Publications by authors named "Chikako Kamisato"

14 Publications

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Prolongation of clot lysis time by a direct thrombin inhibitor melagatran mediated by paradoxical enhancement of thrombin generation: comparison with a direct factor Xa inhibitor edoxaban.

Blood Coagul Fibrinolysis 2021 Apr;32(3):209-215

Biological Research Laboratories, R & D Division, Daiichi Sankyo Co., Ltd, Tokyo, Japan.

Previously, we reported that a direct thrombin inhibitor melagatran paradoxically increased thrombin generation in human plasma in the presence of thrombomodulin. The aim of this study is to test the hypothesis that melagatran may exert a deleterious effect on tissue-type plasminogen activator (t-PA)-induced fibrinolysis via enhancement of thrombin generation and subsequent activation of thrombin-activatable fibrinolysis inhibitor (TAFI) and factor XIII (FXIII). Clot formation in human plasma containing t-PA and thrombomodulin was induced by tissue factor. The absorbance at 405 nm was measured to obtain clot lysis time. Effects of melagatran and a factor Xa inhibitor edoxaban on clot lysis time were determined. In the presence of thrombomodulin, melagatran significantly prolonged clot lysis time, but edoxaban shortened it. In the absence of thrombomodulin, melagatran did not inhibit fibrinolysis. Prolongation of clot lysis time by melagatran was reversed by activated protein C (which suppressed thrombin generation increased by melagatran) and a TAFIa inhibitor. Melagatran significantly suppressed plasmin generation, while edoxaban significantly increased it. However, both melagatran and edoxaban suppressed FXIII activation. In the clot formed in the presence of melagatran and edoxaban, the fibrin fibre was thin compared with control, showing no clear difference in the clot structures between melagatran and edoxaban. These results indicated that melagatran, not edoxaban, prolonged clot lysis time through the paradoxical enhancement of thrombin generation, and subsequent TAFI activation and inhibition of plasmin generation. Neither FXIII activation nor change in fibrin clot structure contributed to the inhibition of fibrinolysis by melagatran.
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http://dx.doi.org/10.1097/MBC.0000000000001020DOI Listing
April 2021

Combined effect of a direct oral anticoagulant edoxaban and an inhibitor of activated thrombin-activatable fibrinolysis inhibitor on clot lysis.

J Thromb Thrombolysis 2020 Jan;49(1):94-99

End-Organ Disease Laboratories, Daiichi Sankyo Co., Ltd., Tokyo, Japan.

Fibrinolysis is regulated by the thrombin/thrombin-activatable fibrinolysis inhibitor (TAFI) system. Thus, anticoagulants and inhibitors of TAFI are expected to accelerate fibrinolysis. The combined effects of an anticoagulant and a TAFIa inhibitor on fibrinolysis remain unknown. The aim of this study was to evaluate the combined effect of edoxaban, an oral direct factor Xa (FXa) inhibitor, and a TAFIa inhibitor, potato tuber carboxypeptidase inhibitor (PCI) on tissue-type plasminogen activator (t-PA)-induced clot lysis in human plasma in vitro. Pooled human plasma (containing 180 ng/mL t-PA and 0.1 nM thrombomodulin) was mixed with edoxaban and/or PCI. Clot formation was induced by 2.5 pM tissue factor and 4 µM phospholipids and clot lysis time was examined. Plasma plasmin-α2 antiplasmin complex (PAP) concentration was measured as a marker of plasmin generation. Edoxaban or PCI alone significantly shortened the t-PA-induced clot lysis time and plasma PAP concentration. The combination of these compounds significantly accelerated the clot lysis compared with the inhibitors alone. Addition of PCI (0.3, 1, and 3 μg/mL) to 75 ng/mL edoxaban increased plasma PAP concentration compared with edoxaban alone; however, compared with PCI alone only the combination of 0.3 μg/mL PCI + 75 ng/mL edoxaban showed the significant increase in PAP concentration. Concomitant use of an oral direct FXa inhibitor, edoxaban, and a TAFIa inhibitor, PCI, significantly accelerate fibrinolysis via enhancement of plasmin generation. These results suggest that the combination of edoxaban and a TAFIa inhibitor might be beneficial for the treatment of thromboembolic diseases.
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http://dx.doi.org/10.1007/s11239-019-01929-3DOI Listing
January 2020

Prevention of Stent Thrombosis in Rats by a Direct Oral Factor Xa Inhibitor Edoxaban.

