Antiplatelet therapy: new pharmacological agents and changing paradigms

The pharmacology of antiplatelet agents for primary, secondary, and tertiary prevention of ischemic stroke

INTRODUCTION

Ischemic etiology accounts for two thirds of all strokes in which platelet activation and aggregation play a major role. A variety of antiplatelet therapies have been tested for primary, secondary, and tertiary prevention, with certain patient subtypes benefiting more than others from a specific regimen.

AREAS COVERED

This review aims at synthetizing current evidence on pharmacology of antiplatelet agents approved for primary, secondary, and tertiary stroke prevention and their application among possible patient subtypes that may benefit more from their administration.

EXPERT OPINION

Management of ischemic stroke has largely evolved over the past decades. A better understanding of stroke pathophysiology has allowed to identify patients who can benefit most from antiplatelet therapies, with varying degrees of benefit depending on whether these agents are being used for primary, secondary, or tertiary prevention. Importantly, the antiplatelet treatment regimens currently available have expanded and no longer limited to aspirin but include other drugs such as P2Y12 and phosphodiesterase inhibitors, also used in combination, as well as precision medicine approaches using genetic testing aiming at optimizing the safety and efficacy in this population.

Platelets: Orchestrators of immunity in host defense and beyond

Platelets prevent blood loss during vascular injury and contribute to thrombus formation in cardiovascular disease. Beyond these classical roles, platelets are critical for the host immune response. They guard the vasculature against pathogens via specialized receptors, intracellular signaling cascades, and effector functions. Platelets also skew inflammatory responses by instructing innate immune cells, support adaptive immunosurveillance, and influence antibody production and T cell polarization. Concomitantly, platelets contribute to tissue reconstitution and maintain vascular function after inflammatory challenges. However, dysregulated activation of these multitalented cells exacerbates immunopathology with ensuing microvascular clotting, excessive inflammation, and elevated risk of macrovascular thrombosis. This dichotomy underscores the critical importance of precisely defining and potentially modulating platelet function in immunity.

One year clinical outcome of dual anti-platelet therapy with the Novel Ticagrelor plus Aspirin versus Clopidogrel plus Aspirin for Endovascular Intervention of patients with Intracranial Aneurysm: A meta-analysis

BACKGROUND

The use of stents to treat un-ruptured intracranial aneurysms was first approved in the year 2002 in the United States as a Humanitarian Device Exemption. Antiplatelet therapy is mandatory following stent placement. Dual antiplatelet therapy (DAPT) with aspirin and clopidogrel has been the first line agents for the prevention of thromboembolic events following neuro-endovascular procedures. However, clopidogrel hypo-responsiveness has often been observed. In this analysis, we aimed to systematically compare one year clinical outcome of DAPT with the Novel Ticagrelor plus Aspirin versus Clopidogrel plus Aspirin for Endovascular Intervention of patients with Intracranial Aneurysm.

METHODS

Online electronic databases were searched from June 2023 till July 2023 for relevant studies which compared DAPT with ticagrelor or clopidogrel for endovascular intervention in patients with intracranial aneurysm. The endpoints which were analyzed were classified into thromboembolic and hemorrhagic events. A fixed and a random effect statistical model were used during data analysis respectively. Risk ratio (RR) with 95 % confidence interval (CI) was used to represent the data following analysis.

RESULTS

Five studies with a total number of 893 participants were included in this analysis. Three hundred and fifty eight (358) participants were assigned to the ticagrelor group whereas 535 participants were assigned to clopidogrel group. Participants' enrollment period ranged from the year 2009 to 2019. Our results showed that during a mean follow-up time period of one year, DAPT with ticagrelor was associated with significantly lower thromboembolic events with RR: 0.33, 95 % CI: 0.16 - 0.68; P = 0.003. In addition, at one year, DAPT with ticagrelor was not associated with any increase in hemorrhagic events (RR: 0.66, 95 % CI: 0.29 - 1.50; P = 0.32) when compared to DAPT with clopidogrel.

CONCLUSION

At one year, DAPT with ticagrelor was associated with significantly lower thromboembolic events without any increase in hemorrhagic events when compared to clopidogrel associated DAPT for endovascular intervention of patients with intracranial aneurysm. However, even though ticagrelor-associated DAPT use appeared to be more effective and safe, this hypothesis should only be confirmed in larger upcoming trials.

Unraveling the access to the regioselective synthesis of highly functionalized pyranopyrazoles using an ionic liquid catalyst

An efficient and green strategy for the regioselective synthesis of highly functionalized pyranopyrazole via one-pot condensation of 3-methyl-1-phenyl-5-pyrazolone or EAA and hydrazine hydrate, substituted aromatic aldehydes with NMSM [(E)-N-Methyl-1-(methylthio)-2-nitro-ethenamine] in the existence of IL [(EMIM)Ac] as catalyst with solvent-free condition (SFC) is described. This domino protocol produces biologically substantial heterocycles through Knoevenagel condensation proceeded by Michael addition and O-cyclization with an eradication of methanethiol group, which create the one stereo-center and creation of "C-C, C-N, C-O, C=C, C=N, bonds." The final product is produced by exceptionally easy filtering after the reaction mass was triturated with ethanol. The strategy's noteworthy features include the use of biodegradable IL catalyst, excellent to exceptional yield with rapid reaction times, applicability to a wide range of substrate, clear reaction profile, and straightforward workup process.

