Prasugrel: A Novel Thienopyridine Antiplatelet Agent. A Review of Preclinical and Clinical Studies and the Mechanistic Basis for Its Distinct Antiplatelet Profile

Antiplatelet strategies: past, present, and future

Antiplatelet therapy plays a critical role in the prevention and treatment of major cardiovascular diseases triggered by thrombosis. Since the 1900s, significant progress in reducing morbidity and death caused by cardiovascular diseases has been made. However, despite the development and approval of drugs that specifically target the platelet, including inhibitors for cycloxygenase-1, P2Y12 receptor, integrin αIIbβ3, phosphodiesterases, and protease-activated receptor 1, the risk of recurrent thrombotic events remains high, and the increased risk of bleeding is a major concern. Scientific advances in our understanding of the role of platelets in haemostasis and thrombosis have revealed novel targets, such as protease-activated receptor 4 (PAR4), glycoprotein Ib (GPIb)-V-IX complex, glycoprotein VI, and 12-lipoxygenase. The antithrombotic effects and safety of the pharmacologic inhibition of these targets are currently under investigation in clinical studies. This review provides an overview of drugs in early development to target the platelet and those in current use in clinical practice. Furthermore, it describes the emerging drug targets being developed and studied to reduce platelet activity and outlines potential novel therapeutic targets in the platelet.

Safety and efficacy of tailored antiplatelet therapy using prasugrel or ticagrelor based on clopidogrel responsiveness in endovascular treatment for intracranial aneurysms: a meta-analysis

BACKGROUND

Clopidogrel (CPG)-based dual antiplatelet therapy (DAPT) in combination with aspirin has been widely used before endovascular procedures for intracranial aneurysms to prevent procedural thromboembolic complication (TEC). However, the main drawback of CPG is the high proportion of hyporesponders. This study sought to investigate the usefulness of tailored DAPT using novel P2Y12 inhibitors (prasugrel or ticagrelor, (PSG/TCG)) guided by a platelet reactivity test (PRT), compared with CPG-based conventional DAPT.

METHOD

Data were extracted from PubMed, Embase, and Cochrane Central Register of Controlled Trials by two independent reviewers. A random effects model was used to investigate the procedural TEC and hemorrhagic complications (HEC) of the tailored DAPT and conventional therapy by risk ratios (RR) and 95% confidence intervals (95% CI). Additionally, we performed subgroup analyses to directly compare prasugrel/ticagrelor with CPG.

RESULTS

Six studies comprising 2557 patients were included in the analysis. Compared with conventional non-tailored therapy, PRT-guided tailored DAPT with PSG/TCG was associated with a lower risk of TEC (RR 0.40, 95% CI 0.22 to 0.74, P=0.004) without increasing HEC rates. The subgroup analysis showed that the switch to PSG/TCG in CPG hyporesponders was related to a lower incidence of TEC (RR 0.46, 95% CI 0.23 to 0.95, P=0.03) without a difference in HEC, compared with maintenance of CPG in CPG responders.

CONCLUSION

Evidence from this analysis supports PRT-guided tailored DAPT (using PSG/TCG) as a better choice for preparation towards endovascular procedures to treat aneurysms. Furthermore, it suggests that PSG/TCG is not limited to the role of a substitute for CPG but may be a first-line agent for DAPT.

The developmental journey of therapies targeting purine receptors: from basic science to clinical trials

Since the discovery of ATP as an extracellular signalling molecule in 1972, purinergic signalling, mediated by extracellular purines and pyrimidines has been identified in virtually all mammalian tissues and is implicated in regulating fundamental cellular processes. In recent years, there has been an increasing focus on the pathophysiology and potential therapeutic interventions based on purinergic signalling. A vast range of compounds targeting purine receptors are in clinical development, and many more are in preclinical studies, which highlights the fast growth in this research field. As a tribute to Professor Geoffrey Burnstock's legacy in purinergic signalling, we present here a brief review of compounds targeting purine receptors that are in different stages of clinical trials. The review highlights the 50-year journey from basic research on purinergic receptors to clinical applications of therapies targeting purine receptors.

P2Y12 Antagonists in Cardiovascular Disease—Finding the Best Balance Between Preventing Ischemic Events and Causing Bleeding

Dual antiplatelet therapy comprising of aspirin and oral P2Y₁₂ receptor antagonists are an established cornerstone of therapy in acute coronary syndromes and percutaneous coronary intervention. As a result, the platelet P2Y₁₂ receptor remains a key therapeutic target in cardiovascular medicine since pharmacological antagonists were first developed in the 1990’s. With a greater understanding of platelet biology and the role played by the P2Y₁₂ receptor in the amplification of platelet activation and thrombus formation, there has been progressive refinement in the development of P2Y₁₂ receptor antagonists with greater potency and consistency of antiplatelet effect. However, challenges remain in the utilization of these agents particularly in balancing the need for greater protection from ischemic events whilst minimizing the bleeding risk and present a real opportunity for the institution of individualized medicine. Future drug developments will provide clinicians with greater avenues to achieve this.

Ticagrelor resistance: a case series and algorithm for management of non-responders

The placement of cervical and intracranial stents requires the administration of antiplatelet drugs to prevent thromboembolic complications. Ticagrelor has emerged as the most widely used alternative in clopidogrel non-responders owing to its potent antiplatelet effects. Because ticagrelor does not require hepatic activation, many neurointerventionalists choose to forgo laboratory testing of platelet inhibition. In rare instances, patients may not achieve adequate platelet inhibition following ticagrelor administration. In this paper we review the mechanism of action of ticagrelor and its use in cerebrovascular procedures. We present two cases of ticagrelor non-responsiveness from two high-volume cerebrovascular centers, discuss their management, and propose an algorithm for managing ticagrelor non-responsiveness.

Effects of clopidogrel vs. prasugrel vs. ticagrelor on endothelial function, inflammatory parameters, and platelet function in patients with acute coronary syndrome undergoing coronary artery stenting: a randomized, blinded, parallel study

AIMS

In a randomized, parallel, blinded study, we investigate the impact of clopidogrel, prasugrel, or ticagrelor on peripheral endothelial function in patients undergoing stenting for an acute coronary syndrome.

METHODS AND RESULTS

The primary endpoint of the study was the change in endothelium-dependent flow-mediated dilation (FMD) following stenting. A total of 90 patients (age 62 ± 9 years, 81 males, 22 diabetics, 49 non-ST elevation myocardial infarctions) were enrolled. There were no significant differences among groups in any clinical parameter. Acutely before stenting, all three drugs improved FMD without differences between groups (P = 0.73). Stenting blunted FMD in the clopidogrel and ticagrelor group (both P < 0.01), but not in the prasugrel group. During follow-up, prasugrel was superior to clopidogrel [mean difference 2.13, 95% confidence interval (CI) 0.68-3.58; P = 0.0047] and ticagrelor (mean difference 1.57, 95% CI 0.31-2.83; P = 0.0155), but this difference was limited to patients who received the study therapy 2 h before stenting. Ticagrelor was not significantly superior to clopidogrel (mean difference 0.55, 95% CI -0.73 to 1.82; P = 0.39). No significant differences were seen among groups for low-flow-mediated dilation. Plasma interleukin (IL)-6 (P = 0.02 and P = 0.01, respectively) and platelet aggregation reactivity in response to adenosine diphosphate (P = 0.002 and P = 0.035) were lower in the prasugrel compared to clopidogrel and ticagrelor group.

