Reversal Agents in Development for the New Oral Anticoagulants

Role of Direct Oral Anticoagulation Agents as Thromboprophylaxis in Antiphospholipid Syndrome

Antiphospholipid syndrome (APS) is an autoimmune disorder that causes venous, arterial and small-vessel thrombosis, pregnancy loss, and premature birth. Cardiac valvular disease, renal thrombotic microangiopathy, thrombocytopenia, hemolytic anemia, and cognitive impairment are some of its other clinical symptoms. Antiphospholipid antibodies cause endothelial cells, monocytes, and platelets to become activated, as well as an increase in tissue factor and thromboxane A2. Complement activation might play a key function in pathogenesis. Long-term oral anticoagulation is used to treat thrombosis, and individuals having arterial episodes should be treated quickly. Patients with systemic lupus erythematosus (SLE), as well as those with solely obstetric antiphospholipid syndrome, should get primary thromboprophylaxis. Obstetric care is based on a combination of medical and obstetric high-risk management, as well as aspirin and heparin therapy. Possible supplementary therapy for this condition is hydroxychloroquine. Statins, rituximab, and novel anticoagulant medicines are all potential future treatments for non-pregnant individuals with antiphospholipid syndrome. We aim to review the role of direct-acting oral anticoagulants (DOACs) as thromboprophylactic drugs in the treatment of APS in this article. The treatment of venous thromboembolism has been transformed by a new class of DOACs. These drugs, such as rivaroxaban, function by inhibiting factor Xa directly. Not only do they have known anticoagulant actions, but they also obviate the need for dosage monitoring and modification, in contrast to warfarin. We conducted an exhaustive literature search of PubMed/MEDLINE and Google Scholar Indexes using the keywords "Antiphospholipid syndrome," "thromboprophylaxis," and "oral anticoagulants" up to September 2021. We found that DOACs have been shown to be non-inferior to warfarin in a variety of anticoagulation situations in a number of high-powered clinical studies. In many hypercoagulable conditions such as APS, DOACs are quickly establishing themselves as first-line therapy. This article is focused on comprehensively reviewing the mechanism of action of DOACs, their role as thromboprophylactic drugs, risks and complications of DOACs, and comparing their efficacy with the standard treatment protocol and warfarin.

New Hemostatic Agents: Perioperative Anesthetic Considerations

AIM

Pharmacologic agents with procoagulant effects and antidotes against antithrombotic drugs play an important role in the prevention and management of perioperative coagulopathic bleeding. The aim of this narrative review is knowledge transfer from new and renewed hemostatic agents to anesthesiologists and other physicians involved in perioperative medicine.

METHODS

The literature search was performed on PubMed and the Summaries of Product Characteristics of 6 pharmacologic agents of interest: fibrinogen concentrate, vonicog alfa, susoctocog alfa, idarucizumab, andexanet alfa, and argatroban.

RESULTS AND DISCUSSION

This review highlights renewed interest in fibrinogen concentrate, an old prohemostatic drug, in correcting hypofibrinogenemia which is a leading pathomechanism of perioperative bleeding. This review describes clinically relevant aspects for brand new recombinant prohemostatic drugs for their use in critical clinical situations: vonicog alfa for the prevention and correction of bleeding in von Willebrand syndrome, and susoctocog alfa in acquired hemophilia A. Clinical experience and increasing evidence broadened the field of applications of the old antithrombotic drug argatroban to heparin resistance. New antidotes against new antithrombotic agents revolutionized the safety of chronic antithrombotic therapy in the emergency situations of acute and trauma surgery. Information on dosing and handling of new hemostatic drugs is summarized.

CONCLUSION

New and potent hemostatic agents exist for perioperative use and may enrich the armamentarium of anesthesiologists. Implementation into clinical practice requires their availability and user knowledge. Sustainability of these new drugs depends on post-licensing research, cost-effectiveness, and clinical experience.

