A specific antidote for dabigatran: functional and structural characterization

Andexanet Alfa-Associated Heparin Resistance in Cardiac Surgery: Mechanism and In Vitro Perspectives

BACKGROUND

Andexanet alfa (andexanet) is the only Food and Drug Administration-approved antidote for direct FXa (factor Xa) inhibitors but has been reported to cause resistance to unfractionated heparin (UFH). This has delayed anticoagulation for procedures requiring cardiopulmonary bypass. The mechanism, andexanet and UFH dose dependence, and thrombotic risk of andexanet-associated heparin resistance are unknown.

METHODS

The effect of andexanet in vitro was determined using activated clotting times and thromboelastography. Ex vivo cardiopulmonary bypass circuits were used to determine whether andexanet impaired anticoagulation for extracorporeal circulation. Kinetics of AT (antithrombin) inhibition of FXa and thrombin were measured in the presence of andexanet. Equilibrium modeling and thrombin generation assay validation were used to predict the role of andexanet, AT, and UFH concentrations in andexanet-associated heparin resistance.

RESULTS

Andexanet prevented UFH-mediated prolongation of activated clotting times and thromboelastography times. At lower concentrations of andexanet, heparin resistance could be overcome with suprapharmacologic doses of UFH, but not at higher andexanet concentrations. Andexanet rendered standard doses of UFH inadequate to prevent circuit thrombosis, and suprapharmacologic UFH doses were only partially able to overcome this. Scanning electron microscopy demonstrated coagulation activation in circuits. Andexanet prevented UFH enhancement of AT-mediated inhibition of FXa and thrombin. Equilibrium modeling and thrombin generation assay validation demonstrated that andexanet creates a triphasic equilibrium with UFH and AT: initial UFH unresponsiveness, normal UFH responsiveness when andexanet is depleted, and finally AT depletion. Sufficient cardiopulmonary bypass heparinization can only occur at low therapeutic andexanet doses and normal AT levels. Higher andexanet doses or AT deficiency may require high UFH doses and potentially AT supplementation.

CONCLUSIONS

Andexanet causes heparin resistance due to redistribution of UFH-bound AT. If andexanet cannot be avoided before heparinization and direct thrombin inhibitors are undesirable, our in vitro study suggests excess UFH should be considered as a potential strategy before AT supplementation.

Multidisciplinary Expert Guidance for the Management of Severe Bleeding on Oral Anticoagulation: An Algorithm for Practicing Clinicians

Bleeding complications associated with oral anticoagulant (OAC) frequently lead to emergency department visits and hospitalization. Short-term all-cause mortality after severe bleeding is substantial ranging from approximately 10% for gastrointestinal bleeding (the most frequent single site) to approximately 50% for intracranial bleeding. A protocol for multidisciplinary approach to bleeding is needed to (i) ensure rapid identification of patients at risk of adverse outcomes, (ii) optimize delivery of supportive measures, (iii) treat the source of bleeding, and (iv) administer anticoagulant reversal or hemostatic therapies judiciously for patients most likely to benefit. We convened a multidisciplinary panel of experts (emergency medicine, gastroenterology, general internal medicine, hematology, neurology, pharmacy, thrombosis) to review the literature and provide practical guidance including a corresponding algorithm for use at the point of care to assist clinicians in the management of patients with acute severe OAC-related bleeding.

Thrombolysis After Dabigatran Reversal for Acute Ischemic Stroke: A National Registry-Based Study and Meta-Analysis

BACKGROUND AND OBJECTIVES

Limited data exist on the safety of IV thrombolysis (IVT) for acute ischemic stroke (AIS) after dabigatran reversal with idarucizumab. We sought to evaluate the safety and efficacy of idarucizumab pretreatment in patients with AIS receiving IVT.

METHODS

A national registry-based study evaluated the safety and efficacy of IVT in this specific subgroup. We also conducted a systematic review and meta-analysis of cohort studies and case series, aiming to document the pooled rates of (1) symptomatic intracranial hemorrhage (sICH), (2) any intracranial hemorrhage, (3) 3-month mortality, and (4) the proportion of excellent (modified Rankin Scale [mRS] scores 0-1) and (5) good (mRS scores 0-2) functional outcome at 3 months among patients with AIS, who received IVT after dabigatran reversal with idarucizumab. Moreover, we sought to compare these outcomes between IVT-treated patients after dabigatran reversal with idarucizumab and IVT-treated patients without dabigatran pretreatment.

RESULTS

Thirteen cohorts including our nation-wide registry-based cohort and 1 case series comprising 553 patients with AIS (mean age: 75 years; male sex: 65%; median baseline NIH Stroke Scale score: 11 points) receiving idarucizumab before IVT were included in this meta-analysis. The pooled rate of sICH after IVT after idarucizumab administration was 4% (95% CI 1-9; I2 = 26%), while the pooled rates of any intracranial hemorrhage and 3-month mortality were 10% (95% CI 5-16; I2 = 24%) and 18% (95% CI 10-27; I2 = 0%), respectively. The pooled rates of excellent and good functional outcomes at 3 months were 56% (95% CI 27-83; I2 = 69%) and 70% (95% CI 57-81; I2 = 40%), respectively. The risk of sICH (risk ratio [RR] 1.86; 95% CI 0.91-3.80; I2 = 0%), any intracranial hemorrhage (RR 1.76; 95% CI 0.99-3.11; I2 = 8%), and 3-month mortality (RR 1.50; 95% CI 0.91-2.48; I2 = 0%) did not differ between patients with AIS receiving IVT with and without idarucizumab. Moreover, idarucizumab administration was associated with higher likelihood of achieving a 3-month good functional outcome (RR 1.35; 95% CI 1.11-1.65; I2 = 27%).

DISCUSSION

IVT for AIS after dabigatran reversal with idarucizumab seems to be safe and effective in observational studies with limited number of patients. Randomized-controlled clinical trials are warranted to provide robust evidence on the safety and efficacy of IVT in this specific AIS subgroup.

Andexanet alfa-associated heparin resistance in cardiac surgery: mechanism and in vitro perspectives

Background

Andexanet alfa (andexanet) is the only FDA-approved antidote for direct factor Xa (FXa) inhibitors but has been reported to cause resistance to unfractionated heparin (UFH). This has delayed anticoagulation for procedures requiring cardiopulmonary bypass (CPB). The mechanism, andexanet and UFH dose dependence, and thrombotic risk of andexanet-associated heparin resistance are unknown.

Methods

The effect of andexanet in vitro was determined using activated clotting times (ACT) and thromboelastography (TEG). Ex vivo CPB circuits were used to determine whether andexanet impaired anticoagulation for extracorporeal circulation. Kinetics of antithrombin (AT) inhibition of FXa and thrombin were measured in the presence of andexanet. Equilibrium modeling and thrombin generation assay (TGA) validation were used to predict the role of andexanet, AT, and UFH concentrations in andexanet-associated heparin resistance.

Results

Andexanet prevented UFH-mediated prolongation of ACT and TEG times. At lower concentrations of andexanet, heparin resistance could be overcome with suprapharmacologic doses of UFH, but not at higher andexanet concentrations. Andexanet rendered standard doses of UFH inadequate to prevent circuit thrombosis, and suprapharmacologic UFH doses were only partially able to overcome this. Scanning electron microscopy demonstrated coagulation activation in circuits. Andexanet prevented UFH enhancement of AT-mediated inhibition of FXa and thrombin. Equilibrium modeling and TGA validation demonstrated that andexanet creates a triphasic equilibrium with UFH and AT: initial UFH unresponsiveness, normal UFH responsiveness when andexanet is depleted, and finally AT depletion. Sufficient CPB heparinization can only occur at low therapeutic andexanet doses and normal AT levels. Higher andexanet doses or AT deficiency may require both AT supplementation and very high UFH doses.

Conclusions

Andexanet causes heparin resistance due to redistribution of UFH-bound AT. If andexanet cannot be avoided prior to heparinization and direct thrombin inhibitors are undesirable, our in vitro study suggests excess UFH should be considered as a potential strategy prior to AT supplementation.

Highlights

Andexanet alfa causes heparin resistance not by depleting antithrombin, but rather by sequestering heparin-bound antithrombin such that it cannot act as an anticoagulant.Heparin responsiveness in the presence of Andexanet alfa is triphasic such that the effect of a dose of heparin can now be predicted in vitro based on the relative concentrations of andexanet, heparin, and antithrombin.The in vitro insights provided by this work provide a rational starting point for further clinical elucidation of the problem and management of andexanet-associated heparin resistance.

