P2Y12 Receptor Antagonist Research Articles

A Review of the Role of the Antiplatelet Drug Ticagrelor in the Management of Acute Coronary Syndrome, Acute Thrombotic Disease, and Other Diseases.

P2Y12 inhibitors, including aspirin, are key components of dual-antiplatelet therapy (DAPT), which is the optimal therapeutic strategy for preventing arterial thrombosis in patients with acute coronary syndromes (ACS) who underwent stent implantation. Ticagrelor is a cyclopentyl-triazole pyrimidine antiplatelet drug that was the first reversible oral P2Y12 receptor antagonist. Compared with clopidogrel, ticagrelor exerts a faster onset and offset of function by reversible and selective inhibition of platelet aggregation in ACS patients, including those with coronary artery blood revascularization. Despite improvement in stent materials, stent thrombosis (ST) due to high on-treatment platelet reactivity (HPR) to clopidogrel continues to occur. In addition to antiplatelet aggregation, ticagrelor displays pleiotropic cardioprotective effects, including improving coronary blood flow, reducing myocardial necrosis after an ischemic event, and anti-inflammatory effects. The benefits of ticagrelor over clopidogrel were consistent in the PLATO results, with lower incidence of the primary endpoint. Also, in 2020, the findings from the phase 3 THALES trial (NCT03354429) showed that aspirin combined with 90 mg of ticagrelor significantly reduced the rates of stroke and death compared with aspirin alone in patients with AIS or TIA. Here, we review recent research on the superiority of ticagrelor over clopidogrel, discuss the pharmacological mechanism, and present future perspectives. This review aims to present the roles of ticagrelor in the management of acute coronary syndrome, acute thrombotic disease, and other diseases.

Does thromboelastography predict bleeding in patients treated with clopidogrel or ticagrelor in off-pump coronary artery bypass grafting?

ObjectivesWe sought to investigate the predictive value of platelet function assessment for bleeding in clopidogrel- or ticagrelor-treated patients undergoing off-pump coronary artery bypass grafting (OPCABG). MethodsThis prospective study included patients treated with acetylsalicylic acid and clopidogrel or acetylsalicylic acid and ticagrelor and scheduled for OPCABG. The percentage of platelet aggregation was evaluated by thromboelastography. Postoperative blood loss was measured as the chest tube drainage (CTD) and excessive blood loss was settled as CTD with more than 600 mL at first postoperative 12 h. Major bleeding complications were defined by Bleeding Academic Research Consortium (BARC) type 4-CABG related bleeding or class 3 or class 4 bleeding in universal definition of perioperative bleeding (UDPB) in adult cardiac surgery. ResultsA total of 434 consecutive patients were included. There was a negative correlation (r = −0.133, P = 0.0056) between ADP-induced platelet aggregation and CTD at 12 h. The platelet aggregation exhibited a moderate performance (AUC = 0.616) for predicting excessive postoperative blood loss. Multivariable analysis showed that ADP-induced platelet aggregation <33.45% (OR = 2.976, 95% CI: 1.325–6.711, P = 0.008) was independently associated with excessive postoperative blood loss. However, the percentage of ADP-induced platelet aggregation predicted neither UDPB-defined nor BARC-defined major bleeding. Instead, P2Y12 receptor antagonist discontinuation time was independently related to the risk of major bleeding complication. ConclusionsADP-induced platelet aggregation detected by thromboelastography was negatively related to postoperative blood loss and platelet aggregation <33.45% was associated with excessive postoperative blood loss. However, platelet function assessment by thromboelastography failed to predict major bleeding complications.

Discovery of P2Y2 Receptor Antagonist Scaffolds through Virtual High-Throughput Screening.

The human ATP- and UTP-activated P2Y2 receptor (P2Y2R) is a Gq protein-coupled receptor involved in several pathophysiological conditions including acute and chronic inflammation, cancer, and pain. Despite its potential as a novel drug target, only few P2Y2R antagonists have been developed so far, all of which suffer from severe drawbacks. These include (i) high polarity due to one or several negative charges resulting in low oral bioavailability, (ii) metabolic instability and generally poor pharmacokinetic properties, and/or (iii) lack of selectivity, which limits their utility for in vitro and in vivo studies aimed at target validation. In search of new druglike scaffolds for P2Y2R antagonists, we employed a structure-based virtual high-throughput screening approach utilizing the complex of a P2Y2R homology model with one of the most potent and selective orthosteric antagonists described so far, AR-C118925 (10). After virtual screening of 3.2 million molecules, 58 compounds were purchased and pharmacologically evaluated. Several novel antagonist scaffolds were discovered, and their binding modes at the human P2Y2R were analyzed by molecular docking studies. The investigated antagonists likely share a similar binding mode with 10 which includes accommodation of bulky, lipophilic groups in the putative orthosteric binding site of the P2Y2R. The discovered scaffolds and the elucidated structure-activity relationships provide a basis for the development of future drug candidates for the P2Y2R which have great potential as novel drugs.

