terutroban and Thrombosis

Antiplatelet agents are a cornerstone in the treatment of acute arterial thrombotic events and in the prevention of thrombus formation. However, existing antiplatelet agents (mainly aspirin, the combination of aspirin and dipyridamole and clopidogrel) reduce the risk of vascular events only by about one quarter compared with placebo. As a consequence, more efficacious antiplatelet therapies with a reduced bleeding risk are needed. We give an overview of several new antiplatelet agents that are currently investigated in secondary stroke prevention: adenosine 5'-diphosphonate receptor antagonists, cilostazol, sarpogrelate, terutroban and SCH 530348. There are unique features in secondary stroke prevention that have to be taken into account: ischaemic stroke is a heterogeneous disease caused by multiple aetiologies and the blood-brain barrier is disturbed after stroke which may result in a higher intracerebral bleeding risk. Several small randomized trials indicated that the combination of aspirin and clopidogrel might be superior to antiplatelet monotherapy in the acute and early post-ischaemic phase. There is an ongoing debate about antiplatelet resistance. Decreasing response to aspirin is correlated independently with an increased risk of cardiovascular events. However, there is still no evidence from randomized trials linking aspirin resistance and recurrent ischaemic events. Similarly, randomized trials have not demonstrated a clinical significantly decreased antiplatelet effect by the concomitant use of clopidogrel and proton pump inhibitors. Nevertheless, a routine use of this drug combination is not recommended.

Topics: Aspirin; Blood-Brain Barrier; Cilostazol; Clopidogrel; Dipyridamole; Drug Interactions; Drug Therapy, Combination; Humans; Lactones; Naphthalenes; Platelet Aggregation Inhibitors; Propionates; Pyridines; Randomized Controlled Trials as Topic; Secondary Prevention; Stroke; Succinates; Tetrazoles; Thrombosis; Ticlopidine

Conventional antiplatelet agents such as aspirin, ticlopidine, and clopidogrel are currently used in the prevention of cardiovascular and cerebrovascular events. However, side effects such as bleeding complications and gastrointestinal disorders and, in some patients, resistance have made the development of new agents desirable. Recently, thromboxane receptors (thromboxane and prostaglandin endoperoxide PGG2-PGH2 receptors) called TP receptors have received increasing attention. These receptors are membrane-bound G-coupled receptors found not only on platelets but also on macrophages, monocytes, vascular endothelial cells, and smooth muscle cells. Antagonists of TP receptors have advantages over aspirin as they not only block the effect of thromboxane A2 on platelets, but also inhibit other ligands such as prostaglandin endoperoxides and isoprostanes. Given the distribution of TP receptors in platelets, in circulating inflammatory cells, in the vascular wall and in atherosclerotic plaques, they also inhibit the effects of thromboxane A2 over TP receptors on vascular cells or in the plaque. Terutroban (Triplion or S18886), a new oral specific TP receptor antagonist, has, aside from being an antithrombotic agent, important vascular properties. It improves endothelial function and has an antiatherosclerotic effect. The potential therapeutic applications of terutroban in the prevention of atherothrombosis, particularly in the cerebrovascular and cardiovascular fields including stroke and coronary artery disease, are based on a number of convincing experimental animal and clinical studies. A large trial is currently comparing the efficacy and safety of terutroban versus aspirin in secondary prevention of cardiovascular events in patients who have suffered a stroke or transient ischemic attack (PERFORM Study).

Topics: Atherosclerosis; Humans; Naphthalenes; Propionates; Receptors, Thromboxane; Stroke; Thrombosis

