New Antiplatelet Strategies in Atherothrombosis and Their Indications

Antiplatelet and myocardial protective effect of Shexiang Tongxin Dropping Pill in patients undergoing percutaneous coronary intervention: A randomized controlled trial

BACKGROUND

High on-clopidogrel platelet reactivity could be partially explained by loss-of-function alleles of CYP2C19, the enzyme that converts clopidogrel into its active form. Shexiang Tongxin Dropping Pill (STDP) is a traditional Chinese medicine to treat angina pectoris. STDP has been shown to improve blood flow in patients with slow coronary flow and attenuate atherosclerosis in apolipoprotein E-deficient mice. However, whether STDP can affect platelet function remains unknown.

OBJECTIVE

The purpose of this study is to examine the potential effects of STDP on platelet function in patients undergoing percutaneous coronary intervention (PCI) for unstable angina. The interaction between the effects of STDP with polymorphisms of CYP2C19 was also investigated.

DESIGN, PARTICIPANTS AND INTERVENTION

This was a single-center, randomized controlled trial in patients undergoing elective PCI for unstable angina. Eligible subjects were randomized to receive STDP (210 mg per day) plus dual antiplatelet therapy (DAPT) with clopidogrel and aspirin or DAPT alone.

MAIN OUTCOME MEASURES

The primary outcome was platelet function, reflected by adenosine diphosphate (ADP)-induced platelet aggregation and platelet microparticles (PMPs). The secondary outcomes were major adverse cardiovascular events (MACEs) including recurrent ischemia or myocardial infarction, repeat PCI and cardiac death; blood biomarkers for myocardial injury including creatine kinase-MB isoenzyme (CK-MB) and high-sensitive troponin I (hsTnI); and biomarkers for inflammation including intercellular cell adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), monocyte chemoattractant protein-1 (MCP-1) and galectin-3.

RESULTS

A total of 118 subjects (mean age: [66.8 ± 8.9] years; male: 59.8%) were included into analysis: 58 in the control group and 60 in the STDP group. CYP2C19 genotype distribution was comparable between the 2 groups. In comparison to the control group, the STDP group had significantly lower CK-MB (P < 0.05) but similar hsTnI (P > 0.05) at 24 h after PCI, lower ICAM-1, VCAM-1, MCP-1 and galectin-3 at 3 months (all P < 0.05) but not at 7 days after PCI (P > 0.05). At 3 months, the STDP group had lower PMP number ([42.9 ± 37.3] vs. [67.8 ± 53.1] counts/μL in the control group, P = 0.05). Subgroup analysis showed that STDP increased percentage inhibition of ADP-induced platelet aggregation only in slow metabolizers (66.0% ± 20.8% in STDP group vs. 36.0% ± 28.1% in the control group, P < 0.05), but not in intermediate or fast metabolizers. The rate of MACEs during the 3-month follow-up did not differ between the two groups.

CONCLUSION

STDP produced antiplatelet, anti-inflammatory and cardioprotective effects. Subgroup analysis indicated that STDP inhibited residual platelet reactivity in slow metabolizers only.

TRIAL REGISTRATION

This study was registered on www.chictr.org.cn: ChiCTR-IPR-16009785.

Anti-platelet Drug-loaded Targeted Technologies for the Effective Treatment of Atherothrombosis

