Restarting Dabigatran Etexilate 24 h After Reversal With Idarucizumab and Redosing Idarucizumab in Healthy Volunteers

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.

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.

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.

Current status of oral anticoagulant reversal strategies: a review

Utilization of direct oral anticoagulants (DOAC) have steadily increased since their approval and are now recommended over warfarin for both stroke prevention in nonvalvular atrial fibrillation and treatment of venous thromboembolism (VTE). With increased DOAC use, the number of major bleeding events requiring medical intervention will continue to rise. Until 2015, warfarin maintained an advantage as the only oral anticoagulant with a specific reversal agent. Since then, idarucizumab has been approved for dabigatran reversal and recently, andexanet alfa was granted approval for the reversal of apixaban or rivaroxaban in patients with life-threatening or uncontrolled bleeding events. Due to the manufacturing practices required to yield these reversal therapies, they are available at high cost to hospital systems and as a result, have been met with resistance. Data exists describing both prothrombin complex concentrates (PCC) and andexanet alfa for DOAC reversal, however, without head-to-head comparison. Until future studies are available, current literature must be critically evaluated to aid in the clinical decision-making process of how to treat patients with life-threatening DOAC-related bleeding.

Specific Antidotes for Direct Oral Anticoagulants in Life-Threatening Bleeding

Review presents data on medicines from the new group of cardiovascular drugs, direct oral anticoagulants (DOACs) inhibitors, as antidotes for DOAC when stopping life-threatening bleeding. DOAC therapy is accorded by hemorrhages with lower frequency than therapy by indirect anticoagulants, but really exist. New antidotes for DOACs are idarucizumab, andexanet, ciraparantag. The need in antidotes for DOAC may suddenly appear in spontaneous bleeding, during surgical operation, invasive procedure, due to trauma, in patients with stroke, kidney or liver failure. Data is given on the frequency of the main types of bleeding while taking new oral anticoagulants. Information concerning use of antidotes for DOACs in bleedings as well as use of non-specific therapy are reviewed.

 

A Single-Agent Dual-Specificity Targeting of FOLR1 and DR5 as an Effective Strategy for Ovarian Cancer

Therapeutic antibodies targeting ovarian cancer (OvCa)-enriched receptors have largely been disappointing due to limited tumor-specific antibody-dependent cellular cytotoxicity. Here we report a symbiotic approach that is highly selective and superior compared with investigational clinical antibodies. This bispecific-anchored cytotoxicity activator antibody is rationally designed to instigate "cis" and "trans" cytotoxicity by combining specificities against folate receptor alpha-1 (FOLR1) and death receptor 5 (DR5). Whereas the in vivo agonist DR5 signaling requires FcγRIIB interaction, the FOLR1 anchor functions as a primary clustering point to retain and maintain a high level of tumor-specific apoptosis. The presented proof of concept study strategically makes use of a tumor cell-enriched anchor receptor for agonist death receptor targeting to potentially generate a clinically viable strategy for OvCa.

Approaches to Direct Oral Anticoagulant Selection in Practice

Direct oral anticoagulants (DOACs) carry many advantages over warfarin and are now considered first line or an alternative for mnay thromboembolic disorders. With the emergence of 5 DOAC agents to the market as well as the accumulating evidence gathered from head-to-head comparisons between the agents, we attempt to provide direction for clinicians when selecting the most appropriate DOAC agent. Important aspects such as efficacy, safety, cost effectiveness, approved indications, and other drug-related factors will be addressed to highlight the major similarities and diversities among the DOACs. When considering the safety profile of DOACs, evidence points toward apixaban as the safest followed by dabigatran and then rivaroxaban. On the other hand, dabigatran currently has the only approved antidote, idarucizumab. According to the approved DOAC indications, rivaroxaban may be favorable in European countries given its additional indication for secondary prevention of myocardial infarction. Following rivaroxaban, dabigatran and apixaban have the largest number of approved indications and lastly comes edoxaban and then betrixaban. For patients with renal impairment, betrixaban is the safest option, followed by apixaban and edoxaban, then rivaroxaban and lastly dabigatran. When considering DOAC dosing, rivaroxaban, edoxaban, and betrixaban are mainly dosed once daily compared to dabigatran and apixaban, which are dosed twice daily. However, rivaroxaban and betrixaban must be administered with food, which adds another level of complexity to the DOAC dosing. Lastly, taking into consideration drug interactions, dabigatran, edoxaban, and betrixaban have the least amount of interactions compared to apixaban and rivaroxaban. Each DOAC has its own set of features that makes it better suited than others based on the exact clinical situation. Therefore, no conclusion can be drawn to the most superior DOAC based on the aspects discussed in this review.