Pharmacology 2019 19;103(1-2):17-22. Epub 2018 Oct 19.

Rare Disease Laboratories, Daiichi Sankyo Co., Ltd., Tokyo, Japan.

Background/aims: Stent thrombosis is a serious complication after percutaneous coronary intervention and femoropopliteal endovascular intervention. The aim of this study was to determine the antithrombotic effects of a direct factor Xa inhibitor edoxaban alone or in combination with antiplatelet agents in a rat model of stent thrombosis.

Methods: Stainless steel stents (4 stents per rat) were placed in an extracorporeal arteriovenous shunt. The shunt was inserted into the carotid artery and the jugular vein in each rat to circulate blood. Stent thrombosis was induced by exposing the stents to arterial blood for 30 min. Protein content of the thrombus was measured. Edoxaban and antiplatelet agents (aspirin, clopidogrel, and ticagrelor) were orally administered before the thrombus induction.

Results: Edoxaban (0.3-3 mg/kg), clopidogrel (1-10 mg/kg), aspirin (10-100 mg/kg), and ticagrelor (0.3-3 mg/kg) exerted significant and dose-dependent antithrombotic effects in a rat stent thrombosis model. The effect of edoxaban was comparable to that of antiplatelet agents. The combination of submaximal doses of edoxaban and clopidogrel or aspirin significantly potentiated the antithrombotic effects compared with antiplatelet agents alone.

Conclusion: These results suggest that edoxaban alone and in combination with clopidogrel or aspirin are promising antithrombotic therapies for the prevention of stent thrombosis.
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http://dx.doi.org/10.1159/000494059DOI Listing
March 2019

Prevention of arterial thrombosis by edoxaban, an oral factor Xa inhibitor in rats: monotherapy and in combination with antiplatelet agents.

Eur J Pharmacol 2016 Sep 7;786:246-252. Epub 2016 Jun 7.

Biological Research Laboratories, R & D Division, Daiichi Sankyo Co., Ltd, Tokyo, Japan. Electronic address:

In addition to platelet aggregation, coagulation activation is considered to be involved in arterial thrombosis. In this study, we determined antithrombotic effects of edoxaban, an oral factor Xa (FXa) inhibitor, as both a monotherapy and in combination with antiplatelet agents in a rat model of arterial thrombosis. We further examined its effects on a procoagulant biomarker and bleeding. Arterial thrombosis was induced by topical application of 15% ferric chloride to rat abdominal aortas. Bleeding time was measured by a tail incision method. Edoxaban, clopidogrel, and aspirin were orally administered 30min, 4h, and 2h before thrombus or bleeding induction. As a biomarker of coagulation activation, plasma thrombin-antithrombin complex (TAT) was measured. Edoxaban dose-dependently prevented arterial thrombosis in a manner comparable to clopidogrel and aspirin. The combination of edoxaban plus clopidogrel or edoxaban plus aspirin significantly potentiated the antithrombotic effects compared with these drugs alone. The combination of edoxaban and clopidogrel was more potent than clopidogrel and aspirin. Plasma TAT concentration was elevated after thrombus induction and suppressed by edoxaban and clopidogrel, but not by aspirin, suggesting P2Y12 receptor-mediated platelet procoagulant activity. Bleeding time was prolonged by the coadministration of edoxaban and clopidogrel, but not by edoxaban and aspirin. In conclusion, the present study demonstrates that the monotherapy with edoxaban and combination therapy with edoxaban plus clopidogrel or edoxaban plus aspirin are promising options for the prevention of arterial thrombosis as effective as the standard antiplatelet agents; however, a combination of edoxaban and clopidogrel increased the risk of bleeding.
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http://dx.doi.org/10.1016/j.ejphar.2016.06.011DOI Listing
September 2016

A direct thrombin inhibitor suppresses protein C activation and factor Va degradation in human plasma: Possible mechanisms of paradoxical enhancement of thrombin generation.

