Biochemical and Pharmacological Properties of SANORG 34006, a Potent and Long-Acting Synthetic Pentasaccharide

Blood ◽  
1998 ◽  
Vol 91 (11) ◽  
pp. 4197-4205 ◽  
Author(s):  
J.M. Herbert ◽  
J.P. Hérault ◽  
A. Bernat ◽  
R.G.M. van Amsterdam ◽  
J.C. Lormeau ◽  
...  
Keyword(s):  
Thrombin Generation ◽  
Ex Vivo ◽  
Thrombus Formation ◽  
Factor Xa ◽  
Therapeutic Index ◽  
Inhibitory Effect ◽  
Experimental Models ◽  
Treatment And Prevention ◽  
Long Acting

SANORG 34006 is a new sulfated pentasaccharide obtained by chemical synthesis. It is an analog of the “synthetic pentasaccharide” (SR 90107/ ORG 31540) which represents the antithrombin (AT) binding site of heparin. SANORG 34006 showed a higher affinity to human AT than SR 90107/ORG 31540 (kd = 1.4 ± 0.3 v 48 ± 11 nmol/L), and it is a potent and selective catalyst of the inhibitory effect of AT on factor Xa (1,240 ± 15 anti–factor Xa U/mg v850 ± 27 anti-factor Xa U/mg for SR 90107/ORG 31540). In vitro, SANORG 34006 inhibited thrombin generation occurring via both the extrinsic and intrinsic pathway. After intravenous (IV) or subcutaneous (SC) administration to rabbits, SANORG 34006 displayed a long-lasting anti–factor Xa activity and inhibition of thrombin generation (TG) ex vivo. SANORG 34006 was slowly eliminated after IV or SC administration to rats, rabbits, and baboons, showed exceptionally long half-lives (between 9.2 hours in rats and 61.9 hours in baboons), and revealed an SC bioavailability near 100%. SANORG 34006 displayed antithrombotic activity by virtue of its potentiation of the anti–factor Xa activity of AT. It strongly inhibited thrombus formation in experimental models of thromboplastin/stasis-induced venous thrombosis in rats (IV) and rabbits (SC) (ED50values = 40.0 ± 3.4 and 105.0 ± 9.4 nmol/kg, respectively). The duration of its antithrombotic effects closely paralleled the ex vivo anti–factor Xa activity. SANORG 34006 enhanced rt-PA–induced thrombolysis and inhibited accretion of125I-fibrinogen onto a preformed thrombus in the rabbit jugular vein suggesting that concomitant use of SANORG 34006 during rt-PA therapy might be helpful in facilitating thrombolysis and preventing fibrin accretion onto the thrombus under lysis. Contrary to standard heparin, SANORG 34006 did not enhance bleeding in a rabbit ear incision model at a dose that equals 10 times the antithrombotic ED50 in this species and, therefore, exhibited a favorable therapeutic index. We suggest that SANORG 34006 is a promising compound in the treatment and prevention of various thrombotic diseases.

Biochemical and Pharmacological Properties of SANORG 34006, a Potent and Long-Acting Synthetic Pentasaccharide

Blood ◽  
1998 ◽  
Vol 91 (11) ◽  
pp. 4197-4205 ◽  
Author(s):  
J.M. Herbert ◽  
J.P. Hérault ◽  
A. Bernat ◽  
R.G.M. van Amsterdam ◽  
J.C. Lormeau ◽  
...  
Keyword(s):  
Thrombin Generation ◽  
Ex Vivo ◽  
Thrombus Formation ◽  
Factor Xa ◽  
Therapeutic Index ◽  
Inhibitory Effect ◽  
Experimental Models ◽  
Treatment And Prevention ◽  
Long Acting