CONCLUSION

As compared to ticagrelor and clopidogrel, therapy with prasugrel in patients undergoing stenting for an acute coronary syndrome is associated with improved endothelial function, stronger platelet inhibition, and reduced IL-6 levels, all of which may have prognostic implications. This effect was lost in patients who received the study medication immediately after stenting.

EUDRACT-NO

2011-005305-73.

The Total Thrombus Formation (T-TAS) platelet (PL) assay, a novel test that evaluates whole blood platelet thrombus formation under physiological conditions

Dual antiplatelet therapy (DAPT, aspirin, and a P2Y₁₂ inhibitor) reduces thrombotic events in patients with coronary artery disease (CAD). The T-TAS PL assay uses arterial shear flow over collagen surface, better mimicking in vivo conditions compared to conventional agonist-based platelet function assays, to evaluate platelet function. Here, the platelet function in patients taking DAPT is evaluated with the T-TAS PL assay. In 57 patients with CAD, taking DAPT ≥7 days (n = 22 for clopidogrel, n = 15 for prasugrel, n = 20 for ticagrelor), T-TAS PL assessments were performed in duplicate, and expressed as area under the flow pressure curve within a 10-minute period (AUC10). The duplicate measurements were strongly correlated (r = 0.90, p < .001), with an intra-assay coefficient of variation (CV) of 11,5%. For clopidogrel, the median AUC10 was 11.5 (IQR5.9-41.8), for prasugrel 28.8 (IQR10.3-37.6), and for ticagrelor 8.9 (IQR 6.4-10.9). All measurements were below the AUC10 cutoff of 260 measured in healthy volunteers, suggesting excellent discrimination of DAPT-treated and untreated persons. The new T-TAS PL assay demonstrated complete discrimination of platelet function in patients on DAPT based on an established cutoff. Ticagrelor showed lower levels of platelet function and a more uniform response compared to prasugrel and clopidogrel.

Intravascular hemolysis triggers ADP-mediated generation of platelet-rich thrombi in precapillary pulmonary arterioles

Patients with hereditary or acquired hemolytic anemias have a high risk of developing in situ thrombosis of the pulmonary vasculature. While pulmonary thrombosis is a major morbidity associated with hemolytic disorders, the etiological mechanism underlying hemolysis-induced pulmonary thrombosis remains largely unknown. Here, we use intravital lung microscopy in mice to assess the pathogenesis of pulmonary thrombosis following deionized water-induced acute intravascular hemolysis. Acute hemolysis triggered the development of αIIbβ3-dependent platelet-rich thrombi in precapillary pulmonary arterioles, which led to the transient impairment of pulmonary blood flow. The hemolysis-induced pulmonary thrombosis was phenocopied with intravascular ADP- but not thrombin-triggered pulmonary thrombosis. Consistent with a mechanism involving ADP release from hemolyzing erythrocytes, the inhibition of platelet P2Y12 purinergic receptor signaling attenuated pulmonary thrombosis and rescued blood flow in the pulmonary arterioles of mice following intravascular hemolysis. These findings are the first in vivo studies to our knowledge to suggest that acute intravascular hemolysis promotes ADP-dependent platelet activation, leading to thrombosis in the precapillary pulmonary arterioles, and that thrombin generation most likely does not play a significant role in the pathogenesis of acute hemolysis-triggered pulmonary thrombosis.

Prasugrel in the treatment of acute coronary syndrome

Dual antiplatelet therapy is the mainstay therapy in patients with acute coronary syndrome. The combination of aspirin and a P2Y12 inhibitor in patients who receive a coronary stent reduces the rate of stent thrombosis and the rates of major adverse cardiovascular events. The newer P2Y12 inhibitors (prasugrel and ticagrelor) have better efficacy than clopidogrel. Prasugrel provides greater inhibition of platelet aggregation and has a rapid onset of action. Current acute coronary syndrome guidelines recommend the use of both newer P2Y12 inhibitors. However, emerging data have shown that prasugrel is more efficient than ticagrelor in reducing the incidence of nonfatal myocardial infarction, stroke or cardiovascular death, without increased risk of major bleeding.

Clopidogrel or prasugrel reduces mortality and lessens cardiovascular damage from acute myocardial infarction in hypercholesterolemic male rats

AIMS

Hypercholesterolemia is a hazard for increasing susceptibility of the heart to myocardial infarction (MI) by inducing platelet hyperaggregability. Clopidogrel and prasugrel have documented cardioprotective effects in clinical studies. Herein, we investigated whether clopidogrel and prasugrel could protect against isoproterenol-induced acute MI (A-MI) under hypercholesterolemic conditions in rats.

MAIN METHODS

Dietary hypercholesterolemic rats were subjected to acute doses of isoproterenol. Serum lipids, inflammatory markers, aortic endothelin1 and endothelial nitric oxide synthase (eNOS) mRNAs expression and immunexpression of BCL2 were determined.

KEY FINDINGS

Hypercholesterolemic rats showed infiltration of inflammatory cells and reduction in aortic wall thickness, deposition of fibrous tissue between cardiac muscle fibers. Protective doses of prasugrel or clopidogrel for 28 days before A-MI increased survival, amended the ECG parameters -including ST segment elevation- and improved the histopathological picture in hypercholesterolemic rats. This was coupled with reductions in platelet aggregation, creatine kinase-MB activity, endothelin 1, systemic inflammation and cardiac lipid peroxidation and increment in aortic eNOS expression. Clopidogrel and prasugrel groups showed enhanced BCL2 expression in cardiac fibers and aortic wall.

SIGNIFICANCE

Prasugrel and clopidogrel protected against A-MI via anti-aggregatory and anti-inflammatory effects. These results add to the value of these drugs in correcting cardiovascular dysfunction in patients vulnerable to A-MI after confirmation by appropriate human studies.

[Atherothrombosis : Novel therapeutic strategies]

Despite intensive scientific research over the past decades, atherosclerosis and atherothrombosis are the leading cause of mortality worldwide. During the recent past it has become clear that atherosclerosis is not merely a lipid-driven disease but a multifactorial process involving chronic inflammation of large arteries. This review article briefly outlines the mechanistic nature of atherosclerosis, presents a synopsis of the current state of the art treatment strategies and finally outlines several therapeutic options, which are in clinical and experimental testing.

Population Pharmacokinetic and Exposure-Response Analyses of Prasugrel in Pediatric Patients with Sickle Cell Anemia

BACKGROUND AND OBJECTIVE

Prasugrel, a P2Y₁₂ adenosine diphosphate (ADP) receptor antagonist, inhibits ADP-mediated platelet activation and aggregation in patients with sickle cell anemia (SCA). We developed a population pharmacokinetic (popPK) model in pediatric patients from 2 to <18 years of age with SCA, and performed exposure-response evaluations to characterize the effects of prasugrel in a subset of these patients who weighed 19 kg or more and experienced at least two episodes of vaso-occlusive crises (VOC) in the past year.

METHODS

A three-compartment popPK model adapted from that used in adults with acute coronary syndrome was used to describe the relationship between plasma concentrations of prasugrel's active metabolite (Pras-AM) and time using data from phase II and III clinical studies in children. A VOC event rate model was developed from the phase III study to explore the exposure-response relationship between Pras-AM exposure and VOC, and included evaluation of covariates.

