vorapaxar and thienopyridine

Platelet inhibitors are the mainstay treatment for patients with vascular diseases. The current 'gold standard' antiplatelet agent clopidogrel has several pharmacological and clinical limitations that have prompted the search for more effective platelet antagonists. The candidates include various blockers of the purinergic P2Y12 receptor such as prasugrel, an oral irreversible thienopyridine; two adenosine triphosphate analogues that bind reversibly to the P2Y12 receptor: ticagrelor (oral) and cangrelor (intravenous); elinogrel, a direct-acting reversible P2Y12 receptor inhibitor (the only antiplatelet compound that can be administered both intravenously and orally); BX 667, an orally active and reversible small-molecule P2Y12 receptor antagonist; SCH 530348, SCH 205831, SCH 602539 and E5555, highly selective and orally active antagonists on the protease-activated receptor 1. A number of drugs also hit new targets: terutroban, an oral, selective and specific inhibitor of the thromboxane receptor; ARC1779, a second-generation, nuclease resistant aptamer which inhibits von Willebrand factor-dependent platelet aggregation; ALX-0081, a bivalent humanized nanobody targeting the GPIb binding site of von Willebrand factor and AJW200, an IgG4 monoclonal antibody of von Willebrand factor. The pharmacology and clinical profiles of new platelet antagonists indicate that they provide more consistent, more rapid and more potent platelet inhibition than agents currently used. Whether these potential advantages will translate into clinical advantages will require additional comparisons in properly powered, randomized, controlled trials.

Topics: Adenosine; Adenosine Monophosphate; Benzofurans; Blood Platelets; Carbamates; Clinical Trials as Topic; Clopidogrel; Humans; Lactones; Piperazines; Platelet Aggregation; Platelet Aggregation Inhibitors; Prasugrel Hydrochloride; Pyridines; Receptor, PAR-1; Receptors, Proteinase-Activated; Thiophenes; Ticagrelor; Ticlopidine; von Willebrand Factor

Vorapaxar is effective in the prevention of secondary atherothrombotic events, although the efficacy/safety balance appears less favorable in the treatment of patients with non-ST-segment elevation (NSTE) acute coronary syndrome (ACS). We hypothesized that patients with NSTE ACS already receiving thienopyridine prior to the ACS event may show differential efficacy/safety effects with vorapaxar vs. placebo added to their standard care.. We studied 12,944 patients from the Thrombin Receptor Antagonist for Clinical Event Reduction in Acute Coronary Syndrome (TRACER) trial with respect to thienopyridine use before admission for the index NSTE ACS event. The primary endpoint was a composite of cardiovascular death, myocardial infarction, stroke, rehospitalization for ischemia, and urgent revascularization. The key secondary endpoint was a composite of cardiovascular death, myocardial infarction, and stroke. Safety endpoints were bleeding complications.. TRACER was largely conducted in thienopyridine-naïve patients with unknown tolerance to multiple antiplatelet treatments. Patients receiving thienopyridine before the index event may have had an attenuated increase in bleeding when adding vorapaxar, whereas concomitantly adding vorapaxar and thienopyridine in naïve patients may have uncovered a latent susceptibility to bleeding.

Topics: Acute Coronary Syndrome; Aged; Female; Hemorrhage; Humans; Lactones; Male; Middle Aged; Platelet Aggregation Inhibitors; Pyridines; Secondary Prevention; Treatment Outcome

