Randomized, Double-Blind, Dose-Ranging Study of Otamixaban, a Novel, Parenteral, Short-Acting Direct Factor Xa Inhibitor, in Percutaneous Coronary Intervention

Biomarkers of coagulation and fibrinolysis in acute myocardial infarction: a joint position paper of the Association for Acute CardioVascular Care and the European Society of Cardiology Working Group on Thrombosis

The formation of a thrombus in an epicardial artery may result in an acute myocardial infarction (AMI). Despite major advances in acute treatment using network approaches to allocate patients to timely reperfusion and optimal antithrombotic treatment, patients remain at high risk for thrombotic complications. Ongoing activation of the coagulation system as well as thrombin-mediated platelet activation may both play a crucial role in this context. Whether measurement of circulating biomarkers of coagulation and fibrinolysis could be useful for risk stratification in secondary prevention is currently not fully understood. In addition, measurement of such biomarkers could be helpful to identify thrombus formation as the leading mechanism for AMI. The introduction of biomarkers of myocardial injury such as high-sensitivity cardiac troponins made rule-out of AMI even more precise. However, elevated markers of myocardial injury cannot provide proof of a type 1 AMI, let alone thrombus formation. The combined measurement of markers of myocardial injury with biomarkers reflecting ongoing thrombus formation might be helpful for the fast and correct diagnosis of an atherothrombotic type 1 AMI. This position paper gives an overview of the current knowledge and possible role of biomarkers of coagulation and fibrinolysis for the diagnosis of AMI, risk stratification, and individualized treatment strategies in patients with AMI.

Novel oral anticoagulants for acute coronary syndrome

Acute coronary syndrome (ACS) is a cardiovascular condition with a multifactorial pathophysiology that includes atherosclerotic plaques, platelet activation and thrombin production, among others. Thrombin production and the prothrombotic state of ACS patients have provided a role for anticoagulants to treat patients during the acute event and has led to subsequent research for the post-acute state. Warfarin has an indication for ACS, however, it is restricted to specific patients and many factors limit its use. Therefore, novel oral anticoagulants (NOACs) are being explored for ACS. Limitations for the use of NOACs in ACS are centered on the increased risk of bleeding that occurs when these agents are added to the current standard of care with dual antiplatelet therapy. Rivaroxaban is the only NOAC that has achieved approval in Europe for this indication with none of the NOAC currently approved in the US for use in ACS. Ongoing studies for rivaroxaban and apixaban may provide evidence to further clarify the place in therapy for NOAC agents in ACS management.

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.

Contemporary anticoagulation therapy in patients undergoing percutaneous intervention

The proper use of anticoagulants is crucial for ensuring optimal patient outcomes post percutaneous interventions in the cardiac catheterization laboratory. Anticoagulant agents such as unfractionated heparin, a thrombin inhibitor; low-molecular weight heparins, predominantly Factor Xa inhibitors; fondaparinux, a Factor Xa inhibitor and bivalirudin, a direct thrombin inhibitor have been developed to target various steps in the coagulation cascade to prevent formation of thrombin. Optimal anticoagulation achieves the correct balance between thrombosis and bleeding and is related to optimal outcomes with minimal complications. This review will discuss the mechanisms and appropriate use of current and emerging anticoagulant therapies used during percutaneous interventions.

Role of novel and emerging oral anticoagulants for secondary prevention of acute coronary syndromes