RESULTS

The final popPK model for children with SCA provided a reasonable fit to Pras-AM plasma concentrations over time, with estimates of apparent clearance (CL/F) (172 L/h) and apparent volume of distribution (Vd/F) (51.7 L) that were comparable to previous studies in adults. The final model included weight as a covariate on both CL/F and Vd/F, and age as a covariate on CL/F. Analyses of safety (bleeding events requiring medical intervention) and efficacy (VOC event rate) variables showed no apparent relationship to model-predicted Pras-AM exposure quartiles, and no statistically significant effects of intrinsic or extrinsic factors on the VOC event rate were identified in the VOC event rate model. The effect of post hoc exposures on the VOC event rate did not reach statistical significance.

CONCLUSIONS

A popPK model was developed that provided reasonable parameter estimates, goodness-of-fit diagnostics, and visual predictive checks when applied to Pras-AM plasma concentrations in pediatric patients with SCA. Post hoc exposures obtained from this model did not correlate with measures of VOC or bleeding events in this population.

Outcomes Among Clopidogrel, Prasugrel, and Ticagrelor in ST-Elevation Myocardial Infarction Patients Who Underwent Primary Percutaneous Coronary Intervention From the TOTAL Trial

BACKGROUND

Robust comparisons between oral P2Y12 inhibitors (clopidogrel, prasugrel, ticagrelor) in ST-elevation myocardial infarction (STEMI) patients who undergo primary percutaneous coronary intervention are lacking. We sought to evaluate outcomes on the basis of P2Y12 inhibitor therapy in patients from the Thrombectomy With PCI Versus PCI Alone in Patients With STEMI Undergoing Primary PCI (TOTAL) trial.

METHODS

We grouped 9932 patients according to P2Y12 inhibitor at hospital discharge: clopidogrel (n = 6500; 65.5%), prasugrel (n = 1244; 12.5%), or ticagrelor (n = 2188; 22.0%). The primary composite end point of cardiovascular death, recurrent myocardial infarction, cardiogenic shock, or New York Heart Association class IV heart failure was examined at 1 year. Secondary efficacy and safety end points were also assessed. Cox proportional hazard ratios were determined and adjusted for confounders via propensity scoring.

RESULTS

Baseline characteristics differing between the 3 groups were mainly age 75 years or older, diabetes, and previous stroke. After adjustment, ticagrelor use was associated with a lower rate of the primary composite outcome compared with clopidogrel (adjusted hazard ratio [aHR], 0.72; 95% confidence interval [CI], 0.57-0.91; P < 0.02) and prasugrel (aHR, 0.65; 95% CI, 0.48-0.89; P = 0.02). Prasugrel use was not associated with a lower rate of the primary outcome compared with clopidogrel (aHR, 1.09; 95% CI, 0.86-1.39; P > 0.99). Neither prasugrel nor ticagrelor were associated with increased risk of stroke compared with clopidogrel. Compared with clopidogrel, ticagrelor was associated with significantly lower rates of major bleeding.

CONCLUSIONS

In this observational analysis of STEMI patients who underwent primary percutaneous coronary intervention, ticagrelor was associated with improved outcomes compared with clopidogrel and prasugrel. An appropriately powered randomized trial is needed to confirm these findings.

Impact of specific functional groups in flavonoids on the modulation of platelet activation

Flavonoids exert innumerable beneficial effects on cardiovascular health including the reduction of platelet activation, and thereby, thrombosis. Hence, flavonoids are deemed to be a molecular template for the design of novel therapeutic agents for various diseases including thrombotic conditions. However, the structure-activity relationships of flavonoids with platelets is not fully understood. Therefore, this study aims to advance the current knowledge on structure-activity relationships of flavonoids through a systematic analysis of structurally-related flavones. Here, we investigated a panel of 16 synthetic flavones containing hydroxy or methoxy groups at C-7,8 positions on the A-ring, with a phenyl group or its bioisosteres as the B-ring, along with their thio analogues possessing a sulfur molecule at the 4th carbon position of the C-ring. The antiplatelet efficacies of these compounds were analysed using human isolated platelets upon activation with cross-linked collagen-related peptide by optical aggregometry. The results demonstrate that the hydroxyl groups in flavonoids are important for optimum platelet inhibitory activities. In addition, the 4-C=O and B ring phenyl groups are less critical for the antiplatelet activity of these flavonoids. This structure-activity relationship of flavonoids with the modulation of platelet function may guide the design, optimisation and development of flavonoid scaffolds as antiplatelet agents.

Consensus Document ANMCO/ANCE/ARCA/GICR-IACPR/GISE/SICOA: Long-term Antiplatelet Therapy in Patients with Coronary Artery Disease

Dual antiplatelet therapy (DAPT) with aspirin and a P2Y12 receptor inhibitor is the cornerstone of pharmacologic management of patients with acute coronary syndrome (ACS) and/or those receiving coronary stents. Long-term (>1 year) DAPT may further reduce the risk of stent thrombosis after a percutaneous coronary intervention (PCI) and may decrease the occurrence of non-stent-related ischaemic events in patients with ACS. Nevertheless, compared with aspirin alone, extended use of aspirin plus a P2Y12 receptor inhibitor may increase the risk of bleeding events that have been strongly linked to adverse outcomes including recurrent ischaemia, repeat hospitalisation and death. In the past years, multiple randomised trials have been published comparing the duration of DAPT after PCI and in ACS patients, investigating either a shorter or prolonged DAPT regimen. Although the current European Society of Cardiology guidelines provide a backup to individualised treatment, it appears to be difficult to identify the ideal patient profile which could safely reduce or prolong the DAPT duration in daily clinical practice. The aim of this consensus document is to review contemporary literature on optimal DAPT duration, and to guide clinicians in tailoring antiplatelet strategies in patients undergoing PCI or presenting with ACS.

Synthesis of a Novel Series of Amino Acid Prodrugs Based on Thienopyridine Scaffolds and Evaluation of Their Antiplatelet Activity

The thienopyridines class of drugs used as P2Y₁₂ receptor antagonists plays a vital role in antiplatelet therapy. To further optimized this compound class, we designed and synthesized a series of amino acid prodrugs of 2-hydroxytetrahydrothienopyridine. All compounds were then evaluated for their inhibitory effect on ADP-induced platelet aggregation in rats and then ED₅₀ and bleeding time of the most potent compounds were compared with commercial drugs. The results showed compound 5c could be a potent and safe candidate for further research.

Role of genetic testing in patients undergoing percutaneous coronary intervention

INTRODUCTION

Variability in individual response profiles to antiplatelet therapy, in particular clopidogrel, is a well-established phenomenon. Genetic variations of the cytochrome P450 (CYP) 2C19 enzyme, a key determinant in clopidogrel metabolism, have been associated with clopidogrel response profiles. Moreover, the presence of a CYP2C19 loss-of-function allele is associated with an increased risk of atherothrombotic events among clopidogrel-treated patients undergoing percutaneous coronary interventions (PCI), prompting studies evaluating the use of genetic tests to identify patients who may be potential candidates for alternative platelet P2Y12 receptor inhibiting therapies (prasugrel or ticagrelor). Areas covered: The present manuscript provides an overview of genetic factors associated with response profiles to platelet P2Y12 receptor inhibitors and their clinical implications, as well as the most recent developments and future considerations on the role of genetic testing in patients undergoing PCI. Expert commentary: The availability of more user-friendly genetic tests has contributed towards the development of many ongoing clinical trials and personalized medicine programs for patients undergoing PCI. Results of pilot investigations have shown promising results, which however need to be confirmed in larger-scale studies to support the routine use of genetic testing as a strategy to personalize antiplatelet therapy and improve clinical outcomes.

