Jeanne Mendell

Randomised, parallel-group, multicentre, multinational phase 2 study comparing edoxaban, an oral factor Xa inhibitor, with warfarin for stroke prevention in patients with atrial fibrillation

The primary objective of this study was to compare the safety of four fixed-dose regimens of edoxaban with warfarin in patients with non-valvular atrial fibrillation (AF). In this 12-week, parallel-group, multicentre, multinational study, 1,146 patients with AF and risk of stroke were randomised to edoxaban 30 mg qd, 30 mg bid, 60 mg qd, or 60 mg bid or warfarin dose-adjusted to a target international normalised ratio of 2.0-3.0. The study was double-blind to edoxaban dose, but open-label to warfarin. Primary outcomes were occurrence of major and/or clinically relevant non-major bleeding and elevated hepatic enzymes and/or bilirubin. Mean age was 65 +/- 8.7 years and 64.4% were warfarin-naïve. Whereas major plus clinically relevant non-major bleeding occurred in 3.2% of patients randomised to warfarin, the incidence of bleeding was significantly higher with the edoxaban 60 mg bid (10.6%; p=0.002) and 30 mg bid regimens (7.8%; p=0.029), but not with the edoxaban 60 mg qd (3.8%) or 30 mg qd regimens (3.0%). For the same total daily dose of 60 mg, both bleeding frequency and trough edoxaban concentrations were higher in the 30-mg bid group than in the 60-mg qd group. There were no significant differences in hepatic enzyme elevations or bilirubin values among the groups. The safety profiles of edoxaban 30 and 60 mg qd in patients with AF were similar to warfarin. In contrast, the edoxaban bid regimens were associated with more bleeding than warfarin. These results suggest that in this three-month study, edoxaban 30 or 60 mg qd are safe and well-tolerated.

Pharmacokinetics, Biotransformation, and Mass Balance of Edoxaban, a Selective, Direct Factor Xa Inhibitor, in Humans

This study determined the mass balance and pharmacokinetics of edoxaban in humans after oral administration of [14C]edoxaban. After oral administration of 60 mg (as active moiety) of [14C]edoxaban to six healthy male subjects, serial blood/plasma and urinary and fecal samples were collected for up to 168 h postdose. All samples were analyzed for total radioactivity by liquid scintillation counting and for concentrations of edoxaban and four metabolites in plasma, urine, and fecal samples by either high-performance liquid chromatography/tandem mass spectrometry method using multiple reaction modes, or a liquid chromatography radiometric method. The mean recovery of radioactivity was >97% of the administered radioactive dose, with 62.2% eliminated in feces and 35.4% in urine. Unchanged edoxaban accounted for the majority of radioactivity, with 49.1 and 23.8% of the dose as parent observed in feces and urine, respectively. Unchanged edoxaban was the most abundant species in plasma, with a mean area under the curve (AUC)0−∞ of 1596 ng · h/ml. The next most abundant species was metabolite M4, with a mean AUC0−∞ 147 ng · h/ml. The mass balance of edoxaban was well described, with unchanged edoxaban as the most abundant component of total radioactivity. Edoxaban is eliminated through multiple pathways, but each accounts for only a small amount of overall elimination.

The P-Glycoprotein Transport System and Cardiovascular Drugs

Permeability glycoprotein (P-gp) mediates the export of drugs from cells located in the small intestine, blood-brain barrier, hepatocytes, and kidney proximal tubule, serving a protective function for the body against foreign substances. Intestinal absorption, biliary excretion, and urinary excretion of P-gp substrates can therefore be altered by either the inhibition or induction of P-gp. A wide spectrum of drugs, such as anticancer agents and steroids, are known P-gp substrates and/or inhibitors, and many cardiovascular drugs have recently been observed to have clinically relevant interactions as well. We review the interactions among commonly prescribed cardiovascular drugs that are P-gp substrates and observe interactions involving P-gp that may be relevant to clinical practice. Cardiovascular drugs with narrow therapeutic indexes (e.g., antiarrhythmic agents, anticoagulant agents) have demonstrated large increases in concentrations when coadministered with potent P-gp inhibitors, thus increasing the risk for drug toxicity. Therefore, dose adjustment or use of alternative agents should be considered when strong P-gp-mediated drug-drug interactions are present. Finally, interactions between novel drugs and known P-gp inhibitors are now being systematically evaluated during drug development, and recommended guidelines for the administration of P-gp substrate drugs will be expanded.