Dual antiplatelet therapy has become a mainstay of long-term management of patients after an acute coronary syndrome (ACS). Mortality for these patients remains high despite current evidence-based treatment strategies. The coagulation cascade plays a role in the pathophysiology of ACS, and trials with warfarin in combination with dual antiplatelet therapy have found decreased rates of ischemic events at the expense of increased bleeding risk. Novel oral anticoagulants (NOACs) in the direct factor Xa (FXa) inhibitor and direct thrombin inhibitor (DTI) categories have been evaluated in combination with standard post-ACS therapy. Rivaroxaban, a FXa inhibitor, reduced the rates of ischemic events but increased major bleeding rates. Apixaban did not decrease the rates of ischemic events and also increased major bleeding rates. Other FXa inhibitors have not been studied in the long-term management of ACS (e.g., otamixaban), are not currently being studied in ongoing phase III trials (e.g., TAK-442), or have been discontinued by the manufacturer (e.g., darexaban). The DTI dabigatran had a 2- to 4-fold increased risk of major bleeding with unclear benefit for reducing ischemic events. The factor IXa inhibitor pegnivacogin is an RNA-based aptamer that has been studied in patients undergoing cardiac catheterization but has not been studied for long-term post-ACS management. The European Society of Cardiology Working Group on Thrombosis recommends the use of newer antiplatelet agents over addition of NOACs. Additional guidelines are available to guide management in patients requiring triple antithrombotic therapy but do not provide definitive recommendations on NOACs. Many questions remain about the place of NOACs for long-term post-ACS management. Recent trials have evaluated double versus triple antithrombotic therapy to balance efficacy and bleeding risk, but they did not include NOACs. It also remains unclear if NOACs hold a place in post-ACS therapy in the era of more potent antiplatelet agents such as prasugrel and ticagrelor.

New oral anticoagulants after acute coronary syndrome

New oral anticoagulants (NOACs) have been developed that may further decrease the mortality and morbidity of ACS by complementing antiplatelet therapy. Optimal use of these agents can be achieved by maximum reduction in thrombotic events at the minimum bleeding risk when combining a long-term oral anticoagulant with anti-platelet therapy in patients with coronary heart disease. Although, based on the pharmacokinetics and -dynamics of NOACs, these agents could improve the current management of ACS patients, multiple trials consistently demonstrate a trend toward increased major and clinically relevant non major bleeding almost diminishing the benefits in reduction of ischemic events. Therefore, some critical issues need to be further evaluated in future trials.

Investigational anticoagulants for hematological conditions: a new generation of therapies

INTRODUCTION

The introduction of novel anticoagulants has had contrasting effects on the agents in the pipeline, fueling the development of some and sinking the others. The complexity of the coagulation cascade offers interesting inhibition choices that might become valid treatment options.

AREAS COVERED

This review will highlight some of the anticoagulants in the pipeline. Following the success of the direct thrombin and FXa inhibitors already in the market, new agents are being tested. These include AZD0837, betrixaban, letaxaban, darexaban, and LY517717. Targeting other components of the hemostatic pathway might lead to better safety profiles without influencing efficacy. Inhibitors to FVIIa-tissue factor (FVIIa/TF) complex, FIX, FXI, and FXII are being assessed. New inspiring inhibitors are antisense oligonucleotides (ASOs) and aptamers. These are highly specific agents with readily reversible effect and might be engineered to inhibit any coagulation factor. Currently tested ASOs and aptamers are inhibitors of FXI, FXII, thrombin, FIXa, and platelet GPIV.

EXPERT OPINION

Some of the agents in the pipeline offer valid treatment option for long-term therapy, overcoming some of the drawbacks of the novel anticoagulants. Research is being driven by an expanding market in the anticoagulation field that has been unexploited for a long time.

Design and rationale of the treatment of acute coronary syndromes with otamixaban trial: a double-blind triple-dummy 2-stage randomized trial comparing otamixaban to unfractionated heparin and eptifibatide in non-ST-segment elevation acute coronary syndromes with a planned early invasive strategy

BACKGROUND

Otamixaban is a synthetic intravenous direct factor Xa inhibitor, with rapid onset/offset, linear kinetics, and no significant renal elimination. A phase II trial in acute coronary syndromes (ACS) showed a marked reduction in the combined end point of death or myocardial infarction (MI) and similar bleeding rates with otamixaban at midrange doses, compared with unfractionated heparin (UFH) and eptifibatide.