Reversal Strategies for Newer Oral Anticoagulants

Nonvitamin K antagonist oral anticoagulants have advantages compared with warfarin, but both types of anticoagulants come with uncertainty about how best to manage life-threatening bleeding events, urgent surgeries, and invasive procedures. Nurse practitioners and physician assistants may need to manage such emergency situations in the critical care setting. Achieving hemostasis quickly is key, and efforts to do so have relied mainly on blood products. Targeted reversal agents are in clinical development and one, idarucizumab, which reverses dabigatran anticoagulation, has been approved. Current options for managing events and urgent procedures in anticoagulated patients are discussed in this article, with a focus on specific reversal agents.

[Management of hemorrhage in patients treated with direct oral anticoagulants]

The introduction of nonvitamin K antagonistic, direct oral anticoagulants (DOAC) made thromboembolic prophylaxis easier for patients. For many physicians, however, there is still uncertainty about monitoring, preoperative discontinuation, and restarting of DOAC therapy. Guidelines for the management of bleeding are provided, but require specific therapeutic skills in the management of diagnostics and therapy of acute hemorrhage. Small clinical studies and case reports indicate that unspecific therapy with prothrombin complex concentrates (PCC) and activated PCC (aPCC) concentrate may reverse DOAC-induced anticoagulation. However, PCC or aPCC at higher doses potentially provoke thromboembolic complications. However, idarucizumab, a specific, fast-acting, antidote for dabigatran, provides immediate and sustained reversal with no intrinsic or prohemostatic activity. This review article provides an overview of the pharmacology and potential risk of DOAC and the management in the perioperative period with a focus of current concepts in the treatment of DOAC-associated bleeding.

Reversal Strategies for Intracranial Hemorrhage Related to Direct Oral Anticoagulant Medications

Direct oral anticoagulants (DOACs) are a new class of anticoagulants that directly inhibit either thrombin or factor Xa in the coagulation cascade. They are being increasingly used instead of warfarin or other vitamin K antagonists (VKAs). Adverse side effects of DOACs may result in hemorrhagic complications, including life-threatening intracranial hemorrhage (ICH), though to a much lesser degree than VKAs. Currently there are relatively limited indications for DOACS but their usage is certain to expand with the availability of their respective specific reversal agents. Currently, only idarucizumab (antidote for dabigatran) has been United States Food and Drug Administration- (FDA-) approved, but others (andexanet-α and ciraparantag) may be approved in near future, and the development and availability of such reversal agents have the potential to dramatically change the current anticoagulant use by providing reversal of multiple oral anticoagulants. Until all the DOACs have FDA-approved reversal agents, the treatment of the dreaded side effects of bleeding is challenging. This article is an attempt to provide an overview of the management of hemorrhage, especially ICH, related to DOAC use.

