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Background and aims: It is well known that elevated cholesterol is associated with enhanced platelet aggregation and patients suffering from familial hypercholesterolemia (FH) have a high risk of thrombotic cardiovascular events. Although decreasing cholesterol level is associated with attenuation of platelet hyperactivity, there are currently no data on the effect of convertase subtilisin/kexin type 9 monoclonal antibodies (PCSK9ab) on platelet reactivity in FH. The aim of the study was to analyse the impact of different therapies including PCSK9ab on platelet aggregation in FH. Methods: This study enrolled all 15 patients treated in the University Hospital Hradec Králové for FH. PCSK9ab have been administered in 12 of 15 patients while 8 patients were also undergoing lipid apheresis. Blood samples from all patients including pre- and post-apheresis period were tested for platelet aggregation triggered by 7 inducers, and the effect of 3 clinically used drugs (acetylsalicylic acid, ticagrelor and vorapaxar) was compared as well. Results: Although apheresis decreased the reactivity of platelets in general, platelet responses were not different between non-apheresis patients treated with PCSK9ab and apheresis patients (post-apheresis values) with the exception of ristocetin. However, when compared to age-matched healthy population, FH patients had significantly lower platelet aggregation responses to 4 out of 7 used inducers and higher profit from 2 out of 3 used antiplatelet drugs even after exclusion of FH patients regularly receiving conventional antiplatelet treatment. Conclusion: This study showed for the first time the suitability of PCSK9ab treatment for reduction of platelet reactivity in FH patients. [ABSTRACT FROM AUTHOR]

Background Thromboembolic events are prevalent in chronic kidney disease (CKD) patients due to increased thrombin generation leading to a hypercoagulable state. We previously demonstrated that inhibition of protease-activated receptor-1 (PAR-1) by vorapaxar reduces kidney fibrosis. Methods We used an animal model of unilateral ischemia–reperfusion injury-induced CKD to explore the tubulovascular crosstalk mechanisms of PAR-1 in acute kidney injury (AKI)-to-CKD transition. Results During the early phase of AKI, PAR-1-deficient mice exhibited reduced kidney inflammation, vascular injury, and preserved endothelial integrity and capillary permeability. During the transition phase to CKD, PAR-1 deficiency preserved kidney function and diminished tubulointerstitial fibrosis via downregulated transforming growth factor-β/Smad signaling. Maladaptive repair in the microvasculature after AKI further exacerbated focal hypoxia with capillary rarefaction, which was rescued by stabilization of hypoxia-inducible factor and increased tubular vascular endothelial growth factor A in PAR-1-deficient mice. Chronic inflammation was also prevented with reduced kidney infiltration by both M1- and M2-polarized macrophages. In thrombin-induced human dermal microvascular endothelial cells (HDMECs), PAR-1 mediated vascular injury through activation of NF-κB and ERK MAPK pathways. Gene silencing of PAR-1 exerted microvascular protection via a tubulovascular crosstalk mechanism during hypoxia in HDMECs. Finally, pharmacologic blockade of PAR-1 with vorapaxar improved kidney morphology, promoted vascular regenerative capacity, and reduced inflammation and fibrosis depending on the time of initiation. Conclusions Our findings elucidate a detrimental role of PAR-1 in vascular dysfunction and profibrotic responses upon tissue injury during AKI-to-CKD transition and provide an attractive therapeutic strategy for post-injury repair in AKI. [ABSTRACT FROM AUTHOR]

BackgroundProtease-activated receptor-1 antagonism by vorapaxar could facilitate arteriovenous fistula maturation but may increase bleeding risk.ObjectiveThe primary objective of the Vorapaxar Study for Maturation of arteriovenous fistula for Hemodialysis Access (VorapAccess) was to determine if vorapaxar improves arteriovenous fistula functional maturation in patients with end-stage renal disease.MethodsVorapAccess was a randomized, placebo-controlled, double-blind pilot trial comparing 2.5 mg vorapaxar per day with placebo for twelve weeks starting on day two after arteriovenous fistula creation. The primary outcome was time to functional maturation defined as successful cannulation for six hemodialysis sessions within three weeks. The planned sample size was 50 participants. The study was terminated early after withdrawal of planned financial support. Given the small number of randomized patients, we performed descriptive analyses without inference testing.ResultsA total of 13 participants were randomly allocated study drug (six vorapaxar and seven placebo). The median age was 56 years and seven participants (54%) were female. The median (minimum-maximum) days to functional maturation were 169 (77-287) days in the vorapaxar group and 145 (48-198) days in the placebo group. Six of the 13 (46%) participants had arteriovenous fistula functional maturation within 180 days; two of six (33%) in the vorapaxar group and four of seven (57%) in the placebo group. There was one bleeding event in the placebo group.ConclusionFewer than half of participants had functional maturation within 180 days after surgery, suggesting a major need for agents or strategies that enhance arteriovenous fistula maturation.

