cangrelor and Angina--Unstable

Platelets possess three P2 receptors for adenine nucleotides: P2Y1 and P2Y12, which interact with ADP, and P2X1, which interacts with ATP. The interaction of adenine nucleotides with their platelet receptors plays an important role in thrombogenesis. The thienopyridine ticlopidine, an antagonist of the platelet P2Y12 ADP receptor, reduces the incidence of vascular events in patients at risk, but it also has some important drawbacks: a relatively high incidence of toxic effects; delayed onset of action; high inter-individual variability in response. Another thienopyridine, clopidogrel, has superseded ticlopidine, because it is an efficacious antithrombotic drug and is less toxic than ticlopidine. However, the high inter-patient variability in response still remains an important issue. These drawbacks justify the continuing search for agents that can further improve the clinical outcome of patients with atherosclerosis through greater efficacy and/or safety. A new thienopyridyl compound prasugrel, which is characterized by higher potency and faster onset of action compared with clopidogrel, is currently under clinical evaluation. Two direct and reversible P2Y12 antagonists, cangrelor and AZD6140, have very rapid onset and reversal of platelet inhibition, which make them attractive alternatives to thienopyridines, especially when rapid inhibition of platelet aggregation or its quick reversal are required. Along with new P2Y12 antagonists, inhibitors of the other platelet receptor for ADP, P2Y1, and of the receptor for ATP, P2X1, are under development and may prove to be effective antithrombotic agents.

Topics: Adenosine; Adenosine Monophosphate; Angina, Unstable; Animals; Blood Platelets; Clopidogrel; Coronary Disease; Coronary Thrombosis; Drug Interactions; Fibrinolytic Agents; Humans; Myocardial Infarction; Piperazines; Platelet Aggregation; Platelet Aggregation Inhibitors; Prasugrel Hydrochloride; Purinergic P2 Receptor Antagonists; Randomized Controlled Trials as Topic; Receptors, Purinergic P2; Receptors, Purinergic P2X; Syndrome; Thiophenes; Ticagrelor; Ticlopidine

Platelets play a central role in the pathophysiology of acute coronary syndromes (ACS). Dual antiplatelet therapy has resulted in significant advances in the treatment of ACS; however, ACS remains an important cause of morbidity and mortality. Important limitations exist among the current antiplatelet agents and therefore a pressing need for the development of improved antiplatelet agents exists. Three antiplatelet agents currently under investigation (prasugrel, AZD6140, and cangrelor) in clinical trials for the treatment of ACS appear promising.

Topics: Adenosine; Adenosine Monophosphate; Angina, Unstable; Blood Platelets; Humans; Myocardial Infarction; Piperazines; Platelet Aggregation Inhibitors; Prasugrel Hydrochloride; Randomized Controlled Trials as Topic; Thiophenes; Ticagrelor; Treatment Outcome

Thrombin generation and platelet aggregation in the disrupted atherosclerotic plaque are the major reasons for thrombus formation associated with acute coronary events. AR-C69931MX is a new agent that inhibits adenosine diphosphate-induced platelet aggregation by antagonism of the P(2T) purinoceptor.. This study assessed the safety profile, tolerability, and plasma concentrations at steady state of intravenous AR-C69931MX in patients with unstable angina pectoris or non-Q-wave myocardial infarction (MI).. This was a Phase II, multicenter, double-blind, randomized, placebo-controlled trial. Patients with unstable angina or non-Q-wave MI were randomized to a 72-hour infusion of AR-C69931MX or placebo as adjunctive therapy to aspirin and low-molecular-weight heparin. Other treatment was at the discretion of the local investigator. Outcomes were assessed at 30 days.. Ninety-four patients were randomized and 91 received treatment (45 AR-C69931MX, 46 placebo). Plasma concentrations of AR-C69931MX were within the expected range, there were no signs of accumulation, and interindividual variability in clearance was low. Four patients receiving AR-C69931MX discontinued treatment due to minor bleeding events, and 5 patients receiving placebo discontinued treatment due to other adverse events or deterioration in their condition. No serious bleeding events were seen during treatment. The incidence of > or = 1 episode of minor bleeding was slightly higher in patients receiving AR-C69931MX compared with those receiving placebo (38% vs 26%, respectively). The drug was well tolerated hemodynamically, and there were no significant changes in other laboratory values between groups.. As adjunctive therapy to aspirin and low-molecular-weight heparin in patients with unstable angina or non-Q-wave MI, intravenous AR-C69931MX was well tolerated, with no difference in the incidence of serious adverse events compared with placebo.

Topics: Adenosine Monophosphate; Aged; Angina, Unstable; Double-Blind Method; Female; Hemodynamics; Humans; Infusions, Intravenous; Male; Metabolic Clearance Rate; Middle Aged; Myocardial Infarction; Platelet Aggregation

Platelet aggregation is the central process in the pathophysiology of acute coronary syndromes. ADP contributes to thrombosis by activating platelets, and AR-C69931MX is a specific antagonist of this process acting at the P2T receptor. At 5 hospitals, 39 patients with unstable angina or non-Q wave myocardial infarction, who were receiving aspirin and heparin, were administered intravenous AR-C69931MX with stepped dose increments over 3 h to a plateau of either 2 microg/kg/min for 21 h (Part 1; n = 12) or up to 69 h (Part 2; n = 13) or 4 microg/kg/min for up to 69 h (Part 3: n = 14). Safety parameters, platelet aggregation (PA) induced by ADP 3 micromol/L (impedance aggregometry), bleeding time (BT) and plasma concentrations of AR-C69931XX were assessed. AR-C69931MX was well tolerated. 33 patients completed the study. There were no deaths at 30 days and no serious adverse events attributed to AR-C69931MX. Trivial bleeding (56%) was common. At 24 h, mean inhibition of PA was 96.0 +/- 8.6, 94.9 +/- 14.4 and 98.7 +/- 2.1% and BT was 9.5 +/- 8.4, 14.0 +/- 9.7 and 16.0 +/- 11.1 min for Parts 1, 2 and 3 respectively. At 1 h post-infusion, mean inhibition of PA was 36.2 +/- 39.2, 20.7 +/- 25.9 and 40.7 +/- 36.7% respectively. 90% patients had a plasma half-life for AR-C69931XX of <9 min. In conclusion, AR-C69931MX is a potent, short-acting platelet ADP receptor antagonist suitable for further studies as an antithrombotic agent.

Topics: Acute Disease; Adenosine Monophosphate; Adult; Aged; Angina, Unstable; Aspirin; Blood Coagulation Tests; Consumer Product Safety; Coronary Disease; Dose-Response Relationship, Drug; Drug Therapy, Combination; Electrocardiography; Female; Heparin; Humans; Male; Membrane Proteins; Middle Aged; Myocardial Infarction; Platelet Aggregation Inhibitors; Purinergic P2 Receptor Antagonists; Receptors, Purinergic P2Y12