Novel P2Y12 adenosine diphosphate receptor antagonists for inhibition of platelet aggregation (II): Pharmacodynamic and pharmacokinetic characterization

Summary“Early” fibrinogen degradation products are more potent inhibitors of thrombin-induced clotting than “late” products and also interfere with the ability of thrombin to release serotonin from platelets. “Early” and “intermediate” FDP cause moderate inhibition of platelet aggregation induced by adenosine diphosphate or connective tissue particles. Serotonin release by connective tissue particles is probably not inhibited by FDP.

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Mode of action of P2Y12 antagonists as inhibitors of platelet function

Thrombosis and Haemostasis ◽

10.1160/th10-07-0482 ◽

2011 ◽

Vol 105 (01) ◽

pp. 96-106 ◽

Cited By ~ 21

Author(s):

Jackie Glenn ◽

Ann White ◽

Sue Fox ◽

Hans van Giezen ◽

Sven Nylander ◽

...

Keyword(s):

Platelet Aggregation ◽

G Protein ◽

Platelet Function ◽

Adenosine Diphosphate ◽

P2y12 Receptor ◽

Receptor Antagonists ◽

Receptor Agonists ◽

P2y12 Antagonists ◽

Induced Aggregation ◽

G Protein Coupled

SummaryP2Y12 receptor antagonists are antithrombotic agents that inhibit platelet function by blocking the effects of adenosine diphosphate (ADP) at P2Y12 receptors. However, some P2Y12 receptor antagonists may affect platelet function through additional mechanisms. It was the objective of this study to investigate the possibility that P2Y12 antagonists inhibit platelet function through interaction with G-protein-coupled receptors other than P2Y12 receptors. We compared the effects of cangrelor, ticagrelor and the prasugrel active metabolite on platelet aggregation and on phosphorylation of vasodilator-stimulated phosphoprotein (VASP). We compared their effects with those of selective IP, EP4 and A2A agonists, which act at Gs-coupled receptors. All three P2Y12 antagonists were strong inhibitors of ADP-induced platelet aggregation but only partial inhibitors of aggregation induced by thrombin receptor activating peptide (TRAP) or the thromboxane A2 mimetic U46619. Further, after removing ADP and its metabolites using apyrase and adenosine deaminase, the P2Y12 antagonists produced only minor additional inhibition of TRAP or U46619-induced aggregation. Conversely, the Gs-coupled receptor agonists always produced strong inhibition of aggregation irrespective of whether ADP was removed. Other experiments using selective receptor agonists and antagonists provided no evidence of any of the P2Y12 antagonists acting through PAR1, TP, IP, EP4, A2A or EP3 receptors. All three P2Y12 antagonists enhanced VASPphosphorylation to a small and equal extent but the effects were much smaller than those of the IP, EP4 and A2A agonists. The effects of cangrelor, ticagrelor and prasugrel on platelet function are mediated mainly through P2Y12 receptors and not through another G-protein-coupled receptor.

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Platelet Glycoprotein IIb/IIIa Receptor Antagonists

Fibrinolytic and Antithrombotic Therapy ◽

10.1093/oso/9780195155648.003.0014 ◽

2006 ◽

Author(s):

Richard C. Becker ◽

Frederick A. Spencer

Keyword(s):