Thromb Res 2016 May 3;141:77-83. Epub 2016 Mar 3.

Biological Research Laboratories, R&D Division, Daiichi Sankyo Co., Ltd., 1-2-58 Hiromachi, Shinagawa-ku, Tokyo 140-8710, Japan. Electronic address:

We have demonstrated that antithrombin (AT)-independent thrombin inhibitors paradoxically increase thrombin generation (TG) in human plasma in a thrombomodulin (TM)- and protein C (PC)-dependent manner. We determined the effects of AT-independent thrombin inhibitors on the negative-feedback system, activation of PC and production and degradation of factor Va (FVa), as possible mechanisms underlying the paradoxical enhancement of TG. TG in human plasma containing 10nM TM was assayed by means of the calibrated automated thrombography. As an index of PC activation, plasma concentration of activated PC-PC inhibitor complex (aPC-PCI) was measured. The amounts of FVa heavy chain and its degradation product (FVa(307-506)) were examined by western blotting. AT-independent thrombin inhibitors, melagatran and dabigatran (both at 25-600nM) and 3-30μg/ml active site-blocked thrombin (IIai), increased peak levels of TG. Melagatran, dabigatran and IIai significantly decreased plasma concentration of aPC-PCI complex at 25nM or more, 75nM or more, and 10 and 30μg/ml, respectively. Melagatran (300nM) significantly increased FVa and decreased FVa(307-506). In contrast, a direct factor Xa inhibitor edoxaban preferentially inhibited thrombin generation (≥25nM), and higher concentrations were required to inhibit PC activation (≥150nM) and FVa degradation (300nM). The present study suggests that the inhibitions of protein C activation and subsequent degradation of FVa and increase in FVa by antithrombin-independent thrombin inhibitors may contribute to the paradoxical TG enhancement, and edoxaban may inhibit PC activation and FVa degradation as a result of TG suppression.
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http://dx.doi.org/10.1016/j.thromres.2016.03.005DOI Listing
May 2016

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.

Thromb Res 2016 May 26;141:17-21. Epub 2016 Feb 26.

Biological Research Laboratories, R & D Division, Daiichi Sankyo Co., Ltd, Tokyo, Japan. Electronic address:

Introduction: Tissue factor-induced platelet aggregation and factor Xa (FXa) activity bound to clot contribute to the formation and growth of thrombus. The effects of edoxaban, a direct FXa inhibitor, on these responses were determined and compared with that of fondaparinux, an antithrombin-dependent (indirect) FXa inhibitor.

Material And Methods: Human platelet aggregation was induced by human tissue factor (Dade Innovin or RecombiPlasTin) in platelet-rich plasma spiked with edoxaban or fondaparinux. Clot formed from human whole blood was incubated with 0.9μM prothrombin in the absence or presence of FXa inhibitors. As the index of FXa activity, the amount of prothrombin fragment F1+2 was measured with an ELISA. Free FXa activity was measured using human FXa and its chromogenic substrate S-2222.

Results: Edoxaban inhibited tissue factor-induced platelet aggregation in a concentration-dependent manner with the IC50 values of 150 and 110nM for Dade Innovin and RecombiPlasTin-induced platelet aggregation, respectively. At 1μM, edoxaban completely inhibited the aggregation. Fondaparinux inhibited RecombiPlasTin-induced aggregation with the IC50 of 9.3μM, but did not show complete inhibition up to 30μM and had no effect on Dade Innovin-induced aggregation. Edoxaban inhibited both free and clot-bound FXa with the IC50 of 2.3 and 8.2nM, respectively. Fondaparinux inhibited free FXa (IC50 5.4nM), but 40-times higher concentration were required to inhibit clot-bound FXa (IC50 217nM).

Conclusions: Edoxaban, a direct FXa inhibitor, was a more potent inhibitor of tissue factor-induced platelet aggregation and clot-bound FXa than fondaparinux, an indirect FXa inhibitor.
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http://dx.doi.org/10.1016/j.thromres.2016.02.028DOI Listing
May 2016

Laboratory measurements of the oral direct factor Xa inhibitor edoxaban: comparison of prothrombin time, activated partial thromboplastin time, and thrombin generation assay.