Atherothrombosis results from direct interaction between atherosclerotic plaque and arterial thrombosis and is the most common type of cardiovascular disease. As a long term progressive disease, atherosclerosis frequently results in an acute atherothrombotic event through plaque rupture and platelet-rich thrombus formation. The pathophysiology of atherothrombosis involves cholesterol accumulation endothelial dysfunction, dyslipidemia, immuno-inflammatory, and apoptotic aspects. Platelet activation and aggregation is the major cause for stroke because of its roles, including thrombus, contributing to atherosclerotic plaque, and sealing off the bleeding vessel. Platelet aggregates are associated with arterial blood pressure and cardiovascular ischemic events. Under normal physiological conditions, when a blood vessel is damaged, the task of platelets within the circulation is to arrest the blood loss. Antiplatelet inhibits platelet function, thereby decreasing thrombus formation with complementary modes of action to prevent atherothrombosis. In the present scientific scenario, researchers throughout the world are focusing on the development of novel drug delivery systems to enhance patient's compliance. Immediate responding pharmaceutical formulations become an emerging trend in the pharmaceutical industries with better patient compliance. The proposed review provides details related to the molecular pathogenesis of atherothrombosis and recent novel formulation approaches to treat atherothrombosis with particular emphasis on commercial formulation and upcoming technologies.

Antiplatelet drugs and platelet reactivity: is it time to halt clinical research on tailored strategies?

Personalized medicine of antiplatelet drugs in cardiovascular patients has led to a significant enthusiasm. Indeed, numerous longitudinal studies showed an association between high platelet reactivity and the recurrence of ischemic events. The first small randomized trials of P2Y12 blockers tailored to each patient's platelet reactivity yielded encouraging reductions of coronary stent thrombosis in high-risk populations. The discovery of genetic variants contributing to the pharmacodynamic effect of clopidogrel has then paved the way toward a personalized antiplatelet therapy based on reliable and stable genetic tests. This enthusiasm was soon tempered by large interventional trials demonstrating that a platelet function testing-based strategy did not improve clinical outcome and that genetic variants discovered up to now only explained a small part of the pharmacodynamic effect of clopidogrel, thus limiting its clinical use. Looking back to the most recent trials, their target populations and the type of clinical setting, it seems that the one-size-fits all policy regarding antiplatelet drugs may be well acceptable for low-risk patients. On the contrary, integration of the clinical setting as well as other risk factors may help to identify subgroups of patients who could derive a benefit from a truly personalized management of antiplatelet therapy.

Influence of the paraoxonase-1 Q192R genetic variant on clopidogrel responsiveness and recurrent cardiovascular events: a systematic review and meta-analysis

BACKGROUND

A poor biological response to clopidogrel is associated with an increased risk of major cardiovascular ischemic events (MACE). Paraoxonase 1 (PON1) enzyme activity is modulated by the PON1-Q192R variant (rs662) and was recently suggested to be strongly involved in clopidogrel bioactivation, but the influence of the PON1-Q192R variant on the risk of MACE in clopidogrel-treated patients is controversial.

OBJECTIVES

To determine whether the PON1-Q192R variant influences clopidogrel biological responsiveness and the risk of MACE in patients treated with clopidogrel.

METHODS

Systematic review and meta-analysis of studies of the association between the PON1-Q192R polymorphism and the biological response to clopidogrel and/or the risk of MACE during clopidogrel administration.

RESULTS

Seventeen studies were included. In the 12 studies of the biological response to clopidogrel (n = 5302 patients), there was no significant difference between 192QQ and 192QR + 192RR subjects, whatever the laboratory method used (global mean standardized difference = 0.10 [-0.06; 0.25], P = 0.22). Eleven studies assessed the risk of MACE, four using a case-control design (n = 2739 patients) and seven a prospective design (n = 5353 patients). Overall, MACE occurred in 19% of patients in case-control studies and in 6% of patients in prospective cohort studies, with no significant difference between 192QQ and 192QR + 192RR patients (OR = 1.28 [0.97; 1.68], P = 0.08). Similar results were obtained when study design was taken into account. Heterogeneity was mainly driven by one publication.

CONCLUSIONS

This meta-analysis suggests that the PON1-Q192R polymorphism has no major impact on the risk of MACE and does not alter the biological response to clopidogrel in clopidogrel-treated patients.

