An Analog Of Thiazole Which Has Potential Antithrombotic Activity With Low Toxicity

Chemical modification of a compound found active in preventing death in mice following intravenous administration of collagen led to the development of an inhibitor of collagen-induced platelet aggregation which was active at 1 ng/ml in human PRP, namely 4,5-bis(p-methoxyphenyl)-2- (trifluoromethyl)-thiazole (TFT). It did not inhibit ADP, thrombin or PGH2-induced aggregation but inhibited the collagen-induced release of radioactivity from platelets labelled with radioactive serotonin. It was active in many animal species and in the rabbit it had a duration of activity of about 8 hours at 1 mg/kg (p.o.).TFT has cyclooxygenase inhibitory activity, but unlike aspirin (A) or flurbiprofen (F), it showed no incidence of ulcers at 500 mg/kg p.o. in rats. However, again unlike A or F, it had very little anti-inflammatory activity as measured by the carrageenan-induced hind paw edema assay in rats. Its LD50 in mice (i.p.) was greater than 1 gm/kg.Thus TFT appears to be a potential antithrombotic agent with high antiplatelet specificity and a wide therapeutic margin as compared with A or F. The anti platelet action of TFT may be due to its inhibition of cyclooxygenase.

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A Thiazole Compound with Potential Antithrombotic Activity

Thrombosis and Haemostasis ◽

10.1055/s-0038-1657156 ◽

1982 ◽

Vol 47 (02) ◽

pp. 173-176 ◽

Cited By ~ 14

Author(s):

E E Nishizawa ◽

A R Mendoza ◽

T Honohan ◽

K A Annis

Keyword(s):

Platelet Aggregation ◽

Potent Inhibitor ◽

Platelet Rich Plasma ◽

Development Program ◽

Antithrombotic Agent ◽

Antithrombotic Activity ◽

Thiazole Derivative ◽

Cyclooxygenase Activity ◽

Drug Development Program

SummaryA thiazole derivative, 4,5-bis(p-methoxyphenyl)-2-(trifluoromethyl)-thiazole was found to be a potent inhibitor of collagen-induced platelet aggregation, in vitro, using platelets from at least six species, including man. It was active in human platelet-rich plasma at a concentration of 1 ng/ml. While its antiplatelet activity was greater than that of flurbiprofen, its cyclooxygenase activity was equivalent to that of flurbiprofen. Also, compared to flurbiprofen, the thiazole had less anti-inflammatory activity in the hind-paw edema test. The thiazole derivative inhibited platelet aggregation following oral administration in five laboratory species. In the guinea pig it was active at 0.5 mg/kg. The LD50 in mice was greater than 1000 mg/kg (i.p.). This compound, which was designed through a systematic drug development program, may have high potential as an antithrombotic agent.

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Antithrombotic Activity of a Potent, New Agent, 6,7-Dichloro-1,2,3,5-Tetrahydroimidazo[2,1-B] Quinazolin-2-One Hydrochloride Monohydrate

10.1055/s-0039-1680489 ◽

1977 ◽

Author(s):

J. S. Fleming ◽

J. P. Buyniski

Keyword(s):

Platelet Aggregation ◽

Animal Models ◽

Ex Vivo ◽

Platelet Rich Plasma ◽

Oral Dosage ◽

Antithrombotic Agent ◽

Duration Of Action ◽

Antithrombotic Activity ◽

Small Vessels ◽

Hydrochloride Monohydrate

A potent, new anti-thrombotic agent, 6 ,7-dichloro-l,2,3,5-tetrahydroimidazo[2,1-b]quinazolin-2-one hydrochloride monohydrate (BL-4162A) has been evaluated for activity against induced platelet aggregation in a series of in vitro and ex vivo experiments using platelet rich plasma (PRP) from various species including man. In addition, the compound’s potential utility as an antithrombotic agent has been tested in various in vivo animal models including two models of induced thrombosis involving both large and small vessels. Aggregometry was employed to test the ability of BL-4162A to inhibit platelet aggregation induced by aggregating agents such as ADP, collagen, thrombin and antigen-antibody complexes. The compound’s antithrombotic activity was evaluated in small vessels using the biolaser-rabbit ear chamber technique while the effect of BL-4162A on large vessel thrombosis was assessed against electrically-induced carotid artery thrombosis in dogs. Results indicate that BL-4162A inhibits platelet aggregation in the range of 0.08 to 0.68 pg/ml. Platelet antiaggregating activity was also observed in ex vivo aggregometry studies in dogs and rats at oral doses in the range of 1 to 10 mg/kg. Of particular interest, is the fact that BL-4162A effectively inhibited thrombosis in both animal models employed over the same oral dosage range. Results of the above investigations as well as an appreciable duration of action suggest that BL-4162A may be an important candidate for clinical evaluation in thromboembolism.

