Antithrombotic properties of SSR182289A, a new, orally active thrombin inhibitor.

N-[3-[[[(1S)-4-(5-Amino-2-pyridinyl)-1-[[4-difluoromethylene)-1-piperidinyl]carbonyl]butyl]amino]sulfonyl][1,1'-biphenyl]-2-yl]acetamide hydrochloride (SSR182289A) is a novel, potent, and selective thrombin inhibitor. We have examined the antithrombotic properties of SSR182289A administered by i.v. and p.o. routes in several different animal thrombosis models in comparison with reference antithrombotic agents. Oral administration of SSR182289A produced dose-related antithrombotic effects in the following models; rat venous thrombosis (ED(50) 0.9 mg/kg p.o.), rat silk thread arterio-venous (AV) shunt (ED(50) 3.8 mg/kg p.o.), rat thromboplastin-induced AV shunt (ED(50) 3.1 mg/kg p.o.), rat carotid artery thrombosis (ED(200) 5.9 mg/kg p.o.), and rabbit venous thrombosis (ED(50) 7.5 mg/kg p.o.). Administered as an i.v. bolus, SSR182289A showed antithrombotic activity in the above models with ED(50)/ED(200) values in the range of 0.2 to 1.9 mg/kg i.v. SSR182289A increased rat tail transection bleeding time at doses > or =10 mg/kg p.o. In the rat thromboplastin-induced AV shunt model, SSR182289A 10 mg/kg p.o. produced marked antithrombotic effects at 30, 60, 120, and 240 min after administration. Hence, SSR182289A demonstrates potent oral antithrombotic properties in animal venous, AV-shunt, and arterial thrombosis models.

Antiplatelet and antithrombotic activity of SL65.0472, a mixed 5-HT1B/5-HT2A receptor antagonist.

The antiplatelet and antithrombotic activity of SL65.0472 (7-fluoro-2-oxo-4-[2-[4-(thieno [3,2-c]pyrin-4-yl) piperazin-1-yl]ethyl]-1,2-di-hydroquinoline-acetamide), a mixed 5-HT1B/5-HT2A receptor antagonist was investigated on 5HT-induced human platelet activation in vitro, and in rat, rabbit and canine platelet dependent thrombosis models. SL65.0472 inhibited 5-HT-induced platelet shape change in the presence of EDTA (IC50 values = 35, 69 and 225 nM in rabbit, rat and human platelet rich plasma (PRP)), and also inhibited aggregation induced in human PRP by 3-5 microM 5-HT + threshold concentrations of ADP (0.5-1 microM) or collagen (0.3 microg/ml) with mean IC50 values of 49 +/- 13 and 48 +/- 6 nM respectively. SL65.0472 inhibited thrombus formation when given both intravenously 5 min and orally 2 h prior to assembly of an arterio-venous (A-V) shunt in rats as from 0.1 and 0.3 mg/kg respectively. It was active in a rabbit A-V shunt model with significant decreases in thrombus weight as from 0.1 mg/kg i. v. and at 10 mg/kg p.o. The delay to occlusion in an electric current-induced rabbit femoral artery thrombosis model was increased by 251% (p <0.05) after 20 mg/kg p.o. SL65.0472 (30 microg/kg i.v.) virtually abolished coronary cyclic flow variations (7.2 +/- 1.0/h to 0.6 +/- 0.6/h, p <0.05) and increased minimum coronary blood flow (1.2 +/- 0.8 ml/min to 31.8 +/- 8.4 ml/min, p <0.05) in a coronary artery thrombosis model in the anaesthetised dog. Finally, SL65.0472 significantly increased the amount of blood lost after rat tail transection at 3 mg/kg p.o. Thus the anti-5-HT2A component of SL65.0472 is reflected by its ability to inhibit 5-HT-induced platelet activation, and platelet-rich thrombus formation.

Antithrombotic activity of a monoclonal antibody inducing the substrate form of plasminogen activator inhibitor type 1 in rat models of venous and arterial thrombosis.

1. Elevated plasminogen activator inhibitor 1 (PAI-1) is a risk factor for thrombosis, and inhibitors of the interaction between PAI-1 and tissue plasminogen activator (t-PA) have antithrombotic and prothrombolytic activity in animals. We describe the antithrombotic effects in the rat of a monoclonal antibody (MA33H1) which converts PAI-1 to a non-inhibitory substrate. 2. The activity of MA33H1 against rat PAI-1 was confirmed using two-chain t-PA and a chromogenic substrate. MA33H1 was evaluated in rat venous (thromboplastin + stasis in the abdominal vena cava) and arterial (electric current applied to a carotid artery) thrombosis models. The effects on tail-transection bleeding time were studied. 3. MA33H1 at 100 ng ml(-1) inhibited both human (44.1%) and rat PAI-1 (49.7%). This effect was concentration-dependent. Its effect on human PAI-1 was not significantly inhibited by 1 microg ml(-1) fibrin or a approximately 7 fold molar excess of vitronectin (1 nM). Inhibition of rat PAI-1 was unchanged by fibrin, but vitronectin reduced inhibition from 0.5 nM. 4. In the venous thrombosis model, MA33H1 significantly reduced thrombus weights by 38 and 58.6% at 50 and 100 microg kg(-1) min(-1) i.v. respectively. This effect was inhibited by tranexamic acid. In the arterial model, MA33H1 significantly increased the delay to occlusive thrombus formation by 58 and 142% at 50 and 100 microg kg(-1) min(-1) i.v., and did not affect bleeding time at 300 microg kg(-1) min(-1) i.v. 5. Thus, a monoclonal antibody which transforms PAI-1 to a t-PA substrate prevents thrombus formation in the rat with no effect on bleeding time at a higher dose.

Ecarin Clotting Time: a predictive coagulation assay for the antithrombotic activity of argatroban in the rat.

We studied the use of the Ecarin Clotting Time (ECT) as a predictive assay of the antithrombotic effects of argatroban in a new tissue factor-dependent model of venous thrombosis and a model of arterial thrombosis in the rat. Heparin was used as a reference anticoagulant. Infusions of argatroban dose-dependently increased the ECT across the range of doses required for antithrombotic activity in models of venous and arterial thrombosis (1.25-40 microg/kg/min). The TT was only useful as a marker in the case of venous thrombosis, since, in the arterial thrombosis model, the clotting times were >200 s in the majority of animals receiving antithrombotic doses. The aPTT is not sufficiently sensitive to be predictive of an antithrombotic effect in the venous model, and shows only modest increases in the arterial thrombosis model. Heparin did not significantly increase the ECT at antithrombotic doses in the venous thrombosis model, and only increased the ECT by 53% at 40 microg/kg/min in the arterial model, despite a marked antithrombotic effect. Both the TT and aPTT were dose-dependently increased by heparin at doses active in the venous model, whereas both parameters were >200 s at doses active in the arterial thrombosis model. Thus, the ECT provides a predictive marker for the antithrombotic activity of argatroban in both venous and arterial thrombosis, at least in the rat.