Background: Heart failure (HF) is a growing public health problem and ischemic heart disease is an important risk factor. Understanding the epidemiology of HF in patients with atherosclerosis may help identify subgroups at greater risk who have the potential to derive greater benefit from preventive strategies. Methods and Results: The TRA 2°P‐TIMI 50 trial randomized 26,449 patients with stable atherosclerosis to the antiplatelet agent vorapaxar versus placebo. Hospitalization for HF (HHF) endpoints were adjudicated from serious adverse events by blinded structured review using established definitions. HHF incidence was estimated using Kaplan–Meier analysis. Independent predictors of HHF risk were identified using multivariable logistic regression. The effect of vorapaxar on HHF risk was explored using Cox regression. The estimated incidence of HHF at 3 years was 1.6%. Independent predictors of HHF included prior HF (adjusted odds ratio [adj‐OR]: 8.31; 95% confidence interval [CI]: 6.56–10.54), age (adj‐OR [per 10 years]: 1.67; 95% CI: 1.47–1.89), type 2 diabetes mellitus (T2DM; adj‐OR: 2.55; 95% CI: 2.01–3.24), polyvascular disease (two‐territory disease, adj‐OR: 1.89; 95% CI: 1.46–2.44; three‐territory disease, adj‐OR: 2.68; 95% CI: 1.94–3.70), chronic kidney disease (CKD; adj‐OR: 1.65; 95% CI: 1.30–2.11), body mass index (BMI; adj‐OR [per 5 kg/m2]: 1.15; 95% CI: 1.03–1.27), prior myocardial infarction (MI) (adj‐OR: 1.35; 95% CI: 1.03–1.78), and hypertension (adj‐OR: 1.44; 95% CI: 1.02–2.04). Patients who experienced HHF during follow‐up had higher rates of subsequent rehospitalization and death. Vorapaxar did not modify the risk of HHF. Conclusions: In patients with stable atherosclerosis, prior HF, age, T2DM, polyvascular disease, CKD, BMI, prior MI, and hypertension are important predictors of HHF risk. [ABSTRACT FROM AUTHOR]

Factor Xa (FXa) and thrombin exert non-hemostatic cellular actions primarily mediated through protease-activated receptors (PARs). We investigated the effect of FXa and thrombin on human late-outgrowth endothelial cells (OECs), a type of endothelial progenitor cells (EPCs), and on human umbilical vein endothelial cells (HUVECs). The effect of direct oral anticoagulants (DOACs), rivaroxaban and dabigatran, was also studied. The membrane expression of intercellular adhesion molecule-1 (ICAM-1) and the secretion of monocyte chemoattractant protein-1 (MCP-1) were used as cell activation markers. FXa and thrombin increase the ICAM-1 expression and the MCP-1 secretion on both cells, being higher on OECs. Vorapaxar, a specific PAR-1 antagonist, completely inhibits FXa-induced activation of both cells and thrombin-induced HUVEC activation, but only partially thrombin-induced OEC activation. Furthermore, thrombin-receptor activating peptide; TRAP-6, only partially activates OECs. OECs do not membrane-express PAR-4, therefore it may not be involved on thrombin-induced OEC activation. Rivaroxaban and dabigatran inhibit OEC and HUVEC activation by FXa and thrombin, respectively. Rivaroxaban enhances thrombin-induced OEC and HUVEC activation, which is completely inhibited by vorapaxar. The inhibition of OEC and HUVEC activation by vorapaxar and DOACs may represent a new pleiotropic effect of these drugs. The pathophysiological and clinical significance of our findings need to be established.

Kallikrein-related peptidase 6 (KLK6) is a secreted serine protease hypothesized to promote inflammation via cleavage of protease-activated receptor 1 (PAR1) and PAR2. KLK6 levels are elevated in multiple inflammatory and autoimmune conditions, but no definitive role in pathogenesis has been established. Here, we show that skin-targeted overexpression of KLK6 causes generalized, severe psoriasiform dermatitis with spontaneous development of debilitating psoriatic arthritis-like joint disease. The psoriatic skin and joint phenotypes are reversed by normalization of skin KLK6 levels and attenuated following genetic elimination of PAR1 but not PAR2. Conservation of this regulatory pathway was confirmed in human psoriasis using vorapaxar, an FDA-approved PAR1 antagonist, on explanted lesional skin from patients with psoriasis. Beyond defining a critical role for KLK6/PAR1 signaling in promoting psoriasis, our results demonstrate that KLK6/PAR1-mediated inflammation in the skin alone is sufficient to drive inflammatory joint disease. Further, we identify PAR1 as a promising cytokine-independent target in therapy of psoriasis and psoriatic arthritis., Introduction Psoriasis is a chronic, incurable systemic inflammatory disease with complex and incompletely understood pathogenesis. Two percent to 3% of the population worldwide suffers from psoriasis, and affected individuals show [...]