Acute thrombosis is a threat in patients undergoing percutaneous coronary intervention with stent implantation. Our objective was to determine if stent-induced thrombus formation could be inhibited by oral treatment with a thromboxane A(2)/prostaglandin H(2) receptor antagonist (TPr; S18886) as an alternative to standard therapy. Pigs were allocated in the following treatment (p.o) groups: I) clopidogrel (CLOP); II) ASA; III) S18886; IV) ASA+CLOP; and V) placebo-control. Damaged vessel was placed in the Badimon chamber containing a stent and perfused at 212/s. Antithrombotic effects were assessed as (111)In-platelet deposition (PD) in two series (60 and 180 min after drug intake). Fibrin(ogen) deposition, light transmittance aggregometry (LTA; collagen, U46619, and ADP), and bleeding time (BT) were also evaluated. After 60 min S18886 reduced PD < or =48%, 40%, and 35% vs placebo, CLOP-, and ASA-treated animals, respectively (P < 0.05), while ASA+CLOP showed a 58% reduction versus placebo (P < 0.01). After 3 hours, ASA+CLOP decreased PD by 55%, S18886 by 40%, CLOP alone by 28% (P < 0.05), and ASA showed no inhibition versus placebo. Similar effects were found in S18886- and ASA+CLOP-treated animals at both times. Fibrin(ogen) deposition followed the same pattern. Collagen-induced LTA was significantly reduced by ASA, ASA+CLOP, and S18886; S18886 abolished U46619-induced LTA; and, CLOP +/- ASA reduced ADP-induced LTA in a time-dependent manner. TPr blockade did not prolong BT, whereas CLOP +/- ASA significantly did (P < 0.0001). In conclusion, blockade of the TPr provided a fast and potent platelet inhibitory effect in a porcine model of in-stent thrombosis comparable to that of blocking both the ADP receptor and cyclooxygenase activation; in addition, TPr provided a more favorable bleeding risk profile.

Topics: Administration, Oral; Animals; Aorta; Aspirin; Bleeding Time; Blood Coagulation; Clopidogrel; Disease Models, Animal; Fibrin; Fibrinogen; Fibrinolytic Agents; Hemorrhage; Naphthalenes; Platelet Activation; Platelet Aggregation Inhibitors; Propionates; Prosthesis Design; Receptors, Thromboxane A2, Prostaglandin H2; Stainless Steel; Stents; Swine; Thrombosis; Ticlopidine; Time Factors

A potent thromboxane A2/PGH2 (TP)-receptor antagonist, S18886, was evaluated for its antithrombotic property in a dog model of acute periodic platelet-mediated thrombosis in stenosed coronary arteries with endothelial damage. After thrombosis had been obtained in 11 dogs, S18886 (300 microg/kg bolus) was administered IV. Heart rate, systemic blood pressure, and coronary blood flow were continuously recorded. Ex vivo whole blood platelet aggregation (PA), blood pH, hematocrit, platelet count, PO2, PCO2, and bleeding times were measured before and 30 minutes after administration of S18886. S18886 completely inhibited thrombosis in all dogs in approximately 5-10 minutes. No change in heart rate, blood pressure, pH, PO2, PCO2, platelet count, or bleeding time and a slight but significant elevation in hematocrit occurred. Infusion of epinephrine IV after complete inhibition of thrombosis by S18886 partially restored thrombosis in 3 of the 11 dogs. PA induced by collagen (4 microg/mL), collagen (0.25 microg/mL) plus epinephrine (1 microg/mL), collagen (1 microg/mL) plus epinephrine (1 microg/mL), ADP (40 microM) plus epinephrine (1 microg/mL), and phorbol 12-myristate 13-acetate (0.5 nM) were attenuated by 90 +/- 8% (P < 0.005), 98 +/- 2% (P < 0.05), 78 +/- 6% (P < 0.005), 70 +/- 10% (P < 0.005), and 28 +/- 8% (P < 0.05), respectively. In conclusion, S18886 is a potent platelet inhibitor that attenuates in vivo platelet-dependent thrombosis in the experimental dog model and reduces ex vivo platelet aggregation.

Topics: Animals; Coronary Stenosis; Coronary Vessels; Disease Models, Animal; Dogs; Drug Evaluation, Preclinical; Female; Male; Molecular Structure; Naphthalenes; Platelet Aggregation; Propionates; Receptors, Thromboxane; Receptors, Thromboxane A2, Prostaglandin H2; Regional Blood Flow; Thrombosis; Time Factors