The Renal Elimination Pathways of the Dabigatran Reversal Agent Idarucizumab and its Impact on Dabigatran Elimination

Idarucizumab, a humanized monoclonal antibody fragment (Fab), provides rapid and sustained reversal of dabigatran-mediated anticoagulation. Idarucizumab and dabigatran are mainly eliminated via the kidneys. This analysis aimed to characterize the renal elimination of idarucizumab and investigate the influence of idarucizumab on the pharmacokinetics (PK) of dabigatran and vice versa. Studies were conducted in 5/6 nephrectomized rats, in human volunteers with and without renal impairment, and in a porcine liver trauma model. In both rats and humans, renal impairment increased idarucizumab exposure and initial half-life but did not affect its terminal half-life. Urinary excretion of unchanged idarucizumab increased with increasing idarucizumab dose, suggesting saturation of renal tubular reuptake processes at higher doses. The PK of idarucizumab was unaffected by dabigatran. In contrast, idarucizumab administration resulted in redistribution of dabigatran to the plasma, where it was bound and inactivated by idarucizumab. Urinary excretion of dabigatran after administration of idarucizumab was delayed, but total dabigatran excreted in urine was unaffected. Idarucizumab and dabigatran were eliminated together via renal pathways.

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.

The Use of Idarucizumab for Dabigatran Reversal in Clinical Practice: A Case Series

PURPOSE

To describe the use of idarucizumab (Praxbind, Boehringer Ingelheim) in routine clinical practice at a large urban academic medical center.

SUMMARY

Seven total doses of idarucizumab were administered to six unique patients from October 31, 2015, to October 31, 2016. The reversal agent was used in conjunction with local bleeding control measures, blood product transfusions, and acid-suppressive therapy. In 86% of cases, idarucizumab administration resulted in a successful cessation of bleeding by clinical assessment. Two patients expired due to coexisting conditions. Idarucizumab was administered to patients with normal baseline coagulation tests in 43% of cases. No adverse reactions related to idarucizumab were reported.

CONCLUSIONS

Idarucizumab administration resulted in successful resolution of bleeding by clinical assessment. The therapy for acute bleeding with use of dabigatran (Pradaxa, Boehringer Ingelheim) remains supportive care, in addition to idarucizumab in cases of severe or uncontrolled bleeding. Development of institution-specific protocols and better guidance for using baseline coagulation tests are needed.

Effect of Age and Renal Function on Idarucizumab Pharmacokinetics and Idarucizumab-Mediated Reversal of Dabigatran Anticoagulant Activity in a Randomized, Double-Blind, Crossover Phase Ib Study

BACKGROUND AND OBJECTIVES

Idarucizumab is an antibody fragment that specifically reverses dabigatran-mediated anticoagulation. Safety, pharmacokinetics and pharmacodynamics of idarucizumab were investigated in dabigatran-treated, middle-aged, elderly and renally impaired volunteers with characteristics similar to patients receiving anticoagulant therapy.

METHODS

In this randomized, double-blind, crossover study, 46 subjects (12 middle-aged, 45-64 years; 16 elderly, 65-80 years; and 18 with mild or moderate renal impairment) received dabigatran etexilate (DE; 220 or 150 mg twice daily) for 4 days. Idarucizumab doses of 1, 2.5 and 5 g or 2 × 2.5 g 1 h apart, or placebo, were administered as a rapid (5 min) infusion ~2 h after DE at steady state.

RESULTS

Dabigatran-prolonged diluted thrombin time, ecarin clotting time and activated partial thromboplastin time were reversed to baseline immediately after idarucizumab infusion in all groups. Reversal was sustained with doses ≥2.5 g. Idarucizumab was well tolerated under all conditions. No impact of age on idarucizumab pharmacokinetics was observed; however, subjects with mild or moderate renal impairment demonstrated increased exposure (up to 84 %), decreased clearance and prolonged (by up to 49 %) initial half-life of idarucizumab compared with healthy middle-aged subjects.

CONCLUSIONS

Impaired renal function was associated with increased exposure and decreased clearance of idarucizumab. Idarucizumab resulted in immediate, complete and sustained reversal of dabigatran anticoagulant activity, and was safe and well tolerated in middle-aged, elderly and renally impaired volunteers. The results support the clinical use of a 5 g dose of idarucizumab.

