Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

Pharmacogenetics devang

2,551 views

Published on

Pharmacogenetics

Published in: Technology, Health & Medicine
  • Be the first to comment

Pharmacogenetics devang

  1. 1. PHARMACOGENETICS Treating Disease Using an Understanding of Genetics Prepared by: Devang Parikh Department of Pharmacology S.B.K.S. M.I.&R.C.
  2. 2. • Introduction of Pharmacogenetics • Human Genome Project • Pharmacogenomic effects on few drugs • Potentials of Pharmacogenomics • Pharmacogenomics and Drug Development • Personalized Medicine • Pharmacogenomics Knowledge Base- website KEY OBJECTIVES
  3. 3. Rx +  =  Rx +  =  ???? Rx +  =  Why Pharmacogenetics ???
  4. 4. Rx +  =  Rx +  =  Differences in genetic constitution Rx +  = 
  5. 5. All patients with same diagnosis 1 2 Responders and patients not predisposed to toxicity Non-responders and toxic responders Treat with alternative drug or dose Treat with conventional drug or dose The Promise of Personalized Medicine
  6. 6.  Pharmacogenetics › Study of how genetic differences in a SINGLE gene influence variability in drug response (i.e., efficacy and toxicity)  Pharmacogenomics › Study of how genetic (genome) differences in MULTIPLE genes influence variability in drug response (i.e., efficacy and toxicity)
  7. 7. Time line of genomic discoveries
  8. 8.  Determine the sequence of the 3 billion nucleotides that make up human DNA (completed by April 2003)  Characterize variability in the genome  Identify all the genes in human DNA International HapMap Project: Identifying common haplotypes in four populations from different parts of the world Identifying ―tag‖ SNPs that uniquely identify these haplotypes A small number of SNP patterns (haplotypes) can account for 80-90% of entire human population
  9. 9.  Genotype: pair of alleles a person has at a region of the chromosome  Phenotype: outward manifestation of a genotype.  Monogenic: due to allelic variation at a single gene  Polygenic: due to variations at two or more genes
  10. 10.  Mutation: difference in the DNA code that occurs in less than 1% of population › Often associated with rare diseases  Cystic fibrosis, sickle cell anemia, Huntington’s disease  Polymorphism: difference in the DNA code that occurs in more than 1% of the population › A single polymorphism is less likely to be the main cause of a disease › Polymorphisms often have no visible clinical impact
  11. 11. Types of Polymorphisms  Single Nucleotide Polymorphism (SNP): GAATTTAAG GAATTCAAG  Simple Sequence Length Polymorphism (SSLP): NCACACACAN NCACACACACACACAN NCACACACACACAN  Insertion/Deletion: GAAATTCCAAG GAAA[ ]CCAAG
  12. 12. DRUG TARGETS DRUG METABOLIZING ENZYMES DRUG TRANSPORTERS PHARMACOKINETICSPHARMACODYNAMICS Variability in Efficacy/Toxicity •Transporters •Plasma protein binding •Metabolising enzymes •Receptors •Ion channels •Enzymes •Immune molecules
  13. 13. Polymorphisms Drug metabolism Adverse Drug Reaction Disease susceptibility Receptor sensitivity Drug transport Responders/ Non-responders Consequences of polymorphisms
  14. 14. These mutations may have  no effect on enzyme activity(normal)  Lead to enzyme activity with Decreased activity Absent activity  Duplications lead to increased enzyme activity  Wild or normal activity enzymes (75 – 85%) of population  Intermediate metabolizers (10 -15%)  Poor metabolizers (5 – 10%)  Ultra-rapid metabolizers (2 – 7%) of population – multiple genes
  15. 15. Genetic mechanism influence pharmacotherapy 1 - Genetic Polymorphism of genes  which results in Altered metabolism of drugs (metabolism of TCAs) Increased or decreased metabolism of a drug may change its concentration Of active, inactive or toxic metabolites
  16. 16. DRUG TRANSPORTERS
  17. 17.  MDR1 encodes a P-glycoprotein (an energy- dependent transmembrane efflux pump) There are 7 different ABC transporters MDR1 is important among them. Expressions of P-glycoprotein in different tissues P-glycoprotein serves a protective role by transporting toxic substances or metabolites out of cells.
