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Optimization of anticoagulation with warfarin for stroke prevention: pharmacogenetic considerations. Am J Ther 2012; 18:e55-66. [PMID: 20335792 DOI: 10.1097/mjt.0b013e3181cea0cd] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Warfarin is a cornerstone of oral anticoagulation for stroke prevention. Anticoagulation with warfarin in patients with atrial fibrillation is over twice as effective in secondary prevention of stroke as any other tested alternatives, including all other antithrombotic drugs or surgical interventions. General belief is that warfarin is capable of preventing 20 ischemic strokes for every hemorrhagic one it causes. However, warfarin is one of the most feared agents as a result of its woeful safety profile and difficulties in maintaining the proper daily dose. Recent research in pharmacogenetics predominantly focused on elucidating the influence of individual genetic predispositions to administered warfarin. Although the incorporation of genotype information improves the accuracy of adequate dose prediction, an improvement in anticoagulation control or a reduction in hemorrhagic complications has not been yet convincingly demonstrated. It is clear that identifying an individual patient's risk for hemorrhage on warfarin will require more broad clinical and genetic studies. Future research focused on patients with stroke should concentrate on defining the possible differences, especially focusing on predicting bleeding events in general and intracranial hemorrhages in particular. The purpose of this review is to summarize the existing evidence about pharmacogenetics of warfarin in general, especially focusing on stroke prevention.
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Wang M, Lang X, Cui S, Fei K, Zou L, Cao J, Wang L, Zhang S, Wu X, Wang Y, Ji Q. Clinical application of pharmacogenetic-based warfarin-dosing algorithm in patients of Han nationality after rheumatic valve replacement: a randomized and controlled trial. Int J Med Sci 2012; 9:472-9. [PMID: 22927772 PMCID: PMC3427951 DOI: 10.7150/ijms.4637] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/23/2012] [Accepted: 07/24/2012] [Indexed: 12/02/2022] Open
Abstract
BACKGROUND The polymorphisms of VKORC1 and CYP2C9 play increasingly important roles in the inter-individual variability in warfarin dose. This study aimed to evaluate the feasibility of clinical application of pharmacogenetic-based warfarin-dosing algorithm in patients of Han nationality with rheumatic heart disease after valve replacement in a randomized and controlled trial. METHODS One hundred and one consecutive patients of Han nationality with rheumatic heart disease undergoing valve surgery were enrolled and randomly assigned to an experimental group (n=50, based on CYP2C9 and VKORC1 genotypes, pharmacogenetic-based "predicted warfarin dose" for 3 days and then was adjusted to INR until stable warfarin maintenance dose) or a control group (n=51, 2.5mg/d for 3 days and then was adjusted to INR until stable warfarin maintenance dose). All included patients were followed for 50 days after initiation of warfarin therapy. The primary end-point was the time to reach a stable warfarin maintenance dose. RESULTS During the follow-up, 84.0% patients in the experimental group and 58.8% patients in the control group received warfarin maintenance dose. Compared with control group, patients in the experimental group had shorter mean time elapse from initiation of warfarin therapy until warfarin maintenance dose (27.5±1.8 d versus 34.7±1.8 d, p<0.001). Cox regression revealed that group (HR for experimental versus control group: 1.568, 95%CI 1.103-3.284) and age were two significant variables related to the time elapse from initiation of warfarin therapy until warfarin maintenance dose. The predicted warfarin maintenance dose was prominently correlated with the actual warfarin maintenance dose (r=0.684, p<0.001). CONCLUSION Based on CYP2C9 and VKORC1 genotypes, the pharmacogenetic-based warfarin-dosing algorithm may shorten the time elapse from initiation of warfarin therapy until warfarin maintenance dose. It is feasible for the clinical application of the pharmacogenetic-based warfarin-dosing algorithm in patients of Han nationality with rheumatic heart disease after valve replacement.
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Affiliation(s)
- MingSong Wang
- Department of Thoracic Cardiovascular Surgery, Xinhua Hospital of Shanghai Jiaotong University School of Medicine, Shanghai, P.R. China
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Genetic polymorphisms affecting drug metabolism: recent advances and clinical aspects. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2012; 63:137-67. [PMID: 22776641 DOI: 10.1016/b978-0-12-398339-8.00004-5] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Though current knowledge of pharmacogenetic factors relevant to drug metabolism is fairly comprehensive and this should facilitate translation to the clinic, there are a number of gaps in knowledge. Recent studies using both conventional and novel approaches have added to our knowledge of pharmacogenetics of drug metabolism. Genome-wide association studies have provided new insights into the major contribution of cytochromes P450 to response to therapeutic agents such as coumarin anticoagulants and clopidogrel as well as to caffeine and nicotine. Recent advances in understanding of factors affecting gene expression, both regulation by transcription factors and by microRNA and epigenetic factors, have added to understanding of variation in expression of genes such as CYP3A4 and CYP2E1. The implementation of testing for pharmacogenetic polymorphisms in prescription of selected anticancer drugs and cardiovascular agents is considered in detail, with current controversies and barriers to implementation of pharmacogenetic testing assessed. Though genotyping for thiopurine methyltransferase is now common prior to prescription of thiopurines, genotyping for other pharmacogenetic polymorphisms prior to drug prescription remains uncommon. However, it seems likely that it will become more widespread as both increased evidence that certain pharmacogenetic tests are valuable and cost-effective and more accessible genotyping methods become available.
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154
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Amici S, Paciaroni M, Agnelli G, Caso V. Gene-drug interaction in stroke. Stroke Res Treat 2011; 2011:212485. [PMID: 22135769 PMCID: PMC3216369 DOI: 10.4061/2011/212485] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2011] [Revised: 07/05/2011] [Accepted: 09/02/2011] [Indexed: 01/09/2023] Open
Abstract
Stroke is the third cause of mortality and one of most frequent causes of long-term neurological disability, as well as a complex disease that results from the interaction of environmental and genetic factors. The focus on genetics has produced a large number of studies with the objective of revealing the genetic basis of cerebrovascular diseases. Furthermore, pharmacogenetic research has investigated the relation between genetic variability and drug effectiveness/toxicity. This review will examine the implications of pharmacogenetics of stroke; data on antihypertensives, statins, antiplatelets, anticoagulants, and recombinant tissue plasminogen activator will be illustrated.
Several polymorphisms have been studied and some have been associated with positive drug-gene interaction on stroke, but the superiority of the genotype-guided approach over the clinical approach has not been proved yet; for this reason, it is not routinely recommended.
