Edoxaban, a direct factor Xa inhibitor, suppresses tissue-factor induced human platelet aggregation and clot-bound factor Xa in vitro: Comparison with an antithrombin-dependent factor Xa inhibitor, fondaparinux

Beyond Anticoagulation: A Comprehensive Review of Non-Vitamin K Oral Anticoagulants (NOACs) in Inflammation and Protease-Activated Receptor Signaling

Non-vitamin K oral anticoagulants (NOACs) have revolutionized anticoagulant therapy, offering improved safety and efficacy over traditional agents like warfarin. This review comprehensively examines the dual roles of NOACs-apixaban, rivaroxaban, edoxaban, and dabigatran-not only as anticoagulants, but also as modulators of inflammation via protease-activated receptor (PAR) signaling. We highlight the unique pharmacotherapeutic properties of each NOAC, supported by key clinical trials demonstrating their effectiveness in preventing thromboembolic events. Beyond their established anticoagulant roles, emerging research suggests that NOACs influence inflammation through PAR signaling pathways, implicating factors such as factor Xa (FXa) and thrombin in the modulation of inflammatory responses. This review synthesizes current evidence on the anti-inflammatory potential of NOACs, exploring their impact on inflammatory markers and conditions like atherosclerosis and diabetes. By delineating the mechanisms by which NOACs mediate anti-inflammatory effects, this work aims to expand their therapeutic utility, offering new perspectives for managing inflammatory diseases. Our findings underscore the broader clinical implications of NOACs, advocating for their consideration in therapeutic strategies aimed at addressing inflammation-related pathologies. This comprehensive synthesis not only enhances understanding of NOACs' multifaceted roles, but also paves the way for future research and clinical applications in inflammation and cardiovascular health.

Ex Vivo Antiplatelet Effects of Oral Anticoagulants

BACKGROUND

The impact of non-vitamin K antagonist oral anticoagulants (NOACs) on platelet function is still unclear. We conducted a comprehensive ex vivo study aimed at assessing the effect of the four currently marketed NOACs on platelet function.

METHODS

We incubated blood samples from healthy donors with concentrations of NOACs (50, 150 and 250 ng/mL), in the range of those achieved in the plasma of patients during therapy. We evaluated generation of thrombin; light transmittance platelet aggregation (LTA) in response to adenosine diphosphate (ADP), thrombin receptor-activating peptide (TRAP), human γ-thrombin (THR) and tissue factor (TF); generation of thromboxane (TX)B2; and expression of protease-activated receptor (PAR)-1 and P-selectin on the platelet surface.

RESULTS

All NOACs concentration-dependently reduced thrombin generation compared with control. THR-induced LTA was suppressed by the addition of dabigatran at any concentration, while TF-induced LTA was reduced by factor-Xa inhibitors. ADP- and TRAP-induced LTA was not modified by NOACs. TXB2 generation was reduced by all NOACs, particularly at the highest concentrations. We found a concentration-dependent increase in PAR-1 expression after incubation with dabigatran, mainly at the highest concentrations, but not with FXa inhibitors; P-selectin expression was not changed by any drugs.

CONCLUSIONS

Treatment with the NOACs is associated with measurable ex vivo changes in platelet function, arguing for antiplatelet effects beyond the well-known anticoagulant activities of these drugs. There are differences, however, among the NOACs, especially between dabigatran and the FXa inhibitors.

Comparison of edoxaban and enoxaparin in a rat model of AlCl3-induced thrombosis of the superior sagittal sinus