Platelet Aggregation ◽

Half Life ◽

Plasma Concentrations ◽

Adenosine Diphosphate ◽

Bound State ◽

Platelet Inhibition ◽

Platelet Glycoprotein ◽

Mechanical Stimuli ◽

Receptor Antagonists ◽

Dependent Inhibition

The glycoprotein (GP) IIb/IIIa (αIIb/β3) receptor totalling 50,000 to 70,000 copies per platelet represents a common pathway for platelet aggregation in response to a wide variety of biochemical and mechanical stimuli. Accordingly, it represents an attractive target for pharmacologic inhibition that can be applied to patients with acute coronary syndromes. The evolution of GPIIb/IIIa receptor antagonists began with murine monoclonal antibodies and subsequently expanded to include small peptide or nonpeptide molecules with structural similarities to fibrinogen. There are three intravenous GPIIb/IIIa receptor antagonists that have been approved by the U.S. Food and Drug Administration: . . . • Abciximab (ReoPro) . . . . . . • Tirofiban (Aggrastat) . . . . . . • Eptifibatide (Integrilin) . . . Abciximab (ReoPro) is the Fab fragment of the chimeric human–murine monoclonal antibody c7E3. Following an intravenous bolus, free plasma concentrations of abciximab decrease rapidly with an initial half-life of less than 10 minutes and a second-phase half-life of 30 minutes, representing rapid binding to the platelet GPIIb/IIIa receptor. Abciximab remains in the circulation for 10 or more days in the platelet-bound state. Intravenous administration of abciximab in doses ranging from 0.15 mg/kg to 0.3 mg/kg produces a rapid dose-dependent inhibition of platelet aggregation in response to adenosine diphosphate (ADP). At the highest dose, 80% of platelet GPIIb/IIIa receptors are occupied within 2 hours and platelet aggregation, even with 20 μM ADP, is completely inhibited. Sustained inhibition is achieved with prolonged infusions (12 to 24 hours) and low-level receptor blockade is present for up to 10 days following cessation of the infusion; however, platelet inhibition during infusions beyond 24 hours has not been well characterized. Platelet aggregation in response to 5 μM ADP returns to greater than or equal to 50% of baseline within 24 hours of drug cessation. In nearly 2,100 patients undergoing either balloon coronary angioplasty or atherectomy at high risk for ischemic (thrombotic) complications, a bolus of abciximab (0.25 mg/kg) followed by a 12-hour continuous infusion (10 μg/min) reduced the occurrence of death, the occurrence myocardial infarction (MI), or the need for an urgent intervention (repeat angioplasty, stent placement, balloon pump insertion, or bypass grafting) by 35% (EPIC Investigators, 1994).

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Contribution of ecto-5′-nucleotidase to the inhibition of platelet aggregation by human endothelial cells

Blood ◽

10.1182/blood.v96.6.2157.h8002157_2157_2162 ◽

2000 ◽

Vol 96 (6) ◽

pp. 2157-2162 ◽

Cited By ~ 6

Author(s):

Yasuko Kawashima ◽

Toshiro Nagasawa ◽

Haruhiko Ninomiya

Keyword(s):

Endothelial Cells ◽

Platelet Aggregation ◽

Adenine Nucleotides ◽

Umbilical Vein ◽

Specific Inhibitor ◽

Adenosine Diphosphate ◽

Inhibition Of Platelet Aggregation ◽

A2a Receptor ◽

Agonistic Activity ◽

Umbilical Vein Endothelial Cells

We studied the role of adenosine (Ado), which is generated from adenine nucleotides via the activity of ecto-5′-nucleotidase (ecto-5′-NT), in the inhibition of platelet aggregation by endothelial cells (ECs). The enzymatic activity of nucleotidases on human umbilical vein endothelial cells (HUVECs) was examined with regard to (1) the inhibition of adenosine diphosphate (ADP)–induced platelet aggregation and (2) the liberation of inorganic phosphate from adenine nucleotides. Adenosine 5′-monophosphate (AMP) preincubated with HUVECs significantly inhibited ADP-induced platelet aggregation. This was completely blocked by the treatment of HUVECs with a specific inhibitor of ecto-5′-NT, 5′-[αβ-methylene] diphosphate (APCP), or by the addition of an A2a receptor antagonist. Neither nitric oxide nor prostacyclin was involved in this inhibitory activity, suggesting that Ado generated in the incubation medium by the activity of 5′-NT on HUVECs inhibited platelet aggregation. When ADP was incubated on HUVECs, it lost most of its agonistic activity for platelets. Pretreatment of HUVECs with APCP at a concentration that abolished ecto-5′-NT activity partially restored ADP-induced platelet aggregation. Ecto-5′-NT contributes to EC function by inhibiting platelet aggregation in cooperation with ATP diphosphohydrolase, which degrades ADP to AMP.

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Contribution of ecto-5′-nucleotidase to the inhibition of platelet aggregation by human endothelial cells

Blood ◽

10.1182/blood.v96.6.2157 ◽

2000 ◽

Vol 96 (6) ◽

pp. 2157-2162 ◽

Cited By ~ 57

Author(s):

Yasuko Kawashima ◽

Toshiro Nagasawa ◽

Haruhiko Ninomiya

Keyword(s):