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Affiliation(s)
- Serena Amici
- Stroke Unit, Division of Cardiovascular Medicine, University of Perugia, Santa Maria della Misericordia Hospital, Sant'Andrea delle Fratte, 06126 Perugia, Italy
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Perlstein TS, Goldhaber SZ, Nelson K, Joshi V, Morgan TV, Lesko LJ, Lee JY, Gobburu J, Schoenfeld D, Kucherlapati R, Freeman MW, Creager MA. The Creating an Optimal Warfarin Nomogram (CROWN) Study. Thromb Haemost 2011; 107:59-68. [PMID: 22116191 DOI: 10.1160/th11-08-0568] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2011] [Accepted: 10/23/2011] [Indexed: 11/05/2022]
Abstract
A significant proportion of warfarin dose variability is explained by variation in the genotypes of the cytochrome P450 CYP2C9 and the vitamin K epoxide reductase complex, VKORC1, enzymes that influence warfarin metabolism and sensitivity, respectively. We sought to develop an optimal pharmacogenetic warfarin dosing algorithm that incorporated clinical and genetic information. We enroled patients initiating warfarin therapy. Genotyping was performed of the VKORC1, -1639G>A, the CYP2C9*2, 430C>T, and the CYP2C9*3, 1075C>A genotypes. The initial warfarin dosing algorithm (Algorithm A) was based upon established clinical practice and published warfarin pharmacogenetic information. Subsequent dosing algorithms (Algorithms B and Algorithm C) were derived from pharmacokinetic / pharmacodynamic (PK/PD) modelling of warfarin dose, international normalised ratio (INR), clinical and genetic factors from patients treated by the preceding algorithm(s). The primary outcome was the time in the therapeutic range, considered an INR of 1.8 to 3.2. A total of 344 subjects are included in the study analyses. The mean percentage time within the therapeutic range for each subject increased progressively from Algorithm A to Algorithm C from 58.9 (22.0), to 59.7 (23.0), to 65.8 (16.9) percent (p = 0.04). Improvement also occurred in most secondary endpoints, which included the per-patient percentage of INRs outside of the therapeutic range (p = 0.004), the time to the first therapeutic INR (p = 0.07), and the time to achieve stable therapeutic anticoagulation (p < 0.001). In conclusion, warfarin pharmacogenetic dosing can be optimised in real time utilising observed PK/PD information in an adaptive fashion.
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Affiliation(s)
- Todd S Perlstein
- Division of Cardiovascular Medicine, Brigham and Women's Hospital, Boston, MA 02115, USA
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Factor VII R353Q genetic polymorphism is associated with altered warfarin sensitivity among CYP2C9 *1/*1 carriers. Eur J Clin Pharmacol 2011; 68:617-27. [DOI: 10.1007/s00228-011-1143-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2011] [Accepted: 10/07/2011] [Indexed: 10/15/2022]
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Abstract
Patients vary in their responses to drug therapy, and some of that variability is genetically determined. This review outlines general approaches used to identify genetic variation that influences drug response. Examples from specific therapeutic areas are presented, such as cholesterol management, arrhythmias, heart failure, hypertension, warfarin anticoagulation, and antiplatelet agents. A brief view of potential pathways to implementation is presented.
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Affiliation(s)
- Dan M Roden
- Departments of Medicine and Pharmacology, Vanderbilt University School of Medicine, Nashville, TN 37232-0575, USA.
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158
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Cavallari LH, Jeong H, Bress A. Role of cytochrome P450 genotype in the steps toward personalized drug therapy. PHARMACOGENOMICS & PERSONALIZED MEDICINE 2011; 4:123-36. [PMID: 23226058 PMCID: PMC3513224 DOI: 10.2147/pgpm.s15497] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/04/2011] [Indexed: 12/19/2022]
Abstract
Genetic polymorphism for cytochrome 450 (P450) enzymes leads to interindividual variability in the plasma concentrations of many drugs. In some cases, P450 genotype results in decreased enzyme activity and an increased risk for adverse drug effects. For example, individuals with the CYP2D6 loss-of-function genotype are at increased risk for ventricular arrhythmia if treated with usual does of thioridazine. In other cases, P450 genotype may influence the dose of a drug required to achieve a desired effect. This is the case with warfarin, with lower doses often necessary in carriers of a variant CYP2C9*2 or *3 allele to avoid supratherapeutic anticoagulation. When a prodrug, such as clopidogrel or codeine, must undergo hepatic biotransformation to its active form, a loss-of-function P450 genotype leads to reduced concentrations of the active drug and decreased drug efficacy. In contrast, patients with multiple CYP2D6 gene copies are at risk for opioid-related toxicity if treated with usual doses of codeine-containing analgesics. At least 25 drugs contain information in their US Food and Drug Administration-approved labeling regarding P450 genotype. The CYP2C9, CYP2C19, and CYP2D6 genes are the P450 genes most often cited. To date, integration of P450 genetic information into clinical decision making is limited. However, some institutions are beginning to embrace routine P450 genotyping to assist in the treatment of their patients. Genotyping for P450 variants may carry less risk for discrimination compared with genotyping for disease-associated variants. As such, P450 genotyping is likely to lead the way in the clinical implementation of pharmacogenomics. This review discusses variability in the CYP2C9, CYP2C19, and CYP2D6 genes and the implications of this for drug efficacy and safety.
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Affiliation(s)
- Larisa H Cavallari
- Department of Pharmacy Practice ; Department of Biopharmaceutical Sciences, College of Pharmacy, University of Illinois at Chicago, Chicago, IL, USA
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159
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Xu H, Jiang M, Oetjens M, Bowton EA, Ramirez AH, Jeff JM, Basford MA, Pulley JM, Cowan JD, Wang X, Ritchie MD, Masys DR, Roden DM, Crawford DC, Denny JC. Facilitating pharmacogenetic studies using electronic health records and natural-language processing: a case study of warfarin. J Am Med Inform Assoc 2011; 18:387-91. [PMID: 21672908 DOI: 10.1136/amiajnl-2011-000208] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
OBJECTIVE DNA biobanks linked to comprehensive electronic health records systems are potentially powerful resources for pharmacogenetic studies. This study sought to develop natural-language-processing algorithms to extract drug-dose information from clinical text, and to assess the capabilities of such tools to automate the data-extraction process for pharmacogenetic studies. MATERIALS AND METHODS A manually validated warfarin pharmacogenetic study identified a cohort of 1125 patients with a stable warfarin dose, in which 776 patients were managed by Coumadin Clinic physicians, and the remaining 349 patients were managed by their providers. The authors developed two algorithms to extract weekly warfarin doses from both data sets: a regular expression-based program for semistructured Coumadin Clinic notes; and an advanced weekly dose calculator based on an existing medication information extraction system (MedEx) for narrative providers' notes. The authors then conducted an association analysis between an automatically extracted stable weekly dose of warfarin and four genetic variants of VKORC1 and CYP2C9 genes. The performance of the weekly dose-extraction program was evaluated by comparing it with a gold standard containing manually curated weekly doses. Precision, recall, F-measure, and overall accuracy were reported. Associations between known variants in VKORC1 and CYP2C9 and warfarin stable weekly dose were performed with linear regression adjusted for age, gender, and body mass index. RESULTS The authors' evaluation showed that the MedEx-based system could determine patients' warfarin weekly doses with 99.7% recall, 90.8% precision, and 93.8% accuracy. Using the automatically extracted weekly doses of warfarin, the authors successfully replicated the previous known associations between warfarin stable dose and genetic variants in VKORC1 and CYP2C9.
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Affiliation(s)
- Hua Xu
- Department of Biomedical Informatics, School of Medicine, Vanderbilt University, Nashville, Tennessee 37232, USA.