Breast Tumor Cells Evade the Cytotoxic Action of Anastrozole, Aspirin, and Clopidogrel Cocktail

Globally, breast cancer is among the most frequently diagnosed and common cause of death among women. Aromatase inhibitors, such as anastrozole, are one of the first-line therapies used in the treatment of breast cancer in postmenopausal women; however, thromboembolic complications are common. Thus, this study investigated the combined effects of anastrozole and antiplatelet therapies, aspirin and clopidogrel, on breast cancer cytotoxicity and survival in vitro. Breast cancer cell lines (MCF-7 and T47D) were treated with varying Cmax concentrations of anastrozole and/or antiplatelet therapies for 24 h. A wound-healing scratch assay was used to measure migration and the WST-1 assay for cellular proliferation. An autophagy/cytotoxicity dual staining kit was used to assay cell death and survival. Changes in cell morphology were assessed using scanning electron microscopy. Data were analyzed with Statistica software. Our findings showed that sub-phenotypic differences exist between the luminal-A breast cancer cell lines, with T47D cells being more aggressive than MCF-7 cells. Cellular proliferation and migration responded in a dose-dependent manner for the different treatment groups. Notably, anastrozole combined with aspirin and clopidogrel mediated higher levels of cell survival than each agent individually, with autophagy levels being significantly increased in comparison to that induced with antiplatelet therapy alone.

Targeting Platelet Activation Pathways to Limit Tumour Progression: Current State of Affairs

The association between cancer and a hypercoagulatory environment is well described. Thrombotic complications serve not only as a major mortality risk but the underlying molecular structure and function play significant roles in enhancing tumour progression, which is defined as the tumour's capacity to survive, invade and metastasise, amongst other hallmarks of the disease. The use of anticoagulant or antiplatelet drugs in cardiovascular disease lessens thrombotic effects, but the consequences on tumour progression require interrogation. Therefore, this review considered developments in the management of platelet activation pathways (thromboxane, ADP and thrombin), focusing on the use of Aspirin, Clopidogrel and Atopaxar, and their potential impacts on tumour progression. Published data suggested a cautionary tale in ensuring we adequately investigate not only drug-drug interactions but also those unforeseen reciprocal interactions between drugs and their targets within the tumour microenvironment that may act as selective pressures, enhancing tumour survival and progression.

Antiplatelet Therapy Combined with Anastrozole Induces Features of Partial EMT in Breast Cancer Cells and Fails to Mitigate Breast-Cancer Induced Hypercoagulation

Thromboembolic complications are a leading cause of morbidity and mortality in cancer patients. Cancer patients often present with an increased risk for thrombosis including hypercoagulation, so the application of antiplatelet strategies to oncology warrants further investigation. This study investigated the effects of anastrozole and antiplatelet therapy (aspirin/clopidogrel cocktail or atopaxar) treatment on the tumour responses of luminal phenotype breast cancer cells and induced hypercoagulation. Ethical clearance was obtained (M150263). Blood was co-cultured with breast cancer cell lines (MCF7 and T47D) pre-treated with anastrozole and/or antiplatelet drugs for 24 h. Hypercoagulation was indicated by thrombin production and platelet activation (morphological and molecular). Gene expression associated with the epithelial-to-mesenchymal transition (EMT) was assessed in breast cancer cells, and secreted cytokines associated with tumour progression were evaluated. Data were analysed with the PAST3 software. Our findings showed that antiplatelet therapies (aspirin/clopidogrel cocktail and atopaxar) combined with anastrozole failed to prevent hypercoagulation and induced evidence of a partial EMT. Differences in tumour responses that modulate tumour aggression were noted between breast cancer cell lines, and this may be an important consideration in the clinical management of subphenotypes of luminal phenotype breast cancer. Further investigation is needed before this treatment modality (combined hormone and antiplatelet therapy) can be considered for managing tumour associated-thromboembolic disorder.

Targeting Thymidine Phosphorylase With Tipiracil Hydrochloride Attenuates Thrombosis Without Increasing Risk of Bleeding in Mice

OBJECTIVE

Current antiplatelet medications increase the risk of bleeding, which leads to a clear clinical need in developing novel mechanism-based antiplatelet drugs. TYMP (Thymidine phosphorylase), a cytoplasm protein that is highly expressed in platelets, facilitates multiple agonist-induced platelet activation, and enhances thrombosis. Tipiracil hydrochloride (TPI), a selective TYMP inhibitor, has been approved by the Food and Drug Administration for clinical use. We tested the hypothesis that TPI is a safe antithrombotic medication. Approach and Results: By coexpression of TYMP and Lyn, GST (glutathione S-transferase) tagged Lyn-SH3 domain or Lyn-SH2 domain, we showed the direct evidence that TYMP binds to Lyn through both SH3 and SH2 domains, and TPI diminished the binding. TYMP deficiency significantly inhibits thrombosis in vivo in both sexes. Pretreatment of platelets with TPI rapidly inhibited collagen- and ADP-induced platelet aggregation. Under either normal or hyperlipidemic conditions, treating wild-type mice with TPI via intraperitoneal injection, intravenous injection, or gavage feeding dramatically inhibited thrombosis without inducing significant bleeding. Even at high doses, TPI has a lower bleeding side effect compared with aspirin and clopidogrel. Intravenous delivery of TPI alone or combined with tissue plasminogen activator dramatically inhibited thrombosis. Dual administration of a very low dose of aspirin and TPI, which had no antithrombotic effects when used alone, significantly inhibited thrombosis without disturbing hemostasis.

CONCLUSIONS

This study demonstrated that inhibition of TYMP, a cytoplasmic protein, attenuated multiple signaling pathways that mediate platelet activation, aggregation, and thrombosis. TPI can be used as a novel antithrombotic medication without the increase in risk of bleeding.

