Antiplatelet Potency Research Articles

Ácido acetilsalicílico versus inibidores dos receptores P2Y12 para prevenção secundária em pacientes tratados por meio de intervenção coronária percutânea

Currently, percutaneous coronary intervention with a drug-eluting stent implantation is the main method of myocardial revascularization in tertiary care hospitals, regardless of the clinical presentation of coronary artery disease. It is well known that to be effective, it requires the use of a dual antiplatelet therapy, which is a combination of acetylsalicylic acid and a P2Y12 platelet receptor inhibitor, which plays a key role in preventing thromboses after endoprosthesis implantation and is also indicated to prevent atherothrombotic events in the late clinical course, regardless of the stent model used. After a variable period of time, depending on some factors, such as the clinical presentation of coronary artery disease and the type of stent implanted, this therapy is discontinued, and the main current guidelines recommend interrupting the P2Y12 receptor inhibitor and maintaining acetylsalicylic acid in the long term, as one of the main pharmacological measures for secondary prevention of atherosclerosis. However, recently, due to their greater antiplatelet potency and probable lower potential for significant bleeding, especially in the digestive tract, P2Y12 inhibitors have been considered a valid and attractive option as an antiplatelet agent for long-term use; but this alternative has not been endorsed by guidelines yet. This review discusses the details related to this important decision that must be made by cardiologists when discontinuing the different antithrombotic therapies initially used after percutaneous coronary intervention. In principle, the scarcity of conclusive and normative clinical studies, especially in the population treated by percutaneous intervention, means that acetylsalicylic acid is the only antiplatelet agent with class I indication for secondary prevention of atherosclerosis.

Navigating the Course of Dual Antiplatelet Therapy After Percutaneous Coronary Intervention: A Review of Guided Approaches.

Dual antiplatelet therapy (DAPT) is the standard approach to prevent thrombotic events in patients undergoing percutaneous coronary intervention and presenting with chronic or acute coronary syndromes. However, a sizeable proportion of patients presents with an impaired or unwarranted response to DAPT depending on genetic polymorphisms or variability in platelet response. Therefore, the concept of changing the type or dose of antiplatelet drugs based on the result of platelet function or genotype tests (ie, guided DAPT) has been introduced. The goal of guided DAPT is to intensify the antiplatelet potency in patients at high risk of thrombotic events (ie, escalation) and to decrease the antiplatelet potency in patients at high risk of bleeding (ie, de-escalation). This review aims to present an up-to-date and comprehensive overview of the latest research findings on DAPT modulation guided by either platelet function or genetic testing, discussing its current indications and future directions.

First-Row Transition Metal Complexes Incorporating the 2-(2'-pyridyl)quinoxaline Ligand (pqx), as Potent Inflammatory Mediators: Cytotoxic Properties and Biological Activities against the Platelet-Activating Factor (PAF) and Thrombin.

Inflammatory mediators constitute a recently coined term in the field of metal-based complexes with antiplatelet activities. Our strategy targets Platelet-Activating Factor (PAF) and its receptor, which is the most potent lipid mediator of inflammation. Thus, the antiplatelet (anti-PAF) potency of any substance could be exerted by inhibiting the PAF-induced aggregation in washed rabbit platelets (WRPs), which internationally is a well-accepted methodology. Herein, a series of mononuclear (mer-[Cr(pqx)Cl3(H2O]) (1), [Co(pqx)Cl2(DMF)] (2) (DMF = N,N'-dimethyl formamide), [Cu(pqx)Cl2(DMSO)] (3) (DMSO = dimethyl sulfoxide), [Zn(pqx)Cl2] (4)) and dinuclear complexes ([Mn(pqx)(H2O)2Cl2]2 (5), [Fe(pqx)Cl2]2 (6) and [Ni(pqx)Cl2]2 (7)) incorporating the 2-(2'-pyridyl)quinoxaline ligand (pqx), were biologically evaluated as inhibitors of the PAF- and thrombin-induced aggregation in washed rabbit platelets (WRPs). The molecular structure of the five-co-ordinate analog (3) has been elucidated by single-crystal X-ray diffraction revealing a trigonal bipyramidal geometry. All complexes are potent inhibitors of the PAF-induced aggregation in WRPs in the micromolar range. Complex (6) displayed a remarkable in vitro dual inhibition against PAF and thrombin, with IC50 values of 1.79 μM and 0.46 μM, respectively. Within the series, complex (5) was less effective (IC50 = 39 μM) while complex (1) was almost 12-fold more potent against PAF, as opposed to thrombin-induced aggregation. The biological behavior of complexes 1, 6 and 7 on PAF's basic metabolic enzymatic pathways reveals that they affect key biosynthetic and catabolic enzymes of PAF underlying the anti-inflammatory properties of the relevant complexes. The in vitro cytotoxic activities of all complexes in HEK293T (human embryonic kidney cells) and HeLa cells (cervical cancer cells) are described via the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. The results reveal that complex 3 is the most potent within the series.

