Prevalence Of High On-treatment Platelet Reactivity Research Articles

Pharmacodynamic Effect of Switching Therapy in Patients With High On-Treatment Platelet Reactivity and Genotype Variation With High Clopidogrel Dose Versus Prasugrel

High on-treatment platelet reactivity (HTPR) is associated with adverse outcomes. We aim to compare the novel thienopyridine prasugrel versus double-dose clopidogrel in patients with HTPR and explore the interaction between CYP2C19 genotype and both drugs. Consecutive stable patients undergoing percutaneous coronary intervention were screened with the Multiplate Analyzer P2Y12 assay, defining HTPR as area under the curve >450. Those with HTPR were randomized to prasugrel (10 mg/day) or high-dose clopidogrel (150 mg/day) for 2 weeks and then crossed-over to, respectively, clopidogrel and prasugrel, repeating the P2Y12 assay at the end of each cycle. Clinical follow-up (until 3 months) and CYP2C19 genotyping was performed in all patients. The primary end point was platelet reactivity after 14 days of prasugrel versus high-dose clopidogrel. Thirty-two patients were randomized to prasugrel and then high-dose clopidogrel or to high-dose clopidogrel followed by prasugrel. Prasugrel was associated with a significantly lower platelet reactivity than high-dose clopidogrel was (325.8 versus 478.5 area under the curve, P=0.028). No patient treated with prasugrel exhibited HTPR, whereas 9 (28.1%) receiving high-dose clopidogrel still had prevalence of HTPR (P=0.001). Similar findings were obtained changing cutoffs or considering platelet reactivity as a continuous variable. Genotyping showed the same efficacy between high-dose clopidogrel and prasugrel in the 18 (56.3%) CYP2C19*2 noncarriers (HTPR in 12.5% versus 0, P=0.274), whereas it was significantly worse in the 14 (43.7%) carriers (HTPR in 43.7% versus 0, P=0.003). HTPR is successfully abolished by therapy with prasugrel irrespective of CYP2C19 genotype. Conversely, high-dose clopidogrel can address HTPR only in CYP2C19*2 noncarriers. URL: http://www.clinicaltrials.gov. Unique identifier: NCT01465828.

Accelerated platelet inhibition by switching from atorvastatin to a non-CYP3A4-metabolized statin in patients with high platelet reactivity (ACCEL-STATIN) study

CYP3A4-metabolized statins can influence the pharmacodynamic effect of clopidogrel. We sought to assess the impact of switching to a non-CYP3A4-metabolized statin on platelet function among patients receiving clopidogrel and atorvastatin with high on-treatment platelet reactivity (HPR). Percutaneous coronary intervention (PCI)-treated patients (n= 50) with HPR [20 μM adenosine diphosphate (ADP)-induced maximal platelet aggregation (MPA) >50%] were enrolled during chronic administration of atorvastatin (10 mg/day) and clopidogrel (75 mg/day) (≥6 months). They were randomly assigned to a 15-day therapy with either rosuvastatin 10 mg/day (n= 25) or pravastatin 20 mg/day (n= 25). Platelet function was assessed before and after switching by conventional aggregometry and the VerifyNow P2Y12 assay. Genotyping was performed for CYP2C19*2/*3, CYP3A5*3, and ABCB1 C3435T alleles. The primary endpoint was the absolute change in 20 μM ADP-induced MPA. After switching, MPAs after stimuli with 20 and 5 μM ADP were decreased by 6.6% (95% confidence interval: 3.2-10.1%; P < 0.001), and 6.3% (95% confidence interval: 2.5-10.2%; P = 0.002), respectively. Fifty-two P2Y12 reaction units fell (95% confidence interval: 35-70; P < 0.001) and the prevalence of HPR decreased (24%; P < 0.001). Pharmacodynamic effects were similar after rosuvastatin and pravastatin therapy. In addition to smoking status, the combination of calcium channel blocker usage and ABCB1 C3435T genotype significantly affected the change of 20 μM ADP-induced MPA. Among PCI-treated patients with HPR during co-administration of clopidogrel and atorvastatin, switching to a non-CYP3A4-metabolized statin can significantly decrease platelet reactivity and the prevalence of HPR. This switching effect appears similar irrespective of the type of non-CYP3A4-metabolized statin.