Validation of the BEST-J score, a prediction model for bleeding after endoscopic submucosal dissection for early gastric cancer: a multicenter retrospective observational study.

A new scoring system, the BEST-J score, using ten risk factors to assign cases to different post-endoscopic submucosal dissection (ESD) risk groups for bleeding, has been shown to be accurate for risk stratification. We first aimed to validate the BEST-J score at four hospitals not specialized in performing ESD and then aimed to identify other risk factors for post-ESD bleeding. We evaluated the incidence of post-ESD bleeding in 791 cases of early gastric cancer (EGC) between October 2013 and December 2020 as a retrospective, multi-center observational study conducted at four hospitals. Multivariate logistic regression models to examine the effect of independent variables on post-ESD bleeding firstly included ten possible factors raised by the BEST-J score and secondly included statistically significant (p &lt; 0.01) in univariate analysis. The prediction accuracy of the model was evaluated by receiver-operating characteristic analysis and the areas under the curve (AUC). The incidence of post-ESD bleeding was 4.8% (38/791, 95% confidence interval [CI] 3.4-6.5%). On multivariate analysis, the risk factors were P2Y12 receptor antagonist (odds ratio [OR]: 5.870, 95% CI 1.624-21.219), warfarin (8.382, 1.658-42.322), direct oral anticoagulant (DOAC) (8.980, 1.603-50.322), and tumor location in lower third of stomach (2.151, 1.012-4.571), respectively. When we categorized cases into low-risk by BEST-J score, intermediate-risk, high-risk, and very high-risk groups, the bleeding rates were 2.8%, 7.3%, 12.8%, and 19.0%, respectively. The AUC for our cohort was 0.713 (95% CI 0.625-0.802) for the BEST-J score. In the multivariate analysis in our cohort, the risks were age, body mass index, P2Y12 receptor antagonist, warfarin, DOAC, respectively. The BEST-J score is equally accurate in risk stratification of patients with EGC for post-ESD bleeding at non-specialized facilities for ESD as in specialized hospitals. BMI and age may be helpful additional risk factors at hospitals not specialized.

TREM2 regulates purinergic receptor-mediated calcium signaling and motility in human iPSC-derived microglia.

The membrane protein TREM2 (Triggering Receptor Expressed on Myeloid cells 2) regulates key microglial functions including phagocytosis and chemotaxis. Loss-of-function variants of TREM2 are associated with increased risk of Alzheimer's disease (AD). Because abnormalities in Ca2+ signaling have been observed in several AD models, we investigated TREM2 regulation of Ca2+ signaling in human induced pluripotent stem cell-derived microglia (iPSC-microglia) with genetic deletion of TREM2. We found that iPSC-microglia lacking TREM2 (TREM2 KO) show exaggerated Ca2+ signals in response to purinergic agonists, such as ADP, that shape microglial injury responses. This ADP hypersensitivity, driven by increased expression of P2Y12 and P2Y13 receptors, results in greater release of Ca2+ from the endoplasmic reticulum stores, which triggers sustained Ca2+ influx through Orai channels and alters cell motility in TREM2 KO microglia. Using iPSC-microglia expressing the genetically encoded Ca2+ probe, Salsa6f, we found that cytosolic Ca2+ tunes motility to a greater extent in TREM2 KO microglia. Despite showing greater overall displacement, TREM2 KO microglia exhibit reduced directional chemotaxis along ADP gradients. Accordingly, the chemotactic defect in TREM2 KO microglia was rescued by reducing cytosolic Ca2+ using a P2Y12 receptor antagonist. Our results show that loss of TREM2 confers a defect in microglial Ca2+ response to purinergic signals, suggesting a window of Ca2+ signaling for optimal microglial motility.

Involvement of purinergic P2Y1R in antidepressant-like effects of electroacupuncture treatment on social isolation stress mice.