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The Interaction Of Platelet Active Drugs With Prostacyclin In Vitro And Against Biolaser Induced Intravascular Thrombosis

10.1055/s-0038-1652780 ◽

1981 ◽

Author(s):

J S Fleming ◽

B T Cornish ◽

J O Buchanan ◽

J P Buyniski

Keyword(s):

Platelet Aggregation ◽

Arachidonic Acid Metabolism ◽

In Vivo Model ◽

Additive Interaction ◽

Antithrombotic Activity ◽

Intravascular Thrombosis ◽

Low Levels ◽

Induced Aggregation

Prostacyclin and thromboxane A2, two of the physiologically most important end products of arachidonic acid metabolism, represent a basic control system which modulates platelet function. Decreased vascular prostacyclin is believed to play a role in the increased thrombotic tendency associated with various clinical diseases including diabetes and atherosclerosis. Compounds which either enhance the formation or release of prostacyclin or potentiate the activity of low levels of prostacyclin may be therapeutically useful in ameliorating this associated pathology. We have studied various inhibitors of platelet aggregation for their ability to potentiate the activity of low levels of prostacyclin both in vitro and in an in vivo model of experimental thrombosis. Anagrelide, aspirin, dipyridamole, sulfinpyrazone and ticlopidine all demonstrated interaction with prostacyclin in vitro against collagen-induced platelet aggregation. More limited interactions were observed against ADP-induced aggregation. Using isobolographic analysis most combinations demonstrated additive interaction. However, pronounced supra-additive interaction was observed vs. both aggregating agents in the case of prostacyclin (0.1-1 ng/ml) - anagrelide (8-90 ng/ml) combinations. Dramatic enhancement of the effects of prostacyclin on biolaser-induced thrombosis was also seen in anagrelide (0.5 mg/kg po) pretreated animals. Other inhibitors of platelet aggregation used in combination with prostacyclin produced less spectacular results. These findings suggest that aside from inherent antiaggregatory and antithrombotic activity, certain platelet active drugs may produce equally important effects by virtue of their ability to interact with prostacyclin in a clinically beneficial manner.

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EFFECT OF COLLAGEN AND CITRATE ON HEPARIN-HEDIATED PLATELET ANTIAGGREGATORY ACTIVITY

10.1055/s-0038-1642869 ◽

1987 ◽

Author(s):

S R Saba ◽

H I Saba ◽

G A Morelli

Keyword(s):

Platelet Aggregation ◽

Inhibitory Activity ◽

Whole Blood ◽

Sodium Citrate ◽

Blood Platelet ◽

Inhibit Platelet Aggregation ◽

Agonist Activity ◽

Antiaggregatory Activity ◽

Induced Aggregation ◽

Blood Platelet Aggregation

Heparin has been reported to inhibit platelet aggregation. Our studies show that this activity is easily demonstrable in washed platelet systems, but fails to occur in citrated platelet-rich plasma (PRP) in the presence of a variety of agonists, except collagen. Studies were performed to answer the following questions: (1) Why does heparin inhibit the aggregation of washed platelets but not of citrated PRP, which is the system commonly used for platelet aggregation studies? (2) What is the effect of heparin on platelet aggregation occurring in whole blood, where it can be examined both with and without the presence of sodium citrate? (3) Why does heparin consistently inhibit the collagen-induced aggregation even in citrated PRP, while it fails to inhibit aggregation caused by other agonists? Results of the studies clearly demonstrated that heparin has the ability to directly react with sodium citrate, causing loss of its inhibitory activity on platelets. The antiaggregatory activity of heparin in the presence of collagen as the agonists appears to be directly related to the blocking of collagen’s agonist activity by heparin. Small concentrations of heparin which were unable to inhibit aggregation per se, effectively blocked the collagen agonist activity on platelet aggregation when heparin was directly added to collagen. Further studies showed that heparin, in a native whole blood platelet aggregation system (in the absence of any anticoagulant), exhibited significant inhibitory activity. This activity was lost when citrate was present in the whole blood preparation. These studies, therefore, indicate that failure of heparin to inhibit platelet aggregation in citrated PRP does not negate the importance of this inhibitory activity. Reactivity of heparin with sodium citrate renders citrated systems unsuitable for studying heparin's effect upon platelets. The whole blood platelet aggregation system without the presence of anticoagulants appears to be a more suitable system for the study of heparin and platelet aggregation, and is closer to the physiological system. Heparin exhibits marked inhibitory activity on platelet aggregation in this system, and this suggests it may be an important activity which deserves further attention.