P2Y12 receptor inhibitors: an evolution in drug design to prevent arterial thrombosis

INTRODUCTION

P2Y12 inhibitors are a critical component of dual antiplatelet therapy (DAPT), which is the superior strategy to prevent arterialthrombosis in patients with acute coronary syndromes (ACS) and undergoing stent implantation.. Areas covered: Basic science articles, clinical studies, and reviews from 1992-2017 were searched using Pubmed library to collet impactful literature. After an introduction to the purinergic receptor biology, this review summarizes current knowledge on P2Y12 receptor inhibitors. Furthermore, we describe the subsequent improvements of next-generation P2Y12 receptor inhibitors facing the ambivalent problem of bleeding events versus prevention of arterial thrombosis in a variety of clinical settings. Therefore, we summarize data from relevant preclinical and clinical trials of currently approved P2Y12 receptor inhibitors (clopidogrel, prasugrel, ticagrelor, cangrelor) and provide strategies of drug switching and management of bleeding events. Expert opinion: An enormous amount of pharmacologic and clinical data is available for the application of P2Y12 receptor inhibitors. Today prasugrel, ticagrelor and clopidogrel are the standard of care drugs during dual antiplatelet therapy for ACS patients, but have considerable rates of bleeding. Recent and future clinical trials will provide evidence for subsequent escalation and de-escalation strategies of P2Y12 receptor inhibition. These data may pave the way for an evidence-based, individualized P2Y12 receptor inhibitor therapy.

Why does ticagrelor induce dyspnea?

In studies that compared the reversible P2Y12 inhibitor ticagrelor with the irreversible inhibitor clopidogrel, dyspnea was observed more frequently among ticagrelor-treated patients than among clopidogreltreated patients. Because dyspnea was not associated with acidosis, pulmonary or cardiac dysfunction, alterations in the mechanisms and pathways of the sensation of dyspnea may be involved in its pathogenesis. It has been hypothesised that the sensation of dyspnea in ticagrelor-treated patients is triggered by adenosine, because ticagrelor inhibits its clearance, thereby increasing its concentration in the circulation. However, dipyridamole, a much stronger inhibitor of adenosine clearance than ticagrelor, usually does not cause dyspnea. We hypothesise that inhibition of P2Y12 on sensory neurons increases the sensation of dyspnea, particularly when reversible inhibitors are used. We base our hypothesis on the following considerations: 1) cangrelor and elinogrel, which, like ticagrelor, are reversible P2Y12 inhibitors, also increase the incidence of dyspnea;2) it is biologically plausible that inhibition of P2Y12 on sensory neurons increases the sensation of dyspnea;3) inhibition of P2Y12 on platelets (which do not have a nucleus) by clopidogrel is permanent, despite the once daily administration and the short plasma half-life of the inhibitor;4) in contrast, inhibition of P2Y12 on neurons by clopidogrel may be temporary and transient, because neurons have a nucleus and can therefore rapidly replace the inhibited receptors with newly synthetised ones;5) inhibition of P2Y12 on neurons by reversible inhibitors is permanent, because the plasma drug concentration is maintained high by repeated dosing, in order to ensure permanent inhibition of platelet P2Y12.

Decrease in high on-treatment platelet reactivity (HPR) prevalence on switching from clopidogrel to prasugrel: Insights from the switching anti-platelet (SWAP) study

The prevalence of high platelet reactivity (HPR) in patients who have switched from clopidogrel to prasugrel during maintenance phase after an acute coronary syndrome (ACS) event is unknown. Therefore, the effect of switching from clopidogrel to prasugrel on the prevalence of HPR was evaluated. This analysis from the previously reported SWAP (SWitching Anti Platelet) study assessed HPR at baseline, 2 and 24 hours, and seven days after switching from clopidogrel to prasugrel maintenance dose (MD), with or without a prasugrel loading dose (LD) using four definitions: maximum platelet aggregation (MPA) >65% (primary endpoint), MPA >50%, P2Y12 reaction units (PRU) >235, and platelet reactivity index (PRI) ≥50%. A total of 95 patients were available for analysis; 56 patients provided DNA for genetic assessments of cytochrome P450 (CYP) 2C19. There were 26 (27.4%) patients with HPR at the end of the clopidogrel run-in (defined as MPA >65%). The HPR prevalence varied by each definition and ranged from 19% (PRU >235) to 68% (PRI ≥50%). A significantly higher HPR prevalence was observed during clopidogrel versus the combined prasugrel therapy groups at seven days as measured by MPA >65% (21.2% vs. 4.5%, p>0.05), PRU >235 (18.8% vs. 0%, p=0.001), and PRI ≥50% (66.7% vs. 7.9%, p<0.0001). There was a significantly higher percentage of subjects carrying at least one reduced function allele with HPR measured by MPA >65% (p=0.02) or PRU >235 (p=0.05) than non-carriers with HPR. Switching ACS patients during maintenance clopidogrel therapy to prasugrel with or without an LD is associated with a reduced HPR prevalence and may provide an alternative strategy to treat patients with HPR, independent of CYP2C19 genotype.

Eversion endarterectomy under full prasugrel treatment

The third-generation thienopyridine prasugrel has much stronger antiplatelet effect compared to other current antiplatelet inhibitors and exhibits practically zero resistance in healthy people. Prasugrel is used as a pre- and post-treatment in percutaneous coronary or neurovascular interventions with parallel aspirin regime. However, as there is a higher reported bleeding with intraluminal interventions and meticulous technique is recommended, there is nearly non-existent international experience of open surgery under full prasugrel treatment. We present, herein, a case of open carotid endarterectomy with the eversion technique in an asymptomatic patient with carotid stenosis, who was receiving dual antiplatelet therapy with aspirin and prasugrel, due to a previous insertion of two newer drug-eluting stents at the left anterior descending artery and the right coronary artery. The resistance test to prasugrel showed complete inhibition of platelet function. Open surgery was performed under continuation of prasugrel treatment and interruption of aspirin for 3 days before surgery. No perioperative and postoperative neurologic or cardiologic event occurred. No bleeding at the cervical or cerebral area was noted.

