P2Y12 Platelet Reactivity Research Articles

A Multicenter Evaluation of Clopidogrel Resistance and Its Role in Predicting Stent Thrombosis in Transcarotid Artery Revascularization

OBJECTIVEClopidogrel resistance testing is not routine prior to Transcarotid Artery Revascularization (TCAR) and resistance rates are not well described in this setting, despite frequent use of periprocedural clopidogrel. We compared two resistance testing modalities to determine the relationship between resistance and stent outcomes. METHODSConsecutive patients undergoing TCAR at three institutions were retrospectively identified. Clopidogrel-resistance testing results and outcomes were described. RESULTSA total of 210 patients underwent TCAR from 2018-2022. 154 (73%) were on dual antiplatelet therapy (DAPT) for at least 7 days prior to TCAR. Twenty-nine patients were not on DAPT due to therapeutic anticoagulation and most (38/56, 68%) received a loading dose of a second antiplatelet the day of surgery. Twenty-five patients (11.9%) experienced stent thrombosis within 30 days. Patients not on DAPT for at least 7 days prior to surgery were more prone to stent thrombosis (16.7% vs 10.4%, p=.164). Over half (133/210, 63%) of patients underwent resistance testing, 25 with thromboelastogram with platelet mapping (TEG-PM), 103 with VerifyNow P2Y12 platelet reactivity assay, and 5 with both. Prevalence of Clopidogrel resistance among tested patients was 41%. In patients tested using both TEG-PM and VerifyNow, agreement was poor (Cohen’s Kappa -0.05). Among patients with resistance, 12 (22%) experienced stent thrombosis. Comparatively, 8 (10%) patients without resistance developed thrombosis (p=.021). VerifyNow P2Y12 platelet reactivity assay correctly predicted Clopidogrel-resistance more accurately than TEG-PM (70% versus 40%, p=.025) and had sensitivity of 56% and specificity of 73% for stent thrombosis. CONCLUSIONOur multi-institutional cohort confirms a high rate of Clopidogrel resistance in patients undergoing TCAR, with higher acute stent thrombosis rates noted in patients with resistance. VerifyNow P2Y12 platelet reactivity assays more reliably predict Clopidogrel resistance than TEG-PM.

Impact of transfusion strategy on platelet aggregation and biomarkers in myocardial infarction patients with anemia.

Higher rates of thrombotic events have been reported in myocardial infarction (MI) patients requiring blood transfusion. The impact of blood transfusion strategy on thrombosis and inflammation is still unknown. To compare the impact of a liberal vs. a restrictive transfusion strategy on P2Y12 platelet reactivity and biomarkers in the multicentric randomized REALITY trial. Patients randomized to a liberal (hemoglobin≤10g/dL) or a restrictive (hemoglobin≤8g/dL) transfusion strategy had VASP-PRI platelet reactivity measured centrally in a blinded fashion and platelet reactivity unit (PRU) measured locally using encrypted VerifyNow; at baseline and after randomization. Biomarkers of thrombosis (P-selectin, PAI-1, vWF) and inflammation (TNF-α) were also measured. The primary endpoint was the change in the VASP-PRI (difference from baseline and post randomization) between the randomized groups. A total of 100 patients randomized were included in this study (n=50 in each group). Transfused patients received on average 2.4±1.6 units of blood. We found no differences in change of the VASP PRI (difference 1.2% 95% CI (-10.3-12.7%)) or by the PRU (difference 13.0 95% CI (-21.8-47.8)) before and after randomization in both randomized groups. Similar results were found in transfused patients (n=71) regardless of the randomized group, VASP PRI (difference 1.7%; 95% CI (-9.5-1.7%)) or PRU (difference 27.0; 95% CI (-45.0-0.0)). We did not find an impact of transfusion strategy or transfusion itself in the levels of P-selectin, PAI-1, vWF, and TNF-α. In this study, we found no impact of a liberal vs. a restrictive transfusion strategy on platelet reactivity and biomarkers in MI patients with anemia. A conclusion that should be tempered due to missing patients with exploitable biological data that has affected our power to show a difference.

Effect of P2Y12 platelet reactivity level on peri- and postoperative outcomes of cardiac surgery patients.