Factor Xa (FXa) and thrombin exert non-hemostatic cellular actions primarily mediated through protease-activated receptors (PARs). We investigated the effect of FXa and thrombin on human late-outgrowth endothelial cells (OECs), a type of endothelial progenitor cells (EPCs), and on human umbilical vein endothelial cells (HUVECs). The effect of direct oral anticoagulants (DOACs), rivaroxaban and dabigatran, was also studied. The membrane expression of intercellular adhesion molecule-1 (ICAM-1) and the secretion of monocyte chemoattractant protein-1 (MCP-1) were used as cell activation markers. FXa and thrombin increase the ICAM-1 expression and the MCP-1 secretion on both cells, being higher on OECs. Vorapaxar, a specific PAR-1 antagonist, completely inhibits FXa-induced activation of both cells and thrombin-induced HUVEC activation, but only partially thrombin-induced OEC activation. Furthermore, thrombin-receptor activating peptide; TRAP-6, only partially activates OECs. OECs do not membrane-express PAR-4, therefore it may not be involved on thrombin-induced OEC activation. Rivaroxaban and dabigatran inhibit OEC and HUVEC activation by FXa and thrombin, respectively. Rivaroxaban enhances thrombin-induced OEC and HUVEC activation, which is completely inhibited by vorapaxar. The inhibition of OEC and HUVEC activation by vorapaxar and DOACs may represent a new pleiotropic effect of these drugs. The pathophysiological and clinical significance of our findings need to be established. [ABSTRACT FROM AUTHOR]

Background Perioperative dual‐antiplatelet therapy for flow diversion limits thromboembolic complications. However, resistance to dual‐antiplatelet therapy medications remains a concern for neuroendovascular intervention. To date, there is no standardized approach for resistance to ADP receptor antagonists. Methods We report a case of ticagrelor resistance for flow diversion of an intracranial aneurysm treated with vorapaxar, as well as a narrative review of the literature for previous cases of ticagrelor resistance. Results Flow diversion with the Pipeline embolization device was deployed for a left internal carotid artery blister aneurysm and bilateral internal carotid artery dissecting pseudoaneurysms. The patient had 3 thromboembolic complications while on dual‐antiplatelet therapy with ticagrelor or prasugrel, leading to transition of antiplatelet therapy to vorapaxar. At 84 days follow‐up, the patient was fully recovered with complete occlusion of the aneurysms. Conclusion Our case suggests that vorapaxar is a promising alternative for patients with ticagrelor resistance in flow diversion–treated intracranial aneurysms. High‐quality randomized controlled trials are needed to elucidate the safety and efficacy of vorapaxar in neuroendovascular procedures.

Panax notoginseng (Burk.) F.H. Chen has long been used to stop bleeding for hundreds of years in China. At present, only dencichine, notoginsenoside Ft1, and 20(S)-protopanaxadiol (PPD) showed hemostatic effect. However, the molecular mechanism of PPD on the platelet aggragetion needs to be further investigated. The study aims to evaluate the hemostatic effect of PPD and reveal its interacting targets using a series of experiments. In this study, the bleeding time was measured in mouse tail amputation and liver scratch models to evaluate hemostatic effect of PPD. The routine blood and plasma coagulation parameters in NS, HC, and PPD (2, 4, and 8 mg/kg) groups were measured using a blood analyzer. Platelet aggregation rate and ATP release were analyzed by a platelet aggregometer. Subsequently, the degranulation marker CD62P and PAC-1, and the concentrations of cytosolic Ca2+ ([Ca2+]i), cAMP, cGMP, and PAC-1 expressions were also assessed. We found that PPD shorted the bleeding time on the mouse tail amputation and liver scratch models and mainly increased blood platelet count in the rats after subcutaneous injection for 4 h. Meanwhile, PPD decreased APTT, increased FIB content, and directly induced platelet aggregation in vitro. In the absence of Ca2+, PPD induced the increase of [Ca2+]i and slightly increased the levels of CD62P and PAC-1. After the addition of 1 mM Ca2+, PPD treatment markedly promoted platelet activation by promoting ATP level, releasing CD62P and increasing PAC-1 binding in washed platelets. Excitingly, PPD-induced changes including platelet aggregation, decreased cAMP content, and the increases of CD62P and PAC-1 were significantly reversed by protease-activated receptor 1 (PAR-1) antagonist, vorapaxar, which showed similar function as thrombin. In addition, molecular docking analysis and ELISA assay demonstrated that PPD had a promising docking score with -6.6 kcal/mol and increased PAR-1 expression in human platelets, which indicated that PAR-1 is involved in PPD-induced platelet aggregation by regulating calcium signaling. Collectively, our study could provide the new insights of PPD as an essential hemostatic ingredient in Panax notoginseng for the treatment of hemorrhagic disease.