Endothelial Cells ◽

Platelet Aggregation ◽

Adenine Nucleotides ◽

Umbilical Vein ◽

Specific Inhibitor ◽

Adenosine Diphosphate ◽

Inhibition Of Platelet Aggregation ◽

A2a Receptor ◽

Agonistic Activity ◽

Umbilical Vein Endothelial Cells

Abstract We studied the role of adenosine (Ado), which is generated from adenine nucleotides via the activity of ecto-5′-nucleotidase (ecto-5′-NT), in the inhibition of platelet aggregation by endothelial cells (ECs). The enzymatic activity of nucleotidases on human umbilical vein endothelial cells (HUVECs) was examined with regard to (1) the inhibition of adenosine diphosphate (ADP)–induced platelet aggregation and (2) the liberation of inorganic phosphate from adenine nucleotides. Adenosine 5′-monophosphate (AMP) preincubated with HUVECs significantly inhibited ADP-induced platelet aggregation. This was completely blocked by the treatment of HUVECs with a specific inhibitor of ecto-5′-NT, 5′-[αβ-methylene] diphosphate (APCP), or by the addition of an A2a receptor antagonist. Neither nitric oxide nor prostacyclin was involved in this inhibitory activity, suggesting that Ado generated in the incubation medium by the activity of 5′-NT on HUVECs inhibited platelet aggregation. When ADP was incubated on HUVECs, it lost most of its agonistic activity for platelets. Pretreatment of HUVECs with APCP at a concentration that abolished ecto-5′-NT activity partially restored ADP-induced platelet aggregation. Ecto-5′-NT contributes to EC function by inhibiting platelet aggregation in cooperation with ATP diphosphohydrolase, which degrades ADP to AMP.

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Differential inhibition of platelet aggregation induced by adenosine diphosphate or a thrombin receptor-activating peptide in patients treated with bolus chimeric 7E3 Fab: Implications for inhibition of the internal pool of GPIIb/IIIa receptors

Journal of the American College of Cardiology ◽

10.1016/0735-1097(95)00391-6 ◽

1995 ◽

Vol 26 (7) ◽

pp. 1665-1671 ◽

Cited By ~ 111

Author(s):

Neal S. Kleiman ◽

Albert E. Raizner ◽

Robert Jordan ◽

Ann L. Wang ◽

Daniel Norton ◽

...

Keyword(s):

Platelet Aggregation ◽

Adenosine Diphosphate ◽

Thrombin Receptor ◽

Differential Inhibition ◽

Inhibition Of Platelet Aggregation

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Species-Dependent Inhibition of Platelet Aggregation by Adenosine and Dipyridamole: Paradoxical Potentiation in the Rat

Thrombosis and Haemostasis ◽

10.1055/s-0038-1654127 ◽

1970 ◽

Vol 23 (01) ◽

pp. 129-139 ◽

Cited By ~ 6

Author(s):

R. B Philp ◽

B Bishop ◽

Keyword(s):

Platelet Aggregation ◽

Guinea Pig ◽

Adenosine Receptors ◽

Guinea Pigs ◽

Human Subjects ◽

Adenosine Diphosphate ◽

Inhibition Of Platelet Aggregation ◽

Rabbit Platelets ◽

Dependent Inhibition ◽

Rat Platelets

SummaryPlatelets of cats, rabbits, guinea pigs, rats and human subjects were aggregated with adenosine diphosphate after having been in contact with adenosine or dipyridamole for 5 to 60 min. The species profiles of both agents were the same. Both inhibited aggregation of human and rabbit platelets and the degree of inhibition increased with the time of contact. Neither inhibited aggregation of cat or guinea-pig platelets and both potentiated the rate and extent of aggregation of rat platelets: the degree of potentiation increased with the time of contact. Some reports on the related effects of adenosine and dipyridamole are reviewed and it is suggested that the effects of dipyridamole might be due to an affinity for adenosine receptors.

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Evidence for the dependence of arterial haemostasis on ADP

Proceedings of the Royal Society of London Series B Biological Sciences ◽

10.1098/rspb.1988.0047 ◽

1988 ◽

Vol 234 (1276) ◽

pp. 255-262 ◽

Cited By ~ 11

Keyword(s):

Platelet Aggregation ◽

Vascular Injury ◽

Adenosine Diphosphate ◽

Mesenteric Arteries ◽

Receptor Antagonists ◽

Arterial Blood ◽

Anaesthetized Rats ◽

Adp Receptor ◽

Adp Receptor Antagonists ◽

Local Release

The possible involvement of adenosine diphosphate (ADP) in haemostatic platelet aggregation was investigated by determining the duration of primary haemorrhage as standardized bleeding times from punctures of small mesenteric arteries in anaesthetized rats. The bleeding times were highly significantly increased by infusing into the mesenteric arterial blood flowing towards the punctures either the nucleotidedephosphorylating enzyme apyrase or the ADP-receptor antagonists ATP, adenosine 5'-(β,γ-methylene)triphosphonate (AMP-PCP) or 2-methylthioadenosine 5'-(β,γ-methylene)triphosphonate (2-MeS-AMP-PCP). The increases in bleeding times could not be accounted for by local vasodilator effects of the agents. It is concluded that the presence of ADP through local release and/or formation at sites of vascular injury contributes significantly to haemostasis, presumably by accelerating platelet aggregation.

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