Browsing by Subject "CYP2D6"

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    Clinical pharmacogenetics implementation consortium guideline (CPIC) for CYP2D6 and CYP2C19 genotypes and dosing of tricyclic antidepressants: 2016 update
    (Wiley, 2017-07) Hicks, J. Kevin; Sangkuhl, Katrin; Swen, Jesse J.; Ellingrod, Vicki L.; Müller, Daniel J.; Shimoda, Kazutaka; Bishop, Jeffrey R.; Kharasch, Evan D.; Skaar, Todd C.; Gaedigk, Andrea; Dunnenberger, Henry M.; Klein, Teri E.; Caudle, Kelly E.; Stingl, Julia C.; Medicine, School of Medicine
    CYP2D6 and CYP2C19 polymorphisms affect the exposure, efficacy and safety of tricyclic antidepressants (TCAs), with some drugs being affected by CYP2D6 only (e.g., nortriptyline and desipramine) and others by both polymorphic enzymes (e.g., amitriptyline, clomipramine, doxepin, imipramine, and trimipramine). Evidence is presented for CYP2D6 and CYP2C19 genotype-directed dosing of TCAs. This document is an update to the 2012 Clinical Pharmacogenetics Implementation Consortium (CPIC) guideline for CYP2D6 and CYP2C19 Genotypes and Dosing of Tricyclic Antidepressants.
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    Composite Functional Genetic and Comedication CYP2D6 Activity Score in Predicting Tamoxifen Drug Exposure Among Breast Cancer Patients
    (Wiley, 2010-04) Borges, Silvana; Desta, Zeruesenay; Jin, Yan; Faouzi, Azzouz; Robarge, Jason D.; Philip, Santosh; Nguyen, Anne; Stearns, Vered; Hayes, Daniel; Rae, James M.; Skaar, Todd C.; Flockhart, David A.; Li, Lang
    Accurate assessment of CYP2D6 phenotypes from genotype is inadequate in patients taking CYP2D6 substrate together with CYP2D6 inhibitors. A novel CYP2D6 scoring system is proposed that incorporates the impact of concomitant medications with the genotype in calculating the CYP2D6 activity score. Training (n = 159) and validation (n = 81) data sets were obtained from a prospective cohort tamoxifen pharmacogenetics registry. Two inhibitor factors were defined: 1 genotype independent and 1 genotype based. Three CYP2D6 gene scoring systems, and their combination with the inhibitor factors, were compared. These 3 scores were based on Zineh, Zanger, and Gaedigk's approaches. Endoxifen/NDM-Tam plasma ratio was used as the phenotype. The overall performance of the 3 gene scoring systems without consideration of CYP2D6-inhibiting medications in predicting CYP2D6 phenotype was poor in both the training set (R(2) = 0.24, 0.22, and 0.18) and the validation set (R(2) = 0.30, 0.24, and 0.15). Once the CYP2D6 genotype-independent inhibitor factor was integrated into the score calculation, the R(2) values in the training and validation data sets were nearly twice as high as the genotype-only scoring model: (0.44, 0.43, 0.38) and (0.53, 0.50, 0.41), respectively. The integration of the inhibitory effect of concomitant medications with the CYP2D6 genotype into the composite CYP2D6 activity score doubled the ability to predict the CYP2D6 phenotype. However, endoxifen phenotypes still varied substantially, even with incorporation of CYD2D6 genotype and inhibiting factors, suggesting that other, as yet unidentified factors must be involved in tamoxifen activation.
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    CYP2D6 Genotype is Not Associated with Survival in Breast Cancer Patients Treated with Tamoxifen: Results from a Population-based Study
    (SpringerLink, 2017-11) Hertz, D.L.; Kidwell, K.M.; Hilsenbeck, S.G.; Oesterreich, S.; Philips, S.; Chenault, C.; Hartmaier, R.J.; Skaar, Todd C.; Sikora, M.J.; Rae, J.M.; Medicine, School of Medicine
    Purpose: A number of studies have tested the hypothesis that breast cancer patients with low-activity CYP2D6 genotypes achieve inferior benefit from tamoxifen treatment, putatively due to lack of metabolic activation to endoxifen. Studies have provided conflicting data, and meta-analyses suggest a small but significant increase in cancer recurrence, necessitating additional studies to allow for accurate effect assessment. We conducted a retrospective pharmacogenomic analysis of a prospectively collected community-based cohort of patients with estrogen receptor-positive breast cancer to test for associations between low-activity CYP2D6 genotype and disease outcome in 500 patients treated with adjuvant tamoxifen monotherapy and 500 who did not receive any systemic adjuvant therapy. Methods: Tumor-derived DNA was genotyped for common, functionally consequential CYP2D6 polymorphisms (*2, *3, *4, *6, *10, *41, and copy number variants) and assigned a CYP2D6 activity score (AS) ranging from none (0) to full (2). Patients with poor metabolizer (AS = 0) phenotype were compared to patients with AS > 0 and in secondary analyses AS was analyzed quantitatively. Clinical outcome of interest was recurrence free survival (RFS) and analyses using long-rank test were adjusted for relevant clinical covariates (nodal status, tumor size, etc.). Results: CYP2D6 AS was not associated with RFS in tamoxifen treated patients in univariate analyses (p > 0.2). In adjusted analyses, increasing AS was associated with inferior RFS (Hazard ratio 1.43, 95% confidence interval 1.00-2.04, p = 0.05). In patients that did not receive tamoxifen treatment, increasing CYP2D6 AS, and AS > 0, were associated with superior RFS (each p = 0.0015). Conclusions: This population-based study does not support the hypothesis that patients with diminished CYP2D6 activity achieve inferior tamoxifen benefit. These contradictory findings suggest that the association between CYP2D6 genotype and tamoxifen treatment efficacy is null or near null, and unlikely to be useful in clinical practice.