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Synthesis, platelet aggregation inhibitory activity, and in vivo antithrombotic activity of new 1,4-dihydropyridines

Journal of Medicinal Chemistry ◽

10.1021/jm00118a004 ◽

1988 ◽

Vol 31 (10) ◽

pp. 1886-1890 ◽

Cited By ~ 37

Author(s):

Carlos E. Sunkel ◽

Miguel Fau de Casa-Juana ◽

Francisco Javier Cillero ◽

Jaime G. Priego ◽

M. Pilar Ortega

Keyword(s):

Platelet Aggregation ◽

Inhibitory Activity ◽

Antithrombotic Activity

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Unexpected Effects of Aurin Tricarboxylic Acid on Human Platelets

Thrombosis and Haemostasis ◽

10.1055/s-0038-1656347 ◽

1992 ◽

Vol 68 (02) ◽

pp. 189-193 ◽

Cited By ~ 9

Author(s):

Raelene L Kinlough-Rathbone ◽

Marian A Packham

Keyword(s):

Platelet Aggregation ◽

Sodium Salt ◽

Platelet Activating Factor ◽

Calcium Ionophore ◽

Tricarboxylic Acid ◽

Calcium Ionophore A23187 ◽

Ionophore A23187 ◽

Antithrombotic Agent ◽

Platelet Suspension ◽

Induced Aggregation

SummaryAurin tricarboxylic acid (ATA) is a potent inhibitor of ristocetin-mediated platelet agglutination and of shear-induced, von Willebrand factor (vWf)-mediated platelet aggregation, probably via inhibition of vWf interaction with glycoprotein Ib (GPIb). We examined the effects of ATA (both the sodium salt and a solution of ATA in ethanol) on platelet functions in citrated plasma (PRP) and in suspensions of washed platelets in Tyrode-albumin solution (contains 2 mM Ca2+). ATA (42–211 µg/ml) blocked aggregation and release of granule contents induced by thrombin (0.15 U/ml in PRP; 0.03 U/ml in platelet suspension). Responses to higher concentrations of thrombin were not inhibited. ATA also prolonged thrombin-induced clotting of fibrinogen. Since ATA had no effect on fibrinogen-induced responses of chymotrypsin-treated platelets, ATA probably acts on thrombin rather than on fibrinogen.In PRP and platelet suspensions, ATA (acid form 106 µg/ml; sodium salt 122 µg/ml) had little effect on ADP-induced platelet aggregation. The sodium salt of ATA (61–122 µg/ml) enhanced collagen-induced aggregation and release by platelets in citrated plasma and by washed platelets; the enhancement was extensively inhibited by aspirin. With platelet suspensions, ATA significantly enhanced aggregation and release caused by low concentrations of sodium arachidonate (15–50 µM); aggregation and release caused by higher concentrations of arachidonate were somewhat inhibited by ATA. Arachidonate-induced aggregation and release were also enhanced by ATA in PRP. ATA enhanced aggregation and release induced by the calcium ionophore A23187; aspirin had little effect on the enhancement. ATA also enhanced aggregation and release caused by the thromboxane A2 mimetic, U46619 (0.1–.4 µM) or platelet-activating factor (PAF) (5 ng/ ml), but enhancement was never as extensive as when these platelet responses were caused by arachidonate or A23187; aspirin partially inhibited these enhancements. Thus, although ATA may interfere with the interaction of GPIb with large vWf multimers and inhibit the activity of thrombin, thereby having antithrombotic properties, it has potentiating effects on some other agonists; these effects should be considered if it is used as an antithrombotic agent.

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Inhibition of Human Platelet Aggregation by Plasmin Digests of Human and Bovine Fibrinogen Preparations: Role of Contaminating Factor VIII-related Material

Blood ◽

10.1182/blood.v44.2.169.169 ◽

1974 ◽

Vol 44 (2) ◽

pp. 169-175 ◽

Cited By ~ 10

Author(s):

D. E. Culasso ◽

M. B. Donati ◽

G. de Gaetano ◽

J. Vermylen ◽

M. Verstraete

Keyword(s):

Platelet Aggregation ◽

Factor Viii ◽

Inhibitory Activity ◽

Gel Chromatography ◽

Human Fibrinogen ◽

Related Material ◽

Large Molecular Weight ◽

Material Factor ◽

Induced Aggregation

Abstract Preparations of human fibrinogen, digested by plasmin, inhibited ADP-induced platelet aggregation; the inhibitory activity was confined to the small dialyzable fragments accumulating during the degradation. Purified large molecular weight fragments D and E had no effect on ADP-induced aggregation, but fragment E inhibited thrombin-induced aggregation. Extensively degraded bovine fibrinogen preparations also inhibited platelet aggregation by ADP. Both human and bovine fibrinogen preparations were contaminated with factor VIII-related material (factor VIII-related antigen and factor VIII procoagulant activity, respectively); separation of factor VIII-related material from human or bovine fibrinogen by gel chromatography and subsequent plasmin digestion of the fractions revealed that the inhibitory activity was mainly linked to digested factor VIII-related material. This inhibitory activity was dialyzable. The effect of fibrinogen digests on platelet aggregation should therefore be reconsidered.