  18. 18. Increased intestinal expression of P-glycoprotein •limit the absorption of P-glycoprotein substrates, •thus reducing their bioavailability and preventing attainment of therapeutic plasma concentrations. Decreased P-glycoprotein expression result in •supratherapeutic plasma concentrations of relevant drugs •Thus produces drug toxicity.  Polymorphism in Exon 26(C3435T), Exon 21(G2677T/A) significantly affect P-gp expression.
  19. 19. Category Substrates of P-gp Anti-cancer agents Actinomycin D, Vincristine,etc Cardiac drugs Digoxin, Quinidine etc HIV protease inhibitors Ritonavir, Indinavir etc Immunosuppressants Cyclosporine A, tacrolimus etc Antibiotics Erythromycin,levofloxacin etc Lipid lowering agents Lovastatin, Atorvastatin etc Substrates of P-glycoprotein Dipeptide transporter, organic anion and cation transporters, and L-amino acid transporter. Other Polymorphic Drug Transporters
  20. 20. Drug Transport
  21. 21. 2 – Genetic variants may produce  unexpected drug effect (toxicity or anaphylactic reaction) Hemolysis in glucose -6 –phosphate dehydrogenase deficiency 3 – Genetic variation in drug targets May alter the clinical response & frequency of side effects Variants of β –adrenergic receptor alter response to β – agonists in asthma patients
  22. 22. DRUG METABOLISM
  23. 23.  Evidence of an inherited basis for drug response dates back in the literature to the 1950s › Succinylcholine: 1 in 3000 patients developed prolonged muscle relaxation. •usual paralysis lasted 2 to 6 min in patients. •occasional pt exhibited paralysis lasting hrs •cause identified as an ―atypical‖ plasma cholinesterase (1/100 affinity than normal enzyme) Hydrolysis by pseudocholinesterase choline succinylmonocholine O C CH2CH2 O (H3C)3NH2CH2C C O O CH2CH2N(CH3)3 + + SUCCINYLCHOLINE
  24. 24. Phase I: biotransformation reactions: oxidation, hydroxylation, reduction, hydrolysis Phase II: conjugation reactions—to increase their water solubility and elimination from the body. The reactions are glucuronidation, sulation,acetylation, glutathione conjugation
  25. 25. 1A2 19% 2D6 3% 2E1 10% 3A4/5 42% 2C9 2C19 26% 1A2 5% 2D6 24% 2E1 1% 3A4/5 51% 2C9 2C19 19% Primary CYP Enzymes in Drug Metabolism % of total enzyme % of drugs metabolised
  26. 26. CYP2C9: Phenytoin, warfarin, NSAIDs etc CYP2C19: Omeprazole, proguanil, diazepam CYP2D6: More than 60 drugs CYP2E1: Ethanol CYP1A6: Nicotine Phase - I enzymes known to have polymorphism
  27. 27. CYP 450 gene Mutant Alleles Substrates CYP2C9*1 *2, *3, *4, *5, *6 Warfarin, losartan phenytoin, tolbutamide CYP2C19*1 *2, *3, *4, *5, *6, *7, *8 Proguanil, Imipramine, Ritonavir, nelfinavir, cyclophosphamide CYP2D6*1 *1XN, *2XN, *3,*4,*5, *6 *9,*10,*17 Clonidine, codeine, promethazine, propranolol, clozapine, fluoxetine, haloperidol, amitriptyline Mutant alleles of Phase I enzymes Red: Absent; Blue: Reduced; Green: Increased activity
  28. 28.  NAT2: Isoniazid, hydralazine,  GST: D-Penicillamine  TPMT: Azathioprine, 6-MP  Pseudocholinesterase: Succinyl choline  UGT1A1: Irinotecan
  29. 29. Gene Mutant Alleles Substrates NAT2 *2, *3, *5, *6,*7, *10,*14 Isoniazid, hydralazine, GST M1A/B, P1 M1 null, T1 null D-penicillamine TPMT *1,*2,*3A,C, *4-*8 Azathioprine, 6-MP UGT1A1 *28 Irinotecan Red: Absent; Blue: Reduced; Mutant alleles of Phase II enzymes
  30. 30. Normal CYP2D6 : 150 mg/day Mutant CYP2D6 : 10-20 mg/day
  31. 31. RECEPTOR SENSITIVITY
  32. 32. Receptor Sensitivity/Effect 1 receptor gene Arg389Gly Ser49Gly Subjects with Gly 389 have reduced sensitivity to beta-blockers Subjects with Gly 49 have increased sensitivity to beta-blockers 2 receptor gene Arg16Gly Gln27Glu Response to salbutamol is 5.3 fold lower in Gly16 asthmatics. Subjects with Glu27 have strong resistance to beta 2 agonists
  33. 33. 10 fold difference in concentration required between genotypes(adenylyl cyclase activity)
  34. 34. RESPONDERS & NON-RESPONDERS
  35. 35. Disease Gene and Polymorphism Allele/ Genotype Effect Asthma ALOX5 Promoter region mut Respond poorly to antileukotriene treatment with ABT- 761 Atherosclerosis CETP TaqIB B2/B2 Poor response to treatment with pravastatin Smoking cessation CYP2B6 C1459T TT Greater craving for cigarettes and higher relapse rates Heart failure 2 AR gene Gln27Glu Glu27 Better response to carvedilol treatment
  36. 36. ADVERSE DRUG REACTIONS
  37. 37.  Inter –individual difference in genetic constitution  inter ethnic group variability 49% of ADRs are associated with Drugs that are substrates for Polymorphic Drug metabolising enzyme.
