Indiana Institute of Personalized Medicine Indiana University School of Medicine Division of Clinical Pharmacology

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Objectives  A case…  A fundamental change in the medical paradigm  A short primer on pharmacogenomics ◦ SNPs ◦ Metabolism and transport ◦ SNP nomenclature  Some pharmacogenomically important medications  Clinical application ◦ Back to the case… Originally created for IU Provider CME 9/2013 3

Case:  RF is a 58 year-old female with a past medical history of coronary artery disease, hypertension, and hypercholesterolemia who presents to her cardiologist with shortness of breath, and a sensation of a “racing heart”. Electrocardiogram confirms atrial fibrillation. Included in RF’s treatment plan is oral anticoagulation initiation with warfarin. ◦ RF agrees to genetic screening for potential variants that could affect her warfarin therapy  Results reveal that she has the heterozygous CYP2C9*2/*3 and the GA VKORC1 genotype Originally created for IU Provider CME 9/2013 4

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D I S E A S E Patient Outcome? MEDICATION Originally created for IU Provider CME 9/2013 6

 Patient outcomes… ◦ Mitigate or cure disease ◦ No effect ◦ Adverse drug event, difficult to predict  Sometimes serious Originally created for IU Provider CME 9/2013 7

 Pharmacogenomic Medical Paradigm… Patient Outcome -Mitigate or cure disease -No serious adverse drug events “Personalized Medicine” Pharmacogenetic test Originally created for IU Provider CME 9/2013 8

Historical milestones Hemolysis in World War II African-American soldiers treated with primaquine lead to identification of G6PD deficiency In the 1957, Kalow and Gunn discovered subjects homozygous for a gene encoding an atypical form of pseudocholinesterase had delayed recovery from succinylcholine 1959, Vogel et al. a common genetic variation in the hepatic enzyme N- acetyltransferase was found to cause marked differences in drug half-life and plasma concentration of isoniazid 1977, Eichelbaum et al. identified the CYP2D6 polymorphism 2001, Drucker et al. demonstrated remarkable response using imatinib for CML 2003, finished version of human genome sequence is completed June 13 th, 2013, US Supreme Court rules that human genes cannot be patented Originally created for IU Provider CME 9/2013 9

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 99.5% of the genome between any two individuals is identical  Mutations that occur in genomic DNA give rise to genetic variation ◦ When a mutation occurs in at least 1% of individuals in a population it is termed a “polymorphism” ◦ Most common polymorphism is the single nucleotide polymorphism or “SNP”  Occurs when there is a difference in a single nucleotide  Approximately 90% of all genetic variation is thought to derive from SNPs  2/3 rd of SNPs involve replacement of cytosine for thymine  ~10 million SNPs in the human genome, so far… ◦ Much of the research has focused on the characterization of the SNPs in human genes regulating drug disposition  Drug metabolizing enzymes  Intracellular transport of drugs Originally created for IU Provider CME 9/

 Drug metabolism ◦ Two basic metabolic reactions  Phase 1 metabolism:  Cytochrome P450 (CYP450) system  CYP3A, 2D6, 2C9, 2C19  Mixed-function oxidases produce more polar compounds  Phase 2 metabolism:  N-acetyltransferase, UDP-glucoruoronysltransferase (UGT), glutathione S-transferase  Conjugation reactions increase the molecular weight, increases bulkiness of compounds Originally created for IU Provider CME 9/

 Drug transporters are found in liver, kidney, intestines, brain and pancreas  Two major classes  Uptake  Facilitate translocation of drugs into cells  OAT (organic anion transporter)  SLCO1B1  OCT (organic cation transporter)  Efflux  Excrete drugs from within cells to extracellular space  P-gp (p-glycoprotein), MRP2, MRP3 Nature Reviews Drug Discovery 9, (March 2010) | doi: /nrd3028 Giacomini KM et al. Nature Rev Drug Discovery, 2010; 9: Originally created for IU Provider CME 9/

Drug metabolism and transport ◦ SNPs can change the protein of a CYP450 enzyme or transporter Leads to altered drug metabolism and/or transport Effects on drug disposition leading to unpredictable pharmacodynamics Drug response? Adverse drug event? Originally created for IU Provider CME 9/

 Nomenclature of SNPs ◦ Phase 1 enzymes: CYP2C9*2A ◦ Alleles are alternate versions of a gene ◦ *1 allele designation (CYP2C9*1) most commonly refers to the “wild type” or “normal” enzyme ◦ *2 or greater denote polymorphic alleles and are typically numbered in order of discovery-validation  Homozygous designation: CYP2C9*1/*1 (two copies of wild-type allele)  Heterozygous designation: CYP2C9*1/*2 (one copy of wild-type and one copy of reduced function allele) Superfamily Family Individual Member Subfamily Suballele Allele Originally created for IU Provider CME 9/

