Pharmacogenomics: Genetic Factors Influencing Drug Response Angela S. Stewart, Pharm.D., BCPS Clinical Associate Professor Assistant Dean – Yakima Extension College of Pharmacy Washington State University

JB is a 63 year old Caucasian gentleman with newly diagnosed atrial fibrillation who needs to be started on warfarin therapy for stroke prevention. He is 5’10”, 187 #, SrCr 1.3, H/H 13.9/42. He has DMII, hyperlipidemia, and HTN controlled on metformin, lisinopril, and rosuvastatin. He is a non-smoker and social drinker. What initial warfarin dose would you select? Patient Case

JB is a 63 year old Caucasian gentleman with newly diagnosed atrial fibrillation who needs to be started on warfarin therapy for stroke prevention. He is 5’10”, 187 #, SrCr 1.3, H/H 13.9/42. He has DMII, hyperlipidemia, and HTN controlled on metformin, lisinopril, and rosuvastatin. He is a non-smoker and social drinker. What initial warfarin dose would you select? What follow-up and monitoring will you order? Patient Case

JB is a 63 year old Caucasian gentleman with newly diagnosed atrial fibrillation who needs to be started on warfarin therapy for stroke prevention. He is 5’10”, 187 #, SrCr 1.3, H/H 13.9/42. He has DMII, hyperlipidemia, and HTN controlled on metformin, lisinopril, and rosuvastatin. He is a non-smoker and social drinker. The patient returns 3 days later and is complaining of bleeding gums, increased bruising, and his INR is 6.5. He is instructed to hold warfarin and return to clinic in 2 days for another INR check. Can genetics help to explain this patients sensitivity to warfarin? Patient Case

State a rationale for advancing a personalized medicine approach in your practice Define pharmacogenomics Review basics of pharmacokinetics and genetics as they relate to pharmacogenomics List common examples of genetic polymorphisms that may alter response to medications Identify tools and resources useful in applying genetic information to patient care Apply genetic testing information in medical decision making for common clinical scenarios Recognize barriers to incorporation of pharmacogenomics information into practice Objectives:

Outline Genomics Definitions Genetics Review Genetic Variation & Pharmacokinetics vs Pharmacodynamics Tools and Resources Clinically Relevant Examples Outline

Personalized Medicine AKA: genomic medicine, precision medicine Wikipedia Definition: medical care that separates patients into different groups – with medical decisions, practices, interventions, and/or products being tailored to the individual patient based on their predicted response or risk of disease. PERSONALIZED MEDICINE CAN: • Shift the emphasis in medicine from reaction to prevention • Direct the selection of optimal therapy and reduce trial-and-error prescribing • Help avoid adverse drug reactions • Increase patient adherence to treatment • Improve quality of life • Reveal additional or alternative uses for medicines and drug candidates • Help control the overall cost of health care Personalized Medicine

Clin Infect Dis November 15, 2005 vol. 41 no. Supplement 7 S449-S452

The study of how genes affect a person's response to drugs The study of how genes affect a person's response to drugs. This relatively new field combines pharmacology (the science of drugs) and genomics (the study of genes and their functions) to develop effective, safe medications and doses that will be tailored to a person's genetic makeup. Pharmacogenetics - Study of variability in drug response determined by single genes. Pharmacogenomics - Study of variability in drug response determined by multiple genes within the genome. Pharmaco- Genomics

DNA Double Helix

Transcription and Translation http://www.nobelprize.org/educational/medicine/dna/index.html

Gene Expression https://www.ncbi.nlm.nih.gov/probe/docs/applexpression/

Mendellian Inheritance http://biology.about.com/od/geneticsglossary/g/alleles.htm

Common Genetic Variation Single Nucleotide Polymorphisms (SNPs) Copy Number Variants (CNV) Insertions/Deletions (Indels) Variable Number Tandem Repeats (VNTR) Common Genetic Variation

SNP http://genomicsinitiative.com/index.html

Genotype & Phenotype http://dx.doi.org/10.1016/j.pharmthera.2012.12.007

Kinetics & Dynamics

Absorption Distribution Excretion Genetic Variability in Drug Transporter Proteins ABCB1 gene – p-Glycoprotein, multi-drug resistance 1 ABCG2 – breast cancer resistance protein OATP – organic anion transporter proteins Absorption Distribution Excretion