Direct-Acting Oral Anticoagulants and Their Reversal Agents-An Update

Background: Over the last ten years, a new class of drugs, known as the direct-acting oral anticoagulants (DOACs), have emerged at the forefront of anticoagulation therapy. Like the older generation anticoagulants, DOACs require specific reversal agents in cases of life-threatening bleeding or the need for high-risk surgery. Methods: Published literature was searched, and information extracted to provide an update on DOACS and their reversal agents. Results: The DOACs include the direct thrombin inhibitor—dabigatran, and the factor Xa inhibitors—rivaroxaban, apixaban, edoxaban, and betrixaban. These DOACs all have a rapid onset of action and each has a predictable therapeutic response requiring no monitoring, unlike the older anticoagulants, such as warfarin. Two reversal agents have been approved within the last five years: idarucizumab for the reversal of dabigatran, and andexanet alfa for the reversal of rivaroxaban and apixaban. Additionally, ciraparantag, a potential “universal” reversal agent, is currently under clinical development. Conclusions: A new generation of anticoagulants, the DOACs, and their reversal agents, are gaining prominence in clinical practice, having demonstrated superior efficacy and safety profiles. They are poised to replace traditional anticoagulants including warfarin.

Topical biomaterials to prevent post-tonsillectomy hemorrhage

Despite advances in surgical technique, postoperative hemorrhage remains a common cause of mortality and morbidity for patients following tonsillectomy. Application of biomaterials at the time of tonsillectomy can potentially accelerate mucosal wound healing and eliminate the risk of post-tonsillectomy hemorrhage (PTH). To understand the current state and identify possible routes for the development of the ideal biomaterials to prevent PTH, topical biomaterials for eliminating the risk of PTH were reviewed. Alternative topical biomaterials that hold the potential to reduce the risk of PTH were also summarized.

The impact of prothrombin complex concentrates when treating DOAC-associated bleeding: a review

Background

Bleeding complications are a risk associated with all anticoagulants. Currently, the treatment options for the management of direct oral anticoagulant (DOAC)-associated bleeding are limited. Prothrombin complex concentrates (PCCs) have been proposed as a potential therapeutic option, and evidence regarding their use is increasing.

Review

Many studies supporting PCC have used preclinical models and healthy volunteers; however, more recently, observational studies have further improved insight into current DOAC reversal strategies. Multiple clinical practice guidelines now specifically suggest use of PCCs for this indication. Specific reversal agents for Factor Xa inhibitors may become available in the near future, but data on their efficacy are still emerging.

Conclusions

Ultimately, a multimodal approach may be the optimal strategy to restore haemostasis in patients presenting with DOAC-associated coagulopathy.

Electronic supplementary material

The online version of this article (10.1186/s12245-018-0215-6) contains supplementary material, which is available to authorized users.

Emergency care of patients receiving non-vitamin K antagonist oral anticoagulants

Non-vitamin K antagonist oral anticoagulants (NOACs), which inhibit thrombin (dabigatran) and factor Xa (rivaroxaban, apixaban, edoxaban) have been introduced in several clinical indications. Although NOACs have a favourable benefit-risk profile and can be used without routine laboratory monitoring, they are associated-as any anticoagulant-with a risk of bleeding. In addition, treatment may need to be interrupted in patients who need surgery or other procedures. The objective of this article, developed by a multidisciplinary panel of experts in thrombosis and haemostasis, is to provide an update on the management of NOAC-treated patients who experience a bleeding episode or require an urgent procedure. Recent advances in the development of targeted reversal agents are expected to help streamline the management of NOAC-treated patients in whom rapid reversal of anticoagulation is required.

Reversal of apixaban anticoagulation by four-factor prothrombin complex concentrates in healthy subjects: a randomized three-period crossover study

Essentials Prothrombin complex concentrates (PCCs) may reverse the effect of factor Xa (FXa) inhibitors. We conducted an open-label, randomized, placebo-controlled, three-period crossover study in 15 subjects. Both PCCs rapidly reversed apixaban-mediated decreases in mean endogenous thrombin potential. Four-factor PCC administration had no effect on apixaban pharmacokinetics or anti-FXa activity.

