Rivaroxaban reversal with prothrombin complex concentrate or tranexamic acid in healthy volunteers

Essentials Specific reversal agents for managing severe factor Xa inhibitor-associated bleeding are lacking. We assessed 4-factor-prothrombin complex concentrate (4F-PCC) and tranexamic acid (TXA). 4F-PCC, but not TXA, reduced the prothrombin time and increased endogenous thrombin potential. These agents may be viable options for reversal of therapeutic doses of rivaroxaban.

SUMMARY

Background Oral activated factor X inhibitors such as rivaroxaban are widely used, but specific reversal agents are lacking. Although four-factor prothrombin complex concentrate (4F-PCC) and tranexamic acid (TXA) are sometimes used to manage serious bleeding, their efficacy is unknown. Prior studies in healthy subjects taking rivaroxaban revealed that 4F-PCC partially reverses the prolonged prothrombin time (PT), and fully restores the endogenous thrombin potential (ETP). The effect of TXA has not been evaluated. Methods In this double-blind, parallel-group study, 147 healthy volunteers given rivaroxaban 20 mg twice daily for 3 days were randomized after their morning dose on day 4 to receive intravenous 4F-PCC (50 IU kg-1 ), TXA (1.0 g), or saline. Standardized punch biopsies were performed at baseline and after 4F-PCC, TXA or saline administration. Reversal was assessed by measuring bleeding duration and bleeding volume at biopsy sites, and by determining the PT and ETP. Results As compared with saline, 4F-PCC partially reversed the PT and completely reversed the ETP, whereas TXA had no effect. Neither 4F-PCC nor TXA reduced bleeding duration or volume. All treatments were well tolerated, with no recorded adverse events. Conclusions Although 4F-PCC reduced the PT and increased the ETP in volunteers given supratherapeutic doses of rivaroxaban, neither 4F-PCC nor TXA influenced punch biopsy bleeding.

Impact of age, comorbidity, and polypharmacy on the efficacy and safety of edoxaban for the treatment of venous thromboembolism: An analysis of the randomized, double-blind Hokusai-VTE trial

BACKGROUND

Many patients with venous thromboembolism (VTE) are elderly, have multiple comorbidities and take several concomitant medications. Physicians may prefer warfarin over direct oral anticoagulants (DOACs) in such patients because comparative data are lacking. This analysis was designed to determine the effects of advanced age, comorbidities, and polypharmacy on the efficacy and safety of edoxaban and warfarin in patients with VTE.

METHODS

Using data from the Hokusai-VTE study, we report rates of recurrent VTE and of clinically relevant bleeding by age category (<65, 65-75, and ≥75; <80 versus ≥80years), and by number of comorbidities (0, 1-2, >2) and concomitant medications (<3, 3-5, >5). Hazard ratios (HR) and corresponding 95% confidence intervals (CI) for edoxaban versus warfarin were determined and Kaplan-Meier methodology was used to construct time-to-event curves. At 3months, pre- and postdose levels of edoxaban were measured using mass spectrometry. For warfarin-treated patients, the time in therapeutic range was calculated. The study was approved by institutional review boards; informed consent was obtained.

RESULTS

Recurrent VTE increased with advanced age, multiple comorbidities, and polypharmacy in warfarin-treated patients but not with edoxaban. Edoxaban was more effective than warfarin in patients ≥75years of age and in those with multiple comorbidities. In the 517 patients over 80years of age, recurrent VTE occurred in 2.8% given edoxaban and in 5.7% given warfarin (HR 0.51, 95% CI 0.21-1.24). Bleeding increased with age, comorbidity, and polypharmacy regardless of treatment, but the relative safety of edoxaban versus well-managed warfarin was maintained. Age, comorbidity, and polypharmacy did not impact edoxaban concentrations.

CONCLUSIONS

These data suggest that a once-daily fixed dose of edoxaban is more effective and at least as safe as warfarin in high-risk VTE patients identified by older age, more comorbidities, and polypharmacy.

CLINICAL TRIAL REGISTRATION

NCT00986154.

Outpatient Management in Patients with Venous Thromboembolism with Edoxaban: A Post Hoc Analysis of the Hokusai-VTE Study

Direct oral anticoagulants (DOACs) facilitate the outpatient treatment of venous thromboembolism (VTE). However, the pivotal trials of DOACs have not reported outcomes separately for patients managed either as outpatients or in the hospital. We performed a subgroup analysis of the Hokusai-VTE study comparing efficacy and safety of edoxaban with warfarin in 8,292 patients with acute VTE. Patients received initial therapy with open-label enoxaparin or unfractionated heparin for ≥5 days in the hospital or as an outpatient at the discretion of the treating physician. Edoxaban or warfarin was then given for 3 to 12 months. The primary efficacy outcome was the cumulative incidence of symptomatic recurrent VTE at 12 months. The principal safety outcome was the incidence of clinically relevant bleeding (composite of major or clinically relevant non-major bleeding). Of the 5,223 consecutively enrolled patients with recorded hospital status and length of stay, 1,414 patients (27.1%) were managed as outpatients and 3,809 were managed in hospital. Among the outpatients, initial presentation was symptomatic deep-vein thrombosis (DVT) in 1,183 patients (83.7%) and pulmonary embolism (PE) in 231 patients (16.3%). Among the outpatients with DVT, recurrent VTE occurred in 18 (3.0%) given edoxaban and in 21 (3.6%) given warfarin (risk difference: −0.61, 95% confidence interval [CI]: −2.6 to 1.4). The principal safety outcome in outpatients occurred in 46 edoxaban patients (7.7%) and in 48 warfarin patients (8.3%; risk difference: −0.59, 95% CI: −3.7 to 2.5). Most outpatients had symptomatic DVT at presentation. In these patients, initial heparin followed by edoxaban had similar efficacy and safety to standard therapy with heparin and warfarin.

Phase 2 study of TAK-442, an oral factor Xa inhibitor, in patients following acute coronary syndrome

TAK-442 is an oral direct factor Xa inhibitor. We sought to determine the dose-dependent effect of TAK-442 on major bleeding when added to standard treatment in stabilised patients with acute coronary syndrome (ACS). In this phase II double-blind study, 2,753 ACS patients were randomised to TAK-442 or placebo in addition to usual care using a three-stage adaptive design. Patients were randomised to placebo in all stages, but doses of TAK-442 escalated from 10 mg BID, 20 mg twice-daily (BID), or 40 mg once-daily (QD) in stage 1; to 40 mg BID, 80 mg QD, or 80 mg BID in stage 2; and to 160 mg QD or 120 mg BID in stage 3. Study drug was started 36 hours after emergent treatment of ACS and within seven days of admission, and continued for 24 weeks. The primary endpoint was incidence of TIMI (thrombolysis in myocardial infarction) major bleeding. TIMI major bleeding incidence was low, but higher with the pooled TAK-442 doses than with placebo (17 [0.9%] vs 4 [0.5%]; p=0.47), although the difference was neither significant nor dose-dependent. However, a dose response was evident when using the modified ISTH scale. The incidence of cardiovascular events was similar among TAK-442 dose groups and placebo. When administered over a wide range of doses after an ACS event, TAK-442 treatment did not result in a dose-dependent increase in TIMI major bleeding, but increased bleeding was observed when a more sensitive bleeding scale was used. There was no evidence for efficacy.