Background Vorapaxar as an adjunct to dual antiplatelet therapy (DAPT) reduces thrombotic events in patients with prior myocardial infarction at the expense of increased bleeding. Withdrawal of aspirin has emerged as a bleeding reduction strategy. The pharmacodynamic effects of vorapaxar with potent P2Y12 inhibitors as well as the impact of dropping aspirin is unexplored and represented the aim of the VORA‐PRATIC (Vorapaxar Therapy in Patients With Prior Myocardial Infarction Treated With Newer Generation P2Y12 Receptor Inhibitors Prasugrel and Ticagrelor) study. Methods and Results Post–myocardial infarction patients (n=130) on standard DAPT (aspirin+prasugrel or ticagrelor) were randomized to 1 of 3 arms: (1) triple therapy: aspirin+prasugrel/ticagrelor+vorapaxar; (2) dual therapy (drop aspirin): prasugrel/ticagrelor+vorapaxar; (3) DAPT: aspirin+prasugrel/ticagrelor. Pharmacodynamic assessments were performed at 3 time points (baseline and 7 and 30 days). Vorapaxar reduced CAT (collagen‐ADP‐TRAP)–induced platelet aggregation, a marker of platelet‐mediated global thrombogenicity (triple therapy versus DAPT at 30 days: mean difference=–27; 95% CI,–35 to –19; P

In seeking to improve care in coronary artery disease patients, further platelet inhibition has been occasionally applied beyond that provided by aspirin and a P2Y12 receptor antagonist. This review aims to offer insights about the rationale, the efficacy and safety of combination antiplatelet therapy, involving three or more agents. Overall, the use of glycoprotein (GP) IIb/IIIa inhibitors did not significantly modify the treatment effect of different antiplatelet strategies, including double vs standard clopidogrel, prasugrel vs clopidogrel, ticagrelor vs clopidogrel, cangrelor vs clopidogrel, and vorapaxar vs placebo. With the caveat that the use of GP IIb/IIIa inhibitor was not randomized, adding such an agent to aspirin and a P2Y12 receptor antagonist appears to carry a significantly increased bleeding potential. Moreover, adding vorapaxar to aspirin- and clopidogrel-treated patients is associated with more bleeding events, while the bleeding potential is further exacerbated in cases of quadruplicate antiplatelet treatment including aspirin, clopidogrel, vorapaxar, and a GP IIb/IIIa inhibitor. In ST-segment elevation, myocardial infarction patients’ administration of an intravenous antiplatelet agent (GP IIb/IIIa inhibitor or cangrelor), in addition to aspirin and a P2Y12 receptor antagonist, efficiently bridges the pharmacodynamic gap of oral agents. Cilostazol on top of aspirin and clopidogrel appears to be safe, although of questionable clinical benefit. In conclusion, combination antiplatelet therapy should be reserved only for selected cases and following thoughtful consideration of the associated risk/benefit ratio.

Panax notoginseng (Burk.) F.H. Chen has long been used to stop bleeding for hundreds of years in China. At present, only dencichine, notoginsenoside Ft1, and 20(S)-protopanaxadiol (PPD) showed hemostatic effect. However, the molecular mechanism of PPD on the platelet aggragetion needs to be further investigated. The study aims to evaluate the hemostatic effect of PPD and reveal its interacting targets using a series of experiments. In this study, the bleeding time was measured in mouse tail amputation and liver scratch models to evaluate hemostatic effect of PPD. The routine blood and plasma coagulation parameters in NS, HC, and PPD (2, 4, and 8 mg/kg) groups were measured using a blood analyzer. Platelet aggregation rate and ATP release were analyzed by a platelet aggregometer. Subsequently, the degranulation marker CD62P and PAC-1, and the concentrations of cytosolic Ca2+ ([Ca2+]i), cAMP, cGMP, and PAC-1 expressions were also assessed. We found that PPD shorted the bleeding time on the mouse tail amputation and liver scratch models and mainly increased blood platelet count in the rats after subcutaneous injection for 4 h. Meanwhile, PPD decreased APTT, increased FIB content, and directly induced platelet aggregation in vitro. In the absence of Ca2+, PPD induced the increase of [Ca2+]i and slightly increased the levels of CD62P and PAC-1. After the addition of 1 mM Ca2+, PPD treatment markedly promoted platelet activation by promoting ATP level, releasing CD62P and increasing PAC-1 binding in washed platelets. Excitingly, PPD-induced changes including platelet aggregation, decreased cAMP content, and the increases of CD62P and PAC-1 were significantly reversed by protease-activated receptor 1 (PAR-1) antagonist, vorapaxar, which showed similar function as thrombin. In addition, molecular docking analysis and ELISA assay demonstrated that PPD had a promising docking score with -6.6 kcal/mol and increased PAR-1 expression in human platelets, which indicated that PAR-1 is involved in PPD-induced platelet aggregation by regulating calcium signaling. Collectively, our study could provide the new insights of PPD as an essential hemostatic ingredient in Panax notoginseng for the treatment of hemorrhagic disease. [ABSTRACT FROM AUTHOR]