SUMMARY

Background Currently, there is no approved reversal agent for direct activated factor Xa (FXa) inhibitors; however, several agents are under investigation, including prothrombin complex concentrates (PCCs). Objective This open-label, randomized, placebo-controlled, three-period crossover study assessed the effect of two four-factor PCCs on apixaban pharmacodynamics and pharmacokinetics in 15 healthy subjects. Methods Subjects received apixaban 10 mg twice daily for 3 days. On day 4, 3 h after apixaban, subjects received a 30-min infusion of 50 IU kg-1 Cofact, Beriplex P/N (Beriplex), or saline. Change in endogenous thrombin potential (ETP), measured with a thrombin generation assay (TGA), was the primary endpoint. Secondary endpoints included changes in other TGA parameters, prothrombin time (PT), International Normalized Ratio (INR), activated partial thromboplastin time, anti-FXa activity, apixaban pharmacokinetics, and safety. Results Apixaban-related changes in ETP and several other pharmacodynamic measures occurred following apixaban administration. Both PCCs reversed apixaban's effect on ETP; the differences in adjusted mean change from pre-PCC baseline to end of infusion were 425 nm min (95% confidence interval [CI] 219.8-630.7 nm min; P < 0.001) for Cofact, and 91 nm min (95% CI - 31.3 to 212.4 nm min; P > 0.05) for Beriplex. Both PCCs returned ETP to pre-apixaban baseline levels 4 h after PCC infusion, versus 45 h for placebo. For both PCCs, mean ETP peaked 21 h after PCC initiation, and then slowly decreased over the following 48 h. Both PCCs reversed apixaban's effect on TGA peak height, PT, and INR. Apixaban pharmacokinetic and anti-FXa profiles were consistent across treatments. Conclusions Cofact and Beriplex reversed apixaban's steady-state effects on several coagulation assessments.

Vitamin K antagonists: relative strengths and weaknesses vs. direct oral anticoagulants for stroke prevention in patients with atrial fibrillation

Vitamin K antagonists (VKAs) have been the mainstay of anticoagulation therapy for more than 50 years. VKAs are mainly used for the prevention of stroke in patients with atrial fibrillation (AF) and the treatment and secondary prevention of venous thromboembolism. In the past 5 years, four new agents-the direct factor Xa inhibitors apixaban, edoxaban and rivaroxaban and the direct thrombin inhibitor dabigatran [collectively known as direct oral anticoagulants (DOACs) or non-VKA oral anticoagulants]-have been approved for these and other indications. Despite these new treatment options, the VKA warfarin currently remains the most frequently prescribed oral anticoagulant. The availability of DOACs provides an alternative management option for patients with AF, especially when the treating physician is hesitant to prescribe a VKA owing to associated limitations, such as food and drug interactions, and concerns about bleeding complications. Currently available real-world evidence shows that DOACs have similar or improved effectiveness and safety outcomes compared with warfarin. Treatment decisions on which DOAC is best suited for which patient to maximize safety and effectiveness should take into account not only clinically relevant patient characteristics but also patient preference. This article reviews and highlights real and perceived implications of VKAs for the prevention of stroke in patients with non-valvular AF, with specific reference to their strengths and weaknesses compared with DOACs.

Preclinical and Clinical Data for Factor Xa and "Universal" Reversal Agents

Oral Factor Xa (FXa) inhibitors, a growing class of direct-acting anticoagulants, are frequently used to prevent stroke and systemic embolism in patients with atrial fibrillation and to prevent and treat venous thromboembolism. These drugs reduce the risk of clotting at the expense of increasing the risk of bleeding, and currently they have no specific reversal agent. However, andexanet alfa, a recombinant modified FXa decoy molecule, is in a late-phase clinical trial in bleeding patients, and ciraparantag, a small molecule that appears to reverse many anticoagulants including the FXa inhibitors, is in development. This review summarizes the published data to date on both drugs, which have the potential to change the management approach to patients with FXa inhibitor-associated major hemorrhage.