Antiplatelet drug response status does not predict recurrent ischemic events in stable cardiovascular patients: results of the Antiplatelet Drug Resistances and Ischemic Events study

BACKGROUND

The biological response to antiplatelet drugs has repeatedly been shown to predict the recurrence of major adverse cardiovascular events (MACEs). However, most studies involved coronary artery disease patients with recent vessel injury shortly after the initiation of antiplatelet therapy. Data on stable cardiovascular patients are scarce, and the added predictive value of specific assays (the vasodilator phosphoprotein assay for the clopidogrel response and serum thromboxane B2 for the aspirin response) and aggregation-based assays relative to common predictors has rarely been addressed.

METHODS AND RESULTS

Stable cardiovascular outpatients participating in the Antiplatelet Drug Resistances and Ischemic Events (ADRIE) study (n=771) were tested twice, at 2 separate visits, with specific and aggregation-based assays. Follow-up lasted 3 years, and <1% of patients were lost to follow-up. MACEs were adjudicated by an independent committee. Multivariate survival analyses included relevant variables identified in univariate analysis and platelet function test results. The C-index was used to express the prognostic value of various multivariate models. MACEs, the primary end point, occurred in 16% of patients. Hypertension, smoking, older age, and elevated low-density lipoprotein cholesterol were predictive of MACE recurrence, with a C-index of 0.63 (P<0.001). Neither the specific nor the aggregation-based assays added significant predictive value for the primary end point.

CONCLUSIONS

Biological antiplatelet drug responsiveness, measured with specific or aggregation-based assays, has no incremental predictive value over common cardiovascular risk factors for MACE recurrence in stable cardiovascular outpatients. These results do not support platelet function testing for MACE risk evaluation in stable cardiovascular patients.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00501423.

Platelet proteomics

Platelets are small cell fragments, produced by megakaryocytes, in the bone marrow. They play an important role in hemostasis and diverse thrombotic disorders. They are therefore primary targets of antithrombotic therapies. They are implicated in several pathophysiological pathways, such as inflammation or wound repair. In blood circulation, platelets are activated by several pathways including subendothelial matrix and thrombin, triggering the formation of the platelet plug. Studying their proteome is a powerful approach to understand their biology and function. However, particular attention must be paid to different experimental parameters, such as platelet quality and purity. Several technologies are involved during the platelet proteome processing, yielding information on protein identification, characterization, localization, and quantification. Recent technical improvements in proteomics combined with inter-disciplinary strategies, such as metabolomic, transcriptomics, and bioinformatics, will help to understand platelets biological mechanisms. Therefore, a comprehensive analysis of the platelet proteome under different environmental conditions may contribute to elucidate complex processes relevant to platelet function regarding bleeding disorders or platelet hyperreactivity and identify new targets for antiplatelet therapy.

Clinical predictors of dual aspirin and clopidogrel poor responsiveness in stable cardiovascular patients from the ADRIE study

BACKGROUND

Poor response to both aspirin and clopidogrel (dual poor responsiveness [DPR]) is a major risk factor for recurrent ischemic events.

OBJECTIVES

The aim of this study was to identify factors associated with DPR, defined with specific tests, and derive a predictive clinical score.

METHODS

We studied 771 consecutive stable cardiovascular patients treated with aspirin (n = 223), clopidogrel (n = 111), or both drugs (n = 37). Aspirin responsiveness was evaluated by serum thromboxane (Tx)B₂ assay, and clopidogrel responsiveness by calculating the platelet reactivity index (PRI) on the basis of the phosphorylation status of the vasodilator phosphoprotein. The analysis was focused on patients treated with both drugs, and on independent predictors of DPR.

