Platelet thrombin receptor antagonism and atherothrombosis

Discovery of Potent and Selective Quinoxaline-Based Protease-Activated Receptor 4 (PAR4) Antagonists for the Prevention of Arterial Thrombosis

PAR4 is a promising antithrombotic target with potential for separation of efficacy from bleeding risk relative to current antiplatelet therapies. In an effort to discover a novel PAR4 antagonist chemotype, a quinoxaline-based HTS hit 3 with low μM potency was identified. Optimization of the HTS hit through the use of positional SAR scanning and the design of conformationally constrained cores led to the discovery of a quinoxaline-benzothiazole series as potent and selective PAR4 antagonists. The lead compound 48, possessing a 2 nM IC50 against PAR4 activation by γ-thrombin in platelet-rich plasma (PRP) and greater than 2500-fold selectivity versus PAR1, demonstrated robust antithrombotic efficacy and minimal bleeding in the cynomolgus monkey models.

Thrombin as target for prevention of recurrent events after acute coronary syndromes

The mechanism underlying thrombus formation in acute coronary syndrome (ACS) involves both platelets and thrombin. While both pathways are targeted in acute care, platelet inhibition has been predominantly administered in the chronic phase, yet thrombin plays a key role in platelet activation and fibrin formation. Among ACS patients, there is also a persistent chronic increase in thrombin generation, which is associated with a higher rate of adverse events. In the setting of post-ACS care with rivaroxaban or vorapaxar, targeting thrombin has been associated with decreased thrombin generation and reduced cardiovascular events, but has been associated with increased bleeding risk. We explored the evidence supporting thrombin generation in the pathophysiology of recurrent events post-ACS and the role of thrombin as a viable therapeutic target. One specific target is factor XI inhibition, which is involved in thrombin generation, but may also allow for the preservation of normal hemostasis.

Comparison of Ticagrelor Monotherapy and Ticagrelor Plus Aspirin Among Patients With Acute Coronary Syndrome Combined With High-Risk of Gastrointestinal Bleeding After Percutaneous Coronary Intervention: A Retrospective Cohort Study

ABSTRACT

To date, no studies have specifically examined the efficacy of P2Y12 inhibitor monotherapy in patients with acute coronary syndrome (ACS) exhibiting a high risk of gastrointestinal (GI) bleeding following percutaneous coronary intervention (PCI). This was a retrospective cohort study of ACS exhibiting a high GI bleeding risk after PCI admitted to the Affiliated Hospital of the Jiangnan University from August 2016 to December 2019. Of the 308 enrolled patients, 269 were found eligible and were assigned to the ticagrelor monotherapy (TIC) arm (n = 128) and to ticagrelor plus aspirin (TIC + ASP) arm (n = 141) treatment for a 1-year period. The primary study outcome was a composite end point, including bleeding academic research consortium (BARC) type 2, 3, or 5 bleeding and adverse cardiac or cerebrovascular events; 8 (6.3%) in the TIC group and 14 (9.9%) in the combination treatment group reached the primary ischemic end point within 1 year with no significant difference between these groups. BARC type 2, 3, and 5 bleeding events affected significantly more patients in the combination group relative to the TIC group (38 [27.0%] vs. 11 [8.6%], P < 0.001). As the follow-up interval was prolonged, the cumulative BARC type 2, 3, and 5 bleeding incidence in the TIC group remained significantly below than that in the combination treatment group ( P < 0.05). These results indicate that TIC is associated with a lower risk of clinically relevant bleeding events among ACS with a high risk of GI bleeding after PCI relative to combination TIC + ASP treatment, although ischemic outcomes in these 2 groups were similar.

A Contemporary Review of Antiplatelet Therapies in Current Clinical Practice

Antiplatelet therapy plays a crucial role in a number of cardiovascular disorders. We currently have a range of antiplatelet agents in our armamentarium. In this review, we aim to summarise the common antiplatelet agents currently available, and their use in clinic practice. We not only highlight recent trials exploring antiplatelet therapy in atherosclerotic cardiovascular disease, but also in trials related to transcatheter aortic valve implantation and coronavirus disease 2019. Inevitably, the antithrombotic benefits of these drugs are accompanied by an increase in bleeding complications. Therefore, an individualised approach to weighing each patient's thrombotic risk versus bleeding risk is imperative, in order to improve clinical outcomes.

The role of monocytes in thrombotic diseases: a review

Cardiovascular and cerebrovascular diseases are the number one killer threatening people's life and health, among which cardiovascular thrombotic events are the most common. As the cause of particularly serious cardiovascular events, thrombosis can trigger fatal crises such as acute coronary syndrome (myocardial infarction and unstable angina), cerebral infarction and so on. Circulating monocytes are an important part of innate immunity. Their main physiological functions are phagocytosis, removal of injured and senescent cells and their debris, and development into macrophages and dendritic cells. At the same time, they also participate in the pathophysiological processes of pro-coagulation and anticoagulation. According to recent studies, monocytes have been found to play a significant role in thrombosis and thrombotic diseases of the immune system. In this manuscript, we review the relationship between monocyte subsets and cardiovascular thrombotic events and analyze the role of monocytes in arterial thrombosis and their involvement in intravenous thrombolysis. Finally, we summarize the mechanism and therapeutic regimen of monocyte and thrombosis in hypertension, antiphospholipid syndrome, atherosclerosis, rheumatic heart disease, lower extremity deep venous thrombosis, and diabetic nephropathy.

Low dose rivaroxaban for the management of atherosclerotic cardiovascular disease

Atherosclerotic cardiovascular disease is characterized by some risk of major adverse events despite the availability of effective medical therapies for secondary prevention. There is emerging evidence suggesting that thrombin partly contributes to this residual risk. In fact, thrombin (i.e., activated coagulation factor II) triggers not only the conversion of fibrinogen to fibrin but also platelet activation and various pathways responsible for pro-atherogenic and/or pro-inflammatory effects through interaction with protease activated receptors. To reduce the risk associated with thrombin activation, oral anticoagulants antagonists of vitamin K showed promise, but were associated with unacceptable bleeding rates. Direct oral anticoagulants targeting the activated factors X and II carry a lower risk of bleeding than vitamin K antagonists. Rivaroxaban, a direct inhibitor of activated factor X approved at the dose of 20 mg once daily for the prevention of thromboembolic events, has been also investigated at a reduced dose of 2.5 mg twice daily in several alternative scenarios of atherosclerotic cardiovascular disease, in combination with standard of care. Current guidelines recommend that low-dose rivaroxaban is given in an adjunct to standard therapy to patients with stable atherosclerosis and acute coronary syndromes at low bleeding risk. Several studies are underway to evaluate its putative benefits in other clinical settings.

Synthesis of 12-quinoline substituted andrographolide derivatives and their preliminary evaluation as anti-aggregation drugs

Based on the structure of the natural product andrographolide, a series of novel 12-quinoline substituted derivatives 9 were designed and synthesized. In preliminary biological evaluation, these synthesized compounds showed prominent anti-platelet aggregation activities in response to thrombin and adenosine diphosphate (ADP) agonists. Among them, compound 9o (inhibition rate 55.73%, IC50 0.36 µM/L) had the highest anti-platelet aggregation activity induced by ADP. Compound 9q (inhibition rate 54.31%, IC50 0.30 µM/L) showed the highest anti-platelet aggregation activity induced by thrombin. Most of the derivatives had no significant cytotoxicity. Our research results provide a novel candidate drug structure for anti-platelet aggregation and enrich the scope of application of andrographolide derivatives.