Am J Clin Pathol 2015 Feb;143(2):241-7

From Biological Research Laboratories, R &D Division, Daiichi Sankyo, Tokyo, Japan.

Objectives: Edoxaban, an oral direct factor Xa inhibitor, does not require routine monitoring. However, assessment of the anticoagulant effects may be required in certain situations.

Methods: We investigated the effects of edoxaban on prothrombin time (PT), activated partial thromboplastin time (aPTT), and thrombin generation using human platelet-poor plasma (PPP) or platelet-rich plasma (PRP).

Results: Edoxaban concentration-dependently prolonged PT and aPTT. There was a considerable variation in the magnitude of PT prolongation among the reagents used. The variability in aPTT prolongation among the reagents was smaller than that of PT. Edoxaban concentration-dependently inhibited thrombin generation, with a more potent effect seen in PPP than in PRP. Thrombin generation assay was three times more sensitive to edoxaban than PT and aPTT.

Conclusions: PT had disadvantages of a large variability among different PT reagents. aPTT could be used as a conventional and convenient test with a smaller variation among reagents. Thrombin generation was the most sensitive assay.
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http://dx.doi.org/10.1309/AJCPQ2NJD3PXFTUGDOI Listing
February 2015

Treatment of venous thrombosis with an oral direct factor Xa inhibitor edoxaban by single and multiple administrations in rats.

Eur J Pharmacol 2014 Nov 30;742:15-21. Epub 2014 Aug 30.

Biological Research Laboratories, R & D Division, Daiichi Sankyo Co., Ltd., 1-2-58 Hiromachi, Shinagawa-ku, Tokyo 140-8710, Japan.

Edoxaban is an oral and direct activated factor X inhibitor. In this study, the acute treatment effect of edoxaban on venous thrombosis is investigated in rats by single and multiple administrations, and compared to the conventional parenteral anticoagulants, enoxaparin and fondaparinux. Venous thrombus was induced in the inferior vena cava by partial stenosis plus topical application of 10% ferric chloride for 5min. After 1-h thrombus maturation, oral edoxaban and subcutaneous enoxaparin and fondaparinux were given. In the single administration experiment, thrombus weight was measured 1 or 4h after thrombus induction. In the multiple administration experiments, edoxaban was orally administered once daily (QD) and twice daily (BID) for 3 days. In the single administration experiment, oral administration of edoxaban (3.0 and 10mg/kg) 1h after thrombus formation significantly regressed the venous thrombus compared to the thrombus at 1h after thrombus formation. Similarly the significant venous thrombus regression was observed with enoxaparin (10mg/kg) and fondaparinux (0.30-3.0mg/kg). In the multiple administration experiment, both QD and BID administration of edoxaban at daily doses of 5 and 10mg/kg exerted significant treatment effects. QD administration of edoxaban including lower doses (1-10mg/kg) significantly reduced thrombus weight. Edoxaban administered QD and BID was effective in the treatment of venous thrombosis, and the treatment effect of edoxaban was comparable to the conventional parenteral anticoagulants. These data demonstrate the potential of edoxaban as an oral anticoagulant in the acute treatment of venous thromboembolism.
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http://dx.doi.org/10.1016/j.ejphar.2014.08.020DOI Listing
November 2014

Comparison of antithrombotic and hemorrhagic effects of edoxaban, a novel factor Xa inhibitor, with unfractionated heparin, dalteparin, lepirudin and warfarin in rats.

Thromb Res 2013 Aug 12;132(2):234-9. Epub 2013 Jun 12.

Biological Research Laboratories, R & D Division, Daiichi Sankyo Co., Ltd. Electronic address:

Background: Edoxaban is a novel, potent and orally active direct Factor Xa (FXa) inhibitor under development for prophylaxis and treatment of thromboembolic diseases. Properties of dose response and margin of safety of anticoagulants are the key factors for a positive risk/benefit of novel oral anticoagulants.

