Prevalence of poor biological response to clopidogrel

Influence of Genetic and Epigenetic Factors of P2Y12 Receptor on the Safety and Efficacy of Antiplatelet Drugs

PURPOSE

P2Y12 receptor inhibitors are drugs that decrease the risk of stent thrombosis and lower the long-term risk of non-stent-related myocardial infarction and stroke. They inhibit the binding of adenosine diphosphate (ADP) to the P2Y12 receptor and effectively reduce platelet reactivity. However, considerable variability in the pharmacodynamics response contributes to a failure of antiplatelet therapy; this phenomenon is especially notorious for older drugs, such as clopidogrel. Some genetic polymorphisms associated with these drugs' metabolic pathway, especially in the CYP2C19 gene, can significantly decrease antiplatelet efficacy. There are few reports on the variability stemming from the target of this drug class that is the P2Y12 receptor itself.

RESULTS AND CONCLUSION

This review summarizes the results of research that focus on the influence of P2Y12 genetic polymorphisms on the pharmacodynamics and the efficacy of P2Y12 inhibitors. We found that the conclusions of the studies are unequivocal, and despite several strong candidates, such as G52T (rs6809699) or T744C (rs2046934), they may not be independent predictors of the inadequate response to the drug. Most probably, P2Y12 genetic polymorphisms contribute to the effect exerted by other gene variants (such as CYP2C19*2/*3/*17), drug interactions, or patient habits, such as smoking. Also, epigenetic modifications, such as methylation or miRNA levels, may play a role in the efficacy of antiplatelet treatment.

Clinical prediction factors of nonchronic total occlusion lesion progression in patients with unstable angina receiving percutaneous coronary intervention for chronic total occlusion lesions

Background

In this study, we investigated clinical prediction factors of nonchronic total occlusion lesion (NCTOL) progression in patients who underwent percutaneous coronary intervention (PCI) for chronic total occlusion (CTO) lesions.

Methods

In total, 450 patients with unstable angina (mean age = 57.1 ± 9.2 years) who underwent PCI for CTO lesions between January 2016 and December 2018 at Beijing Anzhen Hospital were enrolled in this study. A clinical and angiographic follow-up examination was performed 12 months postoperatively. The patients were divided into NCTOL progression (145 cases) and control (305 cases) groups based on the outcome of the 12-month angiographic follow-up. The clinical and angiographic features of the participants were analyzed.

Results

The adenosine diphosphate-induced platelet aggregation (ADP-IPA) rate and levels of lipoprotein (a) (Lp(a)) in the NCTOL progression group were significantly higher than those in the control group (51.89 ± 14.81 vs. 39.63 ± 17.12, P < 0.01; 0.22 ± 0.26 vs. 0.14 ± 0.18, P < 0.05, respectively). Logistic regression showed that the ADP-IPA rate (odds ratio = 1.047, 95 % confidence interval: 1.014-1.082, P = 0.005) and Lp(a) (odds ratio = 11.972, 95 % confidence interval: 1.230-116.570, P = 0.033) were independent predictors of NCTOL progression. Partial correlation analysis demonstrated that the ADP-IPA rate was positively correlated with NCTOL progression (r = 0. 351, P < 0.001). Receiver operating characteristic curve showed that the boundary point of the ADP-IPA rate to predict NCTOL progression was 30 % (sensitivity, 86.2 %; specificity, 68.9 %).

Conclusions

NCTOL progression is an important cause of recurrent PCI in patients with coronary artery disease after PCI for CTO lesions. The ADP-IPA rate is a useful predictor for NCTOL progression in patients with unstable angina who undergo PCI for CTO lesions.

Racial differences in P2Y12 inhibitor responsiveness in patients undergoing neuro-endovascular procedures: A cohort from the Middle East

BACKGROUND

Data on P2Y12 inhibitors responsiveness from the middle east is scarce. We sought to investigate patient responsiveness to P2Y12 inhibitors within a cohort of major races that characterize the UAE population. The secondary objective was to assess risk factors for hyper and hypo-responsiveness in this population.

METHODS

We conducted a cross-sectional study on adults who received either clopidogrel or ticagrelor treatments and had platelet responsiveness testing before undergoing neuro-endovascular interventions at our quaternary care hospital between March 2015 and April 2019.

RESULTS

During the study period, 249 subjects met the inclusion criteria. Overall, 17.3 % were hyper-responsive and 25.7 % were hypo-responsive to P2Y12 inhibitors. When comparing between the P2Y12 inhibitors, rates of hyper-responsiveness were significantly higher to ticagrelor when compared to clopidogrel (11 versus 6 %, p = 0.02 respectively). Contrarily, hypo-responsiveness rates were significantly higher in clopidogrel treated patients compared to their ticagrelor treated counterparts (23 versus 2 %, p < .001 respectively). Patients of Middle-Eastern origin showed a significantly higher rate of hypo-responsiveness to both clopidogrel and ticagrelor when compared to other races (41.1 % and 26.7 %, P < 0.001 respectively). Asians showed the highest rates of hyper-responsiveness for both agents. Multivariate logistic regression analysis showed that proton pump inhibitors and statin combination, (OR: 6.39, 95 %CI [1.60, 25.392]), and Middle East vs. Indian subcontinent patients (OR: 4.67, 95 %CI [1.79-12.14]) were independent predictors of hypo-responsiveness to both P2Y12 inhibitors.

CONCLUSION

This study demonstrated a high rate of hypo-responsiveness to P2Y12 inhibitors in a UAE cohort of patients undergoing neuro-endovascular procedures. In addition, therapeutic responsiveness to P2Y12 inhibitors varied markedly based on the racial background. Future larger studies are needed to evaluate genetic variations that may contribute to this rate of hypo-responsiveness in our population.

The Role of Personalized Medicine in Companion Animal Cardiology

Cardiomyopathies remain one of the most common inherited cardiac diseases in both human and veterinary patients. To date, well over 100 mutated genes are known to cause cardiomyopathies in humans with only a handful known in cats and dogs. This review highlights the need and use of personalized one-health approaches to cardiovascular case management and advancement in pharmacogenetic-based therapy in veterinary medicine. Personalized medicine holds promise in understanding the molecular basis of disease and ultimately will unlock the next generation of targeted novel pharmaceuticals and aid in the reversal of detrimental effects at a molecular level.

Clopidogrel resistance is common in patients undergoing vascular and coronary interventions

OBJECTIVES

"Clopidogrel resistance," also defined as heightened platelet reactivity (HPR) while on clopidogrel therapy, may lead to a sub-optimal antiplatelet effect and a potential thrombotic event. There is limited literature addressing the prevalence of HPR in a large cohort of patients receiving either coronary or endovascular interventions.

METHODS

In a large integrated healthcare system, patients with a P2Y12 reaction units (PRU) test were identified. HPR was defined as a PRU ≥ 200 during clopidogrel therapy. Vascular and coronary interventions were identified utilizing CPT codes, HPR prevalence was calculated, and Fischer's exact test was used to determine significance.

RESULTS

From an initial cohort of 2,405,957 patients (October 2014 to January 2020), we identified 3301 patients with PRU tests administered. Of these, 1789 tests had a PRU ≥ 200 (HPR overall prevalence, 54%). We then identified 1195 patients who underwent either an endovascular or coronary procedure and had a PRU measurement. This corresponded to 935 coronary and 260 endovascular interventions. In the coronary cohort, the HPR prevalence was 54% (503/935). In the vascular cohort, the HPR prevalence was 53% (137/260); there was no difference between cohorts in HPR prevalence (p = 0.78).

CONCLUSION

"Clopidogrel resistance" or HPR was found to be present in nearly half of patients with cardiovascular disease undergoing intervention. Our data suggest HPR is more common in the cardiovascular patient population than previously appreciated. Evaluating patients for HPR is both inexpensive ($25) and rapid (< 10 min). Future randomized studies are warranted to determine whether HPR has a clinically detectable effect on revascularization outcomes.

Choline and trimethylamine N-oxide impair metabolic activation of and platelet response to clopidogrel through activation of the NOX/ROS/Nrf2/CES1 pathway

BACKGROUND

Trimethylamine N-oxide (TMAO), a gut microbe-generated metabolite, elicits thrombotic events by enhancing platelet reactivity; however, no studies have reported the effects of TMAO on the metabolism of and response to clopidogrel.