CLINICAL TRIAL REGISTRATION

http://www.clinicaltrials.gov . Unique identifier: NCT01955720.

Drug therapy in anticoagulation: which drug for which patient?

Four non-vitamin K oral anticoagulants (NOACs) are now licensed and available in the UK, offering unprecedented choices in anticoagulant therapy for clinicians and patients. NOACs have many clear benefits over warfarin, the most striking being the reduction in intracranial haemorrhage. However, a number of uncertainties remain: their efficacy in certain situations, utility of drug assays, significance of drug interactions and management of bleeding. In the absence of any direct comparative trials, it is not clear that any of the NOACs is significantly better than the others in any of the licensed indications. The differential activities, pharmacokinetics, metabolism, excretion and side effects of the agents should be considered when selecting the most appropriate anticoagulant. In this article, we discuss how, with careful selection for the relevant indication, NOACs can simplify therapy while improving outcomes. We aim to provide clinicians with the information needed to select the most suitable anticoagulant drug for an individual patient in a given situation.

Evaluation of the immunogenicity of the dabigatran reversal agent idarucizumab during Phase I studies

Aims

Idarucizumab, a humanized monoclonal anti‐dabigatran antibody fragment, is effective in emergency reversal of dabigatran anticoagulation. Pre‐existing and treatment‐emergent anti‐idarucizumab antibodies (antidrug antibodies; ADA) may affect the safety and efficacy of idarucizumab. This analysis characterized the pre‐existing and treatment‐emergent ADA and assessed their impact on the pharmacokinetics and pharmacodynamics (PK/PD) of idarucizumab.

Methods

Data were pooled from three Phase I, randomized, double‐blind idarucizumab studies in healthy Caucasian subjects; elderly, renally impaired subjects; and healthy Japanese subjects. In plasma sampled before and after idarucizumab dosing, ADA were detected and titrated using a validated electrochemiluminescence method. ADA epitope specificities were examined using idarucizumab and two structurally related molecules. Idarucizumab PK/PD data were compared for subjects with and without pre‐existing ADA.

Results

Pre‐existing ADA were found in 33 out of 283 individuals (11.7%), seven of whom had intermittent ADA. Titres of pre‐existing and treatment‐emergent ADA were low, estimated equivalent to <0.3% of circulating idarucizumab after a 5 g dose. Pre‐existing ADA had no impact on dose‐normalized idarucizumab maximum plasma levels and exposure and, although data were limited, no impact on the reversal of dabigatran‐induced anticoagulation by idarucizumab. Treatment‐emergent ADA were detected in 20 individuals (19 out of 224 treated [8.5%]; 1 out of 59 received placebo [1.7%]) and were transient in ten. The majority had specificity primarily toward the C‐terminus of idarucizumab. There were no adverse events indicative of immunogenic reactions.

Conclusion

Pre‐existing and treatment‐emergent ADA were present at extremely low levels relative to the idarucizumab dosage under evaluation. The PK/PD of idarucizumab appeared to be unaffected by the presence of pre‐existing ADA.

Reversing the anticoagulation effects of dabigatran

The standard of care for oral anticoagulation therapy has primarily been warfarin, which is limited by its indirect mechanism-of-action, variable kinetics, tolerability, and routine monitoring concerns. The direct-acting oral anticoagulants (DOACs) have predictable pharmacokinetics and pharmacodynamics, and improved safety and efficacy compared to warfarin for the prevention of stroke in patients with nonvalvular atrial fibrillation and prevention or management of venous thromboembolism. Consequential bleeding is a concern with all anticoagulants. Vitamin K is not a rapid reversal agent for warfarin; rather it facilitates synthesis of new vitamin K-dependent clotting factors, which can take longer than 24 h. Other nonspecific agents, including recombinant activated factor VII, three- and four-factor prothrombin complex concentrates (PCC), and activated PCC or Factor Eight Inhibitor Bypassing Activity (FEIBA®), are options based on clinical need. Specific agents to quickly reverse the effects of DOACs have been under development, and idarucizumab, a monoclonal antibody fragment that rapidly binds dabigatran, has been approved for clinical use in cases of dabigatran-related life-threatening bleeding, or if a dabigatran-treated patient needs emergency surgery or an invasive procedure. Idarucizumab specifically and rapidly reverses dabigatran-induced anticoagulation as measured by established coagulation assays. However, this does not guarantee complete hemostasis, especially if a patient has underlying comorbidities such as renal or liver disease, or has experienced recent trauma that requires urgent surgery. In these cases, concomitant supportive therapy and/or administration of concentrated clotting factors may be considered. Emerging data from ongoing trials and clinical experience will further inform providers regarding optimal approaches for anticoagulation reversal.