Anticoagulation management for cardiopulmonary bypass using TEG® 6 s in a patient receiving both heparin and dabigatran

BACKGROUND

It is difficult to evaluate adequate dose of heparin for cardiopulmonary bypass (CPB) by activated clotting time (ACT) in a patient receiving both heparin and dabigatran because dabigatran can also prolong ACT. We evaluated the effect of dabigatran by thromboelastography (TEG) to determine adequate heparin dose for CPB.

CASE PRESENTATION

An 81-year-old woman receiving both heparin and dabigatran was scheduled for an emergency surgical repair of iatrogenic atrial septal perforation. Although ACT was prolonged to 419 s, we performed TEG to distinguish anticoagulation by dabigatran from heparin comparing R in CK and CHK. As the results of TEG indicated residual effect of dabigatran, we reversed dabigatran by idarucizumab and then dosed 200 U/kg of heparin to achieve adequate anticoagulation for CPB by heparin.

CONCLUSIONS

TEG could help physicians to determine need for idarucizumab and also an adequate dose of heparin to establish appropriate anticoagulation for CPB.

Idarucizumab in dabigatran-treated patients with acute stroke: a review and clinical update

Idarucizumab is an antibody fragment specific for the immediate reversal of dabigatran anticoagulation effects. The use of idarucizumab is approved for dabigatran-treated patients suffering from life-threatening or uncontrolled bleeding and those in need of urgent surgery or invasive procedures. Data from randomized controlled clinical trials and real-world experience provide reassuring evidence about the efficacy and safety of idarucizmab use in patients with acute stroke. In this narrative review, we summarize the available real-world evidence and discuss the relevance and importance of idarucizumab treatment in acute stroke patients in everyday clinical practice. In addition, we also discuss special issues like prothrombin complex concentrate application as an alternative to idarucizumab, its application before endovascular therapy, sensitivity of thrombi to lysis, and necessary laboratory examinations.

Is there a role for the laboratory monitoring in the management of specific antidotes of direct oral anticoagulants?

Given the growing number of patients receiving direct oral anticoagulant (DOAC), patients requiring rapid neutralization is also increasing in case of major bleedings or urgent surgery/procedures. Idarucizumab is commercialized as a specific antidote to dabigatran while andexanet alfa has gained the Food and Drug Administration and the European Medicines Agency approval as an oral anti-factor Xa inhibitors antidote. Other antidotes or hemostatic agents are still under preclinical or clinical development, the most advanced being ciraparantag. DOAC plasma levels measurement allows to appropriately select patient for antidote administration and may prevent unnecessary prescription of expensive molecules in some acute clinical settings. However, these tests might be inconclusive after some antidote administration, namely andexanet alfa and ciraparantag. The benefit of laboratory monitoring following DOAC reversal remains unclear. Here, we sought to provide an overview of the key studies evaluating the safety and efficacy of DOAC reversal using the most developed/commercialized specific antidotes, to discuss the potential role of the laboratory monitoring in the management of patients receiving DOAC specific antidotes and to highlight the areas that deserve further investigations in order to establish the exact role of laboratory monitoring in the appropriate management of DOAC specific antidotes.

Clinical guideline on reversal of direct oral anticoagulants in patients with life threatening bleeding

BACKGROUND

Anticoagulation is essential for the treatment and prevention of thromboembolic events. Current guidelines recommend direct oral anticoagulants (DOACs) over vitamin K antagonists in DOAC-eligible patients. The major complication of anticoagulation is serious or life-threatening haemorrhage, which may necessitate prompt haemostatic intervention. Reversal of DOACs may also be required for patients in need of urgent invasive procedures. This guideline from the European Society of Anaesthesiology and Intensive Care (ESAIC) aims to provide evidence-based recommendations and suggestions on how to manage patients on DOACs undergoing urgent or emergency procedures including the treatment of DOAC-induced bleeding.

DESIGN

A systematic literature search was performed, examining four drug comparators (dabigatran, rivaroxaban, apixaban, edoxaban) and clinical scenarios ranging from planned to emergency surgery with the outcomes of mortality, haematoma growth and thromboembolic complications. The GRADE (Grading of Recommendations, Assessment, Development and Evaluation) methodology was used to assess the methodological quality of the included studies. Consensus on the wording of the recommendations was achieved by a Delphi process.

RESULTS

So far, no results from prospective randomised trials comparing two active comparators (e.g. a direct reversal agent and an unspecific haemostatic agent such as prothrombin complex concentrate: PCC) have been published yet and the majority of publications were uncontrolled and observational studies. Thus, the certainty of evidence was assessed to be either low or very low (GRADE C). Thirty-five recommendations and clinical practice statements were developed. During the Delphi process, strong consensus (>90% agreement) was achieved in 97.1% of recommendations and consensus (75 to 90% agreement) in 2.9%.

DISCUSSION

DOAC-specific coagulation monitoring may help in patients at risk for elevated DOAC levels, whereas global coagulation tests are not recommended to exclude clinically relevant DOAC levels. In urgent clinical situations, haemostatic treatment using either the direct reversal or nonspecific haemostatic agents should be started without waiting for DOAC level monitoring. DOAC levels above 50 ng ml-1 may be considered clinically relevant necessitating haemostatic treatment before urgent or emergency procedures. Before cardiac surgery under activated factor Xa (FXa) inhibitors, the use of andexanet alfa is not recommended because of inhibition of unfractionated heparin, which is needed for extracorporeal circulation. In the situation of DOAC overdose without bleeding, no haemostatic intervention is suggested, instead measures to eliminate the DOACs should be taken. Due to the lack of published results from comparative prospective, randomised studies, the superiority of reversal treatment strategy vs. a nonspecific haemostatic treatment is unclear for most urgent and emergency procedures and bleeding. Due to the paucity of clinical data, no recommendations for the use of recombinant activated factor VII as a nonspecific haemostatic agent can be given.

CONCLUSION

In the clinical scenarios of DOAC intake before urgent procedures and DOAC-induced bleeding, practitioners should evaluate the risk of bleeding of the procedure and the severity of the DOAC-induced bleeding before initiating treatment. Optimal reversal strategy remains to be determined in future trials for most clinical settings.

Clinical Care Pathway and Management of Major Bleeding Associated with Nonvitamin K Antagonist Oral Anticoagulants: A Modified Delphi Consensus from Saudi Arabia and UAE

Background

The nonvitamin K antagonist oral anticoagulants (NOACs) have become the mainstay anticoagulation therapy for patients requiring oral anticoagulants (OACs) in the Gulf Council Cooperation (GCC) countries. The frequency of NOAC-associated major bleeding is expected to increase in the Emergency Department (ED). Nonetheless, we still lack local guidelines and recommendations for bleeding management in the region. The present Delphi-based consensus aims to establish a standardized and evidence-based clinical care pathway for managing NOAC-associated major bleeding in the Kingdom of Saudi Arabia (KSA) and the United Arab Emirates (UAE).

Methods

We adopted a three-step modified Delphi method to develop evidence-based recommendations through two voting rounds and an advisory meeting between the two rounds. A panel of 11 experts from the KSA and UAE participated in the consensus development.

Results

Twenty-eight statements reached the consensus level. These statements addressed key aspects of managing major bleeding events associated with NOACs, including the increased use of NOAC in clinical practice, clinical care pathways, and treatment options.

Conclusion

The present Delphi consensus provides evidence-based recommendations and protocols for the management of NOAC-associated bleeding in the region. Patients with major DOAC-induced bleeding should be referred to a well-equipped ED with standardized management protocols. A multidisciplinary approach is recommended for establishing the association between NOAC use and major bleeding. Treating physicians should have prompt access to specific reversal agents to optimize patient outcomes. Real-world evidence and national guidelines are needed to aid all stakeholders involved in NOAC-induced bleeding management.

Causal connectivity measures for pulse-output network reconstruction: Analysis and applications

The causal connectivity of a network is often inferred to understand network function. It is arguably acknowledged that the inferred causal connectivity relies on the causality measure one applies, and it may differ from the network's underlying structural connectivity. However, the interpretation of causal connectivity remains to be fully clarified, in particular, how causal connectivity depends on causality measures and how causal connectivity relates to structural connectivity. Here, we focus on nonlinear networks with pulse signals as measured output, e.g., neural networks with spike output, and address the above issues based on four commonly utilized causality measures, i.e., time-delayed correlation coefficient, time-delayed mutual information, Granger causality, and transfer entropy. We theoretically show how these causality measures are related to one another when applied to pulse signals. Taking a simulated Hodgkin-Huxley network and a real mouse brain network as two illustrative examples, we further verify the quantitative relations among the four causality measures and demonstrate that the causal connectivity inferred by any of the four well coincides with the underlying network structural connectivity, therefore illustrating a direct link between the causal and structural connectivity. We stress that the structural connectivity of pulse-output networks can be reconstructed pairwise without conditioning on the global information of all other nodes in a network, thus circumventing the curse of dimensionality. Our framework provides a practical and effective approach for pulse-output network reconstruction.

