stroke or high-risk transient ischemic attack (TIA).

METHODS

A total of 265 patients received dual antiplatelet therapy were consecutively enrolled. High on-treatment platelet reactivity (HTPR) to ADP was assessed by TEG-ADP_MA and detected the CYP2C19 genotype; recurrent ischemic events were followed up for 90 days after onset. The difference of recurrent ischemic events was analyzed with or without HTPR to ADP by the Kaplan-Meier, and further to determine the difference of recurrent ischemic events in each group according to TEG-ADP_MA-based tertile distribution.

RESULTS

A total of 23 (8.6%) patients had recurrent ischemic events. TEG-ADP_MA greater than or equal to 48 mm had good predictive value. Whether these patients were divided into 2 groups or 3 groups, the HTPR to ADP group had higher risk of recurrent ischemic events than the normal on-treatment platelet reactivity to ADP group by the Kaplan-Meier (all, P < .05). The tertile distribution map showed that the results of recurrent ischemic events were statistically significant in the third tertile group compared with the other two groups (all, P < .03); also, the third tertile group had a higher rate of carriers of at least 1 CYP2C19 reduced-function allele than the other two groups (P < .05).

CONCLUSIONS

In patients with minor ischemic stroke and high-risk TIA, the TEG-ADP_MA could predict recurrent ischemic events and has auxiliary effect on clinical decision-making.

The Personalization of Clopidogrel Antiplatelet Therapy: The Role of Integrative Pharmacogenetics and Pharmacometabolomics

Dual antiplatelet therapy of aspirin and clopidogrel is pivotal for patients undergoing percutaneous coronary intervention. However, the variable platelets reactivity response to clopidogrel may lead to outcome failure and recurrence of cardiovascular events. Although many genetic and nongenetic factors are known, great portion of clopidogrel variable platelets reactivity remain unexplained which challenges the personalization of clopidogrel therapy. Current methods for clopidogrel personalization include CYP2C19 genotyping, pharmacokinetics, and platelets function testing. However, these methods lack precise prediction of clopidogrel outcome, often leading to insufficient prediction. Pharmacometabolomics which is an approach to identify novel biomarkers of drug response or toxicity in biofluids has been investigated to predict drug response. The advantage of pharmacometabolomics is that it does not only predict the response but also provide extensive information on the metabolic pathways implicated with the response. Integrating pharmacogenetics with pharmacometabolomics can give insight on unknown genetic and nongenetic factors associated with the response. This review aimed to review the literature on factors associated with the variable platelets reactivity response to clopidogrel, as well as appraising current methods for the personalization of clopidogrel therapy. We also aimed to review the literature on using pharmacometabolomics approach to predict drug response, as well as discussing the plausibility of using it to predict clopidogrel outcome.

Implementation of a pharmacogenetic management service for postmyocardial infarction care in a community pharmacy

AIM

The purpose of this study was to pilot a multisite, proof-of-concept model where community pharmacists could engage patients and physicians to provide pharmacogenetic (PGt) testing and clinical decision support.

PATIENTS & METHODS

Patients with history of acute myocardial infarction and percutaneous coronary intervention with no prior history of CYP2C19 testing.

RESULTS

Four community pharmacies provided pharmacogenetic testing and medication therapy management services to 30 patients, resulting in eight recommendations for antiplatelet therapy adjustment.

CONCLUSION

Pharmacists involved in the study were able to facilitate antiplatelet therapy adjustments based on PGt data regardless of baseline antiplatelet drug selection. Whereas prior literature largely revolved around PGt management in the inpatient setting, this project supports the involvement of the community pharmacist in making PGt-based recommendations.

The pharmacogenetic control of antiplatelet response: candidate genes and CYP2C19

INTRODUCTION

Aspirin, clopidogrel, prasugrel and ticagrelor are antiplatelet agents for the prevention of ischemic events in patients with acute coronary syndromes (ACS), percutaneous coronary intervention (PCI) and other indications. Variability in response is observed to different degrees with these agents, which can translate to increased risks for adverse cardiovascular events. As such, potential pharmacogenetic determinants of antiplatelet pharmacokinetics, pharmacodynamics and clinical outcomes have been actively studied.

AREAS COVERED

This article provides an overview of the available antiplatelet pharmacogenetics literature. Evidence supporting the significance of candidate genes and their potential influence on antiplatelet response and clinical outcomes are summarized and evaluated. Additional focus is directed at CYP2C19 and clopidogrel response, including the availability of clinical testing and genotype-directed antiplatelet therapy.