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160
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Abstract
Patient phenotypes in pharmacological pain treatment varies between individuals, which could be partly assigned to their genotypes regarding the targets of classical analgesics (OPRM1, PTGS2) or associated signalling pathways (KCNJ6). Translational and genetic research have identified new targets, for which new analgesics are being developed. This addresses voltage-gated sodium, calcium and potassium channels, for which SCN9A, CACNA1B, KCNQ2 and KCNQ3, respectively, are primary gene candidates because they code for the subunits of the respective channels targeted by analgesics currently in clinical development. Mutations in voltage gated transient receptor potential (TRPV) channels are known from genetic pain research and may modulate the effects of analgesics under development targeting TRPV1 or TRPV3. To this add ligand-gated ion channels including nicotinic acetylcholine receptors, ionotropic glutamate-gated receptors and ATP-gated purinergic P2X receptors with most important subunits coded by CHRNA4, GRIN2B and P2RX7. Among G protein coupled receptors, δ-opioid receptors (coded by OPRD1), cannabinoid receptors (CNR1 and CNR2), metabotropic glutamate receptors (mGluR5 coded by GRM5), bradykinin B(1) (BDKRB1) and 5-HT(1A) (HTR1A) receptors are targeted by new analgesic substances. Finally, nerve growth factor (NGFB), its tyrosine kinase receptor (NTRK1) and the fatty acid amide hydrolase (FAAH) have become targets of interest. For most of these genes, functional variants have been associated with neuro-psychiatric disorders and not yet with analgesia. However, research on the genetic modulation of pain has already identified variants in these genes, relative to pain, which may facilitate the pharmacogenetic assessments of new analgesics. The increased number of candidate pharmacogenetic modulators of analgesic actions may open opportunities for the broader clinical implementation of genotyping information.
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Affiliation(s)
- Jörn Lötsch
- pharmazentrum frankfurt/ZAFES, Institute of Clinical Pharmacology, Goethe-University, Frankfurt am Main, Germany.
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161
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Johnson JA, Gong L, Whirl-Carrillo M, Gage BF, Scott SA, Stein CM, Anderson JL, Kimmel SE, Lee MTM, Pirmohamed M, Wadelius M, Klein TE, Altman RB. Clinical Pharmacogenetics Implementation Consortium Guidelines for CYP2C9 and VKORC1 genotypes and warfarin dosing. Clin Pharmacol Ther 2011; 90:625-9. [PMID: 21900891 PMCID: PMC3187550 DOI: 10.1038/clpt.2011.185] [Citation(s) in RCA: 472] [Impact Index Per Article: 33.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Warfarin is a widely used anticoagulant with a narrow therapeutic index and large interpatient variability in the dose required to achieve target anticoagulation. Common genetic variants in the cytochrome P450-2C9 (CYP2C9) and vitamin K-epoxide reductase complex (VKORC1) enzymes, in addition to known nongenetic factors, account for ~50% of warfarin dose variability. The purpose of this article is to assist in the interpretation and use of CYP2C9 and VKORC1 genotype data for estimating therapeutic warfarin dose to achieve an INR of 2-3, should genotype results be available to the clinician. The Clinical Pharmacogenetics Implementation Consortium (CPIC) of the National Institutes of Health Pharmacogenomics Research Network develops peer-reviewed gene-drug guidelines that are published and updated periodically on http://www.pharmgkb.org based on new developments in the field.(1).
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Affiliation(s)
- J A Johnson
- Department of Pharmacotherapy and Translational Research, College of Pharmacy, and Center for Pharmacogenomics, University of Florida, Gainesville, Florida, USA.
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162
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Pharmacogenetics and cost-effectiveness analysis: a two-way street. Drug Discov Today 2011; 16:873-7. [DOI: 10.1016/j.drudis.2011.08.015] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2011] [Revised: 08/23/2011] [Accepted: 08/24/2011] [Indexed: 11/23/2022]
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Degoma EM, Rivera G, Lilly SM, Usman MHU, Mohler ER. Personalized vascular medicine: individualizing drug therapy. Vasc Med 2011; 16:391-404. [PMID: 22003003 PMCID: PMC3761360 DOI: 10.1177/1358863x11422251] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Personalized medicine refers to the application of an individual's biological fingerprint - the comprehensive dataset of unique biological information - to optimize medical care. While the principle itself is straightforward, its implementation remains challenging. Advances in pharmacogenomics as well as functional assays of vascular biology now permit improved characterization of an individual's response to medical therapy for vascular disease. This review describes novel strategies designed to permit tailoring of four major pharmacotherapeutic drug classes within vascular medicine: antiplatelet therapy, antihypertensive therapy, lipid-lowering therapy, and antithrombotic therapy. Translation to routine clinical practice awaits the results of ongoing randomized clinical trials comparing personalized approaches with standard of care management.
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Affiliation(s)
- Emil M Degoma
- Division of Cardiovascular Medicine, University of Pennsylvania, Philadelphia, USA.
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164
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Johnson JA, Cavallari LH, Beitelshees AL, Lewis JP, Shuldiner AR, Roden DM. Pharmacogenomics: application to the management of cardiovascular disease. Clin Pharmacol Ther 2011; 90:519-31. [PMID: 21918509 PMCID: PMC3190669 DOI: 10.1038/clpt.2011.179] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The past decade has seen substantial advances in cardiovascular pharmacogenomics. Genetic determinants of response to clopidogrel and warfarin have been defined, resulting in changes to the product labels for these drugs that suggest the use of genetic information as a guide for therapy. Genetic tests are available, as are guidelines for incorporation of genetic information into patient-care decisions. These guidelines and the literature supporting them are reviewed herein. Significant advances have also been made in the pharmacogenomics of statin-induced myopathy and the response to β-blockers in heart failure, although the clinical applications of these findings are less clear. Other areas hold promise, including the pharmacogenomics of antihypertensive drugs, aspirin, and drug-induced long-QT syndrome (diLQTS). The potential value of pharmacogenomics in the discovery and development of new drugs is also described. In summary, pharmacogenomics has current applications in the management of cardiovascular disease, with clinically relevant data continuing to mount.
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Affiliation(s)
- J A Johnson
- Department of Pharmacotherapy and Translational Research and Center for Pharmacogenomics, University of Florida, Gainesville, Florida, USA.
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165
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Abstract
BACKGROUND Pharmacogenetics has emerged as a new tool for the optimization of drug therapy. Although the pharmacogenetics concept was first recognized at least 50 years ago, clinical testing to determine pharmacogenetic traits is still relatively rare, and many hurdles are markedly slowing its development. There is a lot of literature and speculation about potential ethical challenges in genetic and pharmacogenetic testing, yet few researchers have actually examined the attitudes of health care professionals regarding the clinical application of these tests. OBJECTIVE In this article, we aim to review the current literature on health care professionals' perceptions of the role of pharmacogenetic data and describe the attitudes of medical students when faced with a clinical pharmacogenetic testing scenario. METHODS A group of 59 third-year medical students from the American University of Beirut Medical Center were asked to answer a questionnaire about pharmacogenetic testing after being exposed to a clinical scenario of a patient who was diagnosed with mild Alzheimer Disease (AD) and hence was a candidate for therapy with one of the acetylcholinesterase (AChE) inhibitors. RESULTS The students indicated that they would respect patients' confidentiality and inform them about the test results and therapeutic plan, but they would not be as open about bad prognoses. They did not agree on the therapeutic plan that would follow a pharmacogenetic test result and were uncertain about potential patient discrimination in insurability. CONCLUSION Our and others' findings demonstrate the existence and seriousness of several challenges pertaining to pharmacogenetic applications in the clinical setting. Further training and education are needed for health care professionals, since they are the ones who will most probably request these tests in the near future.