Effect of recombinant factor VIIa on melagatran-induced inhibition of thrombin generation and platelet activation in healthy volunteers

The objectives were to investigate whether activation of the extrinsic coagulation cascade by recombinant factor VIIa (rFVIIa) reverses the inhibition of thrombin generation and platelet activation by melagatran, the active form of the oral direct thrombin inhibitor ximelagatran. In a single-blind, randomized, parallel-group study, volunteers (20 per group) received a 5-hour intravenous (iv) infusion to achieve steadystate melagatran plasma concentrations of approximately 0.5 µmol/L, with a single iv bolus of rFVIIa (90 µg/kg) or placebo at 60 minutes. Prothrombin fragment 1+2, thrombin-antithrombin complex, fibrinopeptide A, β-thromboglobulin, and thrombin-activatable fibrinolysis inhibitor were quantified for venous and shed blood. Activated partial thromboplastin time (APTT), prothrombin time (PT), endogenous thrombin potential, thrombus precursor protein (TpP), and plasmin-α2-antiplasmin complex concentrations were determined in venous blood. Shed blood volume was measured. Melagatran reduced markers of thrombin generation and platelet activation in shed blood and prolonged APTT. rFVIIa increased FVIIa activity, PT, and TpP in venous blood. All other parameters were unaffected. In conclusion, rFVIIa did not reverse the anticoagulant effects of high constant concentrations of melagatran. However, the potential value of higher, continuous or repeated doses of rFVIIa or its use with lower melagatran concentrations has not been excluded.

Only high levels of dabigatran attenuate catheter thrombosis in vitro and in rabbits

In patients with mechanical heart valves, thromboembolic events were more frequent with dabigatran, an oral thrombin inhibitor, than with warfarin. This observation raises the possibility that dabigatran may be less effective than conventional anticoagulants in patients with other blood-contacting devices, such as catheters. To address this, we compared the capacity of dabigatran and/or heparin to inhibit catheter-induced thrombin generation in vitro and to attenuate catheter occlusion in rabbits. Using a catheter-induced thrombin generation assay, concentrations of dabigatran over 100 ng/ml prolonged the lag time and time to peak thrombin, and reduced the peak thrombin concentration and endogenous thrombin potential in a concentration-dependent fashion. Compared with saline in a rabbit model of catheter thrombosis, dabigatran prolonged the mean time to catheter occlusion by 2.9– and 1.9-fold when plasma levels were 173 and 140 ng/ml, respectively; values comparable to median peak levels in humans given dabigatran 150 mg twice daily. In contrast, low-dose dabigatran, which produced a level of 60 ng/ml; a value comparable to the trough level of dabigatran in humans, did not prolong the time to occlusion. Whereas a 70 U/kg bolus of heparin prolonged the mean time to occlusion by 3.4-fold, a 15 U/kg bolus had no effect. When low-dose dabigatran was given in combination with 15 U/kg heparin, the mean time to occlusion was prolonged by 2.7-fold. These findings suggest that only peak levels of dabigatran are sufficient to prevent catheter-induced clotting unless supplemented heparin is given.

Comparison of the ecarin chromogenic assay and diluted thrombin time for quantification of dabigatran concentrations

Essentials Routine monitoring is unnecessary but measuring dabigatran levels is helpful in certain situations. We compared ecarin chromogenic assay (STA-ECA-II) and dilute thrombin time (dTT) in patient samples. Both tests provided accurate measurements over a wide range of dabigatran concentrations. Adoption of STA-ECA-II and dTT into routine clinical practice will improve patient care.

SUMMARY

Background Although routine coagulation monitoring is unnecessary, measuring plasma dabigatran concentrations can be useful for detecting drug accumulation in renal failure or overdose, assessing the contribution of dabigatran to serious bleeding, planning the timing of urgent surgery or intervention, or determining the suitability for thrombolytic therapy for acute ischemic stroke. Dabigatran concentrations can be quantified using chromogenic or clot-based tests, such as the ecarin chromogenic assay (ECA) and the diluted thrombin time (dTT), respectively. Objective The purpose of this study was to compare the results of these assays with dabigatran concentrations measured by the reference standard of mass spectrometry in samples from 50 dabigatran-treated patients collected at peak and trough after at least 4 months of drug intake. Methods Drug levels measured with either the STA Ecarin Chromogenic Assay-II (STA-ECA-II) or dTT were linearly correlated with those determined by mass spectrometry over a wide range of concentrations. Results and Conclusions For detection of levels below 50 ng mL-1 both tests have specificities of at least 96%, suggesting that they accurately detect even low levels of drug. Therefore, regardless of whether a chromogenic or clot-based platform is preferred, the STA-ECA-II and dTT are useful tests for measuring dabigatran concentrations. Unfortunately, neither test is licensed by the United States Food and Drug Administration. Although approved in other jurisdictions, the dTT and STA-ECA-II are not widely or rapidly available in most hospitals. Therefore, cooperation between regulators and hospitals is urgently needed to render these tests readily available to inform patient care.

Emerging anticoagulants for the treatment of venous thromboembolism

Anticoagulant therapy is the cornerstone of treatment of venous thromboembolism (VTE). Such treatment is divided into two stages. Rapid initial anticoagulation is given to minimize the risk of thrombus extension and fatal pulmonary embolism, whereas extended anticoagulation is aimed at preventing recurrent VTE, thereby reducing the risk of postphlebitic syndrome. With currently available drugs, immediate anticoagulation can only be achieved with parenteral agents, such as heparin, low-molecular-weight heparin, or fondaparinux. Extended treatment usually involves the administration of vitamin K antagonists,such as warfarin. Emerging anticoagulants have the potential to streamline VTE treatment. These agents include idraparinux, a long-acting synthetic pentasaccharide that is given subcutaneously on a once-weekly basis, and new oral anticoagulants that target thrombin or factor Xa. This paper i) reviews the pharmacology of these agents, ii) outlines their potential strengths and weaknesses, iii) describes the results of clinical trials with these new drugs, and iv) identifies the evolving role of new anticoagulants in the management of VTE.

