Factors associated with the failure of clopidogrel dose-adjustment according to platelet reactivity monitoring to optimize P2Y12-ADP receptor blockade

Introduction

Inter-individual variability in clopidogrel responsiveness is dependent on genetic polymorphisms. We aimed to investigate the impact of 3 genetic polymorphisms involved in clopidogrel metabolism on a strategy of dose-adjustment according to platelet reactivity (PR) monitoring.

Materiel and methods

This prospective multicenter study enrolled 498 ACS patients undergoing PCI. PR was measured using the Vasodilator-Stimulated Phosphoprotein index (VASP) and a cut-off value of ≥ 50% defined high on-treatment platelet reactivity (HTPR). Genetic polymorphisms of cytochrome (CYP) 2C19, Paraxonase-1 (PON1) and ABCB1 were determined by allele specific PCR. Dose-adjustment was performed using up-to 3 additional loading doses (LD) of 600 mg clopidogrel in order to obtain a VASP < 50% in patients with HTPR following the first LD.

Results

CYP 2C19 2*polymorphism (p = 0.02), but neither PON1 (p = 0.8) nor ABCB1 genotype (p = 0.9), was significantly associated with HTPR. The dose-adjustment strategy failed in 11% of patients. ABCB1 polymorphism was significantly associated with a failed dose-adjustment (FDA) (p = 0.04). No relation was found between the other genotypes and the efficacy of LD adjustment. In multivariate analysis, BMI and ABCB1 polymorphism were the only factors significantly associated with FDA (p = 0.005 and p = 0.04 respectively).

Conclusion

While CYP 2C19 2* is associated with HTPR after 600 mg of clopidogrel, ABCB1 is responsible for the failure of a strategy of loading dose-adjustment according to PR monitoring. These findings may help to define a therapeutic strategy to optimize anti-platelet therapy in ACS patients undergoing PCI.     

Platelet reactivity evaluated with the VASP assay following ticagrelor loading dose in acute coronary syndrome patients undergoing percutaneous coronary intervention

Background

The level of platelet reactivity (PR) inhibition obtained after P2Y12-ADP receptor antagonist loading dose (LD) is associated with the ischemic and bleeding risk following percutaneous coronary intervention (PCI) in acute coronary syndromes (ACS).

Objective

We aimed to evaluate the level of PR inhibition achieved by a 180 mg LD of ticagrelor and the rate of high on-treatment platelet reactivity (HTPR) in ACS patients undergoing PCI.

Methods

We performed a multicentre prospective observational study enrolling ACS patients undergoing PCI. Patients were included if they were admitted for ST-elevation myocardial infarction or non ST-elevation ACS. To assess PR, a VASP index was measured at least 6 and within 24 hours following a 180 mg LD of ticagrelor. HTPR was defined as a VASP index ≥ 50%.

Results

One hundred and fifteen patients were included: 31.3% of STEMI, 49.6% of NSTEMI and 19.1% of unstable angina. Following ticagrelor LD the mean VASP index was 17 ± 14%. However the response to ticagrelor was not uniform with a small inter-individual variability: inter quartile range: 7.6–22.8% and a rate of HTPR of 3.5%. A high number of patients, 65.6%, had a VASP index < 16%. None of the baseline characteristics of the study population was associated with PR. In addition, PR was similar in STEMI, NSTEMI and unstable angina (p = 0.9).

Conclusion

In ACS patients the level of PR inhibition achieved by a 180 mg loading dose of ticagrelor is not uniform and the rate of HTPR is 3.5%. A high proportion of patients exhibited a VASP index < 16%.     

CYP2C19*2 and other genetic variants affecting platelet response to clopidogrel in patients undergoing percutaneous coronary intervention

Introduction

Information regarding any possible additional effect of genetic variants other than CYP2C19*2 on platelet reactivity in patients undergoing percutaneous coronary intervention (PCI), while on dual antiplatelet therapy, is sparse.

Materials and Methods

Genotyping for CYP2C19*2, CYP2C19*17, CYP2C9*3, CYP2B6*5, ABCB1 and P2RY12 (c.-217 + 2739 T > C) variants was performed in 146 consecutive PCI patients receiving clopidogrel. Platelet reactivity was assessed by the Verify Now P2Y12 point-of-care assay and high on-treatment platelet reactivity (HTPR) was defined as a Platelet Reactivity Unit (PRU) ≥ 235.