Expressing Enhanced Inhibitory Effects toward Arachidonic Acid Induced Platelet Activation: Design, Synthesis, DFT Calculations and in vitro Evaluation of Imatinib Analogues

AbstractEncouraged by the excellent antiplatelet properties of novel imatinib and nilotinib analogues in our previous study and based on a fact that slight structural changes, such as the incorporation of different substituents at the final phenyl ring of imatinib and nilotinib, have a strong impact on their antiplatelet potency, two pairs of constitutional isomers of the imatinib analogues 1, 2 and 3, 4, have been designed, synthesized and evaluated for their antiplatelet characteristics. The structure geometry of the imatinib analogues 1–4 and NBO (Natural Bond Orbital) charges of the lower energy conformation each of the analogues were explored by DFT. Molecular docking studies were also performed. All compounds were less efficient in inhibiting platelet aggregation induced by ADP or TRAP‐6 in comparison with arachidonic acid (AA). Similar results were obtained for the membrane expression of P‐selectin. The most active compound was also tested to inhibit c‐Src kinase. The present study demonstrates that appropriate modifications of the imatinib structure, may confer on this molecule potent antiplatelet characteristics.

Fermentation Enhances the Anti-Inflammatory and Anti-Platelet Properties of Both Bovine Dairy and Plant-Derived Dairy Alternatives

Within the present study, the effects of fermentation on the anti-inflammatory and anti-platelet properties of both homemade and commercially purchased bovine dairy and almond, coconut, and rice-based dairy alternatives were evaluated. The extracted total lipids (TL) from homemade and commercially purchased fermented and unfermented bovine, almond, coconut, and rice-based products were further separated into their neutral lipids (NL) and polar lipids (PL) fractions by counter current distribution. The TL, PL, and NL of each sample were assessed in human platelets against the inflammatory and thrombotic mediator, platelet-activating factor (PAF), and the well-established platelet agonist, adenosine 5′ diphosphate (ADP). In all samples, the PL fractions showed significantly stronger inhibitory effects against human platelet aggregation induced by PAF or ADP, in comparison to the TL and NL, with higher specificity against PAF. PL of all fermented products (bovine yogurt and fermented dairy alternatives from almond, rice, and coconut), exhibited the strongest anti-inflammatory and anti-platelet potency, in comparison to PL from their initial pasteurized materials (bovine milk and rice, almond, and coconut-based dairy alternative drinks). PL of the pasteurized rice-based drink and, especially PL from the novel homemade rice-based fermented product (HMFRD), showed the strongest anti-PAF and anti-ADP potency compared to all samples, with anti-PAF activity being most potent overall. The unfermented pasteurized coconut-based drink showed the lowest anti-inflammatory and anti-platelet potency, and the bovine and almond-based fermented products showed an intermediate effect. Further lipidomics with LC-MS analysis of all these PL fractions revealed that fermentation altered their fatty acid content in a way that decreased their degree of saturation and increased the content of unsaturated fatty acids, thus providing a rationale for the stronger anti-inflammatory and anti-platelet potency of the more unsaturated PL fractions of the fermented products. This study has shown that fermentation alters the fatty acid content and the bio-functionality of the PL bioactives in both fermented bovine dairy and plant-based dairy alternatives, and subsequently improved their anti-inflammatory and anti-platelet functional properties.

Biogenic Synthesis of Antibacterial, Hemocompatible, and Antiplatelets Lysozyme Functionalized Silver Nanoparticles through the One-Step Process for Therapeutic Applications