Edoxaban for treatment of venous thromboembolism in patients with cancer

Direct oral anticoagulants may be effective and safe for treatment of venous thromboembolism (VTE) in cancer patients, but they have not been compared with low-molecular-weight heparin (LMWH), the current recommended treatment for these patients. The Hokusai VTE-cancer study is a randomised, open-label, clinical trial to evaluate whether edoxaban, an oral factor Xa inhibitor, is non-inferior to LMWH for treatment of VTE in patients with cancer. We present the rationale and some design features of the study. One such feature is the composite primary outcome of recurrent VTE and major bleeding during a 12-month study period. These two complications occur frequently in cancer patients receiving anticoagulant treatment and have a significant impact. The evaluation beyond six months will fill the current gap in the evidence base for the long-term treatment of these patients. Based on the observation that the risk of recurrent VTE in patients with active cancer is similar to that in those with a history of cancer, the Hokusai VTE-cancer study will enrol patients if whose cancer was diagnosed within the past two years. In addition, patients with incidental VTE are eligible because their risk of recurrent VTE is similar to that in patients with symptomatic disease. The unique design features of the Hokusai VTE-cancer study should lead to enrolment of a broad spectrum of cancer patients with VTE who could benefit from oral anticoagulant treatment.

A dose-finding study with TAK-442, an oral factor Xa inhibitor, in patients undergoing elective total knee replacement surgery

This multicentre dose-finding study compared TAK-442, an oral factor Xa inhibitor, with enoxaparin for thromboprophylaxis after knee arthroplasty. In this parallel group study, patients were randomised to oral TAK-442 (40 or 80 mg once-daily [QD] or 10, 20, 40, or 80 mg twice-daily [BID] started 6–8 hours postoperatively), which was blinded as to dose, or to open-label subcutaneous enoxaparin (30 mg BID starting 12–24 hours postoperatively) for 10 days. Treatments were continued until bilateral venography was performed (maximum of 14 days). The primary efficacy endpoint was the composite of any deep-vein thrombosis, non-fatal pulmonary embolism or all-cause mortality, while the primary safety endpoint was major bleeding. Of 1,038 patients randomised who received at least one dose of study drug, 949 completed the study and 730 (76.9%) were evaluable for the primary efficacy analysis. Recruitment into the 10 and 20 mg BID dose groups was stopped early because the incidences of the primary efficacy endpoint were significantly higher than that with enoxaparin. The primary efficacy endpoint occurred in 22.0% of patients given enoxaparin and in 39.0%, 38.4%, 23.5%, 21.4%, 26.8%, and 14.3% of those receiving TAK-442 10 mg BID, 20 mg BID, 40 mg QD, 40 mg BID, 80 mg QD, and 80 mg BID, respectively. The incidences of major and clinically relevant non-major bleeding with TAK-442 were not dose-dependent or different from that with enoxaparin. All TAK-442 doses except 10 and 20 mg BID displayed similar efficacy and safety profiles to enoxaparin.

Multimerin 1 binds factor V and activated factor V with high affinity and inhibits thrombin generation

Multimerin 1 (MMRN1) is a polymeric, factorV (FV) binding protein that is stored in platelet and endothelial cell secretion granules but is undetectable in normal plasma. In human platelet α-granules, FV is stored complexed to MMRN1, predominantly by noncovalent binding interactions. The FV binding site for MMRN1 is located in the light chain, where it overlaps the C1 and C2 domain membrane binding sites essential for activated FV (FVa) procoagulant function. Surface plasmon resonance (SPR), circular dichroism (CD) and thrombin generation assays were used to study the binding of FV and FVa to MMRN1, and the functional consequences. FV and FVa bound MMRN1 with high affinities (KD:2 and 7 nM, respectively). FV dissociated more slowly from MMRN1 than FVa in SPR experiments, and CD analyses suggested greater conformational changes in mixtures of FV and MMRN1 than in mixtures of FV and MMRN1. SPR analyses indicated that soluble phosphatidylserine (1,2-Dicaproylsn-glycero-3-phospho-L-serine) competitively inhibited both FV-MMRN1 and FVa-MMRN1 binding. Furthermore, exogenous MMRN1 delayed and reduced thrombin generation by plasma and platelets, and it reduced thrombin generation by preformed FVa. Exogenous MMRN1 also delayed FV activation, triggered by adding tissue factor to plasma, or by adding purified thrombin or factor Xa to purified FV. The high affinity binding of FV to MMRN1 may facilitate the costorage of the two proteins in platelet α-granules. As a consequence, MMRN1 release during platelet activation may limit platelet dependent thrombin generation in vivo.

General mechanisms of coagulation and targets of anticoagulants (Section I)

Contrary to previous models based on plasma, coagulation processes are currently believed to be mostly cell surface-based, including three overlapping phases: initiation, when tissue factor-expressing cells and microparticles are exposed to plasma; amplification, whereby small amounts of thrombin induce platelet activation and aggregation, and promote activation of factors (F)V, FVIII and FXI on platelet surfaces; and propagation, in which the Xase (tenase) and prothrombinase complexes are formed, producing a burst of thrombin and the cleavage of fibrinogen to fibrin. Thrombin exerts a number of additional biological actions, including platelet activation, amplification and self-inhibition of coagulation, clot stabilisation and anti-fibrinolysis, in processes occurring in the proximity of vessel injury, tightly regulated by a series of inhibitory mechanisms. ″Classical″ anticoagulants, including heparin and vitamin K antagonists, typically target multiple coagulation steps. A number of new anticoagulants, already developed or under development, target specific steps in the process, inhibiting a single coagulation factor or mimicking natural coagulation inhibitors.

Parenteral anticoagulants in heart disease: Current status and perspectives (Section II)

Anticoagulants are a mainstay of cardiovascular therapy, and parenteral anticoagulants have widespread use in cardiology, especially in acute situations. Parenteral anticoagulants include unfractionated heparin, low-molecular-weight heparins, the synthetic pentasaccharides fondaparinux, idraparinux and idrabiotaparinux, and parenteral direct thrombin inhibitors. The several shortcomings of unfractionated heparin and of low-molecular-weight heparins have prompted the development of the other newer agents. Here we review the mechanisms of action, pharmacological properties and side effects of parenteral anticoagulants used in the management of coronary heart disease treated with or without percutaneous coronary interventions, cardioversion for atrial fibrillation, and prosthetic heart valves and valve repair. Using an evidence-based approach, we describe the results of completed clinical trials, highlight ongoing research with currently available agents, and recommend therapeutic options for specific heart diseases.