Analysis of the Financial Impact of Using Cangrelor on the Safety and Efficacy Outcomes in Patients Undergoing Percutaneous Coronary Intervention in Whom Oral Therapy with P2Y12 Inhibitors is Not Feasible or Desirable, in Spain

PURPOSE

Cangrelor is an intravenous, direct-acting, reversible P2Y12 inhibitor indicated for the reduction of thrombotic cardiovascular events in patients with coronary artery disease (CAD) undergoing percutaneous coronary intervention (PCI) in whom oral P2Y12 inhibitors are not feasible or desirable. The objective was to assess the financial impact of introducing cangrelor into the hospital formulary in Spain.

PATIENTS AND METHODS

A budget impact model was developed to calculate the cost difference between two scenarios (without and with cangrelor) to treat CAD patients undergoing PCI in whom oral P2Y12 inhibitors are not feasible or desirable, over 3 years. Intravenous P2Y12 inhibitor (cangrelor), oral P2Y12 inhibitors (clopidogrel, prasugrel, and ticagrelor), and glycoprotein IIb-IIIa inhibitors (GPIs) for bail-out use were considered. Epidemiological, efficacy (thrombotic events including cardiac death), safety (bleeding events), and costs (€, 2019) data were based on Spanish registries, clinical trials, and meta-analyses. One-way sensitivity analysis established the effect of uncertainty on results.

RESULTS

For years 1, 2, and 3, the target population to receive cangrelor was 607, 1,822, and 3,340 patients, and cangrelor uptake was 23.70%, 58.30%, and 51.30%, respectively. The 3-year budget impact was 1,021,717€ varying from 50,245€ in year 1 to 599,272€ in year 3. The results were sensitive to the number of patients treated with GPIs in Spanish hospitals.

CONCLUSION

Based on our results, the financial effort needed to introduce the use of cangrelor in patients undergoing PCI in whom antiplatelet therapy with oral P2Y12 inhibitors is not feasible or desirable barely exceeds one million € over three years, in Spain.

Acquired bleeding disorders through antithrombotic therapy: the implications for dental practitioners

Antithrombotic medications are one of the most common causes of an acquired bleeding disorder. The majority of these medications are administered orally for a variety of clinical indications. It is important that dental surgeons are aware of these medications, their mechanisms of action and how they can influence the dental management of patients, particularly when undertaking procedures which carry a risk of bleeding.

Factors Affecting the Formation and Treatment of Thrombosis by Natural and Synthetic Compounds

Venous thromboembolism (VTE) refers to deep vein thrombosis (DVT), whose consequence may be a pulmonary embolism (PE). Thrombosis is associated with significant morbidity and mortality and is the third most common cardiovascular disease after myocardial infarction and stroke. DVT is associated with the formation of a blood clot in a deep vein in the body. Thrombosis promotes slowed blood flow, hypoxia, cell activation, and the associated release of many active substances involved in blood clot formation. All thrombi which adhere to endothelium consist of fibrin, platelets, and trapped red and white blood cells. In this review, we summarise the impact of various factors affecting haemostatic disorders leading to blood clot formation. The paper discusses the causes of thrombosis, the mechanism of blood clot formation, and factors such as hypoxia, the involvement of endothelial cells (ECs), and the activation of platelets and neutrophils along with the effects of bacteria and reactive oxygen species (ROS). Mechanisms related to the action of anticoagulants affecting coagulation factors including antiplatelet drugs have also been discussed. However, many aspects related to the pathogenesis of thrombosis still need to be clarified. A review of the drugs used to treat and prevent thrombosis and natural anticoagulants that occur in the plant world and are traditionally used in Far Eastern medicine has also been carried out.

One-Pot Access to Diverse Functionalized Pyran Annulated Heterocyclic Systems Using SCMNPs@BPy-SO3H as a Novel Magnetic Nanocatalyst

The SCMNPs@BPy-SO3H catalyst was prepared and characterized using Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA), Vibrating Sample Magnetometry (VSM), Energy Dispersive X-ray Spectroscopy (EDX), X-ray Diffraction (XRD), and Scanning Electron Microscopy (SEM). Afterwards, its capability was efficiently used to promote the one-pot, three-component synthesis of pyrano[2,3-c]pyrazole and 2-amino-3-cyano-pyrano[3,2-c]chromen-5(4H)-one derivatives. The strategy resulted in the desired products with excellent yields and short reaction times. The SCMNPs@BPy-SO3H catalyst was readily recovered using a permanent magnetic field and it was reused in six runs with a slight decrease in catalytic activity. Copyright © 2020 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

[SBA 2020: Regional anesthesia guideline for using anticoagulants update]

The development of protocols to prevent perioperative Venous Thromboembolism (VTE) and the introduction of increasingly potent antithrombotic drugs have resulted in concerns of increased risk of neuraxial bleeding. Since the Brazilian Society of Anesthesiology (SBA) 2014 guideline, new oral anticoagulant drugs were approved by international regulating agencies, and by ANVISA. Societies and organizations that try to approach concerns through guidelines have presented conflicting perioperative management recommendations. As a response to these issues and to the need for a more rational approach, managements were updated in the present narrative revision, and guideline statements made. They were projected to encourage safe and quality patient care, but cannot assure specific results. Like any clinical guide recommendation, they are subject to review as knowledge grows, on specific complications, for example. The objective was to assess safety aspects of regional analgesia and anesthesia in patients using antithrombotic drugs, such as: possible technique-associated complications; spinal hematoma-associated risk factors, prevention strategies, diagnosis and treatment; safe interval for discontinuing and reinitiating medication after regional blockade.

