Absorption, metabolism and excretion of darexaban (YM150), a new direct factor Xa inhibitor in humans

Surfing the Blood Coagulation Cascade: Insight into the Vital Factor Xa

Factor Xa (FXa) plays a key role in haemostasis, it is a central part of the blood coagulation cascade which catalyzes the production of thrombin and leads to clot formation and wound closure. Therefore, FXa is an attractive target for the development of new anticoagulant agents. In this review, we will first describe the molecular features of this fundamental protein in order to understand its mechanism of action, an essential background for the design of novel inhibitors by means of synthetic organic chemistry or using peptides obtained from recombinant methodologies. Then, we will review the current state of the synthesis of novel direct FXa inhibitors along with their mechanisms of action. Finally, approved reversal agents that aid in maintaining blood haemostasis by using these commercial drugs will also be discussed.

Darexaban (YM150) versus enoxaparin for the prevention of venous thromboembolism after total hip arthroplasty: a randomised phase IIb dose confirmation study (ONYX-3)

This double-blind, double-dummy, randomised, phase IIb study (NCT00902928) evaluated different dosing regimens of darexaban compared with enoxaparin (randomised 1:1:1:1:1 to 15 mg twice daily [bid], 30 mg once daily [qd], 30 mg bid or 60 mg qd or enoxaparin 40 mg qd) in patients undergoing elective total hip arthroplasty. Patients, investigators, pharmacists and sponsor were all blinded to treatment allocation. Darexaban administration started 6-10 hours (h) post-surgery. Enoxaparin 40 mg qd administration started 12 ± 2 h before surgery. Treatment continued for 35 days. Bilateral venography was performed on Day 10 ± 2. The primary efficacy outcome was total VTEs (composite of proximal/distal deep-vein thrombosis, pulmonary embolism) or death, at Day 12. Total VTE rates were similar across all groups. There was no apparent difference in efficacy between onceand twice-daily darexaban (odds ratio [OR] 1.00; 95% confidence interval [CI] 0.71–1.42; p=0.988), or total daily dose (30 mg/day vs 60 mg/day; OR 0.81; 95% CI 0.57–1.15; p=0.244). There was no significant difference in major and/or clinically relevant non-major bleeding between darexaban qd or bid, or between total daily doses of 30 mg or 60 mg, and also for any dosing regimen of darexaban vs enoxaparin. Darexaban was well tolerated, without signs of liver toxicity. In conclusion, darexaban, administered qd or bid, and at total daily doses of 30 mg or 60 mg, appears to be effective for VTE prevention and was well tolerated. Data suggest no significant differences between a once- or twice-daily dosing regimen.

A Phase II, double-blind, randomized, parallel group, dose-finding study of the safety and tolerability of darexaban compared with warfarin in patients with non-valvular atrial fibrillation: the oral factor Xa inhibitor for prophylaxis of stroke in atrial fibrillation study 2 (OPAL-2)

BACKGROUND

Darexaban (YM150) is a novel oral anticoagulant that directly inhibits factor Xa.

OBJECTIVES

To investigate the optimal daily dose regimen of YM150 in subjects with non-valvular atrial fibrillation (NVAF).

METHODS

In this multicenter, double-blind, double-dummy, randomized, parallel-group, dose-confirmation study (NCT00938730), patients with NVAF were randomized to darexaban 15 mg bid, 30 mg qd, 30 mg bid, 60 mg qd, 60 mg bid or 120 mg qd, or warfarin qd. The primary endpoint was the incidence of adjudicated major and/or clinically relevant non-major bleeding events. Secondary endpoints included efficacy, pharmacodynamics, safety and tolerability.

RESULTS

A total of 1297 patients were randomized and finally included in the trial (median age, 66 [range 30-89] years; 68.8% male): 981 completed treatment for a median of 28 weeks (interquartile range, 24-36). At daily doses of 30-60 mg, darexaban bid resulted in fewer bleeding events than darexaban qd. For darexaban 120 mg, the bid regimen produced more bleeding events than the qd regimen. Although few efficacy endpoints occurred, these decreased with increasing daily darexaban dose. Darexaban decreased plasma D-dimer levels (index of thrombogenesis) after 4 weeks of treatment by 21.5-33.8% compared with baseline, which was comparable with warfarin at the higher darexaban doses. Darexaban was well tolerated with no liver toxicity.