Depression is a common neuropsychiatric disorder with high incidence and disability. Electroacupuncture (EA) is effective in the treatment of depression. However, the underlying mechanisms are not fully understood. Social isolation stress during post-weaning period can impair purinergic signaling in the brain of rodents and has emerged as a major risk factor for depression. The purpose of this study was to investigate the involvement of P2Y1 receptor (P2Y1R) in the antidepressant-like effects of EA. In this study, C57BL/6 mice were randomly assigned to group-housed (GH) or social isolated (SI) groups at post-natal day 21. After 6weeks of social isolation, EA was performed on acupoints "Bai-hui" (GV20) and "Yin-tang" (GV29), or non-acupoints for 4weeks. The SI mice received either intracerebroventricular injection of a selective P2Y1R agonist, MRS2365 (1nmol); or a selective P2Y1R antagonist, MRS2179 (2μmol), before and after EA. We found that SI mice exhibited depression-like behaviors accompanied with anxiety-like behaviors. The expressions of P2Y1R were well co-localized with GFAP-positive astrocytes and increased in the prefrontal cortex and hippocampus of SI mice. After treated with MRS2179, the depression-like behaviors of SI mice were attenuated, but not with MRS2365. Meanwhile, we found that EA could attenuate social isolation caused depression- and anxiety-like behaviors, and inhibited the up-regulation of P2Y1R in the prefrontal cortex and hippocampus of SI mice. Notably, the positive effects of EA on depression-like behaviors of SI mice could be reversed by MRS2365, while MRS2365 had no effect on the anxiolytic-like effects of EA. Therefore, we provide new evidence that EA could ameliorate depression- and anxiety-like behaviors in social isolation stress mice, and P2Y1R was involved in the antidepressant-like effects of EA.

A comparison of different regression models for the quantitative analysis of the combined effect of P2Y12 and P2Y1 receptor antagonists on ADP-induced platelet activation

IntroductionThe combination index (CI), a common quantitative indicator of the degree of synergy/antagonism, may be determined using different regression methods. However, any analysis with constraints has the potential for underestimating the combined effect of multiple drugs. ObjectivesThis in vitro study describes the combined effects of selected platelet antagonists on ADP-induced platelet activation in different regression models. MethodsThe inhibitory effects of P2Y12 receptor antagonists in combination with P2Y1 receptor antagonists (i.e. cangrelor with MRS 2279, prasugrel metabolite with MRS 2179 and PSB 0739 with MRS 2179) were characterized with the aid of three software packages: CompuSyn (for linear regression with constraints), CISNE (for non-linear regression with constraints) and GraphPad Prism (for non-linear regression without constraints). The synergism between P2Y12 and P2Y1 inhibitors was quantified by CI and synergy area. ResultsMRS 2279 and MRS 2179 were found to act synergistically with selected P2Y12 receptor antagonists to potentiate their antiplatelet effect. The models of regression with constraints, linear regression in particular, demonstrated a worse fit for experimental data than non-linear regression without constraints; this resulted in an incorrect estimation of the combined effects of two antiplatelet drugs, i.e., underestimating the CI and overestimating the synergy area. Also, the synergy area was found to better reflect the differences among models than the CI. ConclusionsThese findings suggest that non-linear regression without constraints offers more precise quantitative determination of combined effects between two drugs compared to the regression models with constraints.

Antiplatelet Therapy for Atherothrombotic Disease in 2022-From Population to Patient-Centered Approaches.

Antiplatelet agents, with aspirin and P2Y12 receptor antagonists as major key molecules, are currently the cornerstone of pharmacological treatment of atherothrombotic events including a variety of cardio- and cerebro-vascular as well as peripheral artery diseases. Over the last decades, significant changes have been made to antiplatelet therapeutic and prophylactic strategies. The shift from a population-based approach to patient-centered precision medicine requires greater awareness of individual risks and benefits associated with the different antiplatelet strategies, so that the right patient gets the right therapy at the right time. In this review, we present the currently available antiplatelet agents, outline different management strategies, particularly in case of bleeding or in perioperative setting, and develop the concept of high on-treatment platelet reactivity and the steps toward person-centered precision medicine aiming to optimize patient care.

