Genetics in Dentistry Pharmacogenetics Pharmacogenetics & Pharmacogenomics • Pharmacogenetics: The role of genetics in drug responses. oF. Vogel. 1959 • Pharmacogenomics: The science that allows us to predict a response to drugs based on an individuals genetic makeup. oFelix Frueh, Associate Director of Genomics, FDA Courtesy Felix W. Frueh Pharmacogenetics & Pharmacogenomics • Pharmacogenetics: study of individual gene-drug interactions, usually one or two genes that have dominant effect on a drug response (SIMPLE relationship) • Pharmacogenomics: study of genomic influence on drug response, often using highthroughput data (sequencing, SNP chip, expression, proteomics COMPLEX interactions) 4 Relation to genes • Almost every pathway of drug metabolism, its transport or activation is influenced by genetic variability. • Clinical variability in the response • The risk of side effects • Genotype specific dosage • Polymorphic targets drug 5 GENETIC POLYMORPHISMS Pharmacokinetic Pharmacodynamic •Transporters •Plasma protein binding •Metabolism •Receptors •Ion channels •Enzymes •Immune molecules 6 From: Evans WE, Relling MV. Pharmacogenomics: Translating functional genomics into rational therapeutics. Science 286:487-491, 1999. Genetic polymorphisms in drug metabolizing enzymes 10 questions in polygenic disorders How important are genetic influences in the most common forms of multigene diseases? What is the influence of the environment on the onset of the disease? Which are the most promising approaches to the determination of genetic factors leading to the onset of disease? Which genes have already been selected as candidate genes? Which paths contribute to genetic susceptibility for the disease? How many genes are involved in susceptibility to disease? Are the most common forms of polygenic diseases associated with frequent or rare genetic variability in the population? (hypothesis frequent variations / frequent genetic disease vs. heterogeneous model) Why alleles that are associated with the disease were not eliminated from the population? The importance for the disease-environment interaction genes and genes-genes? What are the implications for pharmacogenetics? 7 Candidate genes - Association • with the intermediate phenotype • with clinical manifestation of disease • with clinical severity of disease • with responsiveness to treatment of disease 8 Pharmacogenetics: A Case Study Pharmacogenetics: A Case Study Clinically relevant genetic polymorphisms in relation to side effects of drugs 12 Clinically relevant genetic polymorphisms in relation to the effectiveness of drugs 13 14 Glucose-6-phosphate dehydrogenase activity Effects >100 million worldwide R- NH2 CYP MPO PGH Synthase R-NOH ERYTHROCYTE R-NOH O2 HgbFe+2 R-NO HgbFe+3 Reactive Oxygen NADH NAD+ MetHgb Reductase NADPH or GSH(?) NADP+ or GSSG(?)HMP Shunt G-6-PD Dependent SOD Catalase GSH Peroxidase Detoxification Splenic Sequestration Hemolytic Anemia GSH Semi-mercaptal sulfinamide R- NH2 15 Drugs and Chemicals Unequivocally Demonstrated to Precipitate Hemolytic Anemia in Subjects with G6PD Deficiency Acetanilide Nitrofurantoin Primaquine Methylene Blue Sulfacetamide Nalidixic Acid Naphthalene Sulfanilamide Sulfapyridine Sulfamethoxazole 16 INCIDENCE OF G6PD DEFICIENCY IN DIFFERENT ETHNIC POPULATIONS Ethnic Group Incidence(%) Asiatics Chinese 2 Filipinos 13 Indians-Parsees 16 Javanese 13 Micronesians <1 Iranians 8 Greeks 0.7-3 Persia 15 Cytochrome Oxidase P450 Enzymes • 57 Different active genes • 17 Different families • CYP1, CYP2 and CYP3 are primarily involved in drug metabolism. • CYP2A6, CYP2B6, CYP2C9 ,CYP2C19, CYP2D6, CYP2E1 and CYP3A4 are responsible for metabolizing most clinically important drugs © 2006 American Medical Association. All rights reserved Polymorphic Cytochrome P-450s Effect of Metabolic Rate on Drug Dosage © 2006 American Medical Association. All rights reserved 20 Debrisoquine phenotype in subjects with different CYP2D6 genotypes Genotype # of Subjects Metabolic Ratio CYP2D6wt/(CYP2D6L)2 9 0.33 CYP2D6wt/CYP2D6wt 12 1.50 CYP2D6wt/CYP2D6(A or B) 9 2.14 CYP2D6B/CYP2D6B 6 48.84 (CYP2D6L)2 - gene duplication; CYP2D6A - single base deletion CYP2D6B - multiple point mutations Data from: Agundez JG et al. Clin Pharmacol Ther 57:265, 1995. Codeine and Cytochrome P450 CYP2D6 • Codeine is a commonly used opioid • Codeine is a prodrug • It must be metabolized into morphine for activity • Cytochrome P450 allele CYP2D6 is the metabolizing enzyme in the liver • 7% of Caucasians are missing one copy of the Cytochrome P450 CYP2D6 gene • codeine does not work effectively in these individuals 22 From: Dalen P, et al. Clin Pharmacol Ther 63:444-452, 1998. Why Maintaining Warfarin Therapeutic Range is Critical European Atrial Fibrillation Trial Study Group, N Engl J Med 1995;333:5-10. Warfarin Levels Depend on Two Enzymes – CYP2C9 & VKORC1 Estimated Warfarin Dose (mg/day) Based on Genotypes CYP2C9 ACTIVITA 26 Prescribed Daily Warfarin Dose and CYP2C9 Genotype