OBJECTIVES

To determine whether choline and TMAO could significantly impair metabolic activation of and platelet response to clopidogrel in choline- or TMAO-fed mice and the mechanisms involved.

METHODS

Male mice were fed with vehicle control (Ctrl), TMAO, choline alone or in combination with 3,3-dimethyl-1-butanol, N-acetyl-L-cysteine, or ML385 for 14 days and then treated with Ctrl or a single oral dose of clopidogrel. Plasma TMAO, protein levels of clopidogrel-metabolizing enzymes in the liver, plasma concentrations of clopidogrel and its metabolites, and adenosine diphosphate-induced platelet aggregation and activation were measured. In addition, HepG2 cells were treated with Ctrl or TMAO alone or in combination with N-acetyl-L-cysteine, ML385, or apocynin, and CES1, reactive oxygen species (ROS), and Nrf2 protein levels were measured, respectively.

RESULTS

TMAO significantly increased Ces1 protein expression and activity and clopidogrel hydrolysis in the liver as well as intracellular ROS and CES1 levels and Nrf2 nucleus translocation in HepG2 cells but decreased the formation of clopidogrel active metabolite and impaired platelet response to clopidogrel. Furthermore, concomitant use of 3,3-dimethyl-1-butanol, N-acetyl-L-cysteine, or ML385 effectively reversed choline- or TMAO-induced impairment of inhibition of platelet aggregation by clopidogrel in mice, respectively.

CONCLUSIONS

Choline and TMAO impair the metabolic activation of and platelet response to clopidogrel through the activation of the NOX-dependent ROS/Nrf2/CES1 pathway, suggesting novel strategies for overcoming clopidogrel resistance from bench to bedside.

Silk Vista Baby flow diverter stent for ruptured intracranial aneurysms: a retrospective observational study

PURPOSE

Flow diversion changed the approach to complex intracranial aneurysms, leading to a widespread use and a rapid technological evolution. Indeed, indications continued to expand, including ruptured intracranial aneurysms in selected cases. Recently, new devices have been designed specifically to target smaller vessels. Therefore, we conducted a multicenter study to evaluate clinical outcome, complications, and occlusion rate of patients with ruptured aneurysms treated with new generation low profile Silk Vista Baby (SVB) flow diverter stent (FD).

METHODS

We performed a retrospective observational study on consecutive patients who underwent treatment with SVB for ruptured aneurysms at 12 Italian centers. Primary end point was favorable clinical outcome rate, defined as modified ranking score (mRS) of 0-2 at the 3 months. Secondary outcomes were complication rate, aneurysm re-rupture, and complete aneurysm occlusion at last radiological follow-up.

RESULTS

Twenty-five patients were included; at 3 months' follow-up, 19 patients (79.1%) had favorable clinical outcome (mRS 0-2). Three patients (12.5%) died during follow-up. In-stent thrombosis occurred in two cases (8.3%), managed with glycoprotein IIb/IIIA and intra-stent angioplasty, without clinical consequences. In 18 (85.7%) patients, complete occlusion at 3 months was demonstrated. No rebleeding occurred during follow-up. Presentation with unfavorable World Federation of Neurosurgical Societies grading system (WFNS) and posterior circulation location were both significantly correlated with unfavorable clinical outcome (p = 0.005 and p = 0.02).

CONCLUSIONS

Our data suggests that low profile FD treatment of ruptured intracranial aneurysms located distally of the circle of Willis is feasible. New generation low profile FD may represent an alternative option in carefully selected cases.

Antiplatelet response to clopidogrel is associated with a haplotype in CYP2C19 gene in Pakistani patients

Clopidogrel, an antiplatelet drug, is frequently prescribed to patients diagnosed with ischemic diseases such as those suffering from acute coronary syndromes or ischemic stroke. Despite the drug being effective in majority of the patients, some still experience ischemic events early in the treatment which might be due to poor platelet inhibition. This study aims to investigate the association of cytochrome P450 2C19 (CYP2C19) loss-of-function polymorphisms, haplotypes as well as a wide range of clinical and demographic variables with platelet aggregation phenotypes to clopidogrel in a Pakistani cohort. The study comprised of a total of 120 patients diagnosed with cardiovascular diseases and were treated with clopidogrel. Antiplatelet response to clopidogrel was monitored by Helena AggRAM (HL-2-1785P) and patients with maximal platelet aggregation more than 50% were categorized as low responders and those with less than 50% as high responders. Our results show that 56.6% of patients were homozygous for the CYP2C19 wild-type allele, 38.3% of patients possessed one copy of the CYP2C19*2 allele and 5% of patients possessed both CYP2C19*2 alleles. No CYP2C19*3 allele was found in our patient cohort. There was no statistically significant difference between the high and low responder groups to clopidogrel in terms of extensive, intermediate and poor metabolizer genotypes. However, haplotype (H1), leukocyte count, random blood glucose, and history of diabetes mellitus was associated with the antiplatelet response to clopidogrel. The prevalence of clopidogrel resistance in our population was in line with that reported for other regional and global populations.

Platelet transmission electron microscopy for the assessment of poor biological response to antiplatelet agent: pilot descriptive and prospective study - ELECTROSTROKE

INTRODUCTION

Ischaemic stroke is the leading cause of adult disability. Thus, a strategy based on an efficient antiplatelet therapy has been developed. The monitoring of antiplatelet therapy is now limited to high risk and poor prognosis patients. Indeed, the biological monitoring of the antiplatelet therapy with available platelet function assays do not provide a global integrative approach. Platelet transmission electron microscopy, recently validated for assessing distinct ultrastructural abnormalities is a reliable morphological platelet structural analysis tool which could be used to collect all the ultrastructural platelet characteristics and assess the degree of activation of platelets.

METHODS AND ANALYSIS

Our pilot prospective and descriptive study will include 50 consecutive patients hospitalized for an ischaemic stroke. We expect to identify ultrastructural characteristics that will be correlated with the degree of platelet activation to guide clinicians in decision making regarding the antiplatelet therapy strategy.

ETHICS AND DISSEMINATION

The French Ethics Committee (comité de protection des personnes d'Ile-de-France VII) approved the information notice that will be given to participants and the protocol of this trial (protocol No 21-031).The results of the trial will be disseminated through scientific publications.

TRIAL REGISTRATION NUMBER

NCT05004233.

Dosage optimization of clopidogrel via a precision medicine approach: the way forward

Clopidogrel is a prodrug chiefly metabolized by the hepatic isoenzyme CYP2C19 to its active metabolite that inhibits the platelet aggregation. It has been proven in many populations that the genetic polymorphism of CYP2C19 has influence on the pharmacokinetic and or pharmacodynamics of this drug and resulting in high inter-individual variability in the treatment outcomes. As CYP2C19 genetic polymorphism is highly prevalent among the Asian population, the influence of the same on the pharmacokinetics and; thereby, the pharmacodynamics of clopidogrel needs more attention. Using the pharmacogenetic information for drug therapy could help overcome these issues and to optimize the dosage regimen of clopidogrel, this review advocates the precision medicine approach for reducing the clopidogrel resistance and adverse cardiovascular events.

Intensified antiplatelet therapy in patients after percutaneous coronary intervention with high on-treatment platelet reactivity: the OPTImal Management of Antithrombotic Agents (OPTIMA)-2 Trial

High on-treatment platelet reactivity (HOPR) is associated with increased risk of cardiovascular events in patients undergoing percutaneous coronary intervention (PCI). We randomised post-PCI patients with HOPR after 5 days of standard dual antiplatelet therapy (DAPT) to intensified therapy with aspirin 100 mg once daily in combination with either clopidogrel 150 mg once daily, clopidogrel 75 mg once daily plus cilostazol 100 mg twice daily, ticagrelor 90 mg twice daily, or standard therapy with clopidogrel 75 mg once daily (STD) for 1 month, after which all patients were switched to standard DAPT for a further 11 months. The primary outcome was residual HOPR rate at 1 month. We screened 1724 patients with light transmission aggregation studies and randomised 434 with HOPR. At 1 month the proportion of patients with persistent HOPR was significantly lower in the intensified therapy groups compared with STD group. Compared to the group receiving STD therapy, those receiving intensified therapy had significantly lower rate of major adverse cardiovascular events (MACE) at both 1 month and 12 months with no significant increase in bleeding. In patients with post-PCI HOPR, 1 month of intensified antiplatelet therapy provides greater platelet inhibition and improves outcomes without increasing bleeding. Clinical Trial Registration URL: http://www.clinicaltrials.gov; Unique Identifier: NCT01955200.

