New agents for DOAC reversal: a practical management review

Bleeding is the commonest and most concerning adverse event associated with anticoagulants. Bleeding, depending on the severity, is managed in various ways, and for severe or life-threatening bleeding, specific antidotes are indicated and recommended. This review provides guidance relating to specific direct oral anticoagulant (DOAC) reversal agents, the antidotes. We discuss their indications for use, dosing, and potential side effects.

Bleeding in cardiac patients prescribed antithrombotic drugs: electronic health record phenotyping algorithms, incidence, trends and prognosis

BACKGROUND

Clinical guidelines and public health authorities lack recommendations on scalable approaches to defining and monitoring the occurrence and severity of bleeding in populations prescribed antithrombotic therapy.

METHODS

We examined linked primary care, hospital admission and death registry electronic health records (CALIBER 1998-2010, England) of patients with newly diagnosed atrial fibrillation, acute myocardial infarction, unstable angina or stable angina with the aim to develop algorithms for bleeding events. Using the developed bleeding phenotypes, Kaplan-Meier plots were used to estimate the incidence of bleeding events and we used Cox regression models to assess the prognosis for all-cause mortality, atherothrombotic events and further bleeding.

RESULTS

We present electronic health record phenotyping algorithms for bleeding based on bleeding diagnosis in primary or hospital care, symptoms, transfusion, surgical procedures and haemoglobin values. In validation of the phenotype, we estimated a positive predictive value of 0.88 (95% CI 0.64, 0.99) for hospitalised bleeding. Amongst 128,815 patients, 27,259 (21.2%) had at least 1 bleeding event, with 5-year risks of bleeding of 29.1%, 21.9%, 25.3% and 23.4% following diagnoses of atrial fibrillation, acute myocardial infarction, unstable angina and stable angina, respectively. Rates of hospitalised bleeding per 1000 patients more than doubled from 1.02 (95% CI 0.83, 1.22) in January 1998 to 2.68 (95% CI 2.49, 2.88) in December 2009 coinciding with the increased rates of antiplatelet and vitamin K antagonist prescribing. Patients with hospitalised bleeding and primary care bleeding, with or without markers of severity, were at increased risk of all-cause mortality and atherothrombotic events compared to those with no bleeding. For example, the hazard ratio for all-cause mortality was 1.98 (95% CI 1.86, 2.11) for primary care bleeding with markers of severity and 1.99 (95% CI 1.92, 2.05) for hospitalised bleeding without markers of severity, compared to patients with no bleeding.

CONCLUSIONS

Electronic health record bleeding phenotyping algorithms offer a scalable approach to monitoring bleeding in the population. Incidence of bleeding has doubled in incidence since 1998, affects one in four cardiovascular disease patients, and is associated with poor prognosis. Efforts are required to tackle this iatrogenic epidemic.

Practical considerations on anticoagulation reversal: spotlight on the reversal of dabigatran

Idarucizumab (Praxbind) is a humanized antibody fragment, that reversibly and with high affinityties up dabigatran (Pradaxa). Anticoagulation reversal is achieved immediately, and with no procoagulant effect. It is administered intravenously and clearance is renal. The main clinical application of idarucizumab is to antagonize bleeding related to dabigatran, especially if it occurs at critical sites, such as nervous system (central or peripheral), intraocular, pericardial, retroperitoneal or pulmonary. Other indications are: i) dabigatran-induced anticoagulation reversal in the need for emergency surgery or procedures at high risk of bleeding; and ii) second-line treatment in bleedings that persist despite local hemostasis procedures. In this narrative review, we comprehensively address clinical indications for idarucizumab, summing up evidence derived from a systematic literature review, but also from case reports.

Use of idarucizumab in reversing dabigatran anticoagulant effect: a critical appraisal

Use of non-vitamin K antagonist oral anticoagulants is spreading in the real world. Despite that, a strong need for antidotes/reversal agents is still reported by several physicians. Idarucizumab is a humanized monoclonal antibody fragment that binds specifically to dabigatran. Idarucizumab was approved in 2015 by the US Food and Drugs Administration and European Medicines Agency for reversal of anticoagulation activity in dabigatrantreated patients. This review briefly summarizes the experimental evidence about effectiveness and safety of idarucizumab. Furthermore, we review the current recommendations and experts' point of view about the use of antidotes/reversal agents in patients reporting a major bleeding event.