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    Drug–gene and drug–drug interactions associated with tramadol and codeine therapy in the INGENIOUS trial
    (Future Medicine, 2019-04) Fulton, Cathy R.; Zang, Yong; Desta, Zeruesenay; Rosenman, Marc B.; Holmes, Ann M.; Decker, Brian S.; Zhang, Yifei; Callaghan, John T.; Pratt, Victoria M.; Levy, Kenneth D.; Gufford, Brandon T.; Dexter, Paul R.; Skaar, Todd C.; Eadon, Michael T.; Medicine, School of Medicine
    Background: Tramadol and codeine are metabolized by CYP2D6 and are subject to drug-gene and drug-drug interactions. Methods: This interim analysis examined prescribing behavior and efficacy in 102 individuals prescribed tramadol or codeine while receiving pharmaco-genotyping as part of the INGENIOUS trial (NCT02297126). Results: Within 60 days of receiving tramadol or codeine, clinicians more frequently prescribed an alternative opioid in ultrarapid and poor metabolizers (odds ratio: 19.0; 95% CI: 2.8-160.4) as compared with normal or indeterminate metabolizers (p = 0.01). After adjusting the CYP2D6 activity score for drug-drug interactions, uncontrolled pain was reported more frequently in individuals with reduced CYP2D6 activity (odds ratio: 0.50; 95% CI: 0.25-0.94). Conclusion: Phenoconversion for drug-drug and drug-gene interactions is an important consideration in pharmacogenomic implementation; drug-drug interactions may obscure the potential benefits of genotyping.
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    Multi-site investigation of strategies for the clinical implementation of CYP2D6 genotyping to guide drug prescribing
    (Springer Nature, 2019-10) Cavallari, Larisa H.; Van Driest, Sara L.; Prows, Cynthia A.; Bishop, Jeffrey R.; Limdi, Nita A.; Pratt, Victoria M.; Ramsey, Laura B.; Smith, D. Max; Tuteja, Sony; Duong, Benjamin Q.; Hicks, J. Kevin; Lee, James C.; Obeng, Aniwaa Owusu; Beitelshees, Amber L.; Bell, Gillian C.; Blake, Kathryn; Crona, Daniel J.; Dressler, Lynn; Gregg, Ryan A.; Hines, Lindsay J.; Scott, Stuart A.; Shelton, Richard C.; Weitzel, Kristin Wiisanen; Johnson, Julie A.; Peterson, Josh F.; Empey, Philip E.; Skaar, Todd C.; Medical and Molecular Genetics, School of Medicine
    PURPOSE: A number of institutions have clinically implemented CYP2D6 genotyping to guide drug prescribing. We compared implementation strategies of early adopters of CYP2D6 testing, barriers faced by both early adopters and institutions in the process of implementing CYP2D6 testing, and approaches taken to overcome these barriers. METHODS: We surveyed eight early adopters of CYP2D6 genotyping and eight institutions in the process of adoption. Data were collected on testing approaches, return of results procedures, applications of genotype results, challenges faced, and lessons learned. RESULTS: Among early adopters, CYP2D6 testing was most commonly ordered to assist with opioid and antidepressant prescribing. Key differences among programs included test ordering and genotyping approaches, result reporting, and clinical decision support. However, all sites tested for copy-number variation and nine common variants, and reported results in the medical record. Most sites provided automatic consultation and had designated personnel to assist with genotype-informed therapy recommendations. Primary challenges were related to stakeholder support, CYP2D6 gene complexity, phenotype assignment, and sustainability. CONCLUSION: There are specific challenges unique to CYP2D6 testing given the complexity of the gene and its relevance to multiple medications. Consensus lessons learned may guide those interested in pursuing similar clinical pharmacogenetic programs.