Vorapaxar antagonizes protease-activated receptor 1, the primary receptor for thrombin on human platelets, and reduces recurrent thrombotic events in stable patients with a previous myocardial infarction (MI). We wished to determine whether the efficacy and safety of antiplatelet therapy with vorapaxar was modified by concurrent thienopyridine use.. The Thrombin Receptor Antagonist in Secondary Prevention of Atherothrombotic Ischemic Events-Thrombolysis in Myocardial Infarction 50 (TRA 2°P-TIMI 50) was a randomized, double-blind, placebo-controlled trial of vorapaxar in 26,449 patients with previous atherothrombosis. This prespecified analysis included 16,897 patients who qualified with a MI in the preceding 2 weeks to 12 months and was restricted to patients without a history of stroke or transient ischemic attack given its contraindication in that population. Randomization was stratified on the basis of planned thienopyridine use. Thienopyridine was planned at randomization in 12,410 (73%). Vorapaxar significantly reduced the composite of cardiovascular death, MI, and stroke in comparison with placebo regardless of planned thienopyridine therapy (planned thienopyridine, hazard ratio, 0.80, 0.70-0.91, P<0.001; no planned thienopyridine, hazard ratio, 0.75; 0.60-0.94, P=0.011; P-interaction=0.67). Findings were similar when patients were stratified by actual thienopyridine use at baseline (P-interaction=0.82) and through 18 months (P-interaction=0.44). Global Use of Strategies to Open Occluded Coronary Arteries (GUSTO) moderate or severe bleeding risk was increased with vorapaxar and was not significantly altered by planned thienopyridine (planned, hazard ratio, 1.50; 1.18-1.89, P<0.001; no planned, hazard ratio, 1.90, 1.17-3.07, P=0.009; P-interaction=0.37) or actual thienopyridine use (P-interaction=0.24).. Vorapaxar reduced cardiovascular death, MI, or stroke in stable patients with a history of previous MI, whether treated concomitantly with a thienopyridine or not. The relative risk of moderate or severe bleeding was similarly increased irrespective of thienopyridine use.. URL: http://www.clinicaltrials.gov. Unique identifier: NCT00526474.

Topics: Aged; Double-Blind Method; Drug Therapy, Combination; Female; Humans; Internationality; Ischemic Attack, Transient; Lactones; Male; Middle Aged; Myocardial Infarction; Pyridines; Receptor, PAR-1; Receptors, Thrombin; Secondary Prevention; Stroke; Treatment Outcome

Vorapaxar is an antagonist of the protease activated receptor-1 (PAR-1), the principal platelet thrombin receptor. The Thrombin Receptor Antagonist for Clinical Event Reduction (TRACER) trial evaluated vorapaxar compared to placebo in non-ST-elevation (NSTE)-acute coronary syndrome (ACS) patients. It was the study's objective to assess the pharmacodynamic effects of vorapaxar versus placebo that included aspirin or a thienopyridine or, frequently, a combination of both agents in NSTE-ACS patients. In a substudy involving 249 patients, platelet aggregation was assessed by light transmittance aggregometry (LTA) in 85 subjects (41 placebo, 44 vorapaxar) using the agonists thrombin receptor activating peptide (TRAP, 15 μM), adenosine diphosphate (ADP, 20 μM), and the combination of collagen-related peptide (2.5 μg/ml) + ADP (5 μM) + TRAP (15 μM) (CAT). VerifyNow® IIb/IIIa and vasodilator-stimulated phosphoprotein (VASP) phosphorylation assays were performed, and platelet PAR-1 expression, plasma platelet/endothelial and inflammatory biomarkers were determined before and during treatment. LTA responses to TRAP and CAT and VerifyNow results were markedly inhibited by vorapaxar. Maximal LTA response to TRAP (median, interquartile range) 2 hours post loading dose: placebo 68% (53-75%) and vorapaxar 3% (2-6%), p<0.0001. ADP inhibition was greater in the vorapaxar group at 4 hours and one month (p<0.01). In contrast to the placebo group, PAR-1 receptor number in the vorapaxar group at one month was significantly lower than the baseline (179 vs 225; p=0.004). There were significant changes in selected biomarker levels between the two treatment groups. In conclusion, vorapaxar caused a potent inhibition of PAR-1-mediated platelet aggregation. Further studies are needed to explore vorapaxar effect on P2Y12 inhibition, PAR-1 expression and biomarkers and its contribution to clinical outcomes.

Topics: Acute Coronary Syndrome; Adenosine Diphosphate; Aged; Aspirin; Biomarkers; Blood Platelets; Cells, Cultured; Europe; Female; Follow-Up Studies; Humans; Inflammation Mediators; Lactones; Male; Middle Aged; North America; Platelet Aggregation; Pyridines; Receptor, PAR-1; Receptors, Thrombin