Non-vitamin K antagonist oral anticoagulants in patients with an increased risk of bleeding

The non-vitamin K antagonist oral anticoagulants (NOACs) have considerably changed clinical practice and are increasingly being used as an alternative to vitamin K antagonists (VKAs) for 3 main reasons: 1) an improved benefit-risk ratio (in particular lower rates of intracranial bleeding), 2) a more predictable effect without the need for routine monitoring, and 3) fewer food and drug interactions compared with VKAs. Currently, there are four NOACs available: the factor Xa inhibitors apixaban, edoxaban, and rivaroxaban, and the thrombin inhibitor dabigatran. This consensus paper reviews the properties and usage of NOACs in a number of high-risk patient populations, such as patients with chronic kidney disease, patients ≥80 years of age and others and provides guidance for the use of NOACs in patients at risk of bleeding.

A practical guide on how to handle patients with bleeding events while on oral antithrombotic treatment

Bleeding is a feared complication in patients who are treated with antithrombotic therapy (oral anticoagulation or antiplatelet therapy). Management of antithrombotic therapy after bleeding poses a dilemma where restarting the crucial medication could lead to recurrent bleeding, while interrupting or even discontinuing treatment could increase the thrombotic risk. In this review, we provide recommendations regarding the treatment of patients with a bleeding event while on oral antithrombotic therapy, based on the literature and expert opinion.

Andexanet alfa effectively reverses edoxaban anticoagulation effects and associated bleeding in a rabbit acute hemorrhage model

INTRODUCTION

Increasing use of factor Xa (FXa) inhibitors necessitates effective reversal agents to manage bleeding. Andexanet alfa, a novel modified recombinant human FXa, rapidly reverses the anticoagulation effects of direct and indirect FXa inhibitors.

OBJECTIVE

To evaluate the ability of andexanet to reverse anticoagulation in vitro and reduce bleeding in rabbits administered edoxaban.

MATERIALS AND METHODS

In vitro studies characterized the interaction of andexanet with edoxaban and its ability to reverse edoxaban-mediated anti-FXa activity. In a rabbit model of surgically induced, acute hemorrhage, animals received edoxaban vehicle+andexanet vehicle (control), edoxaban (1 mg/kg)+andexanet vehicle, edoxaban+andexanet (75 mg, 5-minute infusion, 20 minutes after edoxaban), or edoxaban vehicle+andexanet prior to injury.

RESULTS

Andexanet bound edoxaban with high affinity similar to FXa. Andexanet rapidly and dose-dependently reversed the effects of edoxaban on FXa activity and coagulation pharmacodynamic parameters in vitro. In edoxaban-anticoagulated rabbits, andexanet reduced anti-FXa activity by 82% (from 548±87 to 100±41 ng/ml; P<0.0001), mean unbound edoxaban plasma concentration by ~80% (from 100±10 to 21±6 ng/ml; P<0.0001), and blood loss by 80% vs. vehicle (adjusted for control, 2.6 vs. 12.9 g; P = 0.003). The reduction in blood loss correlated with the decrease in anti-FXa activity (r = 0.6993, P<0.0001) and unbound edoxaban (r = 0.5951, P = 0.0035).

CONCLUSION

These data demonstrate that andexanet rapidly reversed the anticoagulant effects of edoxaban, suggesting it could be clinically valuable for the management of acute and surgery-related bleeding. Correlation of blood loss with anti-FXa activity supports the use of anti-FXa activity as a biomarker for assessing anticoagulation reversal in clinical trials.

Management of Complications in Anticoagulated Patients with Atrial Fibrillation

Oral anticoagulation is mandatory for patients at high risk of thromboembolism, but the risk of bleeding should also be taken into account. Direct oral anticoagulants are now recommended for non-valvular AF as a potential alternative to warfarin. In this article we discuss methods to assess the anticoagulant effect of these agents, specific and general antidotes, and management of complications such as embolic and haemorrhagic stroke, and significant bleeding.