Combined Anastrozole and Antiplatelet Therapy Treatment Differentially Promotes Breast Cancer Cell Survival

Thromboembolic disorders are the second leading cause of death in breast cancer. Antiplatelet therapy combined with cancer therapy is a potential treatment strategy against cancer-associated thromboembolic disorders; however, the efficacy of such dual treatment has not been established. This study reports novel findings on the response of hormone-dependent breast cancer cell lines (MCF7/T47D) following 24 h treatment with Anastrozole, combined with Aspirin and Clopidogrel cocktail; and Atopaxar. Neutral red and lactate dehydrogenase assays were conducted to assess viability and cytotoxicity respectively. Flow cytometric Annexin-V/PI assay was used to assess the mode of cell death. Morphological alterations were studied using scanning electron microscopy. Statistical analysis was conducted using Statistica V13. Definitive outcomes were established with flow cytometric detection of phosphatidylserine exposure and propidium iodide staining, complemented with ultrastructural analysis. Results showed that a few cells were undergoing death mainly through secondary necrosis. Morphological features suggesting induced cell motility (pseudopodia/ruffled membranes) were observed in both cell lines; notably, T47D cells presented pronounced features than MCF7 cells. Overall, these findings suggest that such combined treatment may differentially promote cell survival, inducing a more aggressive breast cancer phenotype.

Risk of postoperative thromboembolic complication after major digestive surgery in patients receiving antiplatelet therapy: Lessons from more than 3,000 operations in a single tertiary referral hospital

BACKGROUND

Although recent studies have suggested that the continuation of preoperative antiplatelet therapy with aspirin does not affect intraoperative or postoperative bleeding in patients undergoing digestive surgery, its preventive effect against thromboembolic complication remains largely unknown.

METHODS

A total of 3,072 patients who underwent major digestive surgery (esophago-gastrointestinal and hepatobiliary-pancreatic resection for malignancy) between 2005 and 2018 at our institution were enrolled in this study. The patients were divided into 3 groups: patients continuing to receive preoperative antiplatelet therapy with aspirin (continued-antiplatelet therapy group, n = 425), those discontinuing preoperative antiplatelet therapy (discontinued-antiplatelet therapy group, n = 549), and those who were not receiving antiplatelet therapy (non-antiplatelet therapy group, n = 2,117). The CHADS₂ and the CHA₂DS₂-VASc scoring system were used to assess potential thromboembolic risk. Surgical outcomes were compared between the groups and the risk factors for thromboembolic complication, bleeding complication, and operative mortality were determined by multivariate analysis.

RESULTS

There was no difference between the discontinued-antiplatelet therapy and continued-antiplatelet therapy groups in the rate of high risk patients categorized by CHADS₂ and CHA₂DS₂-VASc scores; however, the occurrence of thromboembolic complication in the discontinued-antiplatelet therapy group was significantly higher compared with the continued-antiplatelet therapy group (2.8% vs 0.5%; P = .006). In a multivariate analysis using the whole cohort, discontinuation of antiplatelet therapy (odds ratio = 4.39; P < .001), poor performance status (odds ratio = 4.14; P = .001), and hypertension (odds ratio = 3.46; P = .005) were the independent risk factors for thromboembolic complication. In the groups of patients receiving antiplatelet therapy, multivariate analysis showed that preoperative aspirin continuation had a significant negative impact (odds ratio = 0.10, P = .029) on the occurrence of thromboembolic complication, but did not affect either postoperative bleeding complication or operative mortality.

CONCLUSION

Discontinuation of antiplatelet therapy during major digestive surgery is the most significant risk factor for thromboembolic complication, and the continuation of preoperative aspirin therapy significantly reduces the occurrence of thromboembolic complication in patients receiving antiplatelet therapy. It is suggested that the preoperative continuation of aspirin monotherapy is one of the preferred options to prevent severe thromboembolic events during major digestive surgery in patients receiving antiplatelet therapy.

A Review of Antiplatelet Activity of Traditional Medicinal Herbs on Integrative Medicine Studies

Thrombotic events mainly occurred by platelet activation and aggregation. The vascular occlusion causes serious disease states such as unstable angina, ischemic stroke, and heart attack. Due to the pervading of thrombotic diseases, new antiplatelet drugs are necessary for preventing and treating arterial thrombosis without adverse side effects. Traditional medicinal herbs have been used for the treatment of human ailments for a long time. The clinically useful and safe products from traditional medicinal herbs were identified and developed in numerous pharmacological approaches. A complementary system of traditional medicinal herbs is a good candidate for pharmacotherapy. However, it still has a limitation in its function and efficacy. Thus, it is necessary to study the mode of action of traditional medicinal herbs as alternative therapeutic agents. In this review, we focused on our current understanding of the regulatory mechanisms of traditional medicinal herbs in antiplatelet activity and antithrombotic effect of traditional medicinal herbs on platelet function.