DESIGN

The TAO trial is a phase III, randomized, double-blind, triple-dummy controlled trial testing the efficacy of otamixaban over UFH plus eptifibatide in patients with non-ST-segment elevation ACS to be treated with dual oral antiplatelet therapy and an invasive strategy. Approximately 13,220 patients in 55 countries will be randomized (1:1:1 ratio) to receive UFH plus downstream eptifibatide (started pre-percutaneous coronary intervention and continued per label) or otamixaban (0.08 mg/kg intravenous bolus at randomization then 0.100 or 0.140 mg/kg per hour intravenous infusion). An interim analysis was performed after ≥1,969 patients per arm completed 7 days of follow-up and the Data Monitoring Committee selected 1 otamixaban dose (blinded to investigators) to be carried forward using a prespecified algorithm. The primary efficacy outcome is the composite of all-cause mortality or new MI through day 7. The primary safety outcome is thrombolysis in MI major or minor bleeding through day 7. Secondary outcomes include all-cause mortality, recurrent ischemia/infarction resulting in prolonged/recurrent hospitalization, periprocedural angiographic complications, and pharmacokinetic data in 6,000 patients.

CONCLUSIONS

The TAO trial will assess the clinical efficacy and safety of otamixaban in non-ST-segment elevation ACS with planned invasive strategy.

Appropriate anti-thrombotic/anti-thrombin therapy for thrombotic lesions

Managing coronary thrombus is a challenging task and requires adequate knowledge of the various antithrombotic agents available. In this article, we will briefly analyze the risk-benefit profile of antithrombotic agents, with critical analysis of the scientific evidence available to support their use. Since thrombus consists of platelets and coagulation cofactors, an effective antithrombotic strategy involves using one anticoagulant with two or more antiplatelet agents. Unfractionated heparin traditionally has been the most commonly used anticoagulant but is fast being replaced by relatively newer agents like LMWH, direct thrombin inhibitors, and Factor Xa inhibitors.

In recent years, the antiplatelet landscape has changed significantly with the availability of more potent and rapidly acting agents, like prasugrel and ticagrelor. These agents have demonstrated a sizeable reduction in ischemic outcomes in patients with ACS, who are treated invasively or otherwise, with some concern for an increased bleeding risk. Glycoprotein IIb/IIIa inhibitors have an established role in high risk NSTE ACS patients pretreated with dual antiplatelets, but its role in STEMI patients, treated with invasive approach and dual antiplatelets, has not been supported consistently across the studies. Additionally, in recent years, its place as a directly injected therapy into coronaries has been looked into with mixed results. In conclusion, a well-tailored antithrombotic strategy requires taking into account each patient’s individual risk factors and clinical presentation, with an effort to strike balance between not only preventing ischemic outcomes but also reducing bleeding complications.

New antithrombotic drugs: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines

This article focuses on new antithrombotic drugs that are in or are entering phase 3 clinical testing. Development of these new agents was prompted by the limitations of existing antiplatelet, anticoagulant, or fibrinolytic drugs. Addressing these unmet needs, this article (1) outlines the rationale for development of new antithrombotic agents; (2) describes the new antiplatelet, anticoagulant, and fibrinolytic drugs; and (3) provides clinical perspectives on the opportunities and challenges faced by these novel agents.

New anticoagulants - promising and failed developments

New direct and indirect acting factor Xa (FXa) and thrombin inhibitors are being developed to overcome the downsides of the conventional anticoagulants - unfractionated and low molecular weight heparins and vitamin K antagonists. Ximelagatran and idraparinux failed to demonstrate an acceptable safety profile. Rivaroxaban and dabigatran are approved for the post-operative prevention of thromboembolic complications after elective hip or knee replacement surgery; dabigatran is approved for the prevention of embolism in patients with atrial fibrillation in an increasing number of countries. Several novel indirect antithrombin-dependent anticoagulants as well as antithrombin-independent oral direct FXa and thrombin inhibitors are investigated in multiple indications for the prophylaxis and treatment of venous thromboembolism and the prophylaxis of arterial thrombotic disorders. Quality-adjusted life years costs and incremental cost-effectiveness ratios are relatively high at present, but may decrease after approval of more new anticoagulants for additional indications.

Novel Oral Anticoagulation in Management of Venous Thromboembolism, Atrial Fibrillation, and Acute Coronary Syndrome

Venous thromboembolism (VTE) is a major public health concern since the incidence of VTE rises substantially with age. Furthermore, the diagnosis can be elusive since patients can present differently, causing delay in diagnosis and initiation of treatment and resulting in major morbidity and mortality. In addition to accuracy and precision in diagnosis, antithrombotic therapies are the cornerstones of VTE management. In traditional paradigm, vitamin K antagonists (warfarin), indirect factor Xa inhibitors, and heparin are the foundation in management of VTE. Warfarin has been the only available oral anticoagulant therapy for several decades. Although warfarin is effective in both treatment and prophylaxis against VTE, there are several limitations. Therefore, the novel anticoagulation therapies, including rivaroxaban, apixaban, and dabigatran etexilate, have apparent advantages over warfarin in terms of clinical efficacy and adverse effects. The objective of this review is to describe the background and clinical implications of these novel anticoagulants.