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166
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Prospective evaluation of a pharmacogenetics-guided warfarin loading and maintenance dose regimen for initiation of therapy. Blood 2011; 118:3163-71. [DOI: 10.1182/blood-2011-03-345173] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Abstract
Single-nucleotide polymorphisms in genes that affect warfarin metabolism (cytochrome P450 2C9 gene, CYP2C9) and response (vitamin K epoxide reductase complex 1 gene, VKORC1) have an important influence on warfarin therapy, particularly during initiation; however, there is a lack of consensus regarding the optimal pharmacogenetics-based initiation strategy. We conducted a prospective cohort study in which patients requiring warfarin therapy for atrial fibrillation or venous thromboembolism were initiated with a novel pharmacogenetics-initiation protocol (WRAPID, Warfarin Regimen using A Pharmacogenetics-guided Initiation Dosing) that incorporated loading and maintenance doses based on genetics, clinical variables, and response (n = 167, followed up for 90 days), to assess the influence of genetic variations on anticoagulation responses. Application of the WRAPID algorithm resulted in a negligible influence of genetic variation in VKORC1 or CYP2C9 on time to achievement of first therapeutic response (P = .52, P = .28) and risk of overanticoagulation (P = .64, P = .96). After adjustment for covariates, time to stable anticoagulation was not influenced by VKORC1 or CYP2C9 genotype. Importantly, time spent within or above the therapeutic range did not differ among VKORC1 and CYP2C9 genotype groups. Moreover, the overall time course of the anticoagulation response among the genotype groups was similar and predictable. We demonstrate the clinical utility of genetics-guided warfarin initiation with the WRAPID protocol to provide safe and optimal anticoagulation therapy for patients with atrial fibrillation or venous thromboembolism.
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167
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Howard R, Leathart JBS, French DJ, Krishan E, Kohnke H, Wadelius M, van Schie R, Verhoef T, Maitland-van der Zee AH, Daly AK, Barallon R. Genotyping for CYP2C9 and VKORC1 alleles by a novel point of care assay with HyBeacon® probes. Clin Chim Acta 2011; 412:2063-9. [PMID: 21827742 DOI: 10.1016/j.cca.2011.07.013] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2011] [Accepted: 07/09/2011] [Indexed: 02/03/2023]
Abstract
BACKGROUND Coumarin anticoagulants such as warfarin are used to treat and prevent thromboembolic events in patients. The required dosage is difficult to predict and the risk of over or under anticoagulation are dependent on several environmental and clinical factors, such as concurrent medication, diet, age and genotype for polymorphisms in two genes CYP2C9 and VKORC1. METHODS A novel fluorescent PCR genotyping assay using HyBeacon® probes, was developed to enable clinical staff to genotype the CYP2C9*2 and CYP2C9*3 alleles and the VKORC1 G-1639A polymorphism directly from unextracted blood samples. A prototype PCR instrument, Genie 1, suitable for point of care use was developed to carry out the assays. The panel of tests was validated by analysing blood samples from 156 individuals and comparing genotypes with data obtained using DNA samples from the same individuals. The accuracy of genotypes obtained with the Genie 1 was compared against results from well validated real time PCR and PCR-restriction fragment length polymorphism analysis. RESULTS Identical results were obtained for the newly developed HyBeacon® method and the validation method in all cases except for one where no result was obtained for the VKORC1 polymorphism on the Genie instrument. The samples used for validation represented all six possible *2 and *3 allele-related CYP2C9 genotypes and all three VKORC1 G-1639A genotypes. CONCLUSIONS We observed excellent accuracy for the newly developed method which can determine genotype in less than 2 h.
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Ferraldeschi R, Newman WG. Pharmacogenetics and pharmacogenomics: a clinical reality. Ann Clin Biochem 2011; 48:410-7. [DOI: 10.1258/acb.2011.011084] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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169
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Affiliation(s)
- Thomas P Cappola
- Penn Cardiovascular Institute and the Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, USA.
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170
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Abstract
Although postoperative pain remains incompletely controlled in some settings, increased understanding of its mechanisms and the development of several therapeutic approaches have substantially improved pain control in past years. Advances in our understanding of the process of nociception have led to insight into gene-based pain therapy, the development of acute opioid-induced hyperalgesia, and persistent postsurgical pain. Use of specific analgesic techniques such as regional analgesia could improve patient outcomes. We also examine the development of new analgesic agents and treatment modalities and regimens for acute postoperative pain.
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Affiliation(s)
- Christopher L Wu
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University and School of Medicine, Baltimore, MD 21287, USA.
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172
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Musunuru K. Current Role of Pharmacogenomics in Cardiovascular Medicine. CURRENT TREATMENT OPTIONS IN CARDIOVASCULAR MEDICINE 2011; 13:302-12. [DOI: 10.1007/s11936-011-0129-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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Springer JA, Iannotti NV, Kane MD, Haynes K, Sprague JE. Pharmacogenomics training using an instructional software system. AMERICAN JOURNAL OF PHARMACEUTICAL EDUCATION 2011; 75:32. [PMID: 21519421 PMCID: PMC3073107 DOI: 10.5688/ajpe75232] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2010] [Accepted: 11/15/2010] [Indexed: 05/09/2023]
Abstract
OBJECTIVES To implement an elective course in pharmacogenomics designed to teach pharmacy students about the fundamentals of pharmacogenomics and the anticipated changes it will bring to the profession. DESIGN The 8 sessions of the course covered the basics of pharmacogenomics, genomic biotechnology, implementation of pharmacogenetics in pharmacy, information security and privacy, ethical issues related to the use of genomic data, pharmacoepidemiology, and use and promotion of GeneScription, a software program designed to mimic the professional pharmacy environment. ASSESSMENT Student grades were based on completion of a patient education pamphlet, a 2-page paper on pharmacogenomics, and precourse and postcourse survey instruments. In the postcourse survey, all students strongly agreed that genomic data could be used to determine the optimal dose of a drug and genomic data for metabolizing enzymes could be stored in a safe place. Students also were more willing to submit deoxyribonucleic acid (DNA) data for genetic profiling and better understood how DNA analysis is performed after completing the course. CONCLUSIONS An elective course in pharmacogenomics equipped pharmacy students with the basic knowledge necessary to make clinical decisions based on pharmacogenomic data and to teach other healthcare professionals and patients about pharmacogenomics. For personalized medicine to become a reality, all pharmacists and pharmacy students must learn this knowledge and these skills.