Cerebral sinus venous thrombosis (CSVT) is an uncommon disease that is usually treated with anticoagulation (heparin, low-molecular heparin, or vitamin K-antagonists). We compared treatment with edoxaban, an oral factor Xa-antagonist, that has not been approved in patients with CSVT, with enoxaparin, a well-established therapy, in a rat model of CSVT. Fifty male Wistar rats were randomized into 5 groups (10 animals each) and subjected to aluminum chloride (AlCl3)-induced thrombosis of the superior sagittal sinus (SSS) or sham procedure. Animals with thrombosis of the SSS were treated with edoxaban, enoxaparin, or placebo. Diagnostic workup included neurological examination, MRI imaging, MR-flow measurements of the SSS, and immunohistochemical staining. Neurological examination revealed no differences between treatment groups. Seven days after initial thrombosis, flow in the SSS was lower in the active treatment group as compared to sham-operated animals (p < 0.05). Flow in the SSS in the active treatment groups (edoxaban 1 h prior to thrombosis: 0.16 cm/s ± 0.06 cm/s; edoxaban 6 h after thrombosis: 0.13 cm/s ± 0.05 cm/s; enoxaparin: 0.13 cm/s ± 0.04 cm/s; placebo: 0.07 cm/s ± 0.02 cm/s) was higher as compared to placebo (p < 0.05), but there were no differences between the active treatment groups (p > 0.05). Immunohistochemical staining showed no differences in the actively treated animals. Edoxaban proved to be similar to enoxaparin in a model of experimental AlCl3-induced CSVT.

Edoxaban Monotherapy in Nonvalvular Atrial Fibrillation Patients with Coronary Artery Disease

Background

Current guidelines recommend an oral anticoagulant (OAC) monotherapy in patients with nonvalvular atrial fibrillation (NVAF) and stable coronary artery disease (CAD) 1 year postpercutaneous coronary intervention (PCI). It might be possible to shorten the time for de-escalation from a dual therapy to monotherapy, but data regarding de-escalation to an edoxaban monotherapy are lacking. This study aimed to assess the clinical safety of an edoxaban monotherapy in patients with NVAF and stable CAD.

Methods

A multicenter, prospective, randomized, open-label, and parallel group study was established to investigate the safety of an edoxaban monotherapy in patients with NVAF and stable CAD including over 6 months postimplantation of a third-generation DES and 1 year postimplantation of other stents (PRAEDO AF study). Between March 2018 and June 2020, 147 patients from 8 institutions in Japan were randomized to receive either an edoxaban monotherapy (n = 74) or combination therapy (edoxaban plus clopidogrel, n = 73). The primary study endpoint was the composite incidence of major bleeding and clinically significant bleeding, defined according to the ISTH criteria.

Results

Major or clinically significant bleeding occurred in 2 patients in the monotherapy group (1.67% per patient-year) and in 5 patients in the combination therapy group (4.28% per patient-year) (hazard ratio, 0.39; 95% confidence interval, 0.08-2.02). There was no incidence of a myocardial infarction, stent thrombosis, unstable angina requiring revascularization, ischemic stroke, systemic stroke, or hemorrhagic stroke in either of the groups.

Conclusions

The edoxaban monotherapy was shown to have acceptable clinical safety in patients with NVAF and stable CAD. The study was registered with the Japan Registry of Clinical Trials (jRCTs031180119).

Immunothrombosis and the Role of Platelets in Venous Thromboembolic Diseases

Venous thromboembolism (VTE) is the third leading cardiovascular cause of death and is conventionally treated with anticoagulants that directly antagonize coagulation. However, recent data have demonstrated that also platelets play a crucial role in VTE pathophysiology. In the current review, we outline how platelets are involved during all stages of experimental venous thrombosis. Platelets mediate initiation of the disease by attaching to the vessel wall upon which they mediate leukocyte recruitment. This process is referred to as immunothrombosis, and within this novel concept inflammatory cells such as leukocytes and platelets directly drive the progression of VTE. In addition to their involvement in immunothrombosis, activated platelets can directly drive venous thrombosis by supporting coagulation and secreting procoagulant factors. Furthermore, fibrinolysis and vessel resolution are (partly) mediated by platelets. Finally, we summarize how conventional antiplatelet therapy can prevent experimental venous thrombosis and impacts (recurrent) VTE in humans.

D-dimer levels in patients with nonvalvular atrial fibrillation and acute heart failure treated with edoxaban

BACKGROUND

D-dimer levels can predict ischemic stroke in patients with acute heart failure (AHF). However, the effects of direct oral anticoagulants on D-dimer levels have not been investigated during admission for AHF in patients with atrial fibrillation (AF). This study examined D-dimer levels immediately after admission and following edoxaban initiation as a sub-analysis of a multi-center study that investigated the pharmacokinetics and pharmacodynamics of edoxaban in patients with nonvalvular AF (NVAF) and AHF.