Comparison of Blister Aneurysm Treatment Techniques: A Systematic Review and Meta-Analysis

OBJECTIVE

Blood blister aneurysms are small, thin-walled, rapidly growing side-wall aneurysms that have proved particularly difficult to treat, and evidence-based guidance for treatment strategies is lacking. A systematic review and meta-analysis was performed to aggregate the available data and compare the 3 primary treatment modalities.

METHODS

We performed a comprehensive literature search according to PRISMA guidelines followed by an indirect meta-analysis that compares the safety and efficacy of surgical, flow-diverting stents (FDS), and other endovascular approaches for the treatment of ruptured blood blister aneurysms.

RESULTS

A total of 102 studies were included for quantitative synthesis, with sample sizes of 687 treated surgically, 704 treated endovascularly without FDS, and 125 treated via flow diversion. Comparatively, FDS achieved significantly reduced rates of perioperative retreatment compared with both surgical (P = 0.025) and non-FDS endovascular (P < 0.001). The FDS subgroup also achieved a significantly lower incidence of perioperative rebleed (P < 0.001), perioperative hydrocephalus (P = 0.012), postoperative infarction (P = 0.002), postoperative hydrocephalus (P < 0.001), and postoperative vasospasm (P = 0.002) compared with those patients in the open surgical subgroup. Although no significant differences were found among groups on the basis of functional outcomes, angiographic outcomes detailed by rates of radiographic complete occlusion were highest for surgical (90.7%, 262/289) and FDS (89.1%, 98/110) subgroups versus the non-FDS endovascular subgroup (82.7%, 268/324).

CONCLUSIONS

Flow diversion seems to be an effective treatment strategy for ruptured blood blister aneurysms, with lower rates of perioperative complications compared with surgical and other endovascular techniques, but studies investigating long-term outcomes after flow diversion warrant further study.

miR-204-5p and Platelet Function Regulation: Insight into a Mechanism Mediated by CDC42 and GPIIbIIIa

BACKGROUND

 Several platelet-derived microRNAs are associated with platelet reactivity (PR) and clinical outcome in cardiovascular patients. We previously showed an association between miR-204-5p and PR in stable cardiovascular patients, but data on functional mechanisms are lacking.

AIMS

 To validate miR-204-5p as a regulator of PR in platelet-like structures (PLS) derived from human megakaryocytes and to address mechanistic issues.

METHODS

 Human hematopoietic stem cells were differentiated into megakaryocytes, enabling the transfection of miR-204-5p and the recovery of subsequent PLS. The morphology of transfected megakaryocytes and PLS was characterized using flow cytometry and microscopy. The functional impact of miR-204-5p was assessed using a flow assay, the quantification of the activated form of the GPIIbIIIa receptor, and a fibrinogen-binding assay. Quantitative polymerase chain reaction and western blot were used to evaluate the impact of miR-204-5p on a validated target, CDC42. The impact of CDC42 modulation was investigated using a silencing strategy.

RESULTS

 miR-204-5p transfection induced cytoskeletal changes in megakaryocytes associated with the retracted protrusion of proPLS, but it had no impact on the number of PLS released. Functional assays showed that the PLS produced by megakaryocytes transfected with miR-204-5p were more reactive than controls. This phenotype is mediated by the regulation of GPIIbIIIa expression, a key contributor in platelet-fibrinogen interaction. Similar results were obtained after CDC42 silencing, suggesting that miR-204-5p regulates PR, at least in part, via CDC42 downregulation.

CONCLUSION

 We functionally validated miR-204-5p as a regulator of the PR that occurs through CDC42 downregulation and regulation of fibrinogen receptor expression.

The dawn of aspirin free strategy after short term dual antiplatelet for percutaneous coronary intervention: meta-analysis of randomized controlled trials

There is still a debate about the safety and efficacy of an aspirin free strategy after percutaneous coronary intervention (PCI). Hence, we performed a meta-analysis comparing aspirin free strategy to dual antiplatlets therapy (DAPT). Randomized trials (RCTs) comparing aspirin free strategy to DAPT in patients who received PCI were included. The primary outcome of interest was bleeding, defined per the Bleeding Academic Research Consortium (BARC). Secondary outcomes included major adverse cardiovascular and cerebrovascular events (MACE); defined as all-cause mortality, myocardial infarction or stroke, the individual component of MACE and stent thrombosis. A total of 4 RCTs with 29,089 patients were included. There was significant reduction in BARC 2,3 or 5 bleeding events in patients who were treated with aspirin free strategy versus DAPT (HR 0.61, 95% CI 0.39-, p = 0.03, I² = 89%). Moreover, although there was a trend of reduced major bleeding (BARC 3 or 5) outcomes in the aspirin free strategy group compared to the DAPT group, this did not achieve statistical significance (HR 0.63, 95% CI 0.37-1.06, p = 0.08, I² = 795). Additionally, there was no difference between the aspirin free strategy and DAPT in term of MACE (HR 0.92, 95% CI 0.82-1.03, p = 0.13, I² = 0%), all-cause mortality (HR 0.89, 95% CI 0.77-1.04, p = 0.15, I² = 0%), MI (HR 0.89, 95% CI 0.74-1.08, p = 0.24, I² = 0%), stroke (HR 1.13, 95% CI 0.65-1.99, p = 0.66, I² = 60%) or stent thrombosis (HR 0.1.01, 95% CI 0.83-1.22, p = 0.93, I² = 0%). Aspirin free strategy is as effective as DAPT in reducing MACE with better safety profile in term of bleeding.

CHADS2 and CHA2DS2-VASc scores as predictors of platelet reactivity in acute coronary syndrome

BACKGROUND

Platelet function testing (PFT) in patients treated with P2Y₁₂ inhibitors has been widely evaluated for the prediction of stent thrombosis, myocardial infarction, and bleeding events following percutaneous coronary intervention (PCI) in acute coronary syndrome (ACS). Thus, PFT-guided treatment could positively affect patient outcomes. Data regarding clinical parameters for predicting platelet reactivity in ACS patients are limited. Therefore, our study aims to evaluate CHADS2 and CHA2DS2-VASc scores as predictors for platelet reactivity in ACS patients.

METHODS

Two hundred and ninety-one consecutive patients who underwent PCI and were treated with aspirin and clopidogrel due to ACS were tested for their CHADS2, CHA2DS2-VASc scores and platelet reactivity using adenosine diphosphate (ADP)-induced aggregation (conventional aggregometry). Patients were classified into groups according to their CHADS2 and CHA2DS2-VASc scores. Low-risk group (0-1 score) for CHADS2 and CHA2DS2-VASc scores and high-risk group (2-6, 2-9) for CHADS2 and CHA2DS2-VASc scores, respectively. Furthermore, platelet reactivity in each group were compared (low CHADS2 group vs high CHADS2 group, and low CHA2DS2-VASc vs high CHA2DS2-VASc). Platelet reactivity was defined as low platelet reactivity (<19 U), optimal platelet reactivity [(OPR); 19-46 U], and high on-treatment platelet reactivity [(HPR); >46 U]. Thereafter receiver operating characteristic curve analysis was conducted to verify whether CHADS2 and CHA2DS2-VASc scores could predict platelet reactivity.

RESULTS

Low CHADS2 and CHA2DS2-VASc scores were significantly correlated with lower mean platelet ADP-induced aggregation as compared with high CHADS2 and CHA2DS2-VASc scores [45.5 U (± 16) vs. 54.8 U (±15) and 44.2 U (±16) vs. 51.0 U (±17), respectively, p = 0.01 for both].

CONCLUSION

In ACS patients treated with clopidogrel following PCI, high CHADS2 and CHA2DS2-VASc scores correlated with HPR and lower scores correlated with OPR. Further studies are needed to evaluate our findings' clinical implications.