Reversal of direct oral anticoagulants: a practical approach

Direct oral anticoagulants (DOACs) have at least noninferior efficacy compared with other oral anticoagulants and have ancillary benefits, including overall better safety profiles, lack of the need for routine monitoring, rapid onset of action, and ease of administration. Reversal of these agents may be indicated in certain situations such as severe bleeding and for perioperative management. DOAC-associated bleeding should be risk stratified: patients with moderate or severe bleeding should have the DOAC discontinued and reversal strategies should be considered. Laboratory testing has limited utility in the acute management of bleeding; thrombin time and activated partial thromboplastin time may be useful for excluding clinically relevant levels of dabigatran. Prothrombin time is potentially useful for rivaroxaban and edoxaban, but calibrated anti-Xa assays are optimal for determining clinically relevant levels of factor Xa inhibitors. Because specific reversal agents are not widely available, supportive care and interventions for local hemostasis remain the cornerstones of therapy in the patient with DOAC-associated bleeding. Nonspecific reversal agents should be considered only in the event of severe bleeding because their efficacy is unknown, and they are associated with risk of thrombosis. Recent results from phase 3/4 studies demonstrate efficacy for an antidote to dabigatran (idarucizumab, a monoclonal antibody fragment with specificity for dabigatran) and an antidote to factor Xa inhibitors (andexanet alfa, a recombinant and inactive form of factor Xa that binds inhibitors). A universal reversal agent (ciraparantag) for many anticoagulants, including the DOACs, shows promise in results from phase 1 and 2 studies.

Idarucizumab, a Specific Reversal Agent for Dabigatran: Mode of Action, Pharmacokinetics and Pharmacodynamics, and Safety and Efficacy in Phase 1 Subjects

The direct oral anticoagulants (DOACs) provide a number of clinical advantages over vitamin K antagonists for the treatment of thromboembolism, including improved efficacy and safety, as well as no need for regular monitoring of anticoagulant effect. However, as with all anticoagulants, bleeding complications may occur, and anticoagulant reversal may be required in specific clinical situations, such as in patients experiencing spontaneous or traumatic bleeds, or in anticoagulated patients requiring emergency surgery or other invasive procedures. Therefore, several reversal agents for the DOACs are in development. This includes the specific reversal agent idarucizumab, which has been approved by the U.S. Food and Drug Administration and the European Medicines Agency for use in patients treated with dabigatran when urgent reversal of its anticoagulant effects is needed. Idarucizumab is a humanized monoclonal antibody fragment that binds with high affinity to free and thrombin-bound dabigatran, resulting in an almost irreversibly bound idarucizumab-dabigatran complex and thereby neutralizing dabigatran's anticoagulant activity. The reversal of the anticoagulant effects of dabigatran by idarucizumab has been demonstrated in animal bleeding models, in healthy volunteers with a range of ages and renal function, and in anticoagulated patients. In the phase 1 trials, at doses of 2 g or greater, idarucizumab resulted in immediate and complete reversal of the dabigatran anticoagulant effects and was well tolerated. In the absence of dabigatran, idarucizumab showed no effect on coagulation parameters or thrombin formation. These findings provide initial evidence that idarucizumab could provide a safe and effective means of reversing anticoagulant activity in patients treated with dabigatran in need of emergency surgery or in emergency bleeding situations.