Evidence surrounding P2Y12 platelet reactivity units (PRU) impact on bleeding outcomes in patients undergoing coronary artery bypass is varied. This study sought to assess whether on-pump CABG procedures result in increased bleeding in patients with high compared to low PRUs. This retrospective cohort study compared those with a PRU level ≤237 (low PRU group) to >237 (high PRU group). The primary outcome assessed massive or severe bleeding in accordance with universal definition of perioperative bleeding criteria. Secondary outcomes assessed mortality, length of stay and relevant bleeding related outcomes (e.g., rates of moderate or lower classifications of bleeding, chest tube output, blood product receipt). A total of 69 patients were included, 47 in the low and 22 in the high PRU groups. Patients were a median (IQR) 66 (62-74) years and 84.1% (N.=58) were male. Most patients received clopidogrel prior to procedure (39 [83%] in low and 18 [81.8%] in high PRU group; P=1.0000). The rate of the primary outcome was 14.9% (N.=7) in patients with a low PRU and 18.2% (N.=4) in patients with a high PRU; P=0.7345. The rate of moderate bleeding was 59.6% (N.=28) in the low and 27.3% (N.=6) in the high PRU group (P=0.0124). Packed red blood cells (PRBCs) were administered to more patients in the low (23 [48.9%]) than the high PRU group (2 [22.7%]; P=0.0388). There were no differences in other blood product requirement, chest tube output, factor products administered, mortality, or length of stay. This study determined that low preoperative P2Y12 PRU levels may influence moderate bleeding in patients undergoing cardiac surgery, but not massive or severe bleeding.

Effect of CYP3A4*22 and PPAR-α Genetic Variants on Platelet Reactivity in Patients Treated with Clopidogrel and Lipid-Lowering Drugs Undergoing Elective Percutaneous Coronary Intervention.

This study aims to determine whether genetic variants that influence CYP3A4 expression are associated with platelet reactivity in clopidogrel-treated patients undergoing elective percutaneous coronary intervention (PCI), and to evaluate the influence of statin/fibrate co-medication on these associations. A study cohort was used containing 1124 consecutive elective PCI patients in whom CYP3A4*22 and PPAR-α (G209A and A208G) SNPs were genotyped and the VerifyNow P2Y12 platelet reactivity test was performed. Minor allele frequencies were 0.4% for CYP3A4*22/*22, 6.8% for PPAR-α G209A AA, and 7.0% for PPAR-α A208G GG. CYP3A4*22 was not associated with platelet reactivity. The PPAR-α genetic variants were significantly associated with platelet reactivity (G209A AA: −24.6 PRU [−44.7, −4.6], p = 0.016; A208G GG: −24.6 PRU [−44.3, −4.8], p = 0.015). Validation of these PPAR-α results in two external cohorts, containing 716 and 882 patients, respectively, showed the same direction of effect, although not statistically significant. Subsequently, meta-analysis of all three cohorts showed statistical significance of both variants in statin/fibrate users (p = 0.04 for PPAR-a G209A and p = 0.03 for A208G), with no difference in statin/fibrate non-users. In conclusion, PPAR-α G209A and A208G were associated with lower platelet reactivity in patients undergoing elective PCI who were treated with clopidogrel and statin/fibrate co-medication. Further research is necessary to confirm these findings.

Antiplatelet effects of citalopram in patients with ischaemic stroke: A randomized, placebo-controlled, double-blind study

We evaluated the effect of SSRI treatment on platelet aggregation in patients with ischaemic stroke and included patients from the randomized double-blind controlled study of citalopram in acute ischaemic stroke (TALOS). Patients on clopidogrel were included 6 months after acute ischaemic stroke. Platelet parameters, including P2Y12 platelet reactivity using the VerifyNow System, were measured at the last day of study treatment and repeated after a 14-day wash-out period. A total of 60 patients were included (n = 32 randomized to citalopram). Platelet aggregation levels did not differ between the citalopram group (mean 116, 95% CI 89 to 143) and the placebo group (mean 136, 95% CI 109 to 163) (On-treatment, p = 0.14). Similarly, there was no significant change in platelet aggregation in the citalopram group from on-treatment to post-treatment (mean difference 2.0; 95% CI −18 to 14). Platelet count, size and turnover were not affected by SSRI treatment. In conclusion, SSRI therapy did not lead to statistically significant inhibition of platelet aggregation in ischaemic stroke patients treated with clopidogrel.

Effects of Ticagrelor, Prasugrel, or Clopidogrel on Endothelial Function and Other Vascular Biomarkers: A Randomized Crossover Study