Time for Practical Clinical Tools

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Safety, pharmacokinetics, and reversal of apixaban anticoagulation with andexanet alfa

Direct factor Xa (FXa) inhibitors lack a specific reversal agent for emergencies such as major bleeding or urgent surgery. Andexanet alfa, a modified, catalytically inactive, recombinant human FXa derivative, reverses anticoagulant effect by binding and sequestering FXa inhibitors. This original report of safety and dose-finding, phase 1 and 2 randomized, double-blind, placebo-controlled studies, investigated various doses of andexanet in healthy volunteers. Phase 1 evaluated the safety and pharmacokinetics of andexanet (n = 24) or placebo (n = 8). In phase 2, andexanet (n = 36) or placebo (n = 18) was administered following steady-state apixaban dosing (5 mg twice daily for 6 days); safety, pharmacokinetics, and pharmacodynamics were assessed. Andexanet plasma concentration increased proportionally with dose, with rapid elimination (terminal elimination half-life, 4.35-7.5 hours). Following apixaban treatment, andexanet rapidly (≤2 minutes) and dose dependently reduced unbound apixaban concentration vs placebo (51% to 89% vs 5% reduction; all P < .05), decreased anti-FXa activity (67.8% to 95.0% vs 7.1% reduction; all P < .05), and restored thrombin generation in 67% to 100% vs 6% of subjects (all P < .01), maintaining these effects during continuous 45- and 120-minute infusions. Andexanet was well tolerated. Nine subjects had mild/moderate infusion reactions not associated with hemodynamic changes or respiratory compromise that generally resolved without intervention or dose reduction. There were no thrombotic events or other serious safety issues. In conclusion, andexanet reversed apixaban-mediated effects on pharmacodynamic markers of anticoagulation in healthy volunteers within minutes after administration and for the duration of infusion. This trial was registered at www.clinicaltrials.gov as #NCT01758432.

New Oral Anticoagulants and Their Reversal Agents

OPINION STATEMENT

Direct oral anticoagulants (DOAC) are an attractive therapeutic option for anticoagulant treatment in the setting of venous thromboembolism or non-valvular atrial fibrillation. These drugs overall appear to have a lower risk of life-threatening hemorrhage than the vitamin K antagonists. In addition, they demonstrate more predictable and stable pharmacokinetics. Measurement of the degree of anticoagulation is desirable in patients with DOAC-associated hemorrhage, but commonly available coagulation assays show poor sensitivity for degree of DOAC effect. DOAC-specific tests are time consuming and not widely available. All coagulation tests should be interpreted considering the timing of last intake and renal function. When life-threatening bleeding occurs, hemostasis should be restored as rapidly as possible. Non-specific prohemostatic drugs may have a role in DOAC reversal, and specific antidotes are at different stages of development. In this review, we provide a summary of DOAC characteristics and an overview of the different therapeutic options available for DOAC reversal.

Non-Vitamin K Oral Anticoagulants in Stroke Patients: Practical Issues

Non-vitamin-K oral anticoagulants (NOACs) represent a major advance in the prevention of stroke in patients with atrial fibrillation (AF), offering a similar, if not superior, efficacy and safety profile and several practical advantages over oral vitamin K antagonists (VKAs). The rapid onset of action of the NOACs, their relatively short half-live, and the availability of specific reversal agents may be advantageous when managing acute ischemic strokes, and in the post-stroke, post-transient ischemic attack, and post-intracranial hemorrhage settings. In this review article, we offer practical guidance on the use of NOACs in these settings, focusing on managing the acute event and on initiating or resuming anticoagulation for secondary prevention. We also assess the use of NOACs to prevent stroke and bleeding in patients with AF who have chronic kidney disease, are elderly, or cognitively impaired, and we offer guidance on optimizing the use of NOACs and VKAs in these patient groups in the absence of evidence-based guidelines.

Edoxaban in venous thromboembolism and stroke prevention: an appraisal

Oral anticoagulation is the therapeutic cornerstone in preventing thromboembolic risk in both atrial fibrillation (AF) and venous thromboembolism (VTE). After decades of the sole therapeutic oral anticoagulation option being warfarin, the introduction of non-vitamin K antagonist oral anticoagulants has heralded a new era. Edoxaban is the latest addition to these available for clinical use. Edoxaban was as effective and safer than warfarin in preventing thromboembolic risk in AF patients. Similarly, edoxaban effectiveness and safety was evident when treating VTE patients to prevent recurrent VTE or VTE-related death. Therefore, edoxaban represents a valuable alternative in treating thromboembolic risk for AF and VTE patients.