Results

We identified 65(44.5%) patients with HTPR and 38(26%) carriers of at least one CYP2C19*2 allele, which had higher platelet reactivity compared to non-carriers [least square (LS) mean difference 44.5, 95%CI 15.8-77.3, p = 0.003]. In the entire study population, the presence of at least one CYP2C19*2 or P2RY12 allelic variant was independently associated with HTPR (OR = 3.02, 95%CI 1.16-7.86, p = 0.023 and OR = 3.11, 95%CI 1.03-9.39, p = 0.05 respectively). In CYP2C19*2 non-carriers, carriers of at least one CYP2B6*5 allelic variant had higher platelet reactivity compared to the remainders (LS mean difference 35.6, 95%CI 3.7-67.6, p = 0.03) and the presence of at least one CYP2B6*5 or P2RY12 allelic variant was independently associated with HTPR (OR = 3.26, 95%CI 1.08-9.86, p = 0.04 and OR = 4.27, 95%CI 1.11-16.4, p = 0.04 respectively).

Conclusions

Apart from the CYP2C19*2, other genetic variants involved in clopidogrel metabolism and action like CYP2B6*5 and P2RY12 seem to have an important association with HTPR.     

Influence of cytochrome 2C19 allelic variants on on-treatment platelet reactivity evaluated by five different platelet function tests

Background

The antiplatelet effect of clopidogrel has been linked to cytochrome P450 2C19 (CYP2C19) carrier status. The presence of loss of function and gain of function variants were found to have a gene-dose effect on clopidogrel metabolism. However, genotyping is only one aspect of predicting response to clopidogrel and several platelet function tests are available to measure platelet response.Patients and methodsWe studied the influence of CYP2C19 allelic variants on on-treatment platelet reactivity as assessed by light transmission aggregometry (LTA), the VerifyNow P2Y12 assay, the VASP assay, multiple electrode aggregometry (MEA), and the Impact-R in 288 patients after stenting for cardiovascular disease. Allelic variants of CYP2C19 were determined with the Infiniti® CYP450 2C19 + assay and categorized into four metabolizer states (ultrarapid, extensive, intermediate, poor).

Results

Platelet reactivity increased linearly from ultrarapid to poor metabolizers using the VerifyNow P2Y12 assay (P = 0.04), the VASP assay (P = 0.02) and the Impact-R (P = 0.04). The proportion of patients with high on-treatment residual platelet reactivity (HRPR) identified by LTA, the VerifyNow P2Y12 assay and the VASP assay increased when the metabolizer status decreased, while no such relationship could be identified for results of MEA and Impact-R. The presence of loss of function variants (*2/*2, *2-8*/wt, *2/*17) was an independent predictor of HRPR in LTA and the VASP assay while it did not reach statistical significance in the VerifyNow P2Y12 assay, MEA, and the Impact-R.

Conclusion

Depending on the type of platelet function test differences in the association of on-treatment platelet reactivity with CYP2C19 carrier status are observed.     

Utility of whole blood impedance aggregometry for the assessment of clopidogrel action using the novel Multiplate analyzer--comparison with two flow cytometric methods

Background

Non-responsiveness to anti-platelet therapy has been reported and has been linked to the occurrence of adverse events. No standard method to monitor clopidogrel efficacy is available at present. We aimed at comparing the utility of whole blood impedance aggregometry for the assessment of clopidogrel action using the novel Multiplate® analyzer with two flow cytometric methods.

Methods

Platelet function was determined before and after the initiation of clopidogrel therapy (300 mg loading dose, followed by 75 mg qd) in 40 patients (observational study). Furthermore, 77 patients and 77 referents with and without clopidogrel treatment (75 mg qd) were evaluated (case control study). Platelet function was assessed by Multiplate® ADP and ADP + PG tests, by P-selectin (CD62P) expression, and by vasodilator stimulated phosphoprotein (VASP) phosphorylation status.

Results

The observational study revealed that platelet reactivity decreased significantly after clopidogrel administration with all 4 methods (p < 0.001 for each). In the case control study the median values of all 4 tests were significantly higher in the referents without clopidogrel treatment than in the patients on clopidogrel therapy (p < 0.001 for each). Applying test specific lower reference limits as criterion for the differentiation between responders and non-responders to clopidogrel treatment, 57% of the patients on clopidogrel therapy were classified as non-responders with the Multiplate® ADP test, 38% with the Multiplate® ADP + PG test, 55% with the P-selectin assay, 9% with the PLT VASP/P2Y12 assay.