Incorporating edoxaban into the choice of anticoagulants for atrial fibrillation

The non-vitamin K antagonist oral anticoagulants (NOACs) are replacing warfarin for stroke prevention in many patients with nonvalvular atrial fibrillation. Edoxaban, an oral factor Xa inhibitor, is the newest entrant in this class. Results of the Effective Anticoagulation with Factor Xa Next Generation in Atrial Fibrillation (ENGAGE AF) study demonstrate that edoxaban is noninferior to warfarin for prevention of stroke and systemic embolic events, and is associated with significantly less major bleeding, including intracranial bleeding, and reduced cardiovascular mortality. With a net clinical benefit over warfarin, edoxaban is well positioned as a choice among the NOACs, which include dabigatran, rivaroxaban, and apixaban. But how will clinicians choose amongst them? The purpose of this paper is to (a) place the ENGAGE AF trial results into context with results of the studies with the other NOACs, and (b) aid clinicians in selection of the right anticoagulant for the right atrial fibrillation patient.

Dose reduction of edoxaban preserves efficacy and safety for the treatment of venous thromboembolism

Direct oral anticoagulants simplify venous thromboembolism (VTE) treatment by obviating the need for coagulation monitoring. Nonetheless, renal function, body weight and P-glycoprotein inhibitors influence drug levels. The objective of this analysis was to determine whether reduction in edoxaban dose based on clinical criteria avoids excess drug exposure and preserves efficacy and safety in the Hokusai-VTE study. After initial heparin, patients received edoxaban or warfarin for 3-12 months. Edoxaban was given once daily at a dose of 60 mg, which was reduced to 30 mg in patients with a creatinine clearance of 30–50 ml/minute, body weight ≤60 kg or receiving certain P-glycoprotein inhibitors. The primary efficacy outcome was recurrent VTE and the principal safety outcome was major or clinically relevant non-major bleeding. A total of 8292 patients with acute VTE were randomised, 733 and 719 patients in the edoxaban and warfarin groups met the criteria for dose reduction. These patients were older, more often female or Asian and had more extensive VTE. Edoxaban levels were lower in the 30 mg edoxaban group. Rates of recurrent VTE and bleeding with the 30 mg and 60 mg edoxaban dose were comparable: VTE rates were 3.0 % and 3.2 % and clinically relevant bleeding rates were 7.9 % and 8.6 %, respectively. Rates of recurrent VTE and bleeding in the warfarin-treated patients meeting the criteria for dose reduction were 4.2 % and 12.8 %, respectively. The reduced dose edoxaban regimen maintained efficacy and safety compared with the 60 mg dose but was safer than warfarin in patients meeting the criteria for dose reduction.

Supplementary Material to this article is available online at www.thrombosis-online.com.

New developments in anticoagulants: Past, present and future

Thrombosis is a leading cause of death and disability worldwide, and anticoagulants are the mainstay of its prevention and treatment. Starting with unfractionated heparin (UFH) and vitamin K antagonists (VKAs) such as warfarin, the choices of anticoagulants have exploded in the past 20 years. With over 90% subcutaneous bioavailability, no need for coagulation monitoring and dose adjustment, and a lower risk of heparin-induced thrombocytopenia, low-molecular-weight heparin and fondaparinux have replaced UFH for prevention and initial treatment of venous thromboembolism and for secondary prevention in cancer patients. In patients undergoing percutaneous interventions, bivalirudin is often used instead of UFH. Oral anticoagulation therapy has advanced with the introduction of the non-vitamin K antagonist oral anticoagulants (NOACs), which include dabigatran, rivaroxaban, apixaban and edoxaban. With efficacy at least equal to that of VKAs but with greater safety and convenience, the NOACs are now replacing VKAs for many indications. This paper a) highlights these advances, b) outlines how specific reversal agents for the NOACs will enhance their safety, c) reviews some of the ongoing trials with the NOACs, and d) describes the inhibitors of factor XII and XI that are under investigation as anticoagulants.

A Test in Context: D-Dimer

D-dimer is a soluble fibrin degradation product that results from ordered breakdown of thrombi by the fibrinolytic system. Numerous studies have shown that D-dimer serves as a valuable marker of activation of coagulation and fibrinolysis. Consequently, D-dimer has been extensively investigated for the diagnosis of venous thromboembolism (VTE) and is used routinely for this indication. In addition, D-dimer has been evaluated for determining the optimal duration of anticoagulation in VTE patients, for diagnosing and monitoring disseminated intravascular coagulation, and as an aid in the identification of medical patients at high risk for VTE. Thus, quantification of D-dimer levels serves an important role in guiding therapy. This review: 1) describes how D-dimer is generated; 2) reviews the assays used for its detection; and 3) discusses the role of D-dimer determination in these various conditions.

A randomised, double blind comparison of tecarfarin, a novel vitamin K antagonist, with warfarin

Tecarfarin is a novel vitamin K antagonist that is metabolised by carboxyl estererase, thereby eliminating the variability associated with cytochrome-mediated metabolism. EmbraceAC was designed to compare the quality of anticoagulation with tecarfarin and warfarin as determined by time in therapeutic range (TTR). In this phase 2/3 randomised and blinded trial, 607 patients with indications for chronic anticoagulation were assigned to warfarin (n=304) or tecarfarin (n=303). Dosing of study drugs was managed by a centralised dose control centre, which had access to genotyping. The primary analysis tested superiority of tecarfarin over warfarin for TTR. Patients were recruited between May 12, 2008 and May 12, 2009. TTR with tecarfarin and warfarin were similar (72.3% and 71.5%, respectively; p=0.51). In those taking CYP2C9 interacting drugs, the TTR on tecarfarin (n=92) was similar to that on warfarin (n=87, 72.2% and 69.9%, respectively; p=0.15). In patients with mechanical heart valves, the TTR of tecarfarin (n=42) was similar to that of warfarin (n=42, 68.4% and 66.3%, respectively; p=0.51). The same was true for the TTR in patients with any CYP2C9 variant allele and on CYP2C9-interacting drugs (tecarfarin, n=24, 76.5% vs warfarin, n=31, 69.5%; p=0.09). There was no difference in thromboembolic or bleeding events. In conclusion, superiority of tecarfarin over warfarin for TTR was not demonstrated. The TTR with tecarfarin was similar to that with well-controlled warfarin and tecarfarin appeared to be safe and well tolerated with few major bleeding and no thrombotic events. Favourable trends in certain subpopulations make tecarfarin a promising oral anticoagulant that deserves further study.

Supplementary Material to this article is available online at www.thrombosis-online.com.

Idarucizumab for Dabigatran Reversal - Full Cohort Analysis

BACKGROUND

Idarucizumab, a monoclonal antibody fragment, was developed to reverse the anticoagulant effect of dabigatran.

METHODS

We performed a multicenter, prospective, open-label study to determine whether 5 g of intravenous idarucizumab would be able to reverse the anticoagulant effect of dabigatran in patients who had uncontrolled bleeding (group A) or were about to undergo an urgent procedure (group B). The primary end point was the maximum percentage reversal of the anticoagulant effect of dabigatran within 4 hours after the administration of idarucizumab, on the basis of the diluted thrombin time or ecarin clotting time. Secondary end points included the restoration of hemostasis and safety measures.