New and emerging anticoagulant therapy for atrial fibrillation and acute coronary syndrome

Abstract Thrombosis is an underlying cause of many cardiovascular disorders, and generation of thrombi in the arterial circulation can lead to unstable angina, myocardial infarction, or ischemic stroke. Antithrombotic therapy is widely used, with proven benefit to prevent ischemic stroke and thromboembolic events in patients with atrial fibrillation (AF) or to prevent further ischemic complications in patients with acute coronary syndrome (ACS). Traditional anticoagulants (including unfractionated heparin, low-molecular-weight heparin, and warfarin) and antiplatelet agents (including aspirin, clopidogrel, and prasugrel) are typically used for these indications. Limitations to their use include variable pharmacokinetic and pharmacodynamic profiles, inability to inhibit fibrin-bound thrombin, risk of heparin-induced thrombocytopenia, delayed onset of action, numerous drug interactions, need for substantial laboratory monitoring and dosage titrations, hyporesponsiveness or resistance, hypersensitivity, adverse events, and bleeding. To overcome some of the limitations of traditional agents, new antithrombotic agents under development are highly selective for specific coagulation factors blocking the synthesis of thrombin. Clinicians must have an understanding of the new anticoagulants to aid in the selection of appropriate therapies for patients. We describe the most relevant phases II and III clinical trials that evaluated several recent emerging anticoagulant drugs for use in patients with AF or ACS. The advantages of many new agents include predictable pharmaco-dynamic response and pharmacokinetic parameters, allowing for fixed oral dosing with no need for laboratory monitoring. For patients with AF, dabigatran is already approved for the prevention of stroke and systemic embolism, rivaroxaban appears to be an effective alternative to warfarin in high-risk patients, and apixaban may also be an effective alternative to aspirin in patients unable to take warfarin. Otamixaban shows promise as an intravenous alternative for patients with ACS in the acute care setting. Likewise, rivaroxaban, dabigatran, and darexaban with or without dual antiplatelet therapy may be beneficial for secondary prevention of ischemic events in patients with ACS.

A medicinal chemistry perspective on structure-based drug design and development

The application of X-ray crystallography and molecular modeling can provide valuable insight into the optimization of the molecular interactions of a drug-protein complex to achieve potency and selectivity of a drug candidate. For the successful application of SBDD in a drug development program, the impact of these structural modifications required to improve potency and selectivity must be considered in the context of balancing of a multitude of drug properties and other considerations that include solubility, bioavailability, metabolism, distribution, toxicology, chemical stability, and intellectual property space. The utility of structure-based design from the medicinal chemist's perspective is described in this chapter.

Emerging therapies for acute coronary syndromes

In the majority of cases acute coronary syndromes (ACS) are caused by activation and aggregation of platelets and subsequent thrombus formation leading to a decrease in coronary artery blood flow. Recent focus on the treatment of ACS has centered on reducing the response of platelets to vascular injury as well as inhibiting fibrin deposition. Novel therapies include more effective P2Y12 receptor blockers thereby reducing inter-individual variability, targeting the platelet thrombin receptor (protease activated receptor 1) as well as directly inhibiting factor Xa or thrombin activity. In this review we discuss the clinical data evaluating the effectiveness of these various new ACS treatment options.