Vorapaxar specifically and effectively inhibits protease activated receptor-1 and may reduce thrombin-mediated ischemic events without interfering primary hemostasis. In the TRA-2P-TIMI 50 trial, vorapaxar reduced the risk of primary ischemic outcome but with increased bleeding risk. In the post hoc analysis, in patients with a history of myocardial infarction, peripheral artery disease, the net clinical outcome favored vorapaxar therapy with 10% reduction in cardiovascular death, myocardial infarction, stroke, urgent coronary revascularization and moderate or severe bleeding. Based on these favorable results, vorapaxar was approved for the reduction of thrombotic cardiovascular events in patients with prior myocardial infarction or with peripheral artery disease on top of standard antiplatelet therapy. A careful patient selection is needed to balance efficacy versus safety. [ABSTRACT FROM AUTHOR]

Beta 2 glycoprotein I (β2GPI) is a major antigen for autoantibodies present in antiphospholipid antibody syndrome (APS). β2GPI is a single polypeptide with five repeated domains and different conformations. The activated J-shaped conformation of β2GPI binds to negatively charged phospholipids in the membrane via the fifth domain and causes blood clotting reactions. We applied a drug repurposing strategy using virtual screening and molecular dynamics to find the best FDA drugs against the fifth domain of β2GPI. In the first phase, FDA drugs that had the most favorable ΔG with the fifth domain of β2GPI were selected by virtual screening. Among these drugs that had the most favorable ΔG, Vorapaxar and Antrafenine were selected for molecular dynamics (MD) simulation studies. MD simulation was performed to evaluate the stability of Vorapaxar and Antrafenine complexes and the effect of the two drugs on protein conformation. Also, MD simulation was done to investigate the effect of Antrafenine and Vorapaxar on the binding of β2GPI to the platelet model membrane. According to the results, Vorapaxar and Antrafenine were bound to the protein with the favorable binding energy (Vorapaxar and Antrafenine binding energies are − 49.641 and − 38.803 kcal/mol, respectively). In this study, it was shown that unlike protein alone and protein in the Antrafenine complex, the protein in the Vorapaxar complex was completely separated from the model membrane after 350 ns. Moreover, Vorapaxar led to more changes in the activated J-shape of β2GPI. Thus, Vorapaxar can be a suitable candidate for further investigations on the treatment of APS. [ABSTRACT FROM AUTHOR]

Thrombin is the most potent agonist of human platelets and its effects are primarily mediated through the protease-activated receptors (PARs)-1 and -4. Although PAR-1 has higher affinity for thrombin than PAR-4, both receptors contribute to thrombin-mediated actions on platelets. Recently, a potent and selective PAR-1 antagonist (vorapaxar) was approved for clinical use in selected patients. In contrast, despite the fact that several PAR-4 antagonists have been developed, few of them have been tested in clinical trials. The aim of the present study was to elucidate the molecular requirements involving the PAR-4 mechanism of activation by peptide analogues of its tethered-ligand. Eight synthetic PAR-4 tethered-ligand peptide analogues were synthesized and studied for their agonistic/antagonistic potency and selectivity toward human washed platelet aggregation, using light transmittance aggregometry. In addition, in silico studies were conducted to describe the receptor–peptide interactions that are developed following PAR-4 exposure to the above analogues. To provide a first structure-activity relationship rationale on the bioactivity profiles recorded for the studied analogues, molecular docking was applied in a homology model of PAR-4, derived using the crystal structure of PAR-1. The following peptide analogues were synthesized: AYPGKF-NH2 (1), GYPGKF-NH2 (2), Ac-AYPGKF-NH2 (3), trans-cinnamoyl-AYPGKF-NH2 (4), YPGKF-NH2 (5), Ac-YPGKF-NH2 (6), trans-cinnamoyl-YPGKF-NH2 (7), and caffeoyl-YPGKF-NH2 (8). Peptide (1) is a selective PAR-4 agonist inducing platelet aggregation with an IC50 value of 26.2 μM. Substitution of Ala-1 with Gly-1 resulted in peptide (2), which significantly reduces the agonistic potency of peptide (1) by 25-fold. Importantly, substitution of Ala-1 with trans-cinnamoyl-1 resulted in peptide (7), which completely abolishes the agonistic activity of peptide (1) and renders it with a potent antagonistic activity toward peptide (1)-induced platelet aggregation. All other peptides tested were inactive. Tyr-2, residue, along with its neighboring environment was a key determinant in the PAR-4 recognition mode. When the neighboring residues to Tyr-2 provided an optimum spatial ability for the ligand to enter into the binding site of the transmembrane receptor, a biological response was propagated. These results were compared with the predicted binding poses of small molecule antagonists of PAR-4, denoted as YD-3, ML-354, and BMS-986120. π–π stacking interaction with Tyr-183 appears to be critical and common for both small molecules antagonists and the peptide trans-cinnamoyl-YPGKF-NH2. Conclusively, the lipophilicity, size, and aromatic nature of the residue preceding Tyr-2 are determining factors on whether a human platelet PAR-4 tethered-ligand peptide analogue will exert an agonistic or antagonistic activity.