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Affiliation(s)
- John A. Springer
- Department of Computer and Information Technology, Purdue University
| | | | - Michael D. Kane
- Department of Computer and Information Technology, Purdue University
- Raabe College of Pharmacy, Ohio Northern University
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Finkelman BS, Gage BF, Johnson JA, Brensinger CM, Kimmel SE. Genetic warfarin dosing: tables versus algorithms. J Am Coll Cardiol 2011; 57:612-8. [PMID: 21272753 DOI: 10.1016/j.jacc.2010.08.643] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/22/2010] [Revised: 07/16/2010] [Accepted: 08/24/2010] [Indexed: 01/21/2023]
Abstract
OBJECTIVES The aim of this study was to compare the accuracy of genetic tables and formal pharmacogenetic algorithms for warfarin dosing. BACKGROUND Pharmacogenetic algorithms based on regression equations can predict warfarin dose, but they require detailed mathematical calculations. A simpler alternative, recently added to the warfarin label by the U.S. Food and Drug Administration, is to use genotype-stratified tables to estimate warfarin dose. This table may potentially increase the use of pharmacogenetic warfarin dosing in clinical practice; however, its accuracy has not been quantified. METHODS A retrospective cohort study of 1,378 patients from 3 anticoagulation centers was conducted. Inclusion criteria were stable therapeutic warfarin dose and complete genetic and clinical data. Five dose prediction methods were compared: 2 methods using only clinical information (empiric 5 mg/day dosing and a formal clinical algorithm), 2 genetic tables (the new warfarin label table and a table based on mean dose stratified by genotype), and 1 formal pharmacogenetic algorithm, using both clinical and genetic information. For each method, the proportion of patients whose predicted doses were within 20% of their actual therapeutic doses was determined. Dosing methods were compared using McNemar's chi-square test. RESULTS Warfarin dose prediction was significantly more accurate (all p < 0.001) with the pharmacogenetic algorithm (52%) than with all other methods: empiric dosing (37%; odds ratio [OR]: 2.2), clinical algorithm (39%; OR: 2.2), warfarin label (43%; OR: 1.8), and genotype mean dose table (44%; OR: 1.9). CONCLUSIONS Although genetic tables predicted warfarin dose better than empiric dosing, formal pharmacogenetic algorithms were the most accurate.
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Affiliation(s)
- Brian S Finkelman
- Center for Clinical Epidemiology and Biostatistics, Department of Biostatistics and Epidemiology, University of Pennsylvania School of Medicine, Philadelphia, USA
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Wright DFB, Duffull SB. Development of a bayesian forecasting method for warfarin dose individualization. Pharm Res 2011; 28:1100-11. [PMID: 21301936 DOI: 10.1007/s11095-011-0369-x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2010] [Accepted: 01/10/2011] [Indexed: 12/17/2022]
Abstract
PURPOSE The aim of this study was to develop a Bayesian dose individualization tool for warfarin. This was incorporated into the freely available software TCIWorks ( www.tciworks.info ) for use in the clinic. METHODS All pharmacokinetic and pharmacodynamic (PKPD) models for warfarin in the medical literature were identified and evaluated against two warfarin datasets. The model with the best external validity was used to develop an optimal design for Bayesian parameter control. The performance of this design was evaluated using simulation-estimation techniques. Finally, the model was implemented in TCIWorks. RESULTS A recently published warfarin KPD model was found to provide the best fit for the two external datasets. Optimal sampling days within the first 14 days of therapy were found to be days 3, 4, 5, 11, 12, 13 and 14. Simulations and parameter estimations suggested that the design will provide stable estimates of warfarin clearance and EC50. A single patient example showed the potential clinical utility of the method in TCIWorks. CONCLUSIONS A Bayesian dose individualization tool for warfarin was developed. Future research to assess the predictive performance of the tool in warfarin patients is required.
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Affiliation(s)
- Daniel F B Wright
- School of Pharmacy, University of Otago, PO Box 56, Dunedin 9054, New Zealand.
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Verhoef TI, Redekop WK, Darba J, Geitona M, Hughes DA, Siebert U, de Boer A, Maitland-van der Zee AH, Barallon R, Briz M, Daly A, Haschke-Becher E, Kamali F, Kirchheiner J, Manolopoulos VG, Pirmohamed M, Rosendaal FR, van Schie RMF, Wadelius M. A systematic review of cost-effectiveness analyses of pharmacogenetic-guided dosing in treatment with coumarin derivatives. Pharmacogenomics 2011; 11:989-1002. [PMID: 20602617 DOI: 10.2217/pgs.10.74] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Anticoagulant therapy with coumarin derivatives is often sub- or supra-therapeutic, resulting in an increased risk of thromboembolic events or hemorrhage, respectively. Pharmacogenetic-guided dosing has been proposed as an effective way of reducing bleeding rates. Clinical trials to confirm the safety, efficacy and effectiveness of this strategy are ongoing, but in addition, it is also necessary to consider the cost-effectiveness of this strategy. This article describes the findings of a systematic review of published cost-effectiveness analyses of pharmacogenetic-guided dosing of coumarin derivatives. Similarities and differences in the approaches used were examined and the quality of the analyses was assessed. The results of the analyses are not sufficient to determine whether or not pharmacogenetic-guided dosing of coumarins is cost effective. More reliable cost-effectiveness estimates need to become available before it is possible to recommend whether or not this strategy should be applied in clinical practice.
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Affiliation(s)
- Talitha I Verhoef
- Division of Pharmacoepidemiology & Pharmacotherapy, Utrecht Institute for Pharmaceutical Sciences, Utrecht University, PO Box 80 082, 3508 TB Utrecht, The Netherlands
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Cen HJ, Zeng WT, Leng XY, Huang M, Chen X, Li JL, Huang ZY, Bi HC, Wang XD, He YL, He F, Zhou RN, Zheng QS, Zhao LZ. CYP4F2 rs2108622: a minor significant genetic factor of warfarin dose in Han Chinese patients with mechanical heart valve replacement. Br J Clin Pharmacol 2011; 70:234-40. [PMID: 20653676 DOI: 10.1111/j.1365-2125.2010.03698.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT * Genetic polymorphisms of VKORC1 and CYP2C9 are known to influence warfarin dosage. * Recent studies among Caucasians showed that polymorphisms of CYP4F2 also play a role in warfarin pharmacogenetics. * The contribution of CYP4F2 variants to the variability inwarfarin dose requirement in Chinese subjects remains to be investigated. WHAT THIS STUDY ADDS * This research was to study the effect of CYP4F2 variants on warfarin requirements in the Han Chinese population. * This study developed a multiple regression model including CYP2C9, VKORC1 3673G>A, CYP4F2 genotypes and age, weight, combination use of amiodarone which could explain 56.1% of the individual variability in warfarin dose CYP4F2 could explain 4% of the variance in warfarin dose. * We found that one novel genotypic polymorphism 5417G>T for Asp36Tyr, which was identified as an important marker of warfarin resistance, was absent in the Han Chinese population in our study. AIMS The objective of this study was to assess the effect of the CYP4F2 on the daily stable warfarin dose requirement in Han Chinese patients with mechanical heart valve replacement (MHVR). METHODS From March 2007 to November 2008, 222 Han Chinese MHVR patients were recruited in our study. VKORC1 3673G>A, 5417G>T, CYP2C9*3 and CYP4F2 rs2108622 were genotyped by using the polymerase chain reaction restriction fragment length polymorphism method (PCR-RFLP). Polymorphisms of VKORC1 9041G>A were detected by direct sequencing. Multiple linear regression analysis was used to investigate the contribution of CYP4F2. RESULTS The CYP4F2 rs2108622 CT/TT group took a significantly higher stable warfarin dose (3.2 mg day(-1)) than the CC group (2.9 mg day(-1), 95% CI 0.2, 1.0, P= 0.033). The multiple linear regression model included VKORC1 3673G>A, CYP2C9, CYP4F2 genotypes and clinical characteristics. The model could explain 56.1% of the variance in stable warfarin dose in Han Chinese patients with MHVR. CYP4F2 contributed about 4% to the variance in the warfarin dose. There was no variation in the SNPs of VKORC1 5417G>T. CONCLUSION CYP4F2 is a minor significant factor of individual variability in the stable warfarin dose in Han Chinese patients with MHVR. The effect of CYP2C9 and VKORC1 genotypes on variability in the stable warfarin dose had also been confirmed.
