IT HAS DETAILED EXPLANATION ABOUT PHARMACOGENETICS AND GENOMICS AND THEIR USES IN PRESENT TRENDS

1. 1

2. PHARMACOGENETICS
Dr.
Mahendranath
,
PG 1st year, 2

3. INDEX
1. INTRODUCTION.
2. HISTORY OF PHARMACOGENETICS
3. PHARMACOGENETICS,PHARMACOGENOMICS
&’PERSONALISED MEDICINE.’
4. FACTORS FOR VARIATION IN DRUG RESPONSE
5. PRINCIPLES OF PHARMACOGENETICS
6. TYPES OF PHARMACOGENETIC VARIATIONS
7. PHARMACOGENETICS IN PRACTICE
8. REFERENCE
9. CONCLUSION 3

4. PHARMACOGENETICS :-
 Is the study of inherited genetic differences in
drug metabolic pathways which can affect individual
responses to drugs both in terms of therapeutic effect as
well as adverse effects.
 Genetic differences in a SINGLE gene.
E.g.: peripheral neuritis in slow acetylators and
hepatotoxicity in fast acetylators who are under ISONIAZID
treatment.
4

5. PHARMACOGENOMICS:
- Study of the role of the genome in drug response.
 It analyzes how the genetic makeup of an
individual affects response to drugs.
 It is useful to choose a particular drug to the
responders and avoid unnecessary usage of drugs
in non responders and avoid using in persons with
adverse drug reactions.
 So it is useful in tailoring the drug therapy on the
basis of individual genotype
5

6. PHARMACOGENOMICS
6

7. 7

8. HISTORY
8
The history of pharmacogenetics stretches as far back as
510 B.C. when PYTHAGORAS noted that ingestion of
FAVA BEANS resulted in a potentially fatal reaction
(Hemolytic Anemia and oxidative stress) in some, but not
all, individuals.
Interestingly, this identification was later validated and
attributed to deficiency of 6GDP in the 1950s and called
favism.

9. HISTORY OF PHARMACOGENETICS
 FREDRICH VOGEL 
Word PHARMACOGENETICS coined (at first In 1959)
In 1964 he established the journal HUMAN GENETICS
 SIR ARCHIBALD GARROD 
The role of genetics in response to Drugs.
He wrote book The Incidence of Alkaptonuria.
GARRODS TETRAD- ALKAPTONURIA
INBORN ERRORS OF ALBINISM
METABOLISM CYSTINURIA
PENTOSURIA.
9

10. Time line of genomic discoveries
10

11. (1950 - 1990) & (1990 AND THEREAFTER)
• In 1953  watson and crick DNA double helix.
• MOTULSKY drug gene interactions in drug efficacy.
• Chronic myelogenous Leukemia(CML)  Its association with chromosomal
defects (Philadelphia chromosome) in 1960 by PETER NOWELL & JENET
ROWLEY in university of pennsylvania.
• In 1961 EVANS and CLARKE published 1st paper on pharmacogenetics.
• The inheritance pattern of responses to some of the drugs were found
during this period.
• Until 1990, about100 of properties polymorphic and monomorphic
pharmacogenetics were identified. 11

12. History ofpharmacogenetics
 N- acetyltransferase polymorphism  Racial distribution and
depends on the latitude of countries.
 Polymorphism discovery in hemoglobin  Sickle cell disease
 the SNP of HFE gene  hemochromatosis
 Apolipoprotein E=ApoE  Cardiovascular and Alzheimer's disease,
 Factor’s gene 5 and prothrombin gene  thrombosis
 Methylene Tetra Hydro Folate Reductase=(MTHFR)  Venous
thromboembolism
12

13. Factors contributing to variation in
drug response
• Diet
• Age
• Gender
• Lifestyle
• Circadian &
seasonal variation
• Exercise
• Comorbidities
• Renal and
hepatic
• Genetic factors
13

14.  Human genome has 30,000 genes.
 Each gene has several thousands of nucleotides.
 Each person inherits 2 copies of genes one from each
parent.
 Any two individuals DNA is 99.9% identical
 3 billion nucleotides.
 Variation is seen in >1% of population called
polymorphism
 Of that most common is SNP
BASICS IN GENETICS
Between 2 people (except identical twins) the rate of
genetic variation (individuality) is about 0.1%
[0.1% of 3 billion = 3 million base pair differences]
14