METHODS

Hospitalized patients with NVAF and AHF received edoxaban according to the label. The primary measure was the change in D-dimer levels on 7 consecutive days after admission for AHF. We also investigated differences according to prior edoxaban use (de novo at the time of admission or continuation).

RESULTS

In 10/13 (76.9%) de novo patients, D-dimer levels exceeded the reference value (1.0 µg/mL) at admission (mean, 2.12 µg/mL) and subsequently decreased in 9 patients (at final blood sampling: mean, 1.12 µg/mL); 1 patient did not fall below the reference value due to stasis dermatitis. In the continuation group, most patients had D-dimer levels below the reference value from Day 1 (mean, 0.93 µg/mL), and levels remained stable or decreased (at final blood sampling: mean, 0.49 µg/mL). No events of stroke were observed.

CONCLUSIONS

D-dimer levels may be elevated in patients with NVAF and AHF, particularly in those without prior anticoagulant treatment. Edoxaban may be effective for lowering and keeping D-dimer levels, a biomarker for predicting ischemic stroke, below the reference value in patients with NVAF and AHF.

The role of extracellular vesicles in traumatic brain injury-induced acute lung injury

Acute lung injury (ALI), a common complication after traumatic brain injury (TBI), can evolve into acute respiratory distress syndrome (ARDS) and has a mortality rate of 30%-40%. Secondary ALI after TBI exhibits the following typical pathological features: infiltration of neutrophils into the alveolar and interstitial space, alveolar septal thickening, alveolar edema, and hemorrhage. Extracellular vesicles (EVs) were recently identified as key mediators in TBI-induced ALI. Due to their small size and lipid bilayer, they can pass through the disrupted blood-brain barrier (BBB) into the peripheral circulation and deliver their contents, such as genetic material and proteins, to target cells through processes such as fusion, receptor-mediated interactions, and uptake. Acting as messengers, EVs contribute to mediating brain-lung cross talk after TBI. In this review, we aim to summarize the mechanism of EVs in TBI-induced ALI, which may provide new ideas for clinical treatment.

Non-Vitamin K Antagonist Oral Anticoagulants in Coronary Artery Disease

The prevention of atherothrombotic events is the primary goal in the treatment of patients with arteriosclerotic disorders. Despite recent improvements in the management of coronary artery disease (CAD) with revascularization techniques and antiplatelet therapy, some patients remain at risk of recurrent cardiovascular events. This could be related to additional thrombin generation. As a result, there has been interest in developing novel therapies to prevent thromboembolic events, targeting thrombin-mediated pathways. These include non-vitamin K antagonist oral anticoagulants (NOACs). This article aims to summarize the recent clinical studies that investigated the role of NOACs in CAD.

Dual Pathway of Inhibition and Vascular Protection in Patients with Atherosclerotic Disease

Несмотря на широкое внедрение в клиническую практику современной антитромботической стратегии (моно- или двойной антитромбоцитарной терапии), резидуальный риск неблагоприятных сердечно-сосудистых событий у пациентов с ишемической болезнью сердца (ИБС) и заболеваниями периферических артерий (ЗПА) по-прежнему остается высоким. До настоящего времени двойная антитромбоцитарная терапия является «золотым стандартом» вторичной профилактики при остром коронарном синдроме (ОКС), а монотерапия рекомендована пациентам с симптоматическим течением ЗПА, стабильной ИБС и цереброваскулярной болезнью. Вместе с тем разрыв атеросклеротической бляшки приводит не только к активации тромбоцитов, но также, вследствие экспозиции тканевого фактора, потенцирует образование тромбина. Поэтому терапевтическая стратегия, направленная на одновременное подавление генерации тромбина и активации тромбоцитов и называемая «двойной путь ингибирования», представляется более эффективной, чем известные варианты лечения, связанные с торможением только одного из двух путей. Как показали результаты исследования COMPASS, комбинация 2,5 мг ривароксабана дважды в сутки со 100 мг/сутки аспирина оказалась более эффективной по сравнению с монотерапией 100 мг/сутки аспирина в части снижения риска серьезных сердечно-сосудистых событий, незапланированных госпитализаций и летальности без увеличения количества фатальных и интракраниальных геморрагических осложнений. Преимущества режима двойного ингибирования, апробированного в исследовании COMPASS, были продемонстрированы в популяции пациентов с недавним ОКС, стабильной ИБС и ЗПА, а также после реваскуляризации нижних конечностей. На сегодняшний день ривароксабан является единственным антикоагулянтом, подтвердившим безусловные преимущества в сочетании с антитромбоцитарной терапией в указанных группах пациентов. Комбинированная терапия низкими дозами ривароксабана (2,5 мг/дважды/сутки) и аспирином (100 мг/сутки) уже включена в последние международные рекомендации как вариант вторичной профилактики у пациентов с патологией коронарных и периферических артерий.