In response to the high prevalence of atherothrombotic diseases and the residual risks left by the current antiplatelet therapies, the Food and Drug Administration approved the use of vorapaxar as a secondary prevention of cardiovascular events. Vorapaxar is a novel oral antiplatelet agent that antagonizes protease-activated receptor-1 and inhibits platelet activation without influencing coagulation parameters. In this review, we summarized findings of the main studies and the subanalyses from two pivotal phase III clinical trials of vorapaxar, as well as the results of the available observational studies to assist treatment decision-making of vorapaxar for clinicians. Evidence shows that vorapaxar treatment brings favorable results to patients with myocardial infraction history, peripheral arterial diseases, and acute coronary syndrome and those who underwent coronary artery bypass grafting surgery. Studies supported the efficacy of vorapaxar in treating incident coronary stent thrombosis, acute limb ischemia, and peripheral revascularization which outweighed the safety concern of bleeding. However, vorapaxar should not be administered to patients with prior stroke or transient ischemic attack due to excessive risks of bleeding. Future studies should focus on examining the long-term risks and benefits of vorapaxar on single cardiovascular outcomes and the optimal dosage of vorapaxar for different patient populations.

The review presents the main physiological functions of thrombin. The procoagulant and anticoagulant activities of the key serine protease are discussed in both physiological and pathological conditions of hemostasis. The involvement of thrombin in atherogenesis, as well as its role as a mediator of vascular dysfunction and inflammation in both the peripheral and central nervous system, is highlighted. A pronounced imbalance between the pro- and anticoagulant systems leads to an increase in thrombin formation and creates conditions for the development of thrombosis. Tests that allow direct or indirect assessment of thrombin's functional activity are presented. The potential applications of direct thrombin inhibitors and direct blockers of thrombin PAR receptors in vascular neurology are also considered.

Background Vorapaxar, a protease‐activated receptor‐1 antagonist, is approved for secondary prevention of cardiovascular events but is associated with increased intracranial hemorrhage. Methods and Results TRACER (Thrombin Receptor Antagonist for Clinical Event Reduction in Acute Coronary Syndrome) was a trial of vorapaxar versus placebo among patients with acute coronary syndrome. Strokes were adjudicated by a central events committee. Of 12 944 patients, 199 (1.5%) had ≥1 stroke during the study period (median follow‐up, 477 days). Four patients had a single stroke of unknown type; 195 patients had ≥1 stroke classified as hemorrhagic or nonhemorrhagic (165 nonhemorrhagic, 28 hemorrhagic, and 2 both). Strokes occurred in 96 of 6473 patients (1.5%) assigned vorapaxar and 103 of 6471 patients (1.6%) assigned placebo. Kaplan‐Meier incidence of stroke for vorapaxar versus placebo was higher for hemorrhagic stroke (0.45% versus 0.14% [hazard ratio, 2.74; 95% confidence interval, 1.22–6.15]), lower but not significantly different for nonhemorrhagic stroke (1.53% versus 1.98% at 2 years [hazard ratio, 0.79; 95% confidence interval, 0.58–1.07]), and similar for stroke overall (1.93% versus 2.13% at 2 years [hazard ratio, 0.94; 95% confidence interval, 0.71–1.24]). Conclusions Stroke occurred in