Towards Personalized Antithrombotic Treatments: Focus on P2Y12 Inhibitors and Direct Oral Anticoagulants

Oral anticoagulants and antiplatelet drugs are commonly prescribed to lower the risk of cardiovascular diseases, such as venous and arterial thrombosis, which represent the leading causes of mortality worldwide. A significant percentage of patients taking antithrombotics will nevertheless experience bleeding or recurrent ischemic events, and this represents a major public health issue. Cardiovascular medicine is now questioning the one-size-fits-all policy, and more personalized approaches are increasingly being considered. However, the available tools are currently limited and they are only moderately able to predict clinical events or have a significant impact on clinical outcomes. Predicting concentrations of antithrombotics in blood could be an effective means of personalization as they have been associated with bleeding and recurrent ischemia. Target concentration interventions could take advantage of physiologically based pharmacokinetic (PBPK) and population-based pharmacokinetic (POPPK) models, which are increasingly used in clinical settings and have attracted the interest of governmental regulatory agencies, to propose dosages adapted to specific population characteristics. These models have the benefit of combining parameters from different sources, such as experimental in vitro data and patients' demographic, genetic, and physiological in vivo data, to characterize the dose-concentration relationships of compounds of interest. As such, they can be used to predict individual drug exposure. In the near future, these models could therefore be a valuable means of predicting personalized antithrombotic blood concentrations and, hopefully, of preventing clinical non-response or bleeding in a given patient. Existing approaches for personalization of antithrombotic prescriptions will be reviewed using practical examples for P2Y₁₂ inhibitors and direct oral anticoagulants. The review will additionally focus on the existing PBPK and POPPK models for these two categories of drugs. Lastly, we address potential scenarios for their implementation in clinics, along with the main limitations and challenges.

Body weight, CYP2C19, and P2Y12 receptor polymorphisms relate to clopidogrel resistance in a cohort of Chinese ischemic stroke patients with aspirin intolerance

PURPOSE

Dual antiplatelet therapy (DAT) with clopidogrel and aspirin is not suitable for clopidogrel resistance (CR) patients with aspirin intolerance. To investigate the prevalence of CR in patients with aspirin intolerance after ischemic stroke (IS) and to assess the relationship between CR and CYP2C19, P2Y12 receptor genotypes in patients with aspirin intolerance after IS.

METHODS

We enrolled 126 IS patients with aspirin intolerance from Han Chinese in Shangqiu from January 2016 to November 2018. All IS patients with aspirin intolerance were treated with clopidogrel for 7 days. Adenosine diphosphate-induced platelet inhibition rate was measured by thrombelastography (TEG) mapping assay. The SNPs CYP2C19*2, CYP2C19*3, and P2Y12 receptor (52 G >T) were genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique. Binary logistic regression analyses were performed using SPSS version 20.0.

RESULTS

The prevalence of CR in patients with aspirin intolerance after IS was approximately 31.0%. Multivariate regression analysis showed that body weight (OR 1.091 (95% CI 1.031-1.155), p = 0.003), CYP2C19 phenotype intermediate metabolizer (IM) (OR 3.820 (95% CI 1.021-14.288), p = 0.046), and CYP2C19 phenotype poor metabolizer (PM) (OR 14.481 (95% CI 2.791-75.129), p = 0.001) significantly increased the risk of CR and P2Y12 receptors (52 G >T) (OR 3.498 [95% CI 1.251-9.784], p = 0.017) increased the risk of CR.

CONCLUSIONS

The patients with high body weight, the CYP2C19 phenotypes, and P2Y12 receptor (52 G >T) variant alleles are at risk of CR during clopidogrel treatment in Chinese IS patients with aspirin intolerance. The higher body weight and relevant polymorphisms may help to predict CR in Chinese IS patients with aspirin intolerance.

Population Pharmacokinetic/Pharmacodynamic Modeling of Glenzocimab (ACT017) a Glycoprotein VI Inhibitor of Collagen-Induced Platelet Aggregation

Glenzocimab (ACT017) is a humanized monoclonal antigen‐binding fragment (Fab) directed against the human platelet glycoprotein VI, a key receptor for collagen and fibrin that plays a major role in thrombus growth and stability. Glenzocimab is being developed as an antiplatelet agent to treat the acute phase of ischemic stroke. During a phase I study in healthy volunteers, the population pharmacokinetics (PK) and pharmacodynamics (PD) of glenzocimab were modeled using Monolix software. The PK/PD model thus described glenzocimab plasma concentrations and its effects on ex vivo collagen‐induced platelet aggregation. Glenzocimab was found to have dose‐proportional, 2‐compartmental PK with a central distribution volume of 4.1 L, and first and second half‐lives of 0.84 and 9.6 hours. Interindividual variability in clearance in healthy volunteers was mainly explained by its dependence on body weight. The glenzocimab effect was described using an immediate effect model with a dose‐dependent half maximal inhibitory concentration: Larger doses resulted in a stronger effect at the same glenzocimab plasma concentration. The mechanism of the overproportional concentration effect at higher doses remained unexplained. PK/PD simulations predicted that 1000‐mg glenzocimab given as a 6‐hour infusion reduced platelet aggregation to 20% in 100% of subjects at 6 hours and in 60% of subjects at 12 hours after dosing. Simulations revealed a limited impact of creatinine clearance on exposure, suggesting that no dose adjustments were required with respect to renal function. Future studies in patients with ischemic stroke are now needed to establish the relationship between ex vivo platelet aggregation and the clinical effect.

High on-clopidogrel platelet reactivity in ischaemic stroke or transient ischaemic attack: Systematic review and meta-analysis

OBJECTIVES

To assess the prevalence of high on-clopidogrel platelet reactivity (HCPR) in patients with ischaemic stroke or transient ischaemic attack (IS/TIA), their outcome and genetic basis of on-treatment response variability in IS/TIA patients.

METHODS

We conducted a comprehensive search of PubMed and EMBASE from their inceptions to March 9, 2019. Studies that reported absolute numbers/percentages of HCRP at any time point after IS/TIA onset evaluated with any type of platelet function tests, clinical outcomes and genotyping data were included.

RESULTS

Among 21 studies of 4312 IS/TIA patients treated with clopidogrel, the pooled prevalence of HCPR was 28% (95%CI: 24-32%; high heterogeneity: I² = 88.2%, p < 0.001). Heterogeneity degree diminished across groups defined by the HCPR testing method. Clopidogrel non-responder IS/TIA patients had poorer outcome compared to responders (RR = 2.09, 95%CI: 1.61-2.70; p = 0.036; low heterogeneity across studies: I² = 27.4%, p = 0.210). IS/TIA carriers of CYP2C19*2 or CYP2C19*3 loss of function alleles had a higher risk of HCPR compared to wild type (RR = 1.69, 95%CI: 1.47-1.95; p < 0.001; I² = 0.01%, p = 0.475).

CONCLUSIONS

This systematic review shows a high prevalence of clopidogrel resistance in IS/TIA and poor outcome in these patients. CYP2C19 polymorphisms may potentially influence clopidogrel resistance.

Impact of Platelet Endothelial Aggregation Receptor-1 Genotypes on Platelet Reactivity and Early Cardiovascular Outcomes in Patients Undergoing Percutaneous Coronary Intervention and Treated With Aspirin and Clopidogrel

BACKGROUND

The genetic determinants of response to clopidogrel and aspirin are incompletely characterized. Recently, PEAR1 (platelet endothelial aggregation receptor-1) rs12041331 polymorphism has been shown to influence the platelet reactivity, but its impact on cardiovascular outcomes remains unclear in patients treated with antiplatelet agents.

METHODS AND RESULTS

In this prospective cohort study, 2439 Chinese patients with acute coronary syndrome or stable coronary artery disease undergoing coronary stent implantation and receiving clopidogrel and aspirin were consecutively recruited. Their platelet reactivity was determined by light transmission aggregometry at 5 and 30 days after coronary intervention. Genotyping was performed using an improved multiplex ligation detection reaction technique. All patients completed a 30-day follow-up for clinical outcomes. Genotyping for PEAR1 showed 768 (38.3%) GG homozygotes, 941 (46.9%) GA heterozygotes, and 298 (14.8%) AA homozygotes. The 30-day incidence of major adverse cardiovascular events, the composite of cardiovascular death, nonfatal myocardial infarction, and ischemic stroke were significantly higher in AA homozygotes than in non-AA homozygotes (adjusted hazard ratio, 2.78; 95% CI, 1.13-6.82; P=0.026), irrespective of CYP2C19*2 loss-of-function polymorphism and known outcome predictors including age, sex, smoking, and diabetes mellitus. The ADP-induced platelet aggregation was significantly lower in AA homozygotes than that in GG homozygotes at both time points, although no significant difference was found for the arachidonic acid-induced platelet aggregation among the 3 groups.