Efficacy and Safety of Direct Oral Anticoagulants Compared to Warfarin in Prevention of Thromboembolic Events Among Elderly Patients with Atrial Fibrillation

Direct oral anticoagulants (DOACs), previously also known as novel oral anticoagulants (NOACs), have increased the therapeutic options for stroke prevention in atrial fibrillation (AF). Previous studies comparing their relative efficacy and safety do not address age-related differences, such as comorbidities and physical and social boundaries. This review aimed to summarize and compare the clinical and safety outcomes of DOACs and warfarin for stroke prevention in AF in the elderly population (≥ 65 years). We searched PubMed for randomized controlled trials and meta-analyses that compared DOACs and warfarin in elderly patients with AF. Stroke and systemic embolism (SSE) and major bleeding (MB) were primary outcomes. Secondary outcomes included ischemic stroke, all-cause mortality, intracranial bleeding, and gastrointestinal bleeding. Of 66 studies identified, one randomized control trial (RCT) and one meta-analysis were included. DOACs were at least as effective at reducing the risk of SSE as warfarin. DOACs demonstrated a minimal benefit for ischemic stroke (dabigatran, 110 mg, relative risk (RR) 1.08; edoxaban, 60 mg, RR 1.00; and apixaban, 5 mg, RR 0.99). DOACs associated with decreased risk of MB relative to warfarin include dabigatran, 110 mg; apixaban, 5 mg; and edoxaban, 60 mg (RR 0.80, 0.70, and 0.80, respectively), while dabigatran, 150 mg, and rivaroxaban, 20 mg, increased risk (RR 0.79 - 0.83, respectively). Dabigatran, 110 mg and 150 mg doses, and edoxaban increased the risk of gastrointestinal bleeding (RR 1.04, 1.12, and 1.23, respectively). Lower rates of SSE and intracranial bleeding were seen with DOACs compared to warfarin. Dabigatran, 150 mg, and rivaroxaban, 20 mg, were associated with higher MB in older elderly compared to warfarin. DOACs may be attractive alternatives to warfarin, but further studies are needed to make clinical recommendations.

Preclinical and clinical data for factor Xa and "universal" reversal agents

Oral Factor Xa (FXa) inhibitors, a growing class of direct-acting anticoagulants, are frequently used to prevent stroke and systemic embolism in patients with atrial fibrillation and to prevent and treat venous thromboembolism. These drugs reduce the risk of clotting at the expense of increasing the risk of bleeding, and currently they have no specific reversal agent. However, andexanet alfa, a recombinant modified FXa decoymolecule, is in a late-phase clinical trial in bleeding patients, and ciraparantag, a small molecule that appears to reverse many anticoagulants including the FXa inhibitors, is in development. This review summarizes the published data to date on both drugs, which have the potential to change the management approach to patients with FXa inhibitoreassociated major hemorrhage.

Diagnosis, prognosis and therapeutic management of acute pulmonary embolism

Pulmonary embolism (PE) is a leading cause of mortality worldwide. Recognizing PE and administering anticoagulants can significantly improve patient outcomes by reducing mortality rates and preventing recurrent events. For more than 50 years, standard therapy has involved parenteral anticoagulation followed by long-term therapy with the vitamin K antagonist warfarin. However, management of warfarin therapy is challenging due to its narrow therapeutic range and interactions with genetic and environmental factors. Direct oral anticoagulants (DOACs) have been developed to simplify anticoagulation and avoid the concerns associated with warfarin. DOACs are administered at a fixed dosage without routine monitoring and have few drug interactions. In recent years, DOACs have received FDA approval for the treatment of acute deep venous thrombosis (DVT) and PE based on the results of well-conducted clinical trials. This review discusses approaches to the diagnosis and treatment of PE and the use of DOACs as an alternative to warfarin treatment for the management of the disease. While many of the indications for DOACs and concepts discussed apply to both DVT and PE, our focus will be acute PE.