Platelet function testing and prediction of procedural bleeding risk

The essential role of platelets in haemostasis underlies the relationship between platelet function and spontaneous or procedure-related bleeding, which has important prognostic implications. Although not routinely undertaken, platelet function testing offers the potential to tailor antiplatelet therapy for individual patients. However, uncertainties remain about how well platelet function testing may predict haemostasis and guide management of bleeding risk. Studies of aspirin, P2Y12 inhibitors and other antiplatelet drugs clearly demonstrate how inhibition of platelet function increases bleeding risk. More potent antiplatelet drugs are associated with higher bleeding rates, consistent with the levels of platelet inhibition achieved by these drugs. Studies of patients treated with clopidogrel, which is associated with wide inter-individual variation in antiplatelet effect, suggest that platelet function testing may predict bleeding risk related to coronary artery bypass grafting (CABG) surgery and potentially guide the timing of surgery following discontinuation of clopidogrel. Similarly, some studies have demonstrated a relationship between clopidogrel response and bleeding in patients undergoing percutaneous coronary intervention (PCI), although other studies have not supported this. Carriage of the *17 allele of cytochrome P450 2C19, which is associated with gain of function and enhanced response to clopidogrel, seems to be associated with increased bleeding risk, although studies showing lack of apparent effect of loss-of-function alleles provide contradictory evidence. Further large studies are needed to guide best practice in the application of platelet function testing in the clinical management of patients treated with antiplatelet drugs in order to optimise individual care.

Therapeutic strategies for atherosclerosis and atherothrombosis: Past, present and future

Even two centuries after they were first described, atherosclerosis and atherothrombosis remain among the leading causes of death worldwide. Over the last decades it has become clear that atherosclerosis is not only a lipid-driven disease but also a multifactorial process largely driven by inflammatory mediators, an insight that has instigated additional research and drug development focussing on anti-inflammatory therapies. In this review, we will provide a brief historical overview, followed by a more general synopsis of the range of currently available state-of-the-art therapies for atherosclerosis and atherothrombosis. Finally, we will highlight some of the promising therapeutic strategies that are currently under intense investigation. We believe that the next years will witness highly interesting developments and clinical trials investigating yet more novel therapies, and at the same time looking into potential combinations of all available therapies. This prospect closes in on the ultimate goal, which is to reduce the residual risk that still persists despite present therapeutic options.

Clinical trial conduct in special populations and developing regions: An overview of the DOVE study in pediatric patients with sickle cell disease

Clinical trials conducted in unique patient populations or individuals with rare diseases are typically hampered by limitations in availability of qualified patients, requiring sponsors to broaden their global outreach to achieve enrollment. Engaging clinical study centers in developing regions may offer access to a substantially larger patient pool. However, they provide a unique set of challenges based on local cultures and requirements. The DOVE study (Determining effects Of platelet inhibition on Vaso-occlusive Events) was a clinical trial of prasugrel hydrochloride (prasugrel) in pediatric patients (aged 2 to <18years) with sickle cell anemia. The study was conducted at centers located in both well-developed and developing regions, enrolling 341 children. Study planning and execution required careful consideration of cultural requirements in each region and implementation of additional trial initiation and execution processes to address those needs. Innovative strategies were employed to ensure global consistency and quality in study execution. Significant regional- and country-specific differences were observed in site activation and enrollment. Although site activation processes were more complex and slower in developing countries, enrollment rates were much higher, which helped mitigate the site activation delays and allowed significant contribution to complete study enrollment. Data quality and patient retention in developing countries were equivalent to those observed in more developed countries, further supporting the ability to successfully conduct high-quality global registration trials in those countries. This report provides an overview of the experiences in site identification, site qualification, enrollment, patient retention, and data quality assurance in the DOVE study.

The progress in the research of antiplatelet agents (1995-2017)

Antiplatelet therapy displays a critical role in the treatment and prevention of antithrombotic disorders. Many new antiplatelet agents have been developed following the emergence of various clinical limitations of classical antiplatelet drugs. This review covers mainly the recent advances in the development of P2Y₁₂ antagonists and GPIIb/IIIa antagonists. Meanwhile, it summarizes promising approaches to new platelet surface receptors such as prostanoid EP3 receptor, thromboxane A₂ prostanoid receptor, protease-activated receptors, GPIb-IX-V receptor and P-selectin. In addition, PI3K_β, a critical protein at the inside signaling pathway of platelet activation is also mentioned as an important antiplatelet target. Moreover, the development of respective drug candidates is discussed in detail.

Cangrelor in Percutaneous Coronary Intervention: Current Status and Perspectives

Cangrelor is an intravenously administered P2Y₁₂ receptor antagonist with very fast, potent, and quickly reversible action. In the CHAMPION PHOENIX trial, cangrelor provided an improved anti-ischemic protection compared with clopidogrel, without increasing the risk of severe bleeding. Cangrelor is currently approved by drug regulating authorities for patients undergoing percutaneous coronary intervention (PCI) without prior treatment with a P2Y₁₂ receptor antagonist and not receiving a glycoprotein IIb/IIIa inhibitor, while its use is endorsed with a class IIb recommendation by the European Society of Cardiology guidelines. Several subanalyses of CHAMPION PHOENIX trial have tried to elucidate the role of cangrelor in PCI, including its usefulness during a 2-hour landmark analysis, impact on intraprocedural stent thrombosis, and reduction in myocardial infarction (MI) rate. The influence of gender, geographic region, access site, and bivalirudin use on cangrelor's effects has also been reported. In patients with ST elevation MI and in clinical scenarios of disturbed absorption of oral antiplatelet agents or in need of an intravenous agent, cangrelor may surpass oral agents' drawbacks. Transitioning to an oral agent is mandatory following cangrelor infusion discontinuation, although ticagrelor may be administered earlier without any pharmacodynamic interaction. Nevertheless, the clinical role of cangrelor in conjunction with administration of prasugrel or ticagrelor remains unclear. Accruing real-life experience is expected to improve our understanding of cangrelor's role in everyday clinical practice.

Prasugrel hydrochloride for the treatment of sickle cell disease

INTRODUCTION

Therapeutic options for sickle cell disease (SCD) are limited and, currently, only one drug (hydroxyurea) has FDA approval for the treatment of adult SCD. While this genetic disease is caused by hemoglobin polymerization, subsequent downstream events trigger platelet activation, vaso-occlusion and the disease's complex pathophysiology. Areas covered: The oral thienopyridine, prasugrel hydrochloride, irreversibly inhibits the P2Y12 receptors, inhibiting ADP-dependent platelet activation. We discuss recent clinical trials evaluating the pharmokinetics of prasugrel and its potential for use in SCD. Expert opinion: Prasugrel administration in SCD appears to be well tolerated and safe. However, although this drug modestly inhibits platelet activity in these patients, administration of prasugrel to a large group of children and adolescents for up to 24 months failed to convincingly reduce vaso-occlusive complications. Speculatively, prasugrel may be of occasional use for off-license purposes in patients unable or unwilling to take hydroxyurea (particularly in 12-17-year olds). Although there is currently no prospect of prasugrel being licensed for use in SCD, the success of on-going trials of other antiplatelet agents in SCD might lead to further trials of prasugrel in SCD.

Evaluation of the Pharmacokinetics and Pharmacodynamics of Prasugrel in Japanese Elderly Subjects

Background and Objective

An increased incidence in bleeding events has been reported in Western elderly patients receiving prasugrel. Therefore, doses in Japanese elderly subjects need to be carefully determined. We assessed the pharmacokinetic and pharmacodynamic effects of prasugrel at the clinical dose used in Japan in healthy Japanese elderly subjects compared with non-elderly subjects.

Methods

In an open-label parallel-group study conducted in Japan, two groups (elderly, aged >75 years; non-elderly, aged 45–65 years) received a 20-mg loading dose and a 3.75-mg maintenance dose of prasugrel for 7 days. Plasma concentration of its active metabolite, R-138727, and pharmacokinetic parameters were determined on days 1 and 7 after dosing. Pharmacodynamic response to 20 µM of adenosine diphosphate-induced platelet aggregation was measured by light transmission aggregometry.