RESULTS

A total of 503 patients were enrolled: 301 in group A, and 202 in group B. The median maximum percentage reversal of dabigatran was 100% (95% confidence interval, 100 to 100), on the basis of either the diluted thrombin time or the ecarin clotting time. In group A, 137 patients (45.5%) presented with gastrointestinal bleeding and 98 (32.6%) presented with intracranial hemorrhage; among the patients who could be assessed, the median time to the cessation of bleeding was 2.5 hours. In group B, the median time to the initiation of the intended procedure was 1.6 hours; periprocedural hemostasis was assessed as normal in 93.4% of the patients, mildly abnormal in 5.1%, and moderately abnormal in 1.5%. At 90 days, thrombotic events had occurred in 6.3% of the patients in group A and in 7.4% in group B, and the mortality rate was 18.8% and 18.9%, respectively. There were no serious adverse safety signals.

CONCLUSIONS

In emergency situations, idarucizumab rapidly, durably, and safely reversed the anticoagulant effect of dabigatran. (Funded by Boehringer Ingelheim; RE-VERSE AD ClinicalTrials.gov number, NCT02104947 .).

Research and Practice in Thrombosis and Haemostasis - a new ISTH publishing platform for the global thrombosis and hemostasis community

Research and Practice in Thrombosis and Haemostasis (RPTH) is the new Open Access journal of the International Society on Thrombosis and Haemostasis (ISTH). It was launched to capitalize on the emerging open access publishing trends for knowledge dissemination after extensive methodological research and member and reader surveys identified unmet needs that could not be fully addressed with a traditional print medium. RPTH provides new publishing opportunities to showcase the rich research and education activities of the diverse networks of clinicians, researchers and allied health professionals from around the world active in thrombosis and hemostasis and beyond. The addition of RPTH to the ISTH lineup of publications is designed to foster innovation and interdisciplinary collaboration and will provide another outlet for more excellent papers to be published under the ISTH umbrella. Moreover, RPTH offers a new forum that make the latest science more accessible to the general public.

Recent advances in the treatment of venous thromboembolism in the era of the direct oral anticoagulants

The direct oral anticoagulants (DOACs) have now supplanted vitamin K antagonists (VKAs) for the treatment of venous thromboembolism (VTE). The DOACs include dabigatran, which inhibits thrombin, and rivaroxaban, apixaban, and edoxaban, which inhibit factor Xa. The DOACs are as effective for the prevention of recurrence as conventional VTE treatment, consisting of a parenteral anticoagulant followed by a VKA, and are associated with less bleeding. Because of these properties and the convenience of fixed dosing without the need for routine coagulation monitoring, guidelines now recommend DOACs over VKAs for VTE treatment in patients without active cancer. This paper examines the increasing role of the DOACs for VTE treatment.

Lys 42/43/44 and Arg 12 of thrombin-activable fibrinolysis inhibitor comprise a thrombomodulin exosite essential for its antifibrinolytic potential

The thrombin-thrombomodulin (TM) complex activates thrombin-activable fibrinolysis inhibitor (TAFI) more efficiently than thrombin alone. The exosite on TAFI required for its TM-dependent activation by thrombin has not been identified. Based on previous work by us and others, we generated TAFI variants with one or more of residues Lys 42, Lys 43, Lys 44 and Arg 12 within the activation peptide mutated to alanine. Mutation of one, two, or three Lys residues or the Arg residue alone decreased the catalytic efficiency of TAFI activation by thrombin-TM by 2.4-, 3.2-, 4.7-, and 15.0-fold, respectively, and increased the TAFI concentrations required for half-maximal prolongation of clot lysis times (K_1/2) by 3-, 4,- 15-, and 24-fold, respectively. Mutation of all four residues decreased the catalytic efficiency of TAFI activation by 45.0-fold, increased the K_1/2 by 130-fold, and abolished antifibrinolytic activity in a clot lysis assay at physiologic levels of TAFI. Similar trends in the antifibrinolytic activity of the TAFI variants were observed when plasma clots were formed using HUVECs as the source of TM. When thrombin was used as the activator, mutation of all four residues reduced the rate of activation by 1.1-fold compared with wild-type TAFI, suggesting that these mutations only impacted activation kinetics in the presence of TM. Surface plasmon resonance data suggest that mutation of the four residues abrogates TM binding with or without thrombin. Therefore, Lys 42, Lys 43, Lys 44 and Arg 12 are critical for the interaction of TAFI with the thrombin-TM complex, which modulates its antifibrinolytic potential.

Selection and characterization of a DNA aptamer inhibiting coagulation factor XIa

Factor XIa (FXIa) is a serine protease that catalyzes the activation of Factor IX (FIX) in the blood coagulation cascade. FXIa and its precursor FXI are emergent therapeutic targets for the development of safer anticoagulant agents. Here, we sought a novel DNA-based agent to inhibit FXIa. Towards this goal, an 80 base, single-stranded DNA aptamer library (containing a 40 base randomized core) was screened for FXIa-binding candidates, using ten rounds of positive and negative selection. After selection, 6 of 89 different sequences inhibited FXIa-mediated chromogenic substrate S2366 cleavage. The most active anti-FXIa aptamer had a hypervariable central sequence 5′-AACCTATCGGACTATTGTTAGTGATTTTTATAGTGT-3′ and was designated Factor ELeven Inhibitory APtamer (FELIAP). FELIAP, but not a scrambled aptamer control (SCRAPT), competitively inhibited FXIa-catalyzed S2366 cleavage, FIX activation, and complex formation with antithrombin. No effect of FELIAP on FXI activation was observed. FELIAP inhibited plasma clotting and thrombin generation assays to a significantly greater extent than SCRAPT. Immobilized FELIAP bound FXIa with strong affinity and an equilibrium binding constant (K_D) in the low nanomolar range determined using surface plasmon resonance. FELIAP is the first FXIa-inhibitory aptamer to be described and constitutes a lead compound to develop related aptamers for in vivo use.