Antidote vs. unspecific hemostatic agents for the management of direct oral anticoagulant-related bleeding in trauma

PURPOSE OF REVIEW

The advent of direct oral anticoagulants (DOACs) marks a significant milestone in anticoagulant treatment. However, DOACs can exacerbate bleeding, which is challenging for the treating clinician, especially when combined with traumatic injury.

RECENT FINDINGS

In major bleeding associated with DOACs, rapid reversal of the anticoagulant effects is crucial. Recent observational and nonrandomized interventional trials have demonstrated the effectiveness of the specific antidotes andexanet alfa and idarucizumab as well as the unspecific prothrombin complex concentrates (PCCs) to counteract the anticoagulant effects of DOACs. The European Society of Anaesthesiology and Intensive Care guideline for severe perioperative bleeding and the European trauma guideline propose divergent recommendations for the use of andexanet alfa and PCC to obtain hemostasis in Factor Xa inhibitor-related bleeding. The conflicting recommendations are due to limited evidence from clinical studies and the potential increased risk of thromboembolic complications after the administration of andexanet. Regarding dabigatran-associated major bleeding, both guidelines recommend the specific reversal agent idarucizumab as first-line therapy.

SUMMARY

Current guidelines recommend specific antidots and PCCs in DOAC-related major bleeding. Prospective randomized trials comparing specific vs. nonspecific hemostatic agents in the perioperative setting are needed to evaluate the effectiveness and safety of the hemostatic agents.

Cardiac Tamponade and Duodenal Hemorrhage Caused by Inappropriate Use of Dabigatran in a Patient With End-Stage Renal Failure: A Case Report

A 72-year-old man with end-stage renal failure, receiving 220 mg of dabigatran for chronic atrial fibrillation, was admitted with generalized edema and shortness of breath. Cardiac tamponade caused by pericardial hemorrhage due to inappropriate dabigatran use was treated with pericardial drainage and idarucizumab. Although coagulability normalized, consecutive duodenal hemorrhages occurred, requiring arterial embolization for hemostasis. In cases of severely impaired renal function, the usual dose of idarucizumab may not be sufficient to reverse the effects of dabigatran. Therefore, we considered the need for repeated idarucizumab administration to prevent recurrent bleeding.

Barriers in Access to Idarucizumab in Ischemic Stroke in a Middle-Income Country

Background and Purpose

Current stroke guidelines contraindicate the use of thrombolytics if oral anticoagulants are taken within 48 hours of symptom onset. Idarucizumab is an alternative for patients on dabigatran who experience an acute stroke, so that alteplase may be used. However, this treatment may not be readily available in low/middle-income countries. Our objective is to describe barriers to access to the administration of idarucizumab.

Methods

We applied a structured survey for health personnel, consulted databases of drug providers, and analyzed reports from the National Pharmacologic Surveillance Data to describe idarucizumab use and the related knowledge among prescribers and the drug distribution in health institutions in Colombia between January 2018 and January 2022.

Results

In total, 23.6% of the 337 interviewed physicians' hospitals had access to idarucizumab, and 34.9% of the physicians were unaware of the use of this medication for ischemic stroke. Only 11 private institutions had access to this medication in Colombia. Four male patients with atrial fibrillation received thrombolytics for acute stroke, and two required subsequent mechanical thrombectomy. No fatal complications during hospitalization were observed. Complications included hematuria, hemorrhagic transformation and groin hematoma. None required transfusion or further intervention. All had favorable mRS scores at the 90-day follow-up.

Conclusions

There are multiple barriers to access idarucizumab in Colombia. The main factors identified are the low medication availability in provincial hospitals and the low medical knowledge. However clinical results in this limited group are satisfactory. Stronger public policies are needed to guarantee optimal stroke treatment in patients on DOACs in Colombia.

New insight into the traditional model of the coagulation cascade and its regulation: illustrated review of a three-dimensional view

The coagulation process relies on an intricate network of three-dimensional structural interactions and subtle biological regulations. In the present review, we illustrate the state of the art of the structural biology of the coagulation cascade by surveying the Protein Data Bank and the EBI AlphaFold databases. Investigations performed in the last decade have provided structural information on essentially all players involved in the process. Indeed, the initial characterization of specific and rather canonical domains has been progressively extended to complicated multidomain proteins. Recently, the application of cryogenic electron microscopy techniques has unraveled the structural features of highly complex coagulation factors, which has led to enhanced understanding. This review initially focuses on the structure of the individual factors as a function of their involvement in intrinsic, extrinsic, and common pathways. A specific emphasis is given to what is known or unknown on the structural basis of each step of the cascade. Available data providing clues on the structural recognition of the factors involved in the functional partnerships of the pathways are illustrated. Recent structures of important complexes formed by these proteins with regulators are described, focusing on the drugs used as anticoagulants and on their reversal agents. Finally, we highlight the different roles that innovative biomolecules such as aptamers may have in the regulation of the cascade.

Complement is activated by elevated IgG3 hexameric platforms and deposits C4b onto distinct antibody domains

IgG3 is unique among the IgG subclasses due to its extended hinge, allotypic diversity and enhanced effector functions, including highly efficient pathogen neutralisation and complement activation. It is also underrepresented as an immunotherapeutic candidate, partly due to a lack of structural information. Here, we use cryoEM to solve structures of antigen-bound IgG3 alone and in complex with complement components. These structures reveal a propensity for IgG3-Fab clustering, which is possible due to the IgG3-specific flexible upper hinge region and may maximise pathogen neutralisation by forming high-density antibody arrays. IgG3 forms elevated hexameric Fc platforms that extend above the protein corona to maximise binding to receptors and the complement C1 complex, which here adopts a unique protease conformation that may precede C1 activation. Mass spectrometry reveals that C1 deposits C4b directly onto specific IgG3 residues proximal to the Fab domains. Structural analysis shows this to be caused by the height of the C1-IgG3 complex. Together, these data provide structural insights into the role of the unique IgG3 extended hinge, which will aid the development and design of upcoming immunotherapeutics based on IgG3.

Direct oral anticoagulant drugs for the management of venous thromboembolism

ABSTRACT

Direct oral anticoagulants (DOACs) are effective for both prevention and treatment of venous thromboembolism (VTE) and have favorable safety in comparison with warfarin. Although drug-drug interactions with DOACs are not as frequent as with warfarin, certain drugs can interfere with DOAC metabolism, affect DOAC efficacy, and potentially cause adverse reactions when used in combination with DOACs. The NP must determine which agent is most beneficial for the individual patient with VTE based on a number of factors. A knowledge of periprocedural management of DOACs will assist the NP in providing a smooth transition for patients undergoing minor and major procedures and surgeries.

The methods for removal of direct oral anticoagulants and heparins to improve the monitoring of hemostasis: a narrative literature review

The assessment of hemostasis is necessary to make suitable decisions on the management of patients with thrombotic disorders. In some clinical situations, for example, during thrombophilia screening, the presence of anticoagulants in sample makes diagnosis impossible. Various elimination methods may overcome anticoagulant interference. DOAC-Stop, DOAC-Remove and DOAC Filter are available methods to remove direct oral anticoagulants in diagnostic tests, although there are still reports on their incomplete efficacy in several assays. The new antidotes for direct oral anticoagulants - idarucizumab and andexanet alfa - could be potentially useful, but have their drawbacks. The necessity to remove heparins is also arising as heparin contamination from central venous catheter or therapy with heparin disturbs the appropriate hemostasis assessment. Heparinase and polybrene are already present in commercial reagents but a fully-effective neutralizer is still a challenge for researchers, thus promising candidates remain in the research phase.

Contemporary Antiplatelet and Anticoagulant Therapies for Secondary Stroke Prevention: A Narrative Review of Current Literature and Guidelines

PURPOSE OF REVIEW

Stroke is a leading cause of death and disability worldwide. The annual incidence of new or recurrent stroke is approximately 795,000 cases per year in the United States, of which 87% are ischemic in nature. In addition to the management of modifiable high-risk factors to reduce the risk of recurrent stroke, antithrombotic agents (antiplatelets and anticoagulants) play an important role in secondary stroke prevention. This review will discuss the published literature on the use of antiplatelets and anticoagulants in secondary prevention of acute ischemic stroke and transient ischemic attack (TIA), including their pharmacology, efficacy, and adverse effects. We will also highlight the role of dual antiplatelet therapy (DAPT) in secondary stroke prevention, along with supporting literature.