To evaluate silver nanoparticles’ (AgNPs) therapeutic and clinical potentials, antibacterial action, blood compatibility, and antiplatelet activities are the main concerns for toxicity profiling. Heat-denatured lysozyme-mediated formulation stabilized the AgNPs, thereby providing more bactericidal activity and blood compatibility. The study of the synthesis of AgNPs suggests the rapid and cost-effective formulation of AgNPs by one-step reaction using a 10:1 ratio of silver nitrate and lysozyme by incubating at 60 °C for two hours. Characterization of AgNPs was analyzed by UV–Visible spectroscopy, DLS, TEM, EDX, XRD, AFM, and FTIR, followed by antibacterial, hemocompatibility, and platelet aggregation testing. The average size of synthesized AgNPs was found to be 94.10 nm with 0.45 mV zeta potential and 0.293 polydispersity index by DLS. The TEM and EXD results indicated homogeneously 28.08 nm spherical-shaped pure formations of AgNPs. The XRD peaks showed the synthesis of small AgNPs with a crystallite size of 22.88 nm, while the AFM confirmed the homogeneity and smoothness of the monodispersed AgNPs. The FTIR spectra specified the coating of the lysozyme-derived amide group on the AgNPs surface, which provides stability and functionality of nanoparticles. The antibacterial activity of AgNPs was remarkable against six pathogenic bacteria and three multidrug resistance (MDR) strains (i.e., Escherichia coli, Klebsiella aerogenes, and Pseudomonas aeruginosa), which exhibited inhibition zones with diameters ranging between 13.5 ± 0.2 mm to 19.0 ± 0.3 mm. The non-hemolytic nature of the AgNPs was calculated by percentage hemolysis with four concentrations. The negative result of platelet aggregation using platelet-rich plasma suggests the antiplatelet effect of AgNPs. Only minor hemolysis of 6.17% in human erythrocytes and mild platelet aggregation of 1.98% were induced, respectively, by the use of 1000 µL of 1 mM AgNPs, which contains approximately 107.8 μg silver. The results indicated that the antiplatelet potency and non-hemolytic nature with the antibacterial action of the lysozyme functionalized AgNPs have a good chance to be used to solve in-stent restenosis and thrombosis issues of the coronary stent and may also have a possibility to use in vaccination to resolve the blood clotting problem. So, the optimized biogenic formulation of AgNPs offers promising opportunities to be used as a therapeutic agent.

Anti-Platelet Properties of Apple Must/Skin Yeasts and of Their Fermented Apple Cider Products

Alcoholic beverages like apple cider are considered functional beverages with several health benefits, when consumed in moderation, which are mainly attributed to their microbiota and the plethora of their bioactive compounds. Among them, bio-functional polar lipids (PL) have recently been found in apple cider, which despite low quantities, have exhibited strong anti-inflammatory and anti-platelet properties, while fermentation seems to affect the functionality of apple cider’s PL bioactives. The aim of the present study was to elaborate yeast strains isolated from the complex mixtures of apple surface and must yeasts for evaluating their effects on the anti-platelet functional properties of PL bioactives from their final fermented apple cider products. First, bio-functional PL were extracted and separated from the biomass of the different isolated apple surface/must yeast strains, and were further assessed for their anti-platelet potency against human platelet aggregation induced by the potent inflammatory and thrombotic mediator platelet-activating factor (PAF), or by a classic platelet agonist like adenosine diphopshate (ADP). Novel functional apple ciders were then produced from the fermentation of apple juice by elaborating the most bioactive and resilient yeast strains isolated from the apple must with optimum fermentation properties. PL bioactives extracted from these novel apple cider products were also further assessed for their anti-platelet properties against both the PAF and ADP pathways of human platelet aggregation. These novel cider products were found to contain PL bioactives with lower IC50 values (~40 μg) and thus increased anti-platelet potency against platelet aggregation induced by PAF and ADP. GC-MS analysis of the PL bioactives extracted from these novel apple ciders showed that apple cider PL bioactives are rich in monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA), such as the omega-6 linoleic acid (LA) and the omega-3 alpha linolenic acid (ALA), with favorably lower levels for their omega-6/omega-3 PUFA ratio, which further support the observed strong anti-platelet properties putative anti-inflammatory potency for the apple cider PL bioactives. However, further studies are needed in order to elucidate and fully characterize the apple yeast strains that can be utilized for increasing the anti-inflammatory, anti-platelet and cardioprotective functional properties of their fermented apple cider products.

Beneficial Anti-Platelet and Anti-Inflammatory Properties of Irish Apple Juice and Cider Bioactives.