ObjectivesThe study sought to assess whether treatment with ticagrelor, as compared with prasugrel and clopidogrel, improves endothelium-dependent dilation throughout the course of the treatment and other vascular biomarkers, including systemic adenosine plasma levels. BackgroundThe in vivo off-target effects of ticagrelor in post–acute coronary syndrome (ACS) patients remain poorly characterized. MethodsFifty-four stable post-ACS patients were sequentially exposed to each of the 3 oral P2Y12 inhibitors following a 3-period balanced Latin square crossover design with 4 weeks per treatment in 5 European centers. The primary endpoint was the assessment of endothelial function with pulse amplitude tonometry and expressed as reactive hyperemia index at treatment steady state. Secondary endpoints included reactive hyperemia index after loading or before maintenance regimen, systemic adenosine plasma levels, a wide set of vascular biomarkers, and ticagrelor or AR-C124910XX plasma levels throughout each ticagrelor period. In 9 patients, the evaluation of endothelial function was performed simultaneously by pulse amplitude tonometry and flow-mediated dilation. ResultsReactive hyperemia index did not differ after ticagrelor (1.970 ± 0.535) as compared with prasugrel (2.007 ± 0.640; p = 0.557) or clopidogrel (2.072 ± 0.646; p = 0.685), nor did systemic adenosine plasma levels or vascular biomarkers at any time points. P2Y12 platelet reactivity units were lower after ticagrelor as compared with clopidogrel at all time points and after maintenance dose as compared with prasugrel. Flow-mediated dilation did not differ after the maintenance dose of ticagrelor as compared with clopidogrel and prasugrel. ConclusionsTicagrelor did not improve endothelial function or increased systemic adenosine plasma levels as compared with prasugrel and clopidogrel in stabilized patients who suffered from an ACS. (Hunting for the Off-Target Properties of Ticagrelor on Endothelial Function in Humans [HI-TECH]; NCT02587260).

Effects of statin therapy on platelet reactivity after percutaneous coronary revascularization in patients with acute coronary syndrome.

Statin use is associated with enhanced pharmacodynamic response to clopidogrel in patients with stable coronary artery disease undergoing percutaneous coronary intervention (PCI). However, the impact of statin therapy on clopidogrel response profiles in patients with acute coronary syndrome (ACS) undergoing PCI has not been established and represents the objective of this investigation. On-treatment P2Y12 platelet reactivity was measured using the vasodilator stimulated phosphoprotein (VASP) phosphorylation assay before PCI, at hospital discharge, and at 1month after PCI in ACS patients enrolled in the multicenter, prospective GEne polymorphisms, Platelet Reactivity, and Syntax Score (GEPRESS) study (n = 962). High platelet reactivity (HPR) was defined as platelet reactivity index ≥50%. Statins were prescribed at hospital discharge in 87% (n = 835) of patients. All patients were followed for 1year. The 1-month HPR rate was lower in statin than in non-statin treated patients (39.6 vs 52%, respectively, p = 0.009). This finding was confirmed also among statin-treated patients with high Syntax score (≥15). After adjustment for differences in baseline characteristics, statin use at discharge was independently associated with 1-month HPR rate (odds ratio, 0.58, 95% confidence interval, 0.38-0.89; p = 0.015). In ACS patients undergoing PCI treated with clopidogrel the use of statins at discharge was associated with significantly lower 1-month HPR rates compared with patients not treated with statins.

Impact of platelet inhibition level on subsequent no-reflow in patients undergoing primary percutaneous coronary intervention for ST-segment elevation myocardial infarction

High P2Y12 platelet reactivity (PR) level after primary percutaneous coronary intervention (PPCI) for ST-segment elevation myocardial infarction (STEMI) affects prognosis and may induce the no-reflow phenomenon. To investigate the role of PR in the genesis of microvascular obstruction. Patients with STEMI undergoing PPCI within 12hours of symptoms onset were included prospectively. All patients received a 600mg clopidogrel-loading dose before PPCI and 250mg aspirin. PR was measured thereafter during PPCI while wiring the culprit lesion and before coronary dilatation, using the P2Y12 VerifyNow® assay. No-reflow was defined as ST-segment regression<50% observed 90minutes after PPCI. Between January 2014 and November 2015, 140 STEMI patients were included, and divided into two groups: a low PR group (LPR) defined as PR<209P2Y12 reaction units (PRU); and a high PR group (HPR) defined as PR≥209PRU. There were no differences in baseline characteristics between LPR and HPR groups, including age (57.8±11.9 vs. 59.4±13.2 years, respectively; P=0.44) and weight (76.1±15.1 vs. 74.8±10.9kg, respectively; P=0.55). Delay to revascularization was 270.1±175.5 vs. 295.6±206.2minutes (P=0.49) and time between clopidogrel-loading and PR measurement was 53±37 vs 65±54minutes (P=0.29) in the LPR and HPR groups, respectively. No-reflow was more frequent in the HPR group (44 [47.3%] vs. 9 [19.1%]; P=0.0012). Mean PR was higher in patients with no-reflow: 268.3±53 vs. 223.8±50.1 PRU (P=0.002). In multivariable analysis, HPR was an independent predictor of no-reflow. Area under the receiver operating characteristic curve was 0.745 (0.654, 0.835); the cut-off value predicting no-reflow was 254PRU. High PR level measured at PPCI is independently associated with no-reflow.

