ro-48-3657 and orbofiban

Despite the efficacy of intravenous glycoprotein IIb/IIIa inhibition in patients undergoing percutaneous coronary intervention and those presenting with acute coronary syndromes, the application of oral glycoprotein IIb/IIIa inhibition to the chronic management of coronary artery disease has not met with the same success. To explain these results, factors related to dosing, and inadequate inhibition or activation of platelet pro-coagulant activity have been recently suggested. However, although the disparity between intravenous and oral glycoprotein IIb/IIIa experience remains largely enigmatic, the discordant effect on ischemic endpoints observed within the phase III oral glycoprotein IIb/IIIa inhibitor trials potentially implicates a mechanism unrelated to platelet function.

Topics: Administration, Oral; Alanine; Benzamidines; Coronary Disease; Humans; Integrins; Oximes; Piperidines; Platelet Activation; Platelet Aggregation; Platelet Aggregation Inhibitors; Platelet Glycoprotein GPIIb-IIIa Complex; Pyrrolidines; Randomized Controlled Trials as Topic

Numerous clinical trials have established the benefits of intravenous glycoprotein IIb/IIIa inhibition in the management of coronary artery disease. In contrast, the recent large-scale, placebo-controlled, randomized trials of the oral glycoprotein IIb/IIIa antagonists have failed to provide commensurate reductions in late composite ischemic end points despite potent inhibition of platelet aggregation.. The ORs for death, myocardial infarction, urgent revascularization, and major bleeding from the 4 large-scale, placebo-controlled, randomized trials with oral glycoprotein IIb/IIIa inhibitors were calculated and combined. Stratification by low-dose or high-dose therapy and the use of concurrent aspirin was also undertaken. In 33 326 patients followed for >30 days, a consistent and statistically significant increase in mortality was observed with oral glycoprotein IIb/IIIa therapy (OR, 1.37; 95% CI, 1.13 to 1.66; P:=0.001). This effect was evident regardless of aspirin coadministration and treatment with either low-dose or high-dose therapy. Although a reduction in urgent revascularization was observed with oral glycoprotein IIb/IIIa inhibition, pooled analysis favored an increase in myocardial infarction that did not demonstrate statistical significance.. Although we found a highly significant excess in mortality consistent across 4 trials with 3 different oral glycoprotein IIb/IIIa inhibitor agents, this was associated with a reduction in the need for urgent revascularization and no increase in myocardial infarction. These findings suggest the potential for a direct toxic effect with these agents and argue against a prothrombotic mechanism. Further investigation to elucidate the cause of this increased fatality risk is warranted.

Topics: Administration, Oral; Alanine; Aspirin; Benzamidines; Clinical Trials, Phase III as Topic; Coronary Disease; Dose-Response Relationship, Drug; Drug Therapy, Combination; Hemorrhage; Humans; Incidence; Multicenter Studies as Topic; Myocardial Infarction; Oximes; Piperidines; Platelet Glycoprotein GPIIb-IIIa Complex; Pyrrolidines; Randomized Controlled Trials as Topic

Platelet membrane glycoprotein IIb/IIIa inhibitors, a new class of potent antiplatelet agents, have been used in the treatment of acute coronary syndromes as well as in the prevention of complications after percutaneous coronary interventions. Approximately 50,000 patients with coronary artery disease have been enrolled in randomized studies of glycoprotein IIb/IIIa inhibitors. The purpose of this article is to review the pharmacology of glycoprotein IIb/IIIa inhibitors, the results of the clinical trials using these agents, and their current use in percutaneous coronary interventions and the treatment of acute coronary syndromes.

Topics: Abciximab; Acetates; Acute Disease; Administration, Oral; Alanine; Angioplasty, Balloon, Coronary; Antibodies, Monoclonal; Anticoagulants; Benzamidines; Coronary Disease; Eptifibatide; Hemorrhage; Humans; Immunoglobulin Fab Fragments; Myocardial Infarction; Oximes; Peptides; Piperidines; Platelet Aggregation Inhibitors; Platelet Glycoprotein GPIIb-IIIa Complex; Pyrrolidines; Randomized Controlled Trials as Topic; Stents; Syndrome; Thrombocytopenia; Thrombolytic Therapy; Tirofiban; Tyrosine

Platelet aggregation plays a central role in the pathogenesis of thrombosis and the acute coronary syndromes. When given intravenously, potent selective antagonists of fibrinogen binding to the glycoprotein (GP) IIb/IIIa receptor, the final common pathway for platelet aggregation, have been effective in the treatment of acute coronary syndromes. Their benefit ceases, however, with the end of the infusion. Aspirin reduces the incidence of secondary vascular events by 25% to 30% after an acute coronary syndrome, and clopidogrel provides modest improvement over aspirin. However, both are relatively weak antiplatelet agents that each block only one of many pathways to platelet activation and surface membrane expression of the competent GP IIb/IIIa receptor. With the success of the intravenous GP IIb/IIIa antagonists in the acute setting, recent interest has focused on the potential benefit of oral GP IIb/IIIa antagonists used long-term for secondary prevention. The oral agents tested in phase III studies thus far have not performed up to expectations, however. The following paper reviews these studies and the implications of their results.

