Evaluation of AR-H067637, the active metabolite of the new direct thrombin inhibitor AZD0837, in models of venous and arterial thrombosis and bleeding in anaesthetised rats

2010 ◽  
Vol 104 (12) ◽  
pp. 1242-1249 ◽  
Author(s):  
Susanne Pehrsson ◽  
Karin Johansson ◽  
Magnus Kjaer ◽  
Margareta Elg

SummaryAZD0837, currently in clinical development, is a once-daily oral anticoagulant that is bioconverted to AR-H067637, a selective, reversible direct thrombin inhibitor (DTI). When developing a new DTI, the anti-thrombotic effects are commonly investigated in in vivo animal models; this report shows the effect of AR-H067637 in venous and arterial thrombosis and bleeding models in anaesthetised rats. Thrombus formation was induced by topical application of ferric chloride to the carotid artery or to the caval vein with partial stasis. Cutaneous incision bleeding time and muscle transection blood loss were assessed, with or without acetylsalicylic acid (ASA). Activated partial thromboplastin time (APTT), ecarin coagulation time (ECT) and thrombin coagulation time (TCT) were used as plasma biomarkers of anticoagulant effect. Dalteparin was used as a reference compound. AR-H067637, given by continuous infusion, displayed a dose-dependent antithrombotic effect, with 50% inhibition (IC50) of thrombus size in venous and arterial thrombosis models obtained at plasma concentrations of 0.13 μM and 0.55 μM, respectively, without increased bleeding. Dose-dependent increased bleeding and blood loss were seen at plasma concentrations ≥1 μM AR-H067637. At the highest AR-H067637 plasma concentration tested, bleeding time and blood loss increased two and four times the vehicle group. Addition of ASA moderately potentiated bleeding time and blood loss. APTT, ECT and TCT were dose-dependently prolonged. These studies demonstrate that the DTI AR-H067637 inhibits thrombus formation in rat venous and arterial thrombosis models with no or minor increases in bleeding.

2001 ◽  
Vol 86 (12) ◽  
pp. 1512-1520 ◽  
Author(s):  
Chi-ho Yun ◽  
Hyoung-sik Seo ◽  
Takaki Koga ◽  
Takashi Dan ◽  
Hak-yeop Kim ◽  
...  

SummaryThe antithrombotic efficacy of AT-1459, a novel, direct thrombin inhibitor (Ki = 4.9 nM) was evaluated in rat models of venous thrombosis combined with a bleeding time test and arterial thrombosis.After drugs were given by i. v. bolus injection plus a continuous infusion, the ID50 (a dose that exhibits 50% inhibition of thrombus formation over each vehicle group) values of AT-1459, argatroban, and dalteparin were 0.04 mg/kg plus 0.04 mg/kg/h, 0.1 mg/kg plus 0.4 mg/ kg/h, and 13.0 IU/kg plus 26.0 IU/kg/h, respectively, in the venous thrombosis study. The BT2 (a dose that causes 2-fold prolongation of bleeding time over each vehicle group) values of AT-1459, argatroban, and dalteparin were 0.9 mg/kg plus 0.9 mg/kg/h, 1.0 mg/kg plus 0.6 mg/kg/h, and 345.5 IU/kg plus 691.0 IU/kg/h in the rat tail transection model. The ratios of BT2/ID50 of AT-1459, argatroban, and dalteparin were 22.5, 10.0, and 26.6, respectively.In a rat model of arterial thrombosis induced by topical FeCl2 application, intravenous administration of AT-1459, argatroban, and dalteparin improved the vessel patency significantly (P <0.01) at 0.6 mg/kg plus 0.6 mg/kg/h, 0.6 mg/kg plus 2.4 mg/kg/h, and 300 IU/kg plus 600 IU/kg/h, respectively.The oral antithrombotic effect of AT-1459 lasted for 6 after administering 30 mg/kg and improved the vessel patency significantly 1 h after administering the same dose in venous and arterial thrombosis models, respectively, with a rapid onset of action. Warfarin also inhibited thrombus weight and improved the vessel patency significantly after oral administration of 0.3 mg/kg for three consecutive days in the same study. The antithrombotic and hemorrhagic effects of all drugs studied were correlated with plasma concentration or clotting times.These results suggest that AT-1459 may be clinically useful as an orally available antithrombotic agent for the prevention of venous and arterial thrombosis.


Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 4049-4049
Author(s):  
Margareta Elg ◽  
Helen Zachrisson

Abstract AR-H067637 is a direct thrombin inhibitor derived in vivo from the orally available prodrug AZD0837. AR-H067637 is a reversible and selective direct thrombin inhibitor, which has an inhibition constant, Ki, of 2–4 nmol/L against human alpha-thrombin. During early development of a new anticoagulant drug, data on antithrombotic doses from animal studies may help guide selection of the dose to use in initial human studies. In the present study, using a flow chamber model developed by Badimon and colleagues (Badimon L, et al. J Lab Clin Med1987;110:706–718), the antithrombotic effect of AR-H067637 was evaluated using pig aorta and human whole blood. Following collection of informed consent, blood was taken from 11 healthy subjects into citrate-containing (10%, 0.109 M) tubes. Subjects were not permitted to receive medication for 7 days prior to blood collection. Blood was also collected in EDTA-containing tubes for cell counting. Denuded pig aorta pieces were used as the thrombogenic surface in the flow chamber. AR-H067637 was added to the blood at final blood concentrations ranging from 0.01 to 10 μmol/L, corresponding to plasma concentrations of 0.02 to 16 μmol/L. The blood was drawn for 5 minutes through the flow chamber with a shear of 220−s which is comparable with venous flow rate. The thrombus formed inside the chamber was degraded by plasmin, and platelets attached to the thrombus were lysed. The degradation product of fibrin, D-dimer, and the expression of the platelet cell adhesion molecule P-selectin were used as indirect measures of fibrin and platelet content in the thrombus, respectively. The anticoagulant effect of AR-H067637 was determined using the activated partial thromboplastin time (APTT) and prothrombin time (PT) assays. When using D-dimer levels as a measure of thrombus size, 25%, 50% and 75% thrombus inhibition was estimated to occur at AR-H067637 plasma concentrations of 0.21, 0.48 and 1.32 μmol/L, respectively. A significant inhibition of P-selectin expression by AR-H067637 was seen only at the highest concentration. APTT and PT were shown to be prolonged in a concentration-dependent manner; 50% inhibition of thrombus formation on the pig aorta was obtained at 1.8 and 1.2 times prolongations of APTT and PT, respectively. Hematological parameters such as WBC, RBC, HCT and platelets were all within the normal range. In conclusion, this study demonstrates that AR-H067637, the active metabolite of the oral prodrug AZD0837, has antithrombotic effects, causing concentration-dependent inhibition of thrombus formation measured as fibrin degradation products on the denuded pig aorta. Only a small effect at the highest concentration was observed on inhibition of platelet content in the thrombus, measured by P-selectin. This is in accordance with thrombin being a very potent platelet agonist. Therefore, higher concentrations of a thrombin inhibitor are needed to totally prevent platelet activation and aggregation, compared to those needed to prevent fibrin formation. APTT and PT prolongation correlated with the antithrombotic effect of AR-H067637 with &gt;75% inhibition of fibrin formation at APTT and PT prolongations of 2.4 and 1.7, respectively.


2008 ◽  
Vol 100 (10) ◽  
pp. 670-677 ◽  
Author(s):  
Alexandre Fontayne ◽  
Muriel Meiring ◽  
Seb Lamprecht ◽  
Jan Roodt ◽  
Eddy Demarsin ◽  
...  