Nomenclature of SNPs ◦ Phase 2 enzymes and transporters  Utilizes similar nomenclature  UGT1A1*1/*1 (homozygous for wild-type)  SLCO1B1*1/*5 (heterozygous, contains one functional and one reduced function allele, “C” allele) ◦ Still other nomenclatures…  Named by haplotype  VKORC1, “haplotype A”, (G1639A)  GG, homozygous, (wild-type), normal levels of VKORC1  GA, heterozygous, lower level of VKORC1  AA, homozygous, lowest levels of VKORC1  Named by allele  SLCO1B1*5  “C” high myopathy risk allele, “T” other, low myopathy risk alleles  TT, homozygous, (low myopathy risk)  CT, heterozygous, (moderate myopathy risk)  CC, homozygous, (high myopathy risk)  Human Leukocyte Antigen (HLA)  HLA-B*5701 Originally created for IU Provider CME 9/

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Clopidogrel ◦ Pro-drug, requires CYP2C19 metabolism to become active ◦ CYP2C19 SNPs have been identified leading to different metabolism phenotypes  CYP2C19* 1 (wild-type), normal functioning enzyme  CYP2C19*17, ultra-rapid metabolizer  CYP19*2, CYP19*3, CYP2C19*4 have little or no functioning enzyme  24% Caucasian, 33% African-Americans, 50% of Asians have at least one loss-of-function allele  In 227 cardiac patients, Shuldiner et al. found that 21% of clopidogrel subjects with CYP2C19 LOF SNPs reached study endpoint (death, non-fatal MI, urgent revascularization) compared with 10% without the LOF SNPs Shuldiner AR et al, JAMA, 2009; 302 (8): Originally created for IU Provider CME 9/

Warfarin ◦ Consists of two isomers, S- and R-warfarin  S-warfarin is more potent and metabolized by CYP2C9  R-warfarin is metabolized by CYP1A1, 1A2 and 3A4  Pharmacologic target is VKORC1 ◦ Important SNPs  CYP2C9*1 (wild type): extensive metabolizers  CYP2C9*2 and *3: poor metabolizers  Heterozygous CYP2C9*1/*2 or *3: 20-40% lower clearance  Homozygous CYP2C9*2/*2: 50% lower clearance  Homozygous CYP2C9*3/*3: 85% lower clearance  CYP2C9 SNPs account for ~10-12% of the interindividual variability  CYP2C9*2: 16% of Caucasians, 1% of Asians and African–Americans  CYP2C9*3: 7% of Caucasians, 2% of Asians and African-Americans Originally created for IU Provider CME 9/

Warfarin ◦ Pharmacologic target of warfarin is also polymorphic  Vitamin K 2,3-epoxide reductase (VKORC1), inhibitory target of warfarin  VKORC1 GG, wild-type  VKORC1 GA, need ~25% lower doses  VKORC1 AA, need ~50% lower doses  VKORC1 SNPs account for ~25% of the interindividual variability  Haplotype A: African-Americans 15%, Caucasians 42%, Asians 90% ◦ CYP2C9 and VKORC1 variants have been estimated to explain 30-35% of the variability in warfarin dose requirements Originally created for IU Provider CME 9/

Warfarin ◦ Recent study by Anderson et al. compared two groups initiated on warfarin therapy  PG-guided: CYP2C9 and VKORC1 genotype incorporated into a warfarin dosing algorithm, n=504  Parallel controls: Standard of care, n=1,866 ◦ Investigators found significantly less INRs out-of- range (OOR) and more time in therapeutic range (TTR) during the critical 1 to 3 months of warfarin therapy in the PG-guided compared to control  PG-guided group also had significantly lower numbers of serious adverse events (thromboembolism, hemorrhage, death) ◦ Several large trials are underway to investigate this further  Genetics Informatics Trial of Warfarin to Prevent DVT (GIFT)  Clarification of Optimal Anticoagulation Through Genetics (COAG)  European Pharmacogenetics of Anticoagulant Therapy- Warfarin (EU-PACT) Anderson J L et al. Circulation 2012;125: Percentage of OOR INRs and % TTR for PG- guided dosing algorithms and parallel (standard dosing) controls. Originally created for IU Provider CME 9/

