Patrick Gladding

The Pharmacogenetics and Pharmacodynamics of Clopidogrel Response: An Analysis From the PRINC (Plavix Response in Coronary Intervention) Trial

OBJECTIVES This study assessed the effect of pharmacogenetics on the antiplatelet effect of clopidogrel. BACKGROUND Variability in clopidogrel response might be influenced by polymorphisms in genes coding for drug metabolism enzymes (cytochrome P450 [CYP] family), transport proteins (P-glycoprotein) and/or target proteins for the drug (adenosine diphosphate-receptor P2Y12). METHODS Sixty patients undergoing elective percutaneous coronary intervention in the randomized PRINC (Plavix Response in Coronary Intervention) trial had platelet function measured using the VerifyNow P2Y12 analyzer after a 600-mg or split 1,200-mg loading dose and after a 75- or 150-mg daily maintenance dosage. Polymerase chain reaction-based genotyping evaluated polymorphisms in the CYP2C19, CYP2C9, CYP3A4, CYP3A5, ABCB1, P2Y12, and CES genes. RESULTS CYP2C19*1*1 carriers had greater platelet inhibition 2 h after a 600-mg dose (median: 23%, range: 0% to 66%), compared with platelet inhibition in CYP2C19*2 or *4 carriers (10%, 0% to 56%, p = 0.029) and CYP2C19*17 carriers (9%, 0% to 98%, p = 0.026). CYP2C19*2 or *4 carriers had greater platelet inhibition with the higher loading dose than with the lower dose at 4 h (37%, 8% to 87% vs. 14%, 0% to 22%, p = 0.002) and responded better with the higher maintenance dose regimen (51%, 15% to 86% vs. 14%, 0% to 67%, p = 0.042). CONCLUSIONS Carriers of the CYP2C19*2 and *4 alleles showed reduced platelet inhibition after a clopidogrel 600-mg loading dose but responded to higher loading and maintenance dose regimens. Genotyping for the relevant gene polymorphisms may help to individualize and optimize clopidogrel treatment. (Australia New Zealand Clinical Trials Registry; ACTRN12606000129583).

The Antiplatelet Effect of Six Non-Steroidal Anti-Inflammatory Drugs and Their Pharmacodynamic Interaction With Aspirin in Healthy Volunteers

Patients with cardiovascular disease taking aspirin and some nonsteroidal anti-inflammatory drugs (NSAIDs) appear to have increased vascular events. This study was conducted to compare the ex vivo antiplatelet effects of 6 commonly used NSAIDs and to determine whether these agents antagonize the effect of aspirin. Platelet function was assessed by Platelet Function Analyzer 100 closure time in normal subjects in a randomized, blinded, multiple-crossover study. Platelet function was measured 12 hours after the administration of each NSAID. The NSAID was then given 2 hours before aspirin 300 mg, and platelet function was reassessed 24 hours later. At 12 hours after the administration of naproxen and tiaprofenic acid, closure time was significantly prolonged, whereas the other NSAIDs did not cause significant prolongations. Compared with placebo plus aspirin, closure time was significantly reduced when ibuprofen, indomethacin, naproxen, or tiaprofenic acid was given before aspirin. In conclusion, ibuprofen, indomethacin, naproxen, and tiaprofenic acid all block the antiplatelet effect of aspirin. Sulindac and celecoxib did not demonstrate any significant antiplatelet effect or reduce the antiplatelet of aspirin and, therefore, of the NSAIDs evaluated may be the drugs of choice for patients requiring aspirin and NSAIDs.