Several bioactives from fruit juices and beverages like phenolics, nucleotides and polar lipids (PL) have exhibited anti-platelet cardio-protective properties. However, apple juice and cider lipid bioactives have not been evaluated so far. The aim of this study was to investigate the anti-platelet and anti-inflammatory effects and structure activity relationships of Irish apple juice and Real Irish cider lipid bioactives against the platelet-activating factor (PAF)- and adenosine diphosphate (ADP)-related thrombotic and inflammatory manifestations in human platelets. Total Lipids (TL) were extracted from low, moderate and high in tannins apple juices and from their derived-through-fermentation cider products, as well as from commercial apple juice and cider. These were separated into neutral lipids (NL) and PL, while all lipid extracts were further assessed for their ability to inhibit aggregation of human platelets induced by PAF and ADP. In all cases, PL exhibited the strongest anti-platelet bioactivities and were further separated by high-performance liquid chromatography (HPLC) analysis into PL subclasses/fractions that were also assessed for their antiplatelet potency. The PL from low in tannins apple juice exhibited the strongest antiplatelet effects against PAF and ADP, while PL from its fermented cider product were less active. Moreover, the phosphatidylcholines (PC) in apple juices and the phosphatidylethanolamines (PE) in apple ciders were the most bioactive HPLC-derived PL subclasses against PAF-induced platelet aggregation. Structural elucidation of the fatty acid composition by gas chromatography mass spectra (GCMS) analysis showed that PL from all samples are rich in beneficial monounsaturated fatty acids (MUFA) and omega 3 (n-3) polyunsaturated fatty acids (PUFA), providing a possible explanation for their strong anti-platelet properties, while the favorable low levels of their omega-6/omega-3 (n-6/n-3) PUFA ratio, especially for the bioactive PC and PE subclasses, further support an anti-inflammatory cardio-protective potency for these apple products. In conclusion, Irish apple juice and Real Irish cider were found to possess bioactive PL compounds with strong antiplatelet and anti-inflammatory properties, while fermentation seems to be an important modulating factor on their lipid content, structures and bioactivities. However, further studies are needed to evaluate these effects.

The potency of selatogrel, a reversible antagonist of the P2Y12 receptor, is affected by calcium concentration

Here, we report the in vitro characterization of the P2Y12 receptor antagonist selatogrel (ACT-246475). Binding studies with radiolabeled selatogrel demonstrated that selatogrel is a competitive antagonist of ADP binding to the P2Y12 receptor with a fast onset of action. Consequently, selatogrel was confirmed to be a potent inhibitor of P2Y12-mediated intra-platelet signaling and ADP-induced platelet activation. Characterization of selatogrel in platelet-rich plasma in vitro demonstrated that the mode of anti-coagulation affected the anti-platelet potency. Specifically, in platelet-rich plasma containing physiological calcium concentration (anticoagulated with a direct thrombin inhibitor), selatogrel achieved half-maximal inhibition of ADP-induced platelet aggregation at a 3-fold lower concentration than in conditions with low calcium concentration (anticoagulated with citrate). Furthermore, calcium-dependent reduction in selatogrel potency was observed in whole blood platelet aggregation using the VerifyNow™ system with a 3.7-fold potency loss in low calcium conditions. A comparable potency loss was also observed with the reversible P2Y12 receptor antagonists ticagrelor, cangrelor and elinogrel. Furthermore, receptor-binding experiments using radiolabeled selatogrel confirmed a 3-fold lowering of selatogrel binding affinity to the P2Y12 receptor in low calcium conditions. In conclusion, our data suggest that in low calcium conditions (i.e., citrate-anticoagulated blood), there is a risk of underestimating the potency of reversible P2Y12 receptor antagonists. To avoid overdosing, and a potential increase in bleeding risk, we propose that the ex vivo evaluation of reversible P2Y12 receptor antagonists should be performed with platelet assay systems containing physiological calcium concentration.

Association of FMO3 rs1736557 polymorphism with clopidogrel response in Chinese patients with coronary artery disease

Dual antiplatelet therapy with aspirin and clopidogrel is commonly used for coronary artery disease (CAD) patients undergoing percutaneous coronary intervention to prevent stent thrombosis and ischemic events. However, some patients show high on-treatment platelet reactivity (HTPR) during clopidogrel therapy. Genetic factors such as loss-of-function variants of CYP2C19 are validated to increase the risk of HTPR. Flavin-containing monooxygenase 3 (FMO3) is reported to be associated with potency of platelet responsiveness and thrombosis. This study aimed to explore the association between FMO3 rs1736557 polymorphism and clopidogrel response. Five hundred twenty-two Chinese CAD patients treated with dual antiplatelet therapy were recruited from Xiangya Hospital. After oral administration of 300mg loading dose (LD) clopidogrel for 12-24h or 75mg daily maintenance dose (MD) clopidogrel for at least 5days, the platelet reaction index (PRI) was determined by vasodilator-stimulated phosphoprotein-phosphorylation assay. FMO3 rs1736557, CYP2C19*2, and CYP2C19*3 polymorphisms were genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Mean PRI value was significantly higher in CYP2C19 poor metabolizers (PMs) and intermediate metabolizers (IMs) than the extensive metabolizers (EMs) (p < 0.001). In addition, FMO3 rs1736557 AA homozygotes showed significantly lower PRI as compared with carriers of the major rs1736557 G allele in the entire cohort and in the MD cohort (p = 0.011, p = 0.008, respectively). The risk of HTPR was decreased significantly in carriers of the rs1736557 A allele (AA vs GG: OR = 0.316, 95% CI: 0.137-0.726, p = 0.005; AA vs GA: OR = 0.249, 95% CI: 0.104-0.597, p = 0.001; AA vs GG+GA: OR = 0.294, 95% CI: 0.129-0.669, p = 0.002), and the association was observed mainly in patients carrying the CYP2C19 LOF allele and in those administered with MD. The FMO3 rs1736557 AA genotype was related to an increased the antiplatelet potency of clopidogrel in Chinese CAD patients. Additional studies are required to verify this finding.