  38. 38. Subjects who are carriers of at least one mutant allele (*2 or *3) are 4 times more susceptible to bleeding complications in spite of low dose administration
  39. 39. • 1º and 2º prevention of venous blood clots • patients with prosthetic heart valves or atrial fibrillation • 1º prevention of acute myocardial infarction in high-risk men • prevention of stroke, recurrent infarction, or death in patients with acute myocardial infarction • has a narrow therapeutic window • considerable variability in dose response among subjects • subject to interactions with drugs and diet • laboratory control that can be difficult to standardize • problems in dosing as a result of patient nonadherence Warfarin- anti-coagulant therapy
  40. 40. • prothrombin time and the international normalized ratio (INR) are monitored • doses are adjusted to maintain each patient's INR within a narrow therapeutic range(2.5-3.5) • INR of < 2 is associated with an increased risk of thromboembolism • INR of > 4 is associated with an increased risk of bleeding Clinical management
  41. 41. Warfarin, which is metabolized by CYP2C9, inhibits the vitamin K cycle via actions on thiol-dependent enzymes, such as VKORC1, that are required for regeneration of active vitamin K Pereira, N. L. and Weinshilboum, R. M. (2009) Cardiovascular pharmacogenomics and individualized drug therapy Nat. Rev. Cardiol. doi:10.1038/nrcardio.2009.154
  42. 42. Clearance of S-warfarin and time to achieve steady-state (5x T1/2) *1/*1: ~ 3 days *1/*2: ~ 6 days *1/*3: ~ 12 days Haplotype A (-1639GA, 1173CT): lower maintenance dose Haplotype B (9041GA): higher maintenance dose VKORC1 A/A: 2.7 ± 0.2 mg/d VKORC1 A/B: 4.9 ± 0.2 mg/d VKORC1 B/B: 6.2 ± 0.3 mg/d Mean maintenance dose: 5.1 ± 0.2 mg/d principal enzyme that catalyzes the conversion of S-warfarin to inactive 6- hydroxy and 7-hydroxy metabolites Converts inactive Vit K in to active Vit K hydroquinone
  43. 43.  Patients having TPMT*2, *3A and *3C alleles have low enzyme activity  They are at risk for excessive toxicity, especially fatal myelosuppression, even at standard dose of azathioprine, mercaptopurine and thioguanine
  44. 44. Drugs Demonstrated to Precipitate Hemolytic Anemia in Subjects with G6PD Deficiency Nitrofurantoin Primaquine Dapsone Methylene Blue Sulfacetamide Nalidixic Acid Naphthalene Sulfanilamide Sulfapyridine Sulfamethoxazole INCIDENCE OF G6PD DEFICIENCY IN DIFFERENT ETHNIC POPULATIONS Ethnic Group Incidence(%) Asiatics Chinese 2 Filipinos 13 Indians-Parsees 16 Japanese 13
  45. 45. Pharmacogenomic Biomarkers as Predictors of Adverse Drug Reactions Gene Relevant Drug TMPT 6-mercaptopurines UCT1A1*28 Irinotecan CYP2C0 and VKORC1 Warfarin CYP2D6 Atomoxetine; Venlafaxine; Risperidone; Tiotropium bromide inhalation; Tamoxifen; Timolol Maleate; Fluoxetine HCL; Olanzapine; Cevimeline hydrochloride; Tolterodine; Terbinafine; Tramadol; Acetamophen; Clozapine; Aripiprazole; Metoprolol; Propranolol; Carvedilol; Propafenone; Thioridazine; Protriptyline HCl; Tetrabenazine; Codeine sulfate; Fiorinal with Codeine; Fioricet with Codeine CYP2C19 Omperazole HLA-B5701 Abacavir HLA-B1502 Carbamazepine G6PD Deficiency Rasburicase; Dapsone; Primaquine; Chloroquine MDR1 Protease inhibitors ADD1 Diuretics Ion channel genes QT prolonging antiarrhythmics CRHR1 Inhaled steroids
  46. 46. DISEASE SUSCEPTIBILITY
  47. 47. Disease Gene Polymorphism Allele/ Genotype Effect Hypertension AGT M235T T allele  BP ACE ACEI/D DD  risk AT1R A1166C C  risk β1 AR Arg389Gly Arg389  risk Atherosclerosis CETP TaqIB B2/B2  risk Genetic polymorphism & disease susceptibility
