1 Pharmacogenetics: Improvement of Existing Drug Treatments Zhou Yan-Qiong

2 Background Background ： Clinical genetics Cytogenetic Somatic Cell Genetics Biochmical genetics Molecular genetics Cancer genetics Population genetics Immunogenetics Pharmacogenetics Genetic toxicology Developmental genetics Behavior genetics

3 PHARMACOGENETICS The study of genetically controlled variations in drug response

4 I. Key Concepts and Terms Monogenic: due to allelic variation at a single gene Polygenic: due to variations at two or more genes Polymorphic: frequently occurring monogenic variants occurring at a frequency >1%

5 Normal Distribution Frequency Activity

6 Polymorphic Distribution

7 GENETIC POLYMORPHISMS PharmacokineticPharmacodynamic Transporters Plasma protein binding Metabolism Receptors Ion channels Enzymes Immune molecules

8 From: Evans WE, Relling MV. Pharmacogenomics: Translating functional genomics into rational therapeutics. Science 286: , II. Genetic polymorphisms in drug metabolizing enzymes

9 Genetic polymorphisms in drug metabolizing enzymes 1. Polymorph of debrisoquine extensive metabolizer——EM poor metabolizer ——PM* ＞ 12.6 recessive transmission,autosomal

10 DRUGS WHOSE METABOLISM CO- SEGREGATES WITH DEBRISOQUINE alprenololamitriptylinebufuralolclomipramine codeinedesipramineencainideethylmorphine flecainidefluoxetineguanoxanimipramine metoprololnortriptylineparoxetinephenformin propafenonepropranolol

11 EM PM ： recessive transmission,autosomal racial diversify 2. Polymorph of Mephenetoin ：

12 3. Glucose-6-phosphate dehydrogenase activity Effects >300 million worldwide R- NH 2 CYP MPO PGH Synthase R-NOH ERYTHROCYTE R-NOH O2 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- NH 2

13 Drugs and Chemicals Unequivocally Demonstrated to Precipitate Hemolytic Anemia in Subjects with G6PD Deficiency AcetanilideNitrofurantoinPrimaquine Methylene BlueSulfacetamideNalidixic Acid NaphthaleneSulfanilamideSulfapyridine Sulfamethoxazole

14 INCIDENCE OF G6PD DEFICIENCY IN DIFFERENT ETHNIC POPULATIONS Ethnic GroupIncidence(%) Ashkenazic Jews0.4 Sephardic Jews Kurds53 Iraq24 Persia15 Cochin10 Yemen 5 North Africa<4 Iranians8 Greeks0.7-3

15 INCIDENCE OF G6PD DEFICIENCY IN DIFFERENT ETHNIC POPULATIONS Ethnic GroupIncidence(%) Asiatics Chinese 2 Filipinos13 Indians-Parsees16 Javanese13 Micronesians<1

16 4. N-ACETYLTRANSFERASE ACTIVITY Distribution of plasma isoniazid concentration in 483 subjects after and oral dose. Reproduced from Evans DAP. Br Med J 2:485, 1960.

17 ETHNIC DIFFERENCES IN THE DISTRIBUTION OF ACETYLATOR PHENOTYPE Population% Slow % Hetero Fast% Homo Fast South Indians Caucasians Blacks Eskimos Japanese Chinese From: Kalo W. Clin Pharmacokinet 7: , 1982.

18 XENOBIOTICS SUBJECT TO POLYMORPHIC ACETYLATION IN MAN Hydrazines isoniazid hydralazine phenylzine acetylhydrazine hydrazine Arylamines dapsone procainamide sulfamethazine sulfapyridine aminoglutethimide Carcinogenic Arylamines benzidine  -naphthylamine 4-aminobiphenyl Drugs metabolized to amines sulfasalazinenitrazepam clonazepamcaffeine

19 ADVERSE EFFECTS TO SULFASALAZINE IN PATIENTS WITH INFLAMMATORY BOWEL DISEASE Data from: Das et al. N Engl J Med 289: , Side Effect cyanosis hemolysis transient reticulocytosis Frequency of side effect Slow Acetylators Fast Acetylators

20 Relationship Between Onset of Lupus Syndrome in Fast and Slow Acetylators Receiving Procainamide. Data from: Woosley RL, et al. N Engl J Med 298: , 1978.

21 Distribution of acetylator phenotype in control subjects and those experiencing a sulfonamide hypersensitivity reaction. Rieder et al. Clin Pharmacol Ther 49:13-17, 1991.

22 NAT1 N-acetyl-SMX UDPGT SMX-glucuronide CYP2C9 MPO PGH SYNTHASE SMX hydroxylamine NitrosoDetox Covalent binding to cellular macromolecules/ cytotoxicity Hypersensitivity/ Adverse Reaction O-acetylation Acetoxy ester NAT1 Hydroxamic acid N,O-AT Detoxified metabolite

23 Future Role of SNPs and Pharmacogenetics SNP - Single Nucleotide Polymorphisms ……. G G T A A C T G …… ……. G G C A A C T G …... AS of February 2001, 1.42 million SNPs had been identified in the human genome.

24 Patients with efficacy in clinical trials Patients without efficacy in clinical trials Predictive of efficacy Predictive of no efficacy