Clinical pharmacology of direct and indirect factor Xa inhibitors

The limitations of conventional anticoagulants have stimulated the development of new anticoagulants. The central position of factor Xa (FXa) at the junction of the intrinsic and extrinsic pathways in the coagulation cascade means that direct and indirect FXa inhibitors have increasingly changed antithrombotic strategies. FXa inhibitors potently and selectively inhibit thrombin formation rather than thrombin activity. Direct FXa inhibitors may directly bind to FXa, whereas indirect inhibitors are dependent on antithrombin. Direct inhibitors may bind free FXa and, in contrast to indirect inhibitors, FXa within the prothrombinase complex or within clots as well. Fondaparinux is the prototype indirect FXa inhibitor and has been extensively studied in the prevention and treatment of thromboembolic diseases, including acute coronary syndromes. Due to a favourable efficacy and safety profile and convenient once-daily dosing without the need for monitoring, fondaparinux is preferentially recommended in recent guidelines dealing with antithrombotic treatment. A number of small-molecule direct FXa inhibitors are currently at different stages of clinical development. After an extensive clinical trial programme demonstrating superior efficacy without a significant increase in major bleeds compared with enoxaparin, rivaroxaban is now available for the prevention of thromboembolic events in patients undergoing orthopaedic surgery. Rivaroxaban also offers the convenience of oral once-daily dosing without the need for monitoring. Whereas most direct FXa inhibitors are orally active, otamixaban is administered intravenously, offering rapid on-off anticoagulant activity. Other compounds under development may offer additional options for tailored antithrombotic strategies according to differing indications, clinical situations and patient variables.

Novel oral anticoagulants for prophylaxis and treatment of venous thromboembolism: part I (Factor Xa inhibitors)

The quest for an ideal anticoagulant is ongoing. Oral agents that do not require blood level monitoring are presently undergoing taut scrutiny for efficacies and potential side effects, and would potentially soon revolutionize coagulation medicine. The first part of this article reviews oral Factor Xa inhibitors, such as rivaroxaban, apixaban, eribaxaban, edoxaban and YM150--exploring the outcomes of major clinical trials for prophylaxis and treatment of venous thromboembolism--and also briefly outlining their pharmacological properties. The second part of the article (in a separate issue) will cover oral Factor IIa (thrombin), such as dabigatran and AZD0837 and oral Factor IX inhibitors, such as TTP889.

The optimal pharmacological formula for percutaneous coronary intervention

INTRODUCTION

Adjunctive pharmacotherapy is of key importance in determining the outcomes of percutaneous coronary intervention (PCI). In parallel, there has been an increasing body of evidence indicating that the aggressive management of coronary risk factors and changes in lifestyle behavior yield additional positive results in morbidity and mortality reductions. A stream of new data from randomized clinical trials has recently prompted the release of a focused update of the PCI guidelines, endorsing new recommendations on the use of antiplatelet drugs and parenteral anticoagulants.

AREAS COVERED

The aim of this manuscript is to provide an up-to-date overview of the current evidence on the use of adjunctive pharmacological therapy in patients undergoing revascularization, with focus on results of recent trials and future directions.

EXPERT OPINION

Given the availability of several pharmacological agents with different mechanisms of action, understanding whether a drug should or should not be prescribed, as well as individualizing the pharmacological formula to the patient's need and risk category, is pivotal to balance the safety and efficacy of adjunctive therapies for PCI. Studies on new antiplatelet agents and selective inhibitors of specific coagulation factors are likely to characterize the next years of research on interventional pharmacology.

Factor Xa inhibitors for acute coronary syndromes

BACKGROUND

The activation of coagulation mechanisms plays a central role in the pathogenesis of acute coronary syndromes (ACS). Administration of unfractionated heparin (UFH) and low molecular weight heparins (LMWH), agents preventing the progression of thrombus formation, is a crucial therapeutic strategy. However, some limitations related to their use have recently stimulated the development of new synthetic agents.

OBJECTIVES

To evaluate the clinical efficacy and safety of factor Xa inhibitors for treatment of ACS compared to UFH or LMWH.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) of the Cochrane Library (Issue 1, 2008), PubMed, EMBASE and LILACS as well as the publications from International Congresses and the reference lists of the selected studies in December 2008.

SELECTION CRITERIA

We used randomized controlled trials (RCTs) comparing factor Xa inhibitors to UFH or LMWH during the course of ACS. Outcome measures included all-cause mortality, myocardial infarction, re-infarction, ischemia recurrence, and adverse events.

DATA COLLECTION AND ANALYSIS

The selection, quality assessment and data extraction of the included trials were done independently by two authors and disagreements were resolved by consensus. Data were analysed by the use of risk ratio (RR) with 95% confidence interval (CI), and the numbers needed to treat (NNT) were reported as needed.