Antithrombotic therapy in acute coronary syndromes setting: new clinical guidelines, controversial issues and the role of prehospital stage

Antithrombotic therapy is a cornerstone of acute coronary syndromes treatment, preventing coronary artery thrombosis development and progression. Early administration of P2Y12 receptor antagonists to patients with acute coronary syndromes (ACS) at the prehospital stage is a common practice and has been supported by the European and Russian Societies of Cardiology guidelines for many years despite the lack of definite evidence for its benefit. Recent clinical trials and registers on ACS treatment have shown no benefit and higher prevalence of bleeding related to the early start of P2Y12 receptor antagonists in NSTE-ACS patients. The latest European and Russian Societies of Cardiology guidelines do not recommend prehospital administration of P2Y12 receptor antagonists. The article highlights the antithrombotic therapy in acute coronary syndromes setting, recent ESC guidelines and its possible implementation in common practice.

Mechanical ventilation induces lung and brain injury through ATP production, P2Y1 receptor activation and dopamine release

ABSTRACT Mechanical ventilation can induce lung injury and exacerbate brain injury due to lung-brain interaction. The current study sought to investigate the mechanism of lung-brain interaction induced by mechanical ventilation and offer theoretical insight into the management of ventilator-induced brain injury. The experimental mice were assigned into the spontaneously breathing group and the mechanical ventilation group and injected with dopamine (DA) receptor antagonist haloperidol or P2Y1 receptor antagonist MRS2279 before ventilation. In vitro assay was conducted using lung epithelial cells MLE-12 hippocampal neuron cells and HT-22. Mouse recognition function and lung injury were examined. The condition and concentration of neurons in the hippocampus were observed. The levels of several inflammatory factors, DA, adenosine triphosphate (ATP), P2Y1R, and dysbindin-1 were detected. Mechanical ventilation induced lung and brain injury in mice, manifested in increased inflammatory factors in the bronchoalveolar lavage fluid and hippocampus, prolonged escape latency, and swimming distance and time in the target quadrant with a weakened concentration of neurons in the hippocampus. Our results presented elevated ATP and P2Y1R expressions in the mechanically ventilated mice and stretched MLE-12 cells. The mechanically ventilated mice and P2Y1 receptor activator MRS2365-treated HT-22 cells presented with elevated levels of DA and dysbindin-1. Inactivation of P2Y1 receptor in the hippocampus or blockage of DA receptor alleviated brain injury induced by mechanical ventilation in mice. To conclude, the current study elicited that lung injury induced by mechanical ventilation exacerbated brain injury in mice by increasing ATP production, activating the P2Y1 receptor, and thus promoting DA release.

Cangrelor in STEMI as a bridge to CABG- a mini-case series

BackgroundPatients with STEMI receive dual antiplatelet therapy as soon as possible with aspirin and a P2Y12 receptor antagonist prior to PCI. A fraction of these patients may have multi-vessel disease needing emergent CABG surgery. The choice of a P2Y12 receptor antagonist plays a role in the timing of CABG surgery as it poses a bleeding risk until it is completely eliminated from the system. Oral P2Y12 receptor antagonists have a long duration of platelet inhibition which is difficult to reverse. Cangrelor is an intravenous P2Y12 receptor antagonist with a short half-life and rapid cessation of its effect after discontinuation. MethodsThree patients who presented to our emergency department with STEMI were started on cangrelor infusion prior to cardiac catheterization instead of other P2Y12 receptor antagonists like clopidogrel or ticagrelor. The study received ethical approval as it is part of the current standard of care for STEMI patients. ResultsAll three patients were found to have multi-vessel disease during coronary angiography requiring CABG surgery. As cangrelor was used in these patients they were able to have their surgery within 24–48 h. Intravenous cangrelor was stopped about an hour before surgery. No bleeding complications occurred and all three patients made a speedy recovery in the ICU. ConclusionCangrelor is a potent P2Y12 receptor antagonist which can be used in patients presenting with STEMI as one of the two anti-platelet agents along with aspirin without any dilemma that it would cause a delay in CABG surgery if the patients need one.

Hemoadsorption of Rivaroxaban and Ticagrelor during Acute Type A Aortic Dissection Operations.