Platelet Signaling and Disease: Targeted Therapy for Thrombosis and Other Related Diseases

Platelets are essential for clotting in the blood and maintenance of normal hemostasis. Under pathologic conditions such as atherosclerosis, vascular injury often results in hyperactive platelet activation, resulting in occlusive thrombus formation, myocardial infarction, and stroke. Recent work in the field has elucidated a number of platelet functions unique from that of maintaining hemostasis, including regulation of tumor growth and metastasis, inflammation, infection, and immune response. Traditional therapeutic targets for inhibiting platelet activation have primarily been limited to cyclooxygenase-1, integrin αIIbβ3, and the P2Y12 receptor. Recently identified signaling pathways regulating platelet function have made it possible to develop novel approaches for pharmacological intervention in the blood to limit platelet reactivity. In this review, we cover the newly discovered roles for platelets as well as their role in hemostasis and thrombosis. These new roles for platelets lend importance to the development of new therapies targeted to the platelet. Additionally, we highlight the promising receptor and enzymatic targets that may further decrease platelet activation and help to address the myriad of pathologic conditions now known to involve platelets without significant effects on hemostasis.

Neutrophils in critical illness

During critical illness, dramatic alterations in neutrophil biology are observed including abnormalities of granulopoeisis and lifespan, cell trafficking and antimicrobial effector functions. As a result, neutrophils transition from powerful antimicrobial protectors into dangerous mediators of tissue injury and organ dysfunction. In this article, the role of neutrophils in the pathogenesis of critical illness (sepsis, trauma, burns and others) will be explored, including pathological changes to neutrophil function during critical illness and the utility of monitoring aspects of the neutrophil phenotype as biomarkers for diagnosis and prognostication. Lastly, we review findings from clinical trials of therapies that target the harmful effects of neutrophils, providing a bench-to-bedside perspective on neutrophils in critical illness.

Clopidogrel non-responsiveness in patients undergoing percutaneous coronary intervention using the VerifyNow test: frequency and predictors

Objectives

Stent thrombosis and death after percutaneous coronary intervention (PCI) can be caused by a phenomenon known as clopidogrel non-responsiveness which has been shown to occur in approximately 5%–44% of patients. We investigated the responsiveness of clopidogrel in an Iraqi series of cases. Our aim was to determine for the first time the frequency and predictors of clopidogrel non-responsiveness among Iraqi patients with ischaemic heart disease undergoing PCI.

Methods

The study was conducted at the Cardiac Catheterization Center, Baghdad Teaching Hospital, Medical City, from January to May 2014, and included patients who presented for PCI. A platelet aggregation test was performed for those patients using the VerifyNow system.

Results

A total of 115 patients (mean age: 58.3±10.1 years; male sex: 73.9%) were included in the study. 18.3% of the study population were clopidogrel non-responders, which was comparable with the results of a Chinese study (20.28%, P=0.796) but contrasted with other reports from Jordan, Brazil and Thailand. The major independent predictive factor for non-responsiveness in our report was diabetes mellitus (OR 5.96, 95% CI 2.23 to 13.71; P=0.001), followed by hypertension (OR 4.135, P=0.035), obesity (OR 3.44, P=0.037) and male sex (OR 3.039, P=0.045). Previous use of clopidogrel (OR 0.17, P=0.02) and younger age (OR 0.72, P=0.026) were identified as protective factors.

Conclusions

In this study, 18.3% of patients were non-responders to clopidogrel and the major independent predictive factors for non-responsiveness were diabetes mellitus, hypertension, obesity and male sex.

Low body weight and clinical outcomes in acute coronary syndrome patients: results of the ACHILLES Registry

BACKGROUND

Being overweight increases the risk of cardiovascular diseases and mortality. However, among high-body-weight patients with established acute coronary syndrome (ACS) this evidence is not clear. In this scenario, a low body weight (LBW) has been proposed to confer higher prognostic risk and higher bleeding risk with new P2Y₁₂ inhibitors.

AIMS

We aimed to examine differences in mortality, catheterizations/revascularizations, antiplatelet therapy and ischemic/bleeding adverse events between ACS patients with LBW.

METHODS

This is a multicenter registry involving 1576 consecutive ACS patients (ST-elevation myocardial infarction (STEMI), non-STEMI, or unstable angina) from three tertiary institutions. Patients were divided into two groups: LBW (weight < 60 kg, n = 176) and non-LBW (weight ⩾ 60 kg, n = 1400). During 12 months follow-up, we recorded management (catheterizations/revascularizations), antiplatelet therapy, major adverse cardiovascular events (MACEs), bleeding events (BARC classification), and mortality.

RESULTS

Catheterizations (86.4% vs. 93.4%; p = 0.001) and revascularizations (64.8% vs. 76.1%; p = 0.001) were significantly lower in the LBW group. At discharge, prescription of new P2Y₁₂ inhibitors was also lower in LBW patients (24.4% vs. 37.8%; p = 0.001). After 12-month follow-up, the incidence of MACE (HR 1.61 (95% CI 1.03-2.50]; p = 0.038) and mortality (HR 2.18 (95% CI 1.33-3.58); p = 0.002) was higher in LBW patients compared with non-LBW. In contrast, there were no significant differences for bleeding events.

CONCLUSIONS

LBW in ACS patients was associated with higher incidence of MACE and mortality. In this group of patients less catheterizations and coronary revascularizations were performed. Despite there being no differences in bleeding rates, new P2Y₁₂ inhibitors were less prescribed in LBW patients.