  48. 48. Disease Gene Allele/ Genotype Effect Acute MI CYP2C9 eNOS *3 T786C susceptibility to AMI. Alzheimer’s disease ApoE ε 2 ε 4/ ε4 Reduced risk Poor prognosis Cancer GST M1 Null T1 Null  susceptibility to lung and bladder cancer NAT NAT2 *10  susceptibility to colorectal cancer
  49. 49. Drugs Demonstrated to Precipitate Hemolytic Anemia in Subjects with G6PD Deficiency Nitrofurantoin Primaquine Methylene Blue Sulfacetamide Nalidixic Acid Naphthalene Sulfanilamide Sulfapyridine Sulfamethoxazole INCIDENCE OF G6PD DEFICIENCY IN DIFFERENT ETHNIC POPULATIONS Ethnic Group Incidence(%) Asiatics Chinese 2 Filipinos 13 Indians-Parsees 16 Japanese 13
  50. 50. Pharmacogenomic Biomarkers as Predictors of Adverse Drug Reactions Gene Relevant Drug TMPT 6-mercaptopurines UCT1A1*28 Irinotecan CYP2C0 and VKORC1 Warfarin CYP2D6 Tricyclic antidepressants Beta blockers Tamoxifin CYP2C19 Omperazole HLA-B5701 Abacavir HLA-B1502 Carbamazepine HLADRB1*07 and DQA1*02 Ximelagatran MDR1 Protease inhibitors ADRB1 Beta blockers ADRB2 B agonists ADD1 Diuretics Ion channel genes QT prolonging antiarrhythmics RYR1 General anesthetics CRHR1 Inhaled steroids HMGCR Statins Adapted from: Ingelman-Sundberg M. N Engl J Med 358:637-639, 2008. Roden DM et al. Ann Intern Med 145:749-57, 2006.
  51. 51. Biomarker Drugs Associated with this Biomarker C-KIT expression Imatinib mesylate CCR5 -Chemokine C-C motif receptor Maraviroc CYP2C19 Variants Clopidogrel; Voriconazole; Omeprazole; Pantoprazole; Esomeprazole; diazepam; Nelfinavir; Rabeprazole CYP2C9 Variants Celecoxib; Warfarin CYP2D6 Variants Atomoxetine; Venlafaxine; Risperidone; Tiotropium bromide inhalation; Tamoxifen; Timolol Maleate; Fluoxetine HCL; Olanzapine; Cevimeline hydrochloride; Tolterodine; Terbinafine; Tramadol; Acetamophen; Clozapine; Aripiprazole; Metoprolol; Propranolol; Carvedilol; Propafenone; Thioridazine; Protriptyline HCl; Tetrabenazine; Codeine sulfate; Fiorinal with Codeine; Fioricet with Codeine Deletion of Chromosome 5q(del(5q) Lenalidomide DPD Deficiency Capecitabine; Fluorouracil Cream; Fluorouracil Topical Solution & Cream EGFR expression Erlotinib; Cetuximab; Gefitinib; Panitumab Familial Hypercholesterolemia Atorvastatin G6PD Deficiency Rasburicase; Dapsone; Primaquine; Chloroquine Her2/neu Over-expression Trastuzumab; Lapatinib HLA-B*1502 allele presence Carbamazepine HLA-B*5701 allele presence Abacavir KRAS mutation Panitumumab; Cetuximab NAT Variants Rifampin, isoniazid, and pyrazinamide; Isosorbide dinitrate and Hydralazine hydrochloride Philadelphia Chromosome-positive responders Busulfan; Dasatinib; Nilotinib PML/RAR alpha gene expression Tretinoin; Arsenic Oxide Protein C deficiencies Warfarin TPMT Variants Azathioprine; Thioguanine; Mercaptopurine UGT1A1 Variants Irinotecan; Nilotinib Urea Cycle Disorder (UCD) Deficiency Valproic acid; Sodium Phenylacetate and Sodium Benzoate; sodium phenyl butyrate Vitamin K epoxide reductase (VKORC1) Variants Warfarin
  52. 52. Routine Use of Genetics is Coming Soon! • Good prognosis vs. poor prognosis • Which patients need more intensive or longer therapy • Which patients should receive specific types of therapy • Which patients should not receive specific types of therapy
  53. 53. • How Using Genetics Can Improve Medical Safety and Efficacy • Rapidly expanding field that will have a major impact on how we treat diseases • Help identify who will respond to a specific therapy • Help identify who is at risk for side effects of treatment • Help identify the appropriate dosing for individual patients • Assist in determining which patients are or are not good candidates for a specific type of therapy