Modelling and simulation of edoxaban exposure and response relationships in patients with atrial fibrillation

Edoxaban is a novel, orally available, highly specific direct inhibitor of factor Xa and is currently being developed for the treatment and prevention of venous thromboembolism and prevention of stroke and systemic embolism in patients with non-valvular atrial fibrillation (NVAF). The objectives of the present analyses were to characterise edoxaban population pharmacokinetics (PPK) and identify potential intrinsic and extrinsic factors affecting variability in edoxaban exposure, determine if there are relationships between edoxaban pharmacokinetics or biomarkers and the risk of bleeding in patients with NVAF using an exposure-response model, and to use the PPK and exposure-response model to support dose selection for a phase III trial of edoxaban in patients with NVAF. PPK analysis of data from 1,281 edoxaban-dosed subjects with intrinsic factors such as renal impairment or NVAF and extrinsic factors such as concomitant medications revealed significant effects of renal impairment and concomitant strong P-glycoprotein (P-gp) inhibitors on the pharmacokinetics of edoxaban. Exposure-response analysis found that in patients with NVAF, the incidence of bleeding events increased significantly with increasing edoxaban exposure, with steady-state minimum concentration (Cmin,ss) showing the strongest association. Clinical trial simulations of bleeding incidence were used to select 30 mg and 60 mg once-daily edoxaban with 50% dose reductions for patients with moderate renal impairment or receiving concomitant strong P-gp inhibitors as the treatment regimens in the ENGAGE AF-TIMI 48 (NCT00781391) trial.

Effects of food on the pharmacokinetics of edoxaban, an oral direct factor Xa inhibitor, in healthy volunteers.

The primary objective of this study was to assess the effect of a standard high‐fat meal on the single‐dose (60 mg) pharmacokinetics (PK) of edoxaban in healthy Japanese and Caucasian male volunteers matched by body mass index. This was an open‐label, randomized, 2‐period crossover study. All 32 enrolled volunteers completed the study per protocol. Both serial blood and urine samples were collected, and edoxaban concentrations were analyzed by a validated liquid chromatography/tandem mass spectrometry method. Activated partial thromboplastin and prothrombin times were obtained as measures of pharmacodynamic effect. The point estimates of the geometric mean ratios (fed/fasted) for AUC0‐t, AUC0‐∞, and Cmax demonstrated modest increases ranging from 6% to 22% across PK parameters for both race cohorts. The disposition was similar in both Japanese and Caucasian matched volunteers with slightly higher AUC values (ranging from 7%‐9%) in Caucasians. There were no serious adverse events during the study. All drug‐related adverse events were mild and self‐limited, and none were bleeding related. Both Japanese and Caucasian volunteers demonstrated a modest but clinically insignificant food effect. It was concluded that edoxaban can be administered without regard to food.

Bioavailability and Safety of the Factor Xa Inhibitor Edoxaban and the Effects of Quinidine in Healthy Subjects

Edoxaban is an oral, once‐daily, direct factor Xa inhibitor under investigation for stroke prevention in patients with atrial fibrillation and for treatment and secondary prevention of venous thromboembolism. This study evaluated edoxaban absolute bioavailability and effects of the P‐glycoprotein inhibitor quinidine on edoxaban pharmacokinetics after intravenous edoxaban administration.

In vitro study of the anticoagulant effects of edoxaban and its effect on thrombin generation in comparison to fondaparinux

INTRODUCTION Edoxaban, an oral direct factor Xa (FXa) inhibitor, is in Phase III development for prevention and treatment of thromboembolic disorders. Fondaparinux is an approved indirect FXa inhibitor. This study compared the effects of edoxaban and fondaparinux on thrombin generation (TG) using the calibrated automated thrombogram (CAT). Secondary objectives included evaluation of edoxaban and inhibition of coagulation parameters (prothrombin time [PT], activated partial thromboplastin time [aPTT]), anti-FXa activity and clotting times. MATERIALS AND METHODS Pooled citrated platelet-poor plasma from healthy subjects was spiked with edoxaban (0.02-3.65 μM) or fondaparinux (0.15-1.18 μM). Parameters of TG were calculated using Thrombinoscope software. PT ratios and aPTT were measured in the presence of different thromboplastin reagents. Exogenous anti-FXa was measured using Rotachrom HBPM (Stago) and a specific assay developed for direct FXa inhibitors (Hyphen BioMed). RESULTS Edoxaban exhibited a 3-fold greater concentration-dependent effect than fondaparinux across TG parameters (except endogenous thrombin potential). Edoxaban also produced a concentration-dependent prolongation of PT ratio and aPTT. The magnitude of concentration-dependent increase was related to thromboplastin reagent. In contrast to edoxaban, fondaparinux was inactive on these clotting tests. Linear correlations were observed between plasma concentration of edoxaban and anti-FXa activity and results of clotting time assays. CONCLUSIONS TG evaluation by the CAT method, coagulation tests, and anti-FXa and clotting assays demonstrated concentration-dependent effects of edoxaban. The PT and aPTT prolongation are reagent dependent; correction of PT ratio by international normalized ratio does not reduce variability in response. The greater effect of edoxaban vs. fondaparinux may be related to the broader activity of direct FXa inhibitors compared with indirect FXa inhibitors.

The effects of the antiplatelet agents, aspirin and naproxen, on pharmacokinetics and pharmacodynamics of the anticoagulant edoxaban, a direct factor Xa inhibitor.

