Falk Symposium 156: Genetics in Liver Disease. Pharmacogenetics. Gerd Kullak-Ublick

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1 Falk Symposium 156: Genetics in Liver Disease Pharmacogenetics Gerd Kullak-Ublick Division of Clinical Pharmacology and Toxicology Department of Internal Medicine University Hospital Zurich Freiburg, 8. October 2006

2 Pharmacogenetics Genetic factors that determine an individual s response to drug treatment Polymorphism Genetic variant that occurs with a frequency of at least 1% in the general population Haplotype Combination of different polymorphisms on one allele of a gene

3 Genetic determinants of drug response Pharmacokinetics Pharmacodynamics Disease genotype Comorbidity

4 Genetic differences that influence drug pharmacokinetics: Drug uptake from the intestine into blood (e.g. MDR1 at the apical membrane of enterocytes) Phase I and phase II metabolism Drug efflux Genetic differences that influence drug pharmacodynamics: Target receptors (e.g. β-receptors in the treatment of arterial hypertension

5 Genetic polymorphisms in drug metabolism

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7 Relative importance of P450 polymorphisms in drug metabolism

8 Alleles with (multi-)duplicated CYP2D6*2 genes Johansson et al., PNAS 1993;90:1945 Aklillu et al., JPET 1996;278:441

9 Nortriptyline dosing dependent on CYP2D6 metabolizer phenotype - based on the European population with 7% poor metabolizers and 5.5% ultrarapid metabolizers overall - Ingelman-Sundberg M., Trends Pharmacol Sci 2004;25:193

10 CYP2D6-based dose adjustments for antidepressants and antipsychotics

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12 Warfarin dose requirements and CYP2C9 Warfarin dose (mg/day) Peyvandi et al., Clin Pharmacol Ther 2004

13 Pharmacogenetics-based dose adjustments according to differences in pharmacokinetics Kirchheiner et al., Nature Rev Drug Discov 2005; 4: 639

14 Examples of clinical impact of cytochrome P450 pharmacogenetics Dose % of ctrl Disease Enzyme UMs PMs Examples Depression CYP2C9 Bipolar disoders and valproate CYP2C19 40 PMs and SSRIs CYP2D Non-responders (UMs) and side effects of tricyclics (PMs) Psychosis CYP2D Haloperidol and parkinsonian side effects Ulcer CYP2C19 20 Dosing of PPIs ph and gastrin changes Cancer CYP2B6 Cyclophosphamide metabolism CYP2D Non-response of antiemetic drugs (UMs) CV CYP2C9 30 Warfarin dosing (acenocoumarol) Irbesartan and blood pressure response CYP2D Perhexiline neuropathy and hepatotoxicity Pain CYP2D6 Codeine no response (PMs) Epilepsia CYP2C9 Phenytoin pharmacokinetics and side effects

15 Drug Drug therapy in IBD Genes associated with drug response Azathioprine 6-mercaptopurine 5-aminosalicylates sulfasalazopyridin Thiopurine methyltransferase N - acetyltransferase 1 N - acetyltransferase 2 TPMT NAT1 NAT2 Glucocorticoids Glucocorticoid receptor β hgrβ Multidrug resistance gene product 1 MDR1 Transporter of antigenic peptide 2 Infliximab (anti-tnfα) Fc gamma receptor IIIa (V/V better response than F/F) TAP2 FCGR-3A ICAM-1 / rhuil-10 / natalizumab

16 DNA RNA 6 -thioguanine nucleotides TPMT: thiopurine methyltransferase TPMT 6-methylmercaptopurine 6 -thioisonine 5 -monophosphate TPMT 6-methyl-mercaptopurine ribonucleotides Purine synthesis

17 Variations of TPMT genotype (chromosome 6p22.3, 9 introns, 10 exons) wild type 55% of deficient phenotypes 75% of deficiencies *3A/*1 and *3B/*3C cannot be discriminated: *3A/*1: intermediate activity (TPMT H/L ) *3B/*3C: no enzyme activity (TPMT L/L ) Schütz E et al., Clin Chem 2001;46:11, 1728

18 TPMT activity in relation to genotype TPMT activity [nmol MTG/g*Hb*h -1 ] Wusk B, Kullak-Ublick G et al., Eur J Clin Pharmacol 2004; 60: 5