EXPERT OPINION

The reported aspirin response candidate genes have not been adequately replicated and few candidate genes have thus far been implicated in prasugrel or ticagrelor response. However, abundant data support the clinical validity of CYP2C19 and clopidogrel response variability among ACS/PCI patients. Although limited prospective trial data are available to support the utility of routine CYP2C19 testing, the increased risks for reduced clopidogrel efficacy among ACS/PCI patients that carry CYP2C19 loss-of-function alleles should be considered when genotype results are available.

Genetic determined low response to thienopyridines is associated with higher systemic inflammation in smokers

AIM

To investigate whether the interactions of CYP2C19*2 and CYP2C19*17 with smoking are associated with the levels of P2Y12 receptor inhibition and CRP, in on-thienopyridine post-stenting patients.

METHODS & RESULTS

At 1-month follow-up, the interactions of smoking and CYP2C19 polymorphisms on the vasodilator-stimulated phosphoprotein - platelet reactivity index (VASP PRI), and CRP were explored in three metabolizing groups (1128 patients) as follow: poor metabolizers (*2 carriers/*17 noncarriers); intermediate metabolizers (*2 carriers/*17 carriers or *2 noncarriers/*17 noncarriers); and ultrarapidmetabolizers (*2 allele noncarriers/*17 carriers). The interactions of metabolizing status and smoking was significant for CRP (p = 0.001) but not for VASP PRI (p = 0.734).

CONCLUSION

Interaction between CYP2C19 polymorphisms and smoking modifies on-treatment CRP level of post-stenting, on-thienopyridine patients. This effect seems to be independent to the level of P2Y12 receptor inhibition.

Antiplatelet drugs and platelet reactivity: is it time to halt clinical research on tailored strategies?

Personalized medicine of antiplatelet drugs in cardiovascular patients has led to a significant enthusiasm. Indeed, numerous longitudinal studies showed an association between high platelet reactivity and the recurrence of ischemic events. The first small randomized trials of P2Y12 blockers tailored to each patient's platelet reactivity yielded encouraging reductions of coronary stent thrombosis in high-risk populations. The discovery of genetic variants contributing to the pharmacodynamic effect of clopidogrel has then paved the way toward a personalized antiplatelet therapy based on reliable and stable genetic tests. This enthusiasm was soon tempered by large interventional trials demonstrating that a platelet function testing-based strategy did not improve clinical outcome and that genetic variants discovered up to now only explained a small part of the pharmacodynamic effect of clopidogrel, thus limiting its clinical use. Looking back to the most recent trials, their target populations and the type of clinical setting, it seems that the one-size-fits all policy regarding antiplatelet drugs may be well acceptable for low-risk patients. On the contrary, integration of the clinical setting as well as other risk factors may help to identify subgroups of patients who could derive a benefit from a truly personalized management of antiplatelet therapy.

Treatment options for patients with poor clopidogrel response

A significant percentage of patients demonstrate a poor antiplatelet response to clopidogrel. With the emergence of testing for genetic variations in drug-metabolizing enzyme function and testing for platelet function, it is becoming more common to identify patients as poor responders to clopidogrel. This leaves the clinician in a difficult situation when confronted with a patient deemed to be a poor clopidogrel responder as there is no clear therapeutic strategy for treating these patients. In this situation, a number of alternatives to conventional dosing of clopidogrel have been investigated, including increasing the dosage of clopidogrel, switching from clopidogrel to either prasugrel or ticagrelor, or adding cilostazol to clopidogrel therapy. All of these options have demonstrated pharmacologic benefit in terms of greater antiplatelet effects compared with standard clopidogrel dosing in patients with high on-treatment platelet reactivity or a genetic loss-of-function variant of CYP2C19, the main enzyme responsible for clopidogrel activation. However, the impact of each of these alternative therapies on clinical outcomes is poorly understood. Early studies have not shown a clinical benefit by increasing the clopidogrel dosage or switching to prasugrel although there is still much to be discovered in this area. Of the alternatives to standard dosing of clopidogrel, switching to either prasugrel or ticagrelor has the most potential benefit, but again, there is limited evidence to support this practice in patients who demonstrate high on-treatment platelet reactivity while on clopidogrel although the evidence is somewhat more supportive in patients who have a CYP2C19 loss-of-function variant allele. The evidence for increasing the dosage of clopidogrel or adding cilostazol is the least supportive, making these alternatives difficult to justify. Given the limited evidence to support switching treatments, some providers may simply opt to continue standard dosing of clopidogrel pending the results of ongoing trials. Much research is needed and is currently underway in this area, which will be helpful in establishing future treatment protocols for patients with poor clopidogrel response.