Conclusions

The VASP phosphorylation assay appeared to be advantageous for the assessment of clopidogrel action compared to the Multiplate® ADP + PG test, the P-selectin assay, and the Multiplate® ADP test (listed in descending order). However, our method comparison study underscores the critical nature of the dependence of results on the techniques used in specific studies, and it remains to be elucidated which method correlates best with the occurrence of adverse events.     

P2Y12 platelet reactivity after thrombolytic therapy for ST-segment elevation myocardial infarction

Introduction

Thrombolysis, as reperfusion therapy for ST segment elevation myocardial infarction (STEMI), induces a pro-thrombotic status with enhanced platelet activity; this study aims to evaluate P2Y12 platelet reactivity and response to clopidogrel in the post-thrombolysis scenario.

Materials and Methods

Observational, prospective study, including consecutive patients with elective angiography after thrombolytic therapy for STEMI. Every patient received antiplatelet therapy with loading doses of 250 mg aspirin and 300 mg clopidogrel on admission followed by 100 mg aspirin and 75 mg clopidogrel daily. P2Y12-dependent platelet reactivity (expressed in P2Y12-Reaction Units, PRU) was assessed with VerifyNow® device on admission, daily after thrombolysis and pre-angiography.

Results

41 patients fulfilled the inclusion criteria. Median time between thrombolysis and angiography was 2,5 days (IQR 1,8-4,1). Post-treatment platelet reactivity (PPR) showed poor correlation with time on clopidogrel treatment (r2 = 0.04) and reached a maximum value of 274 ± 84 PRU during the first 24 h after thrombolysis (Day + 1 determination). After this, values showed a progressive reduction until the point of angiography (249 ± 82 PRU), without significant differences between consecutive time-points (p = 0,549).Inhibition of platelet aggregation (IPA) assessed as a percentage of P2Y12 receptor blockage was poor, increasing gradually from 0 ± 4% on admission to 11 ± 6% the day of the angiography (p = 0,001). 71,4% of patients showed PPR ≥ 208 PRU during angiography.

Conclusions

Platelet reactivity, as assessed by post-treatment P2Y12 mediated reactivity, is heightened after thrombolytic therapy during STEMI management. In this scenario, standard doses of clopidogrel did not achieve significant inhibition of ADP-mediated platelet reactivity.     

A randomised study comparing the antiplatelet and antinflammatory effect of clopidogrel 150 mg/day versus 75 mg/day in patients with ST-segment elevation acute myocardial infarction and poor responsiveness to clopidogrel: Results from the DOUBLE study

Introduction

The antiplatelet effect of standard or increased clopidogrel doses in patients with ST- segment elevation acute myocardial infarction (STEMI) has never been studied. In this study we compared the antiplatelet effect of a 75 mg daily maintenance dose of clopidogrel with 150 mg in patients with STEMI undergoing primary percutaneous coronary intervention (PCI).

Materials and methods

Fifty-four patients with STEMI undergoing PCI were randomly allocated to receive either 75 mg/day clopidogrel (group 1) or 150 mg/day (group 2) for 1 month. Platelet function, measured by 5 different assays, was determined at 3 time points: 38 ± 8 hours after the procedure, 1 week and 1 month after randomization.

Results

In group 1, mean ± SD platelet reactivity index (PRI) measured with the VASP assay was 57.7 ± 15.7% and 46.9 ± 15.7% at 1 week and 1 month, respectively, compared to 38.8 ± 15.7% and 34.9 ± 12.6% in group 2 (p = 0.0001). Same results were observed for light transmittance aggregometry, whole blood aggregometry and VerifyNow, but not for thromboelastometry. In contrast to what may be expected, the 75 mg daily maintenance dose took longer than 1-week to provide the full clopidogrel antiplatelet effect. Furthermore, patients in group 2 had a nearly 50% reduction in C-reactive protein levels both at 1 week and 1 month.

Conclusion

In patients with STEMI and poor responsiveness to clopidogrel a 150 mg daily maintenance dose of clopidogrel is associated with a significant reduction of platelet aggregation and a trend towards reduced inflammation.     

