Vera H.M. Deneer

Comparison of Platelet Function Tests in Predicting Clinical Outcome in Patients Undergoing Coronary Stent Implantation

Context High on-treatment platelet reactivity is associated with atherothrombotic events following coronary stent implantation. Objective To evaluate the capability of multiple platelet function tests to predict clinical outcome. Design, Setting, and Patients Prospective, observational, single-center cohort study of 1069 consecutive patients taking clopidogrel undergoing elective coronary stent implantation between December 2005 and December 2007. On-treatment platelet reactivity was measured in parallel by light transmittance aggregometry, Verify Now P2Y12 and Platelet works assays, and the IMPACT-R and the platelet function analysis system (PFA-100) (with the Dade PFA collagen/adenosine diphosphate (ADP) cartridge and Innovance PFA P2Y). Cutoff values for high on-treatment platelet reactivity were established by receiver operating characteristic curve (ROC) analysis. Main Outcome Measurement The primary end point was defined as a composite of all-cause death, nonfatal acute myocardial infarction, stent thrombosis, and ischemic stroke. The primary safety end point included TIMI (Thrombolysis In Myocardial Infarction) criteria major and minor bleeding. Results Kaplan-Meier analysis demonstrated that at 1-year follow-up, the primary end point occurred more frequently in patients with high on-treatment platelet reactivity when assessed by light transmittance aggregometry (52 [11.7%; 95% confidence interval {CI}, 8.9%-15.0%] vs 36 [6.0%;95%CI, 4.2%-8.2%] P.001; n=1049),Verify Now (54 [13.3%; 95% CI, 10.2%-17.0%] vs 37 [5.7%; 95% CI, 4.1%-7.8%]P.001; n=1052), Platelet works (33 [12.6%; 95% CI, 8.8%-17.2%] vs 21 [6.1%;95% CI, 3.8%-9.2%] P=.005; n=606), and Innovance PFA P2Y (18 [12.2%; 95%CI; 7.4%-18.6%] vs 28 [6.3%; 95% CI, 4.3%-8.9%] P=.02; n=588). ROC-curve analysis demonstrated that light transmittance aggregometry (area under the curve[AUC], 0.63; 95% CI, 0.58-0.68), Verify Now (AUC, 0.62; 95% CI, 0.57-0.67), and Platelet works (AUC, 0.61; 95% CI, 0.53-0.69) had modest ability to discriminate between patients with and without primary end point at 1-year follow-up. The IMPACT-R(n=905) and the Siemens PFA Collagen/ADP (n=812) were unable to discriminate between patients with and without the primary end point at 1-year follow-up (all AUCs included 0.50 in the CI). None of the tests identified patients at risk for bleeding. Conclusions Of the platelet function tests assessed, light transmittance aggregometry,Verify Now, Platelet works, and Innovance PFA P2Y were significantly associated with the primary end point. However, the predictive accuracy of these 4 tests was only modest. None of the tests provided accurate prognostic information to identify patients at higher risk of bleeding following stent implantation. Trial Registration clinical trials.gov Identifier: NCT00352014 [corrected].

CYP2C19*2 and CYP2C9*3 alleles are associated with stent thrombosis: a case–control study

AIMS despite treatment with clopidogrel on top of aspirin, stent thrombosis (ST) still occurs being the most serious complication after percutaneous coronary interventions (PCIs). In this study, we aimed to determine the effect of variations in genes involved in the absorption (ABCB1 C1236T, G2677T/A, C3435T), metabolism (CYP2C19*2 and *3, CYP2C9*2 and *3, CYP3A4*1B and CYP3A5*3), and pharmacodynamics (P2Y1 A1622G) of clopidogrel on the occurrence of ST. METHODS AND RESULTS the selected genetic variants were assessed in 176 subjects who developed ST while on dual antiplatelet therapy with aspirin and clopidogrel and in 420 control subjects who did not develop adverse cardiovascular events, including ST, within 1 year after stenting. The timing of the definite ST was acute in 66, subacute in 87, and late in 23 cases. The presence of the CYP2C19*2 and CYP2C9*3 variant alleles was significantly associated with ST (OR(adj): 1.7, 95% CI: 1.0-2.6, P = 0.018 and OR(adj): 2.4, 95% CI: 1.0-5.5, P = 0.043, respectively). The influence of CYP2C19*2 (OR(adj): 2.5, 95% CI: 1.1-5.5, P = 0.026) and CYP2C9*3 (OR(adj): 3.3, 95% CI: 1.1-9.9, P = 0.031) was most strongly associated with subacute ST. No significant associations of the other genetic variations and the occurrence of ST were found. CONCLUSION carriage of the loss-of-function alleles CYP2C19*2 and CYP2C9*3 increases the risk on ST after PCI.

