U. S. Tantry

Paraoxonase 1 (PON1) Gene Variants Are Not Associated With Clopidogrel Response

A common functional variant in paraoxonase 1 (PON1), Q192R, was recently reported to be a major determinant of clopidogrel response. This variant was genotyped in 566 participants of the Amish Pharmacogenomics of Anti–Platelet Intervention (PAPI) study and in 227 percutaneous coronary intervention (PCI) patients. Serum paraoxonase activity was measured in a subset of 79 PAPI participants. PON1 Q192R was not associated with pre– or post–clopidogrel platelet aggregation in the PAPI study (P = 0.16 and P = 0.21, respectively) or the PCI cohort (P = 0.47 and P = 0.91, respectively). The Q192 allele was not associated with cardiovascular events (hazard ratio (HR) 0.46, 95% confidence interval (CI) 0.20–1.06; P = 0.07). No correlation was observed between paraoxonase activity and post–clopidogrel platelet aggregation (r2 < 0.01, P = 0.78). None of 49 additional PON1 variants evaluated was associated with post–clopidogrel platelet aggregation. These findings do not support a role for PON1 as a determinant of clopidogrel response.

Earlier recovery of platelet function after discontinuation of treatment with ticagrelor compared with clopidogrel in patients with high antiplatelet responses

Summary.  Background: The rate of recovery of platelet function after discontinuation of P2Y12 inhibitors depends on the reversibility of the antiplatelet effect and the extent of the on‐treatment response. P2Y12 inhibition increases the bleeding risk in patients requiring surgery. Objectives: To evaluate recovery of platelet function after discontinuation of ticagrelor vs. clopidogrel in stable coronary artery disease (CAD) patients with high levels of platelet inhibition (HPI) during the ONSET/OFFSET study. Methods: Patients received aspirin 75–100 mg per day and either ticagrelor 90 mg twice‐daily or clopidogrel 75 mg daily for 6 weeks. This subanalysis included patients with HPI after the last dose of maintenance therapy, defined as: inhibition of platelet aggregation (IPA) > 75% 4 h post‐dose (ADP 20 μm, final extent); < 120 P2Y12 reaction units 8 h post‐dose (VerifyNow P2Y12 assay); or platelet reactivity index < 50% 8 h post‐dose (VASP‐P assay). Results: IPA > 75% was observed in 39 out of 47 ticagrelor‐treated and 17 out of 44 clopidogrel‐treated patients. The rate of offset of IPA over 4–72 h was greater with ticagrelor (IPA %/hour slope: −1.11 vs. −0.67 for clopidogrel; P < 0.0001). Mean IPA was significantly lower with ticagrelor than clopidogrel between 48 and 168 h post‐dose (P < 0.01). Similar findings were observed with the other assays. The average time for IPA to decline from 30% to 10% was 50.8 h with ticagrelor vs. 110.4 h with clopidogrel. Conclusions: In patients with HPI, recovery of platelet function was more rapid after discontinuation of ticagrelor than clopidogrel leading to significantly greater platelet reactivity by 48 h after the last dose in the ticagrelor group.

High on-treatment platelet reactivity assessed by various platelet function tests: is the consensus-defined cut-off of VASP-P platelet reactivity index too low?