Patients with cardiovascular (CV) disease are at high residual risk of CV events (including peripheral ischemic events), even when they receive the current antithrombotic strategies (single/dual antiplatelet therapy). Until now, dual antiplatelet therapy is the standard of care for the secondary prevention in patients with acute coronary syndrome (ACS), whereas the single antiplatelet therapy, generally with aspirin, is the standard of care for the secondary prevention in stable patients with coronary artery disease (CAD), peripheral artery disease (PAD), or cerebrovascular disease. Meanwhile, atherosclerotic plaque disruption not only induces the platelet activation, but also results in thrombin generation because of tissue factor exposure. Therefore, interrupting both pathways by combining antiplatelet therapy with an anticoagulant (dual pathway inhibition [DPI]), has the potential to be more effective than inhibiting either pathway alone. The COMPASS trial showed that in comparison with aspirin 100 mg, rivaroxaban 2.5 mg twice a day plus aspirin 100 mg reduced the risk of major cardiac events, CV hospitalization, and mortality, without the increase of intracranial or fatal bleedings. The benefit of DPI using the COMPASS regimen was demonstrated in patients with the recent ACS, in chronic CAD and PAD patients, and after the lower extremity revascularization. So far, rivaroxaban is the only anticoagulant, which is effective in combination with antiplatelet therapies in the mentioned groups. The combination of low-dose rivaroxaban (2.5 mg twice daily) and aspirin (100 mg once daily) has been included recently into the latest international recommendations for the secondary prevention in patients with coronary or peripheral artery disease.

Dual Pathway Inhibition for Vascular Protection in Patients with Atherosclerotic Disease: Rationale and Review of the Evidence

Despite advances in secondary prevention strategies in patients with cardiovascular disease, the residual risk of recurrent atherothrombotic events remains high. Dual-antiplatelet therapy is the standard of care for secondary prevention in patients with acute coronary syndrome (ACS), whereas single antiplatelet therapy, generally with aspirin, is the standard of care for secondary prevention in stable patients with coronary artery disease (CAD), peripheral artery disease (PAD), or cerebrovascular disease. However, atherosclerotic plaque disruption not only triggers platelet activation but also results in thrombin generation because of tissue factor exposure. Therefore, blocking both pathways by combining antiplatelet therapy with an anticoagulant, or dual pathway inhibition (DPI), has the potential to be more effective than inhibiting either pathway alone. The benefit of DPI has been demonstrated in the ATLAS ACS 2-TIMI 51, COMPASS, and VOYAGER PAD trials, where the combination of rivaroxaban vascular dose (2.5 mg twice daily) plus aspirin significantly reduced the risk of atherothrombotic events compared with aspirin across a broad range of patients, including those with recent ACS, those with chronic CAD and/or PAD, and patients with PAD who have undergone peripheral revascularization. This article provides the rationale for this regimen in more detail, including why the DPI regimen with the rivaroxaban vascular dose was developed for vascular protection in a broad spectrum of patients with atherosclerotic disease.

Pharmacodynamic Effects of Vorapaxar in Prior Myocardial Infarction Patients Treated With Potent Oral P2Y12 Receptor Inhibitors With and Without Aspirin: Results of the VORA-PRATIC Study