Baseline platelet size is increased in patients with acute coronary syndromes developing early stent thrombosis and predicts future residual platelet reactivity. A case-control study

Introduction

Pre-procedural predictors of early stent thrombosis (ST) and future response to platelet inhibitors are in demand. We sought to evaluate the impact of baseline platelet indices on the occurrence of early ST and future residual platelet reactivity.

Materials and methods

Hundred and eight patients with acute coronary syndromes (ACS) in whom stents were implanted were included: 36 consecutive ST cases and 72 matched controls. Platelet indices assessed with flow cytometry before stent implantation were retrieved from the department's data base. Residual platelet reactivity specific to aspirin (aspirin reaction units-ARU) and clopidogrel (P2Y12 reaction units-PRU) was assessed prospectively with VerifyNow^® under dual antiplatelet treatment.

Results

Platelet size reported as mean platelet volume (MPV) or proportion of large platelets (LPLT) was significantly higher in ST cases compared with controls (10.4, 95% confidence intervals [CI], 10.1-10.8 vs. 9.7, CI, 9.5-9.9, P = 0.0004 and 35.8, CI, 34.2-37.3 vs. 33.3, CI, 32.2-34.3, P = 0.007, respectively). Dual aspirin and clopidogrel poor-responsiveness was diagnosed significantly more often in ST cases than in controls (19.6% vs. 1.4%, P = 0.004), whereas no difference was observed for single aspirin or clopidogrel poor-responsiveness. A strong correlation was found between MPV and both, ARU (r = 0.66, P < 0.0001) and PRU (r = 0.55, P < 0.0001). Similarly, higher LPLT was associated with higher ARU (r = 0.47, P < 0.0001) and PRU (r = 0.38, P = 0.0001).

Conclusions

Baseline platelet size is increased in patients with ACS developing early ST and correlates with future residual platelet reactivity under aspirin and clopidogrel therapy. Dual but not isolated aspirin or clopidogrel poor-responsiveness appears to be associated with early ST.     

Doubling the dose of clopidogrel restores the loss of antiplatelet effect induced by esomeprazole

Introduction

Concerns have been raised about the potential adverse interaction between clopidogrel and PPIs. We studied the impact of esomeprazole and ranitidine on the antiplatelet action of clopidogrel and aspirin and sought to determine whether doubling the dose of clopidogrel could restore its efficacy.

Materials and methods

In a randomized prospective crossover study, we tested platelet reactivity to aspirin and clopidogrel (75 and 150 mg) with and without esomeprazole or ranitidine using the VerifyNow system (Accumetrics Inc, San Diego, CA, USA) in 4 stages, each lasting 7 days: T1, 160 mg aspirin and 75 mg clopidogrel; T2 : 160 mg aspirin + 75 mg clopidogrel + 20 mg esomeprazole, T3 : 160 mg aspirin + 150 mg clopidogrel + 20 mg esomeprazole and T4 : 160 mg aspirin + 75 mg clopidogrel + 150 mg ranitidine. Results are expressed in P2Y12 Reaction Units (PRU%) and Aspirin Reaction Units (ARU).

Results

In 21 patients with stable coronary artery disease, esomeprazole reduced the effect of clopidogrel with a 38.6% ± 24 loss in PRU% (p < 0.001) (absolute mean difference − 16.7 PRU% [− 21;− 12.5]), increasing 8-fold the prevalence of low responders to clopidogrel (defined as patients with PRU% below 20%). Doubling clopidogrel dosage to 150 mg restored the basal response. Ranitidine did not modify the antiplatelet effect of clopidogrel.

Conclusion

Our study demonstrates a strong negative clopidogrel/esomeprazole interaction, compensated by increasing the dose of clopidogrel to 150 mg or replacing esomeprazole with ranitidine. That could offer a simple solution to the PPI-induced clopidogrel resistance.     

Pharmacodynamic assessment of a novel P2Y12 receptor antagonist in Japanese patients with coronary artery disease undergoing elective percutaneous coronary intervention

Introduction

Numerous reports have shown that prasugrel shows a rapid and consistent antiplatelet effect among European and US patients. Previous studies suggest that prasugrel might be expected to achieve an adequate antiplatelet effect in healthy Asian subjects, even at lower doses than those assessed in the TRITON-TIMI 38 study. In this study, the antiplatelet effect of prasugrel was evaluated in Japanese coronary artery disease (CAD) patients undergoing percutaneous coronary intervention (PCI).