MAIN RESULTS

A total of four RCTs involving 27,976 subjects were included. Fondaparinux was the only factor Xa inhibitor identified in our included RCTs. Fondaparinux appeared to be related to a lower risk in all-cause mortality at 90 to 180 days (RR 0.89; 95% CI 0.81 to 0.97), especially in the group where enoxaparin (a LMWH) was the control drug. Fondaparinux was also associated with a lower risk in major and minor bleeding at 30 days compared to enoxaparin (RR 0.63, 95% CI 0.55 to 0.73; RR 0.34, 95% CI 0.28 to 0.43, respectively), but not when compared to UFHs (RR 1.41; 95% CI 0.49 to 4.10; RR 0.70, 95% CI 0.14 to 3.39 respectively).

AUTHORS' CONCLUSIONS

The therapeutic efficacy of factor Xa inhibitors in ACS seemed to be related to a reduced risk in all-cause mortality at 90 to 180 days, with a better safety profile than enoxaparin in terms of reduce incidence of major and minor bleeding.

New parenteral anticoagulants in development

The therapeutic armamentarium of parenteral anticoagulants available to clinicians is mainly composed by unfractionated heparin (UFH), low-molecular-weight heparin (LMWH), fondaparinux, recombinant hirudins (i.e. bivalirudin, desirudin, lepirudin) and argatroban. These drugs are effective and safe for prevention and/or treatment of thromboembolic diseases but they have some drawbacks. Among other inconveniences, UFH requires regular anticoagulant monitoring as a result of variability in the anticoagulant response and there is a risk of serious heparin-induced thrombocytopaenia (HIT). LMWH, fondaparinux and recombinant hirudins are mainly cleared through the kidneys and their use in patients with severe renal insufficiency may be problematic. LMWH is only partially neutralized by protamine while fondaparinux and recombinant hirudins have no specific antidote. Novel anticoagulants in development for parenteral administration include new indirect activated factor Xa (FXa) inhibitors (idrabiotaparinux, ultra-low-molecular-weight heparins [semuloparin, RO-14], new LMWH [M118]), direct FXa inhibitors (otamixaban), direct FIIa inhibitors (flovagatran sodium, pegmusirudin, NU172, HD1-22), direct FXIa inhibitors (BMS-262084, antisense oligonucleotides targeting FXIa, clavatadine), direct FIXa inhibitors (RB-006), FVIIIa inhibitors (TB-402), FVIIa/tissue factor inhibitors (tifacogin, NAPc2, PCI-27483, BMS-593214), FVa inhibitors (drotrecogin alpha activated, ART-123) and dual thrombin/FXa inhibitors (EP217609, tanogitran). These new compounds have the potential to complement established parenteral anticoagulants. In the present review, we discuss the pharmacology of new parenteral anticoagulants, the results of clinical studies, the newly planned or ongoing clinical trials with these compounds, and their potential advantages and drawbacks over existing therapies.

Prothrombin fragments in cardiovascular disease

Prothrombin fragment 1+2 (F1+2), which comes from in vivo cleavage of prothrombin by factor Xa, is considered to be useful for diagnosis of thrombosis. Recognition of the central role of thrombosis in the pathogenesis ofcardiovascular disease has prompted growing interest in the association o F1+2 with cardiovascular clinical syndromes. Increased F1+2 levels have reported in venous thromboembolism, inflammation, cancer, sepsis, acute coronary syndromes, stroke, peripheral arterial disease, atrial fibrillation and during the postoperative period. However, a clear relationship with the appearance of thrombosis has not always been consistently demonstrated. Besides its potential prognostic and diagnostic value, it could also be usefu in assessing the impact of various therapies. However, it should be kept in mind that measurement of hemostasis activation markers has several important biological and methodological disadvantages. Activation markers reflect the presence of thrombosis in any vascular bed, so they are not specific. Furthermore, elevations occur not only in the presence of overt thrombosis but also during the hypercoagulable state. The cutoff level to be used for the definition of elevations is still largely unknown due to the use of different analytical methods, none of which have been standardized until know. Finally, the prognostic value of F1+2 and other markers of coagulation activation remains to be fully defined in future studies.