Predicting Arterial Thrombotic Events Following Peripheral Revascularization Using Objective Viscoelastic Data

Background Peripheral artery disease is endemic in our globally aging population, with >200 million affected worldwide. Graft/stent thrombosis after revascularization is common and frequently results in amputation, major adverse cardiovascular events, and cardiovascular mortality. Optimizing medications to decrease thrombosis is of paramount importance; however, limited guidance exists on how to use and monitor antithrombotic therapy in this heterogeneous population. Thromboelastography with platelet mapping (TEG-PM) provides comprehensive coagulation metrics and may be integral to the next stage of patient-centered thrombophrophylaxis. This prospective study aimed to determine if TEG-PM could predict subacute graft/stent thrombosis following lower extremity revascularization, and if objective cut point values could be established to identify those high-risk patients. Methods and Results We conducted a single-center prospective observational study of patients undergoing lower extremity revascularization. Patients were followed up for the composite end point postoperative graft/stent thrombosis at 1 year. TEG-PM analysis of the time point before thrombosis in the event group was compared with the last postoperative visit in the nonevent group. Cox proportional hazards analysis examined the association of TEG-PM metrics to thrombosis. Cut point analysis explored the predictive capacity of TEG-PM metrics for those at high risk. A total of 162 patients were analyzed, of whom 30 (18.5%) experienced graft/stent thrombosis. Patients with thrombosis had significantly greater platelet aggregation (79.7±15.7 versus 58.5±26.4) and lower platelet inhibition (20.7±15.6% versus 41.1±26.6%) (all P<0.01). Cox proportional hazards analysis revealed that for every 1% increase in platelet aggregation, the hazard of experiencing an event during the study period increased by 5% (hazard ratio, 1.05 [95% CI, 1.02-1.07]; P<0.01). An optimal cut point of >70.8% platelet aggregation and/or <29.2% platelet inhibition identifies those at high risk of thrombosis with 87% sensitivity and 70% to 71% specificity. Conclusions Among patients undergoing lower extremity revascularization, increased platelet reactivity was predictive of subacute postoperative graft/stent thrombosis. On the basis of the cut points of >70.8% platelet aggregation and <29.2% platelet inhibition, consideration of an alternative or augmented antithrombotic regimen for high-risk patients may decrease the risk of postoperative thrombotic events.

Clinical pharmacology of antiplatelet drugs

INTRODUCTION

Platelets play a key role in arterial thrombosis and antiplatelet therapy is pivotal in the treatment of cardiovascular disease. Current antiplatelet drugs target different pathways of platelet activation and show specific pharmacodynamic and pharmacokinetic characteristics, implicating clinically relevant drug-drug interactions.

AREAS COVERED

This article reviews the role of platelets in hemostasis and cardiovascular thrombosis, and discusses the key pharmacodynamics, drug-drug interactions and reversal strategies of clinically used antiplatelet drugs.

EXPERT OPINION

Antiplatelet therapies target distinct pathways of platelet activation: thromboxane A₂ synthesis, adenosine diphosphate-mediated signaling, integrin α_IIbβ₃ (GPIIb/IIIa), thrombin-mediated platelet activation via the PAR1 receptor and phosphodiesterases. Key clinical drug-drug interactions of antiplatelet agents involve acetylsalicylic acid - ibuprofen, clopidogrel - omeprazole, and morphine - oral P2Y₁₂ inhibitors, all of which lead to an attenuated antiplatelet effect. Platelet function and genetic testing and the use of scores (ARC-HBR, PRECISE-DAPT, ESC ischemic risk definition) may contribute to a more tailored antiplatelet therapy. High on-treatment platelet reactivity presents a key problem in the acute management of ST-elevation myocardial infarction (STEMI). A treatment strategy involving early initiation of an intravenous antiplatelet agent may be able to bridge the gap of insufficient platelet inhibition in high ischemic risk patients with STEMI.

Dual Antiplatelet Therapy After Drug-Eluting Stents Implantation in East Asians: A Network Meta-Analysis of Randomized Controlled Trials

ABSTRACT

Dual antiplatelet therapy (DAPT) is essential to prevent the risk of ischemia events, but it is difficult to avoid concurrent bleeding events. East Asians are associated with a higher tendency of bleeding than Caucasians, which may affect the DAPT duration. Therefore, this network meta-analysis to explore optimum DAPT duration for East Asians. The related randomized controlled trials that compared the different DAPT duration in East Asian patients were included by searching PubMed, EMBASE, and Cochrane Library database. The outcomes included myocardial infarction, stent thrombosis, all-cause death, stroke, and major bleeding. In addition, net adverse cardiac and cardiovascular events was defined as a composite outcome in this study. We calculated the odds ratio (OR) and 95% confidence intervals for end point events by the fixed effects model in the Bayesian's network frame. We included a total of 12 randomized controlled trials with 30,640 patients. Compared with 12-month DAPT, 1- to 3-month DAPT is effective in myocardial infarction (OR 0.72, 0.46-1.08), stents thrombosis (OR 1.27, 0.59-2.84), all-cause death (OR 0.91, 0.65-1.28), and stroke (OR 0.89, 0.57-1.39). The 1- to 3-month DAPT was associated with a lower risk of major bleeding compared with 12-month DAPT (OR 0.55, 0.4-0.76), 6-month DAPT (OR 0.54, 0.31-0.94), and >12-month DAPT (OR 0.43, 0.28-0.65). In addition, more than 12 months of DAPT did not reduce the incidence of myocardial infarction (OR 0.75, 0.51-1.11) and increased the risk of major bleeding (OR 1.28, 0.88-1.87) compared with 12-month DAPT. The 1- to 3-month DAPT was more secure and effective than the other 3 DAPT strategies. Although East Asians have a higher risk of bleeding, more than 12 months of DAPT does not increase this incidence of major bleeding.

Antiplatelet therapy after percutaneous coronary intervention

Antiplatelet therapy is key to reducing local thrombotic complications and systemic ischaemic events among patients undergoing percutaneous coronary interventions (PCI), but it is inevitably associated with increased bleeding. The continuous refinement in stent technologies, together with the high incidence of ischaemic recurrences after PCI and the understanding of prognostic implications associated with bleeding, have led to a substantial evolution in antiplatelet treatment regimens over the past decades. Numerous investigations have been conducted to better stratify patients undergoing PCI according to their ischaemic and bleeding risks and to implement antithrombotic regimens accordingly. Evidence from these investigations have resulted in a number of antithrombotic treatment options as recommended by recent guidelines. In this State-of-the-Art review we provide the rationale, summarise the evidence, and discuss current and future directions of antiplatelet treatment regimens after PCI.

The Role of Antiplatelet Therapy in Patients With MINOCA

Myocardial infarction with non-obstructive coronary arteries (MINOCA) is a heterogeneous group of clinical entities characterized by the common clinical evidence of myocardial infarction (MI) with non-obstructive coronary arteries on coronary angiography and without an overt cause for the MI. Platelets play a cornerstone role in the pathophysiology of MI with obstructive coronary arteries. Accordingly, antiplatelet therapy is recommended for treating patients with MI and obstructive coronary disease. However, the role of platelets in the pathophysiology of MINOCA patients is not fully defined, questioning the role of antiplatelet therapy in this setting. In this review, we will assess the role of antiplatelet therapy in MINOCA with a focus on the pathophysiology, therapeutic targets, current evidence, and future directions according to its different etiologies.