SummaryThe Fab-fragment of 6B4, a murine monoclonal antibody targeting the human platelet glycoprotein (GP) Ibα and blocking the binding of von Willebrand factor (VWF), is a powerful antithrombotic. In baboons, this was without side effects such as bleeding or thrombocytopenia. Recently, we developed a fully recombinant and humanized version of 6B4-Fab-fragment, h6B4-Fab, which maintains its inhibitory capacities in vitro and ex vivo after injection in baboons. We here investigated the antithrombotic properties, the effect on bleeding time and blood loss and initial pharmacokinetics of h6B4-Fab in baboons. The antithrombotic effect of h6B4-Fab on acute platelet-mediated thrombosis was studied in baboons where thrombus formation is induced at an injured and stenosed site of the femoral artery, allowing for cyclic flow reductions (CFRs) which are measured on an extracorporeal femoral arteriovenous shunt. Injection of 0.5 mg/kg h6B4-Fab significantly reduced the CFRs by 80%, whereas two extra injections, resulting in cumulative doses of 1.5 and 2.5 mg/kg, completely inhibited the CFRs. Platelet receptor occupancy, plasma concentrations and effects ex vivo were consistent with what was previously observed. Finally, minimal effects on bleeding time and blood loss, no spontaneous bleeding and no thrombocytopenia were observed. We therefore conclude that h6B4-Fab maintains the antithrombotic capacities of the murine 6B4-Fab, without causing side effects and therefore can be used for further development.


1987 ◽  
Vol 58 (02) ◽  
pp. 764-767 ◽  
Author(s):  
Y Cadroy ◽  
C Caranobe ◽  
A Bernat ◽  
J P Maffrand ◽  
P Sié ◽  
...  

SummaryThis study reports on (he anticoagulant, antithrombotic and bleeding effects of a new synthetic direct thrombin inhibitor (SDTI) in comparison with standard heparin (SH). The anticoagulant effect was determined with the thrombin clotting time (TCI) and the activated partial thromboplastin time (APTT). SDTI was more potent than SII in prolonging the TCT, but as potent as SH in prolonging the APTT. The antithrombotic effect was determined using a modified Wessler model in the rabbit, either 30 min after a continuous IV infusion of increasing doses or at various times after a single SC injection (20 mg/kg). After continuous IV infusion of 187 μg/kg/h of SDTI and of 60 μg/kg/h of SH, significant thrombus prevention effects were obtained (59 and 57% respectively). Increasing the dose of SDTI up to 3000 μg/kg/h did not significantly impiove the antithrombotic effect. After SC injection, a significant antihrombotic effect was observed for 12 h with SDTI but for more than 24 h with SH. The bleeding effect was studied using the rabbit ear model 15 min after a continuous infusion of 7.5 and 15 mg/kg/h: the amounts of blood loss were dose-dependent and comparable for SDTI and SH. These studies also indicated that SDTI possesses a considerable shorter half-life in comparison with SH. Accordingly, the ex vivoconcentrations generated after continuous IV infusion or SC injection of the same dose were higher for SH than for the SDTI.


1997 ◽  
Vol 78 (05) ◽  
pp. 1366-1371 ◽  
Author(s):  
Yoshiyuki Morishima ◽  
Kiyoshi Tanabe ◽  
Yasuko Terada ◽  
Tsuyoshi Hara ◽  
Satoshi Kunitada

Summary(+)-2S-2-[4-[[(3S)-l-acetimidoyl-3- pyrrolidinyl]oxy]phenyl]-3-[7-amidino-2-naphthyl]propanoic acid hydrochloride pentahydrate (DX- 9065a) is an antithrombin III (AT III)-independent and selective inhibitor of activated blood coagulation factor X (FXa). The aim of the present study was to compare the antithrombotic and hemorrhagic effects of DX-9065a with a direct thrombin inhibitor and AT Ill-dependent anticoagulants in rat models of thrombosis and bleeding.Rats were administered intravenously DX-9065a (0.1-1 mg/kg/h), argatroban (0.1-1 mg/k/h), low molecular weight heparin (25-100 anti- XaU/kg/h), unfractionated heparin (25-100 anti-XaU/kg/h) or Orgaran (30-300 anti-XaU/kg/h) for 1 h. DX-9065a dose-dependently inhibited both thrombus formation and elevation in plasma thrombin-AT III complex (TAT) level in a copper wire-inserted arteriovenous (AV) shunt model in rats. The dose required for 50% inhibition of thrombus formation was 0.27 mg/kg/h. DX-9065a did not prolong transection bleeding time up to 7.78 mg/kg/h. Argatroban and AT Ill-dependent anticoagulants also inhibited both thrombus formation and TAT elevation, but prolonged bleeding time at a slightly higher dose than the effective dose. These results suggest that direct and selective inhibition of factor Xa by DX-9065a is preferable for the treatment of thrombosis in the aspect of lack of compromising primary hemostasis.