RECENT FINDINGS

Single antiplatelet therapy (SAPT) with aspirin or clopidogrel reduces the risk of recurrent ischemic stroke in patients with non-cardioembolic ischemic stroke or TIA. However, as shown in recent trials, short-term DAPT with aspirin and clopidogrel or ticagrelor for 21-30 days is more effective than SAPT in patients with minor acute non-cardioembolic stroke or high-risk TIA. Although short-term DAPT is highly effective in preventing recurrent stroke, a more prolonged course can increase bleeding risks without additional benefit. DAPT for 90 days, followed by aspirin monotherapy for patients with large vessel intracranial atherosclerotic disease, is suitable for secondary stroke prevention. However, patients need to be monitored for both minor (e.g., bruising) and major (e.g., intracranial) bleeding complications. Conversely, oral warfarin and newer direct oral anticoagulant (DOACs) such as dabigatran, rivaroxaban, apixaban, and edoxaban are the agents of choice for secondary stroke prevention in patients with non-valvular cardioembolic strokes. DOACs may be preferred over warfarin due to decreased bleeding risks, including ICH, lack of need for international normalized ratio monitoring, no dietary restrictions, and limited drug-drug interactions. The choice between different antiplatelets and anticoagulants for prevention of ischemic stroke depends on the underlying stroke mechanism, cytochrome P450 2C19 polymorphisms, bleeding risk profile, compliance, drug tolerance, and drug resistance. Physicians must carefully weigh each patient's relative benefits and bleeding risks before initiating an antiplatelet/anticoagulant treatment regimen. Further studies are warranted to study the optimal duration of DAPT in symptomatic intracranial atherosclerosis since the benefit is most pronounced in the short term while the bleeding risk remains high during the extended duration of therapy.

Evidence-based Management of Major Bleeding in Patients Receiving Direct Oral Anticoagulants: An Updated Narrative Review on the Role of Specific Reversal Agents

The indications of direct oral anticoagulants (DOACs) have expanded over the past 15 years. DOACs are effective and safe oral anticoagulants associated with lower bleeding risks and mortality than vitamin K antagonists. However, DOAC users are prone to a considerable bleeding risk, which can occur at critical sites or lead to severe life-threatening conditions. Recent statistics indicated that major bleeding occurs in up to 6.62 DOAC users per 100 treatment years. With the increased use of DOACs in clinical practice, DOAC-associated major bleeding is expected to be encountered more frequently in the emergency department. The current international guidelines recommend specific reversal agents for the management of DOAC users with severe bleeding to reverse the anticoagulant effect and restore normal hemostasis. An individualized assessment was incorporated in specific clinical situations to guide the decision pathway of major bleeding management. However, specific reversal agents are unavailable or have limited availability in many countries, which is expected to negatively impact the clinical outcomes of DOAC-associated major bleeding. Limited real-world evidence is available from these countries regarding the clinical outcomes of patients with DOAC-associated major bleeding. This narrative review provided an updated assessment of the evidence-based approaches for the management of major bleeding in DOAC users. We also explored the clinical outcomes of patients with major bleeding from clinical settings where specific reversal agents are unavailable.

Direct Oral Anticoagulant Reversal in the Pediatric Emergency Department

ABSTRACT

Direct oral anticoagulants have been used in the adult population for years and are being used more frequently in pediatrics. Direct oral anticoagulants are chosen preferentially because they do not require close outpatient monitoring, have an equal or better safety profile, and are easy for patients to take. Warfarin is the previous, more commonly used oral anticoagulant and acts as a vitamin K antagonist. Direct oral anticoagulants mechanism of action is different in that they directly inhibit part of the coagulation cascade accomplishing the same end goal. Given their differing mechanisms, they require alternate medications for proper reversal when concerned about overdose of life-threatening bleeds. This review will outline the most commonly used direct oral anticoagulants in pediatric populations and the supporting (mainly adult) data available for proper reversal of these medications in times of need.

A short review of ciraparantag in perspective of the currently available anticoagulant reversal agents

Despite the improved safety-profile of direct oral anticoagulants (DOACs), bleeding complications remain an important side effect of anticoagulant treatment. Although anticoagulant-specific antidotes are available, an universal anticoagulant reversal agent in case of life-threatening bleeding or emergency surgery is not yet available. Ciraparantag, a synthetic small molecule that inactivates heparins and DOAC, is a promising new reversal agent that has been investigated in phase 2 trials. In this short review we provide an overview of the preclinical and clinical evidence of ciraparantag, and compare strengths and weaknesses of ciraparantag and the currently available anticoagulant reversal strategies.

A Historical Perspective on the Reversal of Anticoagulants

There has been a landmark shift in the last several decades in the management and prevention of thromboembolic events. From the discovery of parenteral and oral agents requiring frequent monitoring as early as 1914, to the development of direct oral anticoagulants (DOACs) that do not require monitoring or dose adjustment in the late 20th century, great advances have been achieved. Despite the advent of these newer agents, bleeding continues to be a key complication, affecting 2 to 4% of DOAC-treated patients per year. Bleeding is associated with substantial morbidity and mortality. Although specific reversal agents for DOACs have lagged the release of these agents, idarucizumab and andexanet alfa are now available as antagonists. However, the efficacy of these reversal agents is uncertain, and complications, including thrombosis, have not been adequately explored. As such, guidelines continue to advise the use of nonspecific prohemostatic agents for patients requiring reversal of the anticoagulant effect of these drugs. As the indications for DOACs and the overall prevalence of their use expand, there is an unmet need for further studies to determine the efficacy of specific compared with nonspecific pro-hemostatic reversal agents. In this review, we will discuss the evidence behind specific and nonspecific reversal agents for both parenteral and oral anticoagulants.

Stroke Prevention in Atrial Fibrillation: A Scientific Statement of JACC: Asia (Part 2)

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia and is associated with substantial increases in the risk for stroke and systemic thromboembolism. With the successful introduction of the first non-vitamin K antagonistdirect oral anticoagulant agent (NOAC) in 2009, the role of vitamin K antagonists has been replaced in most clinical settings except in a few conditions for which NOACs are contraindicated. Data for the use of NOACs in different clinical scenarios have been accumulating in the past decade, and a more sophisticated strategy for patients with AF is now warranted. JACC: Asia recently appointed a working group to summarize the most updated information regarding stroke prevention in AF. The aim of this statement is to provide possible treatment options in daily practice. Local availability, cost, and patient comorbidities should also be considered. Final decisions may still need to be individualized and based on clinicians' discretion. This is part 2 of the statement.

Treatment strategy of dabigatran etexilate following the availability of idarucizumab in Japanese patients with non-valvular atrial fibrillation: J-Dabigatran Surveillance 2

BACKGROUND

Idarucizumab, a dabigatran-specific reversal agent, was launched in Japan in 2016. The J-Dabigatran Surveillance 2 study was designed to assess the characteristics and outcomes of dabigatran-treated patients after the launch of idarucizumab.

METHODS

Patient characteristics and outcomes, including thromboembolic and bleeding events, of dabigatran-naïve patients with non-valvular atrial fibrillation (NVAF) who received dabigatran etexilate [110 mg or 150 mg twice-daily (b.i.d.)] for the prevention of ischemic stroke and systemic embolism were investigated and presented descriptively. Absolute standardized differences (ASD) in baseline characteristics compared with the first J-Dabigatran Surveillance (J-Dabi1; 2011-2013) study were included.

RESULTS

In total, 5660 patients were enrolled and 5436 were analyzed in this study; 3516 and 1898 received 110 mg b.i.d. and 150 mg b.i.d. dabigatran, respectively; 22 received other doses. The overall duration of follow-up (mean ± standard deviation) was 287 ± 179 days. Baseline characteristics, including stroke/bleeding-risk scores, were typical of this patient population. Overall, paroxysmal, persistent, permanent, and symptomatic atrial fibrillation were observed for 53.2%, 27.1%, 13.7%, and 53.9% of patients, respectively (J-Dabi1 ASD: 0.2, 0.0, 0.3, and 0.2, respectively). Catheter ablation was selected in 27.9% of patients (J-Dabi1 ASD: 0.6). Rates of clinical outcomes were low in the study (mostly <2%/year). The incidence rate of major bleeding was 1.1%/year (n = 46) and stroke/transient ischemic attack/systemic embolism was 1.7%/year (n = 71). Twelve (0.2%) patients received idarucizumab, commonly for serious bleeding events, and most recovered.