Mo1156 Predictors for Elevation in Serum Gastrin Following Proton Pump Inhibitor Treatment

Background: It has been suggested that proton pump inhibitors (especially omeprazole and esomeprazole) may reduce the effectiveness of clopidogrel's anti-platelet activity possibly reflecting inhibition of Cytochrome P450 (CYP) 2C19, a hepatic iso-enzyme responsible for conversion of the agent from pro-drug to its active moiety. Whether differences exist between PPIs types on reduction in platelet inhibition during simultaneous PPI and clopidogrel therapy however remains uncertain. The aim of this study was to compare the effects of different PPIs on clopidogrel-mediated platelet inhibition using platelet aggregometry. Methods: 53 patients (29 men, mean age 79±10yrs) concurrently treated with clopidogrel and PPIs were identified. 57%were receiving pantoprazole, 19% omeprazole, 15% esomeprazole, 6% rabeprazole, and 3% lansoprazole. Platelet reactivity was determined on 5ml fresh blood using the Accumetrics VerifyNow® assay system. Results were expressed as P2Y12 platelet reactivity units (PRU) with a value of >235 units indicating suboptimal inhibition of clopidogrel-mediated anti-platelet activity.[i] PRU values were compared for different PPIs using Student's t-test. The prevalence of sub-optimal platelet inhibition was compared with Fisher's exact test. Results: The PRU was >235 in 13 of 53 patients (25%). Of these, 4 were receiving pantoprazole (13% of total patients taking pantoprazole), 4 esomeprazole (4/8, 50%), and the remaining 5 patients omeprazole (5/10, 50%). PRU values in the 5 patients receiving lansoprazole or rabeprazole were 235 compared to patients treated with pantoprazole, lansoprazole or rabeprazole (p<0.05). The mean PRU in subjects <80 years was 152.2±16.15 versus 200.0±11.93 in subjects who were aged over 80 (p= 0.0183). Conclusion: Patients receiving a combination of clopidogrel with either esomeprazole or omeprazole have a higher incidence of suboptimal inhibition of clopidogrelmediated platelet activity when compared to other PPIs. Monitoring of platelet function should be considered in patients at high risk of cardiovascular events who receive concurrent clopidogrel and PPI therapy. [i] M.J. Price et al. Prognostic significance of post-clopidogrel platelet reactivity assessed by a point-of-care assay on thrombotic events after drug-eluting stent implantation., European Heat Journal (2008) 29, 992-1000.

Mo1155 Differential Effects Between Proton Pump Inhibitors on Clopidogrel-Mediated Anti-Platelet Inhibition

Background: It has been suggested that proton pump inhibitors (especially omeprazole and esomeprazole) may reduce the effectiveness of clopidogrel's anti-platelet activity possibly reflecting inhibition of Cytochrome P450 (CYP) 2C19, a hepatic iso-enzyme responsible for conversion of the agent from pro-drug to its active moiety. Whether differences exist between PPIs types on reduction in platelet inhibition during simultaneous PPI and clopidogrel therapy however remains uncertain. The aim of this study was to compare the effects of different PPIs on clopidogrel-mediated platelet inhibition using platelet aggregometry. Methods: 53 patients (29 men, mean age 79±10yrs) concurrently treated with clopidogrel and PPIs were identified. 57%were receiving pantoprazole, 19% omeprazole, 15% esomeprazole, 6% rabeprazole, and 3% lansoprazole. Platelet reactivity was determined on 5ml fresh blood using the Accumetrics VerifyNow® assay system. Results were expressed as P2Y12 platelet reactivity units (PRU) with a value of >235 units indicating suboptimal inhibition of clopidogrel-mediated anti-platelet activity.[i] PRU values were compared for different PPIs using Student's t-test. The prevalence of sub-optimal platelet inhibition was compared with Fisher's exact test. Results: The PRU was >235 in 13 of 53 patients (25%). Of these, 4 were receiving pantoprazole (13% of total patients taking pantoprazole), 4 esomeprazole (4/8, 50%), and the remaining 5 patients omeprazole (5/10, 50%). PRU values in the 5 patients receiving lansoprazole or rabeprazole were 235 compared to patients treated with pantoprazole, lansoprazole or rabeprazole (p<0.05). The mean PRU in subjects <80 years was 152.2±16.15 versus 200.0±11.93 in subjects who were aged over 80 (p= 0.0183). Conclusion: Patients receiving a combination of clopidogrel with either esomeprazole or omeprazole have a higher incidence of suboptimal inhibition of clopidogrelmediated platelet activity when compared to other PPIs. Monitoring of platelet function should be considered in patients at high risk of cardiovascular events who receive concurrent clopidogrel and PPI therapy. [i] M.J. Price et al. Prognostic significance of post-clopidogrel platelet reactivity assessed by a point-of-care assay on thrombotic events after drug-eluting stent implantation., European Heat Journal (2008) 29, 992-1000.