ASSOCIATION BETWEEN SMOKING AND THE ANTIPLATELET EFFECT OF CLOPIDOGREL

Clopidogrel is the most widely used P2Y12 inhibitor, which is administered for secondary prevention of atherothrombotic events in patients with cardiovascular disease after myocardial infarction and coronary stenting. Given the complexity of the clopidogrel metabolism and variety of potential drug-drug interactions, the issue of individual variability of its antiplatelet effects is of paramount concern. Another issue of clinical relevance is related to so-called “smoker’s paradox”. This phenomenon implies that in some patients smoking is associated with increased antiplatelet potency of clopidogrel. In this review, we analyze recent international data on the features of pharmacokinetics and pharmacodynamics of clopidogrel, plausible mechanisms of the “smoker’s paradox” and its clinical significance in patients with coronary artery disease. Comparative efficacy of available P2Y12 inhibitors and possible implications of smoking are considered. Pharmacogenetic aspects and the issues of personalized antiplatelet therapy are discussed.

Impact of CYP2C19 Polymorphism on Antiplatelet Potency of Prasugrel 5 and 10 mg Daily Maintenance

Background: Whether genetic polymorphisms (GP) impact residual platelet aggregation (RPA) following prasugrel is unclear, especially during maintenance phase. We assessed the influence of CYP2C19 GP carriers on RPA in the prospective observational cohort study. Methods and Results: All post-stent patients (n = 206) received prasugrel 60 mg loading and either 5 or 10 mg daily maintenance with aspirin100 mg. RPA levels by light transmission aggregometry (LTA), multiplate electrode aggregometry (MEA), and VerifyNow (P2Y12 reaction units, PRU) with CYP2C19 GP were measured simultaneously. Demographics and clinical characteristics were not useful for predicting response after prasugrel. GP carriers exhibited higher RPA (PRU: p = 0.001, LTA: p = 0.001, MEA: p = 0.023) than noncarriers. CYP2C19 carriers had higher RPA for 5 mg (n = 35; LTA: p = 0.043, MEA: p = 0.023) and reached significance for 10 mg (n = 27; LTA: p = 0.001, PRU: p = 0.001) prasugrel. When divided into extensive, intermediate, and poor metabolizers, all exhibited statistical differences among the 3 groups (LTA: 14.9 ± 12.3%, 22.6 ± 14.9%, 22.9 ± 15.6%, p = 0.002; PRU: 104.1 ± 70.8%, 141.8 ± 78.0%, 151.0 ± 84.8%, p = 0.003; MEA: 19.7 ± 8.9%, 24.4 ± 12.2%, 28.1 ± 14.7%, p = 0.002). Conclusion: CYP2C19 GP impacts RPA during maintenance phase prasugrel in Korean outpatients. This effect is consistent for both of the approved prasugrel doses potentially affecting long-term outcomes including bleeding risks. However, the clinical utility of these findings is still uncertain, and requires more evidence from larger randomized trials beyond East Asians.

CRISPLD1 rs12115090 polymorphisms alters antiplatelet potency of clopidogrel in coronary artery disease patients in Chinese Han