CONCLUSIONS

Dabigatran continues to be safe and well tolerated in patients with NVAF for stroke and systemic embolism prevention and continues to be prescribed appropriately. Treatment outcomes have not changed since the availability of idarucizumab. Since the J-Dabi1 study, treatment guidelines for anticoagulation use in NVAF have been updated based on emerging clinical evidence, accounting for differences in patient characteristics, and making dabigatran a preference for distinct patient populations.

Development and Validation of UPLC-MS/MS Method for Quantifying of Free and Total Dabigatran in Human Plasma: An Application for a Bioequivalence Study

Dabigatran etexilate mesylate (DABE), a prodrug, quickly changes in our bodies after its oral administration into dabigatran (DAB). Accordingly, detecting DABE in plasma is practically unmanageable. A UPLC-MS/MS technique was developed and validated to compute free DAB in participants. For the first time, the central composite design- a type of response surface methodology- was utilized for optimizing variables affecting the cleavage of glucuronide bond. Additionally, the pharmacokinetic parameters of generic medication (okanadab) were determined, and the obtained outcomes were compared to those of branded drug (pradaxa®). The sample preparation was done using methanol as a protein precipitant and the separation was achieved via ACQUITY UPLC BEH C18 column (2.1x50mm, 1.7μm). The elution was isocratically conducted using 10mM ammonium formate: methanol (72:28, v/v) as a mobile phase (MP) and the flow rate was 0.25mL/min. Multiple reaction monitoring (MRM) and positive electrospray ionization (ESI) were used. The determination was performed within 1min, and the calibration growth curve was established over a range of (1.19 - 475) ng/mL using dabigatran-d3 as a tagged internal standard (IS). Bioequivalence research was validated following FDA guidelines for bio-analytical procedures and acceptable outcomes were achieved. The outcomes for okanadab and pradaxa® did not differ significantly.

Idarucizumab reverses dabigatran-induced anticoagulation in treatment of gastric bleeding: A case report

BACKGROUND

The drug instructions for dabigatran recommend adjusting the dosage to 110 mg twice daily for patients with bleeding risk, and performing at least one renal function test per year for patients with moderate renal impairment. However, owing to chronic insidiously worsening renal insufficiency, dabigatran can still accumulate abnormally, necessitating therapy with idarucizumab to reverse the anticoagulation due to severe erosive gastritis with widespread stomach mucosal bleeding.

CASE SUMMARY

A 76-year-old woman with a history of atrial fibrillation who took dabigatran 110 mg twice daily as directed to lessen the chance of stroke, was transported to the hospital with hematemesis and melena. Laboratory findings revealed severe life-threatening, blood-loss-induced anemia with a hemoglobin (Hb) level of 41.0 g/L and marked coagulation abnormalities with thrombin time (TT) > 180 s, most likely caused by dabigatran-induced metabolic disorder. Aggressive acid suppressive, hemostatic, and blood transfusion therapy resulted in the misconception that the bleeding was controlled, with subsequent rebleeding. Idarucizumab was administered in a timely manner to counteract dabigatran's anticoagulant impact, and 12 h later, TT was determined to be 17.4 s, which was within the normal range. Finally, the patient had no active bleeding signs and laboratory findings showed an Hb level of 104 g/L and TT of 17.7 s.

CONCLUSION

Renal function, coagulation function, and dabigatran concentration should be regularly monitored in older patients. Proton pump inhibitor and dabigatran coadministration is still controversial in preventing upper gastrointestinal tract bleeding.

Decision-Making Process for the Management of Acute Stroke in Patients on Oral Anticoagulant: From Guidelines to Clinical Routine

Background: The occurrence of both ischaemic (IS) and haemorrhagic stroke in patients on anticoagulation is a major issue due to the frequency of their prescriptions in westernised countries and the expected impact of anticoagulant activity on recanalization during an IS or on the outcomes associated with intracerebral haemorrhage (ICH). Several guidelines are available but sometimes differ in their conclusions or regarding specific issues, and their application in routine emergency settings may be limited by particular individual issues or heterogeneous local specificities. Methods: Based on the current guidelines and additional published data, the algorithms proposed in this paper aim to help the decision-making process regarding stroke management in the setting of concurrent anticoagulants by addressing specific clinical situations based on clinical variables commonly encountered in real-world practise. Results: For patients on non-vitamin K oral anticoagulants, reversion can be achieved with specific antidotes, but only idarucizumab, the specific dabigatran antidote, is indicated in both IS and ICH. Due to the low risk of a prothrombotic effect, idarucizumab can be immediately used in IS patients eligible for thrombolysis before the dabigatran concentration is known. To optimise ICH management, the time since symptom onset, with thresholds proposed at 6 and 9 hours based on the expected timing of haematoma expansion, could also to be taken into account. Conclusions: Anticoagulant reversal in patients presenting with a stroke remains a major issue, and algorithms based on a step-by-step approach may be useful for clinical practise. Real-life studies strongly support the benefits of idarucizumab availability in stroke units and emergency departments.

2021 Focused Update Consensus Guidelines of the Asia Pacific Heart Rhythm Society on Stroke Prevention in Atrial Fibrillation: Executive Summary

The consensus of the Asia Pacific Heart Rhythm Society (APHRS) on stroke prevention in atrial fibrillation (AF) has been published in 2017 which provided useful clinical guidance for cardiologists, neurologists, geriatricians, and general practitioners in the Asia-Pacific region. In these years, many important new data regarding stroke prevention in AF were reported. The practice guidelines subcommittee members comprehensively reviewed updated information on stroke prevention in AF, and summarized them in this 2021 focused update of the 2017 consensus guidelines of the APHRS on stroke prevention in AF. We highlighted and focused on several issues, including the importance of the AF Better Care pathway, the advantages of non-vitamin K antagonist oral anticoagulants (NOACs) for Asians, the considerations of use of NOACs for Asian AF patients with single one stroke risk factor beyond gender, the role of lifestyle factors on stroke risk, the use of oral anticoagulants during the "coronavirus disease 2019" pandemic, etc. We fully realize that there are gaps, unaddressed questions, and many areas of uncertainty and debate in the current knowledge of AF, and the physician's decision remains the most important factor in the management of AF.

Costs and Healthcare Resource Utilization Associated with Idarucizumab or Andexanet Alfa Oral Anticoagulant Reversal in Patients Hospitalized with Life-Threatening Bleeds

Purpose: To assess costs and healthcare resource utilization (HCRU) associated with the use of idarucizumab for the reversal of dabigatran and andexanet alfa for the reversal of direct oral Factor Xa inhibitors. Methods: This retrospective study utilizing Premier Healthcare Database (PHD) included patients aged ≥18 years on direct oral anticoagulants (DOACs) who experienced life-threatening bleeds, discharged from the hospital during 5/1/2018–6/30/2019, and received idarucizumab or andexanet alfa. Inverse of treatment probability weighting (IPTW) method was used to balance patient and clinical characteristics between treatment cohorts. Results: Idarucizumab patients were older than andexanet alfa patients (median age 81 vs 77 years; p < 0.001), and less likely to experience intracranial hemorrhage (ICH) (37.1%vs 73.8%; p  =  0.001). After IPTW adjustment, idarucizumab patients incurred lower mean total hospital costs ($30,413  ±  $33,028 vs $44,477  ±  $30,036; p < 0.001),and mean intensive care unit (ICU) cost ($25,114  ±  $30,433 vs $43,484  ±  $29,335; p < 0.001). Conclusions: Anticoagulant reversal therapy with idarucizumab was associated with significantly lower adjusted mean total hospital and ICU costs compared with andexanet alfa. However, a higher prevalence of ICH bleeds was noted in the andexanet alfa group. Trial Registration: Not applicable.

Intravenous Thrombolysis After Reversal of Dabigatran With Idarucizumab in Acute Ischemic Stroke: A Case Report

Background: As there is a growing concern about the cerebral embolism events secondary to non-valvular atrial fibrillation (NVAF), novel oral anticoagulant (NOAC) has been more and more widely used as an anticoagulation treatment for the prevention of stroke. However, in the face of life-threatening bleeding or emergency surgery/treatment, NOAC-related antagonists such as idarucizumab need to be urgently used to reverse the NOAC. Using recombinant tissue plasminogen activator (rt-PA) intravenous thrombolysis for acute ischemic stroke requires a time window of 4.5 h. This case reports rt-PA intravenous thrombolysis after reversal of dabigatran anticoagulation with idarucizumab in patients with acute ischemic stroke. Case Presentation: We report the case of 62-year-old Chinese female with NVAF treated with dabigatran 110 mg twice daily, and missed a dose on the eve of the stroke. The patient presented with acute ischemic stroke causing the angle of mouth deviated to right side and left limb weakness in the early morning of the next day. However, the last dosing time of dabigatran was between 24 and 48 h, the patients were given rt-PA intravenous thrombolysis after reversal of dabigatran anticoagulation with idarucizumab, while any potential relative contraindication had been excluded by means of laboratory test and CT scan in the hospitalization services. National Institute of Health stroke scale (NIHSS) score was reduced from 4 to 1, and the patient was discharged after 2 weeks. Conclusion: Our case report adds to the evidence that idarucizumab administration is safe and effective in the setting of patients with atrial fibrillation treated with dabigatran who develop acute ischemic stroke requiring rt-PA intravenous thrombolysis.