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Affiliation(s)
- Han-Jing Cen
- School of Pharmaceutical Sciences, Sun Yat-sen University, China
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Rosenberg G, Marshall LS, Caraco Y. The Neuroprotective Agent DP-b99 Does Not Interact with S-warfarin In Vivo Despite Significant CYP2C9 Inhibition In Vitro. Basic Clin Pharmacol Toxicol 2010; 108:289-92. [PMID: 21414144 DOI: 10.1111/j.1742-7843.2010.00654.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Verhoef TI, Schalekamp T, Redekop WK, de Boer A, Maitland-van der Zee AH. Clinical and economic consequences of pharmacogenetic-guided dosing of warfarin. Expert Rev Pharmacoecon Outcomes Res 2010; 10:375-8. [PMID: 20715914 DOI: 10.1586/erp.10.42] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Patients using warfarin for oral anticoagulant therapy need to be frequently monitored because of warfarin's narrow therapeutic range and the large variation in dose requirements among patients. Patients receiving the wrong dose have an increased risk of bleeding or thromboembolic events. The required dose is influenced by environmental factors, such as gender, age, diet and concomitant medication, as well as genetic factors. Pharmacogenetic testing prior to warfarin initiation might improve dosing accuracy and, therefore, safety and efficacy of warfarin treatment. Meckley et al. studied the clinical consequences and costs of genotyping before warfarin treatment. The results of their study suggest that pharmacogenetic-guided dosing of patients initiating warfarin could improve health (quality-adjusted life-years) but at a high cost per quality-adjusted life-year gained. Owing to the inevitable assumptions that have to be made in all cost-effectiveness models, great uncertainty remains regarding the cost-effectiveness of pharmacogenetic-guided warfarin dosing.
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Affiliation(s)
- Talitha I Verhoef
- Utrecht University, Faculty of Science, Division of Pharmacoepidemiology and Pharmacotherapy, PO Box 80 082, 3508 TB Utrecht, The Netherlands
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Pendleton RC, Rodgers GM, Hull RD. Established Venous Thromboembolism Therapies: Heparin, Low Molecular Weight Heparins, and Vitamin K Antagonists, with a Discussion of Heparin-Induced Thrombocytopenia. Clin Chest Med 2010; 31:691-706. [DOI: 10.1016/j.ccm.2010.07.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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French B, Joo J, Geller NL, Kimmel SE, Rosenberg Y, Anderson JL, Gage BF, Johnson JA, Ellenberg JH. Statistical design of personalized medicine interventions: the Clarification of Optimal Anticoagulation through Genetics (COAG) trial. Trials 2010; 11:108. [PMID: 21083927 PMCID: PMC3000386 DOI: 10.1186/1745-6215-11-108] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2010] [Accepted: 11/17/2010] [Indexed: 11/16/2022] Open
Abstract
Background There is currently much interest in pharmacogenetics: determining variation in genes that regulate drug effects, with a particular emphasis on improving drug safety and efficacy. The ability to determine such variation motivates the application of personalized drug therapies that utilize a patient's genetic makeup to determine a safe and effective drug at the correct dose. To ascertain whether a genotype-guided drug therapy improves patient care, a personalized medicine intervention may be evaluated within the framework of a randomized controlled trial. The statistical design of this type of personalized medicine intervention requires special considerations: the distribution of relevant allelic variants in the study population; and whether the pharmacogenetic intervention is equally effective across subpopulations defined by allelic variants. Methods The statistical design of the Clarification of Optimal Anticoagulation through Genetics (COAG) trial serves as an illustrative example of a personalized medicine intervention that uses each subject's genotype information. The COAG trial is a multicenter, double blind, randomized clinical trial that will compare two approaches to initiation of warfarin therapy: genotype-guided dosing, the initiation of warfarin therapy based on algorithms using clinical information and genotypes for polymorphisms in CYP2C9 and VKORC1; and clinical-guided dosing, the initiation of warfarin therapy based on algorithms using only clinical information. Results We determine an absolute minimum detectable difference of 5.49% based on an assumed 60% population prevalence of zero or multiple genetic variants in either CYP2C9 or VKORC1 and an assumed 15% relative effectiveness of genotype-guided warfarin initiation for those with zero or multiple genetic variants. Thus we calculate a sample size of 1238 to achieve a power level of 80% for the primary outcome. We show that reasonable departures from these assumptions may decrease statistical power to 65%. Conclusions In a personalized medicine intervention, the minimum detectable difference used in sample size calculations is not a known quantity, but rather an unknown quantity that depends on the genetic makeup of the subjects enrolled. Given the possible sensitivity of sample size and power calculations to these key assumptions, we recommend that they be monitored during the conduct of a personalized medicine intervention. Trial Registration clinicaltrials.gov: NCT00839657
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Affiliation(s)
- Benjamin French
- Department of Biostatistics and Epidemiology, University of Pennsylvania School of Medicine, 423 Guardian Drive, Philadelphia, Pennsylvania 19104, USA.
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Donohue MM, Tirschwell DL. Implications of pharmacogenetic testing for patients taking warfarin or clopidogrel. Curr Neurol Neurosci Rep 2010; 11:52-60. [PMID: 21046289 DOI: 10.1007/s11910-010-0157-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Our knowledge of the pharmacogenetics of warfarin and clopidogrel continues to expand as we learn more about the individual genetic variations that contribute to the drugs' efficacy and toxicity. We aim to review the recent developments in the field and discuss the clinical implications for the treatment of ischemic stroke patients. Despite recent advances, there is still insufficient data to suggest that routine genetic testing improves outcomes in patients treated with warfarin or clopidogrel for prevention of stroke.
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Affiliation(s)
- Megan M Donohue
- Department of Neurology, Harborview Medical Center, 325 9th Avenue, Box 359775, Seattle, WA 98104, USA.