CONCLUSIONS

In this Phase II study in patients with NVAF, a lower bleeding rate was observed in the 120 mg daily darexaban group compared with warfarin with a reduction in plasma D-dimer as marker for hemostasis. Further investigation of the optimal dose of darexaban for the prevention of stroke in patients with NVAF would need to be considered.

Anticoagulation in atrial fibrillation

Atrial fibrillation increases the risk of stroke, which is a leading cause of death and disability worldwide. The use of oral anticoagulation in patients with atrial fibrillation at moderate or high risk of stroke, estimated by established criteria, improves outcomes. However, to ensure that the benefits exceed the risks of bleeding, appropriate patient selection is essential. Vitamin K antagonism has been the mainstay of treatment; however, newer drugs with novel mechanisms are also available. These novel oral anticoagulants (direct thrombin inhibitors and factor Xa inhibitors) obviate many of warfarin's shortcomings, and they have demonstrated safety and efficacy in large randomized trials of patients with non-valvular atrial fibrillation. However, the management of patients taking warfarin or novel agents remains a clinical challenge. There are several important considerations when selecting anticoagulant therapy for patients with atrial fibrillation. This review will discuss the rationale for anticoagulation in patients with atrial fibrillation; risk stratification for treatment; available agents; the appropriate implementation of these agents; and additional, specific clinical considerations for treatment.

Clinical Pharmacokinetics, Pharmacodynamics, Safety and Tolerability of Darexaban, an Oral Direct Factor Xa Inhibitor, in Healthy Elderly Japanese Subjects

The clinical pharmacokinetics, pharmacodynamics, safety and tolerability of darexaban after single and multiple once-daily doses of 60, 120, and 240 mg in healthy elderly Japanese subjects were assessed. Following oral administration, darexaban was rapidly and extensively metabolized to darexaban glucuronide, which is an active glucuronide metabolite. Plasma concentrations of darexaban glucuronide increased with dose, and Cmax and AUC increased dose-dependently after both single and repeated doses. Cumulative urinary excretion of darexaban glucuronide up to 24 hours after repeated doses ranged from 28.59% to 36.50%. PT-INR, aPTT, and FXa activity were prolonged or decreased dose-dependently after both single and repeated doses of darexaban. The time-profile of pharamcodynamic parameters closely followed the time-concentration profile of darexaban glucuronide. Five adverse events occurred in the present study (4: darexaban [16.7%]; 1: placebo [8.3%]), all of which were mild in severity and required no treatment.

Darexaban (YM150), an oral direct factor Xa inhibitor, has no effect on the pharmacokinetics of digoxin

To investigate the impact of the direct Factor Xa inhibitor darexaban administered in a modified-release formulation (darexaban-MR) on the pharmacokinetic (PK) profile of digoxin. In this Phase I, randomized, double-blind, two-period crossover study (8 days for each treatment, 10 days washout), 24 healthy subjects received darexaban-MR 120 mg once/day (qd) + digoxin 0.25 mg qd in one treatment period, and placebo + digoxin 0.25 mg qd in the other treatment period. Blood for PK assessment of digoxin and darexaban was obtained in serial profile on day 8, as well as pre-dose on day 6-7; urinary PK samples were obtained up to 24 h after the last dose on day 8. A lack of interaction was determined if 90 % confidence intervals (CIs) for the geometric mean ratios (GMR) of digoxin C max,ss and AUC0-24h,ss with and without darexaban-MR co-administration were within 0.80-1.25 limits. Pharmacodynamic activity was assessed by international normalized ratio and activated partial thromboplastin time. Twenty-three subjects completed the study. The GMR (90 % CI) for C max,ss and AUC0-24h,ss of digoxin plus darexaban versus digoxin plus placebo was 1.03 (90 % CI: 0.94-1.12) and 1.11 (90 % CI: 1.05-1.17), respectively. The 90 % CI for the GMRs fell within the limits of 0.80-1.25, indicating a lack of drug-drug interaction. Co-administration of digoxin with darexaban-MR was well tolerated, with no unexpected treatment-emergent adverse events or safety concerns. Co-administration of darexaban-MR did not impact the steady-state PK profile of digoxin.