EVALUATION OF COST-EFFECTIVENESS OF PLATELET REACTIVITY ANALYSIS USING THE VERIFYNOW P2Y12 ASSAY IN PATIENTS AFTER ACUTE CORONARY SYNDROME

Dual antiplatelet therapy, including clopidogrel and aspirin, in a significant share of patients after acute coronary syndrome (ACS) is characterized by high level of platelet reactivity, which is associated with an increased incidence of cardiovascular events. Perhaps it will make reasonable the prescription of new antiplatelet drugs, particularly the combination of ticagrelor with aspirin. Aim. To assess the cost-effectiveness of VerifyNow P2Y12 platelet reactivity testing in patients after ACS. Material and methods. The analysis was performed for patients aged 55 years after ACS by modeling based on the results of the PLATO trial considering Russian epidemiological data. The time horizon of simulation was 5 years. It was assumed that the patients were receiving either generic clopidogrel or ticagrelor for 1 year, or before maintenance treatment VerifyNow P2Y12 assay had been performed, and the patients with platelet reactivity index &gt;230 24-48 hours after ACS were receiving ticagrelor and the remaining patients - generic clopidogrel. It was expected that after 1 year the patients would discontinue treatment with clopidogrel or ticagrelor, and hereafter additional therapeutic effect of their use would be absent. The costs of antiplatelet agents in the reference case corresponded to the weighted average price of public procurement in 2013 in Russia. The costs of treatment of complications corresponded to the compulsory health insurance rates for St. Petersburg in 2014. The cost and life expectancy were discounted at 3.5% per year. Results. The platelet reactivity test and the prescription by its results of the combination of clopidogrel plus aspirin or ticagrelor plus aspirin can prevent 5 myocardial infarction and 6 deaths per 1000 patients additionally as compared with the prescription of clopidogrel plus aspirin combination to all patients. The costs for one additional year of life as compared with the combination of clopidogrel plus aspirin were 376.5 and 373.2 thousand rubles, respectively, the costs for one additional quality adjusted life year (QALY) were 433.8 and 509.8 thousand rubles, respectively. The total predictive value of costs per 1 patient with ACS using the test was 32% lower than in the routine use of ticagrelor in all patients. Conclusion. Assessment of platelets reactivity using VerifyNow P2Y12 assay in patients with ACS and modification of antithrombotic therapy in accordance with the received data can be considered as a cost-effective intervention which can reduce treatment costs as compared with the routine use of new antithrombotic drugs.

Cost-Effectiveness of Universal and Platelet Reactivity Assay-Driven Antiplatelet Therapy in Acute Coronary Syndrome

Assays monitoring P2Y12 platelet reactivity can accurately predict which patients will have a poor response to clopidogrel. We sought to determine the cost-effectiveness of using platelet reactivity assays (PRAs) to select a dual-antiplatelet regimen for patients with acute coronary syndrome. A hybrid decision tree Markov model was developed to determine the cost-effectiveness of universal clopidogrel, ticagrelor, or prasugrel (given to all patients) or PRA-driven ticagrelor or prasugrel (given to patients with high platelet reactivity, defined as >230 on the VerifyNow P2Y12 assay; the others received generic clopidogrel). We assumed a cohort of 65-year-old patients with acute coronary syndrome and an incidence of high platelet reactivity of 32% and 13% at ~24 to 48 hours after revascularization and 1 month, respectively. The 5-year costs, quality-adjusted life-years, and incremental cost-effectiveness ratios were calculated for PRA-driven ticagrelor and prasugrel compared with universal clopidogrel, ticagrelor, or prasugrel. PRA-driven ticagrelor and prasugrel were cost-effective compared with universal clopidogrel (incremental cost-effectiveness ratio $40,100 and $49,143/quality-adjusted life-year, respectively); however, universal ticagrelor and prasugrel were not (incremental cost-effectiveness ratio $61,651 and $96,261/quality-adjusted life-year, respectively). Monte Carlo simulation suggested PRA-driven ticagrelor, PRA-driven prasugrel, universal ticagrelor, and universal prasugrel would have an incremental cost-effectiveness ratio <$50,000/quality-adjusted life-year in 52%, 40%, 23%, and 2% of the iterations compared with universal clopidogrel, respectively. Universal ticagrelor and prasugrel were not cost-effective compared with their respective PRA-driven regimens (incremental cost-effectiveness ratio $68,182; $116,875/quality-adjusted life-year, respectively). Monte Carlo simulation suggested universal ticagrelor and prasugrel would have an incremental cost-effectiveness ratio <$50,000/quality-adjusted life-year in 26% and 4% of iterations compared with their respective PRA-driven regimens. The results were most sensitive to differences in agent costs and drug-specific relative risks of death. In conclusion, even with generic clopidogrel, PRA-driven selection of antiplatelet therapy appeared to be a cost-effective strategy with the potential to decrease the overall acute coronary syndrome-associated healthcare costs.