Drug Metabolism Phase I Functionalization Reactions Oxidation Reduction Cytochrome P450 Enzyme Systems Phase II Conjugation Reactions Glucuronidation Sulfation Others Drug Metabolism

Variability in CYP enzymes http://dx.doi.org/10.1016/j.pharmthera.2012.12.007

Variabililty in Phase II Enzymes N-acetyltransferase (NAT2) Cancer risk Metabolism of isoniazide, caffeine, others UDP-glucuronosyltransferase (UGT1A1*28) Gilbert’s Syndrome Metabolism of irinotecan Thiopurine methyltranferase (TPMT) Metabolism of 6-mercaptopurine and azathioprine Variabililty in Phase II Enzymes

Clinically Relevant Examples Disease Drug Example DME & variant alleles Depression Tricyclic Antidepressants CYP2D6*3,*4,*6 CYP2C19*2, *3, *17 Thromboembolic Disorders Warfarin Clopidogrel CYP2C9*2, *3 GI Diseases Proton Pump Inhibitors CYP2C19*2, *3 Pain Management Codeine CYP2D6*4, *5, *6 Malignant Diseases Thiopurines Irinotecan TPMT *2, *3A, *3C UGT1A1 *28, *6, *27 Clinically Relevant Examples

Pharmaco-dynamics Genetic Variability Affecting Drug Targets VKOR – Vitamin K Epoxide Reductase ACE – Angiotensin I Converting Enzyme ADRB2 – Beta 2 Receptor Pharmaco-dynamics

JB is a 63 year old Caucasian gentleman with newly diagnosed atrial fibrillation who needs to be started on warfarin therapy for stroke prevention. He is 5’10”, 187 #, SrCr 1.3, H/H 13.9/42. He has DMII, hyperlipidemia, and HTN controlled on metformin, lisinopril, and rosuvastatin. He is a non-smoker and social drinker. The patient returns 3 days later and is complaining of bleeding gums, increased bruising, and his INR is 6.5. He is instructed to hold warfarin and return to clinic in 2 days for another INR check. Which available genetifc test(s) may explain this patient’s sensitivity to warfarin? Patient Case

Metabolism and therapeutic action of warfarin. Qiang Ma, and Anthony Y. H. Lu Pharmacol Rev 2011;63:437-459 U.S. Government work not protected by U.S. copyright

Warfarin Gene/Allele of Interest Functional Effect CYP2C9 *2 or *3 VKORC1 (-1639G>A) Functional Effect Reduced metabolism of S-warfarin Reduced expression of VKOR protein Population Prevalence CYP2C9*2 an *3 = 5% each VKORC1 variant 36%, 88% East Asians Clinical Significance Together account for approximately 40% of variability in response Contribute to increased warfarin sensitivity Warfarin

JB is a 63 year old Caucasian gentleman with newly diagnosed atrial fibrillation who needs to be started on warfarin therapy for stroke prevention. He is 5’10”, 187 #, SrCr 1.3, H/H 13.9/42. He has DMII, hyperlipidemia, and HTN controlled on metformin, lisinopril, and rosuvastatin. He is a non-smoker and social drinker. The results of JB’s genomic testing reveal that he has the VKORC1 AA genotype and is an CYP2C9 *1/*2 genotype (intermediate metabolizer phenotype). How will you use this information to personalize his drug therapy? Patient Case

Warfarin Dosing with Genotyping Warfarin Dose (mg/day) Coumadin package insert

Genomic Dosing for Warfarin Package Insert – genotype information, when available, can assist in selecting the starting dose CPIC – use warfarin dosing algorithm that incorporates genetic information Conflicting results in clinical trials N Engl J Med 2013; 369:2283-2293 N Engl J Med 2013; 369:2294-2303 Genomic Dosing for Warfarin