The Antiplatelet Effect of Higher Loading and Maintenance Dose Regimens of Clopidogrel: The PRINC (Plavix Response in Coronary Intervention) Trial

OBJECTIVES This study evaluated the antiplatelet effect of a higher loading and maintenance dose regimen of clopidogrel and a possible drug interaction with verapamil. BACKGROUND Clopidogrel loading doses above 600 mg have not resulted in more rapid or complete platelet inhibition. Higher maintenance dosages may be more effective than 75 mg/day. METHODS A double-blind, randomized, placebo-controlled trial was undertaken in 60 patients undergoing percutaneous coronary intervention. All patients received clopidogrel 600 mg at the start of the procedure. Using a 2 x 2 design, patients were allocated to clopidogrel 600 mg given 2 h later or matching placebo, and to verapamil 5 mg intra-arterial or placebo. Platelet function was measured using the VerifyNow P2Y12 analyzer (Accumetrics Ltd., San Diego, California) at 2, 4, and 7 h. Patients were further randomized to receive a clopidogrel 75 or 150 mg once daily, with platelet function assessed after 1 week. RESULTS Two hours after the second dose of clopidogrel or placebo, platelet inhibition was 42 +/- 27% with clopidogrel, compared with 24 +/- 22% with placebo (p = 0.0006). By 5 h after the second dose, platelet inhibition was 49 +/- 30% with clopidogrel, compared with 29 +/- 22% with placebo (p = 0.01). No drug interaction was seen with verapamil. A clopidogrel maintenance dosage of 150 mg daily for 1 week resulted in greater platelet inhibition than 75 mg daily (50 +/- 28% vs. 29 +/- 19%, p = 0.01). CONCLUSIONS In an unselected population undergoing percutaneous coronary intervention a clopidogrel 1,200-mg loading dose, given as two 600-mg doses 2 h apart, results in more rapid and complete platelet inhibition than a single 600-mg dose. A maintenance dosage of 150 mg daily produces greater platelet inhibition than 75 mg daily. (The PRINC trial; ACTRN12606000129583).

Pharmacogenetic testing for clopidogrel using the rapid INFINITI analyzer: a dose-escalation study.

OBJECTIVES Our aim was to assess whether a higher clopidogrel maintenance dose has a greater antiplatelet effect in CYP2C19*2 allele carriers compared with noncarriers. BACKGROUND Clopidogrel is a prodrug that is biotransformed by the cytochrome P450 enzymes CYP2C19, 2C9, and 3A4, 2B6, 1A2. The CYPC219*2 loss of function variant has been associated with a reduced antiplatelet response to clopidogrel and a 3-fold risk of stent thrombosis. METHODS Forty patients on standard maintenance dosage clopidogrel (75 mg), for 9.4 +/- 9.2 weeks, were enrolled into a dose escalation study. Platelet function was assessed at baseline and after 1 week of 150 mg once daily using the VerifyNow platelet function analyzer (Accumetrics Ltd., San Diego, California). Genomic DNA was hybridized to a BioFilmChip microarray on the INFINITI analyzer (AutoGenomics Inc., Carlsbad, California) and analyzed for the CYP19*2, *4, *17, and CYP2C9*2, *3 polymorphisms. RESULTS Platelet inhibition increased over 1 week, mean +8.6 +/- 13.5% (p = 0.0003). Carriers of the CYP2C19*2 allele had significantly reduced platelet inhibition at baseline (median 18%, range 0% to 72%) compared with wildtype (wt) (median 59%, range 11% to 95%, p = 0.01) and at 1 week (p = 0.03). CYP2C19*2 allele carriers had an increase in platelet inhibition of (mean +9 +/- 11%, p = 0.03) and reduction in platelet reactivity (mean -26 +/- 38 platelet response unit, p = 0.04) with a higher dose. Together CYP2C19*2 and CYP2C9*3 loss of function carriers had a greater change in platelet inhibition with 150 mg daily than wt/wt (+10.9% vs. +0.7%, p = 0.04). CONCLUSIONS Increasing the dose of clopidogrel in patients with nonresponder polymorphisms can increase antiplatelet response. Personalizing clopidogrel dosing using pharmacogenomics may be an effective method of optimizing treatment.

Antiplatelet drug nonresponsiveness

The response to most medication, including antiplatelet drugs, is highly variable between individuals. Observational studies have shown that nonresponders to antiplatelet agents appear to have an increased incidence of vascular events. This review article reviews the background, mechanisms, and evidence in support of the clinical significance of this phenomenon.