Duration of Dual Antiplatelet Therapy After Implantation of Drug-Coated Balloon

The drug-coated balloon (DCB) is an emerging percutaneous coronary intervention (PCI) device with theoretical advantages and promising results. Recent clinical observations have demonstrated that DCB tends to have both good efficacy and a good safety profile in the treatment of in-stent restenosis (ISR) for both bare-metal and drug-eluting stents (DES), de novo coronary artery disease (CAD), and other situation, such as high bleeding risk, chronic total occlusion, and acute coronary syndrome (ACS). Dual antiplatelet therapy (DAPT) has become an essential medication in daily clinical practice, but the optimal duration of DAPT after the implantation of a DCB remains unknown. At the time of the first in vivo implantation of paclitaxel-DCB for the treatment of ISR in 2006, the protocol-defined DAPT duration was only 1 month. Subsequently, DAPT duration ranging from 1 to 12 months has been recommended by various trials. However, there have been no randomized controlled trials (RCTs) on the optimal duration of DAPT after DCB angioplasty. Current clinical guidelines normally recommend the duration of DAPT after DCB-only angioplasty based on data from RCTs on the optimal duration of DAPT after stenting. In this review, we summarized current clinical trials on DCB-only angioplasty for different types of CADs and their stipulated durations of DAPT, and compared their clinical results such as restenosis, target lesion revascularization (TLR) and stent thrombosis event. We hope this review can assist clinicians in making reasonable decisions about the duration of DAPT after DCB implantation.

PAR-1 Antagonism to Promote Gut Mucosa Healing in Crohn's Disease Patients: A New Avenue for CVT120165

A new paradigm has been added for the treatment of inflammatory bowel diseases such as Crohn's disease and ulcerative colitis. In addition to resolving symptoms and inflammatory cell activation, the objective of tissue repair and mucosal healing is also now considered a primary goal. In the search of mediators that would be responsible for delayed mucosal healing, protease-activated receptor-1 (PAR-1) has emerged as a most interesting target. Indeed, in Crohn's disease, the endogenous PAR-1 agonist thrombin is drastically activated. Activation of PAR-1 is known to be associated with epithelial dysfunctions that hamper mucosal homeostasis. This review gathers the scientific evidences of a potential role for PAR-1 in mucosal damage and mucosal dysfunctions associated with chronic intestinal inflammation. The potential clinical benefits of PAR-1 antagonism to promote mucosal repair in CD patients are discussed. Targeted local delivery of a PAR-1 antagonist molecule such as CVT120165, a formulated version of the FDA-approved PAR-1 antagonist vorapaxar, at the mucosa of Crohn's disease patients could be proposed as a new indication for IBD that could be rapidly tested in clinical trials.

[Are there alternatives to dual antiplatelet therapy after stenting of peripheral arteries?]

It is estimated that more than 200 million people worldwide suffer peripheral artery disease and the rate of amputations remains at a high level. The basis of treatment is timely revascularization wherein the fraction of interventions performed endovascularly has steadily been growing both in Russia and abroad. Nevertheless, the parameters of long-term patency of endovascular reconstructions of the infrainguinal segment are still inferior to open interventions. In order to select an optimal method of revascularization and to predict the duration of patency of the reconstruction modern clinical guidelines suggest using the GLASS and WIfI scales, which may improve the remote results of the intervention. Moreover, modern paclitaxel-coated stents and balloons may help increase primary patency of the reconstruction after endovascular procedures. A not less important method of improving remote results of endovascular treatment of patients with peripheral artery disease is considered to be the use of contemporary regimens of antithrombotic therapy. The VOYAGER PAD trial showed that in patients with peripheral artery disease after endured revascularization of lower limbs rivaroxaban prescribed at a dose of 2.5 mg twice daily in a combination with conventional antithrombocytic therapy made it possible to decrease the risk of such ischaemic complications as acute limb ischaemia, major amputation, myocardial infarction, ischaemic stroke and death of cardiovascular causes.

Antiplatelet Activity of Cucurbita maxima

Natural extracts constitute an important source in the prevention of noncommunicable diseases, such as cardiovascular diseases. The pumpkin, Cucurbita maxima, is widely consumed in Chile. Pumpkin seeds, despite having crude protein, lipids, and carbohydrates, are regarded as agro-industrial waste. In this work, we correlated the antiplatelet activity of aqueous, ethanolic, and methanolic extracts from pumpkin seeds with their bioactive compounds. In vitro platelet aggregation and activation studies were performed by turbidimetry and flow cytometry, respectively. Results reveal that the extracts inhibited, in a dose-dependent manner, platelet aggregation induced by adenosine diphosphate, thrombin receptor activator peptide 6 (TRAP-6), and collagen. Pumpkin seed extracts inhibited P-selectin secretion and glycoprotein IIb/IIIa activation on TRAP-6-activated platelets. They were found to be rich in fatty acids and a powerful source of plant-based protein, which could be related to the high antiplatelet potential identified in extracts. This research demonstrated that pumpkin seed extracts could be a candidate in the prevention of thrombotic events.

The efficacy and safety of rivaroxaban in coronary artery disease patients with heart failure and sinus rhythm: a systematic review and meta-analysis

PURPOSE

To explore the efficacy and safety of rivaroxaban in patients with coronary artery disease (CAD), heart failure (HF) and sinus rhythm (SR).

METHODS

Comprehensive literature searches were conducted using the PubMed, Cochrane Library, Embase, CNKI and Wanfang databases from inception to February 2021. Randomized controlled trials (RCTs) focusing on the efficacy and safety of new oral anticoagulant (NOAC) therapy in CAD and HF patients in SR were eligible. Statistical analyses were performed using R Programming Language.

RESULTS

Three RCTs included 10,658 adult patients treated with antiplatelet drugs with or without rivaroxaban were ultimately analysed. The average follow-up period was 20.4-24 months. Rivaroxaban had a favourable point estimate in myocardial infarction (MI) and stroke (MI rivaroxaban group (3.83%, 203/5306) vs. APT group (4.52%, 214/4731), RR = 0.78, 95% CI 0.65-0.94, P < 0.01, I² = 0%), (stroke: rivaroxaban group (1.60%, 85/5306) vs. APT group (2.52%, 119/4731), RR = 0.64, 95% CI 0.49-0.85, P < 0.01, I² = 12%) compared with the placebo. Rivaroxaban was comparable to the placebo for all-cause death and major bleeding (all-cause death: rivaroxaban group (12.27%, 688/5606) vs. APT group (14.59%, 737/5052), RR = 0.73, 95% CI 0.49-1.06, P > 0.05, I² = 87%), (major bleeding: rivaroxaban group (1.52%, 85/5586) vs. APT group (1.37%, 69/5043), RR = 1.18, 95% CI 0.86-1.62, P > 0.05, I² = 0%).

CONCLUSIONS

In SR patients with CAD and HF, the rates of MI and stroke associated with rivaroxaban combined with APT were lower than those associated with APT alone, and the two treatments had similar rates of all-cause death and major bleeding.