2021 Focused update of the 2017 consensus guidelines of the Asia Pacific Heart Rhythm Society (APHRS) on stroke prevention in atrial fibrillation

The consensus of the Asia Pacific Heart Rhythm Society (APHRS) on stroke prevention in atrial fibrillation (AF) has been published in 2017 which provided useful clinical guidance for cardiologists, neurologists, geriatricians, and general practitioners in Asia-Pacific region. In these years, many important new data regarding stroke prevention in AF were reported. The Practice Guidelines subcommittee members comprehensively reviewed updated information on stroke prevention in AF, and summarized them in this 2021 focused update of the 2017 consensus guidelines of the APHRS on stroke prevention in AF. We highlighted and focused on several issues, including the importance of AF Better Care (ABC) pathway, the advantages of non-vitamin K antagonist oral anticoagulants (NOACs) for Asians, the considerations of use of NOACs for Asian patients with AF with single 1 stroke risk factor beyond gender, the role of lifestyle factors on stroke risk, the use of oral anticoagulants during the "coronavirus disease 2019" (COVID-19) pandemic, etc. We fully realize that there are gaps, unaddressed questions, and many areas of uncertainty and debate in the current knowledge of AF, and the physician's decision remains the most important factor in the management of AF.

Retrospective analysis of the effectiveness of a reduced dose of idarucizumab in dabigatran reversal

BACKGROUND

The recommended dose of idarucizumab, the specific reversal agent for dabigatran etexilate, is 5g. However, published data showed biochemical reversal after an initial 2.5g dose.

OBJECTIVES

This study aims to retrospectively compare the clinical effectiveness of 2.5g and 5g doses of idarucizumab used in dabigatran reversal in three hospitals in Auckland, New Zealand.

METHODS

All patients receiving idarucizumab for dabigatran reversal between 1st April 2016 and 31st December 2018 were included. The primary outcome was the likelihood of receiving a second dose of idarucizumab during the same admission. Secondary outcomes included normalisation of coagulation profiles; and 30-day thrombotic, bleeding and mortality rates.

RESULTS

Of 329 patients included, 206 received an upfront 2.5g dose and 123 received a 5g dose. The median age was 78 years and median creatinine clearance was 50mL/min. Most patients (62.6%) required idarucizumab for an urgent procedure, while 37.4% presented with bleeding. A 2.5g dose was not associated with an increased rate of receiving a second dose (OR 0.686, 95% CI 0.225-2.090). A similar proportion of patients in each group achieved a normal APTT (73.8% vs 80.0%, p=0.464) and dTCT (95.9% vs 91.4%, p=0.379) following idarucizumab infusion. There was no increase in the rate of death (OR 0.602, 95% CI 0.292-1.239), thrombosis (OR 0.386, 95% CI 0.107-1.396) or bleeding (OR 0.96, 95% CI 0.27-3.33) in the 2.5g dose group compared to the 5g dose group.

CONCLUSIONS

An initial 2.5g dose of idarucizumab appears effective for dabigatran reversal in the real-world setting.

Acute Stroke Treatment in an Anticoagulated Patient: When Is Thrombolysis an Option?

Purpose of Review

Direct oral anticoagulants (DOACs: the factor Xa inhibitors rivaroxaban, apixaban, and edoxaban and the direct thrombin inhibitor dabigatran) are the mainstay of stroke prevention in patients with non-valvular atrial fibrillation (AF). Nevertheless, there is a residual stroke risk of 1–2% per year despite DOAC therapy. Intravenous thrombolysis (IVT) reduces morbidity in patients with ischemic stroke and improves functional outcome. Prior DOAC therapy is a (relative) contraindication for IVT but emerging evidence supports its use in selected patients.

Recent Findings

Recent observational studies highlighted that IVT in patients on prior DOAC therapy seems feasible and did not yield major safety issues. Different selection criteria and approaches have been studied including selection by DOAC plasma levels, non-specific coagulation assays, time since last intake, and prior reversal agent use. The optimal selection process is however not clear and most studies comprised few patients.

Summary

IVT in patients taking DOAC is a clinically challenging scenario. Several approaches have been proposed without major safety issues but current evidence is weak. A patient-oriented approach balancing potential benefits of IVT (i.e., amount of salvageable penumbra) against expected bleeding risk including appropriate monitoring of anticoagulant activity seem justified.

Dabigatran Etexilate Induces Cytotoxicity in Rat Gastric Epithelial Cell Line via Mitochondrial Reactive Oxygen Species Production

Dabigatran is a novel oral anticoagulant that directly inhibits free and fibrin-bound thrombins and exerts rapid and predictable anticoagulant effects. While the use of this reagent has been associated with an increased risk of gastrointestinal bleeding, the reason why dabigatran use increases gastrointestinal bleeding risk remains unknown. We investigated the cytotoxicity of dabigatran etexilate and tartaric acid, the two primary components of dabigatran. The cytotoxicity of dabigatran etexilate and tartaric acid was measured in a cell viability assay. Intracellular mitochondrial reactive oxygen species (mitROS) production and lipid peroxidation were measured using fluorescence dyes. Cell membrane viscosity was measured using atomic force microscopy. The potential of ascorbic acid as an inhibitor of dabigatran cytotoxicity was also evaluated. The cytotoxicity of dabigatran etexilate was higher than that of tartaric acid. Dabigatran etexilate induced mitROS production and lipid peroxidation and altered the cell membrane viscosity. Ascorbic acid inhibited the cytotoxicity and mitROS production induced by dabigatran etexilate. Therefore, we attributed the cytotoxicity of dabigatran to dabigatran etexilate, and proposed that the cytotoxic effects of dabigatran etexilate are mediated via mitROS production. Additionally, we demonstrated that dabigatran cytotoxicity can be prevented via antioxidant treatment.

Effective Removal of Dabigatran by Idarucizumab or Hemodialysis: A Physiologically Based Pharmacokinetic Modeling Analysis

Background

Application of idarucizumab and hemodialysis are options to reverse the action of the oral anticoagulant dabigatran in emergency situations.

Objectives

The objectives of this study were to build and evaluate a mechanistic, whole-body physiologically based pharmacokinetic/pharmacodynamic (PBPK/PD) model of idarucizumab, including its effects on dabigatran plasma concentrations and blood coagulation, in healthy and renally impaired individuals, and to include the effect of hemodialysis on dabigatran exposure.

Methods

The idarucizumab model was built with the software packages PK-Sim® and MoBi® and evaluated using the full range of available clinical data. The default kidney structure in MoBi® was extended to mechanistically describe the renal reabsorption of idarucizumab and to correctly reproduce the reported fractions excreted into urine. To model the PD effects of idarucizumab on dabigatran plasma concentrations, and consequently also on blood coagulation, idarucizumab-dabigatran binding was implemented and a previously established PBPK model of dabigatran was expanded to a PBPK/PD model. The effect of hemodialysis on dabigatran was implemented by the addition of an extracorporeal dialyzer compartment with a clearance process governed by dialysate and blood flow rates.

Results

The established idarucizumab-dabigatran-hemodialysis PBPK/PD model shows a good descriptive and predictive performance. To capture the clinical data of patients with renal impairment, both glomerular filtration and tubular reabsorption were modeled as functions of the individual creatinine clearance.

Conclusions

A comprehensive and mechanistic PBPK/PD model to study dabigatran reversal has been established, which includes whole-body PBPK modeling of idarucizumab, the idarucizumab-dabigatran interaction, dabigatran hemodialysis, the pharmacodynamic effect of dabigatran on blood coagulation, and the impact of renal function in these different scenarios. The model was applied to explore different reversal scenarios for dabigatran therapy.

Electronic supplementary material

The online version of this article (10.1007/s40262-019-00857-y) contains supplementary material, which is available to authorized users.

Safety of idarucizumab in the reversal of dabigatran at six tertiary care Ontario hospitals

Background

Idarucizumab, a monoclonal antibody fragment that reverses the anticoagulant effect of dabigatran, was approved for use in Canada in 2016.

Objective

Our objective was to assess the safety of idarucizumab among patients who received the drug within the first 3 years of its use in Canada.