Abstract 348: Lys 42, 43, 44 and Arg 12 of Thrombin Activable Fibrinolysis Inhibitor Comprise Thrombomodulin Binding Exosite Essential for Exerting Its Antifibrinolytic Activity

The thrombin-thrombomodulin (TM) complex activates thrombin-activable fibrinolysis inhibitor (TAFI) more efficiently than thrombin or plasmin alone. The exosite on TAFI required for its TM-dependent activation by thrombin has not been identified. Based on previous work by us and others, we generated TAFI variants with one or more of residues Lys 42, Lys 43, Lys 44 and Arg 12 within the activation peptide mutated to alanine. Mutation of one, two, or three Lys residues or the Arg residue alone decreased the catalytic efficiency of TAFI activation by thrombin-TM by 2.4-, 3.2-, 4.7-, and 15.0-fold, respectively, and increased the TAFI concentrations required for half-maximal prolongation of clot lysis times (K 1/2 ) by 3-, 4,- 15-, and 24-fold, respectively. Mutation of all four residues eliminated TM binding, decreased the catalytic efficiency of TAFI activation by 45.0-fold, increased the K 1/2 by 130-fold, and abolished antifibrinolytic activity in a clot lysis assay. When thrombin or plasmin was used as the activator, mutation of all four residues reduced the rate of activation by 1.1- and 4.0-fold compared with wild-type TAFI, respectively, suggesting that the mutation only impacted activation kinetics by thrombin-TM. Surface plasmon resonance data show that mutation of the four residues results in complete loss of binding, either in the presence or absence of thrombin. Together, our findings suggest that these four residues are critical for the interaction of TAFI with the thrombin-TM complex that modulates its antifibrinolytic activity.

Once versus twice daily aspirin after coronary bypass surgery: a randomized trial

Essentials Coronary artery bypass graft (CABG) failure is associated with myocardial infarction and death. We tested whether more frequent dosing improves aspirin (ASA) response following CABG surgery. Twice-daily compared with once-daily dosing reduces ASA hyporesponsiveness after CABG surgery. The efficacy of twice-daily ASA needs to be tested in a trial powered for clinical outcomes.

SUMMARY

Background Acetyl-salicylic acid (ASA) hyporesponsiveness occurs transiently after coronary artery bypass graft (CABG) surgery and may compromise the effectiveness of ASA in reducing thrombotic graft failure. A reduced response to ASA 81 mg once-daily after CABG surgery is overcome by four times daily ASA dosing. Objectives To determine whether ASA 325 mg once-daily or 162 mg twice-daily overcomes a reduced response to ASA 81 mg once-daily after CABG surgery. Methods Adults undergoing CABG surgery were randomized to ASA 81 mg once-daily, 325 mg once-daily or 162 mg twice-daily. The primary outcome was median serum thromboxane B2 (TXB2 ) level on postoperative day 4. We pooled the results with those of our earlier study to obtain better estimates of the effect of ASA 325 mg once-daily or in divided doses over 24 h. Results We randomized 68 patients undergoing CABG surgery. On postoperative day 4, patients randomized to receive ASA 81 mg once-daily had a median day 4 TXB2 level of 4.2 ng mL-1 (Q1, Q3: 1.5, 7.5 ng mL-1 ), which was higher than in those randomized to ASA 162 mg twice-daily (1.1 ng mL-1 ; Q1, Q3: 0.7, 2.7 ng mL-1 ) and similar to those randomized to ASA 325 mg once-daily (1.9 ng mL-1 ; Q1, Q3: 0.9, 4.7 ng mL-1 ). Pooled data showed that the median TXB2 level on day 4 in groups receiving ASA 162 mg twice-daily or 81 mg four times daily was 1.1 ng mL-1 compared with 2.2 ng mL-1 in those receiving ASA 325 mg once-daily. Conclusions Multiple daily dosing of ASA is more effective than ASA 81 mg once-daily or 325 mg once-daily at suppressing serum TXB2 formation after CABG surgery. A twice-daily treatment regimen needs to be tested in a clinical outcome study.

Healthcare resource utilization in patients receiving idarucizumab for reversal of dabigatran anticoagulation due to major bleeding, urgent surgery, or procedural interventions: interim results from the RE-VERSE AD™ study

AIMS

Patients treated with anticoagulants may experience serious bleeding or require urgent surgery or intervention, and may benefit from rapid anticoagulant reversal. This exploratory analysis assessed healthcare resource utilization (HCRU) in patients treated with idarucizumab, a specific reversal agent for dabigatran etexilate.

MATERIALS AND METHODS

RE-VERSE AD™ (NCT02104947), a prospective, multi-center open-label study, is evaluating idarucizumab for dabigatran reversal in patients with serious bleeding (Group A) or undergoing emergency surgery/procedures (Group B). HCRU outcome measures evaluated in the first 90 patients enrolled were use of blood products and pro-hemostatic agents, length of stay (LOS) in hospital, and LOS in intensive care unit (ICU).

RESULTS

Blood products or pro-hemostatic agents were given to 63% (32/51) of patients in Group A and 23% (9/39) of patients in Group B on the day of/day after surgery. An overnight hospital stay was reported for 82% (42/51) of patients in Group A with median LOS = 7 (range = 1-71) bed-days. For Group B, 92% (36/39) had an overnight hospital stay with a median LOS = 9 (range = 1-92) bed-days. In Group A, 17 patients were admitted to the ICU for at least 1 day with median LOS = 4 (range = 1-44) days; in Group B the number was 15 with median LOS = 2 (range = 1-92) days.

LIMITATIONS

The lack of a control group and the small patient numbers limit the strength of the conclusions.

CONCLUSIONS

The use of idarucizumab may simplify emergency management of dabigatran-treated patients with life-threatening bleeds and reduce perioperative complications in patients undergoing emergency surgery.

Evolving Treatments for Arterial and Venous Thrombosis: Role of the Direct Oral Anticoagulants

The direct oral anticoagulants (DOACs) represent a major advance in oral anticoagulant therapy and have replaced the vitamin K antagonists as the preferred treatment for many indications. By simplifying long-term anticoagulant therapy and improving its safety, the DOACs have the potential to reduce the global burden of thrombosis. Postmarketing studies suggest that the favorable results achieved with DOACs in the randomized controlled trials can be readily translated into practice, but highlight the need for appropriate patient, drug and dose selection, and careful follow-up. Leveraging on their success to date, ongoing studies are assessing the utility of DOACs for the prevention of thrombosis in patients with embolic stroke of unknown source, heart failure, coronary artery disease, peripheral artery disease, antiphospholipid syndrome, and cancer. The purpose of this article is to (1) review the pharmacology of the DOACs, (2) describe the advantages of the DOACs over vitamin K antagonists, (3) summarize the experience with the DOACs in established indications, (4) highlight current challenges and limitations, (5) highlight potential new indications; and (6) identify future directions for anticoagulant therapy.

Rivaroxaban or Aspirin for Extended Treatment of Venous Thromboembolism

BACKGROUND

Although many patients with venous thromboembolism require extended treatment, it is uncertain whether it is better to use full- or lower-intensity anticoagulation therapy or aspirin.