Idarucizumab and Factor Xa Reversal Agents: Role in Hospital Guidelines and Protocols

As expected with all antithrombotic agents, there is a risk of bleeding complications in patients receiving direct oral anticoagulants (DOACs) because of the DOAC itself, acute trauma, invasive procedures, or underlying comorbidities. For many bleeding events, a prudent course of action will be to withdraw the DOAC, then "wait and support" the patient, with the expectation that the bleeding event should resolve with time. Likewise, DOAC therapy may be interrupted ahead of a planned procedure, the stopping time being dependent on the agent involved and the patient's renal function. However, urgent reversal of anticoagulation is required in patients with serious or life-threatening bleeding or in those requiring urgent surgery or procedures. Novel specific reversal agents, either under development or recently approved, will need to be incorporated into local anticoagulation reversal protocols. For dabigatran-treated patients, idarucizumab recently has been approved for clinical use in cases of life-threatening or uncontrolled bleeding or when patients require emergency surgery or urgent procedures, both associated with a high risk of bleeding. As clinical experience with individual specific reversal agents grows, their roles in managing major bleeding events in DOAC-treated patients will become better defined. Future research, as well as ongoing use of idarucizumab, should help establish when it is appropriate to re-dose with idarucizumab, co-administer with prothrombin complex concentrates, or re-initiate DOAC after idarucizumab use. Ongoing trials should help identify the appropriate doses and expected durations of effect for andexanet alfa and ciraparantag, which are likely to vary depending on the individual oral anticoagulants.

Idarucizumab: A Review as a Reversal Agent for Dabigatran

Idarucizumab (Praxbind(®)), a humanized monoclonal antibody, is a specific reversal agent for the direct oral thrombin inhibitor dabigatran, available as its prodrug dabigatran etexilate (Pradaxa(®)). Idarucizumab is approved in several countries (including the USA, the EU, Canada and Australia) for use in adult patients on dabigatran when the reversal of its anticoagulant effects is required for emergency surgery/procedures or in the event of life-threatening or uncontrolled bleeding. In the ongoing pivotal RE-VERSE AD trial in these populations (n = 90), intravenous idarucizumab 5 g reversed dabigatran-induced prolongation of dilute thrombin time (dTT) and ecarin clotting time (ECT) within minutes. The median maximum percentage reversal was 100 % for both assays (primary endpoint). Idarucizumab normalized dTT and ECT in 88-98 % of patients who had elevated levels at baseline. After idarucizumab administration, bleeding stopped in 97 % of evaluable patients in the bleeding cohort within 24 h (median time to cessation of bleeding was 11.4 h), and the rate of normal intraoperative haemostasis was 92 % in the surgical cohort. Idarucizumab was generally well tolerated. In conclusion, idarucizumab is a unique and specific treatment option for the reversal of the anticoagulant effects of dabigatran in adult patients requiring emergency procedures or in the event of life-threatening or uncontrolled bleeding.

Dabigatran approaching the realm of heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia (HIT) is a serious, immune mediated complication of exposure to unfractionated or low-molecular-weight heparin. Though rare, it is a condition associated with high morbidity and mortality that requires immediate change to alternative anticoagulants for the prevention of life-threatening thrombosis. The direct thrombin inhibitors lepirudin and argatroban are currently licensed for the treatment of HIT. Dabigatran, a novel oral anticoagulant (NOAC) with a similar mechanism of action and effective use in other indications, has recently been proposed as another therapeutic option in cases of HIT. This review serves as an introduction to using dabigatran for this purpose, detailing the clinical aspects of its administration, evidence of its performance compared to other anticoagulants, and the preliminary reports of HIT successfully treated with dabigatran. As the literature on this develops, it will need to include clinical trials that directly evaluate dabigatran against the other NOACs and current treatment options.