Clopidogrel Pharmacokinetics and Pharmacodynamics Vary Widely Despite Exclusion or Control of Polymorphisms (CYP2C19, ABCB1, PON1), Noncompliance, Diet, Smoking, Co-Medications (Including Proton Pump Inhibitors), and Pre-Existent Variability in Platelet Function

This study sought to determine whether known genetic, drug, dietary, compliance, and lifestyle factors affecting clopidogrel absorption and metabolism fully account for the variability in clopidogrel pharmacokinetics and pharmacodynamics. Platelet inhibition by clopidogrel is highly variable. Patients with reduced inhibition have increased risk for major adverse cardiovascular events. Identification of factors contributing to clopidogrel's variable response is needed to improve platelet inhibition and reduce risk for cardiovascular events. Healthy subjects (n = 160; ages 20 to 53 years; homozygous CYP2C19 extensive metabolizer genotype; no nicotine for 6 weeks, prescription drugs for 4 weeks, over-the-counter drugs for 2 weeks, and no caffeine or alcohol for 72 h; confined; restricted diet) received clopidogrel 75 mg/day for 9 days, at which time clopidogrel pharmacokinetic and pharmacodynamic endpoints were measured. At steady-state, clopidogrel active metabolite (clopidogrel(AM)) pharmacokinetics varied widely between subjects (coefficients of variation [CVs] 33.8% and 40.2% for clopidogrel(AM) area under the time-concentration curve and peak plasma concentration, respectively). On-treatment vasodilator stimulated phosphoprotein P2Y(12) platelet reactivity index (PRI), maximal platelet aggregation (MPA) to adenosine phosphate, and VerifyNow P2Y12 platelet response units (PRU) also varied widely (CVs 32% to 53%). All identified factors together accounted for only 18% of intersubject variation in pharmacokinetic parameters and 32% to 64% of intersubject variation in PRI, MPA, and PRU. High on-treatment platelet reactivity was present in 45% of subjects. Clopidogrel pharmacokinetics and pharmacodynamics vary widely despite rigorous exclusion or control of known disease, polymorphisms (CYP2C19, CYP3A5, ABCB1, PON1), noncompliance, co-medications, diet, smoking, alcohol, demographics, and pre-treatment platelet hyperreactivity. Thus, as yet unidentified factors contribute to high on-treatment platelet reactivity with its known increased risk of major adverse cardiovascular events. (A Study of the Effects of Multiple Doses of Dexiansoprazole, Lansoprazole, Omeprazole or Esomeprazole on the Pharmacokinetics and Pharmacodynamics of Clopidogrel in Healthy Participants: NCT00942175).

Clopidogrel Pharmacokinetics and Pharmacodynamics Vary Widely Despite Exclusion or Control of Polymorphisms (CYP2C19, ABCB1, PON1), Non-Compliance, Diet, Smoking, Co-Medications (including Proton Pump Inhibitors), and Pre-Existent Variability in Platelet Function