Reversal of Dabigatran with Idarucizumab

INTRODUCTION

The use of novel oral anticoagulants such as dabigatran has been increasing over the last five years. Indicated for use in the prevention of thromboembolic complications from non-valvular atrial fibrillation and for the treatment and prevention of venous thromboembolic disease, dabigatran is increasingly encountered clinically. Lack of an efficacious reversal agent has been a challenge for increased clinical 10 adoption, and for management of patients with bleeding complications while taking dabigatran, or those requiring urgent procedures while taking dabigatran. Idarucizumab, a monoclonal antibody fragment, has recently been approved for use to reverse anticoagulation with dabigatran in patients with serious bleeding.

AREAS COVERED

Herein we discuss the development and early clinical data evaluating the use of idarucizumab for dabigatran reversal. Expert commentary: Idarucizumab has been shown to be an efficacious reversal agent for patients receiving dabigatran. The drug provides a novel and clinically useful agent for patients with significant bleeding while receiving dabigatran, or those needing urgent invasive procedures.

NOAC monitoring, reversal agents, and post-approval safety and effectiveness evaluation: A cardiac safety research consortium think tank

Four non-vitamin K antagonist oral anticoagulants (dabigatran, rivaroxaban, apixaban, and edoxaban) have been approved in the United States for treatment of atrial fibrillation (AF) and venous thromboembolic disease. They have been as or more effective than the prior standards of care, with less fatal or intracranial bleeding, fewer drug and dietary interactions, and greater patient convenience. Nonetheless, the absence of the ability for clinicians to assess compliance or washout with a simple laboratory test (or to adjust dosing with a similar assessment) and the absence of an antidote to rapidly stop major hemorrhage or to enhance safety in the setting of emergent or urgent surgery/procedures have been limitations to greater non-vitamin K antagonist oral anticoagulant usage and better thromboembolic prevention. Accordingly, a Cardiac Research Safety Consortium "think tank" meeting was held in February 2015 to address these concerns. This manuscript reports on the discussions held and the conclusions reached at that meeting.

Reversing the Effect of Oral Anticoagulant Drugs: Established and Newer Options

The vitamin K antagonists (VKAs) have been the standard (and only) oral anticoagulants used for the long-term treatment or prevention of venous thromboembolism or stroke in patients with atrial fibrillation. The coagulopathy induced by VKAs can be reversed with vitamin K, and in urgent situations, the vitamin K-dependent coagulation factors can be replaced by transfusion. In the last decade, a new class of oral anticoagulants has been developed, direct oral anticoagulants that bind to a specific coagulation factor and neutralize it. These compounds were shown to be effective and safe compared with the VKAs and were licensed for specific indications, but without a specific reversal agent. The absence of a reversal agent is a barrier to more widespread use of these agents. Currently, for the management of major life-threatening bleeding with the direct oral anticoagulants, most authorities recommend the use of four factor prothrombin complex concentrates. There are now three reversal agents in development and poised to enter the market. Idarucizumab is a specific antidote targeted to reverse the direct thrombin inhibitor, dabigatran, which was recently approved for use in the USA. Andexanet alfa is an antidote targeted to reverse the oral direct factor Xa inhibitors as well as the indirect inhibitor enoxaparin. Ciraparantag is an antidote targeted to reverse the direct thrombin and factor Xa inhibitors as well as the indirect inhibitor enoxaparin.