Topics: Alanine; Angina, Unstable; Aspirin; Benzamidines; Clinical Trials, Phase II as Topic; Clinical Trials, Phase III as Topic; Humans; Myocardial Infarction; Oximes; Piperidines; Platelet Aggregation Inhibitors; Platelet Glycoprotein GPIIb-IIIa Complex; Pyrrolidines; Syndrome; Treatment Outcome

The central role of platelet-rich thrombus in the pathogenesis of acute coronary syndromes (ACSs) is well-known. Glycoprotein IIb/IIIa (Gp IIb/IIIa) receptor antagonists are potent inhibitors of platelet function that may be expected to affect favorably the natural history of ACSs.. To define the optimal role of Gp IIb/IIIa inhibitors in treatment strategies for ACSs.. A MEDLINE search was performed to identify all English-language articles regarding use of Gp IIb/IIIa inhibitors in ACSs published between 1966 and June 2000. In addition, relevant abstracts from the annual meetings of the American Heart Association, American College of Cardiology, and the European Society of Cardiology were reviewed.. Only studies of 500 or more patients were included. Of 15 studies identified, 10 randomized, placebo-controlled, double-blind trials of Gp IIb/IIIa inhibitors in ACSs were selected for review.. Data quality was determined by publication in the peer-reviewed literature or presentation at an official cardiology society-sponsored meeting, as well as by verification with the primary author.. Three members of this class of drugs are available for intravenous use. Abciximab, eptifibatide, and tirofiban hydrochloride, each have data demonstrating their value in improving the outcomes of patients presenting with ACSs. Current evidence supports use of these drugs in both conservative and invasive treatment strategies. Glycoprotein IIb/IIIa-blocking therapy is safe, and with proper precautions, bleeding risks can be minimized. Biological differences exist among these agents, but as of yet, no head-to-head comparisons have been made of their clinical efficacy. Unlike intravenous Gp IIb/IIIa inhibitors, available data regarding any role of oral Gp IIb/IIIa inhibitors are not favorable.. Current data indicate that intravenous Gp IIb/IIIa inhibitor therapy merits a prominent role in the initial management of patients with ACSs. JAMA. 2000;284:1549-1558.

Topics: Abciximab; Acute Disease; Alanine; Angina, Unstable; Angioplasty, Balloon, Coronary; Antibodies, Monoclonal; Anticoagulants; Benzamidines; Drug Therapy, Combination; Eptifibatide; Heparin, Low-Molecular-Weight; Humans; Immunoglobulin Fab Fragments; Myocardial Infarction; Oximes; Peptides; Piperidines; Platelet Aggregation Inhibitors; Platelet Glycoprotein GPIIb-IIIa Complex; Pyrrolidines; Randomized Controlled Trials as Topic; Stents; Tirofiban; Tyrosine

Several oral glycoprotein (GP) IIb/IIIa antagonists, Sibrafiban, Orbofiban and Lotrafiban, have been studied in large phase III trials; each has failed to provide efficacy and has been associated with increased mortality. Roxifiban has pharmacokinetic and pharmacodynamic properties believed to be more favorable than the earlier oral agents. Here, we revisit the controversial hypothesis of platelet activation liabilities of GP IIb/IIIa antagonists. The effects of site occupancy by four fibans (Roxifiban, Sibrafiban, Orbofiban and Lotrafiban) on platelet activation was assessed using P-selectin expression, fibrinogen binding and microaggregate formation. All four fibans inhibited ADP and TRAP-stimulated fibrinogen binding and microaggregate formation in a concentration-dependent manner, whereas P-selectin expression was relatively unaltered. To more vigorously test for activation liabilities, the effects of transition from peak to trough receptor occupancy upon platelet stimulation was analyzed. The high affinity of Roxifiban for resting platelets precluded reduction of site occupancy by dialysis or gel filtration. A method was developed that takes advantage of the rapid equilibrium of Roxifiban between platelets and soluble GPIIb/IIIa. The platelet occupancy is controlled by the ratio of platelet GPIIb/IIIa to soluble GPIIb/IIIa. This method allows in vitro investigation of peak/trough transitions on platelet activation. A decrease in site occupancy from peak to trough of Roxifiban or Sibrafiban did not result in increased activation of platelets. The loss of platelet-bound antagonist upon incubation with purified soluble GPIIb/IIIa returned fibrinogen binding/microaggregate formation to no drug levels. In conclusion, these studies do not provide evidence for an activation liability of GPIIb/IIIa antagonists in vitro.

Topics: Alanine; Amidines; Benzodiazepines; Blood Platelets; Humans; In Vitro Techniques; Isoxazoles; Oximes; P-Selectin; Piperidines; Platelet Adhesiveness; Platelet Aggregation; Platelet Glycoprotein GPIIb-IIIa Complex; Pyrrolidines; Thrombosis