Methods and results

Eighty-four patients were randomized into four treatment groups: prasugrel 10/2.5 mg (loading dose [LD]/maintenance dose [MD]), 15/3.75 mg or 20/5 mg, and clopidogrel 300/75 mg. The LD of each regimen was administered the day before PCI, followed by 28-day MD on aspirin background therapy (81-100 mg). Antiplatelet effects were evaluated by light transmission aggregometry and VASP assay.The mean inhibition of platelet aggregation (IPA) induced by 20 μM of adenosine diphosphate at 4 hours after LD was higher among the prasugrel 10/2.5 mg, 15/3.75 mg and 20/5 mg groups compared with the clopidogrel group (12.3%, 20.9%, 29.8% vs. 8.4%, respectively). The proportion of subjects with an IPA of < 10% on Day 28 was lower among the prasugrel 15/3.75 mg, and 20/5 mg groups than in the clopidogrel group (0%, 6.3% vs. 15.8%, respectively). No “major” or “clinically relevant non-major” bleeding was observed.

Conclusions

Prasugrel 15 mg LD/3.75 mg MD or higher doses was well tolerated and achieved a more rapid, higher and consistent antiplatelet effect than clopidogrel in Japanese CAD patients undergoing PCI.     

Relationship between aspirin and clopidogrel responses in acute coronary syndrome and clinical predictors of non response

Objectives

We have prospectively investigated the association between aspirin and clopidogrel responses and the clinical predictors of non response.

Methods

635 Non ST Elevation Acute Coronary Syndrome (NSTE ACS) patients were included and received loading doses of 250 mg aspirin and 600 mg clopidogrel. We analyzed post-treatment maximal intensity of arachidonic acid and ADP-induced platelet aggregation (AA-Ag and ADP-Ag) and Platelet Reactivity Index of VAsodilator-Stimulated Phosphoprotein (PRI VASP). Aspirin and clopidogrel non responses were defined respectively by AA-Ag > 30% and ADP-Ag > 70%.

Results

Aspirin non responders patients had significantly higher ADP-Ag and PRI VASP than aspirin responders: 63.7 ± 15.9% vs 55 ± 19% (p = 0.0001) and 73.6 ± 13.3% vs 53 ±23% (p = 0.0001) respectively and the rate of clopidogrel non responders was higher among aspirin non responders than aspirin responders: 36.7% vs 22.7% (p = 0.003). In addition, clopidogrel non responders had significantly higher AA-Ag and rate of aspirin non responders than clopidogrel responders: 21.6 ± 24% vs 10.3 ± 19% (p = 0.0001) and 22.8% vs 12.9% (p = 0.003) respectively. Age and Body Mass Index (BMI) were significantly associated with non response to Clopidogrel (p = 0.035 and 0.02 respectively) and diabetes mellitus by trend (p = 0.07).

Conclusion

We observed a relationship between aspirin and clopidogrel non responses and an association between age, BMI and diabetes mellitus and clopidogrel response.     

The influence of body size on the pharmacodynamic and pharmacokinetic response to clopidogrel and prasugrel: A retrospective analysis of the FEATHER study

Introduction

Patients treated with clopidogrel who have higher body size exhibit greater platelet reactivity than patients with lower body size. In a retrospective analysis of the FEATHER trial, we examined the relationship between platelet response to thienopyridines clopidogrel 75 mg (Clop-75), prasugrel 5 mg (Pras-5), and prasugrel 10 mg (Pras-10) using 3 body size indices: body weight (BW), body mass index (BMI), and body surface area (BSA). Relationships were assessed as continuous variables and as 4 incremental body size groups.

Materials and Methods

Aspirin-treated patients with stable coronary artery disease (N = 72) and a BW range of 45-134 kg received Clop-75, Pras-5, and Pras-10 in a 3-period, blinded, cross-over study. Platelet assays included maximum platelet aggregation (MPA) to 20 μM ADP by light transmission aggregometry, VerifyNow-P2Y12 reaction units (PRU), and vasodilator-associated stimulated phosphoprotein (VASP) phosphorylation platelet reactivity index (PRI). Exposure to active metabolites (AMs) was also assessed.

Results

Body size was a determinant of AM exposure and residual platelet reactivity regardless of type and dose of thienopyridine. BW and BSA demonstrated marginally stronger correlations with platelet reactivity; VASP-PRI demonstrated a stronger correlation with the body size than the other tests. Correlation coefficients ranged from a high of 0.64 (BW vs. PRI on Pras-5) to a low of 0.34 (BMI vs. MPA on Pras-10), but all were statistically significant (p < 0.01).