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ChemInform Abstract: Synthesis, Platelet Aggregation Inhibitory Activity, and in vivo Antithrombotic Activity of New 1,4-Dihydropyridines.

ChemInform ◽

10.1002/chin.198910214 ◽

1989 ◽

Vol 20 (10) ◽

Author(s):

C. E. SUNKEL ◽

M. FAU DE CASA-JUANA ◽

F. J. CILLERO ◽

J. G. PRIEGO ◽

M. P. ORTEGA

Keyword(s):

Platelet Aggregation ◽

Inhibitory Activity ◽

Antithrombotic Activity

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In Vivo Activity of Tieclopidine, a New Drug with Platelet Aggregation Inhibiting, Antisludge and Antithrombotic Properties

10.1055/s-0039-1689157 ◽

1975 ◽

Author(s):

J. C. Ferrand ◽

D. Aubert ◽

B. Lacaze ◽

O. Pepin ◽

J. J. Thebault

Keyword(s):

Platelet Aggregation ◽

Blood Stasis ◽

Blood Platelet ◽

Inhibitory Effect ◽

Clinical Approach ◽

Synthetic Compounds ◽

Antithrombotic Activity ◽

Daily Dose ◽

Induced Aggregation

Tieclopidine (53–32 C) belongs to a new series of synthetic compounds which have proved to inhibit significantly blood platelet aggregation in animals. Administered orally to rats, it reduces markedly the plate let aggregation induced by ADP and collagen. The activity appears 2 to 6 hours after a single dose and persists for 24 hours.The sludge and blood stasis induced in rats by protamin sulfate injections disappear completely in five minutes after an intravenous administration of Thieclopidine. Animals pretreated orally with this compound failed to show any sludge formation.The antithrombotic activity of Tieclopidine was demonstrated in rats carrying a dental broach implanted in the abdominal aorta. White thrombideveloped locally in the control animals, but were absent or much less severe in pretreated animals.In man the first clinical approach has shown that at a daily dose of 1 g the inhibitory effect of Tieclopidine on ADP induced aggregation requires 24 to 48 hrs to become significant and reaches a plateau after 5 or 6 days of treatment.

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Demonstration of antithrombotic activity of glomerular adenosine diphosphatase [published erratum appears in Blood 1991 Oct 15;78(8):2163]

Blood ◽

10.1182/blood.v78.1.141.bloodjournal781141 ◽

1991 ◽

Vol 78 (1) ◽

pp. 141-148 ◽

Cited By ~ 1

Author(s):

K Poelstra ◽

JF Baller ◽

MJ Hardonk ◽

WW Bakker

Keyword(s):

Platelet Aggregation ◽

Ex Vivo ◽

Rat Kidney ◽

Selective Reduction ◽

Uridine Diphosphate ◽

Antithrombotic Activity ◽

Perfusion Model ◽

Induced Aggregation ◽

Thrombotic Tendency

We have demonstrated that reduced glomerular adenosine diphosphatase (ADPase) activity within the rat kidney is associated with an increased thrombotic tendency. To establish a possible causal relationship between these intraglomerular events, experiments were conducted to inhibit adenosine diphosphate (ADP) degradation without influencing other glomerular prothrombotic or antithrombotic mechanisms. Concurrently, we studied intraglomerular platelet aggregation. Two ways of selective inhibition of glomerular ADPase activity were applied: (1) by competitive substrates (ie, uridine diphosphate [UDP]), and (2) by the nondegradable ADP analogue ADP-beta-S. Both strategies were used during ex vivo alternate perfusion of kidneys with platelets and ADP (to test intraglomerular thrombotic tendency). Each group (n = 6) received different substrates or a combination of substrates. A significant increase in platelet aggregation was observed in kidneys after perfusion with platelets and ADP together with the competitive substrate UDP as compared to perfusions with platelets and ADP alone (78.5% +/- 9.8% v 27.9% +/- 11.4% glomeruli staining positive for platelets, P less than .005). In contrast, UDP alone had no effect on platelet aggregation. Other nucleoside polyphosphates (guanosine diphosphate and inosine triphosphate) were also effective as competitive substrates in the ex vivo perfusion model (n = 4). None of these substrates was capable of increasing ADP-induced aggregation when studied in vitro. In addition, ADP- beta-S also increased platelet aggregation in the perfusion model as compared with native ADP (P less than .005). These results show that selective reduction of ADP degradation in intact kidneys strongly promotes the intraglomerular proaggregatory condition. It can be concluded that glomerular ADPase exerts potent antithrombotic activity within the normal rat kidney.

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