Vorapaxar-dependent protease-activated receptor (PAR)-1 inhibition diminishes diabetic nephropathy in experimental type 1 diabetes. As most patients with diabetic nephropathy suffer from type 2 diabetes, the aim of this study was to investigate whether PAR-1 inhibition also limits diabetic nephropathy in experimental type 2 diabetes. Consequently, leptin-deficient black and tan brachyuric (BTBRob/ob) mice were randomly assigned to vorapaxar (1.75 mg/kg; twice weekly via oral gavage) or vehicle treatment, whereas matched wild-type (WT) BTBR (BTBRWT) mice served as nondiabetic controls. Weight and (nonfasting) blood glucose levels were monitored for up to 18 wk, after which kidney function and histologic damage was evaluated postmortem. We show that blood glucose levels and body weight increased in diabetic BTBRob/ob mice compared with nondiabetic BTBRWT controls. Vorapaxar-dependent PAR-1 inhibition reduced but did not normalize blood glucose levels in BTBRob/ob mice, whereas it potentiated the increase in body weight. Vorapaxar did not, however, preserve kidney function, whereas it only minimally reduced histopathological signs of kidney injury. Overall, we thus show that PAR-1 inhibition reduces blood glucose levels during the progression of diabetic nephropathy in experimental type 2 diabetes but does not improve renal function. This is in contrast to the therapeutic potential of vorapaxar in type 1 diabetes-induced nephropathy, highlighting the importance of disease-dependent treatment modalities. [ABSTRACT FROM AUTHOR]

Atherosclerosis (AS) is an inflammatory disease that occurs in the arterial wall and is characterized by progressive lipid accumulation within the intima of large arteries, leading to the dysfunction of endothelial cells and further destruction of the endothelial barrier and vascular tone. Arterial intima injury accelerates the adhesion and activation of platelets at the injury site. The activation of platelets results in the secretion of growth factors, leading to the migration and proliferation of vascular smooth muscle cells (VSMCs), promoting the formation of plaque, resulting in the formation of thrombus. The present study found that vorapaxar could alleviate the inflammatory response induced by a high concentration of cholesterol stimulation and increase the release of nitric oxide (NO) via the protein kinase B (AKT) signaling pathway and regulation of the intracellular concentration of Ca2+ ([Ca2+]i). We also found that vorapaxar could reduce the damage of DNA caused by cholesterol stimulation and regulate the cell cycle via the AKT/JNK signaling pathway and its downstream molecules glycogen synthase kinase 3β (GSK-3β) and connexin 43, maintaining the integrity of the endothelial barrier and proliferation of endothelial cells, serving a protective role in endothelial cells. [ABSTRACT FROM AUTHOR]

Patients with renal disease are often undertreated with antiplatelet therapy due to concerns about bleeding. Vorapaxar blocks platelet activation via the PAR-1 receptor and reduces cardiovascular events in patients with stable atherosclerosis, but with increased bleeding. We examined the efficacy and safety of vorapaxar in patients with impaired renal function. TRA2°P-TIMI 50 randomized patients with stable atherosclerosis to vorapaxar or. We analyzed patients with eGFR assessed who qualified with a history of MI or PAD (without stroke or TIA) (n = 19,932). Cox models assessed the risk of CV events and bleeding by quartile of baseline eGFR in the placebo arm and then by randomized assignment. Net clinical outcome (NCO) was predefined as CV death, MI, stroke, or GUSTO severe bleeding. Patients with lower eGFR tended to be older, female, have hypertension, hyperlipidemia or prior PAD. In the placebo arm, baseline eGFR in the lowest quartile was associated with a 26% higher risk of CV death, MI or stroke (Q1:Q4 HRadj 1.26, 1.03–1.55) and 73% higher risk of GUSTO moderate or severe bleeding (HRadj 1.73, 1.12–2.65). Vorapaxar reduced the risk of MACE to a similar extent (14–26%) across quartiles of baseline eGFR (P interaction = 0.70) and increased the relative risk of GUSTO moderate or severe bleeding (P interaction = 0.54). NCO was similar across quartiles of eGFR (P interaction = 0.65). Intensification of antiplatelet therapy with vorapaxar offers comparable net clinical benefit regardless of baseline renal function. These data support the use of more potent antiplatelet regimens in patients with renal dysfunction. [ABSTRACT FROM AUTHOR]

Judy WM Cheng Department of Pharmacy Practice, MCPHS University, Boston, MA, USA Abstract: This article reviews the pharmacology, clinical efficacy, and safety of vorapaxar in reducing cardiovascular risk. Vorapaxar is a tricyclic himbacine-derived reversible inhibitor of platelet surface protease activator receptor-1, which prevents thrombin from activating platelets. Two Phase III clinical trials and multiple subanalyses from the two trials with vorapaxar have been published. In patients with recent acute coronary syndrome, vorapaxar, when added to standard therapy, did not reduce the composite cardiovascular end point. In contrary, in a study of secondary prevention for patients with cardiovascular diseases, vorapaxar reduced the risk of cardiovascular death or ischemic events (myocardial infarction, stroke) in patients with stable atherosclerosis who were receiving standard therapy. Vorapaxar is approved in the US for use with aspirin and/or clopidogrel in the secondary prevention of thrombogenic cardiovascular events in stable patients with peripheral arterial disease or a history of myocardial infarction. Vorapaxar increases risk of bleeding and is contraindicated in patients with previous cerebrovascular events. It is essential to balance individual patient’s bleeding risk to any further cardiovascular benefits that they may get. Future investigation is also needed to evaluate use of vorapaxar with newer antiplatelet agents such as ticagrelor and cangrelor, as well as its role as monotherapy. Keywords: vorapaxar, protease activator receptor-1 antagonist, atherosclerotic disease