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Pirmohamed M. Acceptance of Biomarker-Based Tests for Application in Clinical Practice: Criteria and Obstacles. Clin Pharmacol Ther 2010; 88:862-6. [DOI: 10.1038/clpt.2010.245] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Joo J, Geller NL, French B, Kimmel SE, Rosenberg Y, Ellenberg JH. Prospective alpha allocation in the Clarification of Optimal Anticoagulation through Genetics (COAG) trial. Clin Trials 2010; 7:597-604. [PMID: 20693186 PMCID: PMC3111931 DOI: 10.1177/1740774510381285] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND The Clarification of Optimal Anticoagulation through Genetics (COAG) trial is a large, multicenter, double-blinded, randomized trial to determine whether use of a genotype-guided dosing algorithm (using clinical and genetic information) to initiate warfarin treatment will improve anticoagulation status when compared to a dosing algorithm using only clinical information. PURPOSE This article describes prospective alpha allocation and balanced alpha allocation for the design of the COAG trial. METHODS The trial involves two possibly heterogeneous populations, which can be distinguished by the difference in warfarin dose as predicted by the two algorithms. A statistical approach is detailed, which allows an overall comparison as well as a comparison of the primary endpoint in the subgroup for which sufficiently different doses are predicted by the two algorithms. Methods of allocating alpha for these analyses are given - a prospective alpha allocation and allocating alpha so that the two analyses have equal power, which we call a 'balanced alpha allocation.' RESULTS We show how to include an analysis of the primary endpoint in a subgroup as a co-primary analysis. Power can be improved by incorporating the correlation between the overall and subgroup analyses in a prospective alpha allocation approach. Balanced alpha allocation for the full cohort and subgroup tests to achieve the same desired power for both of the primary analyses is discussed in detail. LIMITATIONS In the COAG trial, it is impractical to stratify the randomization on subgroup membership because genetic information may not be available at the time of randomization. If imbalances in the treatment arms in the subgroup are found, they will need to be addressed. CONCLUSIONS The design of the COAG trial assures that the subgroup in which the largest treatment difference is expected is elevated to a co-primary analysis. Incorporating the correlation between the full cohort and the subgroup analyses provides an improvement in power for the subgroup comparison, and further improvement may be achieved via a balanced alpha allocation approach when the parameters involved in the sample size calculation are reasonably well estimated.
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Affiliation(s)
- Jungnam Joo
- Office of Biostatistics Research, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, USA.
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Extending and evaluating a warfarin dosing algorithm that includes CYP4F2 and pooled rare variants of CYP2C9. Pharmacogenet Genomics 2010; 20:407-13. [PMID: 20442691 DOI: 10.1097/fpc.0b013e328338bac2] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
OBJECTIVE Warfarin dosing remains challenging because of its narrow therapeutic window and large variability in dose response. We sought to analyze new factors involved in its dosing and to evaluate eight dosing algorithms, including two developed by the International Warfarin Pharmacogenetics Consortium (IWPC). METHODS we enrolled 108 patients on chronic warfarin therapy and obtained complete clinical and pharmacy records; we genotyped single nucleotide polymorphisms relevant to the VKORC1, CYP2C9, and CYP4F2 genes using integrated fluidic circuits made by Fluidigm. RESULTS When applying the IWPC pharmacogenetic algorithm to our cohort of patients, the percentage of patients within 1 mg/d of the therapeutic warfarin dose increases from 54% to 63% using clinical factors only, or from 38% using a fixed-dose approach. CYP4F2 adds 4% to the fraction of the variability in dose (R) explained by the IWPC pharmacogenetic algorithm (P<0.05). Importantly, we show that pooling rare variants substantially increases the R for CYP2C9 (rare variants: P=0.0065, R=6%; common variants: P=0.0034, R=7%; rare and common variants: P=0.00018; R=12%), indicating that relatively rare variants not genotyped in genome-wide association studies may be important. In addition, the IWPC pharmacogenetic algorithm and the Gage (2008) algorithm perform best (IWPC: R=50%; Gage: R=49%), and all pharmacogenetic algorithms outperform the IWPC clinical equation (R=22%). VKORC1 and CYP2C9 genotypes did not affect long-term variability in dose. Finally, the Fluidigm platform, a novel warfarin genotyping method, showed 99.65% concordance between different operators and instruments. CONCLUSION CYP4F2 and pooled rare variants of CYP2C9 significantly improve the ability to estimate warfarin dose.
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Gene-based warfarin dosing compared with standard of care practices in an orthopedic surgery population: a prospective, parallel cohort study. Ther Drug Monit 2010; 32:338-45. [PMID: 20386359 DOI: 10.1097/ftd.0b013e3181d925bb] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Warfarin remains a difficult drug to manage due to a narrow therapeutic range and wide interindividual variability in dose requirements. The relationship between warfarin sensitivity and CYP2C9 and VKORC1 variants is strong, and is the basis for several proposed dosing algorithms. Here a gene-based dosing algorithm was compared with standard of care dosing in patients receiving warfarin to prevent venous thromboembolism after joint replacement surgery. Participants (n = 229) were adults (> or =18 years) undergoing elective total hip or knee arthroplasty and receiving warfarin under the direction of a dedicated anticoagulation services team. Patients were assigned to genotype-based or standard of care dosing arms in an alternating fashion. Initial dose for patients was determined by validated algorithms from Sconce 2005 and Pendleton 2008. Management was based on INR, but dose was adjusted less aggressively for patients with CYP2C9 variants. The primary endpoint was reduction in the incidence of adverse events; additional endpoints included time to first therapeutic INR (1.8-2.9), time to first supratherapeutic INR, and percent of INR determinations that fell below, within, and above the therapeutic range. Endpoints did not achieve statistical significance, possibly due to the management of this study by a dedicated and experienced anticoagulation services team. Trends in the data suggest that patients with genetic variants progressed to a therapeutic INR faster than patients in whom genetic variants were not detected, and there were fewer adverse events in the genotype-based dosing arm. In addition, the results of this study confirm those of others demonstrating clear relationship of genotype for CYP2C9 and VKORC1 with warfarin dose requirements; as the number of variants in these genes increases, the dose requirement decreases. Of note, the gene-based algorithm utilized here significantly underpredicted the dose requirement for participants with no variants, indicating that patients with no variants should be managed with a different algorithm than patients who inherit genetic variants in CYP2C9 and/or VKORC1. In conclusion, gene-based dosing did not improve warfarin management as defined by INR dose response, using the described protocols for implementation. Findings suggest alternative strategies for dosing based on the presence or absence of genetic variants is needed.
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Cascorbi I. Safe and effective medicines for all: is personalized medicine the answer? Expert Rev Clin Pharmacol 2010; 3:627-37. [PMID: 22111745 DOI: 10.1586/ecp.10.36] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
An improvement in drug treatment and clinical outcome is one of the major challenges in clinical medicine. The development of evidence-based standards of care has led to a significant improvement, but, by definition, strictly standardized cohorts in clinical trials have to ignore individual differences. Personalized medicine is defined as the application of genomic and molecular data to better target the delivery of healthcare, facilitate the discovery and clinical testing of new products, and help determine a person's predisposition to a particular disease or condition. After the deciphering of the human genome, however, the high expectations in individualized medicine were not always fulfilled. However, personalized medicine has become indispensable in the treatment of malignant diseases and there is increasing evidence for its benefit in other areas. This article outlines the impact of pharmacogenetics and pharmacogenomics, especially with regard to personalized medicine, in major medical indications and reflects the obstacles and chances taken in current daily practice.