Conclusions

Using a comprehensive selection of body size indices, AM exposures, platelet function tests, and thienopyridine doses, we demonstrated a consistent inverse relationship between body size and response to clopidogrel and prasugrel.     

Gender differences in the effects of peroxisome proliferator-activated receptor γ2 gene polymorphisms on metabolic adversity in patients with schizophrenia or schizoaffective disorder

Objective

Metabolic syndrome (MS) is a major health problem in schizophrenic patients. Peroxisome proliferator-activated receptor γ2 (PPARγ2) is one of the candidate genes responsible for the liability to metabolic problems. In this study, we investigated the effect of the PPARγ2 gene Pro12Ala and C161T polymorphisms on metabolic adversities in patients with schizophrenia or schizoaffective disorder.

Methods

Metabolic profiles and PPARγ2 gene polymorphisms were determined in 600 patients (309 men and 291 women) with a clinical diagnosis of schizophrenia or schizoaffective disorder. Metabolic indices and components of MS were compared between patients with different Pro12Ala or C161T genotypes.

Results

In the whole population, the allele frequency of 12Ala and 161T was 4.4% and 24.7% respectively. Both polymorphisms had no significant effect on obesity or metabolic-related traits. However, following gender stratification of the data, we found female 12Ala allele carriers were at greater risk of developing abdominal obesity (OR = 4.0, 95% CI = 1.1-14.2, p = 0.04) and hypertension (OR = 2.9, 95% CI = 1.2-7.4, p = 0.02) than female 12Ala allele non-carriers. Male 161T allele carriers had lower insulin levels (p = 0.02) and lower high-density lipoprotein cholesterol (HDL-C) (p = 0.05) levels than male 161T allele non-carriers. Moreover, female 161T allele carriers had higher body weight (p = 0.04), waist circumference (p = 0.05), and systolic blood pressure (p = 0.01), and were at greater risk of developing hypertension (OR = 2.0, 95% CI = 1.1-3.5, p = 0.02). Haplotype analyses showed that PPARγ2 gene polymorphisms were significantly associated with HDL-C level in men and blood pressure in women.

Conclusions

We did not find an association of PPARγ2 gene polymorphisms with MS or obesity in our schizophrenia sample. But further analyses by gender stratification revealed gender-specific differences in the effect of different PPARγ2 genotypes on certain metabolic adversities in these patients.     

Response to antiplatelet therapy is independent of endogenous thrombin generation potential

Background

Thrombin is the most potent platelet activator, and achieves rapid platelet activation even in the presence of antiplatelet therapy. Since activated platelets respond stronger to additional stimuli, the extent of endogenous thrombin generation may in part be responsible for the reported response variability to aspirin and clopidogrel therapy.

Patients and methods

Thrombin generation potential was measured with a commercially available assay, and platelet reactivity was assessed with the vasodilator-stimulated phosphoprotein (VASP) phosphorylation assay, light transmission aggregometry (LTA), the VerifyNow aspirin and P2Y12 assays, and multiple electrode aggregometry (MEA) in 316 patients on dual antiplatelet therapy undergoing angioplasty and stenting.

Results

Peak thrombin, the lag phase and the area under the curve of thrombin generation correlated poorly with on-treatment platelet reactivity by all test systems. High on-treatment residual platelet reactivity (HRPR) in response to arachidonic acid was seen in 33 (10.5%), 41 (13%), and 79 (25.7%) patients by LTA, the VerifyNow aspirin assay, and MEA, respectively. HRPR in response to adenosine diphosphate was seen in 150 (48.1%), 48 (15.3%), 106 (33.7%), and 118 (38.3%) patients by the VASP assay, LTA, the VerifyNow P2Y12 assay, and MEA, respectively. Peak thrombin generation did not differ between patients without and with HRPR by the VASP assay, LTA, the VerifyNow P2Y12 assay and MEA. In the VerifyNow aspirin assay, patients without HRPR had higher peak thrombin generation than patients with HRPR (p = 0.01). Finally, patients without and with high peak thrombin generation exhibited similar on-treatment platelet reactivity by all test systems, and high peak thrombin generation occurred to a similar extent in patients without and with HRPR.

Conclusion

Response to antiplatelet therapy with aspirin and clopidogrel is not associated with thrombin generation potential.     