CONCLUSIONS

About 15% of Chinese patients undergoing coronary stent implantation were AA homozygotes for PEAR1 rs12041331. These patients had ≈3-fold increase in short-term major adverse cardiovascular events risk compared with non-AA homozygotes, and the adverse clinical outcome is unlikely to be mediated by suboptimal pharmacological response to aspirin or clopidogrel.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov . Unique identifier: NCT01968499.

A 70-Year-Old Female with Unexpected Platelet Function Testing Results

A 70-year-old female with a history of hypertension and left A2 segment aneurysm was scheduled for pipeline embolization device (PED) placement. Preinterventional antiplatelet prophylaxis included aspirin and ticagrelor. Unexpectedly, after 13 days of treatment, VerifyNow showed a P2Y12 reaction unit (PRU) value of 216, approximately >5 times the mean PRU of other patients on aspirin and ticagrelor. We confirmed platelet reactivity and ticagrelor resistance with light transmission aggregometry. Antiplatelet therapy was switched to prasugrel, and aspirin was continued. Eight days later, the P2Y12 reaction value (PRU) was 164. PED was placed without complications. Unlike clopidogrel, ticagrelor is a direct P2Y12 inhibitor that does not require metabolism to an active metabolite. Ticagrelor resistance is very rarely reported. To the best of our knowledge, there has been no case of ticagrelor resistance reported in the context of pre-PED placement prophylaxis.

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.

Stratified Approaches to Antiplatelet Therapies Based on Platelet Reactivity Testing

Antiplatelet therapy with P2Y₁₂ receptor inhibitors (clopidogrel, prasugrel, ticagrelor, cangrelor) is a cornerstone of medical therapy after percutaneous coronary interventions. Significant prevalence of high on-treatment platelet reactivity (HTPR) on clopidogrel treatment led to introduction of more potent P2Y₁₂ inhibitors: prasugrel (a third generation thienopyridine), ticagrelor, and cangrelor (cyclopentyl-triazolo-pyrimidines). Nevertheless, more potent platelet inhibition and resulting low on-treatment platelet reactivity (LTPR) has led to increased risk of major bleeding events. These limitations resulted in a need for an individualized antiplatelet therapy approach. This review discusses the current role and future perspectives of diagnostic tools such as platelet function testing to optimize antiplatelet therapy with a focus on deescalating therapies to reduce bleeding risks.

The effect of CYP2C19 genotype-guided antiplatelet therapy on outcomes of selective percutaneous coronary intervention patients: an observational study

Aim: To observe if personalized antiplatelet therapy according to the CYP2C19 phenotype can improve the outcomes of patients receiving selective percutaneous coronary intervention (PCI). Methods: In this observational study, 677 Chinese patients undergoing selective PCI were divided into gene group (n = 369) and conventional group (n = 308), and given antiplatelet therapy according to the CYP2C19 genotype or clinical features, respectively. Incidence of MACE (death, non-fatal myocardial infarction, and unplanned repeat revascularization) and bleeding was compared between the two groups after 18 months. Results: Diabetes, heart dysfunction and SYNTAX score (>15), but not routinely CYP2C19 genotype test-guided antiplatelet therapy, were associated with MACE. The incidence of bleeding showed no difference. Conclusion: CYP2C19 phenotype-guided antiplatelet therapy may have no influence on the outcomes of selective PCI patients. Clinical features-guided antiplatelet therapy may be reasonable.

Genotyping and phenotyping CYP3A4\CYP3A5: no association with antiplatelet effect of clopidogrel

The objective of this study was to determine the impact of polymorphism of CYP3A subfamily isoenzymes (allelic variants of CYP3A4*22 and CYP3A5*3) on the efficacy clopidogrel in patients with an acute coronary syndrome (ACS), who have undergone percutaneous coronary intervention (PCI). Platelet activity was determined on a VerifyNow P2Y12 test system in 81 patients with ACS aged 37-91 who had PCI. The activity of CYP3A4/5 was expressed as the ratio of the concentrations of cortisol and 6β-hydroxycortisol was performed by using high performance liquid chromatography. Genotyping was performed by using real-time polymerase real-time chain reaction. The frequencies for the CYP3A5 gene, rs 776746, were identified as follows: 77 (95.1%)-CC, 4 (4.9%)-CT; the allele frequencies by loci for the CYP3A4, rs rs35599367, were as follows: 78 (96.3%)-GG, 3 (3.7%)-AG. There was no statistically significant genotype-dependent difference between the presence of a minor T and G alleles and the presence of clopidogrel resistance (OR 3.53; 95% CI 0.46-26.94; p = 0.233 and p = 0.443, respectively). The average level of the metabolic relationship (6β-hydroxycortisol/cortisol) between the clopidogrel-resistant group and the normal platelet reactivity group was not statistically significantly different: 3.3 ± 2.8 versus 3.2 ± 3.2; p = 0.947. So, the activity of CYP3A4/5 was not related to platelet aggregation rates in this model. Genotyping and phenotyping CYP3A4\CYP3A5 does not predict the antiplatelet effect of clopidogrel. More extensive research is required to establish their clinical relevance.

Periprocedural Neuroendovascular Antiplatelet Strategies for Thrombosis Prevention in Clopidogrel-Hyporesponsive Patients

Patients undergoing neuroendovascular procedures such as cerebral aneurysm coiling and intracranial stent deployment are frequently treated with antiplatelet agents to prevent thrombotic complications. The combination of aspirin and a P2Y12 inhibitor such as clopidogrel is often initiated days before elective procedures or as loading doses for emergent procedures; however, some patients may still experience thrombotic complications. Patients identified as clopidogrel hyporesponders are more likely to experience poor outcomes and may require changes to their regimens. Historically, high-dose clopidogrel regimens were used in response to subtherapeutic results of platelet function assays and point-of-care testing despite limited supporting data. Recently, more data have emerged using alternative P2Y12 inhibitors such as prasugrel and ticagrelor. Dosing for neuroendovascular conditions is often extrapolated from the cardiac literature, although outcomes in cardiac patients may not be relevant to neurologic patients, making prophylactic treatment recommendations challenging for these patients. This review summarizes the literature for antiplatelet prophylaxis in patients undergoing neuroendovascular device placement, focusing on alternative regimens for clopidogrel hyporesponders.

Population-scale genomics-Enabling precision public health

The current excitement for affordable genomics technologies and national precision medicine initiatives marks a turning point in worldwide healthcare practices. The last decade of global population sequencing efforts has defined the enormous extent of genetic variation in the human population resulting in insights into differential disease burden and response to therapy within and between populations. Population-scale pharmacogenomics helps to provide insights into the choice of optimal therapies and an opportunity to estimate, predict and minimize adverse events. Such an approach can potentially empower countries to formulate national selection and dosing policies for therapeutic agents thereby promoting public health with precision. We review the breadth and depth of worldwide population-scale sequencing efforts and its implications for the implementation of clinical pharmacogenetics toward making precision medicine a reality.

Pharmacogenetic association study on clopidogrel response in Puerto Rican Hispanics with cardiovascular disease: a novel characterization of a Caribbean population

Introduction

High on-treatment platelet reactivity (HTPR) to clopidogrel imparts an increased risk for ischemic events in adults with coronary artery disease. Platelet reactivity varies with ethnicity and is influenced by both clinical and genetic variables; however, no clopidogrel pharmacogenetic studies with Puerto Rican patients have been reported. Therefore, we sought to identify clinical and genetic determinants of on-treatment platelet reactivity in a cohort of Puerto Rican patients with cardiovascular disease.

Methods

We performed a retrospective study of 111 patients on 75 mg/day maintenance dose of clopidogrel. Patients were allocated into 2 groups: Group I, without HTPR; and Group II, with HTPR. Platelet function was measured ex vivo using the VerifyNow® P2Y12 assay and HTPR was defined as P2Y12 reaction units (PRU) ≥230. Genotyping testing was performed using Taqman^® Genotyping Assays.