BackgroundDual antiplatelet therapy (DAPT) with aspirin and clopidogrel is a recommended treatment for coronary artery disease (CAD) patients undergoing percutaneous coronary intervention (PCI) to reduce the rate of ischemic events and stent thrombosis. However, high on-treatment platelet reactivity (HTPR) during clopidogrel therapy for some patients may lead to outcome failure and occurrence of cardiovascular events. Amounts of studies have proved that genetic factors may contribute to HTPR. In our study, we explored the predictive value of 10 single nucleotide polymorphisms (SNPs) in 8 genes indicated by exome sequencing with clopidogrel efficacy. MethodsTwo hundred and forty-one Han Chinese CAD patients (mean age: 61 ± 10 years) receiving dual antiplatelet therapy were recruited, among which 118 patients administered with 300 mg loading dose (LD) clopidogrel for 12–24 h and 123 subjects administered with 75 mg/day maintain dose (MD) clopidogrel for at least 5 days before discharge. The platelet reaction index (PRI) was determined to reflect clopidogrel response in the patients. Venous blood samples were drawn from all participants to extract genomic DNA. MassARRAY, Sanger sequencing and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) were used to determine the genotypes of 10 SNPs. ResultsAllelic tests showed significant differences in genotype distribution between HTPR and normal on-treatment platelet reactivity (NTPR) patients for 3 SNPs including CYP2C19 rs4244285 (CYP2C19*2) (co-dominant model: p = 0.003, dominant model: p = 0.004, recessive model: p = 0.012), CRISPLD1 rs12115090 (co-dominant model: p = 0.011, dominant model: p = 0.004), and LTA4H rs11108379 (dominant model: p = 0.041). After adjusting for covariates including clinical characteristics of patients, concomitant medications and complications, we confirmed that carriers of the CYP2C19*2 showed significantly increased risk of HTPR (*2/*2 vs *1/*1: OR = 12.266, 95% CI: 1.336–112.592, p = 0.027; *1/*2 + *2/*2 vs *1/*1: OR = 2.202, 95% CI: 1.083–4.480, p = 0.029). Contrarily, carriers of the CRISPLD1 rs12115090 C allele showed significantly reduced risk of HTPR (CC vs AA: OR = 0.242, 95% CI: 0.078–0.752, p = 0.014; CA + CC vs AA: OR = 0.457, 95% CI: 0.232–0.904, p = 0.024) in Chinese CAD patients. In addition, carriers of the CYP2C19*2 allele showed significantly increased PRI (*1/*2 vs *1/*1: p = 0.008, 2/*2 vs 1/*1: p < 0.001, *2/*2 vs 1/*2: p = 0.011), while patients carrying the rs12115090 C allele showed significantly decreased PRI than the wild-type AA homozygotes (CA vs AA: p = 0.046, CA + CC vs AA: p = 0.023). ConclusionCYP2C19*2 reduced the antiplatelet potency of clopidogrel and increased the risk of HTPR, while CRISPLD1 rs12115090 A>C polymorphism increased the antiplatelet potency of clopidogrel. Genetic tests, especially for CYP2C19*2 are recommended in Han Chinese CAD patients before using of clopidogrel.

Acute coronary syndrome remodels the antiplatelet aggregation properties of HDL particle subclasses

Background Although HDLs have antithrombotic effects by reducing platelet activation, the relationship between HDL levels and the risk of acute coronary syndrome (ACS) is unclear, as HDL particles are heterogeneous in composition and biological properties. Objective To characterize the effects of HDL2 and HDL3 subclasses from ACS patients and non-coronary artery disease (CAD) subjects on platelet activation. Methods We measured platelet aggregation and ex vivo thrombus formation, analyzed signaling pathways by flow cytometry, and performed a targeted lipidomics analysis on HDL subclasses. Results Analysis of human platelet aggregation in suspension, adhesion on von Willebrand factor and thrombus formation on collagen under arterial shear demonstrated that HDL2 from ACS patients had higher antiplatelet potency than HDL3 from ACS patients and HDL from non-CAD subjects. HDL binding to scavenger receptor class B type I was essential for this effect. A lipidomics analysis revealed that HDL2 from ACS patients had more oxidized polyunsaturated fatty acids (PUFAs). An inverse correlation between the concentrations of 9-hydroxyoctadecadienoic acid (9-HODE), 13-hydroxyoctadecadienoic acid (13-HODE), the eicosapentaenoic acid metabolite 18-hydroxyeicosapentaenoic acid (18-HEPE) and hydroxyeicosatetraenoic acid isomers in HDL2 and platelet aggregation was observed. This relationship was further demonstrated by the direct inhibitory effects of 18-HEPE, 9-HODE, 13-HODE, 17-hydroxydocosahexaenoic acid and 14-hydroxydocosahexaenoic acid on collagen-related peptide-induced platelet aggregation, indicating that oxidized PUFAs contribute to the antithrombotic effect of ACS HDL2. Conclusions Our data shed new light on the antiplatelet effects of HDL subclasses, and suggest physiological adaptation through the modulation of HDL properties in ACS patients that may limit their platelet-dependent thrombotic risk.