Platelet Function Testing and Genotyping Improve Outcome in Patients Treated With Antithrombotic Agents

The only reason P2Y12 inhibitors are administered in addition to aspirin is to improve the prevention of thrombosis. The clinical efficacy of adding clopidogrel to aspirin as a secondary prevention strategy in patients with high-risk coronary artery disease is well established.1 There are no effects of clopidogrel on any receptor other than P2Y12 to explain the magnitude of the clinical benefit. All of the established clinical effects are attributed to reduced platelet responsiveness to ADP.2 Therefore, the patient with inadequate P2Y12 inhibition determined by ex vivo testing logically has an increased risk for thrombosis. Persistent ischemic event occurrence and the irrefutable demonstration of clopidogrel antiplatelet response variability are 2 potent arguments against the widely practiced nonselective or one-size-fits-all strategy of administering clopidogrel therapy. Observational studies conducted in thousands of patients have led to an international consensus that high on-treatment platelet reactivity (HPR) to ADP is a major risk factor for post–percutaneous coronary intervention (PCI) ischemic event occurrence.3,4 Moreover, the recent 2011 American and European guidelines have given a Class IIb recommendation for platelet function testing or genotyping if the results of testing may alter management.5–7 Furthermore, the Society of Thoracic Surgeons gave a Class IIb recommendation for platelet function testing to determine the timing of surgery in patients on clopidogrel therapy (Level of Evidence C).8 These recommendations for personalizing antiplatelet therapy are unprecedented and acknowledge that a large body of data has accrued demonstrating the relation of HPR to ischemic risk in the PCI-treated patient. Finally, the evidence of diminished effectiveness of clopidogrel in poor metabolizers (those having 2 loss-of-function [LoF] cytochrome P450 [ CYP ] 2C19 alleles) has been recognized by the Food and Drug Administration (FDA) boxed warning about treatment with clopidogrel.9 Response by Krishna …

Interaction analysis between genetic polymorphisms and pharmacodynamic effect in patients treated with adjunctive cilostazol to dual antiplatelet therapy: results of the ACCEL‐TRIPLE (Accelerated Platelet Inhibition by Triple Antiplatelet Therapy According to Gene Polymorphism) study

Compared with standard dual antiplatelet therapy, adjunctive cilostazol to dual antiplatelet therapy ('triple antiplatelet therapy') has a potential to reduce ischemic event occurrence after percutaneous coronary intervention. The pharmacokinetic and pharmacodynamic effects of clopidogrel have been significantly influenced by the enzyme activity of the ABCB1 C3435T and the CYP2C19 system. • For the pharmacokinetics of cilostazol, genetic polymorphisms of the CYP3A5 and CYP2C19 have been associated with the substantial interindividual variability in healthy volunteers. Loss-of-function polymorphism of the CYP2C19 gene, but not the ABCB1 C3435T and CYP3A5*3 genes, affects the antiplatelet effect of triple antiplatelet therapy. Most of extensive and intermediate East Asian metabolizers (0 or 1 CYP2C19 loss-of-function allele) show adequate platelet inhibition when treated with triple antiplatelet therapy after percutaneous coronary intervention. However, carriage of 2 CYP2C19 loss-of-function alleles is still associated with the risk of high platelet reactivity (defined by by 5 µM ADP-induced maximal platelet aggregation >46%), which clinical impact needs to be validated in future clinical trials. AIMS Although adjunctive cilostazol to dual antiplatelet therapy can reduce the risks of clinical events after percutaneous coronary intervention (PCI), whether genetic polymorphism can influence the pharmacodynamics of this regimen has not been evaluated. One hundred and twenty-seven patients treated with PCI and taking triple antiplatelet therapy (≥1 month) were enrolled. Platelet reactivity was assessed by conventional aggregometry and the VerifyNow P2Y12 assay. High on-treatment platelet reactivity (HPR) was defined as 5 µm ADP-induced maximal platelet reactivity (Agg(max) ) >46%. CYP3A5*3, CYP2C19*2/*3 and ABCB1 3435C > T were genotyped. CYP3A5*3 and ABCB1 3435C > T variants did not affect the antiplatelet effect of triple antiplatelet therapy. For non-carriers, one and two carriers of the CYP2C19 loss-of-function (LOF) allele, Agg(max) consecutively increased after the addition of 5 µm[mean (95% confidence intervals): 24.6% (20.8 to 28.5%) vs. 28.7% (25.4 to 32.0%) vs. 32.3% (25.8 to 38.7%), P = 0.062, respectively] and 20 µm ADP [34.2% (29.3 to 39.0%) vs. 41.7% (37.8 to 45.6%) vs. 44.9% (37.9 to 51.9%), P = 0.007, respectively]. Likewise, late platelet reactivity and P2Y12 reaction units proportionally changed according to the number of CYP2C19 LOF alleles. HPRs were observed in 9.2% of subjects: 6.3%, 7.4% and 20.0% with 0, 1 and 2 carriers of CYP2C19 LOF allele(s) (P = 0.099). In multivariate analysis, carriage of two CYP2C19 LOF alleles was a significant predictor for the prevalence of HPR (odds ratio 5.78, 95% CI 1.21, 27.78, P = 0.028). Among PCI-treated patients, the effect of triple antiplatelet therapy is influenced by the CYP2C19 LOF allele. Its clinical benefit needs to be validated according to the CYP2C19 metabolic phenotype in future clinical trials. [Adjunctive Cilostazol Versus High Maintenance dose ClopidogrEL in Acute Myocardial Infarction Patients According to CYP2C19 Polymorphism (ACCEL-AMI-2C19), NCT00915733 and Adjunctive Cilostazol Versus High Maintenance-dose Clopidogrel According to Cytochrome 2C19 Polymorphism (ACCEL-2C19), NCT01012193].