Objectives: To compare the dose response of antithrombotic effect and margin of safety between antithrombotic and hemorrhagic effects of edoxaban with conventional anticoagulants, unfractionated heparin (UFH), dalteparin (low molecular weight heparin), lepirudin, and warfarin in rat models of thrombosis and hemorrhage.

Methods: Rats were treated with edoxaban, UFH, dalteparin, and lepirudin by continuous intravenous (iv) infusion, or with oral warfarin for 4 days before inducing thrombosis or bleeding. Thrombosis was induced by inserting a platinum wire into the inferior vena cava for 60 minutes. Tail template bleeding time was measured after making an incision on the tail.

Results: In rats, iv infusion of edoxaban inhibited venous thrombosis in a dose-dependent manner. The other anticoagulants also exerted dose-dependent antithrombotic effects. The slopes of the dose-response curves of edoxaban were significantly shallower than the slopes of UFH, dalteparin, and warfarin. At supratherapeutic doses, edoxaban prolonged bleeding time in a rat tail bleeding model. To determine bleeding risk, the margins between antithrombotic and bleeding-time prolongation were compared. The margins of safety of edoxaban were wider than those of UFH, dalteparin, lepirudin, and warfarin.

Conclusions: These results suggest that edoxaban may be more easily controlled and has the potential for a more positive risk/benefit ratio compared to conventional anticoagulants.
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http://dx.doi.org/10.1016/j.thromres.2013.05.020DOI Listing
August 2013

Impact of antithrombin deficiency on efficacy of edoxaban and antithrombin-dependent anticoagulants, fondaparinux, enoxaparin, and heparin.

Thromb Res 2013 Jun 11;131(6):540-6. Epub 2013 May 11.

Biological Research Laboratories, R&D Division, Daiichi Sankyo Co., Ltd., 1-2-58 Hiromachi, Shinagawa-ku, Tokyo 140-8710, Japan.

Introduction: Oral factor Xa (FXa) inhibitors are a novel class of anticoagulants that, unlike heparins, are expected to demonstrate antithrombotic effects independent of plasma antithrombin (AT) concentrations. We utilized heterozygous AT-deficient (AT+/-) mice to determine the impact of AT deficiency on anticoagulant and antithrombotic effects of edoxaban, a direct FXa inhibitor, and compared with heparins (fondaparinux, enoxaparin, and unfractionated heparin [UHF]).

Materials And Methods: The effects of edoxaban and heparins on in vitro prothrombin time and activated partial thromboplastin time were measured in plasma obtained from wild type (AT+/+) and AT+/- male mice. To assess the antithrombotic effects of these anticoagulants in vivo, venous thrombosis was induced in the inferior vena cava by FeCl3 treatment. Potency ratios of antithrombotic effects in AT+/- compared with AT+/+ mice were analyzed by a parallel line assay.

Results: In vitro studies demonstrated that the clotting-time prolongation effects of edoxaban were not affected by heterozygous AT deficiency whereas those of AT-dependent anticoagulants were attenuated. In AT+/- mice, the antithrombotic effects of AT-dependent anticoagulants were less potent than those in AT+/+ mice. In contrast, edoxaban was equipotent in preventing thrombus formation in both wild-type and AT-deficient mice. The attenuated antithrombotic effects of fondaparinux, enoxaparin, and UFH in AT-deficient mice were restored by AT supplementation. Edoxaban exerts a comparable antithrombotic effect even in mice with low plasma AT antigen and activity to that in wild-type mice.

Conclusion: Edoxaban may potentially be prioritized over AT-dependent anticoagulants in patients with lower plasma AT concentration.
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http://dx.doi.org/10.1016/j.thromres.2013.04.016DOI Listing
June 2013

The effects of warfarin and edoxaban, an oral direct factor Xa inhibitor, on gammacarboxylated (Gla-osteocalcin) and undercarboxylated osteocalcin (uc-osteocalcin) in rats.

Thromb Res 2013 Jan 19;131(1):59-63. Epub 2012 Sep 19.

Biological Research Laboratories, R&D Division, Daiichi Sankyo Co., Ltd., 1-2-58 Hiromachi, Shinagawa-ku, Tokyo 140-8710, Japan.