  54. 54.  Creating opportunities to increase the value of the drugs we develop using genetics › Distinguish subgroups of patients who respond differently to drug treatment › Aid interpretation of clinical study results › Obtain greater understanding of disease  Predict disease severity, onset, progression  Identify genetic subtypes of disease  Aid in discovery of new drug targets
  55. 55.  Genome wide approach versus candidate gene approach  Thousands of SNPs  Thousands of patients  Replication studies  Sophisticated databases housing pharmacogenomic information  Drug selection and dosing algorithms incorporating non- genetic and genetic information  Integrating genetics with other technologies  Transcriptomics, Proteomics, Metabonomics, Imaging, PK/PD modelling  A combined approach to diagnosis & prescription
  56. 56.  80% of products that enter the development pipeline FAIL to make it to market  Pharmacogenomics may contribute to a ―smarter‖ drug development process › Allow for the prediction of efficacy/toxicity during clinical development › Make the process more efficient by decreasing the number of patients required to show efficacy in clinical trials › Decrease costs and time to bring drug to market
  57. 57. Idea Marketed Drug Years 11-15 Years Discovery Exploratory Development Full Development Phase I Phase II Phase III 0 155 10 Patent life 20 years Phase IV It costs >$800 million to get a drug to market
  58. 58. Applying Pharmacogenomics . DISEASE GENETICS TARGET VARIABILITY SELECTING RESPONDERS PHARMACO- GENETICS Discovery Development Choosing the Best Targets Better Understanding of Our Targets Improving Early Decision Making Predicting Efficacy and Safety
  59. 59. Current Options Options with Pharmacogenomics Proportionofpatientsshowing poorornoresponse Low High Continue clinical trials to market Abandon drug before market Optimize clinical trials, making them smaller and shorter Continue trials safely by excluding at-risk pts
  60. 60.  Targeted Therapies: › Herceptin: treatment of HER2 positive metastatic breast cancer › Gleevec: treatment for patients with Philadelphia chromosome-positive chronic myeloid leukemia › Erlotinib: treatment for non-small cell lung cancer  Most effective in epidermal growth factor receptor positive tumors › Maraviroc (not approved): treatment for HIV  Studies have incorporated a screening process for different receptors that HIV uses to gain access to cells › Iloperidone (not approved): schizophrenia treatment  Company identified a genetic marker that predicts a good response to the drug
  61. 61.  Publicly accessible knowledge base › www.pharmgkb.org  Goal: establish the definitive source of information about the interaction of genetic variability and drug response 1. Store and organize primary genotyping data 2. Correlate phenotypic measures of drug response with genotypic data 3. Curate major findings of the published literature 4. Provide information about complex drug pathways 5. Highlight genes that are critical for understanding pharmacogenomics
  62. 62. Patient requires Treatment Examination by the Physician Genomic testing Traditional investigations EXPERT SYSTEM Decision making by Physician, assisted by an Expert System (interactive interpretation) Prescribes individualized drug treatment
  63. 63. Roche Diagnostics Launches the AmpliChip CYP450 in the US, - the World’s First Pharmacogenomic Microarray for Clinical Applications
  64. 64. Personalized medicine S M A R T C A R D Person’s name GENOME (Confidential) “Here is my sequence”
  65. 65. elusive dream or imminent reality?

×