Abstract SANORG 34006 is a new sulfated pentasaccharide obtained by chemical synthesis. It is an analog of the “synthetic pentasaccharide” (SR 90107/ ORG 31540) which represents the antithrombin (AT) binding site of heparin. SANORG 34006 showed a higher affinity to human AT than SR 90107/ORG 31540 (kd = 1.4 ± 0.3 v 48 ± 11 nmol/L), and it is a potent and selective catalyst of the inhibitory effect of AT on factor Xa (1,240 ± 15 anti–factor Xa U/mg v850 ± 27 anti-factor Xa U/mg for SR 90107/ORG 31540). In vitro, SANORG 34006 inhibited thrombin generation occurring via both the extrinsic and intrinsic pathway. After intravenous (IV) or subcutaneous (SC) administration to rabbits, SANORG 34006 displayed a long-lasting anti–factor Xa activity and inhibition of thrombin generation (TG) ex vivo. SANORG 34006 was slowly eliminated after IV or SC administration to rats, rabbits, and baboons, showed exceptionally long half-lives (between 9.2 hours in rats and 61.9 hours in baboons), and revealed an SC bioavailability near 100%. SANORG 34006 displayed antithrombotic activity by virtue of its potentiation of the anti–factor Xa activity of AT. It strongly inhibited thrombus formation in experimental models of thromboplastin/stasis-induced venous thrombosis in rats (IV) and rabbits (SC) (ED50values = 40.0 ± 3.4 and 105.0 ± 9.4 nmol/kg, respectively). The duration of its antithrombotic effects closely paralleled the ex vivo anti–factor Xa activity. SANORG 34006 enhanced rt-PA–induced thrombolysis and inhibited accretion of125I-fibrinogen onto a preformed thrombus in the rabbit jugular vein suggesting that concomitant use of SANORG 34006 during rt-PA therapy might be helpful in facilitating thrombolysis and preventing fibrin accretion onto the thrombus under lysis. Contrary to standard heparin, SANORG 34006 did not enhance bleeding in a rabbit ear incision model at a dose that equals 10 times the antithrombotic ED50 in this species and, therefore, exhibited a favorable therapeutic index. We suggest that SANORG 34006 is a promising compound in the treatment and prevention of various thrombotic diseases.

SR123781A, a Synthetic Heparin Mimetic

2001 ◽  
Vol 85 (05) ◽  
pp. 852-860 ◽  
Author(s):  
J. P. Hérault ◽  
A. Bernat ◽  
P. Savi ◽  
P. Schaeffer ◽  
P. A. Driguez ◽  
...  
Keyword(s):  
Ex Vivo ◽  
Thrombus Formation ◽  
Vena Cava ◽  
Subcutaneous Administration ◽  
Factor Xa ◽  
Inhibitory Effect ◽  
Binding Domain ◽  
Heparin Binding ◽  
Venous Shunt

SummarySR123781A, a synthetic hexadecasaccharide comprising an anti-thrombin (AT) binding domain, a thrombin binding domain, and a neutral methylated hexasaccharide sequence, was obtained from glucose through a convergent synthesis. SR123781A showed high affinity for human AT (Kd = 58 ± 22 nM) and was a potent catalyst of its inhibitory effect with regard to factor Xa (IC50 = 77 ± 5 ng/ml – 297 ± 13 U/mg) and thrombin (IC50 = 4.0 ± 0.5 ng/ml – 150 ± 30 U/mg). SR123781A which acted exclusively via AT (no effect via heparin cofactor II at a concentration of 6 g/ml) inhibited thrombin generation occurring via both the extrinsic and intrinsic pathways in vitro in human plasma. SR123781A did not compete for 3H-heparin binding to PF4 and did not activate platelets in the presence of plasma from patients with heparin-induced thrombocytopenia. After intravenous or subcutaneous administration to rats, rabbits or baboons, SR123781A displayed prolonged anti-factor Xa and anti-factor IIa activity ex vivo. After intravenous injection to baboons, decreases of the anti-factor Xa and anti-thrombin activities were parallel and disappeared with the same pharmacodynamics. Intravenous administrations of SR123781A strongly inhibited thrombus formation in an experimental model of thromboplastin-induced venous thrombosis in rats with an ED50 value of 18 ± 0.1 g/kg (vs 77 ± 3 g/kg for heparin). SR123781A inhibited arterial thrombus formation induced on a silk thread in an arterio-venous shunt and in the vena cava (ED50 values of 225 ± 10 and 27 ± 8 g/kg, respectively). Compared to standard and low molecular weight heparin and to presently used drugs, SR123781A exhibited a highly favourable anti-thrombotic/bleeding ratio therefore showing that it might be considered as a promising compound in the treatment and prevention of various thrombotic diseases.