Antithrombotic Therapy in Patients with Peripheral Artery Disease: A Focused Review on Oral Anticoagulation

Peripheral artery disease (PAD) is a major cause of morbidity and mortality but it is usually underdiagnosed and undertreated. Patients with PAD present dysregulated procoagulant, anticoagulant, and fibrinolytic pathways leading to arterial and venous thrombosis. The risk of several ischemic-related complications could be mitigated with appropriate antithrombotic therapy, which plays a central role in all types of PAD. For years, antiplatelets have been indicated in patients with symptomatic PAD or those who have undergone revascularization. Unfortunately, a non-negligible proportion of patients with PAD will suffer from adverse events during the follow-up, even despite proper medical therapies for the prevention of PAD complications. Thus, there is room for improving clinical outcomes in these patients. Given the implication of both, primary and secondary hemostasis in arterial thrombosis and the pathophysiology of PAD, the combination of antiplatelets and anticoagulants has emerged as a potential antithrombotic alternative to antiplatelets alone. In this narrative review article, we have highlighted the most recent evidence about antithrombotic therapy in PAD patients, with a special focus on oral anticoagulation. Certainly, COMPASS and VOYAGER PAD trials have shown promising results. Thus, rivaroxaban in combination with aspirin seem to reduce cardiovascular outcomes with a similar bleeding risk compared to aspirin alone. Nevertheless, results from real-world studies are needed to confirm these observations, and other trials will provide novel evidence about the safety and efficacy of emerging anticoagulant agents.

Antithrombotic therapy in diabetes: which, when, and for how long?

Cardiovascular disease remains the main cause of mortality in individuals with diabetes mellitus (DM) and also results in significant morbidity. Premature and more aggressive atherosclerotic disease, coupled with an enhanced thrombotic environment, contributes to the high vascular risk in individuals with DM. This prothrombotic milieu is due to increased platelet activity together with impaired fibrinolysis secondary to quantitative and qualitative changes in coagulation factors. However, management strategies to reduce thrombosis risk remain largely similar in individuals with and without DM. The current review covers the latest in the field of antithrombotic management in DM. The role of primary vascular prevention is discussed together with options for secondary prevention following an ischaemic event in different clinical scenarios including coronary, cerebrovascular, and peripheral artery diseases. Antiplatelet therapy combinations as well as combination of antiplatelet and anticoagulant agents are examined in both the acute phase and long term, including management of individuals with sinus rhythm and those with atrial fibrillation. The difficulties in tailoring therapy according to the variable atherothrombotic risk in different individuals are emphasized, in addition to the varying risk within an individual secondary to DM duration, presence of complications and predisposition to bleeding events. This review provides the reader with an up-to-date guide for antithrombotic management of individuals with DM and highlights gaps in knowledge that represent areas for future research, aiming to improve clinical outcome in this high-risk population.

Changes in serum serotonin levels in patients with acute coronary syndrome and stable angina undergoing percutaneous coronary intervention

OBJECTIVE

Activated platelets release serotonin, causing platelet aggregation and vasoconstriction. Serotonin levels were investigated in patients with acute coronary syndrome (ACS) and chronic stable angina (CSA) treated with percutaneous coronary intervention (PCI).

METHODS

Consecutive patients undergoing PCI for either ACS or CSA were enrolled between July 2009 and April 2010. Patients were pre-treated with dual antiplatelet agents (aspirin and clopidogrel) before PCI. Serum serotonin levels, measured at baseline, pre- and post-PCI, and at 90 min, and 6, 12, 24 and 48 h following PCI, were compared between ACS and CSA groups.

RESULTS

Sixty-three patients with ACS and 60 with CSA were included. Overall baseline characteristics were similar between the two groups. Serotonin levels at post-PCI (55.2 ± 120.0 versus 20.1 ± 24.0) and at peak (regardless of timepoint; 94.0 ± 170.9 versus 38.8 ± 72.3) were significantly higher in the ACS versus CSA group. At 90 min and 6, 24 and 48 h post-PCI, serum serotonin was numerically, but not significantly, higher in patients with ACS. Serotonin levels fluctuated in both groups, showing an initial rise and fall, rebound at 24 h and drop at 48 h post-PCI.

CONCLUSIONS

In patients undergoing PCI, serum serotonin was more elevated in patients with ACS than those with CSA, suggesting the need for more potent and sustained platelet inhibition, particularly in patients with ACS.

Dual antiplatelet therapy (PEGASUS) vs. dual pathway (COMPASS): a head-to-head in vitro comparison

Dual antiplatelet therapy (DAPT) with aspirin and a P2Y12 inhibitor is prescribed for 1-year after myocardial infarction. Two clinical strategies are considered at 1-year: continuation of DAPT or "Dual Pathway" (DP), using aspirin and rivaroxaban. No head-to-head comparative studies exist. In our in-vitro study, 24 samples of donor blood were treated with clinically proven concentrations of 5 antithrombotic regimens: aspirin, ticagrelor, rivaroxaban, DAPT, and DP. Thrombosis was analyzed using the Total Thrombus Analysis System (T-TAS) to measure both antiplatelet and anticoagulant effects. Flow cytometry was performed to quantify platelet activation. DAPT was the most potent antiplatelet regimen, delaying thrombus onset (p < .0001) and reducing thrombogenicity (p < .0001), relative to control. DP did not delay thrombus formation relative to aspirin alone (p = .69). DP was the most potent anticoagulant regimen, delaying thrombus onset (p < .0001) and reducing thrombogenicity (p < .0001), relative to control. DP showed synergistic antithrombotic effects by delaying thrombus onset (p < .0001) and reducing thrombogenicity (p = .0003), relative to rivaroxaban alone. Flow cytometry showed only DAPT (p = .0023) reduced platelet activation. DP treatment demonstrated synergistic antithrombotic effects over rivaroxaban alone, but no additional antiplatelet synergism over aspirin alone.

Impact of Transcatheter Aortic Valve Implantation on Thrombin Generation and Platelet Function

BACKGROUND

 Transcatheter aortic valve implantation (TAVI) is an evolving treatment of severe aortic valve stenosis. However, thromboembolic events such as stroke are common, predominantly early after TAVI. Optimal periprocedural antithrombotic regime is unknown. Especially, as antithrombotic medication enhances bleeding risk, thrombin generation and platelet function are crucial in the pathogenesis of ischemic events. However, the impact of the TAVI procedure on thrombin formation and platelet reactivity is not known by now.

METHODS

 We evaluated thrombin levels using thrombin-antithrombin (TAT) complexes and prothrombin fragments (PTFs) using enzyme-linked immunosorbent assay. Furthermore, platelet reactivity was measured via light transmission aggregometry before and 2 hours after TAVI in 198 patients.

RESULTS

 TAT complexes and PTF F1 + 2 substantially increased during TAVI. Postprocedurally, TAT complexes and PTF were significantly higher after TAVI compared with percutaneous coronary intervention due to acute myocardial infarction, while preprocedural TAT complexes and PTF F1 + 2 did not differ. In contrast, platelet reactivity was not altered early after TAVI. Only adenosine diphosphate-induced aggregation was reduced, reflecting preprocedural loading with clopidogrel.