Adenosine A2A receptor agonists with potent antiplatelet activity

Selected adenosine A_2A receptor agonists (PSB-15826, PSB-12404, and PSB-16301) have been evaluated as new antiplatelet agents. In addition, radioligand-binding studies and receptor-docking experiments were performed in order to explain their differential biological effects on a molecular level. Among the tested adenosine derivatives, PSB-15826 was the most potent compound to inhibit platelet aggregation (EC₅₀ 0.32 ± 0.05 µmol/L) and platelet P-selectin cell-surface localization (EC₅₀ 0.062 ± 0.2 µmol/L), and to increase intraplatelets cAMP levels (EC₅₀ 0.24 ± 0.01 µmol/L). The compound was more active than CGS21680 (EC₅₀ 0.97±0.07 µmol/L) and equipotent to NECA (EC₅₀ 0.31 ± 0.05 µmol/L) in platelet aggregation induced by ADP. In contrast to the results from cAMP assays, K_i values determined in radioligand-binding studies were not predictive of the A_2A agonists' antiplatelet activity. Docking studies revealed the key molecular determinants of this new family of adenosine A_2A receptor agonists: differences in activities are related to π-stacking interactions between the ligands and the residue His264 in the extracellular loop of the adenosine A_2A receptor which may result in increased residence times. In conclusion, these results provide an improved understanding of the requirements of antiplatelet adenosine A_2A receptor agonists.

Antithrombotic therapy for secondary prevention of atherothrombotic events in cerebrovascular disease

Atherothrombosis is the common underlying process for numerous progressive manifestations of cardiovascular disease, including coronary artery disease (CAD) and cerebrovascular disease (CVD). Antiplatelet therapy is the cornerstone of pharmacological management in patients with atherothrombosis. Over the past 20 years, major advances in antiplatelet pharmacotherapy have been made, particularly for the treatment of patients with CAD. The treatment of patients with concomitant CAD and CVD is complex, owing to their increased risk of both ischaemia and bleeding. When CVD arises from large artery atherosclerosis, antithrombotic therapies are essential to prevent stroke or transient ischaemic attack (TIA). However, the use of antithrombotic medications in patients with CVD can put them at high risk of intracranial haemorrhage. As such, the risk-benefit profile of various combinations of antiplatelet agents in patients with both CAD and CVD is uncertain. This Review provides a state-of-the-art account of the available evidence on antithrombotic therapies for the secondary prevention of atherothrombotic events in patients with concomitant CAD and CVD, particularly those with a history of noncardioembolic stroke or TIA.

Antithrombotic therapy for secondary prevention of atherothrombotic events in cerebrovascular disease

Atherothrombosis is the common underlying process for numerous progressive manifestations of cardiovascular disease, including coronary artery disease (CAD) and cerebrovascular disease (CVD). Antiplatelet therapy is the cornerstone of pharmacological management in patients with atherothrombosis. Over the past 20 years, major advances in antiplatelet pharmacotherapy have been made, particularly for the treatment of patients with CAD. The treatment of patients with concomitant CAD and CVD is complex, owing to their increased risk of both ischaemia and bleeding. When CVD arises from large artery atherosclerosis, antithrombotic therapies are essential to prevent stroke or transient ischaemic attack (TIA). However, the use of antithrombotic medications in patients with CVD can put them at high risk of intracranial haemorrhage. As such, the risk-benefit profile of various combinations of antiplatelet agents in patients with both CAD and CVD is uncertain. This Review provides a state-of-the-art account of the available evidence on antithrombotic therapies for the secondary prevention of atherothrombotic events in patients with concomitant CAD and CVD, particularly those with a history of noncardioembolic stroke or TIA.

Novel Antiplatelet Activity of Minocycline Involves Inhibition of MLK3-p38 Mitogen Activated Protein Kinase Axis

Platelets play an essential role in hemostasis and wound healing by facilitating thrombus formation at sites of injury. Platelets also mediate inflammation and contain several pro-inflammatory molecules including cytokines and chemokines that mediate leukocyte recruitment and activation. Not surprisingly, platelet dysfunction is known to contribute to several inflammatory disorders. Antiplatelet therapies, such as aspirin, adenosine diphosphate (ADP) antagonists, glycoprotein IIb/IIIa (GPIIb/IIIa) inhibitors, and anticoagulants such as warfarin, dampen platelet activity at the risk of unwarranted bleeding. Thus, the development of drugs that reduce platelet-mediated inflammation without interfering with thrombus formation is of importance to combat platelet-associated disorders. We have shown here for the first time that the tetracycline antibiotic, minocycline, administered to HIV-infected individuals reduces plasma levels of soluble CD40L and platelet factor 4 levels, host molecules predominately released by platelets. Minocycline reduced the activation of isolated platelets in the presence of the potent platelet activator, thrombin, as measured by ELISA and flow cytometry. Platelet degranulation was reduced upon exposure to minocycline as shown by mepacrine retention and flow cytometry. However, minocycline had no effect on spreading, aggregation, GPIIb/IIIa activation, or in vivo thrombus formation. Lastly, immunoblot analysis suggests that the antiplatelet activity of minocycline is likely mediated by inhibition of mixed lineage kinase 3 (MLK3)-p38 MAPK signaling axis and loss of p38 activity. Our findings provide a better understanding of platelet biology and a novel repurposing of an established antibiotic, minocycline, to specifically reduce platelet granule release without affecting thrombosis, which may yield insights in generating novel, specific antiplatelet therapies.

Thrombin-Mediated Platelet Activation of Lysed Whole Blood and Platelet-Rich Plasma: A Comparison Between Platelet Activation Markers and Ultrastructural Alterations

Platelet ultrastructural alterations representing spurious activation have been identified in pathological conditions. A limitation of platelet studies is that sample preparation may lead to artifactual activation processes which may confound results, impacting the use of scanning electron microscopy as a supplemental diagnostic tool. We used scanning electron microscopy and flow cytometry to analyze platelet activation in platelet-rich plasma (PRP) and whole blood (WB) samples. PRP generated using a single high g force centrifugation, and WB samples treated with a red blood cell lysis buffer, were exposed to increasing concentrations of the agonist thrombin. Platelets in lysed WB samples responded to thrombin by elevating the activation marker CD62p definitively, with corresponding ultrastructural changes indicating activation. Conversely, CD62p expression in PRP preparations remained static. Ultrastructural analysis revealed fully activated platelets even under low concentration thrombin stimulation, with considerable fibrin deposition. It is proposed that the method for PRP production induced premature platelet activation, preventable by using an inhibitor of platelet aggregation and fibrin polymerization. Nevertheless, our results show a definitive correspondence between flow cytometry and scanning electron microscopy in platelet activation studies, highlighting the potential of the latter technique as a supplemental diagnostic tool.