scholarly journals Heparin is more effective than apixaban in inhibiting in vitro contact activated coagulation

2020 ◽  
Vol 41 (Supplement_2) ◽  
Author(s):  
M.M Engelen ◽  
C Van Laer ◽  
M Jacquemin ◽  
C Vandenbriele ◽  
K Peerlinck ◽  
...  
Keyword(s):  
Thrombin Generation ◽  
Heart Valves ◽  
Thrombus Formation ◽  
Oral Anticoagulants ◽  
Direct Oral Anticoagulants ◽  
Factor Xa ◽  
Coagulation Factor ◽  
Mechanical Heart Valves ◽  
Contact Activation

Abstract Introduction Contact of blood with artificial surfaces such as mechanical support devices, catheters, and mechanical heart valves activates the contact activation (CA) pathway of coagulation. Furthermore, recent animal data and clinical studies suggest a more important contribution of CA in pathological thrombus formation in other cardiovascular diseases. Direct oral anticoagulants (DOACs) are recommended as first-line treatment in most patients who require long-term anticoagulation. However, because DOACs directly inhibit a single downstream coagulation factor (thrombin (fXIIa) or factor Xa (fXa)), it has been suggested that their efficacy could be reduced in the presence of strong activation of the CA pathway as compared to anticoagulants that target multiple, more upstream located coagulation factors. Purpose To compare the efficacy of a DOAC (apixaban) and heparin to suppress thrombin generation in the presence of strong CA pathway activation. Methods Pooled platelet-poor plasma was spiked with either apixaban (dissolved in DMSO and PBS) or unfractionated heparin to achieve therapeutic plasma levels. SynthASil, a commercially available mixture of phospholipids and silica, was used to stimulate the CA pathway in two different dilutions (1–80 and 5–80). Downstream coagulation was accessed by Thrombin Generation Test using Thrombinoscope by Stago and associated Thrombin Calibrator (activity 640 nM). The endogenous thrombin potential (area under the thrombin generation curve; ETP), peak thrombin generation (PTG), time to peak (ttPeak) and time to start (ttStart) were accessed. Results With decreasing concentrations of apixaban, stimulation with the lower dose SynthASil reveals an increasing ETP and PTG. As expected, ttPeak and ttStart decreased. Even supratherapeutic levels of apixaban (i.e. 1120 ng/mL) could not inhibit thrombin from being generated, in striking contrast with UFH where no thrombin was formed. Using a five times higher dose of SynthASil showed comparable ETP for all concentrations of apixaban, allocated around the control value. PTG, however, slightly increased with decreasing concentrations of apixaban. ttPeak and ttStart slightly decreased. Except for the subtherapeutic UFH concentration of 0,114 IU/mL, no thrombin was generated with UFH. Conclusion UFH is more effective in inhibiting downstream thrombin generation compared to apixaban as a response to activation of the CA pathway in vitro. These findings could help explain why direct inhibitors were not able to show non-inferiority in patients with mechanical heart valves and support the development of specific CA pathway inhibitors for patients with conditions that activate the CA pathway. Thrombin generation curves Funding Acknowledgement Type of funding source: None

scholarly journals Models and methods to characterise levonorgestrel release from intradermally administered contraceptives

2021 ◽  
Author(s):  
Adnan Al Dalaty ◽  
Benedetta Gualeni ◽  
Sion A. Coulman ◽  
James C. Birchall
Keyword(s):  
Ex Vivo ◽  
Extraction Procedure ◽  
In Vitro Release ◽  
Reversed Phase ◽  
Experimental Models ◽  
Detection Methods ◽  
Hormonal Contraceptives ◽  
Limit Of Quantification ◽  
Long Acting