Percutaneous Closure of a Left Ventricular Free-Wall Rupture Site

An 86-year-old woman who lived independently was referred for consideration of percutaneous closure of a left ventricular free wall rupture site. Ten years earlier, she had undergone aortic valve replacement with a Carpentier-Edwards bioprosthesis (Edwards Lifesciences, Irvine, Calif) and received a single saphenous vein graft to the right coronary artery. Five years later, at the age of 81, she had an inferolateral myocardial infarction and an acute rupture of the left ventricular free wall. The resultant false …

Feasibility, Safety, and Efficacy of a Novel Polymeric Pimecrolimus-Eluting Stent: Traditional Pre-Clinical Safety End Points Failed to Predict 6-Month Clinical Angiographic Results

OBJECTIVES The aim of this study was to determine the safety and efficacy of a novel pimecrolimus-eluting stent in a porcine coronary model and in a phase I clinical trial. BACKGROUND Rapamycin- and paclitaxel-eluting stents reduce the need for repeat intervention by limiting neointimal hyperplasia but might cause delayed healing, pre-disposing patients to late stent thrombosis. Because inflammation plays a key role in restenosis, pimecrolimus, an anti-inflammatory drug, might reduce restenosis without adversely affecting re-endothelialization. METHODS We evaluated a novel polymeric pimecrolimus-eluting stent covered with a thin parylene C diffusion barrier in a porcine coronary model and in a phase I human clinical trial. The clinical study was a prospective, nonrandomized, first-in-human hypothesis-generating study that enrolled 15 patients who had a single de novo native coronary stenosis. RESULTS At 28 days and 3 months in the porcine model, histopathologic indicators predicted safety and biocompatibility when stents coated with polymer only, drug only, and 2 drug-polymer formulations were compared with bare-metal stents (BMS). In the phase I clinical trial, 15 patients had successful implantation of pimecrolimus-eluting stents. By 6 months, no patient suffered death, myocardial infarction, or stent thrombosis. However, the angiographic restenosis (61%), mean late loss (1.44 mm), and repeat target lesion revascularization (53%) were significantly higher than historical BMS controls. Whereas the primary end point was percent volume obstruction, restenosis was so severe that operators performed intravascular ultrasound examination in only 6 patients. CONCLUSIONS Pimecrolimus-eluting stents induced an exaggerated neointimal hyperplasia at 6 months in comparison with historical controls.

A Multi-feature Reproducibility Assessment of Mass Spectral Data in Clinical Proteomic Studies

BackgroundThe use of mass spectrometry to investigate disease-associated proteins among thousands of candidates simultaneously creates challenges with the evaluation of operational and biological variation. Traditional statistical methods, which evaluate reproducibility of a single feature, are likely to provide an inadequate assessment of reproducibility. This paper proposes a systematic approach for the evaluation of the global reproducibility of multidimensional mass spectral data at the post-identification stage.MethodsThe proposed systematic approach combines dimensional reduction and permutation to test and summarize the reproducibility. First, principal component analysis is applied to the mean quantities from identified features of paired replicated samples. An eigenvalue test is used to identify the number of significant principal components which reflect the underlying correlation pattern of the multiple features. Second, a simulation-based permutation test is applied to the derived paired principal components. Third, a modified form of Bland Altman or MA plot is produced to visualize agreement between the replicates. Last, a discordance index is used to summarize the agreement.ResultsApplication of this method to data from both a cardiac liquid chromatography tandem mass spectrometry experiment with iTRAQ labeling and simulation experiments derived from an ovarian cancer SELDI-MS experiment demonstrate that the proposed global reproducibility test is sensitive to the simulated systematic bias when the sample size is above 15. The two proposed test statistics (max t statistics and a sign score statistic) for the permutation tests are shown to be reliable.ConclusionThe methodology presented in this paper provides a systematic approach for the global measurement of reproducibility in clinical proteomic studies.