Variability in on-treatment platelet reactivity explained by CYP2C19*2 genotype is modest in clopidogrel pretreated patients undergoing coronary stenting

Background An inadequate response to clopidogrel is mainly attributable to the variable formation of its active metabolite. The CYP2C19*2 loss-of-function polymorphism leads to reduced generation of the active metabolite and is, similarly to high on-treatment platelet reactivity (HPR), associated with recurrent atherothrombotic events following coronary stent implantation. Aim To determine the relative contribution of CYP2C19*2 genotype to HPR. Methods and results CYP2C19*2 genotyping and platelet function testing using 5 and 20 μmol/l ADP-induced light transmittance aggregometry (LTA), the PlateletWorks assay and the VerifyNow P2Y12 assay, were performed in 1069 clopidogrel pretreated patients undergoing elective coronary stenting (POPular study, http://clinicalTrials.gov/ NCT00352014). The relative contributions of CYP2C19*2 genotype and clinical variables to the interindividual variability of on-treatment platelet reactivity and the occurrence of HPR were established using multivariate regression models. CYP2C19*2 carrier status was associated with a more frequent occurrence of HPR. CYP2C19*2 genotype alone could explain 5.0%, 6.2%, 4.4% and 3.7% of the variability in 5 and 20 μmol/l ADP-induced LTA, the PlateletWorks assay and the VerifyNow P2Y12 assay, respectively, which increased to 13.0%, 15.2%, 5.6% and 20.6% when clinical variables were considered as well. Besides the CYP2C19*2 genotype, multiple clinical variables could be identified as independent predictors of HPR, including age, gender, body mass index, diabetes mellitus, clopidogrel loading dose regimen, use of amlodipine and platelet count. Conclusion The CYP2C19*2 loss-of-function polymorphism is associated with a more frequent occurrence of HPR. However, the part of the interindividual variability in on-treatment platelet reactivity explained by CYP2C19*2 genotype is modest.

Besides CYP2C19*2, the variant allele CYP2C9*3 is associated with higher on-clopidogrel platelet reactivity in patients on dual antiplatelet therapy undergoing elective coronary stent implantation

Introduction The prodrug clopidogrel plays an important role in the prevention of thrombotic events in patients undergoing coronary stenting. However, a substantial number of atherothrombotic events still occur, which can partially be explained by heightened residual platelet reactivity. Several studies report that the genetic variation in CYP2C19 (*2) is associated with an impaired response to clopidogrel. Objectives To evaluate the effect of genetic variants affecting clopidogrels absorption (ABCB1 C1236T, G2677T/A, C3435T), metabolism (CYP2C9*2, *3, CYP2C19*3, CYP3A4*1B, and CYP3A5*3), and pharmacodynamics (P2Y1 A1622G) on top of the influence of CYP2C19*2 on platelet reactivity in patients undergoing elective coronary stenting on dual antiplatelet therapy. Methods Platelet function was assessed by light transmittance aggregometry and VerifyNow P2Y12 assay in 428 consecutive patients. Patients were either on chronic clopidogrel maintenance therapy (75 mg/day for >5 days before the intervention) or received a 300 mg clopidogrel loading dose (1–5 days before the intervention, followed by 75 mg/day). Linear and logistic regression models were used to assess the associations between genetic variants and platelet reactivity and poor responder status. Results In both the treatment groups, CYP2C19*2-carriage was associated with higher platelet reactivity (P<0.03) and poor responder status; 75 mg group: adjusted odds ratio (ORadj): 3.8, 95% confidence interval (CI): 2.0–7.2, 300 mg group: ORadj: 4.1, 95% CI: 1.6–10.4. In the 300 mg group, CYP2C9*3-carriage was associated with higher platelet reactivity (P<0.05) and poor responder status (ORadj: 11.1, 95% CI: 1.6–78.8, P=0.016). Conclusion Besides CYP2C19*2, the variant allele CYP2C9*3 plays an important role in the response to clopidogrel in patients on dual antiplatelet therapy undergoing coronary stenting.