CONCLUSION

 In this pilot study, we were able to demonstrate that thrombin generation is significantly increased early after TAVI, while platelet function is not affected. Increased thrombin concentrations may contribute to the high risk of postprocedural thromboembolic events. This leads to the hypothesis that extended peri-interventional anticoagulation early after TAVI may be an approach to reduce thromboembolic events.

Integrin αIIbβ3 outside-in signaling activates human platelets through serine 24 phosphorylation of Disabled-2

Background

Bidirectional integrin αIIbβ3 signaling is essential for platelet activation. The platelet adaptor protein Disabled-2 (Dab2) is a key regulator of integrin signaling and is phosphorylated at serine 24 in eukaryotic cells. However, the mechanistic insight and function of Dab2-serine 24 phosphorylation (Dab2-pSer24) in platelet biology are barely understood. This study aimed to define whether and how Dab2 is phosphorylated at Ser24 during platelet activation and to investigate the effect of Dab2-pSer24 on platelet function.

Results

An antibody with confirmed specificity for Dab2-pSer24 was generated. By using this antibody as a tool, we showed that protein kinase C (PKC)-mediated Dab2-pSer24 was a conservative signaling event when human platelets were activated by the platelet agonists such as thrombin, collagen, ADP, 12-O-tetradecanoylphorbol-13-acetate, and the thromboxane A2 activator U46619. The agonists-stimulated Dab2-pSer24 was attenuated by pretreatment of platelets with the RGDS peptide which inhibits integrin outside-in signaling by competitive binding of integrin αIIb with fibrinogen. Direct activation of platelet integrin outside-in signaling by combined treatment of platelets with manganese dichloride and fibrinogen or by spreading of platelets on fibrinogen also resulted in Dab2-pSer24. These findings implicate that Dab2-pSer24 was associated with the outside-in signaling of integrin. Further analysis revealed that Dab2-pSer24 was downstream of Src-PKC-axis and phospholipase D1 underlying the integrin αIIbβ3 outside-in signaling. A membrane penetrating peptide R11-Ser24 which contained 11 repeats of arginine linked to the Dab2-Ser24 phosphorylation site and its flanking sequences (RRRRRRRRRRR¹⁹APKAPSKKEKK²⁹) and the R11-S24A peptide with Ser24Ala mutation were designed to elucidate the functions of Dab2-pSer24. R11-Ser24 but not R11-S24A inhibited agonists-stimulated Dab2-pSer24 and consequently suppressed platelet spreading on fibrinogen, with no effect on platelet aggregation and fibrinogen binding. Notably, Ser24 and the previously reported Ser723 phosphorylation (Dab2-pSer723) occurred exclusively in a single Dab2 molecule and resulted in distinctive subcellular distribution and function of Dab2. Dab2-pSer723 was mainly distributed in the cytosol of activated platelets and associated with integrin inside-out signaling, while Dab2-pSer24 was mainly distributed in the membrane fraction of activated platelets and associated with integrin outside-in signaling.

Conclusions

These findings demonstrate for the first time that Dab2-pSer24 is conservative in integrin αIIbβ3 outside-in signaling during platelet activation and plays a novel role in the control of cytoskeleton reorganization and platelet spreading on fibrinogen.

Pharmacodynamic Comparison of Ticagrelor Monotherapy Versus Ticagrelor and Aspirin in Patients After Percutaneous Coronary Intervention: The TEMPLATE (Ticagrelor Monotherapy and Platelet Reactivity) Randomized Controlled Trial

Background

To assess differences in platelet inhibition during ticagrelor monotherapy (TIC) or dual therapy with ticagrelor and aspirin (TIC+ASP) in patients after percutaneous coronary intervention using a comprehensive panel of functional tests.

Methods and Results

In a single‐center parallel group, open label, randomized controlled trial, 110 participants were randomized to receive either TIC (n=55) or TIC+ASP (n=55) for 4 weeks. The primary outcome was the platelet aggregation response with 10 μmol/L thrombin receptor activation peptide‐6 (TRAP‐6). The secondary outcomes were platelet aggregation responses and binding of surface activation markers with a panel of other activators. The mean percentage aggregation for 10 μmol/L TRAP‐6 was similar for the TIC and TIC+ASP groups (mean difference+4.29; 95% CI, −0.87 to +9.46). Aggregation was higher in the TIC group compared with the TIC+ASP group with 1 μg/mL (+6.47; +2.04 to +10.90) and 0.5 μg/mL (+14.00; +7.63 to +20.39) collagen related peptide. Aggregation responses with 5 μmol/L TRAP‐6, 5 μmol/L or 2.5 μmol/L thromboxane A₂ receptor agonist and surface activation marker binding with 5 μmol/L TRAP‐6 or 0.5 μg/mL collagen related peptide were the same between the treatment groups.

Conclusions

Patients with PCI show similar levels of inhibition of most platelet activation pathways with TIC compared with dual therapy with TIC + ASP. However, the greater aggregation response with collagen related peptide during TIC indicates incomplete inhibition of glycoprotein VI (collagen) receptor‐mediated platelet activation. This difference in pharmacodynamic response to anti‐platelet medication may contribute to the lower bleeding rates observed with TIC compared with dual antiplatelet therapy in recent clinical trials.

Registration Information

URL: https://www.isrctn.com; Unique Identifier ISRCTN84335288.

Antithrombotic Therapy for Atherosclerotic Cardiovascular Disease Risk Mitigation in Patients With Coronary Artery Disease and Diabetes Mellitus

Patients with diabetes mellitus (DM) are characterized by enhanced thrombotic risk attributed to multiple mechanisms including hyperreactive platelets, hypercoagulable status, and endothelial dysfunction. As such, they are more prone to atherosclerotic cardiovascular events than patients without DM, both before and after coronary artery disease (CAD) is established. In patients with DM without established CAD, primary prevention with aspirin is not routinely advocated because of its increased risk of major bleeding that largely offsets its ischemic benefit. In patients with DM with established CAD, secondary prevention with antiplatelet drugs is an asset of pharmacological strategies aimed at reducing the risk of atherosclerotic cardiovascular events and their adverse prognostic consequences. Such antithrombotic strategies include single antiplatelet therapy (eg, with aspirin or a P2Y₁₂ inhibitor), dual antiplatelet therapy (eg, aspirin combined with a P2Y₁₂ inhibitor), and dual-pathway inhibition (eg, aspirin combined with the vascular dose of the direct oral anticoagulant rivaroxaban) for patients with chronic ischemic heart disease, acute coronary syndromes, and those undergoing percutaneous coronary intervention. Because of their increased risk of thrombotic complications, patients with DM commonly achieve enhanced absolute benefit from more potent antithrombotic approaches compared with those without DM, which most often occurs at the expense of increased bleeding. Nevertheless, studies have shown that when excluding individuals at high risk for bleeding, the net clinical benefit favors the use of intensified long-term antithrombotic therapy in patients with DM and CAD. Several studies are ongoing to establish the role of novel antithrombotic strategies and drug formulations in maximizing the net benefit of antithrombotic therapy for patients with DM. The scope of this review article is to provide an overview of current and evolving antithrombotic strategies for primary and secondary prevention of atherosclerotic cardiovascular events in patients with CAD and DM.