2015 ESC Guidelines for the management of acute coronary syndromes in patients presenting without persistent ST-segment elevation.

Patients receiving therapy for the secondary prevention of myocardial infarction (MI) are still at high risk of a major cardiovascular event or death despite the use of currently available treatment strategy. Vorapaxar, an oral protease-activated receptor antagonist, is a novel antiplatelet drug that has been recently approved to provide further risk reduction. The results of two Phase III trials (thrombin receptor antagonists for clinical event reduction and the TRA 2 °P-TIMI 50) have showed that vorapaxar, in addition to standard of care therapy, has the potential to provide further risk reduction in patients with prior MI. A search was made on PubMed on articles related to clinical trials and clinical consideration with the use of vorapaxar. This review article summarizes the results of Phase II trials, Phase III trials, subgroup analysis, precautions, and drug interaction with the use of vorapaxar.

Platelet protease-activated receptor 1 (PAR1) is a cell surface G-protein-coupled receptor (GPCR) that acts as a thrombin receptor promoting platelet aggregation. Targeting the PAR1 pathway by vorapaxar, a PAR1 antagonist, leads to a reduction in ischemic events in cardiovascular patients with a history of myocardial infarction or with peripheral arterial disease. In platelets, specialized microdomains highly enriched in cholesterol act as modulators of the activity of several GPCRs and play a pivotal role in the signaling pathway. However, their involvement in platelet PAR1 function remains incompletely characterized. In this context, we aimed to investigate whether activation of PAR1 in human platelets requires its localization in the membrane cholesterol-rich microdomains. Using confocal microscopy, biochemical isolation, and proteomics approaches, we found that PAR1 was not localized in cholesterol-rich microdomains in resting platelets, and only a small fraction of the receptor relocated to the microdomains following its activation. Vorapaxar treatment increased the level of PAR1 at the platelet surface, possibly by reducing its endocytosis, while its colocalization with cholesterol-rich microdomains remained weak. Consistent with a cholesterol-dependent activation of Akt and p38 MAP kinase in thrombin receptor-activating peptide (TRAP)-activated platelets, the proteomic data of cholesterol-rich microdomains isolated from TRAP-activated platelets showed the recruitment of proteins contributing to these signaling pathways. In conclusion, contrary to endothelial cells, we found that PAR1 was only weakly present in cholesterol-rich microdomains in human platelets but used these microdomains for efficient activation of downstream signaling pathways following TRAP activation.

Abstract Objective The anti-cancer anthracycline drug Doxorubicin (Dox) causes cardiotoxicity. We investigated the role of protease-activated receptor 1 (PAR-1) in Dox-induced cardiotoxicity. Methods and results In vitro experiments revealed that PAR-1 enhanced Dox-induced mitochondrial dysfunction, reactive oxygen species and cell death of cardiac myocytes and cardiac fibroblasts. The contribution of PAR-1 to Dox-induced cardiotoxicity was investigated by subjecting PAR-1−/− mice and PAR-1+/+ mice to acute and chronic exposure to Dox. Heart function was measured by echocardiography. PAR-1−/− mice exhibited significant less cardiac injury and dysfunction compared to PAR-1+/+ mice after acute and chronic Dox administration. PAR-1−/− mice had reduced levels of nitrotyrosine, apoptosis and inflammation in their heart compared to PAR-1+/+ mice. Furthermore, inhibition of PAR-1 in wild-type mice with vorapaxar significantly reduced the acute Dox-induced cardiotoxicity. Conclusion Our results indicate that activation of PAR-1 contributes to Dox-induced cardiotoxicity. Inhibition of PAR-1 may be a new approach to reduce Dox-induced cardiotoxicity in cancer patients. Highlights • Protease-activated receptor 1 (PAR-1) contributes to doxorubicin cardiotoxicity. • PAR-1 activation increases doxorubicin-induced oxidative stress and apoptosis. • PAR-1 activation enhances doxorubicin-mediated cell death of cardiac cells. • PAR-1−/−mice are protected against doxorubicin-induced cardiotoxicity. • Vorapaxar protects against doxorubicin-induced heart failure. [ABSTRACT FROM AUTHOR]