Multi-parameter assessment of platelet inhibition and its stability during aspirin and clopidogrel therapy

Introduction

Poor response to antiplatelet drugs is associated with adverse outcomes. We assessed platelet inhibition and its stability and tested correlation and agreement between platelet function assays.

Methods

Peripheral blood from 58 patients on both aspirin and clopidogrel who underwent percutaneous coronary intervention (PCI) was collected at hospital discharge (visit-1) and at 30-90 days (visit-2). Platelet function was measured using light transmission aggregometry (LTA-AA and LTA-ADP), VerifyNow® (Aspirin; ARU and P2Y12; PRU), ex vivo TxB₂, urinary 11dhTxB₂, and VASP (PRI) assays. Data were analyzed as continuous, quartiles and binary. Patients were defined as aspirin poor responder (PR) with ARU ≥ 550, LTA-AA maximum ≥ 20%, TxB₂ ≥ 1 ng/mL or 11dhTxB₂ ≥ 1,500 pg/mg of creatinine and as clopidogrel PR with PRU ≥ 240, PRU ≥ 208, LTA-ADP maximum ≥ 40%, PRI ≥ 50%, or PRI ≥ 66%.

Results

Aspirin PR was 3-33% and clopidogrel PR was 10-35% in visit-1. LTA-AA, 11dhTxB_2, and all clopidogrel-response measures showed correlation and agreement between visit-1 and visit-2. The highest agreement between two visits was revealed by PRU ≥ 240 and PRI ≥ 66% (PRU-κ = 0.7, 95% CI = 0.47, 0.93; PRI-κ = 0.69, 95% CI = 0.42, 0.95, p-values < 0.001). Comparison of platelet function assays in a single visit (visit-1) revealed a poor correlation between LTA-AA and 11dhTxB₂ assays and no agreement among aspirin-response assays. The highest correlation and agreement were obtained between VerifyNow® P2Y12 and VASP assays (rho = 0.7, p-value < 0.001 and PRU ≥ 208-PRI-κ = 0.41-0.42, 95% CI = 0.13, 0.69, p-values < 0.001).

Conclusions

Platelet inhibition is stable during aspirin and clopidogrel treatment. Clopidogrel-response assays correlate and agree with each other better than aspirin-response assays.     

Genetic and non-genetic factors responsible for antiplatelet effects of clopidogrel in Japanese patients undergoing coronary stent implantation: An algorithm to predict on-clopidogrel platelet reactivity

Introduction

Antiplatelet effects of clopidogrel appear to be affected by various factors including genetic polymorphism. So far, there has been little information about the response of clopidogrel in Asians, whose prevalence of a CYP2C19 loss-of-function (LOF) allele is high.

Methods and Results

We investigated background and clinical factors affecting on-clopidogrel platelet reactivity in Japanese patients undergoing coronary stent implantation (n = 114). In univariate analysis, antiplatelet effects of clopidogrel in a steady state were associated with not only CYP2C19 genotypes but also several factors including dyslipidemia. In addition, we developed an algorithm that can estimate P2Y12 Reaction Units (PRU) in a steady state by multiple regression analysis and evaluated the adequacy of the algorithm by the Akaike Information Criterion.

Conclusions

We revealed several factors influencing on-clopidogrel platelet reactivity in Japanese patients. We also succeeded in developing an algorithm that estimates PRU in a steady state, although it is uncertain whether the algorithm can be applied to other populations.     

Evaluation of ticagrelor pharmacodynamic interactions with reversibly binding or non-reversibly binding P2Y(12) antagonists in an ex-vivo canine model

Introduction

As ticagrelor, clopidogrel and cangrelor therapies may be used in the same clinical setting, their potential pharmacodynamic interactions are of interest. Hence, we investigated possible interactions between these agents in dogs using a variety of switching protocols.

Methods

Six male dogs all received 7 different dosing regimens separated by 1-5 week washout periods: cangrelor (1 μg/kg/min, intravenous infusion); ticagrelor (0.8 mg/kg, oral); clopidogrel (3 mg/kg, intravenous injection); cangrelor together with ticagrelor initiated 10 minutes after cangrelor infusion start or clopidogrel given 30 minutes after cangrelor infusion start; ticagrelor followed by clopidogrel given 3 or 7 hours after ticagrelor dosing. ADP-induced whole blood platelet aggregation was measured by impedance aggregometry.

