Same Medicine, Different Result Pharmacogenetics: Where Are We Now?

1. Same Medicine, Different ResultPharmacogenetics: Where Are We Now? Dr Richard FitzGerald Molecular & Clinical Pharmacology Institute of Translational Medicine University of Liverpool Richard.Fitzgerald@liverpool.ac.uk

2. The drugs don’t work.......

3. ....... they just make it worse.

4. ‘If it were not for the great variability among individuals, medicine might as well be a science and not an art.’ Sir William Osler, 1892 The problem: variability

5. Pythagoras (6th Century B.C.) • “…..be far from fava beans consumptions” • Met death in Ancient Italy because he refused to cross a field of beans • Many theories: • Contained souls • Looked like testicles • flatulence • Medical reason FAVISM RBC haemolysis Fava beans

6. First suggested by Sir Archibald Garrod that genetics may affect chemical transformations He used the example of alkaptonuria (1902) ‘Chemical Individuality’ ‘One gene, one enzyme’

7. Modern pharmacogenetics

9. Types of Genetic Variation

11. Drug Response: a complex trait?

12. The early years: one gene, one disease • Robert Smith investigated debrisoquine (a commercially available anti-hypertensive) • He took the tablet, along with most of his laboratory staff • He collapsed and became markedly hypotensive. Nobody else did.

14. CYP2D6 Major Alleles

15. Nortriptyline pharmacogenetics

16. Codeine phosphate

17. Drug metabolising enzymes Most DME have clinically relevant polymorphisms Those with changes in drug effects are separated from pie.

18. Azathioprine Xanthine oxidase TPMT Thiouric acid 6-Mercaptopurine 6-Me MP HGPRT 6-thioinosine nucleotide IMPDH 6-thioguanine nucleotides Immunosupression Clinical benefit

19. TPMT (Thiopurine methyltransferase) Allelic polymorphism High TPMT 89% Low TPMT 1/300 Intermediate TPMT 11% ?very high TPMT Severe Bone Marrow Suppression High risk of marrow suppression Low risk Low risk ? poor responders - + clinical response

21. PGx: current applications

22. Abacavir Hypersensitivity • Nucleoside analogue • Reverse transcriptase inhibitor • Hypersensitivity 5% • Fever, skin rash, gastro-intestinal symptoms, eosinophilia within 6 weeks • Re-challenge results in a more serious reaction

23. Association with HLA-B*5701 Clinical phenotype Causal chemical Clinical genotype Abacavir Hypersensitivity

24. PGx: effects on drug usage Data from RLBUHT courtesy of Prof SayeKhoo

25. PREDICT-1

26. Abacavir Genetics: Why so Rapidly Implemented? • Implemented even before RCT evidence • In some cases, observational study designs may provide adequate evidence • Successful implementation was because of several factors: • Good and replicated evidence of a large genetic effect size • Clinician community amenable to rapid change in clinical practice • Vocal and knowledgeable patient lobby

27. Carbamazepine-induced hypersensitivity reactions 5% of patients on carbamazepine (CBZ) develop hypersensitivity reactions 10% in prospective SANAD study (UK) Clinical manifestations • Maculopapular exanthema usually mild • Hypersensitivity reaction (HSS) 1/1000 patients Fever, hepatitis, eosinophilia • Stevens-Johnson syndrome Toxic epidermal necrolysis 5-30% fatality rate

28. FDA warning • PATIENTS WITH ASIAN ANCESTRY SHOULD BE SCREENED FOR THE PRESENCE OF HLA-B*1502 PRIOR TO INITIATING TREATMENT WITH Carbamazepine.

29. To prospectively identify subjects at risk for SJS • 4877 CBZ naive subjects from 23 hospitals • The Taiwan SJS Consortium HLA-B*1502 testing → 0 incidence of SJS/TEN

30. University of Liverpool (SANAD, EUDRAGENE, Swiss, WT Sanger, Harvard) • EPIGEN Consortium (Ireland, Duke University, UCL, Belgium) • Faculty of 1000 -top 2% of published articles in biology and medicine • American Academy of Neurology meeting- voted as one of the top articles in neurology this year

31. HLA-A*3101 HLA-A*3101 22 patients with HSS 43 patients with MPE 2691 healthy control subjects 1296 healthy control subjects McCormack et al. NEJM 2011