Results

The mean PRU across the cohort was 203±61 PRU (range 8–324), and 42 (38%) patients had HTPR. Multiple logistic regression showed that 27% of the total variation in PRU was explained by a history of diabetes mellitus, hematocrit, CYP2C19*2, and PON1 p.Q192R. Body mass index (odds ratio [OR]=1.15; 95% CI: 1.03–1.27), diabetes mellitus (OR=3.46; 95% CI: 1.05–11.43), hematocrit (OR=0.75; 95% CI: 0.65–0.87), and CYP2C19*2 (OR=4.44; 95% CI: 1.21–16.20) were the only independent predictors of HTPR.

Conclusion

Moreover, we propose a predictive model to determine PRU values as measured by VerifyNow P2Y12 assay for the Puerto Rican Hispanic population. This model has the potential to identify Hispanic patients at higher risk for adverse events on clopidogrel.

Impact of mean platelet aggregation degree on long-term clinical outcomes among patients undergoing a complex percutaneous coronary intervention

OBJECTIVE

The aim of this study was to evaluate the association between the mean platelet aggregation degree and long-term clinical outcomes in patients receiving a complex percutaneous coronary intervention (CPCI).

PATIENTS AND METHODS

We screened 2141 patients after a percutaneous coronary intervention (PCI) treated with aspirin and clopidogrel. CPCI was defined as a procedure targeted to at least one of the following: left main disease, bifurcation lesion, ostial lesion, chronic total occlusion, and small-vessel stenting. ADP-induced platelet aggregation was serially measured by light transmission aggregometry at least three times after PCI and the mean value was calculated. The population was categorized on the basis of the mean ADP degree and the presence of CPCI. The primary endpoint measured was a major adverse cardiovascular and cerebral event (MACCE).

RESULTS

A total of 1245 patients enrolled in the study were divided into four groups: group A (CPCI and ADP≥40%), group B (CPCI and ADP<40%), group C (non-CPCI and ADP≥40%), and group D (non-CPCI and ADP<40%). The median follow-up was 29.9 months. The Cox multivariate analysis suggested that group A was an independent risk factor for MACCE (hazard ratio: 2.70, 95% confidence interval: 1.25-5.81; P<0.001). Compared with group A, the remaining groups (groups B, C, and D) had a lower rate of MACCE. When group C was set as the reference, groups B and D had similar risks for primary endpoints.

CONCLUSION

Patients undergoing CPCI with a high mean ADP degree are at a high risk for MACCE. Serial platelet function testing is therefore important in patients receiving CPCI.

Acute myocardial infarction occurring while on chronic clopidogrel therapy ('clopidogrel failure') is associated with high incidence of clopidogrel poor responsiveness and stent thrombosis

Objectives

The clinical significance of the laboratory-based phenomenon of clopidogrel hypo-responsiveness and platelet reactivity associated with acute myocardial infarction, despite chronic clopidogrel therapy, is largely unknown. We aimed to determine platelet reactivity and clinical and angiographic features in 29 consecutive patients sustaining an acute myocardial infarction despite chronic (≥1 month) clopidogrel therapy.

Methods

Platelet reactivity was determined on admission using conventional aggregometry. All patients underwent coronary angiography within 24 hours of admission. Patients were matched with clopidogrel-naïve acute myocardial infarction patients. Clopidogrel-naïve patients received a 600 mg clopidogrel loading dose and 75 mg/day thereafter.

Results

Of the 29 study patients, 19 (66%) presented with ST-elevation myocardial infarction, and in 25% the infarction was related to angiographically-proved definite stent thrombosis. Two-thirds of these patients were poor responders to clopidogrel (adenosine diphosphate-induced platelet aggregation >50%) and dual antiplatelet poor responsiveness was found in 57% in the chronic clopidogrel therapy group. Compared with clopidogrel-naïve patients, chronic clopidogrel therapy patients were more likely to demonstrate clopidogrel poor responsiveness (66% versus 38%, p = 0.02), to be diabetic (52% versus 33%, p = 0.1) and to have multi-vessel coronary disease (79% versus 55%, p = 0.03).

Conclusions

Patients sustaining acute coronary syndrome despite chronic clopidogrel therapy are more likely to exhibit inadequate platelet inhibition with clopidogrel.

Assessment of a flow cytometry technique for studying signaling pathways in platelets: Monitoring of VASP phosphorylation in clinical samples

A recently released kit (PerFix EXPOSE) was reported to improve the measurement of the degree of phosphorylation of proteins in leukocytes by flow cytometry. We tested its adaptation for platelets to monitor vasodilator-stimulated phosphoprotein (VASP) phosphorylation, which is the basis of a currently used test for the assessment of the pharmacological response to P2Y12 antagonists (PLT VASP/P2Y12). The PerFix EXPOSE kit was compared to the PLT VASP/P2Y12 kit by using blood samples drawn at 24 h post clopidogrel dose from 19 patients hospitalized for a non-cardio-embolic ischemic stroke and treated with clopidogrel monotherapy for at least five days in an observational study. The platelet PerFix method was based on adaptation of the volume of the sample, the centrifugation speed and the incubation temperature. Poor agreement between prevention by adenosine diphosphate (ADP) of PGE₁-induced cAMP-mediated VASP phosphorylation and ADP induced aggregation assessed by Light Transmittance Aggregometry was found. We found a significant correlation between the PLT VASP/P2Y12 kit and the PerFix EXPOSE kit. The PerFix EXPOSE kit may also be helpful to monitor adverse effects of second-generation tyrosine kinase inhibitors on platelets.

A synergic effect between CYP2C19*2, CYP2C19*3 loss-of-function and CYP2C19*17 gain-of-function alleles is associated with Clopidogrel resistance among Moroccan Acute Coronary Syndromes patients

Objective

The main objective of our study was to investigate the association of CYP2C19*2 and CYP2C19*3 loss-of-function and CYP2C19*17 gain-of-function variants of CYP2C19 gene with Clopidogrel resistance in a sample of Moroccan Acute Coronary Syndromes patients.

Results

Our results showed the existence of a synergic effect between the three alleles, statistically very significant, on Clopidogrel resistance among the treated patients (P = 0.0033). For the three variants of the CYP2C19 gene, the heterozygous and homozygous mutant genotypes were the most frequent among ACS patients (CYP2C19*2: 82.76% GA and 10.35% AA; CYP2C19*3: 76.67% GA and 18.33% AA; CYP2C19*17: 66.67% CT and 18.66% TT). Allelic frequencies were 51.73% vs 48.27% (P < 0.001); 56.67% vs 43.33% (P < 0.001); and 52% vs 48% (P = 0.01) for the mutant and wild type alleles of the CYP2C19*2, CYP2C19*3 and CYP2C19*17 variants respectively. Our results support a role of CYP2C19 gene variants as a potential marker of Clopidogrel response. Understanding the functional and clinical consequences of these variants may help for treating patients more effectively, they could be genetically screened and appropriate dose adjustments could be made on the basis of their CYP2C19 genotype.

Electronic supplementary material

The online version of this article (10.1186/s13104-018-3132-0) contains supplementary material, which is available to authorized users.

CYP2C19 genotype and adverse cardiovascular outcomes after stent implantation in clopidogrel-treated Asian populations: A systematic review and meta-analysis

The effect of CYP2C19 gene polymorphism on clinical outcomes of patients with coronary artery disease (CAD) treated with clopidogrel remains controversial. Ethnicity has been proposed to influence clopidogrel response following stent implantation in CAD patients with different CYP2C19 genotypes. Furthermore, Asian populations are reported to have a relatively greater prevalence of CYP2C19 loss-of-function (LOF) alleles. We aimed to evaluate the impact of CYP2C19 gene polymorphism on clinical outcomes in Asian populations who underwent percutaneous coronary interventions (PCI) and received clopidogrel therapy. We conducted a comprehensive search in PubMed, EMBASE, and Cochrane Library from their inceptions to January 20, 2017. Studies that reported clopidogrel therapy information, clinically relevant outcomes (adverse cardiovascular events, stent thrombosis and bleeding), and CYP2C19 genotypes among Asian populations were included. The primary endpoint was major adverse cardiovascular events (MACE), defined as a composite of cardiovascular death and myocardial infarction. The safety endpoint was any kind of bleeding. We retrieved 20 studies of 15056 patients reporting 1301 cardiovascular events. The primary analysis showed at least one CYP2C19 LOF allele (*2 and/or *3) carriers were at an increased risk of MACE compared with non-carriers (10.58% vs. 6.07%, OR: 1.99, 95% CI: 1.64 to 2.42, p < .001). Stent thrombosis (ST) was also more frequent in LOF allele carriers (2.22% vs. 0.44%, OR: 4.77, 95% CI: 2.84 to 8.01, p < .001). Inversely, the risk of bleeding was lower in LOF allele carriers (OR: 0.66, 95% CI: 0.46 to 0.96, p < .001). Subgroup analysis was performed to assess differences by high (600 mg) or routine (300 mg) loading dose of clopidogrel and by different nationalities. The risk of MACE in LOF allele carriers remained significantly higher even in high loading dose group (high loading dose: OR 1.72, 95% CI: 1.37 to 2.16, and routine loading dose: OR 2.22, 95% CI: 1.68 to 2.94, p for subgroup heterogeneity = 0.16). Subgroup analysis between three nationalities of China, Korea, and Japan demonstrated that the risk of MACE among Chinese LOF allele carriers was the greatest (OR: 2.28; 95% CI:1.91 to 2.73). In conclusion, among Asian populations with CAD undergoing stent implantation, CYP2C19 LOF allele carriers are at greater risk of adverse cardiovascular events and lower risk of bleeding compared with non-carriers. Genetic testing may be helpful for clinicians to personalize antiplatelet therapy especially in Asian population.