Background Vorapaxar as an adjunct to dual antiplatelet therapy (DAPT) reduces thrombotic events in patients with prior myocardial infarction at the expense of increased bleeding. Withdrawal of aspirin has emerged as a bleeding reduction strategy. The pharmacodynamic effects of vorapaxar with potent P2Y12 inhibitors as well as the impact of dropping aspirin is unexplored and represented the aim of the VORA-PRATIC (Vorapaxar Therapy in Patients With Prior Myocardial Infarction Treated With Newer Generation P2Y12 Receptor Inhibitors Prasugrel and Ticagrelor) study. Methods and Results Post-myocardial infarction patients (n=130) on standard DAPT (aspirin+prasugrel or ticagrelor) were randomized to 1 of 3 arms: (1) triple therapy: aspirin+prasugrel/ticagrelor+vorapaxar; (2) dual therapy (drop aspirin): prasugrel/ticagrelor+vorapaxar; (3) DAPT: aspirin+prasugrel/ticagrelor. Pharmacodynamic assessments were performed at 3 time points (baseline and 7 and 30 days). Vorapaxar reduced CAT (collagen-ADP-TRAP)-induced platelet aggregation, a marker of platelet-mediated global thrombogenicity (triple therapy versus DAPT at 30 days: mean difference=-27; 95% CI,-35 to -19; P<0.001; primary end point). This effect was attenuated but still significant in the absence of aspirin (dual therapy versus DAPT at 30 days: mean difference=-15; 95% CI,-23 to -7; P<0.001; between-group comparisons, P<0.05). Vorapaxar abolished TRAP-induced aggregation (P<0.001), without affecting thrombin generation and clot strength. There were no differences in markers of P2Y12 reactivity. Markers sensitive to aspirin-induced effects increased (P<0.001) in the dual-therapy arm. Conclusions In post-myocardial infarction patients treated with potent P2Y12 inhibitors, vorapaxar reduces platelet-driven global thrombogenicity, an effect that persisted, albeit attenuated, in the absence of aspirin and without affecting markers of P2Y12 reactivity or clot kinetics. The clinical implications of these PD observations warrant future investigation. Registration URL: https://www.clini​caltr​ials.gov. Unique identifier: NCT02545933.

Pharmacodynamic Effects of Vorapaxar in Patients With and Without Diabetes Mellitus: Results of the OPTIMUS-5 Study

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Vorapaxar reduces thrombotic cardiovascular events in patients with atherosclerotic disease, with enhanced effects in those with DM.

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Adjunctive vorapaxar therapy reduces platelet-mediated thrombogenicity without affecting clot kinetics in both patients with and those without DM having prior MI/PAD on dual antiplatelet therapy with aspirin and clopidogrel.

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The pharmacodynamic effects of vorapaxar occur via selective blockade of the PAR-1 on the platelet membrane without apparent interplay with other platelet signaling pathways.

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Aspirin withdrawal, which leaves patients on a background of clopidogrel and vorapaxar, increases markers specific to COX-1–mediated blockade, leading to an increase in platelet-mediated global thrombogenicity, particularly among patients with DM.

Vorapaxar reduces thrombotic cardiovascular events at the expense of increased bleeding. However, the differential pharmacodynamic (PD) effects of vorapaxar according to diabetes mellitus (DM) status are unknown. Moreover, although withdrawal of aspirin has emerged as a bleeding reduction strategy, the PD effects of stopping aspirin in patients treated with vorapaxar also are unknown. In this prospective PD investigation, vorapaxar was associated with reduced platelet-mediated thrombogenicity without affecting clot kinetics irrespective of DM status. However, platelet-mediated thrombogenicity increased after aspirin withdrawal, particularly among patients with DM. (Optimizing anti-Platelet Therapy In diabetes MellitUS-5 Study [OPTIMUS-5]; NCT02548650)

Nonhemostatic Activities of Factor Xa: Are There Pleiotropic Effects of Anti-FXa Direct Oral Anticoagulants?

Factor Xa (FXa) is the key serine protease of the coagulation cascade as it is the point of convergence of the intrinsic and extrinsic pathways, leading to the formation of thrombin. Factor Xa is an established target of anticoagulation therapy, due to its central role in coagulation. Over the past years, several direct oral anticoagulants (DOACs) targeting FXa have been developed. Rivaroxaban, apixaban, and edoxaban are used in clinical practice for prevention and treatment of thrombotic diseases. Increasing evidence suggests that FXa exerts nonhemostatic cellular effects that are mediated mainly through protease-activated receptors-1 and -2 and are involved in pathophysiological conditions, such as atherosclerosis, inflammation, and fibrosis. Direct inhibition of FXa by DOACs could be beneficial in these conditions. This is a narrative review that focuses on the cellular effects of FXa in various cell types and conditions, as well as on the possible pleiotropic effects of FXa-targeting DOACs.