ISAR-REACT 3A: a study of reduced dose of unfractionated heparin in biomarker negative patients undergoing percutaneous coronary intervention

AIMS

Although a 140 U/kg dose of unfractionated heparin (UFH) was comparable with bivalirudin in terms of net clinical outcome in the Intracoronary Stenting and Antithrombotic Regimen: Rapid Early Action for Coronary Treatment (ISAR-REACT) 3 trial, it was associated with a higher risk of bleeding. We designed this study to assess whether a reduction in the UFH dose from 140 to 100 U/kg is associated with improved net clinical outcome.

METHODS AND RESULTS

A total of 2505 biomarker negative patients undergoing percutaneous coronary intervention (PCI) after clopidogrel pre-treatment received a single bolus of 100 U/kg UFH. The primary endpoint was net clinical outcome-a quadruple endpoint of death, myocardial infarction, urgent target-vessel revascularization within 30 days, or in-hospital REPLACE 2 defined major bleeding. The primary comparison was with the historical UFH group of ISAR-REACT 3 (2281 patients). In a second analysis, we checked for non-inferiority against the historical bivalirudin arm of ISAR-REACT 3 (2289 patients). The incidence of the primary endpoint was 7.3% in the lower UFH dose group compared with 8.7% in the higher UFH dose group [hazard ratio (HR) 0.81; 95% confidence interval (CI) 0.67-1.00; P = 0.045]. The incidence of major bleeding was 3.6% in the lower UFH dose group and 4.6% in the higher UFH dose group (HR 0.79; 95% CI 0.59-1.05; P = 0.11). The lower UFH dose met the criterion of non-inferiority compared with bivalirudin (P < 0.001).

CONCLUSION

In biomarker negative patients undergoing PCI after clopidogrel loading, a reduced dose of 100 U/kg UFH provided net clinical benefit compared with the historical control of 140 U/kg UFH in the ISAR-REACT 3 trial. The benefit was mostly driven by reduction in bleeding.

CLINICAL TRIAL REGISTRATION INFORMATION

URL www.clinicaltrials.gov; Unique identifier NCT00735280.

The thrombin hypothesis in ACS: a disappointing disconnect between bench data and bedside clinical trials

Studies have demonstrated the efficacy and safety of unfractionated heparin and low-molecular-weight heparin in the management of patients with acute coronary syndrome. However, a common limitation of unfractionated heparin and low-molecular-weight heparin is that neither can neutralize clot-bound thrombin. To overcome this limitation of the broad heparin-based anticoagulants, novel anticoagulants targeted for both the free and clot-bound forms of thrombin (direct thrombin inhibitors), or other individual components of the coagulation cascade (eg, direct and indirect factor Xa inhibitors), were developed. These targeted anticoagulation agents showed promising results in preclinical testing and have been evaluated in large-scale clinical acute coronary syndrome trials. This review discusses the disconnect between the excellent preclinical findings obtained with these novel, targeted agents and the efficacy and safety data observed in patients with acute coronary syndrome, compared with the broader-range heparin-based anticoagulants.

Emerging drugs for acute myocardial infarction

IMPORTANCE OF THE FIELD

The present review is aimed at going over the pharmacological profile (and the clinical impact) of the emerging drugs involved in the management of patients with ST-elevation myocardial infarction (STEMI) in order to provide the cardiologists who deal with these patients in the early phase with the most recent evidence on this topic.

AREAS COVERED IN THIS REVIEW

Anticoagulant and antiplatelet drugs are the main cornerstones of therapy in the treatment of STEMI patients undergoing primary percutaneous coronary intervention (PCI). The main issues that clinicians have to deal with are represented by balancing thrombotic and bleeding risks. In tailoring therapy, variables such as age, sex and previous disease should be taken into account, as well as ongoing complications (such as acute renal failure) that could affect hemostasis. Despite the well-established clinical benefits of antiplatelet agents, questions remain, mainly surrounding potential for variable platelet response, which are strictly related to non-genetic (i.e., diet, drug-drug interaction, clinical factors such as obesity, diabetes mellitus, and inflammation) and genetic determinants.