A novel thromboxane receptor antagonist, nstpbp5185, inhibits platelet aggregation and thrombus formation in animal models

A novel benzimidazole derivative, nstpbp5185, was discovered through in vitro and in vivo evaluations for antiplatelet activity. Thromaboxane receptor (TP) is important in vascular physiology, haemostasis and pathophysiological thrombosis. Nstpbp5185 concentration-dependently inhibited human platelet aggregation caused by collagen, arachidonic acid and U46619. Nstpbp5185 caused a right-shift of the concentration-response curve of U46619 and competitively inhibited the binding of 3H-SQ-29548 to TP receptor expressed on HEK-293 cells, with an IC50 of 0.1 µM, indicating that nstpbp5185 is a TP antagonist. In murine thrombosis models, nstpbp5185 significantly prolonged the latent period in triggering platelet plug formation in mesenteric and FeCl3-induced thrombi formation, and increased the survival rate in pulmonary embolism model with less bleeding than aspirin. This study suggests nstpbp5185, an orally selective anti-thrombotic agent, acting through blockade of TXA2 receptor, may be efficacious for prevention or treatment of pathologic thrombosis.

Allosterism-based simultaneous, dual anticoagulant and antiplatelet action: allosteric inhibitor targeting the glycoprotein Ibα-binding and heparin-binding site of thrombin

BACKGROUND

Allosteric inhibition is a promising approach for developing a new group of anticoagulants with potentially reduced bleeding consequences. Recently, we designed sulfated β-O4 lignin (SbO4L) as an allosteric inhibitor that targets exosite 2 of thrombin to reduce fibrinogen cleavage through allostery and compete with glycoprotein Ibα to reduce platelet activation.

OBJECTIVE

To assess: (i) the antithrombotic potential of a novel approach of simultaneous exosite 2-dependent allosteric inhibition of thrombin and competitive inhibition of platelet activation; and (ii) the promise of SbO4L as the first-in-class antithrombotic agent.

METHODS

A combination of whole blood thromboelastography, hemostasis analysis, mouse arterial thrombosis models and mouse tail bleeding studies were used to assess antithrombotic potential.

RESULTS AND CONCLUSIONS

SbO4L extended the clot initiation time, and reduced maximal clot strength, platelet contractile force, and the clot elastic modulus, suggesting dual anticoagulant and antiplatelet effects. These effects were comparable to those observed with enoxaparin. A dose of 1 mg of SbO4L per mouse prevented occlusion in 100% of arteries, and lower doses resulted in a proportionally reduced response. Likewise, the time to occlusion increased by ~ 70% with a 0.5-mg dose in the mouse Rose Bengal thrombosis model. Finally, tail bleeding studies demonstrated that SbO4L does not increase bleeding propensity. In comparison, a 0.3-mg dose of enoxaparin increased the bleeding time and blood volume loss. Overall, this study highlights the promise of the allosteric inhibition approach, and presents SbO4L as a novel anticoagulant with potentially reduced bleeding side effects.

A Comparative Study of Molecular Structure, pKa, Lipophilicity, Solubility, Absorption and Polar Surface Area of Some Antiplatelet Drugs

Theoretical chemistry methods have been used to study the molecular properties of antiplatelet agents (ticlopidine, clopidogrel, prasugrel, elinogrel, ticagrelor and cangrelor) and several thiol-containing active metabolites. The geometries and energies of most stable conformers of these drugs have been computed at the Becke3LYP/6-311++G(d,p) level of density functional theory. Computed dissociation constants show that the active metabolites of prodrugs (ticlopidine, clopidogrel and prasugrel) and drugs elinogrel and cangrelor are completely ionized at pH 7.4. Both ticagrelor and its active metabolite are present at pH = 7.4 in neutral undissociated form. The thienopyridine prodrugs ticlopidine, clopidogrel and prasugrel are lipophilic and insoluble in water. Their lipophilicity is very high (about 2.5–3.5 logP values). The polar surface area, with regard to the structurally-heterogeneous character of these antiplatelet drugs, is from very large interval of values of 3–255 Ų. Thienopyridine prodrugs, like ticlopidine, clopidogrel and prasugrel, with the lowest polar surface area (PSA) values, exhibit the largest absorption. A high value of polar surface area (PSA) of cangrelor (255 Ų) results in substantial worsening of the absorption in comparison with thienopyridine drugs.

A New Generation of Antiplatelet, and Anticoagulant Medication and the Implications for the Dental Surgeon

The management of dental patients taking either antiplatelet medication, anticoagulant medication or both has been well established in the previous literature. Recently, new generations of drugs have emerged which are becoming increasingly common, including direct thrombin inhibitors, factor X inhibitors and a new class of oral thienopyridines. The implications of these drugs for the dental surgeon are not yet fully known. Awareness remains low and there is very little information available within the literature on safe use during surgery. This review paper aims to provide some guidance for dental practitioners performing invasive procedures. CPD/CLINICAL RELEVANCE: A new generation of anticoagulant and antiplatelet drugs have serious implications for patients undergoing surgery and their use is increasing.