Results

A total of 47 subjects were enrolled (23 elderly, 24 non-elderly). There was no statistically significant difference in pharmacokinetic parameters between groups: area under the plasma concentration–time curve up to the last quantifiable time and maximum plasma concentration were about 174–175 ng·h/mL and 134–153 ng/mL, respectively, after the loading dose; and about 25–26 ng·h/mL and 25 ng/mL, respectively, after the maintenance dose. Inhibition of platelet aggregation was higher in the elderly subjects than in the non-elderly subjects, with a statistically significant difference from 24 h after the loading dose. No serious adverse events (bleeding or non-bleeding) occurred.

Conclusions

Prasugrel (20-mg loading dose; 3.75-mg maintenance dose) produced a slight increase in antiplatelet efficacy in elderly compared with non-elderly subjects, despite no statistically significant difference in the pharmacokinetics.

Electronic supplementary material

The online version of this article (doi:10.1007/s40261-017-0525-0) contains supplementary material, which is available to authorized users.

Newly Formed Reticulated Platelets Undermine Pharmacokinetically Short-Lived Antiplatelet Therapies

Supplemental Digital Content is available in the text.

Objective—

Aspirin together with thienopyridine P2Y₁₂ inhibitors, commonly clopidogrel, is a cornerstone of antiplatelet therapy. However, many patients receiving this therapy display high on-treatment platelet reactivity, which is a major therapeutic hurdle to the prevention of recurrent thrombotic events. The emergence of uninhibited platelets after thrombopoiesis has been proposed as a contributing factor to high on-treatment platelet reactivity. Here, we investigate the influences of platelet turnover on platelet aggregation in the face of different dual-antiplatelet therapy strategies.

Approach and Results—

Traditional light transmission aggregometry, cytometry, advanced flow cytometric imaging, and confocal microscopy were used to follow the interactions of populations of platelets from healthy volunteers and patients with stable cardiovascular disease. Newly formed, reticulated platelets overproportionately contributed to, and clustered at, the core of forming aggregates. This phenomenon was particularly observed in samples from patients treated with aspirin plus a thienopyridine, but was absent in samples taken from patients treated with aspirin plus ticagrelor.

Conclusions—

Reticulated platelets are more reactive than older platelets and act as seeds for the formation of platelet aggregates even in the presence of antiplatelet therapy. This is coherent with the emergence of an uninhibited subpopulation of reticulated platelets during treatment with aspirin plus thienopyridine, explained by the short pharmacokinetic half-lives of these drugs. This phenomenon is absent during treatment with ticagrelor, because of its longer half-life and ability to act as a circulating inhibitor. These data highlight the important influences of pharmacokinetics on antiplatelet drug efficacies, especially in diseases associated with increased platelet turnover.

Antiplatelet agents in hemodialysis

Patients affected by cardiovascular disease (CVD) are treated with antiplatelet agents (AA) and/or anticoagulant drugs, which are fundamental in the management of stroke, coronary atherosclerotic disease, peripheral vascular disease and atrial fibrillation. CVD is the most important cause of death in chronic renal failure (CRF). Death rates from myocardial infarction (MI) and from all other cardiac causes exceed those for the general population. Incidence of MI in CRF is triple that in the general population. Moreover, mortality is seven- to eight-fold higher in patients requiring chronic hemodialysis compared to the general population, and approximately 40% of deaths in this population are attributable to coronary artery disease (CAD). For these reasons, AA are widely used in patients affected by CRF. Current data do not support a protective effect of antiplatelet administration in hemodialytic patients as primary prevention of cardiovascular mortality. Different results have been obtained concerning secondary prevention of CVD. The Cooperative Cardiovascular Project demonstrated that dialysis patients treated with aspirin following MI had a 43% lower mortality. Another study reported that the use of aspirin and beta-blockers following MI was associated with lower mortality in CRF patients. However, aspirin plus clopidogrel seems to increase the hemorrhagic risk without a significant reduction in cardiovascular mortality and there are insufficient data to support the use of new AA drugs in hemodialytic patients. In conclusion, since CRF patients are one of the groups at highest risk for atherosclerotic events, it could be reasonable to use aspirin in HD patients. However, the bleeding risk in HD patients needs to be strongly evaluated, especially before starting dual AA treatment.

Real-time dose adjustment using point-of-care platelet reactivity testing in a double-blind study of prasugrel in children with sickle cell anaemia

Patients with sickle cell anaemia (SCA) have vaso-occlusive crises resulting from occlusive hypoxic-ischaemic injury. Prasugrel inhibits platelet activation and aggregation involved in SCA pathophysiology. Determining Effects of Platelet Inhibition on Vaso-Occlusive Events (DOVE) was a phase 3, double-blind, randomised, placebo-controlled trial assessing prasugrel efficacy. DOVE sought to bring patients' P2Y12 reaction unit (PRU) value within a targeted range via prasugrel dose adjustments using encrypted VerifyNow P2Y12^® (VN-P2Y12) point-of-care testing and an interactive voice-response system (IVRS). After PRU determination, randomised patients received 0.08 mg/kg/day prasugrel or placebo. Encrypted PRUs and IVRS provided double-blind dose adjustments to achieve a defined PRU target range of 136-231; placebo patients had mock titrations. Of 341 randomised patients, 166 placebo and 160 prasugrel patients reached the fully titrated dose (FTD). Most prasugrel patients (n=104, 65 %) remained on the initial 0.08 mg/kg dose; doses escalations occurred in 23 % of patients (n=36). Mean PRUs for the pharmacodynamic population at baseline were similar in the prasugrel (273 ± 44.9) and placebo groups (273 ± 51.7), with significant reductions in PRU (p<0.001) for prasugrel patients at the FTD and at 9 months. Concomitant use of hydroxyurea did not affect platelet reactivity at any time. The majority of prasugrel patients (n=135, 84.4 %) at the FTD were within the target range of 136-231 PRUs. Mean VN-P2Y12 percentage inhibition at baseline was similar in the prasugrel (2.8  ± 5.4 %) and placebo groups (2.0 ± 4.7 %); prasugrel patients had significant increases in inhibition (p<0.001) at FTD and at 9 months. Patients with higher PRU values at baseline required higher prasugrel doses to bring PRU within the prespecified range. DOVE is the first study to successfully employ double-blind, real-time, encrypted, point-of-care platelet testing and IVRS to dose-adjust antiplatelet therapy to a targeted range of platelet inhibition.

Prasugrel, a Platelet P2Y12 Receptor Antagonist, Improves Abnormal Gait in a Novel Murine Model of Thrombotic Hindlimb Ischemia

Background

The efficacy of P2Y₁₂ inhibition for the prevention of cardiovascular events in patients with peripheral arterial disease (PAD) has been established. However, the therapeutic effects on ischemic limb complications are less clear. Accordingly, we aimed to develop a novel murine model of thrombotic hindlimb ischemia to reflect that found in patients with PAD exhibiting ischemic limb symptoms. We further investigated the effects of P2Y₁₂ deficiency and P2Y₁₂ inhibition by prasugrel in this model.