AbstractMicroneedle (MN)-based technologies have been proposed as a means to facilitate minimally invasive sustained delivery of long-acting hormonal contraceptives into the skin. Intradermal administration is a new route of delivery for these contraceptives and therefore no established laboratory methods or experimental models are available to predict dermal drug release and pharmacokinetics from candidate MN formulations. This study evaluates an in vitro release (IVR) medium and a medium supplemented with ex vivo human skin homogenate (SH) as potential laboratory models to investigate the dermal release characteristics of one such hormonal contraceptive that is being tested for MN delivery, levonorgestrel (LNG), and provides details of an accompanying novel two-step liquid–liquid drug extraction procedure and sensitive reversed-phase HPLC–UV assay. The extraction efficiency of LNG was 91.7 ± 3.06% from IVR medium and 84.6 ± 1.6% from the medium supplemented with SH. The HPLC–UV methodology had a limit of quantification of 0.005 µg/mL and linearity between 0.005 and 25 µg/mL. Extraction and detection methods for LNG were exemplified in both models using the well-characterised, commercially available sustained-release implant (Jadelle®). Sustained LNG release from the implant was detected in both media over 28 days. This study reports for the first time the use of biologically relevant release models and a rapid, reliable and sensitive methodology to determine release characteristics of LNG from intradermally administered long-acting drug delivery systems. Graphical abstract

Inhibitory Effect of Piracetam on Platelet-rich Thrombus Formation in an Animal Model

1998 ◽  
Vol 79 (01) ◽  
pp. 222-227 ◽  
Author(s):  
F. Stockmans ◽  
W. Deberdt ◽  
Å. Nyström ◽  
E. Nyström ◽  
J. M. Stassen ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Ex Vivo ◽  
Peak Plasma ◽  
Thrombus Formation ◽  
Plasma Concentrations ◽  
Inhibitory Effect ◽  
Human Platelets ◽  
Cell Deformability

SummaryIntravenous administration of piracetam to hamsters reduced the formation of a platelet-rich venous thrombus induced by a standardised crush injury, in a dose-dependent fashion with an IC50 of 68 ± 8 mg/kg. 200 mg/kg piracetam also significantly reduced in vivo thrombus formation in rats. However, in vitro aggregation of rat platelets was only inhibited with piracetam-concentrations at least 10-fold higher than plasma concentrations (6.2 ± 1.1 mM) obtained in the treated animals. No effects were seen on clotting tests.In vitro human platelet aggregation, induced by a variety of agonists, was inhibited by piracetam, with IC50’s of 25-60 mM. The broad inhibition spectrum could be explained by the capacity of piracetam to prevent fibrinogen binding to activated human platelets. Ex vivo aggregations and bleeding times were only minimally affected after administration of 400 mg/kg piracetam i.v. to healthy male volunteers, resulting in peak plasma levels of 5.8 ± 0.3 mM.A possible antiplatelet effect of piracetam could be due to the documented beneficial effect on red blood cell deformability leading to a putative reduction of ADP release by damaged erythrocytes. However similarly high concentrations were needed to prevent stirring-induced “spontaneous” platelet aggregation in human whole blood.It is concluded that the observed antithrombotic action of piracetam cannot satisfactorily be explained by an isolated direct effect on platelets. An additional influence of piracetam on the rheology of the circulating blood and/or on the vessel wall itself must therefore be taken into consideration.