Results

Mean maximum inhibition of platelet aggregation (IPA) was 81-87% at 6 minutes (cangrelor), 3 hours (ticagrelor) and 4 hours (clopidogrel) postdosing and platelet function recovered after 1.5 hours, 12 hours, and 9 days, respectively. IPA at 2 hours post clopidogrel was reduced to 39% when clopidogrel was given during cangrelor infusion versus 69% for clopidogrel alone. With clopidogrel dosed 3 hours after ticagrelor, IPA was reduced after washout of ticagrelor to 38% at 24 hrs vs. 68% for clopidogrel alone, but an interaction was not seen when clopidogrel was dosed 7 hours after ticagrelor. No pharmacodynamic interaction occurred between ticagrelor and cangrelor.

Conclusions

The extent of the pharmacodynamic drug-drug interactions observed between clopidogrel and cangrelor or ticagrelor apparently depends on the level of receptor occupancy when clopidogrel is administered. Importantly, no significant pharmacodynamic interaction occurred between ticagrelor/clopidogrel when clopidogrel was given at clinical trough IPA levels with ticagrelor. No significant pharmacodynamic interaction occurred with cangrelor and ticagrelor.     

A case-control study provides evidence of association for a common SNP rs974819 in PDGFD to coronary heart disease and suggests a sex-dependent effect

Introduction

Peden et al. have revealed a significant association between four new risk loci and coronary heart disease (CHD) in Europeans and South Asians. The goal of this study is to evaluate the contribution of these genetic loci to CHD risk in Han Chinese.

Methods

We recruited 161 CHD patients and 112 controls proved by angiography originated from Ningbo in the Eastern China, and performed a case-control association study of the four significant SNPs.

Results

Among the four tested SNPs, we found a significant association of rs974819 in PDGFD gene with CHD (allele p = 0.04; OR = 1.45, 95% CI = 1.02 - 2.08) and the allele A/G of rs974819 shows significant difference in females (allele p = 0.04; OR = 1.83, 95% CI = 1.01 - 3.31). A further meta-analysis showed that rs974819 of PDGFD gene was significantly associated with an increasing risk of CHD (OR = 1.08, 95% CI = 1.05 - 1.11) in both Europeans and South Asians including Han Chinese.

Conclusions

Our findings suggests that rs974819 of PDGFD is also a CHD risk factor in Han Chinese. In addition, it presents a sex-dependent genetic effect.     

ABCB1 C3435T polymorphism and risk of adverse clinical events in clopidogrel treated patients: a meta-analysis

Introduction

The ABCB1 C3435T polymorphism limits oral bioavailability of clopidogrel and may influence prognosis of patients treated with clopidogrel. Several studies have examined the association between the C3435T polymorphism and risk of adverse clinical events in clopidogrel treated patients, but the results were inconsistent. To assess the role of the C3435T polymorphism in the impact on clinical outcomes, a meta-analysis was conducted.

Methods

6 studies with 10,153 subjects were included in this meta-analysis. Fixed- or random-effects model was chosen according to heterogeneity. Publication bias was evaluated by fail-safe numbers.

Results

The association of the C3435T polymorphism with risk of overall recurrent ischemic events in clopidogrel treated patients was not statistically significant for all genetic models (OR = 1.13, 95%CI: 0.78-1.64, P = 0.51; OR = 1.15, 95%CI: 0.99-1.33, P = 0.07; OR = 1.19, 95%CI: 0.81-1.76, P = 0.37). Significant association was identified between the C3435T polymorphism and risk of short-term recurrent ischemic events (OR = 1.55, 95% CI: 1.09-2.20, P = 0.01; OR = 1.41, 95% CI: 1.06-1.87, P = 0.02; OR = 1.77, 95% CI: 1.19-2.63, P = 0.005). No statistically significant association between the C3435T polymorphism and stent thrombosis (OR = 0.79, 95% CI: 0.47-1.32, P = 0.37) or bleeding (OR = 0.98, 95% CI: 0.79-1.21, P = 0.82) was identified. The results may be affected by publication bias.

Conclusions

This meta-analysis failed to show an association between the ABCB1 C3435T polymorphism and risk of overall recurrent ischemic events, stent thrombosis or bleeding in clopidogrel treated patients. However, the association between TT homozygotes of the C3435T polymorphism and risk of short-term recurrent ischemic events may exist, but needs more studies to confirm.