Priapism: A very rare complication of dual antiplatelet therapy after percutaneous coronary intervention

Context: Dual antiplatelet therapy (DAPT), with aspirin and P2Y12 receptor inhibitors, is standard of care in patients with ST elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PCI). However, its use is associated with increased risk of bleeding. We herein report an unusual bleeding complication associated with DAPT after primary PCI. Case Report: A 42-year-old man, who presented with acute inferior wall MI and underwent a successful bare metal placement in circumflex coronary artery, was discharged on dual antiplatelet therapy. However, he presented 2 weeks later with priapism for 20 hours that needed surgical drainage of large amount of blood from his penis. There were no other causes to explain priapism, but since this was not known complication of DAPT, it was not discontinued given his recent stent placement. However, 3 weeks later he suffered another episode of priapism that also needed surgical drainage. Therefore, given its high antiplatelet potency, Prasugrel was eventually discontinued, and the patient was maintained on aspirin only. The decision was guided by optical coherence tomography evaluation of his recent stent to rule out local risks for stent thrombosis. The patient has done well over 14 months of follow up with no cardiac symptoms or recurrence of priapism. Conclusion: To the best of our knowledge, the association between priapism and DAPT was never reported previously. Given the wide use of DAPT after coronary intervention, we believe that interventional cardiologist should be aware of this rare, yet potentially devastating, complication.

Impact of CYP2C19 Polymorphisms on Clinical Outcomes and Antiplatelet Potency of Clopidogrel in Caucasian Poststroke Survivors.

Variable response after clopidogrel is well documented and may affect major adverse clinical events after stroke. Impact of CYP2C19 genetic polymorphisms is an established marker linked to variable response after clopidogrel. However, the association of certain genetic polymorphisms with prediction of major adverse clinical events following stroke still remains controversial, especially in Caucasians. The primary aim was to evaluate the impact of CYP2C19 allele *2 in heterozygote form on major adverse clinical events in Caucasian poststroke survivors treated with clopidogrel. The secondary aim was to analyze the potential link between CYP2C19 genetic polymorphism and variable response after clopidogrel. One hundred thirty patients of Caucasian origin following documented ischemic stroke were included. Platelet reactivity was assessed by light transmittance aggregometry (LTA) and matched with various CYP2C19 loss-of-function genetic polymorphisms and major adverse clinical events (composite of vascular deaths, stroke/transient ischemic attack, and myocardial infarction). Over the mean follow-up of 14.9 months, 19 patients experienced major adverse clinical events. The risk of major adverse clinical events was nearly 3-fold in loss-of-function allele carriers (hazard ratio = 2.904; 95% confidence interval, 1.083-7.786; P = 0.013), whereas the risk of ischemic stroke or transient ischemic attack alone was also higher (hazard ratio = 3.170; 95% confidence interval, 1.281-7.849; P = 0.034). Platelet activity was strongly associated with allele *2 status (rs = 0.21, P = 0.016) but not with other genetic polymorphisms. Carriers of allele*2 exhibited lower platelet response to adenosine diphosphate-mean LTA (30.1% vs. 42.0%; P = 0.017). There were no significant differences in LTA results with other agonists. Strong association of increase in adenosine diphosphate-induced aggregation with diabetes mellitus (rs = 0.20, P = 0.023), increasing age (rs = 0.23, P = 0.008), and conversely diminishing over increased weight (rs = 0.23, P = 0.009) was also detected. The carriers of other gene allele variants lack uniformed impact on variable response after clopidogrel. Even heterozygous CYP2C19*2 allele carriers among Caucasian patients after ischemic stroke had a higher risk of major adverse clinical events. The LTA, however, did not predict major adverse clinical events. The exact clinical utility of these findings is still uncertain and requires large outcome-driven randomized trial in Caucasians for proof of concept.

RELEVANCE OF THE CYP2C19 POLYMORPHISM FOR LOADING AND MAINTENANCE DOSE OF PRASUGREL AND CLOPIDOGREL TREATMENT EFFECT IN CORONARY ARTERY DISEASE PATIENTS UNDERGOING PERCUTANEOUS CORONARY INTERVENTION PCI : THE PRAISE-GENE STUDY

CYP2C19 polymorphism has been associated with altered antiplatelet potency of clopidogrel. On the other hand, prasugrel exerts greater and more consistent platelet inhibition with rapid onset when compared to clopidogrel in both healthy subjects and stable coronary artery disease patients. We sought

Exploration of efficacy and bleeding with combined phosphoinositide 3‐kinase β inhibition and aspirin in man