Influence of genetic co-factors on the population pharmacokinetic model for clopidogrel and its active thiol metabolite

PURPOSE

A high interindividual variability is observed in the pharmacokinetics of clopidogrel, a widely used antiplatelet drug. In the present study, a joint parent-metabolite population pharmacokinetic model was developed to adequately describe observed concentrations of clopidogrel and its active thiol metabolite (H4).

METHODS

The study included 63 patients undergoing elective coronarography or percutaneous coronary intervention. The population pharmacokinetic model was developed in the NONMEM 7.3 software, and first-order conditional estimation method with interaction was applied. Also, the influence of covariates was evaluated (age, weight, body mass index (BMI), obesity defined as BMI ≥ 30 kg/m2, sex, diabetes mellitus, co-administration of PPI or statins, presence of CYP2C19*2, CYP2C19*17, CYP3A4*1G alleles, and ABCB1 3435 TT genotype).

RESULTS

It was found that the only significant covariate was the presence of CYP2C19*2 allele, which had an impact on lower conversion of clopidogrel to H4. As a result, predicted area under the time-concentration curve values was lower in carriers of this allele, with median 5.94 ng h/ml (interquartile range 3.92-12.51 [ng∙h/ml]) vs. 12.70 ng h/ml in non-carriers (interquartile range, 7.00-19.39 [ng∙h/ml]), respectively (p = 0.004).

CONCLUSIONS

Developed model predicts that the only significant covariate influencing the observed concentrations and therefore the exposure to the active H4 metabolite is the presence of CYP2C19*2 allele.

Prediction of high on-treatment platelet reactivity in clopidogrel-treated patients with acute coronary syndromes

BACKGROUND

About 40% of clopidogrel-treated patients display high platelet reactivity (HPR). Alternative treatments of HPR patients, identified by platelet function tests, failed to improve their clinical outcomes in large randomized clinical trials. A more appealing alternative would be to identify HPR patients a priori, based on the presence/absence of demographic, clinical and genetic factors that affect PR. Due to the complexity and multiplicity of these factors, traditional statistical methods (TSMs) fail to identify a priori HPR patients accurately. The objective was to test whether Artificial Neural Networks (ANNs) or other Machine Learning Systems (MLSs), which use algorithms to extract model-like 'structure' information from a given set of data, accurately predict platelet reactivity (PR) in clopidogrel-treated patients.

METHODS

A complete set of fifty-nine demographic, clinical, genetic data was available of 603 patients with acute coronary syndromes enrolled in the prospective GEPRESS study, which showed that HPR after 1month of clopidogrel treatment independently predicted adverse cardiovascular events in patients with Syntax Score >14. Data were analysed by MLSs and TSMs. ANNs identified more variables associated PR at 1month, compared to TSMs.

RESULTS

ANNs overall accuracy in predicting PR, although superior to other MLSs was 63% (95% CI 59-66). PR phenotype changed in both directions in 35% of patients across the 3 time points tested (before PCI, at hospital discharge and at 1month).

CONCLUSIONS

Despite their ability to analyse very complex non-linear phenomena, ANNs or MLS were unable to predict PR accurately, likely because PR is a highly unstable phenotype.

Clinical determinants of clopidogrel responsiveness in a heterogeneous cohort of Puerto Rican Hispanics

BACKGROUND

Clopidogrel is by far the most prescribed platelet adenosine diphosphate (ADP) antagonist in Puerto Rico despite the advent of newer agents (prasugrel and ticagrelor). Given the paucity of data on clopidogrel responsiveness in Hispanics, we sought to determine the association between clinical characteristics and platelet reactivity in Puerto Rican patients on clopidogrel therapy.

STUDY POPULATION

A total of 100 Puerto Rican patients on clopidogrel therapy were enrolled and allocated into two groups: Group I, without high on-treatment platelet reactivity (HTPR); and Group II, with HTPR. Platelet function was measured ex vivo using the VerifyNow® P2Y12 assay.

RESULTS

The cohort was comprised of Hispanic patients with coronary artery disease (57%), peripheral artery disease (32%), carotid artery stenosis (7%), cerebral artery aneurysm (2%), and stroke (2%). Mean platelet reactivity was 200 ± 61 P2Y12 reaction units (PRUs) (range: 8-324), and 35% of patients had HTPR (PRUs ⩾ 230). Multivariable logistic regression analysis determined that diabetes mellitus (DM) [odds ratio (OR) = 3.27; 95% confidence interval (CI): 1.20-8.96], use of proton-pump inhibitors (PPIs) (OR = 3.60; 95% CI: 1.09-11.82), and calcium channel blockers (CCBs) (OR = 3.10; 95% CI: 1.09-8.83) were independent predictors of HTPR ( p < 0.05) after adjusting for other clinical variables.

CONCLUSIONS

In a sample of 100 Puerto Rican Hispanic patients on clopidogrel, 35% had HTPR. Furthermore, DM, PPIs and CCBs predicted HTPR. Clinical outcome data are needed to identify appropriate PRU thresholds for risk prediction in the Puerto Rican population.

Duration of dual anti-platelet therapy - State of the art after the DAPT and PEGASUS-TIMI 54 trials

Dual anti-platelet therapy is prescribed in the setting of coronary heart disease for the prevention of stent thrombosis and acute thrombotic events. The optimal duration of dual anti-platelet therapy is still under debate as numerous trials have shown non-inferiority of a strategy of early cessation of one of the agents as compared to the standard practice whereas two larger trials have demonstrated benefit of prolonging dual anti-platelet therapy.

Platelet Function Testing in Patients with Acute Ischemic Stroke: An Observational Study

BACKGROUND

The measurement of platelet reactivity in patients with stroke undergoing antiplatelet therapies is not commonly performed in clinical practice. We assessed the prevalence of therapy responsiveness in patients with stroke and further investigated differences between patients on prevention therapy at stroke onset and patients naive to antiplatelet medications. We also sought differences in responsiveness between etiological subtypes and correlations between Clopidogrel responsiveness and genetic polymorphisms.

METHODS

A total of 624 stroke patients on antiplatelet therapy were included. Two different groups were identified: "non-naive patients", and "naive patients". Platelet function was measured with multiple electrode aggregometry, and genotyping assays were used to determine CYP2C19 polymorphisms.

RESULTS

Aspirin (ASA) responsiveness was significantly more frequent in naive patients compared with non-naive patients (94.9% versus 82.6%, P < .0010). A better responsiveness to ASA compared with Clopidogrel or combination therapy was found in the entire population (P < .0010), in non-naive patients (P < .0253), and in naive patients (P < .0010). Multivariate analysis revealed a strong effect of Clopidogrel as a possible "risk factor" for unresponsiveness (odds ratio 3.652, P < .0001). No difference between etiological subgroups and no correlations between responsiveness and CYP2C19 polymorphisms were found.

CONCLUSION

In our opinion, platelet function testing could be potentially useful in monitoring the biological effect of antiplatelet agents. A substantial proportion of patients with stroke on ASA were "resistant", and the treatment with Clopidogrel was accompanied by even higher rates of unresponsiveness. Longitudinal studies are needed to assess whether aggregometry might supply individualized prognostic information and whether it can be considered a valid tool for future prevention strategies.