Objective: To analyze the results of hemoadsorption in patients with cardiac surgery to thoracic aortic surgery, who had been loaded beforehand with either Factor Xa inhibitor rivaroxaban or P2Y12 receptor antagonist ticagrelor.Methods: We investigated 21 of 171 consecutive patients (median age 71 [interquartile range 62, 76] years) who underwent emergency cardiac operations for acute type A aortic dissection between 2014 and 2020. These patients were pretreated with rivaroxaban (n = 9) or ticagrelor (n = 12). In ten of 21 cases (since 2017), we installed a hemoadsorber into the heart–lung machine and compared the results to eleven patients done without hemoadsorber before that time.Results: The operation time was significantly shorter in the adsorber group (286 ± 40 min vs. 348 ± 79 min; p = 0.045). The postoperative 24-hour drainage volume was significantly lower after adsorption (p <0.001; 482 ± 122 ml vs. 907 ± 427 ml) and no rethoracotomy had to be performed (compared to two rethoracotomies [18.9%] among patients without adsorber use). Also, patients without hemoadsorption required significantly more platelet transfusions (p = 0.049).Conclusions: In patients with acute type A aortic dissection who were pretreated with rivaroxaban and ticagrelor, the intraoperative use of CytoSorb hemoadsorption during cardiopulmonary bypass is reported for the first time. The method was found to be effective to prevent from bleeding and to improve the outcome in aortic dissection.

Pharmacological Approaches to Limit Ischemic and Reperfusion Injuries of the Heart: Analysis of Experimental and Clinical Data on P2Y12 Receptor Antagonists.

Ischemic and reperfusion injuries of the heart underlie the pathogenesis of acute myocardial infarction (AMI) and sudden cardiac death. The mortality rate is still high and is 5-7% in patients with ST-segment elevation myocardial infarction. The review is devoted to pharmacological approaches to limitation of ischemic and reperfusion injuries of the heart. The article analyzes experimental evidence and the clinical data on the effects of P2Y12 receptor antagonists on the heart's tolerance to ischemia/reperfusion in animals with coronary artery occlusion and reperfusion and also in patients with AMI. Chronic administration of ticagrelor prevented adverse remodeling of the heart. There is evidence that sphingosine-1-phosphate is the molecule that mediates the infarct-reducing effect of P2Y12 receptor antagonists. It was discussed a role of adenosine in the cardioprotective effect of ticagrelor.

Transition from Syringe to Autoinjector Based on Bridging Pharmacokinetics and Pharmacodynamics of the P2Y12 Receptor Antagonist Selatogrel in Healthy Subjects

Selatogrel is a potent, reversible, and selective antagonist of the platelet P2Y12 receptor currently developed for the treatment of acute myocardial infarction(AMI). In the completed Phase I/II studies, selatogrel was subcutaneously(s.c.) administered as a lyophilizate-based formulation by syringe by a healthcare professional. In the Phase III study, selatogrel will be self-administered s.c. as a liquid formulation with an autoinjector at the onset of AMI symptoms to shorten treatment delay. This clinical bridging study compared the pharmacokinetics(PK) of selatogrel between the different formulations. This was a single-center, randomized, open-label, three-period, cross-over Phase I study in 24 healthy subjects. In each period, a single subcutaneous dose of 16 mg selatogrel was administered as (1) a Phase III liquid formulation by autoinjector (Treatment A), (2) a Phase III liquid formulation by prefilled syringe (Treatment B), or (3) a Phase I/II reconstituted lyophilizate-based formulation by syringe (Treatment C). PK parameters including area under the plasma concentration-time curve from zero to infinity (AUC0-∞), maximum plasma concentration (Cmax), time to reach Cmax(tmax), and terminal half-life(t1/2) were determined using noncompartmental analysis. Pharmacodynamic(PD) parameters were estimated using PK/PD modeling, including the time of first occurrence of inhibition of platelet aggregation(IPA) ≥80% (tonset), duration of IPA above 80% (tduration), and responder rate defined as the percentage of subjects with tonset ≤30min and tduration ≥3h. Safety and tolerability were also assessed. Comparing Treatment A to Treatment C, the exposure (AUC0-∞) was bioequivalent with a geometric mean ratio(GMR) (90% confidence interval) of 0.95 (0.92-0.97) within the bioequivalence range (0.80-1.25). Absorption following Treatment A was slightly slower with atmax occurring approximately 30min later and a 20% lower Cmax. The autoinjector itself had no impact on the PK of selatogrel, as similar values of Cmax and AUC0-∞ were determined after administration as a Phase III liquid formulation by autoinjector or by prefilled syringe (i.e., GMR [90% confidence interval] of 1.06 [0.97-1.15] and 0.99 [0.96-1.03] for Cmax and AUC0-∞, respectively). PK/PD modeling predicted that the median tonset will occur slightly later for Treatment A (7.2min) compared to Treatment C (4.2 min), while no relevant differences in tduration and responder rate were estimated between the two treatments. Selatogrel was safe and well tolerated following all three treatments. PK and simulated PD effects of selatogrel were similar across treatments. NCT04557280.