Introduction: Osteocalcin plays a role in bone homeostasis. The vitamin K cycle is essential for the gamma-carboxylation of glutamic acid residues in osteocalcin. Some evidence suggests that long-term warfarin therapy, which inhibits the vitamin K cycle and prevents gamma-carboxylation, is associated with increased bone-fracture risk. The aim of this study was to determine the effects of warfarin and edoxaban, a direct factor Xa inhibitor, on the serum concentration of total, gamma-carboxylated (Gla-osteocalcin) and undercarboxylated osteocalcin (uc-osteocalcin) in rats.

Materials And Methods: Rats received orally administered warfarin or edoxaban, and 24h later serum and plasma were prepared. Osteocalcin level in serum was measured with ELISA. A Gla-osteocalcin was precipitated by the addition of hydroxyapatite, and the resulting supernatant was used for measuring uc-osteocalcin. Prothrombin time (PT) of plasma was also measured.

Results: Warfarin at 1mg/kg (a dose which prolonged PT 2.62-fold) markedly increased the serum level of uc-osteocalcin and slightly increased the total osteocalcin level compared with control in rats. Serum Gla-osteocalcin significantly decreased by warfarin. Edoxaban at 1mg/kg (an antithrombotic dose) and 54mg/kg (a dose which prolonged PT 2.25-fold) had no effects on total, uc-, and Gla-osteocalcin levels.

Conclusions: This study demonstrates that warfarin impaired the carboxylation of osteocalcin in rats. In contrast, edoxaban at or higher doses than needed for an antithrombotic effect sustained the circulating Gla-osteocalcin level. These findings suggest that edoxaban has no effects on the production of Gla-osteocalcin and thus, may have a lower risk of adverse effects on bone health.
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http://dx.doi.org/10.1016/j.thromres.2012.08.304DOI Listing
January 2013

Comparison of antithrombotic and haemorrhagic effects of edoxaban, an oral direct factor Xa inhibitor, with warfarin and enoxaparin in rats.

Thromb Res 2012 Sep 29;130(3):514-9. Epub 2012 May 29.

Biological Research Laboratories, R & D Division, Daiichi Sankyo Co., Ltd., 1-2-58 Hiromachi, Shinagawa-ku, Tokyo 140–8710, Japan.

Introduction: Factor Xa (FXa) is a key serine protease in the coagulation cascade and a promising target for a new antithrombotic agent. Edoxaban is an oral, selective and direct FXa inhibitor. The objective of this study was to compare the antithrombotic and haemorrhagic effects of edoxaban with clinically available anticoagulants, warfarin and enoxaparin, in rat models of thrombosis and haemorrhage.

Methods: Rats were treated with single oral administration of edoxaban, repeated oral dosing of warfarin for 4 days and single subcutaneous administration of enoxaparin before thrombosis or haemorrhage induction. Thrombosis was induced by the insertion of a platinum wire into the inferior vena cava for 60 min. Tail template bleeding time was measured after making an incision on the tail.

Results: Edoxaban at 0.3, 1 and 3mg/kg exerted dose-dependent and significant inhibition of venous thrombus formation. The 50% thrombus inhibition dose (ED(50)) was 1.9 mg/kg. At supra-therapeutic doses (10 and 20mg/kg), edoxaban significantly but moderately (less than 2-fold) prolonged bleeding time. Warfarin and enoxaparin also dose-dependently inhibited venous thrombosis and prolonged bleeding time. The ED(50) values of warfarin and enoxaparin were 0.12 mg/kg and 500 IU/kg, and the 2-fold bleeding time prolongation doses (BT2) were 0.16 mg/kg and 1700 IU/kg, respectively. The safety margin (ratio of BT2 to ED(50)) of edoxaban (>10.5) was greater than those of warfarin (1.3) and enoxaparin (3.4).

Conclusions: Edoxaban inhibited venous thrombosis comparably to warfarin and enoxaparin, and the attendant bleeding risk of edoxaban was lower than that of warfarin and enoxaparin in rats.
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http://dx.doi.org/10.1016/j.thromres.2012.05.008DOI Listing
September 2012

Reversal of anticoagulant effects of edoxaban, an oral, direct factor Xa inhibitor, with haemostatic agents.