Warfarin Dose* Genotype 5.63 (2.56) *1/*1 4.88 (2.57) *1/*2 3.32 (0.94) *1/*3 4.07 (1.48) *2/*2 2.34 (0.35) *2/*3 1.60 (0.81) *3/*3 *Data presented as mean (SD) daily dose in mg From: Higashi MK, et al. Association between CYP2C9 genetic variants and anticoagulation-related outcomes during warfarin therapy. JAMA 287:1690-1698, 2002. Frequency of VKORC1 Alleles in Various Populations Sconce et al. Blood 2005, Yuan et al. Human Mol Genetics 2005, Schelleman et al. Clin Pharmacol Ther 2007, Montes et al Br J Haemat 2006 Another Anticoagulant Clopidogrel (Plavix) and CYP2C19 Alleles Interaction with drogs metabolized and/or reactingi with CYP2C9 29 Competition Enzyme inductor Enzyme inhibitor ASA a většina NSAID rifampicin fluvoxamin (ostatní SSRI slabí) fenobarbital, fenytoin fenobarbital, fenytoin omeprazol S-warfarin karbamazepin inhibitory HMG-CoA reduktázy losartan tolbutamid tolbutamid cimetidin (slabý) sulfonamidy, dapson azolová antimykotika (slabá) diazepam, tenazepam ritonavir fluoxetin, moclobemid desethylamiodaron zidovudin 17, 20, 21 20. Topinková E et al: Postgrad Med 2002; 5:477-82 21. Naganuma M et al: J Cardiovasc Pharmacol Ther 2001; 6:636-7 Metabolic rate • According to the activity of the enzyme may be a population divided into four main groups - poor metabolisers (PM), intermediate metabolizers (IM), efficient metabolizers (EM), and ultra-fast metabolizers (UM). • Most individuals among the white population - extensive metabolizers (EM) - the drugs are metabolized by the expected rate. • 5-10% of individuals are genetically determined poor metabolisers (PM) - the slow degradation of substances metabolised and are at a higher incidence of adverse events. • Intermediate metabolizers (IM) are represented in 10-15% and in long term treatment in response – comparable to PM. • Ultra-fast metabolizers (UM) – metabolization is intensive; clinically unresponsive to the usual doses of drugs - 5-10%. 31 BRONJ Age Obesity Smoking Cancer diagnosis Genetic background Osteonecrosis of the jaw induced by bisphosphonates (BP) BRONJ free BP users BRONJ BP users Genome-wide Sreening DNADNA SNPs in RBSM3 RBSM3 COL1 Prx1 Fibroblast + RBSM3 ; Col1 Expression Osteoporosis RBSM3 32 Methotrexate in RA • Effectiveness of treatment of rheumatoid arthritis (RA) by methotrexate (MTX) 46% - 65% (ACR20) • During treatment with MTX side effects may occur. At least one in 72.9% of patients, severe in 30% of patients. • gastrointestinal toxicity (nausea, vomiting, diarrhea, 20% - 65% • Hepatotoxicity 10% - 43% • oral ulceration 37% • alopecia to 4% • pulmonary toxicity 2.1% - 8% • Bone marrow suppression light 12% • pancytopenia 0.8% 33 Folát y Gastrointestiná lní toxicita Dihydrofolá ty Adenosin - uvolňování 5,10-methylen tetradydrofolát 5,10- methenyl tetrahydrofolát 10- formyl tetrahydrofolát 5-methyl tetradydrofolát Syntéza polyaminů 34 Methotrexate Ranganathan P, McLeod HL. A&R 2006 35 Methotrexate Ranganathan P, McLeod HL. A&R 2006 36 MDR1 • MDR1 (ATP-binding cassette B1/multidrug resistance 1) is an efflux pump that transports toxic endogenous substances, drugs and xenobiotics out of cells. • It is known to affect susceptibility to many hematopoietic malignancies. • ABCB1/MDR1 polymorphisms may either change the protein expression or alter its function, suggesting a possible association between ABCB1/MDR1 single nucleotide polymorphisms (SNP) and clinical aspects of T-cell lymphoma. • Therefore, association of two polymorphisms in the gene with clinical staging and therapy was evaluated. 37 Epigenetics 38 (A) An example of an experimentally verified miRNA pharmacogenomic set. miR-125 b inhibits vitamin D receptor (VDR) expression. Rukov J L et al. Brief Bioinform 2013;bib.bbs082 © The Author 2013. Published by Oxford University Press. 40 From: Esteller M, et al. Inactivation of the DNA-repair gene MGMT and the clinical response of gliomas to alkylating agents. NEJM 243:1350-1354, 2000. Why are some gliomas resistant to nitrosourea alkylating agents? Evidence suggests this may be the result of an epigenetic phenomenon – one that does not involve a change in DNA sequence. MGMT – methylguanine-DNA methyltransferase Methylation of the promoter region of MGMT may silence the gene 41 From: Esteller M, et al. Inactivation of the DNA-repair gene MGMT and the clinical response of gliomas to alkylating agents. NEJM 243:1350-1354, 2000. 42 From: Esteller M, et al. Inactivation of the DNA-repair gene MGMT and the clinical response of gliomas to alkylating agents. NEJM 243:1350-1354, 2000. 43 Personalized Drugs • Herceptin (breast cancer, target: Her2/neu) • Erbitux (colorectal cancer, target: EGFR) • Tarceva (lung cancer, target: EGFR) • Strattera (attention-deficit/hyperactivity disorder, Metabolism: P4502D6) • 6-MP (leukemia, Metabolism: TPMT) • Antivirals (i.e. resistance based on form of HIV) • etc. and the list is growing rapidly ... FDA Requires Genetic Tests for Certain Therapies Thank you for your attention „I just need a closer look...“