Newer Oral Anticoagulants: Stroke Prevention and Pitfalls

Warfarin is very effective in preventing stroke in patients with atrial fibrillation. However, its use is limited due to fear of hemorrhagic complications, unpredictable anticoagulant effects related to multiple drug interactions and dietary restrictions, a narrow therapeutic window, frequent difficulty maintaining the anticoagulant effect within a narrow therapeutic window, and the need for inconvenient monitoring. Several newer oral anticoagulants have been approved for primary and secondary prevention of stroke in patients with non-valvular atrial fibrillation. These agents have several advantages relative to warfarin therapy. As a group, these direct oral anticoagulants (DOAC), which include the direct thrombin inhibitor, dabigatran, and the factor Xa inhibitors (rivaroxaban, apixaban, and edoxaban), are more effective than dose adjusted warfarin for prevention of all-cause stroke (including both ischemic and hemorrhagic stroke), and have an overall more favorable safety profile. Nevertheless, an increased risk of gastrointestinal bleeding (with the exception of apixaban), increased risk for thrombotic complication with sudden discontinuation, and inability to accurately assess and reverse anticoagulant effect require consideration prior to therapy initiation, and pose a challenge for decision making in acute stroke therapy.

Preventing bleeding and thromboembolic complications in atrial fibrillation patients undergoing surgery

Neurologists feel uneasy when asked about temporary anticoagulant interruption for surgery in patients with atrial fibrillation (AF). Rational decisions can be made based on current scientific evidence. Method Critical review of international guidelines and selected references pertaining to bleeding and thromboembolism during periods of oral anticoagulant interruption. Results Withholding oral anticoagulants leads to an increased risk of perioperative thromboembolism, depending on factors such as age, renal and liver function, previous ischemic events, heart failure etc. Surgeries are associated with a variable risk of bleeding - from minimal to very high. Individualized decisions about preoperative drug suspension, bridging therapy with heparin and time to restart oral anticoagulants after hemostasis can significantly reduce these opposing risks. Conclusion Rational decisions can be made after discussion with all Health care team professionals involved and consideration of patient fears and expectations. Formal written protocols should help managing antithrombotic treatment during this delicate period.

Gastrointestinal bleeding in patients receiving oral anticoagulation: Current treatment and pharmacological perspectives

Gastrointestinal bleeding (GIB) is a potentially fatal and avoidable medical condition that poses a burden on global health care costs. The rate of major GIB related to the use of some direct acting oral anticoagulant drugs (DOACs), is higher than that detected in warfarin users. Current strategies in the treatment of GIBs in patients receiving warfarin or DOACs (vitamin K, activated charcoal; hemodialysis; recombinant factor VIIa; [activated] prothrombin complex concentrates) including indications for the treatment of bleeding based on different degrees of severity of the episodes, is reported in this article. Potential preventive strategies to mitigate the risk of GIBs (e.g. upper endoscopy/biopsy, colon cancer screening; eradication of Helicobacter pylori prior to starting anticoagulation; use of proton-pump inhibitors, identification of risk factors for bleeding) are also reported as well as the fact that some of them have not been tested so far in patients receiving DOACs. Antidotes that experimentally reverse the anti-coagulant effect of dabigatran (Idarucizumab; BI 655075; Boehringer Ingelheim); of rivaroxaban, apixaban, or edoxaban (Andexanet alfa, r-Antidote, PRT064445; Portola Pharmaceuticals) or of all DOACs (Aripazine, PER-977, ciraparantag; Perosphere Inc.) are discussed. Likewise, population pharmacokinetics modeling related to the rate of major DOACs-related GIBs is presented. It is also emphasized that the occurrence of GIB reflects the presence of patients at the highest risk for adverse outcomes. Finally, the implications of the concept that patient characteristics and the severity of illness (i.e. comorbidities) exert a greater impact on the risk of GIB than the type of antithrombotic agent employed, are analyzed.

WITHDRAWN:The onset of thalamic hemorrhage in Rivaroxaban in oral IX factor complex formulation administration, but showed a hematoma expansion case

Ahead of Print article withdrawn by publisher.