Effects of TAK-442, a Direct FXa Inhibitor, and Fondaparinux on Platelet-Associated Prothrombinase in the Balloon Injured Artery of Rats

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 4077-4077 ◽  
Author(s):  
Masaki Kawamura ◽  
Noriko Konishi ◽  
Hiroe Katsuhiko ◽  
Yasuhiro Imaeda ◽  
Takuya Fujimoto ◽  
...  
Keyword(s):  
Thrombus Formation ◽  
Factor Xa ◽  
Arterial Injury ◽  
Inhibitory Effect ◽  
Endothelial Damage ◽  
Stent Deployment ◽  
Risk Of Death ◽  
Fxa Inhibitor ◽  
Prothrombinase Activity

Abstract PCI patients routinely experience arterial injury during balloon angioplasty and stent deployment. At the injured arterial site, endothelial damage triggers platelet adhesion to the vascular wall and initiates platelet-associated prothrombinase complex (factor Xa [FXa]-factor Va-phospholipids-calcium) formation, resulting in the progression of thrombus formation. Recently, it was demonstrated that treatment with fondaparinux reduced the risk of death or recurrent myocardial infarction without an increase in the incidence of major bleeding compared to standard therapy in patients with STEMI. However, fondaparinux showed no superiority to placebo or heparin in patients undergoing PCI. On the other hand, small molecule direct FXa inhibitors, which are still in early stages of clinical development for the prevention of ACS, have been reported to strongly block reconstituted prothrombinase. Here, we compared the effects of TAK-442, a novel direct FXa inhibitor on platelet-associated prothrombinase activity, with fondaparinux. TAK- 442 and fondaparinux inhibited endogenous FXa activity in platelet-poor plasma from humans (IC50: 53 nM, TAK-442; 11 nM, fondaparinux) and rats (IC50: 32 nM, TAK-442; 19 nM, fondaparinux). When TAK-442 or fondaparinux were preincubated with free FXa, they each inhibited in vitro reconstituted prothrombinase activity, with IC50 values of 28 nM and 3.9 nM, respectively. In the absence of free FXa preincubation, TAK-442 retained this inhibitory effect (IC50, 51 nM); the inhibitory effect of fondaparinux, however, decreased dramatically (IC50, 1700 nM). In a rat model of balloon injury, thrombin activity on the surface of injured vessels increased to 3.3-, 20- and 5.7-fold that of intact aorta at 5 min, 1 hr, and 24 hrs after the injury, respectively. At 1 hr after the injury, 300 nM TAK-442 significantly (p<0.025) inhibited platelet-associated thrombin generation on the surface of injured aorta by 99% (IC50, 19 nM), whereas the same concentration of fondaparinux showed no significant (p=0.076) inhibition (IC50, >300 nM). These results highlight a limitation of fondaparinux in inhibiting platelet-associated prothombinase activity that leads to thrombus formation compared with TAK-442, and suggest that TAK-442 may be more effective in preventing arterial thrombosis in patients undergoing percutaneous coronary interventions.

Differential Effects of TAK-442, a Factor Xa Inhibitor, and Ximelagatran, a Thrombin Inhibitor, on Bleeding: Possible Role of Differences in Effects on Factor V-Mediated Feedback on Blood Coagulation Cascade

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 5460-5460
Author(s):  
Noriko Konishi ◽  
Katsuhiko Hiroe ◽  
Yasuhiro Imaeda ◽  
Takuya Fujimoto ◽  
Keiji Kubo ◽  
...  
Keyword(s):  
Venous Thrombosis ◽  
Rat Model ◽  
Positive Feedback ◽  
Thrombin Generation ◽  
Thrombus Formation ◽  
Factor Xa ◽  
Coagulation Cascade ◽  
Factor V ◽  
Differential Effects