Thromb Haemost 2012 Feb 21;107(2):253-9. Epub 2011 Dec 21.

Daiichi Sankyo Co., Ltd. – Biological Research Laboratories, Tokyo, Japan.

Edoxaban, an oral, direct factor Xa inhibitor, has a similar or low incidence of bleeding events compared with other anticoagulants in clinical trials. Therefore, agents to reverse the anticoagulant effects of edoxaban could be desirable in emergency situations. In this study, the reversal effects of haemostatic agents were determined on prothrombin time (PT) prolongation in vitro and bleeding time prolongation in vivo by edoxaban. PT using human plasma was measured in the presence of edoxaban at therapeutic and excess concentrations with the haemostatic agents, prothrombin complex concentrate (PPSB-HT), activated prothrombin complex concentrate (Feiba), and recombinant factor VIIa (rFVIIa). In rats, rFVIIa and Feiba was given during intensive anticoagulation with edoxaban. The haemostatic effect was evaluated in a model of planta template bleeding and a potential prothrombotic effect was evaluated in a venous thrombosis model. PPSB-HT, Feiba, and rFVIIa concentration-dependently shortened PT prolonged by edoxaban. Among these, rFVIIa and Feiba showed potent activities in reversing the PT prolongation by edoxaban. rFVIIa (1 and 3 mg/kg, i.v.) and Feiba (100 U/kg, i.v.) significantly reversed edoxaban (1 mg/kg/h)-induced prolongation of bleeding time in rats. In a rat venous thrombosis model, no potentiation of thrombus formation was observed when the highest dose (3 mg/kg) of rFVIIa was added to edoxaban (0.3 and 1 mg/kg/h) compared with the control. The present study indicated that rFVIIa, Feiba, and PPSB-HT have the potential to be reversal agents for edoxaban.
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http://dx.doi.org/10.1160/TH11-09-0668DOI Listing
February 2012

Comparison of antithrombotic efficacy between edoxaban, a direct factor Xa inhibitor, and fondaparinux, an indirect factor Xa inhibitor under low and high shear rates.

Thromb Haemost 2011 Dec 22;106(6):1062-8. Epub 2011 Sep 22.

Biological Research Laboratories, R&D Division, Daiichi Sankyo Co., Ltd., 1-2-58 Hiromachi, Shinagawa-ku, Tokyo 140-8710, Japan.

Edoxaban is an oral, direct factor Xa (FXa) inhibitor under late-phase clinical development. This study compared the antithrombotic efficacy of edoxaban with that of an indirect FXa inhibitor, fondaparinux, in in vivo venous and arterial thrombosis models and in ex vivo perfusion chamber thrombosis model under low and high shear rates in rats. Venous and arterial thrombi were induced by platinum wire insertion into the inferior vena cava and by application of FeCl₃ to the carotid artery, respectively. The perfusion chamber thrombus was formed by blood perfusion into a collagen-coated capillary at 150 s⁻¹ (low shear rate) and 1,600 s⁻¹ (high shear rate). Effective doses of edoxaban that reduced thrombus formation by 50% (ED₅₀) in venous and arterial thrombosis models were 0.076 and 0.093 mg/kg/h, respectively. In contrast, ED₅₀ of fondaparinux in the arterial thrombosis model (>10 mg/kg/h) was markedly higher compared to ED₅₀ in the venous thrombosis model (0.021 mg/kg/h). In the perfusion chamber thrombosis model, the ratio of ED₅₀ under high shear rate (1.13 mg/kg/h) to that under low shear rate (0.63 mg/kg/h) for edoxaban was 1.9, whereas that for fondaparinux was more than 66. While the efficacy of fondaparinux markedly decreased in arterial thrombosis and in a high-shear state, edoxaban exerted consistent antithrombotic effects regardless of flow conditions. These results suggest that shear rate is a key factor in different antithrombotic effects between edoxaban and fondaparinux.
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http://dx.doi.org/10.1160/TH11-07-0451DOI Listing
December 2011