Abstract 18022: High On-Treatment Platelet Reactivity Measured by Various Platelet Function Tests: Is the Current VASP-PRI Cutoff Too Low?

Background: High on-treatment platelet reactivity (HPR) to ADP measured by multiple methods has been linked to adverse post-PCI clinical event occurrence. The correlation of HPR cutoffs is still a matter of debate, since the predictive value and HPR group size are different depending on platelet function assays. To determine the comparable cutpoint, we correlated cutpoints for HPR determined by various assays in the same patient cohort. Methods: Platelet measures [5µM ADP-induced light transmission aggregation (LTA5μ MADP); P2Y12 reaction units by VerifyNow (PRU), and platelet reactivity index by VASP assay (PRI)] were evaluated (n=936 pairs, cohort I) in stable CAD patients during P2Y12 receptor inhibitor treatment. These assays also performed in PCI-treated patients receiving standard aspirin and clopidogrel therapy (n=584, cohort II). The HPR cutpoints were defined as LTA 5μ MADP &gt;46%, PRU &gt;235, and PRI &gt;50%. Results: In the stable CAD patients, LTA 5μ MADP showed significant correlations with PRU and PRI (r ≥0.688). In ROC curve analysis using the cutpoint of LTA 5μ MADP (&gt;46%), the matched values of PRU and PRI were &gt;234 (AUC 0.943, p&lt;0.001, sensitivity 87.3% and specificity 87.8%) and &gt;60% (Figure A). Among PCI-treated patients, the prevalence of HPR was highest based on PRI &gt;50% (69%) compared with other criteria (≤55%). The comparable values for LTA 5μ MADP &gt;46% were PRU &gt;235 (AUC 0.850, p&lt;0.001, sensitivity 85.3% and specificity 70.4%) and PRI &gt;59% (Figure B). Conclusion: The published cutoff values for HPR by LTA 5μ MADP and PRU were well correlated, whereas published PRI &gt;50% cutoff value may overestimate the risk of HPR. Updated cutoff of PRI &gt; 60% may better stratify the risk for HPR and can be used in future trials.

The effect of ticagrelor versus clopidogrel on high on-treatment platelet reactivity: Combined analysis of the ONSET/OFFSET and RESPOND studies

The objective of the study was to determine the prevalence of high on-treatment platelet reactivity (HPR) in coronary artery disease patients enrolled in the ONSET/OFFSET and RESPOND studies. HPR has been linked to the occurrence of adverse events after stenting in patients treated with clopidogrel (C) and aspirin. Prevalence of HPR after treatment with ticagrelor (T), a reversible oral P2Y(12) receptor antagonist developed to overcome the limitations of C, is unknown. Patients were treated with T (n = 106) or C (n = 103) on top of aspirin therapy. HPR was defined by published cutoff points associated with post-percutaneous coronary intervention ischemic risk: >59% 20 μM adenosine diphosphate-induced aggregation (light transmittance aggregometry), >235 P2Y12 reaction unit by VerifyNow P2Y(12) assay (VerifyNow, San Diego, CA), and >50% platelet reactivity index by vasodilator-stimulated phosphoprotein phosphorylation assay (VASP-P). Proportion differences for T versus C were analyzed by χ(2) test for each time point. Correlations (R) were analyzed by the Pearson method. Ticagrelor was associated with a significantly lower prevalence of HPR (0%-8%) compared with C (21%-81%) at 2, 4, 8, and 24 hours and ≥2 weeks postdosing (P < .0001, for all assays). The R values between light transmittance aggregometry and VerifyNow/VASP-P were all ≥0.43, P < .0001. The above data represent the largest serial pharmacodynamic evaluation of the comparative effects of T versus C. Ticagrelor was rapidly and consistently associated with a very low prevalence of HPR compared with C, as determined by multiple established methods to measure platelet reactivity. These results provide a mechanism for the lower ischemic event rate associated with T therapy reported in the PLATO trial.