RESULTS

Among patients on dual therapy, there was no relevant correlation between TxB₂ levels and PRI values (r = 0.11). Sixty-seven patients (15.4%) had DPR. Diabetes [odds ratio (OR) 1.89, 95% confidence interval (CI) 1.06-3.39], high body weight (> 86 kg vs. < 77 kg, OR 4.74, 95% CI 2.49-9.73), low aspirin dose (75-81 mg vs. ≥ 160 mg, OR 0.12, 95% CI 0.09-0.93) and high C-reactive protein (CRP) level (> 1.6 mg L⁻¹ vs. < 0.6 mg L⁻¹, OR 3.66, 95% CI 1.74-8.72) were independently associated with DPR, via increased TxB(2) levels, increased PRI, or both. These associations with TxB₂ and PRI were reproduced across the whole population. With use of a factor-weighed score (c-index = 0.74), the predicted prevalence of DPR was 57% in the highest strata of the score as compared with < 4% for the lowest strata.

CONCLUSIONS

Diabetes, body weight, the aspirin dose and CRP levels are readily available independent predictors of DPR, and some are potential targets for reducing its prevalence.

Clinical implications of clopidogrel non-response in cardiovascular patients: a systematic review and meta-analysis

BSUMMARY BACKGROUND: Previous studies have shown an important risk of cardiovascular events in patients with clopidogrel biological non-response, and data have shown considerable, unexplored heterogeneity.

OBJECTIVES

To evaluate the magnitude of cardiovascular risk associated with clopidogrel non-response and to explore heterogeneity.

METHODS

This was a systematic review and meta-analysis of prospective studies of patients treated with clopidogrel for symptomatic atherothrombosis, evaluated by light transmission aggregometry with ADP and monitored prospectively for clinical ischemic events.

RESULTS

Fifteen studies were included, totaling 3960 patients, of whom 25% were considered to be clopidogrel non-responders. The global relative risk (RR) for recurrent ischemic events in clopidogrel non-responders was 3.5 [95% confidence interval (CI) 2.4-5.2, P < 0.0001]. The results of the different studies were heterogeneous (Cochran P = 0.01 and I(2) = 52%). The most recent studies yielded lower RRs [global RR = 2.9 (95% CI 2.3-3.8) after 2007, and global RR = 6.6 (95% CI 3.7-11.9) before 2007, P = 0.01]. Heterogeneity was present in the group of studies in which more than 10% of patients took glycoprotein (GP)IIb-IIIa inhibitors [Cochran P = 0.003 and I(2) = 70%; RR = 3.8 (95% CI 2.9-5.1)] and was absent in the other studies [Cochran P = 0.88 and I(2) = 0; RR = 2.5 (95% CI 1.7-3.6)]. The RR was significantly higher in studies using higher ADP maximal aggregation cut-offs (> 65%) for clopidogrel non-response than in studies using lower cut-offs [RR = 5.8 (95% CI 3.2-10.3) and RR = 2.9 (95% CI 2.2-3.7), respectively, P = 0.03].

CONCLUSIONS

The risk of ischemic events associated with clopidogrel non-response is now more precisely defined. The risk is heterogeneous across studies, possibly because of an interaction with GPIIb-IIIa inhibitors and the use of different cut-offs to identify non-responders.

Effect of pharmaceutical interventions targeting thromboxane receptors and thromboxane synthase in cardiovascular and renal diseases

The present review focuses on the roles of thromboxane A2 (TxA2) in arterial thrombosis, atherogenesis, vascular stent-related ischemic events and renal proteinuria. Particular emphasis is laid on therapeutic interventions targeting the TxA2 (TP) receptors and TxA2 synthase (TS), including dual TP-receptor antagonists and TS inhibitors. Their significant inhibitory efficacies on arterial thrombogenesis, atherogenesis, restenosis after stent placement, vasoconstriction and proteinuria indicate novel and improved treatments for cardiovascular and selected renal diseases. New therapeutic interventions of the TxA2 pathway may also be beneficial for patients with poor biological antiplatelet drug response, for example, to aspirin and/or clopidogrel. These new TP/TS agents offer novel improved treatments to efficiently and simultaneously interfere with thrombogenesis and atherogenesis, and to enlarge the existing panel of platelet inhibitors for efficient prophylaxis and treatment of arterial thrombosis and renal proteinuria.