AbstractAbstract 4356 Background:Platelet inhibition by clopidogrel is highly variable. Patients with reduced inhibition have increased risk for major adverse cardiovascular events. The aim of this study was to determine whether known genetic, drug, dietary, compliance and lifestyle factors affecting clopidogrel absorption and metabolism fully account for the variability in clopidogrel pharmacokinetics and pharmacodynamics. Methods and Results:Healthy subjects (n=160; age 20–53; homozygous CYP2C19 extensive metabolizer genotype; no nicotine 6 weeks, prescription drugs 4 weeks, over-the-counter drugs 2 weeks, caffeine and alcohol 72 hours; confined; restricted diet) received clopidogrel 75 mg daily for 9 days. At steady-state, clopidogrel active metabolite (clopidogrelAM) pharmacokinetics varied widely between subjects (CVs 33.8% and 40.2% for clopidogrelAM AUCt and Cmax, respectively). On-treatment pharmacodynamic endpoints VASP P2Y12 platelet reactivity index (PRI), maximal platelet aggregation (MPA) to ADP, and VerifyNow P2Y12 platelet response units (PRU) also varied widely (CVs 32 – 53%). All identified factors together accounted for only 18% of inter-subject variation in pharmacokinetic parameters and 32 – 64% of inter-subject variation in PRI, MPA, and PRU. High on-treatment platelet reactivity was present in 45% of healthy, homozygous CYP2C19 extensive metabolizer subjects, free of nicotine, alcohol, and co-medications, with witnessed clopidogrel 75 mg/d treatment for 9 days. Conclusions:Clopidogrel pharmacokinetics and pharmacodynamics vary widely despite rigorous exclusion or control of known disease, polymorphisms (CYP2C19, CYP3A5, ABCB1, PON1), non-compliance, co-medications, diet, smoking, alcohol, demographics, and pre-treatment platelet hyperreactivity. Thus, as yet unidentified factors contribute to high on-treatment platelet reactivity with its known increased risk of major adverse cardiovascular events. Disclosures:Frelinger:Takeda Pharmaceuticals: Research Funding; GLSynthesis: Research Funding. Bhatt:Medscape Cardiology: Membership on an entity’s Board of Directors or advisory committees; Boston VA Research Institute: Membership on an entity’s Board of Directors or advisory committees; Society of Chest Pain Centers: Membership on an entity’s Board of Directors or advisory committees; American Heart Association Get With The Guidelines Science Subcommittee: Chair, Chair Other; American College of Cardiology: Editor, Clinical Trials, Cardiosource Other; Duke Clinical Research Institute: clinical trial steering committees, clinical trial steering committees Other; Slack Publications: Chief Medical Editor, Cardiology Today Intervention Other; WebMD: CME steering committees, CME steering committees Other; Amarin, AstraZeneca, Bristol-Myers Squibb, Eisai, Ethicon, Medtronic, Sanofi Aventis, The Medicines Company: Research Funding; PLx Pharma, Takeda: unfunded research Other. Lee:Takeda Global Research & Development Center, Inc: Employment. Mulford:Takeda Global Research & Development Center, Inc: Employment. Wu:Takeda Global Research & Development Center, Inc: Employment. Nudurupati:Takeda Global Research & Development Center, Inc: Employment. Michelson:Eli Lilly: Data monitoring committee and idependent external monitor of clinical trials, Research Funding; Takeda: Research Funding; Oxygen Biotherapeutics: Research Funding; Alexion: Research Funding; Omthera: Research Funding.

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

IntroductionThrombolysis, 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 MethodsObservational, prospective study, including consecutive patients with elective angiography after thrombolytic therapy for STEMI. Every patient received antiplatelet therapy with loading doses of 250mg aspirin and 300mg clopidogrel on admission followed by 100mg aspirin and 75mg 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. Results41 patients fulfilled the inclusion criteria. Median time between thrombolysis and angiography was 2,5days (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 24h 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. ConclusionsPlatelet 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.

Abstract 94: Brief Discontinuation of Proton Pump Inhibitor Therapy Enhances Anti-Platelet Effects of Clopidogrel

Background: It has been suggested that proton pump inhibitor (PPI) administration may decrease clinical efficacy of clopidogrel. We have studied changes in platelet reactivity during brief discontinuation of chronic PPI administration in patients on clopidogrel maintenance therapy. Methods: Study was approved by institutional IRB and informed consent was obtained in all patients. Study population consisted of 9 outpatients (6 females, 68+/-6 years old) on chronic clopidogrel and PPI therapy. VerifyNow P2Y12 point of care assay was used to measure P2Y12 platelet reactivity unit (PRU) and percent platelet inhibition. Platelet reactivity was measured on PPI therapy, 10 days after stopping PPI, and 10 days after re-starting PPI. Control baseline platelet reactivity testing was conducted on each occasion and remained unchanged (on enrollment 321+/-44 PRU vs. off clopidogrel 327+/-33 PRU vs. on clopidogrel 342+/-36, p=0.159). Repeated measurements ANOVA analysis was used to study overall changes in platelet reactivity. Fisher’s protected least significance difference intervals test was used to compare individual groups. All tests were 2-tailed, p&lt;0.05 was considered significant. Results: We observed a significant reduction in platelet reactivity after PPI discontinuation (baseline PRU 205+/-111 vs. PRU 159+/-116 on day 10 post last PPI dose, p=0.028). Resuming PPI resulted in increased platelet reactivity (228+/-94 PRU after 10 days of PPI, p=0.002). Accordingly, PPI discontinuation was associated with significantly enhanced platelet inhibition (baseline percent inhibition 38+/-31 vs. 52+/-33% on day 10 after stopping PPI, p=0.029). Re-starting PPI resulted in significantly less effective platelet inhibition (percent inhibition 34+/-23% 10 days after PPI resumption, p=0.009). There were no significant differences in platelet reactivity (p=0.243) and percent inhibition (p=0.596) when baseline values were compared with ones obtained after 10 days of PPI treatment. Conclusions: We have documented dynamic changes in clopidogrel induced platelet inhibition associated with discontinuation and resumption of PPI therapy. Clopidogrel appears to provide significantly less effective platelet inhibition when PPI is administered simultaneously.