Based on animal and human data, phosphoinositide 3-kinase (PI3K)β is a promising antithrombotic target. However, the relation between efficacy and bleeding when combined with current antiplatelet therapies is unclear. To strengthen the PI3Kβ target validation using the short-acting inhibitor AZD6482 alone and in different combinations with P2Y12 and cyclooxygenase (COX)-1 inhibition invitro (human platelets), invivo (dog), and in healthy subjects. Evaluation of complete target inhibition of PI3Kβ (by AZD6482), P2Y12 (by ticagrelor), and COX-1 (by aspirin) alone and in the different combinations vs. concentration responses for a panel of platelet agonists invitro (adenosine diphosphate, collagen, thrombin receptor activating peptide) indicates that the rank order of antiplatelet efficacy is P2Y12 >PI3Kβ>COX-1 as monotherapy and P2Y12 plus PI3Kβ >P2Y12 plus COX-1>PI3Kβ plus COX-1 as dual therapy, with little additional effect with triple therapy. Use of a conscious dog model to assess exvivo antiplatelet effect in parallel with bleeding time prolongation (standard incision in the ear) confirms the wide separation of efficacy vs. bleeding for PI3Kβ inhibition and that this separation is reduced when combined with aspirin and more reduced when combined with clopidogrel. In healthy subjects, AZD6482, in combination with aspirin, shows a potential for greater antiplatelet potency but less bleeding potential compared with clopidogrel plus aspirin. PI3Kβ inhibition, in comparison with P2Y12 and COX-1, delivers medium antiplatelet effect but with minimal bleeding. PI3Kβ inhibition, in combination with aspirin, in healthy subjects, provides a potential for greater overall antiplatelet effect compared with clopidogrel plus aspirin, but with significantly less bleeding potential.

In vitro anti-platelet potency of ticagrelor in blood samples from infants and children

IntroductionTicagrelor, a novel platelet inhibitor acting on the ADP-dependent P2Y12 receptor, is currently approved for treating adults with acute coronary syndrome. The effect of ticagrelor in children has not been explored. As a first step, we here evaluate if the in vitro anti-platelet potency of ticagrelor in blood samples from children of different age is different as compared with in blood samples from adults. Materials and MethodsBlood samples from 36 healthy children grouped by age (0–2 months, n=6; 2–6 months, n=6; 6months-2years, n=6; 2–6 years, n=10; 6–12 years, n=8) and 13 adults were collected for in vitro analysis using vasodilator stimulated phosphoprotein phosphorylation (VASP) assay in whole blood and ADP-induced light transmission aggregometry (LTA) in platelet rich plasma. Ticagrelor (0.01 – 10μmol/L) was added in vitro and its potency was assessed by calculating the concentration that provided 50% inhibition of the maximum response (IC50). ResultsThe in vitro potency of ticagrelor in blood from adults and in blood from children of any age group were comparable, both when analyzed with LTA and with VASP. ConclusionsThese in vitro results are consistent with the hypothesis that ticagrelor would achieve a comparable anti-platelet effect in children of different ages as in adults at equal plasma exposure.

Prasugrel overcomes high on-clopidogrel platelet reactivity in the acute phase of acute coronary syndrome and maintains its antiplatelet potency at 30-day follow-up

The aim of this study was to assess antiplatelet effect of prasugrel in acute coronary syndrome (ACS) patients with high on-treatment platelet reactivity (HTPR) on clopidogrel, undergoing percutaneous coronary intervention (PCI). A prospective, platelet reactivity-guided, parallel-group, open-label study including 71 patients pretreated with clopidogrel 600 mg and assigned either to prasugrel (30 mg loading dose, 10 mg maintenance dose; n = 46) or clopidogrel (150 mg maintenance dose for 6 days and thereafter 75 mg maintenance dose; n = 25) regimen, based on vasodilator-stimulated phosphoprotein (VASP)-assessed platelet reactivity index (PRI; > 50% vs. ≤ 50%) measured next morning post-PCI. Median PRI value after switch to prasugrel sharply declined at 24 h (70.0 [61.3-75.6] vs. 11.9 [6.8-25.7]%; p < 0.000001) and slightly but significantly rose between 24 h and 30 days (27.9 [15.5-46.8]%; p < 0.0006). In contrast, median PRI values in the clopidogrel group were similar at baseline and at 24 h (25.1 [13.7-40.2] vs. 22.0 [18.4-36.8]%; p = NS) and then modestly rose at 30 days (30.3 [20.4-45.7]%; p < 0.03). The prevalence of HTPR decreased in the prasugrel group between baseline and 24 h measurements (100.0 vs. 4.3%; p < 0.0001). Rates of patients with HTPR at 24 h and 30 days were similar in both groups, so were the tendencies in patterns of platelet inhibition evaluated with multiple electrode aggregometry as compared with the VASP assay. Our study indicates that prasugrel overcomes HTPR on clopidogrel in the acute phase of interventionally treated ACS and maintains its antiplatelet potency in 30-day follow-up. Potential clinical benefits of personalized antiplatelet prasugrel-based therapy warrant further investigation in clinical ACS trials.