Abstract Thrombin generation serves to amplify the coagulation cascade via positive feedback activation of factor V (FV) and factor VIII. We hypothesized that factor Xa (FXa) inhibitors, unlike thrombin inhibitors, would not block the feedback activation of the coagulation cascade but would have a favorable anticoagulating profile—sufficient to prevent thrombus formation, yet not interfere with hemostatic plug formation. TAK-442 is a newly synthesized, selective FXa inhibitor that strongly inhibits FXa (with a Ki value of 1.8 nM), and displays more than 440x selectivity toward FXa than other serine proteases. In the present study, we compared the effects of TAK-442 versus ximelagatran on FV-mediated positive feedback in vitro, and on their antithrombotic and hemorrhagic effects in a rat model of venous thrombosis. In vitro, TAK-442 gradually inhibited thrombin generation and prolonged prothrombin time (PT) in a dose-dependent manner, while melagatran, an active form of ximelagatran, exhibited a steeper effect at higher doses tested. The PT prolonging potency was increased in FV–deficient human plasma, with CT2 values (the concentration that causes 2 times prolongation of clotting times) of 120 nM for TAK-442 and 32 nM for melagatran, compared with 500 nM and 360 nM for TAK-442 and melagatran, respectively in normal plasma. In the rat model of venous thrombosis, TAK-442 (10 mg/kg, po) prevented thrombus formation by 55% and prolonged PT by 1.3 times of control values; a similar effect was observed in ximelagatran-treated (3 mg/kg, po) animals, with 59% inhibition of thrombus formation and 1.2 times prolongation of PT. TAK-442 at 100 mg/kg, prolonged PT by 2.1 times, with no significant change in bleeding time (BT); in contrast, increasing the dose of ximelagatran to 10 mg/kg, po prolonged PT by 3.9 times and significantly (P<0.025) increased BT. Our data suggest that the differential effects of the two agents on FV-mediated amplification of thrombin generation may underlie the observation of a wider therapeutic window for TAK-442 than for ximelagatran.

The Effect of the Synthetic Pentasaccharide SR 90107/ORG 31540 on Thrombin Generation Ex Vivo Is Uniquely due to ATIII-Mediated Neutralization of Factor Xa

1995 ◽  
Vol 74 (06) ◽  
pp. 1474-1477 ◽  
Author(s):  
J C Lormeau ◽  
J P Herault
Keyword(s):  
Thrombin Generation ◽  
Graphical Representation ◽  
Ex Vivo ◽  
Subcutaneous Administration ◽  
Factor Xa ◽  
Significant Rise ◽  
Time Courses ◽  
The One

SummaryThe inhibition of thrombin generation (TG) was studied in plasma from human volunteers after single subcutaneous administrations of 4000, 8000 or 12,000 anti-Xa units (i.e., 6, 12 or 18 mg) of the synthetic pentasaccharide (SR 90107/ORG 31540) (SP).SP impaired TG in plasma for up to 18 h after injection, and the time-courses of TG and factor Xa inhibitions were similar.In untreated plasma supplemented in vitro with SP to obtain the same anti-Xa activity as in ex vivo samples, equivalent TG inhibitions were observed thus showing that no transformed SP molecules were involved in the TG inhibition ex vivo.Functional as well as immunological assay of TFPI indicated that subcutaneous injection of 12,000 anti-Xa units of SP did not induce any TFPI release, whereas under the same conditions, 13,000 IU of Fraxiparine® produced a significant rise of TFPI in plasma.The plotting of TG inhibition versus SP concentration could be fitted with a good correlation (r = 0,94) to the graphical representation linking [ATIII-SP] to [SP].These results demonstrate that following subcutaneous administration to man, SP inhibits TG ex vivo and likely in vivo exclusively through the same selective ATIII-mediated inhibition of factor Xa as the one elicited in vitro.

Ex Vivo Effects of Acetylsalicylic Acid, Sulfinpyrazone and Dipyridamole on Platelet Adhesion and Thrombus Formation in Flowing Native and Anticoagulated Blood

1979 ◽  
Author(s):  
H. R. Baumgartner
Keyword(s):  
Acetylsalicylic Acid ◽  
Platelet Adhesion ◽  
Ex Vivo ◽  
Thrombus Formation ◽  
Drug Effects ◽  
Inhibitory Effect ◽  
Blood Collection ◽  
Citrate Anticoagulation ◽  
Drug Actions