Method article: an in vitro blood flow model to advance the study of platelet adhesion utilizing a damaged endothelium

In vitro flow assays utilizing microfluidic devices are often used to study human platelets as an alternative to the costly animal models of hemostasis and thrombosis that may not accurately represent human platelet behavior in vivo. Here, we present a tunable in vitro model to study platelet behavior in human whole blood flow that includes both an inflamed, damaged endothelium and exposed extracellular matrix. We demonstrate that the model is adaptable across various anticoagulants, shear rates, and proteins for endothelial cell culture without the need for a complicated, custom-designed device. Furthermore, we verified the ability of this ‘damaged endothelium’ model as a screening method for potential anti-platelet or anti-thrombotic compounds using a P2Y12 receptor antagonist (ticagrelor), a pan-selectin inhibitor (Bimosiamose), and a histamine receptor antagonist (Cimetidine). These compounds significantly decreased platelet adhesion to the damaged endothelium, highlighting that this model can successfully screen anti-platelet compounds that target platelets directly or the endothelium indirectly.

Current and Novel Antiplatelet Therapies for the Treatment of Cardiovascular Diseases.

Over the last decades, antiplatelet agents, mainly aspirin and P2Y12 receptor antagonists, have significantly reduced morbidity and mortality associated with arterial thrombosis. Their pharmacological characteristics, including pharmacokinetic/pharmacodynamics profiles, have been extensively studied, and a significant number of clinical trials assessing their efficacy and safety in various clinical settings have established antithrombotic efficacy. Notwithstanding, antiplatelet agents carry an inherent risk of bleeding. Given that bleeding is associated with adverse cardiovascular outcomes and mortality, there is an unmet clinical need to develop novel antiplatelet therapies that inhibit thrombosis while maintaining hemostasis. In this review, we present the currently available antiplatelet agents, with a particular focus on their targets, pharmacological characteristics, and patterns of use. We will further discuss the novel antiplatelet therapies in the pipeline, with the goal of improved clinical outcomes among patients with atherothrombotic diseases.

Risk factors and prediction of bleeding after gastric endoscopic submucosal dissection in patients on antithrombotic therapy: newly developed bleeding prediction application software, SAMURAI model.

Bleeding after gastric endoscopic submucosal dissection (ESD) remains problematic, especially in patients receiving antithrombotic therapy. Therefore, this study aimed to identify the risk factors. In this retrospective study, patients (n = 1,207) who underwent gastric ESD while receiving antithrombotic therapy were enrolled at Osaka Medical and Pharmaceutical University Hospital and 18 other referral hospitals in Japan. Risks of post-ESD bleeding were calculated using multivariable logistic regression. The dataset was divided into a derivation cohort and a validation cohort. We created a prediction model using the derivation cohort. The accuracy of the model was evaluated using the validation cohort. Post-ESD bleeding occurred in 142 (11.8%) participants. Multivariable analysis yielded an odds ratio of 2.33 for aspirin, 4.90 for P2Y12 receptor antagonist, 1.79 for cilostazol, 0.95 for other antithrombotic agents, 6.53 for warfarin, 5.65 for dabigatran, 7.84 for apixaban, 10.45 for edoxaban, 6.02 for rivaroxaban, and 1.46 for heparin bridging. The created prediction model was called safe ESD management using the risk analysis of post-bleeding in patients with antithrombotic therapy (SAMURAI). This model had good predictability, with a C-statistic of 0.77. In conclusion, use of the SAMURAI model will allow proactive management of post-ESD bleeding risk in patients receiving antithrombotic therapy.

DNA Damage in AML-12 Hepatocytes and 3T3-L1 Adipocytes Treated with Clopidogrel.

