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The goals of the Association for Molecular Pathology Clinical Practice Committee's Pharmacogenomics (PGx) Working Group are to define the key attributes of pharmacogenetic alleles recommended for clinical testing and a minimum set of variants that should be included in clinical PGx genotyping assays. This document series provides recommendations for a minimum set of variant alleles (tier 1) and an extended list of variant alleles (tier 2) that will aid clinical laboratories when designing assays for PGx testing. The Association for Molecular Pathology PGx Working Group considered the functional impact of the variant alleles, allele frequencies in multiethnic populations, the availability of reference materials, and other technical considerations for PGx testing when developing these recommendations. The goal of this Working Group is to promote standardization of PGx testing across clinical laboratories. This document will focus on clinical DPYD PGx testing that may be applied to all dihydropyrimidine dehydrogenase-related medications. These recommendations are not to be interpreted as prescriptive but to provide a reference guide., Competing Interests: Disclosure Statement The University of North Carolina Medical Genetics Laboratory, RPRD Diagnostics, AccessDx Laboratory, and the Stanford Medicine Clinical Genomics Laboratory are fee-for-service clinical laboratories that offer clinical pharmacogenomic testing. V.M.P. is the director of Scientific Affairs for Agena Bioscience, is a member of the Pharmacogene Variation Consortium (PharmVar) Steering Committee and PharmVar CYP2C and CYP3A Gene Expert Panels, and is the Association for Molecular Pathology liaison to the National Academy of Medicine Roundtable on Genomics and Precision Health. L.H.C. is supported by NIH/National Human Genome Research Institute (NHGRI) grant U01 HG007269 and NIH/National Center for Advancing Translational Sciences grant UL1 TR001427 and serves on the Clinical Pharmacogenetics Implementation Consortium (CPIC) steering committee. A.G. is the director of PharmVar, a member of CPIC, and a member of the CPIC and Pharmacogenomics Clinical Annotation Tool Scientific Advisory Boards. H.H. is an employee of AccessDx Holdings and serves on the CPIC Scientific Advisory Board and on the PharmVar CYP2D6 Gene Expert Panel. Y.J. serves as the Vice Chair of the American College of Medical Genetics and Genomics (ACMG) Membership Committee. R.C.L. is a member of the PharmVar CYP2D6 Gene Expert Panel. A.M.M. is a member of the College of American Pathologists (CAP)/ACMG Biochemical and Molecular Genetics Committee and Pharmacogenetics Workgroup, the PharmVar CYP2D6 Gene Expert Panel, the ClinGen Pharmacogenomics (PGx) Working Group, and the ClinPGx Scientific Advisory Board. S.A.S. serves on the steering committees of CPIC and PharmVar and is a member of the PharmVar CYP2C Gene Expert Panel. A.J.T.'s efforts are supported in part by RPRD Diagnostics, an independent clinical laboratory offering pharmacogenetic testing services; she also serves on the PharmVar CYP1A2, CYP2D6, DPYD, and NUDT15 Gene Expert Panels. R.H.N.v.S. is a member of the Dutch Pharmacogenetics Working Group of the Royal Dutch Pharmacists Association, is a board member and past president of the European Society for Pharmacogenomics and Personalized Therapy, serves on the PharmVar CYP3A Gene Expert Panel, and is a member of the CPIC Scientific Advisory Board. M.W.-C. is supported by NIH/NHGRI/National Institute of Child Health and Human Development/National Institute on Drug Abuse grant U24 HG010615 and NIH/NHGRI grant U24 HG013077, is a co-investigator of CPIC, is co–principal investigator and director of the Pharmacogenomics Knowledgebase, and serves on the steering committee and multiple Gene Expert Panels for PharmVar. K.E.W. serves as the CAP liaison to the National Academy of Medicine Roundtable on Genomics and Precision Health. The remaining authors have declared no related conflicts of interest., (Copyright © 2024 Association for Molecular Pathology and American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.)

Methadone is a mu (μ) opioid receptor agonist used clinically in adults and children to manage opioid use disorder, neonatal abstinence syndrome, and acute and chronic pain. It is typically marketed as a racemic mixture of R- and S-enantiomers. R-methadone has 30-to 50-fold higher analgesic potency than S-methadone, and S-methadone has a greater adverse effect (prolongation) on the cardiac QTc interval. Methadone undergoes stereoselective metabolism. CYP2B6 is the primary enzyme responsible for catalyzing the metabolism of both enantiomers to the inactive metabolites, S- and R-2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (S- and R-EDDP). Genetic variation in the CYP2B6 gene has been investigated in the context of implications for methadone pharmacokinetics, dose, and clinical outcomes. Most CYP2B6 variants result in diminished or loss of CYP2B6 enzyme activity, which can lead to higher plasma methadone concentrations (affecting S- more than R-methadone). However, the data do not consistently indicate that CYP2B6-based metabolic variability has a clinically significant effect on methadone dose, efficacy, or QTc prolongation. Expert analysis of the published literature does not support a change from standard methadone prescribing based on CYP2B6 genotype (updates at www.cpicpgx.org)., (© 2024 The Author(s). Clinical Pharmacology & Therapeutics © 2024 American Society for Clinical Pharmacology and Therapeutics.)

The Pharmacogene Variation Consortium (PharmVar) provides nomenclature for the human CYP2A gene locus containing the highly polymorphic CYP2A6 gene. CYP2A6 plays a role in the metabolism of nicotine and various drugs. Thus, genetic variation can substantially contribute to the function of this enzyme and associated efficacy and safety. This GeneFocus provides an overview of the clinical significance of CYP2A6, including its genetic variation and function. We also highlight and discuss caveats in the identification and characterization of allelic variation of this complex pharmacogene, a prerequisite for accurate genotype determination and prediction of phenotype status., (© 2024 The Author(s). Clinical Pharmacology & Therapeutics published by Wiley Periodicals LLC on behalf of American Society for Clinical Pharmacology and Therapeutics.)

The Pharmacogene Variation Consortium (PharmVar) serves as a global repository providing star (*) allele nomenclature for the polymorphic human CYP4F2 gene. CYP4F2 genetic variation impacts the metabolism of vitamin K, which is associated with warfarin dose requirements, and the metabolism of drugs, such as imatinib or fingolimod, and certain endogenous compounds including vitamin E and eicosanoids. This GeneFocus provides a comprehensive overview and summary of CYP4F2 genetic variation including the characterization of 14 novel star alleles, CYP4F2*4 through *17. A description of how haplotype information cataloged by PharmVar is utilized by the Pharmacogenomics Knowledgebase (PharmGKB) and the Clinical Pharmacogenetics Implementation Consortium (CPIC) is also provided., (© 2024 The Author(s). Clinical Pharmacology & Therapeutics published by Wiley Periodicals LLC on behalf of American Society for Clinical Pharmacology and Therapeutics.)