Potential platelet inhibitors are usually tested ex vivo by investigating platelet function in vitro after drug ingestion and subsequent blood collection into citrate. The purpose of the present study was to determine whether and how citrate anticoagulation interferes with possible drug actions in rabbits. Platelet adhesion and thrombus formation on subendothelium were compared after perfusion at 1300 sec-1 wall shear rate of native blood and of blood anticoagulated with citrate, heparin or heparin plus citrate. Results. 15 mM citrate in plasma caused significant reduction of aggregation, thrombus volume and thrombus height; adhesion was concomitantly increased. Heparin (500 U/kg) had no effect on adhesion and thrombus dimensions. Treatment of rabbits with acetylsalicylic acid or sulfinpyrazone (2x100 µmol/kg) caused a significant reduction of thrombus volume and thrombus height in the presence of citrate. However, no drug effects were observed after perfusion of native or heparinized blood of the same rabbits. Equimolar doses of dipyridamole were always without effect. Conclusion. Low citrate concentrations (1) inhibit thrombus growth, (2) enhance thrombus breakdown,(3) secondarily increase adhesion and (4) strongly enhance a possible inhibitory effect of acetylsalicylic acid and sulfinpyrazone on thrombus growth and/or breakdown.

The Direct Factor Xa Inhibitor Apixaban Produces Broad Antithrombotic Activity with Limited Effects on Bleeding Time in Rats.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 4005-4005
Author(s):  
William A. Schumacher ◽  
Jeffrey S. Bostwick ◽  
Anne B. Stewart ◽  
Thomas E. Steinbacher ◽  
Donald J. Pinto ◽  
...  
Keyword(s):  
Bleeding Time ◽  
Ex Vivo ◽  
Thrombus Formation ◽  
Plasma Concentrations ◽  
Vena Cava ◽  
Factor Xa ◽  
Experimental Models ◽  
Factor Xa Inhibitor ◽  
Dependent Manner ◽  
Venous Shunt

Abstract Apixaban is an oral, direct and highly selective factor Xa inhibitor which is in late stage clinical development for the prevention and treatment of thromboembolic diseases. Apixaban is potent against human and rat factor Xa (Ki = 0.08 and 1.3 nM, respectively). The efficacy/safety profile of apixaban was determined in experimental models of thrombosis and hemostasis performed in anesthetized rats. Thrombosis was induced either by topical application of FeCl2 to the vena cava (VT) or carotid artery (AT), tissue factor infusion into the vena cava (TF-VT), or within an extracorporeal arterial-venous shunt (ST). Bleeding time was measured in response to template incision of the renal cortex. Apixaban was administered as a continuous i.v. infusion of 0.1, 0.3, 1 or 3 mg/kg/h starting 60 min before each experimental procedure (n=5 or 6 per dose). These respective doses increased the ex vivo prothrombin time by 1.3, 1.9, 3.0 and 3.9 times control baseline, and achieved plasma concentrations of 0.3, 1.4, 5.0 and 12.2 μM. In comparison to vehicle treatment, the 3 mg/kg/h dose of apixaban decreased thrombus weight by 90 ± 2% in VT, 62 ± 7% in TF-VT, 62 ± 4% in AT, and 79 ± 3% in ST (all p<0.05). A 50% thrombus weight reduction sufficient to prevent vascular occlusion in each model would require projected doses (mg/kg/h) of 0.4 (VT), 1.9 (TF-VT), 0.8 (AT) and 1.1 (ST). The lowest dose level which preserved carotid blood flow at the pre-injury level during thrombus formation was 0.3 mg/kg/h. Apixaban prolonged bleeding time in a dose-dependent manner with no effect detected at 0.1 and 0.3 mg/kg/h, while significant (p<0.05) increases of 1.34 ± 0.12 and 2.13 ± 0.17 times control were observed at 1 and 3 mg/kg/h, respectively. In comparison, aspirin increased bleeding time by 1.42 ± 0.1 times control (n=7, p<0.05) when tested at a 10 mg/kg dose, a dose which produced maximum cyclooxygenase inhibition. These studies predict a wide therapeutic index for apixaban based on the prevention of occlusive thrombosis in a variety of experimental models without excessive bleeding time prolongation. These results are consistent with the safety and efficacy observed with apixaban in phase II clinical trials.

Sign in / Sign up

Export Citation Format

Share Document