Recent consensus of the Working Group has suggested that high on-treatment platelet reactivity (HPR) to ADP is a major cardiovascular risk factor [1]. This document also has provided the potential cut-offs of HPR to ADP for the most commonly used platelet function tests (PFTs), including light transmittance aggregometry (LTA), the VerifyNow P2Y12 assay (VerifyNow), Multiplate and the vasodilator-stimulated phosphoprotein-phosphorylation (VASP-P) assay. Although the concept of HPR is a major step forward for a personalized antiplatelet therapy strategy in high-risk patients undergoing percutaneous coronary intervention (PCI), several issues have been raised and delayed the clinical adoption of PFT [2,3]. The different correlations and degree of agreement between HPR determined by various PFTs are important concerns. Although the various PFTs identify different aspects of platelet biology, several studies have suggested matched cut-offs of HPR measured by LTA, VerifyNow and Multiplate [4,5], strengthening the reliability of the hypothesis of HPR being an important indicator of risk. The higher prevalence of HPR determined by the VASP-P assay in clopidogrelor prasugrel-treated patients (> 50% and 25%, respectively) compared with other assays during clopidogrel therapy (20 40%) [6–10], questions that the consensus-defined cut-off value of > 50% platelet reactivity index (PRI) may be so low that the true proportion of high-risk patients for ischemic events is overestimated [2,3]. If we keep in mind the relatively low rate of post-PCI ischemic events, an estimation of HPR exceeding 50% during clopidogrel therapy may cause unnecessary application of potent P2Y12 receptor inhibitors with an attendant increased risk of bleeding. We therefore performed the current pharmacodynamic analysis to determine the agreement for the definition and the prevalence of HPR among various PFTs in patients with stable coronary artery disease treated with dual antiplatelet therapy [6]. Platelet function measurements from two prospective randomized studies [6] were used in this analysis; 37 and 39 patients were enrolled from our institution and treated with ticagrelor (180-mg loading-dose [LD] and 90-mg twice a day maintenance-dose [MD]) and clopidogrel (600-mg LD and 75mg d MD), respectively. Serial LTA, VerifyNow and VASPP assays were performed, and a total of 1002 matched pairs (ticagrelor = 498 pairs; clopidogrel = 504 pairs) were available for this analysis. The overall inter-assay correlation and receiver-operating characteristics (ROC) curve analysis determined by the level of platelet inhibition were consistent irrespective of clopidogrel or ticagrelor administration. The LTA values correlated most with VerifyNow (Fig. 1A, r = 0.821) and less well with the VASP-P assay (Fig. 1B, r = 0.688). PRI values in low/ medium responsive patients were more scattered compared with LTAmeasurements, a finding that is in line with previous observations [11,12]. The frequency ofHPR (based on consensus-defined cut-offs) was the greatest by VASP-P PRI (47.5%) compared with 5 lM ADP-induced aggregation > 46% (37.3%) and P2Y12 reaction units (PRU) > 235 (40.0%). A PRU cut-off > 235 showed substantial agreement with > 46% LTA cut-off (j = 0.737; concordance, 87.5%; balanced distribution of discordance) (Fig. 1A). The VASP-P PRI cut-off showed moderate agreement with the LTA cut-off (j = 0.585; concordance, 79.6%; relatively unbalanced distribution of discordance) (Fig. 1B). ROC curve analysis was used to assess the corresponding points to 5 lM ADP-induced aggregation > 46%, PRU > 234 and VASP-P PRI > 60% (Fig. 1C, D). When the new HPR criteria of a VASP PRI > 60% were applied, the agreement with the LTA cut-off improved (j = 0.634; concordance, 82.6%; narrowed discordance) (Fig. 1B: green arrow and numbers). We also performed ROC curve analysis to assess the corresponding cut-offs to VASP-P PRI > 50%. The matched point with 5 lM ADPinduced aggregation was > 37% (AUC [area under curve], 0.887; 95% confidence interval [CI], 0.843–0.890; P < 0.001; sensitivity, 79.5%; specificity, 82.7%). PRU > 167 was identified as the matched point to > 50% VASP-P PRI (AUC, 0.897; 95% CI, 0.875–0.918; P < 0.001; sensitivity, 87.1%; and specificity, 80.3%). To the best of our knowledge, this is the first comparative analysis describing the agreement between the definitions of the Correspondence: Paul A. Gurbel, Sinai Center for Thrombosis Research, Cardiac Catheterization Laboratory, 2401 W. Belvedere Ave., Baltimore, MD 21215, USA. Tel.: +1 410 601 9600; fax: +1 410 601 9601. E-mail: pgurbel@lifebridgehealth.org

Viral respiratory tract infections increase platelet reactivity and activation: an explanation for the higher rates of myocardial infarction and stroke during viral illness