Use of Platelet Function Testing Before Pipeline Embolization Device Placement

Background and Purpose—

Thromboembolic complications constitute a significant source of morbidity after neurointerventional procedures. Flow diversion using the pipeline embolization device for the treatment of intracranial aneurysms necessitates the use of dual antiplatelet therapy to reduce this risk. The use of platelet function testing before pipeline embolization device placement remains controversial.

Methods—

A retrospective review of prospectively maintained databases at 3 academic institutions was performed from the years 2009 to 2016 to identify patients with intracranial aneurysms treated with pipeline embolization device placement. Clinical and radiographic data were analyzed with emphasis on thromboembolic complications and clopidogrel responsiveness.

Results—

A total of 402 patients underwent 414 pipeline embolization device procedures for the treatment of 465 intracranial aneurysms. Thromboembolic complications were encountered in 9.2% of procedures and were symptomatic in 5.6%. Clopidogrel nonresponders experienced a significantly higher rate of thromboembolic complications compared with clopidogrel responders (17.4% versus 5.6%). This risk was significantly lower in nonresponders who were switched to ticagrelor when compared with patients who remained on clopidogrel (2.7% versus 24.4%). In patients who remained on clopidogrel, the rate of thromboembolic complications was significantly lower in those who received a clopidogrel boost within 24 hours pre-procedure when compared with those who did not (9.8% versus 51.9%). There was no significant difference in the rate of hemorrhagic complications between groups.

Conclusions—

Clopidogrel nonresponders experienced a significantly higher rate of thromboembolic complications when compared with clopidogrel responders. However, this risk seems to be mitigated in nonresponders who were switched to ticagrelor or received a clopidogrel boost within 24 hours pre-procedure.

Platelet testing in flow diversion: a review of the evidence

OBJECTIVE

Although the use of dual antiplatelet therapy with flow diversion is recommended and commonplace, the testing of platelet inhibition is more controversial.

METHODS

The authors reviewed the medical literature to establish and describe the physiology of platelet adhesion, the pharmacology of antiplatelet medications, and the mechanisms of the available platelet function tests. Additionally, they present a review of the pertinent neurointerventional and interventional cardiology literature.

RESULTS

Competing reports in the neurointerventional literature argue for and against the use of routine platelet function testing, with adjustments to the dosage or medications based on the results. The interventional cardiology literature has also wrestled with this dilemma after percutaneous coronary interventions, with conflicting reports of the benefits of platelet function testing.

CONCLUSIONS

Despite its prevalence, the benefits of platelet function testing prior to flow diversion are unproven. This practice will likely remain controversial until the level of evidence improves through more rigorous testing and reporting.

Impact of CYP3A4*1G Allele on Clinical Pharmacokinetics and Pharmacodynamics of Clopidogrel

BACKGROUND AND OBJECTIVES

Resistance to the antiplatelet treatment with clopidogrel has both genetic and non-genetic causes. Polymorphic variants of cytochrome P450 3A4 isoenzyme involved in the bioactivation of clopidogrel might have an influence on responsiveness to the drug. The aim of this study was to evaluate the influence of CYP3A4*1G (IVS10+12G>A, rs2242480) on the pharmacokinetics and pharmacodynamics of clopidogrel.

METHODS

CYP3A4*1G polymorphism was determined in a group of 82 patients undergoing percutaneous coronary intervention and taking 75 mg of clopidogrel daily. Concentrations of clopidogrel and its metabolites, inactive carboxylic acid derivative and two diastereoisomers of active thiol metabolite: H3 and H4, were determined by a validated HPLC-MS/MS method. Pharmacodynamic effect was measured by an impedance method with a Multiplate analyzer. Moreover, an effect of factors, such as CYP2C19 phenotype, age, gender, body mass index and interactions with drugs metabolized by CYP3A4 were also investigated.

RESULTS

In the studied group allele frequencies were: wt-0.921, *1G-0.079. Pharmacokinetic parameters of clopidogrel and its metabolites were not significantly different in carriers of *1G allele, comparing to wt/wt homozygotes. Platelet aggregation was higher in heterozygotes than in wt/wt carriers; however, the difference was not statistically significant (p = 0.484). In a multivariate analysis, which included age, body mass index, co-morbidities and coadministered drugs, CYP3A4*1G was not a predictor of values of H3 and H4 pharmacokinetic parameters and platelet aggregation.

CONCLUSION

CYP3A4*1G might not be a significant contributor to the variability in pharmacokinetic and pharmacodynamic response to clopidogrel therapy.

Platelet Function Tests: Preanalytical Variables, Clinical Utility, Advantages, and Disadvantages

Platelet function tests are mainly used in the diagnostic work-up of platelet disorders. During the last decade, the additional use of platelet function tests to evaluate the effect of antiplatelet therapy has also emerged in an attempt to identify patients with an increased risk of arterial thrombosis. Furthermore, platelet function tests are increasingly used to measure residual effect of antiplatelet therapy prior to surgery with the aim of reducing the risk of bleeding. To a limited extend, platelet function tests are also used to evaluate hyperaggregability as a potential marker of a prothrombotic state outside the setting of antiplatelet therapy. This multifaceted use of platelet function tests and the development of simpler point-of-care tests with narrower application have increased the use of platelet function testing and also facilitated the use of platelet function tests outside the highly specialized laboratories. The present chapter describes the preanalytical variables, which should be taken into account when planning platelet function testing. Also, the most widely used platelet function tests are introduced, and their clinical utility and their relative advantages and disadvantages are discussed.

Landscape of warfarin and clopidogrel pharmacogenetic variants in Qatari population from whole exome datasets

AIM

Pharmacogenetic landscapes of commonly used antiplatelet drugs, warfarin and clopidogrel have been studied in-depth in many countries. However, there is a paucity of data to understand their patterns in the Arab populations.

MATERIALS & METHODS

We analyzed the whole exome sequencing datasets of 100 Qatar individuals available in public domain with this perspective.

RESULTS

We characterized the allelic distribution of variants routinely tested for warfarin and clopidogrel. We additionally evaluated the population stratification and its effect on allele frequency distribution. Our analysis points to ethnic differences in the frequency distribution even for the small population studied.

CONCLUSION

This is one of the first and most comprehensive pharmacogenetic maps of variants associated with warfarin and clopidogrel for an Arab population, which can help tailor the drug dosage to the population.

The Impact of CYP2C19 Loss-of-Function Polymorphisms, Clinical, and Demographic Variables on Platelet Response to Clopidogrel Evaluated Using Impedance Aggregometry

INTRODUCTION

Clopidogrel is an antiplatelet drug widely used in patients with acute coronary syndromes or stroke. Despite adequate antiplatelet therapy, some patients develop acute ischemic events. This is partly attributed to the fact that they have poor inhibition of platelet reactivity, despite treatment. This study aimed to assess the impact of clinical and demographic variables and of cytochrome P450 2C19 (CYP2C19) loss-of-function polymorphisms on platelet response to clopidogrel evaluated using impedance aggregometry in an East European population.

METHODS

The study included 189 clopidogrel-treated patients with acute coronary syndromes and noncardiogenic ischemic stroke. Platelet aggregation was evaluated by impedance aggregometry. CYP2C19 loss-of-function polymorphisms were detected using the polymerase chain reaction restriction fragment length polymorphism technique. Various clinical and demographic data were also recorded.

RESULTS

In our data set, 81% of the patients were responders and 19% nonresponders to clopidogrel therapy. The distribution of CYP2C19 polymorphisms was as follows: 61.1% of patients were CYP2C19 wild-type homozygotes, 27.7% of patients were CYP2C19*2 heterozygotes, 1.1% of patients were CYP2C19*3 heterozygotes, and 10% of patients were CYP2C19*2 homozygotes. The highest level of association with clopidogrel response status was found for CYP2C19 polymorphisms, concomitant aspirin treatment, leukocyte and platelet count, history of myocardial infarction, arterial hypertension, and ward where patients were admitted.

CONCLUSION

The prevalence of clopidogrel resistance in our East European population was in line with that reported for Western populations. Clopidogrel response was significantly influenced by the presence of CYP2C19 polymorphisms. Interestingly, the concomitant use of aspirin had a significant impact on platelet response to clopidogrel, indicating a synergic interaction between these drugs.