19 Frequency of TPMT activity distribution in IBD patients n = 240 TPMT H/H Frequency [%] TPMT H/L TPMT activity [nmol MTG/g*Hb*h -1 ] Wusk B, Kullak-Ublick G et al., Eur J Clin Pharmacol 2004; 60: 5

20 Thiopurine methyltransferase allelic polymorphism low TPMT act. 1/300 intermediate TPMT act. 11% high TPMT act. 89%? very high TPMT act. severe bone marrow toxicity!! + high risk for bone marrow toxicity clinical response low risk low risk? poor responders -

21 intron 26: T(+2) A splicing mutation in the MDR3 gene BSEP MDR3 cholangitis Bile acids Phospholipids Hepatozyt hepatocyte Bile ducts cytokeratin 19 staining Pauli-Magnus and Kullak-Ublick, Pharmacogenetics 2004; 14: 91

22 MDR3 mutations in intrahepatic cholestasis of pregnancy Exon 9: S320F Exon 19: G762E COOH NH 2 ATP-binding ATP-binding Pauli-Magnus et al., Pharmacogenetics 2004

23 MDR3 mutations in intrahepatic cholestasis of pregnancy COOH NH 2 Intron 21: G(+1)A Intron 25: G(+5)C Intron 25: C(-3)G Intron 26: T(+2)A Pauli-Magnus et al., Pharmacogenetics 2004

24 PSC and PBC specific nonsynonymous MDR3 variants PSC PBC Control Common Pauli-Magnus et al., Hepatology 2004; 39: 779

25 Distribution of major MDR3 haplotypes Pauli-Magnus et al., Hepatology 2004; 39: 779

26 PSC and PBC specific nonsynonymous BSEP variants PSC PBC Control Common Pauli-Magnus et al., Hepatology 2004; 39: 779

27 Distribution of major BSEP haplotypes Pauli-Magnus et al., Hepatology 2004; 39: 779

28 BSEP expression in human liver tissue correlates with the 1457T>C polymorphism (V444A) in the BSEP gene BSEP protein expression (n=110): number of patients Mean ± SD: 0.00 ± BSEP expression BSEP expression V444A allele frequency 1457C: 57% -1.5 Meier Y et al., TT (VV) CC (AA) TC (VA)

29 The 1457T>C polymorphism in the BSEP gene is a genetic risk factor for drug-induced cholestasis Cholestasis antibiotics (10) Hepatitis others (2) PPI (1) statins (3) % % 54% T allele C allele contraceptives (1) 70 57% antibiotics (5) contraceptives (5) statins (2) antipsych. (2) PPI (2) others (2) Lang C. et al, Pharmacogenetics Genomics, in press cholestasis (n=48) hepatitis (n=24) controls (n=420)

30 Kinetic characterization of the V444A BSEP variant Lang C. et al, Pharmacogenetics Genomics, in press

31 Inhibition of BSEP mediated taurocholate transport (3 µm) by fluvastatin Lang C. et al, Pharmacogenetics Genomics, in press

32 Cases with BSEP deficiency syndrome Intron 4 (+3)A>G) PFIC2 K903X E297G BRIC2 R432T Noé J., Kullak-Ublick et al., J Hepatol 2005; 43: 536

33 Altered BSEP protein expression in BSEP deficiency syndrome PFIC2 BRIC2 BSEP PFIC2 MRP2 BSEP BRIC2 Noé J., Kullak-Ublick et al., J Hepatol 2005; 43: 536

34 Altered BSEP function in BSEP deficiency syndrome K m μm 15 Reference BSEP E2997G 22 6 R432T Noé J., Kullak-Ublick et al., J Hepatol 2005; 43: 536

35 Pharmacokinetic determinants of drug response Metabolism CYP2D6 CYP2C9 CYP2C19 Distribution OATP1B1 TPMT Nuclear receptors Absorption OCTN1 OCTN2 Elimination BSEP MDR3 MDR1

36 Strategies needed to identify the relevant genes for a given drug: Candidate gene approaches based on known pharmacokinetic and pharmacodynamic factors Genome-wide haplotype mapping Gene expression analyses Proteomic methods

37 Determinants of drug response Age Sex Genetic factors Drug response Comorbidity Polypharmacy Nutrition Alcohol