Factor VIII and Factor IX in a twin population. Evidence for a major effect of ABO locus and factor VIII level. Am J Hum Genet 1985; 37: 89. 16 O’Donnell J, Boulton F, Manning R, Laffan M. Genotype at the secretor blood locus is a determinant of plasma von-Willebrand factor level. Br J Haematol 2002; 116: 350–6. 17 Meiklejohn DJ, Vickers MA, Morrison ER, Dijkuisen R, Moore I, Urbaniak SJ, Greaves M. In vivo platelet activation in atherothrombotic stroke is not determined by polymorphisms of human platelet glycoprotein IIIa or Ib. Br J Haematol 2001; 112: 621–31. 18 Downing J, Darke C. A modified PCR-SSP method for the identification of ABO blood group antigens. Eur J Immunogenet 2003; 30: 295–8. 19 Vestergaard EM, Wolf H, Orntoft TF. Increased concentration of genotype-interpreted Ca 19-9 in urine of bladder cancer patients mark diffuse atypia of the urothelium. Clin Chem 1998; 44: 197–204. 20 O’Donnell J, Boulton F,Manning R, LaffanM.Amount of H antigen expressed on circulating von Willebrand factor is modified by ABO blood group genotype and is a major determinant of plasma von Willebrand factor antigen levels. Arterioscler Thromb Vasc Biol 2002; 22: 335–341.

Pharmacodynamic Evaluation of Clopidogrel Plus PA32540: The Spaced PA32540 With Clopidogrel Interaction Gauging (SPACING) Study

PA32540 combines 325 mg enteric–coated (EC) aspirin (ASA) with 40 mg immediate–release omeprazole; its influence on the antiplatelet effect of clopidogrel (C) is unknown. In this randomized, open–label study, subjects (n = 30) were treated with (i) 300 mg C + 325 mg ECASA followed by 75 mg C + 325 mg ECASA on days 2–7, (ii) 300 mg C + PA32540 followed by 75 mg C + PA32540 on days 2–7, or (iii) PA32540 in the morning + 300 mg C 10 h later on day 1 and PA32540 in the morning + 75 mg C 10 h later on days 2–7. We analyzed the noninferiority of PA32540 relative to ECASA, as defined by the upper bound of the 95% confidence interval ≤10% for the difference in least–square means of platelet inhibition between the treatments. As compared to ECASA+C, synchronous treatment of PA32540+C was not noninferior, whereas the spacing strategy of PA32540+C was noninferior. Spacing the administration of PA32540 and clopidogrel lessens the interaction observed with synchronous administration; PA32540 administration with clopidogrel may be associated with a different antiplatelet profile.

Influence of CYP2C19*2 and *3 loss-of-function alleles on the pharmacodynamic effects of standard- and high-dose clopidogrel in East Asians undergoing percutaneous coronary intervention: the results of the ACCEL-DOUBLE-2N3 study.

Y . -H . J EONG,*† 1 K . A . ABADILLA ,†‡ 1 U . S . TANTRY ,† Y . PARK ,* J . S . KOH,* C . H . KWAK,* J . -Y . HWANG* and P . A . GURBEL† *Department of Internal Medicine, Gyeongsang National University Hospital and Gyeongsang National University School of Medicine, Jinju, Korea; †Sinai Center for Thrombosis Research; and ‡Department of Internal Medicine, Sinai Hospital of Baltimore, Baltimore, MD, USA

Translational platelet research in patients with coronary artery disease: What are the major knowledge gaps?