METHODS

In this randomized, double-blind, phase 3 study, we assigned 3396 patients with venous thromboembolism to receive either once-daily rivaroxaban (at doses of 20 mg or 10 mg) or 100 mg of aspirin. All the study patients had completed 6 to 12 months of anticoagulation therapy and were in equipoise regarding the need for continued anticoagulation. Study drugs were administered for up to 12 months. The primary efficacy outcome was symptomatic recurrent fatal or nonfatal venous thromboembolism, and the principal safety outcome was major bleeding.

RESULTS

A total of 3365 patients were included in the intention-to-treat analyses (median treatment duration, 351 days). The primary efficacy outcome occurred in 17 of 1107 patients (1.5%) receiving 20 mg of rivaroxaban and in 13 of 1127 patients (1.2%) receiving 10 mg of rivaroxaban, as compared with 50 of 1131 patients (4.4%) receiving aspirin (hazard ratio for 20 mg of rivaroxaban vs. aspirin, 0.34; 95% confidence interval [CI], 0.20 to 0.59; hazard ratio for 10 mg of rivaroxaban vs. aspirin, 0.26; 95% CI, 0.14 to 0.47; P<0.001 for both comparisons). Rates of major bleeding were 0.5% in the group receiving 20 mg of rivaroxaban, 0.4% in the group receiving 10 mg of rivaroxaban, and 0.3% in the aspirin group; the rates of clinically relevant nonmajor bleeding were 2.7%, 2.0%, and 1.8%, respectively. The incidence of adverse events was similar in all three groups.

CONCLUSIONS

Among patients with venous thromboembolism in equipoise for continued anticoagulation, the risk of a recurrent event was significantly lower with rivaroxaban at either a treatment dose (20 mg) or a prophylactic dose (10 mg) than with aspirin, without a significant increase in bleeding rates. (Funded by Bayer Pharmaceuticals; EINSTEIN CHOICE ClinicalTrials.gov number, NCT02064439 .).

Factor XI and factor XII as targets for new anticoagulants

Although the non-vitamin antagonist oral anticoagulants produce less intracranial bleeding than warfarin, serious bleeding still occurs. Therefore, the search for safer anticoagulants continues. Factor XII and factor XI have emerged as promising targets whose inhibition has the potential to prevent thrombosis with little or no disruption of hemostasis. Thus, thrombosis is attenuated in mice deficient in factor XII or factor XI and patients with congenital factor XII deficiency do not bleed and those with factor XI deficiency rarely have spontaneous bleeding. Strategies targeting factor XII and XI include antisense oligonucleotides to decrease their synthesis, inhibitory antibodies or aptamers, and small molecule inhibitors. These strategies attenuate thrombosis in various animal models and factor XI knockdown with an antisense oligonucleotide in patients undergoing knee replacement surgery reduced postoperative venous thromboembolism to a greater extent than enoxaparin without increasing bleeding. Therefore, current efforts are focused on evaluating the efficacy and safety of factor XII and factor XI directed anticoagulant strategies.

Factors XI and XII as Targets for New Anticoagulants

Compared with vitamin K antagonists, the direct oral anticoagulants (DOACs) are simpler to administer and are associated with less intracranial bleeding. Nonetheless, even with the DOACs, bleeding still occurs and many patients with atrial fibrillation fail to receive anticoagulant thromboprophylaxis because of the fear of bleeding. Therefore, there is an urgent need for safer anticoagulants. Recent investigations into the biochemistry of hemostasis and thrombosis have identified new targets for development of novel anticoagulants. Using data from complementary sources, including epidemiological studies and investigations in various animal models, the contact pathway has emerged as a potential mediator of thrombosis that plays a minor part in hemostasis. Consequently, factor (F) XII of the contact system and FXI in the intrinsic pathway have been identified as potentially safer targets of anticoagulation than thrombin or FXa. However, further studies are needed to identify which is the better target for the appropriate indication. This review highlights the evidence for focusing on FXI and FXII and examines the novel approaches directed at these new targets. These emerging strategies should address current unmet medical needs and provide new avenues by which to improve anticoagulant therapy by reducing the risk of bleeding.

Choosing wisely: The impact of patient selection on efficacy and safety outcomes in the EINSTEIN-DVT/PE and AMPLIFY trials

BACKGROUND

The results of the EINSTEIN-DVT/PE and AMPLIFY trials, which compared rivaroxaban and apixaban with conventional anticoagulation therapy for acute venous thromboembolism (VTE), respectively, are often compared. However, the trials differed in duration of therapy (3-12 and 6months, respectively) and in patient selection (few exclusion criteria and more stringent exclusion criteria, respectively).

METHODS

To determine the effect of these methodological differences on outcomes, the patients enrolled in EINSTEIN-DVT/PE were divided into 2 cohorts; the 5253 patients that matched the exclusion criteria for AMPLIFY and were treated for at least 6months (cohort 1) and the 2368 patients who would have been ineligible for AMPLIFY (cohort 2).

RESULTS

Compared with patients in cohort 2, those in cohort 1 were older and more often male and there were more with unprovoked VTE, prior VTE, cancer and known thrombophilia. In cohort 1, rivaroxaban would have significantly reduced recurrent VTE (relative risk [RR], 0.64; 95% confidence interval [CI], 0.43-0.95) and major bleeding (RR, 0.50; 95% CI, 0.30-0.82) compared with conventional therapy, whereas the two treatments would have had similar effects on recurrent VTE (RR, 1.08; 95% CI, 0.65-1.79) and major bleeding (RR, 1.03; 95% CI, 0.48-2.18) in cohort 2.

CONCLUSIONS

This analysis illustrates the influence of patient selection and treatments duration on outcome results and highlights the limitations of cross-trial comparisons.

Global Anticoagulant Registry in the Field - Venous Thromboembolism (GARFIELD-VTE). Rationale and design

Venous thromboembolism (VTE) is a common disorder associated with significant rates of morbidity and mortality. VTE management aims to reduce mortality, the risks of recurrence, and long-term complications. VTE treatment is evolving with the introduction of non-vitamin K antagonist anticoagulants (NOACs). The Global Anticoagulant Registry in the FIELD - Venous Thromboembolism (GARFIELD-VTE) is a prospective, multicentre, observational study that will enrol 10,000 patients treated for acute VTE from ~500 sites in 28 countries. Identified sites reflect the diversity of care settings, including hospital and outpatient settings. Patients will be managed according to local practices and followed for at least three years. The primary objective is to determine the extent to which VTE treatment varies in the real-world setting and to assess the impact of such variability on clinical and economic outcomes. Evolving patterns of care will be captured using two sequential cohorts. The GARFIELD-VTE registry will provide insights into the evolving global treatment patterns for VTE, both deep-vein thrombosis and pulmonary embolism. By enrolling patients from diverse care settings, the registry will provide information on adherence to national and international guidelines, identify good practice as well as treatment deficiencies, and relate patient outcomes to clinical management. The incidence of death, recurrent VTE, bleeding, post-thrombotic syndrome and chronic thromboembolic pulmonary hypertension will be documented. By capturing information during and after anticoagulation treatment, the registry will not only define aspects of the natural history of VTE, but also its economic and societal impact at a regional and global level.