Protease activated receptor 4 (PAR4) antagonists: Research progress on small molecules in the field of antiplatelet agents

Protease activated receptor 4 (PAR4) is a key target in antiplatelet medication to reduce the risk of heart attack and thrombotic complications in stroke. PAR4 antagonists can prevent harmful and stable thrombus growth while retaining initial thrombus formation by acting on the late diffusion stage of platelet activation, which may provide a safer alternative than other antiplatelet agents. Currently, research on PAR4 antagonists is of increasing interest in the field of antiplatelet agents. This article provides an overview of the discovery and development of small-molecule antagonists of PAR4 as novel antiplatelet agents, including structure-activity relationship (SAR) analysis, progress of structure and bioassay optimization, and the latest structural and/or clinical information of representative small-molecule antagonists of PAR4.

Pharmacodynamic Effects of Vorapaxar in Prior Myocardial Infarction Patients Treated With Potent Oral P2Y12 Receptor Inhibitors With and Without Aspirin: Results of the VORA-PRATIC Study

Background Vorapaxar as an adjunct to dual antiplatelet therapy (DAPT) reduces thrombotic events in patients with prior myocardial infarction at the expense of increased bleeding. Withdrawal of aspirin has emerged as a bleeding reduction strategy. The pharmacodynamic effects of vorapaxar with potent P2Y12 inhibitors as well as the impact of dropping aspirin is unexplored and represented the aim of the VORA-PRATIC (Vorapaxar Therapy in Patients With Prior Myocardial Infarction Treated With Newer Generation P2Y12 Receptor Inhibitors Prasugrel and Ticagrelor) study. Methods and Results Post-myocardial infarction patients (n=130) on standard DAPT (aspirin+prasugrel or ticagrelor) were randomized to 1 of 3 arms: (1) triple therapy: aspirin+prasugrel/ticagrelor+vorapaxar; (2) dual therapy (drop aspirin): prasugrel/ticagrelor+vorapaxar; (3) DAPT: aspirin+prasugrel/ticagrelor. Pharmacodynamic assessments were performed at 3 time points (baseline and 7 and 30 days). Vorapaxar reduced CAT (collagen-ADP-TRAP)-induced platelet aggregation, a marker of platelet-mediated global thrombogenicity (triple therapy versus DAPT at 30 days: mean difference=-27; 95% CI,-35 to -19; P<0.001; primary end point). This effect was attenuated but still significant in the absence of aspirin (dual therapy versus DAPT at 30 days: mean difference=-15; 95% CI,-23 to -7; P<0.001; between-group comparisons, P<0.05). Vorapaxar abolished TRAP-induced aggregation (P<0.001), without affecting thrombin generation and clot strength. There were no differences in markers of P2Y12 reactivity. Markers sensitive to aspirin-induced effects increased (P<0.001) in the dual-therapy arm. Conclusions In post-myocardial infarction patients treated with potent P2Y12 inhibitors, vorapaxar reduces platelet-driven global thrombogenicity, an effect that persisted, albeit attenuated, in the absence of aspirin and without affecting markers of P2Y12 reactivity or clot kinetics. The clinical implications of these PD observations warrant future investigation. Registration URL: https://www.clini​caltr​ials.gov. Unique identifier: NCT02545933.

[Combined Antithrombotic Therapy in Patients with a Stable Atherosclerotic Cardiovascular Diseases: What Direction did COMPASS Show?]

In patients with stable ischemic heart disease (IHD) and/or peripheral artery disease (PAD), current secondary prevention, including the antiplatelet monotherapy, is associated with a significant residual risk of recurrent cardiovascular complications (CVC). Practical application of results from many modern studies evaluating the effect of secondary prevention of atherothrombosis is complicated. An additional influence on coagulation may play a key role in prevention of atherothrombosis. In the COMPASS study, adding rivaroxaban 2.5 mg, b.i.d., to the acetylsalicylic acid (ASA) monotherapy significantly reduced the risk of death from cardiovascular complications, myocardial infarction or stroke, or all-cause death compared to the ASA monotherapy, in patients with IHD or PAD. The combination antithrombotic therapy was associated with an increased risk of major, but not fatal, or intracranial bleeding. In addition, PAD patients had a reduced risk of severe ischemic lower limb complications, including amputations. According to the subgroup analysis in the COMPASS study, supplementing ASA with rivaroxaban 2.5 mg, b.i.d., may appear most beneficial for patients with stable atherosclerotic disease and with a high risk of severe CVC without causing an increased risk of bleeding.

Clinical Significance of Thrombin Blockade with Low Doses (2.5 mg) of Rivaroxaban in Ischemic Heart Disease Patients

Arterial thrombosis is a result of complex interaction between blood cells, soluble coagulation factors in plasma and vessel wall. Antiplatelet drugs do not always provide the necessary antithrombotic effect of sufficient strength, because their influence does not extend to all three factors involved in this process. Low doses of direct oral inhibitors of thrombin are able to potentiate antithrombotic effect of antiplatelet therapy. The combination of rivaroxaban in a dose of 2.5 mg and standard double antiplatelet therapy turned out to be the most promising for clinical use, since studies with dabigatran and apixaban at the II and III stages of the trials were found to be unsuccessful due to the unacceptably high frequency of bleeding. Studies of the combination of rivaroxaban at a dose of 2.5 mg and standard antiplatelet therapy conducted in previous years among patients with acute myocardial infarction showed a decrease in the frequency of complications of atherothrombosis associated with their ischemic nature, while at the same time there was a slight increase in hemorrhagic complications. In the COMPASS study the combination of rivaroxaban (2.5 mg) plus aspirin reduced the risk of the primary endpoint (myocardial infarction, ischemic stroke, cardiovascular death) more significantly than aspirin alone in patients with stable ischemic heart disease and ischemic brain disease. The pathophysiological rationales for the use of low doses of rivaroxaban when added to dual antiplatelet therapy are considered, and the significance of recent studies in patients with acute coronary syndrome, stable ischemic heart disease and in the prevention of ischemic stroke is discussed.

Dual-pathway inhibition for secondary and tertiary antithrombotic prevention in cardiovascular disease

Advances in antiplatelet therapies for patients with cardiovascular disease have improved patient outcomes over time, but the challenge of balancing the risks of ischaemia and bleeding remains substantial. Moreover, many patients with cardiovascular disease have a residual risk of ischaemic events despite receiving antiplatelet therapy. Therefore, novel strategies are needed to prevent clinical events through mechanisms beyond platelet inhibition and with an acceptable associated risk of bleeding. The advent of non-vitamin K antagonist oral anticoagulants, which attenuate fibrin formation by selective inhibition of factor Xa or thrombin, has renewed the interest in dual-pathway inhibition strategies that combine an antiplatelet agent with an anticoagulant drug. In this Review, we highlight the emerging pharmacological rationale and clinical development of dual-pathway inhibition strategies for the prevention of atherothrombotic events in patients with different manifestations of cardiovascular disease, such as coronary artery disease, cerebrovascular disease and peripheral artery disease.