CYP2C19 genotype-guided antiplatelet therapy in ST-segment elevation myocardial infarction patients-Rationale and design of the Patient Outcome after primary PCI (POPular) Genetics study

RATIONALE In patients with ST-segment elevation myocardial infarction (STEMI) who undergo primary percutaneous coronary intervention (pPCI), the use of dual antiplatelet therapy is essential to prevent atherothrombotic complications. Therefore, patients are treated with acetylsalicylic acid and clopidogrel, prasugrel, or ticagrelor. Clopidogrel, however, shows a major interindividual variation in antiplatelet effect, which is correlated to an increase in atherothrombotic events in patients with high platelet reactivity. This interindividual variation is partly a result of CYP2C19 genetic variants. Ticagrelor and prasugrel reduce atherothrombotic events but increase bleeding rate and drug costs, as compared with clopidogrel. CYP2C19-based tailoring of antiplatelet therapy might be beneficial to STEMI patients. STUDY DESIGN POPular Genetics (NCT01761786) is a randomized, open-label, multicenter trial involving 2,700 STEMI patients who undergo pPCI. Patients are randomized to CYP2C19 genotyping or routine ticagrelor or prasugrel treatment. In the genotyping group, *1/*1 (wild-type) patients receive clopidogrel, and patients carrying 1 or 2 *2 or *3 loss-of-function alleles receive ticagrelor or prasugrel. The primary net clinical benefit end point is the composite of death, (recurrent) myocardial infarction, definite stent thrombosis, stroke, and Platelet Inhibition and Patient Outcomes (PLATO) major bleeding at 1 year. Primary safety end point is the composite of (PLATO) major and minor bleeding. Cost-effectiveness and quality of life will be assessed by calculating quality-adjusted life-years, net costs per life-year, and per quality-adjusted life-year gained. CONCLUSION The POPular Genetics study is the first large-scale trial comparing CYP2C19 genotype-guided antiplatelet therapy to a nontailored strategy in terms of net clinical benefit, safety, and cost-effectiveness.

From evidence based medicine to mechanism based medicine. Reviewing the role of pharmacogenetics

Aim of the review The translation of evidence based medicine to a specific patient presents a considerable challenge. We present by means of the examples nortriptyline, tramadol, clopidogrel, coumarins, abacavir and antipsychotics the discrepancy between available pharmacogenetic information and its implementation in daily clinical practice. Method Literature review. Results A mechanism based approach may be helpful to personalize medicine for the individual patient to which pharmacogenetics may contribute significantly. The lack of consistency in what we accept in bioequivalence and in pharmacogenetics of drug metabolising enzymes is discussed and illustrated with the example of nortriptyline. The impact of pharmacogenetics on examples like tramadol, clopidogrel, coumarins and abacavir is described. Also the present status of the polymorphisms of 5-HT2A and C receptors in antipsychotic-induced weight gain is presented as a pharmacodynamic example with until now a greater distance to clinical implementation. Conclusion The contribution of pharmacogenetics to tailor-made pharmacotherapy, which especially might be of value for patients deviating from the average, has not yet reached the position it seems to deserve.

Rationale and design of POPular-TAVI: antiPlatelet therapy fOr Patients undergoing Transcatheter Aortic Valve Implantation

BACKGROUND Despite improving experience and techniques, ischemic and bleeding complications after transcatheter aortic valve implantation (TAVI) remain prevalent and impair survival. Current guidelines recommend the temporary addition of clopidogrel in the initial period after TAVI to prevent thromboembolic events. However, explorative studies suggest that this is associated with a higher rate of major bleeding without a decrease in thromboembolic complications. METHODS The POPular TAVI trial is a prospective randomized, controlled, open-label multicenter clinical trial to test the hypothesis that monotherapy with aspirin or oral anticoagulation (OAC) after TAVI is safer than the addition of clopidogrel for 3 months, without compromising clinical benefit. This trial encompasses 2 cohorts: cohort A, patients are randomized 1:1 to aspirin vs aspirin + clopidogrel, and cohort B, patients on OAC therapy are randomized 1:1 to OAC vs OAC + clopidogrel. Primary outcome is freedom from non-procedure-related bleeding at 1 year. Secondary net-clinical benefit outcome is freedom from the composite of cardiovascular death, non-procedural-related bleeding, myocardial infarction, or stroke at 1 year. The primary outcome is analyzed for superiority, whereas the secondary outcome is analyzed for noninferiority. Recruitment began in February 2014, and the trial will continue until a total of 1,000 patients (684 expected in cohort A and 316 in cohort B) are included and followed up for 1 year. SUMMARY The POPular TAVI trial (NCT02247128) is the first large randomized controlled trial to test if monotherapy with aspirin or OAC vs additional clopidogrel after TAVI reduces bleeding with a favorable net-clinical benefit.