Patients/Methods

We performed a retrospective health records review of all idarucizumab use, excluding use in those <18 years of age, between May 16, 2016, and August 1, 2019, at six Ontario tertiary care hospitals. The primary outcome was mortality. The secondary outcomes were in-hospital arterial thrombotic event (ATE), in-hospital venous thromboembolism (VTE), length of hospital stay, and length of critical care stay.

Results

A total of 85 patients received idarucizumab during the study period for the following indications: 37 (43.5%) for spontaneous bleeding, 28 (32.9%) for traumatic bleeding, 11 (12.9%) for emergency surgeries/procedures, 5 (5.9%) for elective surgeries/procedures, and 4 (4.7%) for other indications. Nineteen patients (22.4%; 95% confidence interval [CI], 14.8%-32.3%) did not survive their hospitalization. During hospitalization, two patients (2.4%; 95% CI, 0.7%-8.2%) had ATE, and three patients (3.5%; 95% CI, 1.2%-9.9%) had VTE. The median length of stay was 8 (interquartile range [IQR], 2.5-13) days in hospital and 3 (IQR, 2-5) days in critical care.

Conclusions

Compared with clinical trial data, we found a numerically higher rate of mortality and similar rate of ATE and VTE among patients treated with idarucizumab in the real world.

Development and validation of LC-MS/MS method for simultaneous determination of dabigatran etexilate and its active metabolites in human plasma, and its application in a pharmacokinetic study

Dabigatran is a direct thrombin inhibitor widely used for preventing various thrombotic events. Although there are several established LC-MS/MS based methods for quantification of plasma dabigatran etexilate and its active metabolites (dabigatran and dabigatran acylglucuronide), so far, there are no studies for simultaneous quantification of dabigatran etexilate, dabigatran, and dabigatran acylglucuronide in human plasma samples. In the present study, a novel and sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS) method was developed and validated for assessment of dabigatran pharmacokinetics in human plasma samples according to FDA guidelines. We used the new method to simultaneously quantify dabigatran etexilate, dabigatran, and dabigatran acylglucuronide in human plasma samples. After deproteinization using acetonitrile, the supernatants were evaporated, dissolved in a mobile phase, and finally injected onto an HPLC system with a silica-based C₁₈ reverse-phase column. Mass spectrometer system was operated in multiple reaction monitoring mode (MRM) (dabigatran etexilate: m/z 629.464→290.100; dabigatran: m/z 472.300→289.100, and dabigatran acylglucuronide: m/z 648.382→289.100) and all the components were confirmed using positive electrospray ionization (ESI). Correlation coefficients > 0.999 were achieved for all the calibration curves with linear regression. The intra-day and inter-day accuracies of dabigatran etexilate, dabigatran, and dabigatran acylglucuronide were 95.84-109.44 %, 99.4-103.42 %, and 98.37-104.42 %, respectively, while their corresponding precisions were 3.84-9.79, 1.07-8.76 %, and 2.56-4.51 %, respectively. We successfully applied the new method to determine the pharmacokinetic profiles of dabigatran etexilate, dabigatran, and dabigatran acylglucuronide in humans. Our findings demonstrated the method as robust, reliable, and sensitive.

Idarucizumab for dabigatran reversal in cardiac tamponade complicating percutaneous intervention in ST elevation myocardial infarction

An 83-year-old man with a history of permanent atrial fibrillation (AF) anticoagulated by dabigatran 150 b.i.d., type 2 diabetes mellitus, and hypertension was admitted to the hospital with a diagnosis of ST-elevation myocardial infarction (STEMI). The patient was loaded with 300 mg of aspirin p.o., 5000 IU of unfractionated heparin i.v. and 600 mg of clopidogrel and was transferred to the catheterization laboratory. Coronary angiography demonstrated left anterior descending artery (LAD) occlusion. During the LAD angioplasty a dissection of a distal part of the LAD and the blood extravasation to the pericardium occurred (Figure 1 A). Idarucizumab 2 × 2.5 g i.v. was administered and the inflated balloon maintained at the site of coronary perforation. About 10 min after the end of idarucizumab infusion, the balloon was deflated and the patient presented with clinical symptoms of cardiac tamponade such as blood pressure decrease and tachycardia. The echocardiographic assessment revealed up to 16 mm accumulation of pericardial fluid (Figure 2 A). Immediately the covered stent was implanted (Papyrus, Biotronik) and the pericardiocentesis was carried out. 320 ml of blood was finally drained. Control contrast injection revealed a covered perforating zone with no contrast extravasation (Figure 1 B). The echocardiographic control revealed pericardial effusion less than 5 mm (Figure 2 B). The patient was stable with a blood pressure of 130/80 mm Hg, a heart rate of 100–130/min (AF), and without chest pain. No significant reduction in the red blood cell count was observed. Antiplatelet therapy was given consisting of aspirin and clopidogrel. In the following days enoxaparin was introduced and finally changed to dabigatran 110 mg b.i.d.

The in vitro addition of idarucizumab to plasma samples from patients increases thrombin generation

Dabigatran interferes with many coagulation tests. To overcome this obstacle the use of idarucizumab as an in vitro antidote to dabigatran has been proposed. The aim of this study was to test the effect of idarucizumab as an in vitro antidote to dabigatran in ex vivo plasma samples from routine clinical patients examined by a thrombin generation assay (TGA). From 44 patients with atrial fibrillation five blood samples were collected. Thrombin generation was measured in all samples before and after the addition of idarucizumab. When idarucizumab was added to baseline plasma (no dabigatran), it caused a significantly shorter Lag Time and Time to Peak Thrombin, and a higher Peak Thrombin and Endogenous Thrombin Potential (ETP) of TGA. Similar results were obtained when idarucizumab was added to dabigatran-containing plasma, with TGA parameters comparable to baseline + idarucizumab plasma, but not to baseline plasma. In summary, our study showed that in vitro addition of idarucizumab to plasma samples from patients increases thrombin generation. The use of idarucizumab to neutralize dabigatran in patient plasma samples as well as the clinical relevance of in vitro increased thrombin generation induced by idarucizumab needs further investigation.

Idarucizumab (Praxbind®) for dabigatran reversal in patients undergoing heart transplantation: a cohort of ten patients

Background

Novel oral anticoagulants are used in atrial fibrillation. Idarucizumab has been approved for reversal of dabigatran in situations of life-threatening hemorrhage or emergency surgery.

Objectives

We report a single center experience of ten patients on dabigatran therapy who were given idarucizumab prior to heart transplantation.

Methods & results

The mean plasma concentration of dabigatran prior to reversal was 139 ± 89 ng/ml. Hemoglobin, hematocrit and platelet levels were decreased after surgery. Surgical procedures were successfully performed with no increased risk, especially regarding bleeding complications. All patients were alive after 90 days.

Conclusion

Dabigatran reversal with idarucizumab in contexts of emergency surgery/urgent procedures is an attractive and safe option to be taken into consideration for patients with end stage heart disease awaiting transplantation and indication of anticoagulant therapy.

A chemometric comparison of different models in fluorescence analysis of dabigatran etexilate and dabigatran

In this paper, a simple, rapid, low-cost and potential method was established for the simultaneous quantitative analysis of dabigatran etexilate (DABE) and dabigatran (DAB) in spiked biological fluids. It combined excitation-emission matrix fluorescence (EEMF) with different second-order calibration methods, including the self-weighted alternating normalized residue fitting (SWANRF) algorithm based on trilinear decomposition model, the multivariate curve resolution - alternating least-squares (MCR-ALS) based on bilinear decomposition model and the unfolded partial least-square coupled with residual bilinearization (U-PLS/RBL) based on latent variables model. The proposed method showed "second-order advantage", that is, satisfactory quantitative results were successfully obtained even in the presence of unknown interferences and serious spectral overlap. The recoveries of DABE and DAB in spiked biological fluids were 91.7%-101.7% for SWANRF, 95.9%-117.8% for MCR-ALS, 83.0%-109.6% for U-PLS/RBL, respectively. Figures of merit and other statistical parameters were also calculated to assess the performance of the proposed method. Moreover, the modeling procedures and characteristics of three different models in EEMF analysis were discussed and compared.