2006 ◽  
Vol 96 (10) ◽  
pp. 446-453 ◽  
Author(s):  
Jørgen Ingerslev ◽  
Benny Sørensen

SummaryDirect thrombin inhibitors have proven efficacious in prevention of venous thromboembolism. Bleeding complications are rare, but in case of acute serious bleeding, an effective and instant haemostatic intervention may be required. In the present study it was demonstrated that the direct thrombin inhibitor melagatran induces dose-dependent abnormalities in whole blood (WB) clotting profiles as recorded bya recently described modified thrombelastographic model, and that rFVIIa or APCC are capable of improving the haemostatic capacity. Experiments were performed using WB from 30 healthy males. In-vitro titration experiments (n=10) with addition of melagatran to WB corresponding to plasma concentrations ranging from 0 to 5.0 µM (12 steps) showed a dose-dependent prolongation of the clot initiation and characteristic decrease of the maximum rate of clot propagation. In-vitro intervention studies (n=20) were completed with four different concentrations of melagatran as well as addition of four different levels of rFVIIa or APCC. At all tested concentrations of melagatran, rFVIIa significantly shortened the melagatran-induced prolonged clot initiation but induced only minor improvements of the reduced clot propagation. In contrast, APCC significantly and dose-dependently shortened the clot initiation and accelerated the clot propagation. In conclusion, our thrombelastographic model appears useful for evaluating the effect of direct thrombin inhibitors on dynamic WB clot formation and rFVIIa, but especially APCC significantly improved theWB clot formation. The pronounced stabilizing effect of APCC may be caused by its content of prothrombin and activated coagulation factors.


Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 3155-3155 ◽  
Author(s):  
Minori Saitoh ◽  
Seiji Kaku ◽  
Toshiyuki Funatsu ◽  
Hiroyuki Koshio ◽  
Tsukasa Ishihara ◽  
...  

Abstract YM150, an oral, direct factor Xa inhibitor, is currently being evaluated in Phase II studies as prophylaxis for venous thromboembolism in patients undergoing orthopedic surgery. In the present study, we compared the antithrombotic effect of YM150 with the effects of antithrombin-dependent indirect factor Xa inhibitors, enoxaparin and fondaparinux, and a direct thrombin inhibitor, ximelagatran, in ferric chloride (FeCl3)-induced venous and arterial thrombosis models in rats. We also evaluated the bleeding time in a rat tail transection model. Prior to any experimentation, male Sprague-Dawley rats, which had been fasting for at least 12 h, were anesthetized with urethane (1 g/kg, i.p.) or sodium pentobarbital (50 mg/kg, i.p.). YM150 and ximelagatran were administered intra-duodenally, and both enoxaparin and fondaparinux were given subcutaneously, 30 min prior to induction of thrombus or tail transection. All animals were kept warm with a heating pad during the experiments. Venous and arterial thromboses were produced, respectively, by the 5 min application of 8% FeCl3 soaked filter paper to the external surface of the inferior vena cava and 35% FeCl3 soaked filter paper to the abdominal aorta. The venous thrombosis model was supplemented by using a silk thread venous stenosis. To measure bleeding time, the tail was transected 5 mm from its tip. Blood was carefully blotted each 30 sec with a filter paper. Once a blood stain was observed, we defined bleeding as blood flow sustained over 30 sec. Bleeding time was defined as the sum of the bleeding periods during the 60 min observation in each animal. Administration of intra-duodenal YM150 significantly inhibited both venous and arterial thrombus formation at doses of 10 mg/kg or greater, and 3 mg/kg or greater, respectively. This indicated that YM150 promoted an antithrombotic effect at similar dose ranges for venous and arterial thromboses. In contrast, YM150 did not prolong the bleeding time at doses up to 30 mg/kg. Venous thrombus formation was inhibited by subcutaneous enoxaparin at doses of 100 IU/kg or greater and fondaparinux at doses of 0.03 mg/kg or greater. Arterial thrombus formation was inhibited by subcutaneous administration of 1000 IU/kg enoxaparin and 3 mg/kg fondaparinux. The results indicated that 10–100 times higher doses of these antithrombotics were needed to inhibit arterial thrombosis. Furthermore, enoxaparin at doses of 300 IU/kg or greater and fondaparinux at doses of 1 mg/kg or greater, significantly prolonged the bleeding time, suggesting that these two medications may be associated with increased risk of hemorrhage at concentrations used to prevent arterial thrombosis. At doses of 1 mg/kg or greater, intra-duodenal ximelagatran inhibited both venous and arterial thrombus formation. The dose-response curve for ximelagatran tended to be steeper than that for other anticoagulants tested. Antithrombotic doses of ximelagatran (1 mg/kg or greater), produced similar prolongations of bleeding time as those seen with administration of enoxaparin and fondaparinux. In conclusion, YM150, an oral direct factor Xa inhibitor, shows promise as an antithrombotic drug with potentially wider safety margins than current antithrombin-dependent factor Xa inhibitors and a thrombin inhibitor.