Ginkgo biloba extract enhances antiplatelet and antithrombotic effects of cilostazol without prolongation of bleeding time

Thrombosis and thromboembolic occlusions of major and minor blood vessels are a major complication in various peripheral vascular diseases. Antiplatelet agents (APA), key tools in the treatment of atherothrombosis, therefore became a mainstay medication for a wide range of vascular diseases. Cilostazol and Ginkgo biloba extract (GB), commonly used remedies for peripheral arterial disease, inhibit platelet aggregation with distinct therapeutic mechanisms. In this study, we have investigated if GB can potentiate the antiplatelet effects of cilostazol to explore the utility of combination therapy of cilostazol and GB against peripheral occlusive vascular diseases. GB or cilostazol was evaluated alone or in combination for the antiplatelet activity using in vitro and in vivo models. In addition, potential bleeding side effect of the combinative therapy was assessed by measuring bleeding time, prothrombin time (PT) and activated partial thromboplastin time (aPTT) in vivo after oral administration. In in vitro assays using freshly isolated human platelets, the combination of cilostazol and GB showed superior inhibition of both the shear and the collagen-induced platelet aggregation to those of each drug alone. In accordance with these enhanced in vitro antiplatelet activities, the combinative therapy showed enhanced anti-thrombotic effects in in vivo pulmonary embolism model and arterial thrombosis model. In particular, the increase of survival rate in pulmonary embolism model by combination treatment of cilostazol (25 mg/kg) and GB (20 mg/kg) was higher more than two-fold of those of the respective drugs. Notably, the combination of cilostazol and GB did not show a significant effect on the bleeding time, PT and aPTT increase, suggesting that GB may potentiate the antiplatelet effect of cilostazol without the prolongation of bleeding time or coagulation time. With these studies, we suggest that combinative therapy of GB and cilostazol might offer enhanced anti-thrombotic efficacies without increasing side-effects.

Use of the PFA-100 closure time to predict cardiovascular events in aspirin-treated cardiovascular patients: a systematic review and meta-analysis

BACKGROUND

PFA-100 is a point-of-care assay that evaluates platelet reactivity in high-shear-stress conditions by measuring the closure time (CT) of a membrane aperture. When determined with a collagen/epinephrine cartridge (CEPI), the CT is usually prolonged by aspirin. Studies of the predictive value of a short PFA-100CT(CEPI) for ischemic events in aspirin-treated patients have given variable results.

OBJECTIVES

To conduct a systematic review and meta-analysis of studies on the clinical predictive value of a short PFA-100CT(CEPI) in aspirin-treated cardiovascular patients.

PATIENTS AND METHODS

Relevant studies were identified by scanning electronic databases. Studies were selected if they included aspirin-treated patients with symptomatic atherosclerosis, measured the PFA-100CT(CEPI), used a CT cut-off value to define aspirin 'responders' and 'non-responders', and reported ischemic events.

RESULTS

We selected seven non-prospective studies (1466 patients) and eight prospective studies (1227 patients). In non-prospective studies, the PFA-100CT(CEPI) was performed after the ischemic clinical endpoint, and a publication bias was identified. In prospective studies, the global odds ratio (OR) for the recurrence of an ischemic event in 'aspirin non-responders' relative to 'aspirin responders' was 2.1 [95% confidence interval (CI) 1.4-3.4, P < 0.001]. Pooled analysis with a random effect model revealed no heterogeneity (Q Cochran P = 0.36 and I(2) = 9.4%).

CONCLUSIONS

A short PFA-100CT(CEPI) is associated with increased recurrence of ischemic events in aspirin-treated cardiovascular patients. This finding needs to be confirmed in stable ischemic patients, and the PFA-100CT(CEPI) cut-off needs to be refined in these patients.