Methods and Results

Thrombus formation induced by application of ferric chloride to the femoral artery resulted in a significant reduction in blood flow in the injured limb. In gait analysis using the CatWalk system, moderate difficulties in grounding and weight bearing of the ischemic limb, including reduction of maximum contact area and stance phase duration and increasing in swing phase duration in the ischemic limb, were observed in this model. Blood flow reduction and gait abnormalities gradually recovered over 21 days to levels present before arterial injury. Compared to wild‐type (WT) mice, significant increases in blood flow and improvement in gait were observed in P2Y₁₂‐deficient mice. In addition, daily oral administration of prasugrel (3 mg/kg per day) to WT mice resulted in significant inhibition of blood flow reduction and gait abnormalities to levels found in P2Y₁₂ deficient mice.

Conclusions

Acute femoral artery thrombosis resulted in hindlimb ischemia and moderate gait abnormalities in mice. In addition, the present study suggests a possible role of P2Y₁₂ in the complications with thrombotic limb ischemia.

Pharmacokinetics and pharmacodynamics of prasugrel in healthy Japanese subjects

This randomized double-blind and placebo-controlled study assessed the pharmacodynamics and pharmacokinetics of prasugrel in healthy adult Japanese male subjects after single (n = 50) and multiple (n = 40) oral administration. With a single administration of prasugrel (2-30 mg), the plasma concentration of the active metabolite increased rapidly, reached a maximum at 30 min after administration, and then decreased rapidly within 4 h. The 5 mg and higher doses prevented ADP-induced platelet aggregation in a dose-dependent manner. Further analyses showed that 30 mg prasugrel exhibited the peak inhibition, and 20 mg prasugrel showed a nearly equivalent effect. With multiple doses (2.5-10 mg), the pharmacokinetic parameters on Day 1 and Day 7 were similar, and no accumulation attributable to multiple dosing was observed. The inhibitory effect on ADP-induced platelet aggregation increased with doses from 2.5 to 7.5 mg, and reached the peak level at 7.5 mg. Regarding safety, all of the drug-related adverse events observed were mild, and there were no clinically significant bleeding-related adverse events. This study indicates that a single oral administration of prasugrel at a dose of up to 30 mg and a maintenance dose of up to 10 mg are tolerated in Japanese healthy subjects.

Time-Varying Effects of Prasugrel Versus Clopidogrel on the Long-Term Risks of Stroke After Acute Coronary Syndromes: Results From the TRILOGY ACS Trial

BACKGROUND AND PURPOSE

The role of more intense, sustained platelet inhibition in preventing stroke after acute coronary syndrome (ACS) is unclear. We observed a signal for reduced stroke risk in the Targeted Platelet Inhibition to Clarify the Optimal Strategy to Medically Manage Acute Coronary Syndromes (TRILOGY ACS) trial after 12 months of treatment with prasugrel versus clopidogrel in medically managed patients with ACS.

METHODS

We examined 7243 patients with ACS, aged <75 years and without prior stroke, analyzing differences in baseline characteristics between patients with and without a stroke event through 30 months with a Cox proportional hazards model. We also assessed the effect of prasugrel versus clopidogrel (plus aspirin) on risk of all stroke events and ischemic stroke over time with an extended Cox proportional hazards model.

RESULTS

Stroke events were infrequent through 30 months (ischemic stroke=62; hemorrhagic stroke=15). Patients with stroke were older, had more comorbidities, and had a higher Global Registry of Acute Coronary Events (GRACE) risk score. There was a trend for a lower unadjusted frequency of all stroke events through 30 months for prasugrel versus clopidogrel: 31 (1.5%) versus 46 (2.2%); P=0.08. There was a significant treatment-by-time interaction for those with ischemic stroke (P=0.03), consistent with the 12-month landmarked Kaplan-Meier log-rank test showing a reduced hazard of ischemic stroke after 12 months with prasugrel (P=0.04). No significant interactions between treatment effect of prasugrel versus clopidogrel and time were observed for all stroke events.

CONCLUSIONS

We observed a potential late treatment effect for prasugrel versus clopidogrel for a reduced risk of ischemic stroke in medically managed patients with ACS aged <75 years. These hypothesis-generating findings suggest that longer duration and more potent platelet inhibition with prasugrel may be associated with lower risk of ischemic stroke after 12 months.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00699998.

A Multinational Trial of Prasugrel for Sickle Cell Vaso-Occlusive Events

BACKGROUND

Sickle cell anemia is an inherited blood disorder that is characterized by painful vaso-occlusive crises, for which there are few treatment options. Platelets mediate intercellular adhesion and thrombosis during vaso-occlusion in sickle cell anemia, which suggests a role for antiplatelet agents in modifying disease events.

METHODS

Children and adolescents 2 through 17 years of age with sickle cell anemia were randomly assigned to receive oral prasugrel or placebo for 9 to 24 months. The primary end point was the rate of vaso-occlusive crisis, a composite of painful crisis or acute chest syndrome. The secondary end points were the rate of sickle cell-related pain and the intensity of pain, which were assessed daily with the use of pain diaries.

RESULTS

A total of 341 patients underwent randomization at 51 sites in 13 countries across the Americas, Europe, Asia, and Africa. The rate of vaso-occlusive crisis events per person-year was 2.30 in the prasugrel group and 2.77 in the placebo group (rate ratio, 0.83; 95% confidence interval, 0.66 to 1.05; P=0.12). There were no significant differences between the groups in the secondary end points of diary-reported events. The safety end points, including the frequency of bleeding events requiring medical intervention, of hemorrhagic and nonhemorrhagic adverse events that occurred while patients were taking prasugrel or placebo, and of discontinuations due to prasugrel or placebo, did not differ significantly between the groups.

CONCLUSIONS

Among children and adolescents with sickle cell anemia, the rate of vaso-occlusive crisis was not significantly lower among those who received prasugrel than among those who received placebo. There were no significant between-group differences in the safety findings. (Funded by Daiichi Sankyo and Eli Lilly; ClinicalTrials.gov number, NCT01794000.).

Design of the DOVE (Determining Effects of Platelet Inhibition on Vaso-Occlusive Events) trial: A global Phase 3 double-blind, randomized, placebo-controlled, multicenter study of the efficacy and safety of prasugrel in pediatric patients with sickle cell anemia utilizing a dose titration strategy

BACKGROUND

Sickle cell disease (SCD) is an inherited blood disorder characterized by painful vaso-occlusive crises (VOC) with limited treatment options, particularly for children. Emerging knowledge of the pathophysiology of SCD suggests antiplatelet therapies may hold promise for treatment of VOC. Multiple small studies have evaluated antiplatelet agents on the frequency of VOC with varying results, but there has not been an adequately powered study to definitively determine the effect of antiplatelet agents on VOC. Prasugrel, a third-generation thienopyridine that irreversibly inhibits platelet activation and aggregation, is approved in adults with acute coronary syndrome managed with percutaneous coronary intervention.

PROCEDURE

Determining Effects of Platelet Inhibition on Vaso-Occlusive Events (DOVE) is a double-blind, randomized study with planned enrollment of >220 children from 14 countries across the Americas, Europe, Asia, and Africa, designed to test the hypothesis that prasugrel reduces the rate of VOC in children with sickle cell anemia (SCA) (homozygous hemoglobin S [HbSS] and hemoglobin Sβ(0) thalassemia [HbSβ(0)]). Secondary study endpoints include reductions in rate and intensity of vaso-occlusive pain as recorded in daily electronic diaries. Safety assessments include incidence of hemorrhagic events requiring medical intervention and treatment-emergent adverse events. DOVE incorporates a dose-titration strategy to reduce potential bleeding risks inherent with antiplatelet therapy while maintaining blinded treatment assignment.