Abstract: Edoxaban is an oral factor Xa (FXa) inhibitor in clinical development for stroke prevention in patients with atrial fibrillation, an elderly population that frequently receives aspirin (ASA) and/or nonsteroidal anti-inflammatory drugs for concurrent illnesses. Three studies were conducted to evaluate the pharmacokinetic and pharmacodynamic interactions of edoxaban 60 mg coadministered with low-dose (100 mg) ASA, high-dose (325 mg) ASA, or naproxen (500 mg) in healthy subjects (n = 126). Template bleeding times (BT) were measured. Mean baseline (predose) BT for the 3 studies ranged from 4.72 to 6.13 minutes. Edoxaban administered alone increased BT by 21%–35% (4 hours post dose) from baseline. Concomitant administration of edoxaban with high-dose ASA, low-dose ASA, or naproxen increased BT approximately 2-fold showing an additive effect greater than either agent administered alone. Edoxaban pharmacokinetics were not affected by concomitant low-dose ASA or naproxen, but high-dose ASA increased systemic exposure of edoxaban by approximately 30%. The effects of edoxaban on prothrombin time, activated partial thromboplastin time, international normalized ratio, anti-FXa, and intrinsic FXa activity were not influenced by administration with ASA or naproxen. Inhibition of platelet aggregation by high-dose ASA, low-dose ASA, or naproxen was not affected by edoxaban. Concomitant administration of edoxaban and ASA or naproxen was well tolerated.

Ex vivo reversal of the anticoagulant effects of edoxaban

INTRODUCTION Edoxaban is an oral, once-daily direct factor Xa (FXa) inhibitor. Although rapidly cleared, strategies to reverse edoxaban-mediated effects on anticoagulation are needed in cases of excessive bleeding or emergency. This study evaluated the effect of two prohemostatic agents, recombinant factor VIIa (rFVIIa) and factor VIII inhibitor bypass activity (FEIBA), on the anticoagulatory effects of supratherapeutic concentrations of edoxaban in human whole blood ex vivo. MATERIALS AND METHODS Blood samples were collected from six healthy volunteers. Edoxaban (500 or 1000 ng/mL), alone or followed by rFVIIa (0.8 or 1.8μg/mL) or FEIBA (0.75 or 1.5 U/mL), was added to an aliquot of each sample. Biomarkers, including prothrombin time (PT), activated partial thromboplastin time (aPTT), extrinsic FXa activity (anti-FXa), intrinsic factor X activity, and D-dimer, were assessed at 0.25, 0.5, 1, 2, and 4 hours after adding rFVIIa or FEIBA. RESULTS Decreases in measures of PT (p<0.0001), aPTT (p<0.0001), and anti-FXa (p<0.0001) were observed when rFVIIa or FEIBA was added to edoxaban-containing blood samples. Intrinsic FX activity was increased up to 20% and 31% of normal in the presence of edoxaban by rFVIIa and FEIBA, respectively. The impact of these agents on the anticoagulant effects of edoxaban were observed within 15 minutes and remained relatively unchanged at each timepoint thereafter. CONCLUSIONS The findings of this ex vivo study suggest that rFVIIa and FEIBA rapidly reversed edoxaban-mediated anticoagulation effects based on PT and aPTT, but had minimal effect based on intrinsic FX activity. No dose response was observed for rFVIIa or FEIBA.

Edoxaban administration following enoxaparin: A pharmacodynamic, pharmacokinetic, and tolerability assessment in human subjects

Edoxaban is an oral direct factor (F)Xa inhibitor in advanced stages of clinical development. The primary objective of the present study was to assess the pharmacodynamics (PD) and safety of enoxaparin 1 mg/kg followed 12 hours (h) post-dose by edoxaban 60 mg, which is the regimen being used in the phase III study of edoxaban for the treatment of venous thromboembolism (Hokusai-VTE). This was a phase I, open-label, randomised, four-period, four-treatment cross-over study. Treatments were edoxaban alone (EDOX), enoxaparin alone (ENOX), edoxaban plus enoxaparin (EDOX+ENOX), and enoxaparin followed by edoxaban 12 h later (ENOX12-EDOX). Serial blood samples were collected for PD (thrombin generation, anti-FXa) and pharmacokinetic (PK) variables (edoxaban and its principal metabolite M4 by LC-MS/MS, and anti-FIIa as a surrogate of enoxaparin). The highest effect on thrombin AUC (endogenous thrombin potential, or ETP), thrombin (peak), thrombin generation lag time, and velocity index was observed for EDOX+ENOX, followed by ENOX, ENOX12-EDOX, and EDOX. The greatest effect on anti-FXa activity was observed for EDOX+ENOX, followed by ENOX12-EDOX. As expected, neither edoxaban nor enoxaparin significantly altered the PK of the other drug. There were no serious adverse events during the study. It is concluded that a 60-mg dose of edoxaban can be safely administered 12 h following enoxaparin 1 mg/kg.