The continuous challenge of antithrombotic strategies in diabetes: focus on direct oral anticoagulants

Direct oral anticoagulants (DOACs) include dabigatran, which inhibits thrombin, and apixaban, edoxaban, and rivaroxaban, which inhibit factor Xa. They have been extensively studied in large trials involving patients affected by the most common cardiovascular diseases. As the presence of diabetes leads to peculiar changes in primary and secondary hemostasis, in this review we highlight the current evidence regarding DOAC use in diabetic patients included in the majority of recently conducted studies. Overall, in trials involving patients with atrial fibrillation, data seem to confirm at least a similar efficacy and safety of DOACs compared to warfarin in patients with or without diabetes. Furthermore, in diabetic patients, treatment with DOACs is associated with a significant relative reduction in vascular death compared to warfarin. In trials enrolling patients undergoing percutaneous coronary intervention, results concerning bleeding events are consistent in patients with or without diabetes. With regards to the COMPASS study, in patients with diabetes (n = 10,241), addition of rivaroxaban 2.5 mg to aspirin resulted in a significantly lower incidence of major adverse cardiovascular events (HR 0.74, 95% CI 0.61-0.90; interaction p = 0.68) with higher rates of major bleeding expected (HR 1.70, 95% CI 1.25-2.31). The 3287 patients with peripheral artery disease and diabetes receiving rivaroxaban plus aspirin had a twofold higher absolute reduction in the composite endpoint (cardiovascular death, myocardial infarction, and stroke) than patients without diabetes. Finally, we report the involvement of cytochromes or P-glycoprotein on the metabolism of the most commonly prescribed glucose-lowering drugs. No clinically relevant interactions are expected during the concomitant use of DOACs and anti-diabetic agents.

Fifty years of research on antithrombotic therapy: Achievements and disappointments

The achievements with antithrombotic therapy over the past 50 years have been monumental and the disappointments relatively few. In this review, we will discuss, chronologically, the major developments of the two recognized classes of antithrombotics - anticoagulants and antiplatelet agents.

Rivaroxaban plus aspirin for cardiovascular protection: Rationale for the vascular dose and dual pathway inhibition

This review provides the rationale for dual pathway inhibition with the combination of low-dose rivaroxaban (2.5 mg twice daily) to attenuate thrombin generation and aspirin (100 mg once daily) to reduce platelet activation. Such therapy has been licensed for secondary prevention in patients with coronary or peripheral artery disease.

Pharmacodynamic Effects of Vorapaxar in Patients With and Without Diabetes Mellitus: Results of the OPTIMUS-5 Study

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Vorapaxar reduces thrombotic cardiovascular events in patients with atherosclerotic disease, with enhanced effects in those with DM.

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Adjunctive vorapaxar therapy reduces platelet-mediated thrombogenicity without affecting clot kinetics in both patients with and those without DM having prior MI/PAD on dual antiplatelet therapy with aspirin and clopidogrel.

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The pharmacodynamic effects of vorapaxar occur via selective blockade of the PAR-1 on the platelet membrane without apparent interplay with other platelet signaling pathways.

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Aspirin withdrawal, which leaves patients on a background of clopidogrel and vorapaxar, increases markers specific to COX-1–mediated blockade, leading to an increase in platelet-mediated global thrombogenicity, particularly among patients with DM.

Vorapaxar reduces thrombotic cardiovascular events at the expense of increased bleeding. However, the differential pharmacodynamic (PD) effects of vorapaxar according to diabetes mellitus (DM) status are unknown. Moreover, although withdrawal of aspirin has emerged as a bleeding reduction strategy, the PD effects of stopping aspirin in patients treated with vorapaxar also are unknown. In this prospective PD investigation, vorapaxar was associated with reduced platelet-mediated thrombogenicity without affecting clot kinetics irrespective of DM status. However, platelet-mediated thrombogenicity increased after aspirin withdrawal, particularly among patients with DM. (Optimizing anti-Platelet Therapy In diabetes MellitUS-5 Study [OPTIMUS-5]; NCT02548650)

Effectiveness and Safety of Standard- and Low-Dose Rivaroxaban in Asians With Atrial Fibrillation

BACKGROUND

Low-dose rivaroxaban (10 mg/day) has been widely used in Asia for patients with atrial fibrillation (AF), although there is a lack of evidence regarding its effectiveness. In Asians, it is unclear whether low-dose rivaroxaban is equally effective as that of the standard dose or is associated with less bleeding risk.

OBJECTIVES

The aim of this study was to evaluate the effectiveness and safety of standard-dose (15 or 20 mg/day) and low-dose (10 mg/day) rivaroxaban in Asians with AF.

METHODS

Using data files from the National Health Insurance Research Database between May 1, 2014, and September 30, 2015, a retrospective population-based cohort study was conducted in patients diagnosed with AF or atrial flutter and treated with low- or standard-dose rivaroxaban. Patients were followed up until the first occurrence of the study outcome or the end of the observation period (December 31, 2015).

RESULTS

Among 6,558 eligible patients, a total of 2,373 and 4,185 patients took low- and standard-dose rivaroxaban, respectively. Compared to standard-dose rivaroxaban, low-dose rivaroxaban was associated with a significantly higher risk of myocardial infarction (subdistribution hazard ratio: 2.26; 95% confidence interval: 1.13 to 4.52), with similar risk of ischemic stroke, systemic embolism, major bleeding, and nonmajor clinically relevant bleeding.

CONCLUSIONS

Compared to standard-dose rivaroxaban, low-dose rivaroxaban in Asian patients with AF was associated with similar risks of thromboembolism and bleeding except myocardial infarction.

Role of oral anticoagulant therapy for secondary prevention in patients with stable atherothrombotic disease manifestations

Coronary artery disease and peripheral arterial disease are strong predictors of risk for a future ischemic event. Despite the utilization of effective secondary prevention strategies, the prevalence of ischemic recurrences remains high, underscoring the need for effective secondary prevention antithrombotic treatment regimens. To date, most of the tested approaches have been with the use of antiplatelet therapies, used either individually or in combination. However, most recent findings support the potential role of oral anticoagulant therapy in addition to antiplatelet therapy to reduce the risk of ischemic recurrences. This approach has been tested in both acute and stable settings of patients with cardiovascular disease manifestations. The present manuscript provides an overview on the rationale and clinical trial updates on the role of oral anticoagulant therapy, in particular rivaroxaban used at the so-called vascular protection dose, in adjunct to antiplatelet therapy (i.e. aspirin), a strategy known as dual pathway inhibition, for secondary prevention of ischemic recurrences in patients with stable atherosclerotic disease manifestations.

ST-segment elevation myocardial infarction

ST-segment elevation myocardial infarction (STEMI) is the most acute manifestation of coronary artery disease and is associated with great morbidity and mortality. A complete thrombotic occlusion developing from an atherosclerotic plaque in an epicardial coronary vessel is the cause of STEMI in the majority of cases. Early diagnosis and immediate reperfusion are the most effective ways to limit myocardial ischaemia and infarct size and thereby reduce the risk of post-STEMI complications and heart failure. Primary percutaneous coronary intervention (PCI) has become the preferred reperfusion strategy in patients with STEMI; if PCI cannot be performed within 120 minutes of STEMI diagnosis, fibrinolysis therapy should be administered to dissolve the occluding thrombus. The initiation of networks to provide around-the-clock cardiac catheterization availability and the generation of standard operating procedures within hospital systems have helped to reduce the time to reperfusion therapy. Together with new advances in antithrombotic therapy and preventive measures, these developments have resulted in a decrease in mortality from STEMI. However, a substantial amount of patients still experience recurrent cardiovascular events after STEMI. New insights have been gained regarding the pathophysiology of STEMI and feed into the development of new treatment strategies.