CONCLUSIONS

DOVE presents a unique opportunity to determine whether antiplatelet therapy reduces frequency of patient-reported VOC and daily vaso-occlusive pain in a global study of children with SCA.

Prevention of occlusive arterial thrombus formation by a single loading dose of prasugrel suppresses neointimal hyperplasia in mice

The present study examined the effects of prasugrel in a mouse model of thrombosis-induced neointimal hyperplasia. Following carotid artery injury by application of ferric chloride solution, thrombus formation was assessed on Day 1 and neointimal thickening was assessed on Day 21. Single administrations of prasugrel at 0.3-3mg/kg (p.o.) resulted in a dose-related and sustained inhibition of ADP-induced platelet aggregation through 24h. Single and multiple (1 and 3 weeks) administration of prasugrel (3mg/kg loading and 1mg/kg/day maintenance doses) resulted in a marked inhibition of neointimal thickening in the injured artery. In the dose-response study, a single administration of prasugrel at 0.3-3mg/kg (p.o.) dose-relatedly inhibited thrombus formation and neointimal thickening on Days 1 and 21, respectively. The degree of neointimal hyperplasia in the injured artery correlated significantly with the thrombus indices, time to occlusion and patency rate. To explore possible mechanisms of inhibition of neointimal hyperplasia by prasugrel, mRNA expression levels of inflammatory and fibrosis markers were determined in injured arteries. Prasugrel treatment resulted in reduced MCP-1, ICAM-1 and TGF-β mRNA levels on Day 2 (24h after the injury) and Day 8 (1 week after the injury) in the target arteries. In conclusion, we found that a single oral loading dose of prasugrel markedly prevented neointimal hyperplasia by inhibiting platelet activation and thrombus formation and was associated with inhibition of the expression of inflammatory and fibrosis markers, including MCP-1, ICAM-1 and TGF-β, in the injured arteries.

Harmonizing Optimal Strategy for Treatment of coronary artery diseases--comparison of REDUCtion of prasugrEl dose or POLYmer TECHnology in ACS patients (HOST-REDUCE-POLYTECH-ACS RCT): study protocol for a randomized controlled trial

Background

Antiplatelet treatment is an important component in optimizing the clinical outcomes after percutaneous coronary intervention (PCI) especially in patients with acute coronary syndrome (ACS). Prasugrel, which is a new P2Y12 inhibitor, has been confirmed as efficacious in a large trial in Western countries, and a similar trial is also to be launched in Asian countries. Although a 60-mg loading dose of prasugrel followed by 10 mg per day should be acceptable, there have been no data regarding the optimal dose in Asian patients. Furthermore, serum levels of prasugrel and the rates of platelet inhibition are known to be higher in Asians than Caucasians with the same dose of the drug.

Polymer, a key component of drug-eluting stents (DES), has been suggested as the cause of inflammation leading to late complications, and has driven many companies to develop biodegradable-polymer DES. Currently, there are limited data regarding the head-to-head comparison between BP-BES and the biostable polymer CoCr-EES or the newest platinum-chromium everolimus-eluting stent (PtCr-EES). Furthermore, the polymer issue may be more important in ACS where there is ruptured thrombotic plaque where polymer-induced inflammation may affect the local milieu of the stented artery.

Therefore, the present study dedicated only to ACS patients, will offer important information on the optimal prasugrel dose in the Asian population by comparing a 10-mg versus a 5-mg maintenance dose beyond 1 month after PCI, as well as giving important insight into the polymer issue by comparing BP-BES versus biostable-polymer PtCr-EES.

Method/Design

Harmonizing Optimal Strategy for Treatment of coronary artery diseases – comparison of REDUCtion of prasugrEl dose or POLYmer TECHnology in ACS patients (HOST-REDUCE-POLYTECH-ACS) trial is a multicenter, randomized and open-label clinical study with a 2 × 2 factorial design, according to the type of stent (PtCr-EES versus BP-BES) and prasugrel maintenance dose (5 mg versus 10 mg), to demonstrate non-inferiority of PtCr-EES relative to BP-BES or the reduced prasugrel dose relative to conventional dose in an Asian all-comers PCI population presenting with ACS. Approximately 3400 patients will undergo prospective, random assignment separately to either stent or prasugrel arm (1:1 ratio, respectively). When the patients have contraindications to prasugrel, they are categorized into an antiplatelet observation group after stent-randomization. The primary endpoint is the patient-oriented composite outcome, which is a composite of all-cause mortality, any myocardial infarction (MI), any repeat revascularization in the stent arm at 12 months after index PCI. In the prasugrel arm, primary endpoint is any major adverse cardiovascular event, which is a composite of all-cause mortality, any MI, any stent thrombosis (Academic Research Consortium (ARC)-defined), any repeat revascularization, stroke, or bleeding (BARC class ≥ 2).

Discussion

The HOST-REDUCE-POLYTECH-ACS RCT is the first study exploring the optimal maintenance dose of prasugrel beyond 1 month after PCI for ACS in Asian all-comers. In addition, this is the largest study dedicated only to ACS patients to evaluate the polymer issue in the situation of ACS by directly comparing biostable-polymer PtCr-EES versus BP-BES.

Trial registration

ClinicalTrials.gov (ID: NCT02193971, 13 July 2014).

Prasugrel reduces ischaemic infarct volume and ameliorates neurological deficits in a non-human primate model of middle cerebral artery thrombosis

Several clinical trials have demonstrated the benefits of thienopyridine monotherapy in ischaemic stroke patients. Non-human primate models of ischaemic stroke have been used for various antithrombotic agents; however, to the best of our knowledge, there is no data on the effects of P2Y12 antagonists in models, such as the thrombotic middle cerebral artery occlusion (MCAO) monkey model. Accordingly, it remains unclear what level of inhibition of platelet aggregation (IPA) is required for optimal treatment of ischaemic stroke. In the present study, we investigated the effects of prasugrel, a third-generation thienopyridine antiplatelet drug, on platelet aggregation, thrombus formation and cerebral infarct volume in a non-human primate model. Daily oral administration of prasugrel resulted in significant and stable platelet inhibitory effects on Day 3, with IPA values ranging from 31% to 36% at 0.3mg/kg/day and from 44% to 50% at 1mg/kg/day. These IPA levels encompassed values observed in clinical trials of clopidogrel, and were thus selected for further study. In the thrombotic MCAO model, prasugrel increased MCA patency in a dose-dependent manner and significantly reduced ischaemic infarct volume by approximately 70% at 0.3mg/kg/day and 90% at 1mg/kg/day without increasing haemorrhagic infarction. Prasugrel also significantly reduced neurological deficit scores by 60% at 0.3mg/kg/day and 80% at 1mg/kg/day. In conclusion, prasugrel treatment resulted in effective reduction of ischaemic infarction and an associated improvement in neurological function without increasing haemorrhagic infarction. These data suggest that prasugrel monotherapy would be effective for the prevention of thrombotic stroke.