Translational platelet function investigations performed in the percutaneous coronary intervention (PCI)-treated population receiving clopidogrel have identified high platelet reactivity to ADP (HPR) as a major risk factor for both acute as well as long-term ischaemic event occurrence, including stent thrombosis. Recent studies have highlighted the relation of single nucleotide polymorphisms of genes involved in clopidogrel absorption and metabolism to reduced pharmacokinetic and pharmacodynamic responses to clopidogrel. CYP 2C19 loss-of-function (LoF) allele carriage has been associated with increased thrombotic risk in the PCI population. However, there is no information regarding the utility of platelet function testing to predict outcomes in patients with stable coronary artery disease and in medically managed patients with acute coronary syndromes. Additionally, few studies have included longitudinal assessment of platelet function to assess a potential time-dependent relation to ischaemic event occurrence and no phase-III antiplatelet-therapy trial has included a large enough platelet function sub-study to examine the relation between on-treatment platelet reactivity, bleeding, and ischaemic event occurrence. Therefore, futher studies are needed to delineate the role of platelet function testing across the spectrum of symptomatic coronary artery disease.

Effect of adjunctive dipyridamole to DAPT on platelet function profiles in stented patients with high platelet reactivity. The result of the ACCEL-DIP Study.

Adjunctive use of phosphodiesterase (PDE) inhibitor can enhance antiplatelet and vasoprotective properties in patients with cardiovascular disease. The aim of this study was to evaluate the impact of PDE5 inhibitor dipyridamole on platelet function in stented patients with high platelet reactivity (HPR) during dual antiplatelet therapy (DAPT) with aspirin and clopidogrel. Patients with HPR after 600-mg clopidogrel loading were randomly assigned to adjunctive dipyridamole 75 mg twice daily to standard DAPT (DIP group; n = 45) or double-dose clopidogrel of 150 mg daily (DOUBLE group; n = 46) for 30 days. Platelet function was assessed at baseline and 30-day follow-up with platelet reactivity index (PRI) by vasodilator-stimulated phosphoprotein-phosphorylation (VASP-P) assay and platelet aggregation (PA) by light transmittance aggregometry (LTA). Primary endpoint was PRI at 30-day follow-up. HPR was defined as PRI > 50%. Baseline platelet function did not differ between the groups. Following 30-day therapy, platelet function was significantly reduced in the DIP and DOUBLE groups (all p-values ≤ 0.004 and ≤ 0.068, respectively). PRI values were not significantly different between the two groups (mean difference: 3.1%; 95% confidence interval: -2.8% to 9.0%: p = 0.295). PA values and prevalence of HPR were similar between the groups. However, a significant number of patients still exhibited HPR in the DIP (75.6%) and DOUBLE (67.4%) groups. In conclusion, among stented HPR patients, adding dipyridamole to DAPT does not reduce platelet reactivity and prevalence of HPR compared with double-dose clopidogrel therapy, and therefore both strategies are inadequate to overcome HPR.

Potential role of oral anticoagulants in the treatment of patients with coronary artery disease: focus on dabigatran

The pharmacologic management of patients with high-risk coronary artery disease consists of aspirin and a P2Y12 receptor inhibitor. Chronic oral anticoagulation with warfarin is the major treatment strategy to attenuate thromboembolism or stroke in patients with deep vein thrombosis, pulmonary embolism, heart failure and atrial fibrillation. A substantial percentage of the latter group of patients have coronary artery disease and may require stenting with long-term dual antiplatelet therapy in addition to therapy with warfarin to reduce arterial ischemic events in addition to stroke. These new oral anticoagulants have been developed for long-term therapy to overcome the limitations of warfarin. Dabigatran is a direct thrombin inhibitor and its role in patients with acute coronary syndrome is being explored.

Evidence that pre-existent variability in platelet response to ADP accounts for ‘clopidogrel resistance’: reply to a rebuttal

durations, our study design avoided the confounding effects on platelet response of a percutaneous coronary intervention performed between pre- and postclopidogrel time-points. Our statistical analyses compared the variation observed in the untreated population (wherein everyone should respond to ADP) with the variation observed in the subsets of patients exposed to clopidogrel for varying lengths of time (wherein, if clopidogrel resistance were present, some individuals would respond normally to ADP while most would respond poorly to ADP, resulting in greater variation of response for the population). The data from this large number of patients (n = 613) (see Fig. 2) were consistent with the data from the normal volunteers (see Fig. 1), i.e. platelet response variability