32. Pooled analysis of case-control studies P=0.03 P=8 x10-7 P=8 x10-5 P=1x10-7 P= McCormack et al. NEJM 2011

33. GWAS identifies HLA-A*3101 allele as a genetic risk factor for CBZ-induced cutaneous adverse drug reactions in Japanese population HLA-A*3101 Ozeki et al. Hum Mol Genet 2011

34. Conclusions • HLA-A*3101 - a prospective marker for CBZ hypersensitivity • Associated with several phenotypes • Further work needed to enable clinical use • Need for consortia • Possibility of rare variants and CNVs (exome-sequencing/WGS) • Mechanistic studies to follow genetics

35. Flucloxacillin-Induced Cholestatic Hepatitis: Whole Genome Scan • Illumina 1 million SNP array • Strong (P=10-30) association with SNP in LD with HLA-B*5701 • Weaker association with novel marker on chromosome 3 (p < 1.4 x 10-8 ) • Weak association with copy number polymorphism Daly at al, 2009 Performed in collaboration with the Serious Adverse Event Consortium

36. Implicated SNP is in the SLCO1B1 gene (transporter) Shown with simvastatin 40mg and 80mg C variant may account for 60% of the cases of myopathy

37. Clopidogrel Pharmacogenetics

38. Stent Thromb HR 2.61; 95% CI 1.61-4.37, P<0.00001

39. All events: HR 1.57; 95% CI 1.13-2.16, P=0.006

40. Conclusions • Clear adverse effect of the CYP2C19*2 polymorphism on clinical and pharmacodynamic outcomes • PD Meta-analysis limited by multiple outcome measures • Potential utility in CYP2C19*2 as marker of clopidogrel non-response and risk of adverse outcome • Translation into clinical practice • Increase dose of clopidogrel from 75mg/day to 150mg/day • Evidence from CURRENT-OASIS 7 trial • Bleeding risk • Use of alternative anti-platelet drugs (Prasugrel, Ticagrelor) • Better platelet inhibition • Higher rates of bleeding (+ other adverse effects) • Benefit may be only seen in those with the CYP2C19*2 allele • Cost

41. Warfarin: a more complex variation • Widely used drug • A variety of acute/chronic indications • Large numbers of patients • 6% of all patients over 80 years of age • Narrow therapeutic index • Drug interactions and alcohol • Efficacy

42. Bleeding complications: • 10-24 per 100-patient years • 10% of all ADR-related hospital admissions

43. The clinical phenotype • 10-50 fold variability in dose requirements • Increased age; decreased requirements • 8% decrease in warfarin dose per decade • Enhanced responsiveness (PD) • Reduced clearance (PK)

45. Warfarin and metabolism by CYP2C9 CYP2C9*1 Wild Type Arg144 Ile359 CYP2C9*2 Arg144Cys : interaction with cytochrome P450 reductase CYP2C9*3 Ile359Leu : substrate binding site : affects Km, Vmax Variant alleles have 5-12% of the activity of wild-type • Steward et al, Pharmacogenetics (1997), 7, 361-367

46. CYP2C9 genotype Number of patients Aggregate mean dose (mg) CYP2C9*1*1 639 5.5 CYP2C9*1*2 207 4.5 CYP2C9*1*3 109 3.4 CYP2C9*2*2 7 3.6 CYP2C9*2*3 11 2.7 CYP2C9*3*3 5 1.6 Warfarin and pharmacokinetics

47. Polymorphisms in vitamin K epoxide reductase (VKOR)C1 Associated reductions in warfarin dose Accounts for greater variance in dose than CYP2C9 Variation in genes encoding γ-glutamylcarboxylase and factors II, VII and X Warfarin and pharmacodynamics

48. 55% Age: p<0.0001, r2 = 0.10 Body weight: p=0.0018, r2 = 0.05 Genetic and Environmental Factors and Dose Requirements of Warfarin Independent effects of VKORC1 and CYP2C9: VKORC1: p<0.0001, r2 = 0.29 CYP2C9: p=0.0003, r2 = 0.11 Wadelius et al. 2005

49. Warfarin: multiple genes/factors GENETIC • Cytochrome P450 polymorphisms • Vitamin K epoxide reductase • Phase II metabolising genes • Drug transporters • Clotting factors • Disease genes ENVIRONMENTAL • Sex • Age • Smoking • Interacting drugs • Alcohol • Compliance • Diet