Clopidogrel has been commonly prescribed as a selective P2Y12 receptor antagonist to reduce heart attack and stroke risk. Nearly 10% of absorbed clopidogrel is metabolized to active forms by cytochrome P450 (CYP) enzymes in the liver and 90% to inactive clopidogrel carboxylate by esterases. Since different forms of clopidogrel have cytotoxic potential, our aim was to determine the effect of 7.5, 40, and 75μM clopidogrel over DNA damage in adipocytes and hepatocytes. In the present study, DNA damage was investigated by Comet analysis using 3T3-L1 adipocytes and Alpha Mouse 12 (AML-12) hepatocytes. DNA fragmentation was found to be increased as a response to 7.5 μM, 40 μM, and 75 μM clopidogrel treatment compared to non-treated control groups in AML-12 hepatocytes (p<0.01, p<0.001, p<0.01 respectively) and 3T3-L1 adipocytes (p<0.001, p<0.001 and p<0.001respectively). DNA damage levels as a response to clopidogrel treatment were found to be higher in 3T3-L1 adipocytes than AML-12 hepatocytes. Also, DNA damage levels in adipocytes and hepatocytes were found to increase dose-dependently for 7.5 and 40 μM clopidogrel, whereas decreased as a response to 75 μM. According to our results, clopidogrel results in more DNA damage in adipocytes than in hepatocytes. The molecular mechanism of clopidogrel genotoxicity needs to be further investigated especially in adipose tissue.

Abstract 13919: Ticagrelor versus Clopidogrel in Patients With Acute Coronary Syndrome: A Meta-Analysis

Introduction: P2Y 12 receptor antagonists are potent antiplatelet medications used in acute coronary syndrome (ACS). As compared to clopidogrel, ticagrelor has been shown to decrease the risk of myocardial infarction, stroke, and mortality. However, ticagrelor’s effect on the microcirculation of the coronary arteries is not well defined. Methods/Results: This meta-analysis compares the index of microcirculatory resistance (IMR), coronary flow reserve (CFR), and fractional flow reserve (FFR) of ticagrelor versus clopidogrel in ACS patients immediately post-PCI. Four randomized controlled trials were included with 375 patients. IMR was significantly lower in the ticagrelor arm (mean difference (MD) -6.34, 95% confidence interval (CI) -8.60 to -4.09, p&lt;0.00001, I 2 =66%) (Figure 1). CFR was significantly higher in the ticagrelor arm (MD 0.26, 95% CI 0.04-0.47, p=0.02, I 2 =0%). Finally, FFR was determined to be similar between ticagrelor and clopidogrel. Conclusion: This meta-analysis shows that ticagrelor significantly decreases IMR and subsequently the risk of myocardial damage and microvascular injury. Ticagrelor is also associated with significantly higher values of CRF and thus a decreased plaque burden and microvascular burden. In correlation with the decreased adverse effects, ticagrelor may be more efficacious in improving microcirculation than clopidogrel immediately post-PCI in patients who present with ACS.

Novel Thienopyrimidine-Based PET Tracers for P2Y12 Receptor Imaging in the Brain.

The P2Y12 receptor (P2Y12R) is uniquely expressed on microglia in the brain, and its expression level directly depends on the microglial activation state. Therefore, P2Y12R provides a promising imaging marker for distinguishing the pro- and anti-inflammatory microglial phenotypes, both of which play crucial roles in neuroinflammatory diseases. In this study, three P2Y12R antagonists were selected from the literature, radiolabeled with carbon-11 or fluorine-18, and evaluated in healthy Wistar rats. Brain imaging was performed with and without blocking of efflux transporters P-glycoprotein and breast cancer resistance protein using tariquidar. Low brain uptake in healthy rats was observed for all tracers at baseline conditions, whereas blocking of efflux transporters resulted in a strong (6–7 fold) increase in brain uptake for both of them. Binding of the most promising tracer, [18F]3, was further evaluated by in vitro autoradiography on rat brain sections, ex vivo metabolite studies, and in vivo P2Y12R blocking studies. In vitro binding of [18F]3 on rat brain sections indicated high P2Y12R targeting with approximately 70% selective and specific binding. At 60 min post-injection, over 95% of radioactivity in the brain accounted for an intact tracer. In blood plasma, still 40% intact tracer was found, and formed metabolites did not enter the brain. A moderate P2Y12R blocking effect was observed in vivo by positron emission tomography (PET) imaging with [18F]3 (p = 0.04). To conclude, three potential P2Y12R PET tracers were obtained and analyzed for P2Y12R targeting in the brain. Unfortunately, the brain uptake appeared low. Future work will focus on the design of P2Y12R inhibitors with improved physicochemical characteristics to reduce efflux transport and increase brain penetration.