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Affiliation(s)
- Ingolf Cascorbi
- Institute for Experimental and Clinical Pharmacology, University Hospital Schleswig-Holstein, Arnold-Heller-Str. 3, Bldg 30, D-24105 Kiel, Germany.
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Standard warfarin dose in a patient with the CYP2C9*3/*3 genotype leads to hematuria. Clin Chim Acta 2010; 411:1375-7. [DOI: 10.1016/j.cca.2010.04.014] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2010] [Revised: 04/09/2010] [Accepted: 04/13/2010] [Indexed: 11/23/2022]
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Thornburg CD, Jones E, Bomgaars L, Gage BF. Pediatric warfarin practice and pharmacogenetic testing. Thromb Res 2010; 126:e144-6. [DOI: 10.1016/j.thromres.2009.12.022] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2009] [Revised: 11/23/2009] [Accepted: 12/30/2009] [Indexed: 11/28/2022]
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Squassina A, Manchia M, Manolopoulos VG, Artac M, Lappa-Manakou C, Karkabouna S, Mitropoulos K, Zompo MD, Patrinos GP. Realities and expectations of pharmacogenomics and personalized medicine: impact of translating genetic knowledge into clinical practice. Pharmacogenomics 2010; 11:1149-67. [DOI: 10.2217/pgs.10.97] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The implementation of genetic data for a better prediction of response to medications and adverse drug reactions is becoming a reality in some clinical fields. However, to be successful, personalized medicine should take advantage of an informational structured framework of genetic, phenotypic and environmental factors in order to provide the healthcare system with useful tools that can optimize the effectiveness of specific treatment. The impact of personalized medicine is potentially enormous, but the results that have so far been gathered are often difficult to translate into clinical practice. In this article we have summarized the most relevant applications of pharmacogenomics on diseases to which they have already been applied and fields in which they are currently emerging. The article provides an overview of the opportunities and shortcomings of the implementation of genetic information into personalized medicine and its full adoption in the clinic. In the second instance, it provides readers from different fields of expertise with an accessible interpretation to the barriers and opportunities in the use/adoption of pharmacogenomic testing between the different clinical areas.
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Affiliation(s)
| | - Mirko Manchia
- University of Cagliari, Cagliari, Italy
- Dalhousie University, Halifax, Nova Scotia, Canada
| | | | | | | | | | | | | | - George P Patrinos
- University of Patras, Department of Pharmacy, School of Health Sciences, University Campus, Rion, GR-265 04, Patras, Greece
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The long and winding road to warfarin pharmacogenetic testing. J Am Coll Cardiol 2010; 55:2813-5. [PMID: 20579536 DOI: 10.1016/j.jacc.2010.04.006] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/29/2010] [Revised: 04/01/2010] [Accepted: 04/06/2010] [Indexed: 11/21/2022]
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Lötsch J, Geisslinger G. A critical appraisal of human genotyping for pain therapy. Trends Pharmacol Sci 2010; 31:312-7. [DOI: 10.1016/j.tips.2010.04.002] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2009] [Revised: 04/07/2010] [Accepted: 04/08/2010] [Indexed: 01/08/2023]
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Manolopoulos VG, Ragia G, Tavridou A. Pharmacogenetics of coumarinic oral anticoagulants. Pharmacogenomics 2010; 11:493-6. [PMID: 20350128 DOI: 10.2217/pgs.10.31] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Coumarinic oral anticoagulants are life-saving drugs, but are also one of the leading causes of drug-induced major bleeding events. Moreover, there is substantial individual variation in response to coumarinic oral anticoagulants caused by several factors including variations in the CYP2C9 and VKORC1 genes. Several retrospective and a few small prospective clinical studies have shown that polymorphisms in CYP2C9 and VKORC1 genes together account for 35-50% of the variability in warfarin initiation and maintenance dose requirements. Large randomized clinical trials are currently underway to further solidify the safety, clinical utility and cost-effectiveness of pharmacogenetic-guided dosing algorithms for warfarin, acenocoumarol and phenprocoumon. By 2020, coumarinic oral anticoagulant pharmacogenetic testing will be part of routine clinical practice in anticoagulant therapy.
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Affiliation(s)
- Vangelis G Manolopoulos
- Laboratory of Pharmacology & Clinical Pharmacology, Medical School, Democritus University of Thrace, Dragana Campus, 68100 Alexandroupolis, Greece.
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Cascorbi I. The promises of personalized medicine. Eur J Clin Pharmacol 2010; 66:749-54. [PMID: 20563567 DOI: 10.1007/s00228-010-0858-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2010] [Accepted: 06/02/2010] [Indexed: 01/11/2023]
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Muszkat M, Bialer O, Blotnick S, Adar L, Xie HG, Ufer M, Cascorbi I, Caraco Y. Effects of folic acid supplementation on the pharmacokinetics and anticoagulant effect of warfarin: an open-label, prospective study of long-term administration in adults. Clin Ther 2010; 32:347-56. [PMID: 20206792 DOI: 10.1016/j.clinthera.2010.02.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/23/2009] [Indexed: 02/06/2023]
Abstract
BACKGROUND Folic acid supplementation in patients with folic acid deficiency has been associated with increased clearance of phenytoin to its cytochrome P450 (CYP) 2C9-mediated metabolite, 5-(4'-hydroxyphenyl)-5-phenylhydantoin. OBJECTIVE The aim of this study was to determine whether folic acid supplementation increases the dosage requirement of the CYP2C9 substrate warfarin, and the formation clearance of the CYP2C9-mediated product, (S)-7-hydroxywarfarin. METHODS Patients aged >or=18 years with folic acid deficiency who were receiving long-term treatment with a stable dosage of warfarin were studied prospectively, before and 30 to 60 days after the initiation of supplementation with folic acid. Warfarin dosage and international normalized ratio (INR) were documented, and the formation clearance of (S)- and (R)-7-hydroxywarfarin and the oral clearance of (S)- and (R)-warfarin were determined. RESULTS Twenty-four white patients (14 males; mean (SD) age, 55.0 [19.7] years; body mass index, 30.64 [6.8] kg/m(2)) were enrolled. Treatment with folic acid was associated with a significantly increased mean (SD) formation clearance of (S)-7-hydroxywarfarin (1.096 [0.816] vs 1.608 [1.302] mL/min; P = 0.048). Before folic acid supplementation, the mean (SD) warfarin dosage was 5.98 (2.12) mg/d, and the INR was 2.51 (0.55). During supplementation, the warfarin dosage was 6.17 (2.31) mg/d and the INR was 2.63 (0.65) (both, P = NS vs before supplementation). CONCLUSIONS Folic acid supplementation was associated with significantly increased formation clearance of (S)-7-hydroxywarfarin. Changes in warfarin dosage requirements and INR were nonsignificant.
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Affiliation(s)
- Mordechai Muszkat
- Division of Medicine, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
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