A Randomized, 2-Period, Crossover Design Study to Assess the Effects of Dexlansoprazole, Lansoprazole, Esomeprazole, and Omeprazole on the Steady-State Pharmacokinetics and Pharmacodynamics of Clopidogrel in Healthy Volunteers

The aim of this study was to assess the effects of different proton pump inhibitors (PPIs) on the steady-state pharmacokinetics and pharmacodynamics of clopidogrel. Metabolism of clopidogrel requires cytochrome P450s (CYPs), including CYP2C19. However, PPIs may inhibit CYP2C19, potentially reducing the effectiveness of clopidogrel. A randomized, open-label, 2-period, crossover study of healthy subjects (n = 160, age 18 to 55 years, homozygous for CYP2C19 extensive metabolizer genotype, confined, standardized diet) was conducted. Clopidogrel 75 mg with or without a PPI (dexlansoprazole 60 mg, lansoprazole 30 mg, esomeprazole 40 mg, or, as a positive control to maximize potential interaction and demonstrate assay sensitivity, omeprazole 80 mg) was given daily for 9 days. Pharmacokinetics and pharmacodynamics were assessed on days 9 and 10. Pharmacodynamic end-points were vasodilator-stimulated phosphoprotein P2Y(12) platelet reactivity index, maximal platelet aggregation to 5 and 20 μmol/l adenosine diphosphate, and VerifyNow P2Y12 platelet response units. Pharmacokinetic and pharmacodynamic responses with omeprazole demonstrated assay sensitivity. The area under the curve for clopidogrel active metabolite decreased significantly with esomeprazole but not with dexlansoprazole or lansoprazole. Similarly, esomeprazole but not dexlansoprazole or lansoprazole significantly reduced the effect of clopidogrel on vasodilator-stimulated phosphoprotein platelet reactivity index. All PPIs decreased the peak plasma concentration of clopidogrel active metabolite (omeprazole > esomeprazole > lansoprazole > dexlansoprazole) and showed a corresponding order of potency for effects on maximal platelet aggregation and platelet response units. Generation of clopidogrel active metabolite and inhibition of platelet function were reduced less by the coadministration of dexlansoprazole or lansoprazole with clopidogrel than by the coadministration of esomeprazole or omeprazole. These results suggest that the potential of PPIs to attenuate the efficacy of clopidogrel could be minimized by the use of dexlansoprazole or lansoprazole rather than esomeprazole or omeprazole.

Inhibition of platelet aggregation by prostaglandin E1 (PGE1) in diabetic patients during therapy with clopidogrel and aspirin

Diabetes mellitus (DM) is associated with increased platelet activation and reduced platelet inhibition by clopidogrel. Prostaglandin E1 (PGE1) stimulates adenyl cyclase activity in platelets and increases cyclic AMP concentrations, which inhibit Ca2+release and platelet aggregation induced by P2Y1 receptor activation. PGE1 is included in the VerifyNow P2Y12 assay to suppress P2Y1 induced platelet aggregation. We hypothesized that diabetes mellitus may be associated with altered response to PGE1 in subjects treated with clopidogrel. Subjects with established coronary artery disease who were taking clopidogrel 75 mg daily and aspirin for >14 days were enrolled (n = 96). Diabetic (n = 34) were compared with non-diabetic subjects (n = 62). VerifyNow P2Y12 assay and light transmittance aggregometry (LTA) were performed using ADP as agonist with and without addition of PGE1. Genomic DNA was genotyped for common cytochrome P450 (CYP) 2C19 variants using Taqman assays. Residual on-treatment platelet aggregation induced by 20 µM ADP was not significantly different between subjects with and without DM. Addition of 22 nM and 88 nM PGE1 to 20 µM ADP resulted in a significant reduction of maximal platelet aggregation (MPA). Residual LTA platelet aggregation with PGE1 and VerifyNow P2Y12 platelet reactivity were significantly higher in subjects with DM than those without DM and in carriers of CYP 2C19*2 polymorphism. We conclude that an impaired inhibitory response to PGE1 may contribute to the high platelet reactivity phenotype in subjects with DM treated with clopidogrel. Addition of PGE1 to ADP agonist platelet assays may identify subjects with blunted inhibitory response to prostaglandins and result in a higher proportion of subjects with DM being classified as non-responders.