Optimizing the safety of treatment for venous thromboembolism in the era of direct oral anticoagulants

Direct oral anticoagulants (DOACs) are rapidly replacing vitamin K antagonists (VKAs) for treatment of venous thromboembolism (VTE). The DOACs include dabigatran, which inhibits thrombin, and rivaroxaban, apixaban, and edoxaban, which inhibit factor Xa. When compared with conventional VTE treatment consisting of a parenteral anticoagulant followed by a VKA, the DOACs were equally effective for prevention of recurrence, but were associated with less bleeding. With similar efficacy, better safety, and the convenience of fixed dosing without the need for routine coagulation monitoring, guidelines now recommend DOACs over VKAs for VTE treatment in patients without active cancer. Nonetheless, measures are needed to optimize the safety of DOACs. Focusing on these measures, this paper summarizes the results of phase III trials evaluating DOACs for VTE treatment; identifies which VTE patients are or are not candidates for DOACs; provides guidance on how to choose among DOACs; lists the licensed dosing information for DOACs; discusses the optimal treatment duration for VTE; describes periprocedural management of DOACs in patients requiring surgery or intervention; and finally, reviews the management of bleeding, including the role for specific reversal agents.

Clinical presentation and course of bleeding events in patients with venous thromboembolism, treated with apixaban or enoxaparin and warfarin. Results from the AMPLIFY trial

Apixaban, a direct acting oral anticoagulant (DOAC), was found to be non-inferior to and safer as enoxaparin followed by warfarin for treatment of venous thromboembolism (VTE) in the AMPLIFY trial. Information is needed on how bleeding events with DOACs present and develop. In this post-hoc analysis, the clinical presentation and course of all major and clinically relevant non major (CRNM) bleeding events in the AMPLIFY trial were blindly classified by three investigators, using pre-designed classification schemes containing four categories. Odds ratios (OR) for classifying as category three or four (representing a more severe clinical presentation and course) were calculated between apixaban and enoxaparin/warfarin. In total, 63 major and 311 CRNM bleeding events were classified. Of the major bleeds, a more severe clinical presentation occurred in 28.5 % of apixaban versus 44.9 % of enoxaparin/warfarin related recipients (OR 0.49, 95 % confidence interval [CI] 0.14-1.78). A severe clinical course was observed in 14.3 % and in 12.2 %, respectively (OR 1.19, 95 %CI 0.21-6.69). Of the CRNM bleeding events, a more severe clinical presentation and extent of clinical care was found in 25 % of apixaban recipients compared to 22.7 % in the enoxaparin/warfarin group (OR 1.13, 95 %CI 0.65-1.97). The clinical presentation and course of major and CRNM bleeds were similar in apixaban and enoxaparin/warfarin treated patients. This finding should reassure physicians and patients that even in the absence of a specific reversal agent, apixaban is a convenient and safe choice for VTE.

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

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

Edoxaban for venous thromboembolism in patients with cancer: results from a non-inferiority subgroup analysis of the Hokusai-VTE randomised, double-blind, double-dummy trial

BACKGROUND

Venous thromboembolism occurs commonly in patients with cancer. Direct oral anticoagulants are non-inferior to conventional anticoagulants for the treatment of venous thromboembolism. We hypothesised that edoxaban, a direct oral inhibitor of activated clotting factor Xa, might be more suitable than conventional anticoagulants in the management of cancer-associated venous thromboembolism. The aim of this study was to assess the efficacy and safety of edoxaban compared with warfarin in a subgroup of patients with cancer enrolled in the Hokusai-VTE trial.

METHODS

We did a prespecified subgroup analysis in August, 2013, and a post-hoc analysis of non-inferiority and safety in March, 2016, of the patients with cancer enrolled in the randomised, double-blind, double-dummy, multicentre, Hokusai-VTE trial done between Jan 28, 2010, and Oct 31, 2012. In this study, patients aged at least 18 years with acute symptomatic deep-vein thrombosis or acute symptomatic pulmonary embolism (with or without deep-vein thrombosis) were assigned to receive edoxaban 60 mg once per day (or 30 mg once per day for patients with a creatinine clearance of 30-50 mL/min, bodyweight <60 kg, or who were receiving concomitant treatment with the P-glycoprotein inhibitors quinidine or verapamil) or warfarin (dose adjusted to maintain the international normalised ratio between 2·0 and 3·0) or placebos for either group for at least 3 months up to 12 months. All patients received initial therapy with open-label enoxaparin or unfractionated heparin for at least 5 days. Edoxoban (or placebo) was started after discontinuation of initial heparin; warfarin (or placebo) started concurrently with the study regimen of heparin. In our analysis we examined data for a subgroup of these patients who had a history of cancer or who had been categorised as having active cancer by the study physician at the time of enrolment. Additionally, all patients with a history of cancer were reviewed post hoc and categorised according to the presence or absence of active cancer. The primary efficacy outcome was the proportion of these patients with symptomatic recurrent venous thromboembolism during the 12-month study period, analysed in the modified intention-to-treat population, with an upper limit of the CI for the hazard ratio (HR) of 1·5. The principal safety outcome was the proportion of patients who had clinically relevant bleeding in the population of patients who received at least one dose of the study drug. This study is registered with ClinicalTrials.gov, number NCT00986154.

FINDINGS

Of 771 patients with cancer enrolled in the trial, 378 were assigned to edoxaban and 393 to warfarin. Recurrent venous thromboembolism occurred in 14 (4%) of 378 patients given edoxaban and in 28 (7%) of 393 patients given warfarin (hazard ratio [HR] 0·53, 95% CI 0·28-1·00; p=0·0007). The upper limit of this 95% CI did not exceed the non-inferiority margin of 1·5 that was prespecified for the trial. Clinically relevant bleeding (major or non-major) occurred in 47 (12%) of 378 patients who received edoxaban and in 74 (19%) of 393 patients who received warfarin; HR for clinically relevant bleeding 0·64, 95% CI 0·45-0·92; p=0·017. Major bleeding occurred in ten (3%) of 378 patients with a history of cancer who received edoxaban and in 13 (3%) of 393 who received warfarin (HR 0·80, 95% CI 0·35-1·83).

INTERPRETATION

Edoxaban might be as effective as warfarin for the treatment of patients with cancer with venous thromboembolism, and with less clinically relevant bleeding. Additional clinical trials of edoxaban versus low-molecular-weight heparin for the treatment of venous thromboembolism in patients with cancer are warranted.

FUNDING

Daiichi Sankyo.