Safety and Efficacy of Rivaroxaban When Added to Aspirin Monotherapy Among Stabilized Post‐Acute Coronary Syndrome Patients: A Pooled Analysis Study of ATLAS ACS‐TIMI 46 and ATLAS ACS 2‐TIMI 51

Background

A residual risk of ischemic events following an acute coronary syndrome (ACS) remains despite antiplatelet therapy. The addition of an antithrombin as part of a “dual pathway” approach may further improve outcomes as thrombin generation persists for several months post‐ACS. The present study evaluates the safety and efficacy of “dual pathway” therapy (rivaroxaban plus aspirin) as compared with aspirin monotherapy among post‐ACS patients.

Methods and Results

A total of 1477 patients were analyzed in a pooled analysis of subsets of the ATLAS ACS‐TIMI (Anti‐Xa Therapy to Lower cardiovascular events in addition to Aspirin with or without thienopyridine therapy in Subjects with Acute Coronary Syndrome – Thrombolysis in Myocardial Infarction) 46 and ATLAS ACS 2‐TIMI 51 trials including post‐ACS patients receiving aspirin monotherapy and randomized to either rivaroxaban 2.5 mg BID or rivaroxaban 5 mg BID or placebo. The primary efficacy end point was a composite of cardiovascular death, myocardial infarction (MI), or stroke (ischemic, hemorrhagic, or of uncertain cause). The primary safety end point was TIMI‐non‐coronary artery bypass (CABG) major bleeding. The combined rivaroxaban group (2.5 or 5 mg BID) among stabilized post‐ACS patients on a background of aspirin monotherapy was associated with a significant reduction in the primary end point as compared with placebo (hazard ratio=0.65, 95% CI=0.45–0.92, P=0.016). Although the combined rivaroxaban dose groups were associated with higher rates of non‐CABG TIMI major bleeding, the 2.5 mg dose group was not, and the overall number of patients experiencing a non‐CABG TIMI major bleeding event was low (1.5%).

Conclusions

Among patients in the immediate post‐ACS period, a “dual pathway” approach using aspirin and low‐dose rivaroxaban may reduce the risk of secondary atherothrombotic events, but increase bleeding risk.

Clinical Trial Registration

URL: https://www.clinicaltrials.gov. Unique identifiers: NCT00402597; NCT00809965.

See Editorial by Harrison and Newby

Usefulness of Rivaroxaban for Secondary Prevention of Acute Coronary Syndrome in Patients With History of Congestive Heart Failure (from the ATLAS-ACS-2 TIMI-51 Trial)

Patients with both acute coronary syndromes (ACS) and congestive heart failure are at an increased risk of recurrent cardiovascular (CV) events attributed in part to both excess thrombin generation and impaired fibrinolysis. We hypothesized that patients with the overlap of ACS and CHF would thus derive particular benefit from antithrombotic therapy with rivaroxaban. ATLAS-ACS-2 Thrombolysis in Myocardial Infarction-51 was a double-blind, multicenter, phase 3 clinical trial that randomized patients within 7 days of an ACS event to standard of care plus either rivaroxaban 2.5 mg BID, 5 mg BID, or placebo (n = 15,526). In this post hoc subgroup analysis, subjects with a history of CHF at randomization (n = 1,694) were evaluated. Among subjects with a history of CHF, both rivaroxaban doses reduced the primary composite end point of CV death, myocardial infarction, or stroke (2.5 mg BID vs placebo: hazard ratio [HR] 0.59, 95% confidence interval [CI] (0.42, 0.81), p = 0.001; 5 mg BID vs placebo: HR 0.61, 95% CI (0.44, 0.84), p = 0.002; p interaction = 0.006). Both doses of rivaroxaban reduced CV mortality (rivaroxaban 2.5 mg BID vs placebo: 4.1% vs 9.0%, HR 0.45, 95% CI [0.27, 0.74], p = 0.002; rivaroxaban 5 mg BID vs placebo: 5.8% vs 9.0%, HR 0.62, 95% CI [0.40, 0.96], p = 0.031) as well as all-cause mortality. There was no significant increase in noncoronary artery bypass graft-related Thrombolysis in Myocardial Infarction major bleeding with either dose of rivaroxaban as compared with placebo (rivaroxaban 2.5 mg BID = 0.4% vs rivaroxaban 5 mg BID = 1.1% vs placebo = 0.5%). Rivaroxaban also did not increase either intracranial hemorrhage or fatal bleeding. In conclusion, in ACS subjects with a history of CHF, secondary prevention with rivaroxaban reduced the composite of CV death, myocardial infarction, or stroke without an increase in noncoronary artery bypass graft-related major bleeding. These findings require further prospective evaluation in an adequately powered phase 3 study.

Synthesis and in vitro anti-platelet aggregation activities of 2-methoxy-5-arylamido-N-(pyridin-3-yl-methyl)benzamides

In order to discover novel compounds with anti-platelet aggregation activities, a series of novel 2-methoxy-5-arylamido-N-(pyridin-3-ylmethyl)benzamides (1a-n) were synthesized and their anti-platelet aggregation activities were evaluated by the turbidimetric method in response to the following agonists: adenosine diphosphate (ADP) (5 mM/L), arachidonic acid (AA) (20 µM/L), and collagen (1 mg/mL). Those synthesized compounds that have better in vitro activities were subjected to cell toxicity tests via cell counting kit-8 (CCK-8) assay. The biological evaluation revealed that compound 1a (IC₅₀ : 0.21 µM/L) exhibited the highest anti-platelet aggregation activities when ADP was selected as an inducer, and compound 1b (IC₅₀ : 0.23 µM/L) showed the best activities when AA was selected as inducer, and compound 1m (inhibition rate: 55.06%) had significant anti-platelet aggregation activities when collagen was selected as inducer among all target compounds. Moreover, the effect of cell toxicity exhibited that none of the compounds had obvious cell toxicity against L929 cells. Therefore, 2-methoxy-5-arylamido-N-(pyridin-3-ylmethyl)benzamides have the potential to become a novel kind of anti-platelet drugs and deserve further study.

Oral antiplatelet agents in cardiovascular disease

Antiplatelet agents significantly reduce mortality and morbidity in ischemic heart disease, cerebrovascular disease and peripheral artery disease (PAD), and are therefore part of guideline-driven daily medical treatment in these patients. Due to its beneficial effects in the secondary prevention of atherothrombotic events, aspirin remains the most frequently prescribed antiplatelet agent in cardiovascular disease. In patients with acute coronary syndromes (ACS) and in those undergoing angioplasty with stent implantation dual antiplatelet therapy with aspirin and an adenosine diphosphate (ADP) receptor antagonist is indicated. The development of the newer ADP P2Y₁₂ inhibitors prasugrel and ticagrelor has further improved prognosis in ACS patients compared to clopidogrel. Moreover, vorapaxar allows the inhibition of platelet activation by thrombin via protease-activated receptor-1 and has been approved for the use in patients with PAD and in those with a history of myocardial infarction. This review article summarizes the current evidence on oral antiplatelet agents in cardiovascular disease. Keywords: Aspirin, clopidogrel, prasugrel, ticagrelor, vorapaxar, cardiovascular disease.