Direct oral anticoagulants: a review on the current role and scope of reversal agents

New guideline recommendations prefer direct oral anticoagulants (DOACs) over warfarin in DOAC-eligible patients with atrial fibrillation and patients with venous thromboembolism. As expected with all antithrombotic agents, there is an associated increased risk of bleeding complications in patients receiving DOACs that can be attributed to the DOAC itself, or other issues such as acute trauma, invasive procedures, or underlying comorbidities. For the majority of severe bleeding events, the widespread approach is to withdraw the DOAC, then provide supportive measures and "watchful waiting" with the expectation that the bleeding event will resolve with time. However, urgent reversal of anticoagulation may be advantageous in patients with serious or life-threatening bleeding or in those requiring urgent surgery or procedures. Until recently, the lack of specific reversal agents, has affected the uptake of these agents in clinical practice despite a safer profile compared to warfarin in clinical trials. In cases of life-threatening or uncontrolled bleeding or when patients require emergency surgery or urgent procedures, idarucizumab has been recently approved for reversal of anticoagulation in dabigatran-treated patients and andexanet alfa for factor Xa inhibitor-treated treated patients. The current review summarizes the current clinical evidence and scope of these agents with the potential impact on DOAC use in clinical practice.

An engineered factor Va prevents bleeding induced by direct-acting oral anticoagulants by different mechanisms

Control of bleeding with direct-acting oral anticoagulants (DOACs) remains an unmet clinical need. Activated superFactor V (superFVa) is an engineered activated protein C (APC)-resistant FVa variant with enhanced procoagulant activity resulting from an A2/A3 domain disulfide bond and was studied here for control of DOAC-induced bleeding. SuperFVa reversed bleeding induced by FXa inhibitors (rivaroxaban, apixaban), and the FIIa inhibitor dabigatran in BalbC mice. The blocking anti-protein C and APC [(A)PC] antibody SPC-54 also reduced FXa inhibitor induced bleeding similar to superFVa, whereas dabigatran-induced bleeding was not affected. This indicated that sufficient APC was generated to contribute to bleeding in the presence of FXa inhibitors, but not in the presence of dabigatran, suggesting that mechanisms contributing to bleeding differed for FXa and FIIa inhibitors. Despite different mechanisms contributing to bleeding, superFVa effectively reduced bleeding for all DOACs, indicating the versatility of superFVa's properties that contribute to its universal prohemostatic effects for DOAC associated bleeding. Supported by thrombin generation assays on endothelial cells in normal plasma spiked with DOACs and patient plasma anticoagulated with DOACs, 3 complementary mechanisms were identified by which superFVa achieved DOAC class-independent prohemostatic efficiency. These mechanisms are resistance to inactivation by APC, overcoming the FV activation threshold, and maximizing the efficiency of the prothrombinase complex when the available FXa is increased by FVIIa-based prohemostatics. In summary, it is this versatility of superFVa that delineates it from other prohemostatic agents as a promising class-independent rescue agent in bleeding situations associated with DOACs.

Dabigatran Reversal With Idarucizumab Preceding Thrombolysis in an Octogenarian Patient with Chronic Kidney Disease and Acute Stroke: A Case Report

BACKGROUND AND PURPOSE

Reversing the effect of dabigatran among patients with atrial fibrillation is important to normalize coagulation profile among patients who develop serious hemorrhage from any source. However, such intervention always has the potential to cause a prothrombotic state. Among patients suspected of ischemic stroke, Idarucizumab, may be administered preceding thrombolysis. This is a considerable option when given during the critical phase of revascularization.

METHODS

We report the case of an 84-year old, male, banker, known hypertensive with chronic renal disease. He has non valvular atrial fibrillation receiving Dabigatran at 75 mg twice daily and presented with symptoms of right-sided weakness, right hemisensory loss, facial asymmetry, and slurring of speech equating to National Institute of Health Stroke Scale (NIHSS) of 5. After coming into the hospital for a suspected stroke, 3 hours and 25 minutes after symptoms, complete reversal of Dabigatran with Idarucizumab was administered and intravenous thrombolysis was initiated 271 minutes post ictus. There was immediate improvement of the right upper extremity weakness and dysarthria 30 minutes post infusion. At 13 days post ictus, the patient was discharged with minimal right central facial palsy and right arm drift (NIHSS 2). Brain CT scan post revascularization did not reveal any hemorrhage and anticoagulant Apixaban 2.5 mg twice daily was started and maintained thereafter. Brain Magnetic Resonance Angiogram (MRA) showed complete recanalization of the left proximal MCA after 52 days.

CONCLUSION

Our case showed the effectiveness and safety of giving Idarucizumab followed by thrombolysis in Dabigatran-treated atrial fibrillation with ischemic stroke. Based on this case, the procedure can be performed in an elderly population with chronic kidney disease when administered close to the limit of threshold for thrombolysis.

A Review on the Use of Reversal Agents of Direct Oral Anticogulant Drugs in Case of Gastrointestinal Bleeding

BACKGROUND

Major bleeding is a life-threatening condition and a medical emergency with high mortality risk. It is often the complication of anticoagulant's intake. Anticoagulants are commonly used for the prevention and treatment of thrombotic events. The standard therapy with vitamin K antagonist (warfarin) has been frequently replaced by direct oral anticoagulants (DOACs). The latter agents (rivaroxaban, apixaban, edoxaban, dabigatran, and betrixaban) showed better efficacy and safety compared to standard warfarin treatment and they are recommended for the reduction of ischemic stroke. Literature data reported a high risk of gastrointestinal bleeding with DOACs, in particular with dabigatran and rivaroxaban. In case of life-threatening gastrointestinal bleeding, these patients could benefit from the use of reversal agents.

METHODS

We performed an electronic search on PUBMED of the literature concerning reversal agents for DOACs and gastrointestinal bleeding in the Emergency Department from 2004 to 2020.

AIM

This review summarizes the current evidence about three reversal agents idarucizumab, andexanet alfa and ciraparantag, and the use of the first two in the emergency setting in patients with active major bleeding or who need urgent surgery which physicians indicate for a better management approach in order to increase patient's safety.

CONCLUSION

Although these agents have been marketed for five years (idarucizumab) and two years (andexanet alfa) respectively, and despite guidelines considering antidotes as first-line agents in treating life-threatening hemorrhage when available, these antidotes seem to gain access very slowly in the clinical practice. Cost, logistical aspects and need for plasma level determination of DOAC for an accurate therapeutic use probably have an impact on this phenomenon.. An expert multidisciplinary bleeding team should be established so as to implement international guidelines based on local resources and organization.

Andexanet Alfa and its Clinical Application

Factor Xa (FXa) inhibitors are widely used for stroke prevention in patients with nonvalvular atrial fibrillation, and for the treatment and prevention of deep venous thrombosis and pulmonary embolism. Compared with warfarin, individual FXa inhibitors are associated with a lower risk of major bleeding. Nevertheless, bleeding remains a feared complication of any anticoagulant therapy. Despite their demonstrated safety, implementation of FXa inhibitors in clinical practice may have been limited by the lack of a specific antidote. Recently, however, the United States Food and Drug Administration and the European Medicines Agency approved andexanet alfa for reversal of anticoagulation in patients treated with rivaroxaban or apixaban who have life-threatening or uncontrolled bleeding. This review will discuss andexanet alfa's mode of action, indication for use and efficacy, with a focus on its appropriate use in clinical practice. Unnecessary usage should be prevented as this may compromise patient safety. Assessment of potentially suitable patients by a multidisciplinary team, use according to the institutional protocol and central storage, all contribute to proper use of andexanet alfa. A practical tool to direct appropriate use of andexanet alfa is proposed.

Idarucizumab for Emergency Reversal of Anticoagulant Effects of Dabigatran: Interim Results of a Japanese Post-Marketing Surveillance Study

INTRODUCTION

Idarucizumab, a monoclonal antibody fragment, was developed to reverse the anticoagulant effect of dabigatran, and it was approved in Japan in September 2016. An all-case post-marketing surveillance is ongoing to collect data in Japanese patients treated with idarucizumab who had serious bleeding (Group A) or required an urgent procedure (Group B).

METHODS

The primary endpoint was the incidence of adverse drug reactions (ADRs). The secondary endpoint was the maximum extent of reversal of the anticoagulant effect of dabigatran based on activated partial thromboplastin time (aPTT) within 4 h after idarucizumab administration.

RESULTS

This interim analysis included 262 patients who received idarucizumab. Eighteen patients (6.9%) experienced ADRs within 4 weeks. The reversal effect of idarucizumab based on aPTT within 4 h after idarucizumab administration was assessed in 30 patients and the median maximum percentage reversal was 100%. In Group A, the median time to bleeding cessation in patients without intracranial bleeding was 3.3 h. In Group B, normal intraoperative hemostasis was reported in 63 patients (72.4%).

CONCLUSIONS

The results of this interim analysis suggest that idarucizumab is safe and effective for the reversal of dabigatran in Japanese patients in a real-world setting, and support the continued use of idarucizumab.

TRIAL REGISTRATION

ClinicalTrials.gov identifier, NCT02946931.