1993 ◽  
Vol 69 (02) ◽  
pp. 157-163 ◽  
Author(s):  
Irving Fox ◽  
Adrian Dawson ◽  
Peter Loynds ◽  
Jane Eisner ◽  
Kathleen Findlen ◽  
...  

SummaryHirulog™ (BG8967) is a direct thrombin inhibitor built by rational design using the protein hirudin as a model (Maraganore et al. [1990]; Biochemistry 29: 7095–101). In order to evaluate the therapeutic potential for hirulog in the management of thrombotic disease, the tolerability and anticoagulant activity of the agent were examined in a study of human volunteers.In a randomized, placebo-controlled study (n = 54), the intravenous infusion of hirulog over 15 min showed a rapid, dose-dependent prolongation of activated partial thromboplastin time (APTT), prothrombin time (PT), and thrombin time (TT). There was a corresponding dose-dependent increase in plasma hirulog levels. The peptide was rapidly cleared with a half-life of 36 min and a total body clearance rate for the peptide of 0.43 1 kg−1 h−1. Similar activity was observed following subcutaneous injection but with sustained pharmacodynamic and pharmacokinetic behavior. There was a significant correlation between pharmacokinetic and pharmacodynamic variables for both intravenous (r = 0.8, p <0.001) and subcutaneous administration (r = 0.7, p = 0.002).To evaluate the possible interactions of aspirin on the tolerability and anticoagulant activity of intravenous hirulog, a cross-over design was employed in eight subjects. Aspirin administration did not modify the peptide’s activity. At the administered dose of 0.6 mg kg−1 h−1 for 2 h, hirulog infusion prolonged APTT from 230 to 260% baseline. The infusion of hirulog in subjects who had received aspirin was not associated with any significant changes in the template bleeding time.The final phase of the study examined the activity and tolerability of hirulog in ten subjects during prolonged intravenous infusions for up to 24 h. The peptide (0.3 mg kg−1 h−1) exhibited sustained anticoagulant activity with no evidence for a cumulative effect. During hirulog infusion, APTT was prolonged from 210 to 250% baseline.In all phases of the study, hirulog administration was generally well-tolerated.Our observations show that hirulog is an active antithrombin agent with excellent tolerability in humans. As a direct thrombin inhibitor, hirulog provides a novel approach for the management of thrombotic disease.


2011 ◽  
Vol 4 ◽  
pp. CMBD.S5118 ◽  
Author(s):  
Bernd Saugel ◽  
Roland M. Schmid ◽  
Wolfgang Huber

Heparin-induced thrombocytopenia (HIT) is a life-threatening adverse reaction to heparin therapy that is characterized by thrombocytopenia and an increased risk of venous and arterial thrombosis. According to guidelines, in patients with strongly suspected or confirmed HIT all sources of heparin have to be discontinued and an alternative, nonheparin anticoagulant for HIT treatment must immediately be started. For both the prophylaxis of thrombembolic events in HIT and the treatment of HIT with thrombosis the direct thrombin inhibitor argatroban is approved in the United States. The objective of this review is to describe the mechanism of action and the pharmacokinetic profile of argatroban, to characterize argatroban regarding its safety and therapeutic efficacy and to discuss its place in therapy in HIT.


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