Sulfonylureas and on-clopidogrel platelet reactivity in type 2 diabetes mellitus patients.

Clopidogrel is a prodrug that needs to be converted in vivo by several cytochrome (CYP) P450 iso-enzymes to become active. Both clopidogrel and the oral hypoglycemic drug class sulfonylureas are metabolized by the iso-enzyme CYP2C9. The objective of the study was to evaluate the relationship of sulfonylureas and on-clopidogrel platelet reactivity in type 2 diabetes mellitus patients undergoing elective coronary stent implantation. In this prospective, observational study, on-clopidogrel platelet reactivity was quantified using adenosine diphosphate (ADP)-induced light transmittance aggregometry in 139 type 2 diabetes mellitus patients undergoing elective coronary stent implantation treated with clopidogrel and aspirin. High on-clopidogrel platelet reactivity was defined as >70.7% platelet reactivity to 20 µmol/L ADP. A total of 53 patients (38.1%) were on concomitant treatment with sulfonylureas. The remaining 86 patients were on other hypoglycemic drugs. On-clopidogrel platelet reactivity was significantly higher in patients with concomitant sulfonylurea treatment as compared to patients without concomitant sulfonylurea treatment (for 5 µmol/L ADP: 46.0% ± 11.8 vs. 40.6% ± 16.0; p = 0.035, adjusted p = 0.032 and for 20 µmol/L ADP: 64.6% ± 10.8 vs. 58.7% ± 15.5; p = 0.019, adjusted p = 0.017). The concomitant use of sulfonylureas was associated with a 2.2-fold increased risk of high on-clopidogrel platelet reactivity (OR 2.2, 95% CI 1.1–4.7, p = 0.039 and after adjustment for confounders: ORadj 2.0, 95% CI 1.0–5.7, p = 0.048). Concomitant treatment with sulfonylureas might be associated with decreased platelet inhibition by clopidogrel in type 2 diabetes mellitus patients on dual antiplatelet therapy undergoing elective coronary stent implantation.

Effect of oxybutynin on exercise‐induced sweating in healthy individuals

Objectives: Oxybutynin has been proven to be effective in patients with generalized hyperhidrosis. Some dermatoses aggravate as a result of sweating. Therefore, oxybutynin might also be useful in such normohidrotic patients. The aim was to evaluate the efficacy and safety of different doses of oxybutynin on exercise‐induced sweating in healthy individuals. Methods: Two randomized, double‐blind, placebo‐controlled, cross‐over studies were performed, in which two different dosages (2.5 and 5 mg) of oxybutynin were tested. The degree of sweating was determined by transepidermal water loss (TEWL) measurement on the forearm and the hand during exercise. Furthermore, the effectiveness was evaluated by means of the individuals global assessment score, and side effects were noted. Results: No significant differences between oxybutynin and placebo were found on the forearm and the hand at both dosages of oxybutynin with respect to TEWL values and the individuals global assessment score. Side effects consisted of diarrhoea, dizziness, dry mouth and dry eyes. Conclusions: In this model, oxybutynin did not result in inhibition of exercise‐induced sweating in healthy volunteers.

Exercise-induced sweating in healthy subjects as a model to predict a drug's sweat-reducing properties in hyperhydrosis: a prospective, placebo-controlled, double-blind study.

The aim of this study was to develop a model to evaluate the efficacy of drugs with expected sweat-reducing properties in healthy subjects in order to select candidate drugs for the systemic treatment of primary generalized hyperhidrosis. A randomized, double-blind, placebo-controlled cross-over study was performed in 8 healthy subjects. Sweating was induced by exercise. The degree of sweating at different exercise levels was determined by measurement of transepidermal water loss. Either the anticholinergic drug oxybutynin or placebo was given before measurements started. No statistically significant differences in transepidermal water loss between active treatment and placebo were found at the different exercise levels. This is noteworthy, as oxybutynin has been proven successful in patients with generalized hyperhidrosis. Thus, the present model does not mimic the situation in patients with primary generalized hyperhidrosis. This may be because this form of hyperhidrosis is not caused only by sympathetic overactivity, as described in the literature, but is based on more complex mechanisms. Further investigations are required fully to understand the pathophysiology of primary generalized hyperhidrosis in order to develop effective human test models.