Simvastatin ◦ Drug transporters also have SNPs ◦ OATP1B1 is a transporter for entry of simvastatin into the hepatocyte for metabolism  SLCO1B1 is the gene that encodes this transporter ◦ A genetic variant of SLCO1B1 (C allele) was found to be associated with an increased risk of statin-induced myopathy in a study of over 12,000 subjects taking simvastatin SEARCH Collaborative Group, NEJM 2008;359: Originally created for IU Provider CME 9/2013

Tamoxifen ◦ Pro-drug metabolized by CYP2D6 to active endoxifen  CYP2D6*1, CYP2D6*2 (normal or “extensive” metabolizers)  Poor metabolizers (PM) CYP2D6*3, *4, *5, *6  Intermediate metabolizers (heterozygotes)  One normal and one PM allele (CYP2D6*1/*3)  Ultra-rapid metabolizers  3 or more copies of normal alleles due to duplication  CYP2D6*1/*2/*2  PMs are found in 7-14% of Caucasians, 14.5% of African- Americans ◦ In a study of early stage breast cancer subjects taking tamoxifen, Schroth et al. found that the presence of 2 functional CYP2D6 alleles was associated with better clinical outcomes than those subjects with non-functional or reduced- function CYP2D6 alleles 23 Schroth W et al, JAMA, 2009; 302(13): Originally created for IU Provider CME 9/

Abacavir ◦ Associated with a non- specific “hypersensitivity reaction” in patients with the HLA-B*5701 allele  Fever, rash, constitutional symptoms, GI and respiratory symptoms that worsen with continued dosing  Symptoms abate when abacavir is discontinued  In US, HLA-B*5701 is found in 8% of Caucasians, 2.5% of African-Americans and ~1% of Asians 24 Originally created for IU Provider CME 9/2013

 Prior examples are only a subset of the medications with pharmaco-genomic disposition issues  A 2011 list of the top 200 prescribed medications by total prescriptions included 17 with pharmacogenomic information in their FDA package inserts ◦ Includes the 5 th and 7 th most commonly prescribed medications ◦ In 2011, 362 million prescriptions were filled for these 17 medications ◦ Numbers are only expected to increase as pharmacogenomics and personalized medicine grows Originally created for IU Provider CME 9/

Interesting, but so what? How do I utilize this genetic information for the patient in my clinic? 26

Clinical Pharmacogenetics Implementation Consortium (CPIC) Purpose of CPIC is to “translate genetic information into clinical actions and to make recommendations for actionable pharmacogenetic variants” Group of clinical pharmacologists, clinicians and scientists that review all current literature and develop recommendations and algorithms to guide drug dosing based on pharmacogenotypes CPIC prioritizes gene-drug pairs based on community input and sponsored surveys of the CPIC members, American Society of Clinical Pharmacology and Therapeutics (ASCPT) and the public CPIC is a frequent contributor to the FDA and endorsed by the AMA, ASHP CPIC has evaluated 14 drugs so far with more to follow  Abacavir, allopurinol, azathioprine, capecitabine, carbamazepine, clopidogrel, codeine, irinotecan, mercaptopurine, phenytoin, simvastatin, TCAs, thioguanine, warfarin Originally created for IU Provider CME 9/

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Case:  RF is a 58 year-old female with a past medical history of coronary artery disease, hypertension, and hypercholesterolemia who presents to her cardiologist with shortness of breath, and a sensation of a “racing heart”. Electrocardiogram confirms atrial fibrillation. Included in RF’s treatment plan is oral anticoagulation initiation with warfarin. ◦ RF agrees to genetic screening for potential variants that could affect her warfarin therapy  Results reveal that she has the heterozygous CYP2C9*2/*3 and the GA VKORC1 genotype Originally created for IU Provider CME 9/

CPIC guideline for warfarin: Recommended daily warfarin doses (mg/day) to achieve a therapeutic INR based onCYP2C9 and VKORC1 genotype using the warfarin product insert approved by the US Food and Drug Administration Reproduced from updated warfarin (Coumadin) product label. VKORC1 (1639G>A) CYP2C9*1/*1 (mg) CYP2C9*1/*2 (mg) CYP2C9*1/*3 (mg) CYP2C9*2/*2 (mg) CYP2C9*2/*3 (mg) CYP2C9*3/*3 (mg) GG GA AA Clin Pharmacol Ther, 2011, 90: Originally created for IU Provider CME 9/

Conclusions  Pharmacogenomic medicine is a powerful tool to inform drug selection and clinical decision- making ◦ Has demonstrated potential to improve efficacy and safety of medications  As more clinical data emerges and genotyping costs fall, there will be increasing utilization and presence in clinical medicine "Here's my sequence...” New Yorker magazine Originally created for IU Provider CME 9/