Anticoagulant therapy for acute venous thrombo-embolism in cancer patients: A systematic review and network meta-analysis

Background

Low-molecular-weight heparin (LMWH) is usually recommended for the treatment of cancer-associated thrombosis (CAT) but this treatment requires burdensome daily injections. We did a systematic review to compare the efficacy and safety of direct oral anticoagulants (DOAC), vitamin K antagonists (VKA) and LMWH in patients with CAT.

Methods

We searched Pubmed, Embase and CENTRAL for randomised controlled trials comparing DOAC, VKA and LMWH in patients with CAT. Pairwise and network meta-analyses were computed for venous thromboembolism (VTE) recurrence and bleeding complications.

Results

We identified 14 studies, including 4,661 patients. In pairwise comparison, DOAC were superior to LMWH to prevent VTE recurrence (HR 0.63; 95% CI 0.42–0.96) and LMWH was superior to VKA (HR 0.53; 95% CI 0.40–0.70). The rate of major bleeding was higher with DOAC compared to LMWH (HR 1.78; 95% CI 1.11–2.87). In the network meta-analysis, DOAC had a lower, but non-significant, rate of VTE recurrence compared to LMWH (HR 0.74; 95% CI 0.54–1.01). Both DOAC (HR 0.42; 95% CI 0.29–0.61) and LMWH (HR 0.57; 95% CI 0.44–0.75) were associated with lower rates of recurrence compared to VKA. No significant difference in major bleeding rate was observed in the network meta-analysis. Inconsistency was observed between pairwise and network meta-analysis comparisons for major bleeding.

Conclusions

DOAC are effective to prevent VTE recurrence in patients with CAT but are associated with an increased risk of bleeding compared to LMWH. The choice of anticoagulant should be personalised, taking into account the patient’s bleeding risk, including cancer site, and patient’s values and preferences.

Effect of apixaban compared with warfarin on coagulation markers in atrial fibrillation

Objectives

Compare the effect of apixaban and warfarin on coagulation and primary haemostasis biomarkers in atrial fibrillation (AF).

Methods

The biomarker substudy from the Apixaban for Reduction in Stroke and Other Thromboembolic Events in Atrial Fibrillation trial included 4850 patients with AF randomised to treatment with apixaban or warfarin. Sixty per cent of patients used vitamin K antagonist (VKA) within 7 days before randomisation. Prothrombin fragment 1+2 (F1+2), D-dimer, soluble CD40 ligand (sCD40L) and von Willebrand factor (vWF) antigen were analysed at randomisation and after 2 months of study treatment.

Results

In patients not on VKA treatment at randomisation, F1+2 and D-dimer levels were decreased by 25% and 23%, respectively, with apixaban, and by 59% and 38%, respectively, with warfarin (p<0.0001 for treatment differences for both). In patients on VKA at randomisation, F1+2 and D-dimer levels increased by 41% and 10%, respectively, with apixaban and decreased by 37% and 11%, respectively, with warfarin (p<0.0001 for treatment differences for both). sCD40L levels were slightly increased at 2 months, regardless of VKA or randomised treatment. Apixaban and warfarin also both reduced vWF antigen regardless of VKA treatment. The efficacy (stroke) and safety (bleeding) of apixaban compared with warfarin was similar irrespectively of biomarker levels at 2 months.

Conclusions

Treatment with apixaban compared with warfarin for stroke prevention in patients with AF was associated with less reduction in thrombin generation and fibrin turnover. This effect of apixaban could contribute to the clinical results where apixaban was superior to warfarin both in stroke prevention and in reducing bleeding risk.

Trial registration number

NCT00412984.

Measuring Direct Oral Anticoagulants

Direct oral anticoagulants (DOACs) can be quantified using methods that can be performed in any clinical or research laboratory using manual or automated instrument platforms. Dabigatran etexilate, the oral direct thrombin inhibitor, can be quantified by drug-calibrated clot or chromogenic-based assays using either thrombin or ecarin as substrates. Oral direct anti-Xa inhibitors, such as rivaroxaban, apixaban, and edoxaban, can be quantified with drug-calibrated anti-Xa kits or reagents as typically used for measuring heparins (unfractionated, low molecular weight, or pentasaccharides).