WHAT THE READER WILL GAIN

In their daily practice, cardiologists cannot abstract from the knowledge and updating on the ongoing research fields as well as the newly developed drugs, which they should frame in the very patient in the attempt to the develop a personalized medical strategy. These include also the pharmacological option(s) in the treatment of the reperfusion injury, the metabolic aspects and the stem cell therapy. TAKE HOME MASSAGE: In our opinion, the goal of ongoing research on the pharmacological approach to STEMI patients is a personalized medical strategy that relies on critical clinicians who merge newly developed acquisitions on this topic and a more complete, systemic and critical approach to the patient.

Catheter thrombosis and percutaneous coronary intervention: fundamental perspectives on blood, artificial surfaces and antithrombotic drugs

Recent reports of catheter thrombosis among patients undergoing percutaneous coronary intervention (PCI) have had a significant impact on the development of new antithrombotic therapies. The overall incidence of this complication is unknown, mainly because of underreporting in contemporary clinical trials of coronary intervention. The etiology and pathophysiology of catheter thrombosis is also poorly understood. Introduction of a catheter or guidewire may not provoke the intense thrombotic response that follows angioplasty or stenting, but factors such as catheter materials and device size, equipment surface properties, flow conditions, procedural time and complexity, as well as the antiplatelet and anticoagulant drugs administered during the procedure influence the likelihood, rate and clinical impact of thrombosis. The crucial role of cellular interactions involving tissue-factor bearing cells and platelets in the process of thrombosis also needs to be critically explored when considering blood contact with an exogenous material. Focusing on the inherently prothrombotic environment of percutaneous coronary intervention, we review the physiologic underpinnings of catheter and guidewire thrombosis, and explore the effect of antithrombotic drugs at the interface between blood and material surfaces. We also propose a clinical classification for the diagnosis and investigation of catheter thrombosis in clinical trials of anticoagulant therapy and PCI.

Antithrombotics in acute coronary syndromes

Antithrombotic agents are an integral component of the medical regimens and interventional strategies currently recommended to reduce thrombotic complications in patients with acute coronary syndromes (ACS). Despite great advances with these therapies, associated high risks for thrombosis and hemorrhage remain as the result of complex interactions involving patient comorbidities, drug combinations, multifaceted dosing adjustments, and the intricacies of the care environment. As such, the optimal combinations of antithrombotic therapies, their timing, and appropriate targeted subgroups remain the focus of intense research. During the last several years a number of new antithrombotic treatments have been introduced, and new data regarding established therapies have come to light. Although treatment guidelines include the most current available data, subsequent findings can be challenging to integrate. This challenge is compounded by the complexity associated with different efficacy and safety measures and the variability in study populations, presenting syndromes, physician, and patient preferences. In this work we review recent data regarding clinically available antiplatelet and anticoagulation agents used in the treatment of patients with ACS. We address issues including relative efficacy, safety, and timing of therapies with respect to conservative and invasive treatment strategies. In specific cases we will highlight remaining questions and controversies and ongoing trials, which will hopefully shed light in these areas. In addition to reviewing existing agents, we take a look forward at the most promising new antithrombotics currently in late-stage clinical development and their potential role in the context of ACS management.

Novel anticoagulants in clinical development: focus on factor Xa and direct thrombin inhibitors

Vitamin K antagonists are the mainstay in the prevention and treatment of thromboembolic diseases. Although effective under optimal conditions, several drawbacks are imminent to the long-term application of these drugs due to their narrow therapeutic window, interactions with other drugs as well as the need for regular monitoring and the risk of a recurrent event versus the risk of bleeding. To overcome these downsides, novel anticoagulants are being developed; in contrast to vitamin K antagonists, these novel agents specifically and selectively block central elements of the coagulation cascade. Several clinical trials have demonstrated the efficacy and safety of selective FXa inhibitors (such as fondaparinux, rivaroxaban, apixaban) and direct thrombin inhibitors (such as lepirudin, bivalirudin, dabigatran etexilate) in the treatment of typical indications for conventional vitamin K antagonists, in particular, the prevention and treatment of venous thromboembolism. This review summarizes the results and designs of recently published and ongoing clinical trials of novel anticoagulants.