Clinically Useful Websites CPIC – Clinical Pharmacogenetics Implementation Consortium Clinical guidelines for use of genomic testing/dosing https://www.pharmgkb.org/view/dosing- guidelines.do?source=CPIC Food and Drug Administration (FDA) Drugs with genomic information in package insert http://www.fda.gov/Drugs/ScienceResearch/ResearchAreas/Ph armacogenetics/default.htm WarfarinDosing.org Free website and genomic dosing calculator http://www.warfarindosing.org/Source/Home.aspx National Human Genome Research Institute NIH Institute dedicated to advancing application ofgenomics research https://www.genome.gov/ Genetics Home Reference Consumer-friendly information on the effects of genetic variation on human health. https://ghr.nlm.nih.gov/ Clinically Useful Websites

Commercially Available Tests Genetic Testing Registry (GTR) Central location for information on available tests https://www.ncbi.nlm.nih.gov/gtr/ Examples from GTR Genelex and YouScript Decision Support http://genelex.com/ 61 conditions/phenotypes in 29 tests MD Labs and RxIGHT Pharmacogenetics www.RxIGHT.com 79 conditions/phenotypes in one test OneOME www.oneome.com 94 conditions/phenotypes in one test Direct to Consumer Testing Information International Society of Genetic Geneology Wiki http://isogg.org/wiki/List_of_personal_genomics_c ompanies Commercially Available Tests

Barriers to Full Implementation Practical issues involved in clinical implementation of pharmacogenomic testing in healthcare system. Issue Challenge Test performance Reasonable turnaround time for delivery of test result Interpretation of result Not a straightforward normal versus abnormal interpretation Education of clinicians is crucial to proper use Education of health professionals Variable time and content devoted to educating future clinicians within health professional schools Overwhelming information for most current practicing clinicians Cost reimbursement by payers Almost exclusively based on proof of cost-effectiveness Acceptance by clinicians Potential additional workload Potential legal liability Health disparity concern for patient Acceptance by patients Privacy and discrimination concern Health disparity concern Ownership of genetic information Barriers to Full Implementation http://dx.doi.org/10.1155/2013/641089

Clopidogrel CYP2C19 Prevalence Effect Recommendation Ultra-rapid metabolizer *1/*17 *17/*17 5-30% Increased platelet inhibition Monitor for increased bleeding Extensive metabolizer *1/*1 35-50% Normal platelet inhibition Normal dosing Intermediate metabolizer *1/*2 *1/*3 *2/*17 18-45% Reduced platelet inhibition, increased risk for CV events Consider alternative anti-platelet agents Poor metabolizer *2/*2 *2/*3 *3/*3 2-15% Significantly reduced platelet inhibition, increased risk for CV events Use alternative anti-platelet agents Clopidogrel

Phenotype CYP2D6 Prevalence CYP2C19 Poor metabolizer *3/*4 *4/*4 *5/*5 1-10% *2/*2 *2/*3 *3/*3 2-15% Normal Metabolizer *1/*1 72-88% 34-50% Ultra-rapid metabolizer *1/*1xN 1-20% *17/*17 2-5% Amitriptylline PM’s – greatly reduced metabolism, increased risk for ADR’s, consider alternative agents or at least 50% dose reduction URM’s – increased metabolism to less active compounds, lower plasma concentrations, increased risk for treatment failure, consider alternative agents

Codeine Metabolism Phenotype Allele Prevalence Effect Recommendation Ultra-rapid *1/*1N *1/*2N 1-2% Increased formation of morphine Avoid use due to toxicity Extensive *1/*1 *1/*2 *2/*2 77-92% Normal formation of morphine Normal dosing Intermediate *4/*10 *5/*41 2-11% Reduced formation of morphine Normal dosing, monitor for response Poor *4/*4 *4/*5 *5/*5 5-10% Greatly reduced formation of morphine Avoid use due to lack of efficacy Codeine

Personalized Medicine and Pharmacogenomcis may improve patient outcomes There are a wide variety of genetic polymorphisms that may alter an individuals response to medications Genetic testing is becoming more widely available and affordable Guidelines exist to help in utilizing genetic information to optimize drug therapy Barriers still exist to full incorporation of pharmacogenomic information into routine medical decision making Conclusions