Antithrombotic therapy in peripheral artery disease

Antiplatelet agents are recommended for the reduction of major adverse cardiovascular events among all patients with symptomatic peripheral artery disease. However, the optimal antiplatelet regimen and duration of therapy in peripheral artery disease (PAD) remains unclear, largely due to limited and conflicting data in this patient population. This article reviews current data on antithrombotic therapy in PAD and discusses the implications of this data for current practice and future research.

Acute Myocardial Infarction in Women: A Scientific Statement From the American Heart Association

Cardiovascular disease is the leading cause of mortality in American women. Since 1984, the annual cardiovascular disease mortality rate has remained greater for women than men; however, over the last decade, there have been marked reductions in cardiovascular disease mortality in women. The dramatic decline in mortality rates for women is attributed partly to an increase in awareness, a greater focus on women and cardiovascular disease risk, and the increased application of evidence-based treatments for established coronary heart disease. This is the first scientific statement from the American Heart Association on acute myocardial infarction in women. Sex-specific differences exist in the presentation, pathophysiological mechanisms, and outcomes in patients with acute myocardial infarction. This statement provides a comprehensive review of the current evidence of the clinical presentation, pathophysiology, treatment, and outcomes of women with acute myocardial infarction.

Using implementation science to help integrate preoperative evidence-based measures into practice for vascular surgery patients

The preoperative workup is a necessary and crucial evaluation for patients undergoing major vascular surgery. It is important to assess for likelihood of perioperative adverse events and then implement evidence-based measures to reduce identified medical comorbidities and improve the quality of patient care and outcomes after surgery. Although there are numerous opportunities to implement evidence-based processes during the preoperative period, there are many barriers that can prevent vascular surgeons from achieving these goals. This review will discuss how an implementation science-based approach can be used by members of the vascular surgery team to identify appropriate preoperative evidence-based interventions for diverse practice settings and to overcome barriers and allow integration of these interventions as part of the routine preoperative workup.

A Study of the Management of Patients Taking Novel Oral Antiplatelet or Direct Oral Anticoagulant Medication Undergoing Dental Surgery in a Rural Setting

PURPOSE

Novel oral antiplatelet (NOAP) (prasugrel and ticagrelor) and direct oral anticoagulant drugs (DOAC) (dabigatran, rivaroxaban and apixaban) have emerged in the last decade. This study was undertaken to determine current approaches taken to the management of patients taking these agents in dental practice in a remote and rural setting.

METHODS

A small retrospective study was carried out in a small island population that identified patients taking one of the above drugs. All national health service and private dental records were examined to determine the type of treatment carried out and whether drug therapy, treatment plans or actual treatment were modified as a result of NOAP or DOAC therapy. In addition other outcomes such as referral to another service for advice or treatment and any adverse bleeding events were noted.

RESULTS

156 dental encounters for 95 patients taking one of the drugs were identified. Significant events were identified in sixteen encounters and the management of patients taking each drug type differed significantly between cases but no patients returned with troublesome post-operative bleeding.

CONCLUSIONS

The approaches taken by dental surgeons in Orkney in the management of the NOAPs and DOACs varied and this is likely to be a reflection of the limited literature available.

New approaches to inhibiting platelets and coagulation

Ischemic heart disease and stroke are major causes of death and morbidity worldwide. Coronary and cerebrovascular events are a consequence of thrombus formation caused by atherosclerotic plaque rupture or embolism, both of which result from platelet activation and aggregation and thrombin-mediated fibrin generation via the coagulation cascade. Current and emerging antiplatelet and anticoagulant agents are evolving rapidly. The use of aspirin for primary prevention continues to be controversial, as are the doses appropriate for secondary prevention. Development of new oral and intravenous adenosine diphosphate P2Y12 inhibitors and novel antiplatelet agents continues to transform the landscape of antiplatelet therapy. Oral anticoagulation has advanced with the use of direct thrombin and factor Xa inhibitors that do not require therapeutic monitoring. In this review, we discuss the pharmacology and growing clinical evidence for traditional and new antiplatelet and anticoagulant therapies.

Cangrelor for the treatment of arterial thrombosis: pharmacokinetics/pharmacodynamics and clinical data

INTRODUCTION

Dual antiplatelet therapy is the standard of care for patients with acute coronary syndromes or with recent coronary stents implantation. P2Y12 receptor antagonists have shown to reduce the risk of recurrent ischemic events among these patients, at the expense of an increased risk of bleeding. Cangrelor is a novel, intravenous, short-acting, reversible platelet P2Y12 inhibitor, which has been evaluated for the treatment of arterial thrombosis.

AREAS COVERED

Studies on the pharmacological characteristics of cangrelor and clinical trials were retrieved by a PubMed literature search.

EXPERT OPINION

Cangrelor has been tested in patients with coronary artery diseases undergoing percutaneous coronary intervention and as bridging therapy for patients undergoing coronary artery bypass graft. The rapid peak of action allows a fast and complete inhibition of platelet aggregation; the rapid offset is advantageous in case of bleeding complications; and finally, the intravenous administration also makes this drug suitable for patients unable to consume oral medications. Unfortunately, the large clinical trials evaluating cangrelor in percutaneous coronary intervention did not show superiority to the standard antiplatelet therapy, and its future use in this setting still needs to be better assessed. Conversely, when used as bridging therapy to coronary artery bypass graft, cangrelor showed promising results.