15. 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
15

16. Mutation: difference in the DNA code that occurs in
less than 1% of population
› Often associated with rare diseases
Cystic fibrosis, Albinism,
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
16

17. GENETICPOLYMORPHISMS
Single nucleotide
(polymorphisms (SNPs)
•Coding, nonsynonymous
C C G – Pro
C A G – Gln
•Coding, synonymous
CCG – Pro
CCA – Pro
•Non coding
•Promoter/intronic
•Transcript stability/splicing
Indels (smaller)
• Insertions/deletions
• Tandem repeats
 Copy number variations(larger)
• Gene duplications
• Large deletions
17

18. SNPs
18
A single nucleotide polymorphism (SNP), is a variation in a single
nucleotide that occurs at a specific position in the
genome, where each variation is present to some appreciable degree within
a population (e.g. >1%).
75
%
23
%
2%
*

19. SNPs types
19
SNPs usually occur in non-coding regions
more frequently than in coding regions.
Non-coding SNPs in promoters/enhancers are
in 5′ and 3′ untranslated regions may affect
gene transcription/gene splicing.
for example, a common genetic variant due to an SNP in one of the coagulation
factors, known as factor V Leiden, is the commonest form of inherited thrombophilia.

20. 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
20

21. GENETIC POLYMORPHISM BASED ON DRUG METABOLIZING ABILITY
PHENOTYPE GENOTYPE EFFECTS
A. extensive or normal
drug metabolizers(EM)
(75 –85%)
homozygousor
heterozygous for wildtype
allele.
Normal metabolism.No
dosemodification needed.
B.intermediate metabolizer
phenotype (IM) (10 -
15%)
heterozygous for thewild
type allele
mayrequire lowerthan
averagedrug dose for
optimal therapeutic
response.
C.poor metabolizers (PM)
(5 –10%)
mutation or deletionof
both alleles
accumulation of drug
substrates in their systems
with toxic effects.
D.ultrarapid metabolizers
(UM) (2 –7%)
gene amplification
/gene duplication.
drug failure
21

22. DRUG
TARGETS
DRUG
TRANSPORTERS
DRUG
METABOLIZING
ENZYMES
PHARMACOKINETICSPHARMACODYNAMICS
Variability in
Efficacy/Toxicity
•Transporters
•Plasma protein binding
•Metabolising enzymes
•Receptors
•Ion channels
•Enzymes
•Immune molecules
22

23. Polymorphisms
Drug metabolism
Adverse Drug
Reaction
Disease
susceptibility
Receptor
sensitivity
Drug transport
Responders/
Non-responders
Consequences of polymorphisms
23

24. PHARMACOKINETIC VARIATIONS
OXIDATION
ACETYLATION
SUCCINYLCHOLINE HYDROLYSIS
AMINOGLYCOSIDE OTOTOXICITY
24

25. OXIDATION (phase 1):-
 most of drugs are lipophilic compounds
eliminated by oxidation catalyzed by
cytochrome p 450 enzyme present in liver.
 Total number of cyp450 genes in human
consist of 57 CYP genes and 29 pseudo genes.
 95% of all drug oxidation occurs in 5 CYP
enzymes.
25

26. http://www.doctorfungus.org/t
hedrugs/images/antifung_2.gif
26

27. DRUG METABOLIZING ENZYMES
Phase I: biotransformation reactions: oxidation, hydroxylation, reduction, hydrolysis
Phase II: conjugation reactions—to increase their water solubility and elimination from the
body. Thereactions are glucuronidation, sulation,acetylation, glutathione conjugation 27

28. 1A2
19%
2D6
3%
2E1
10%
3A4/5
42%
2C9
2C19
26%
2D6
24%
2E1
1%
3A4/5
51%
2C9
2C19
19%
Primary CYP Enzymes in Drug Metabolism
% of total enzyme % of drugs metabolised
1A2
5%
28

29. CYP2D6
29
 Source of sparteine / debrisoquine oxidation polymorphism
 7-9 % caucasian population referred as poor metabolizers
 They don’t express the enzyme they have mutation on the
long arm of chromosome 22.
 CYP2D6 show marked allelic heterogenecity
 80 known variants of SNP are reported.
 It oxidizes tricyclic antidepressants , antipsychotics ,SSRI,
antiarrhythmics, beta adrenoreceptor blockers,phenformin
and opiates.
 Poor hydroxylators have dose related toxicity like
Lactic acidosis with phenformin,CNS toxicity with nortriptyline
 Extensive metabolizers have duplication of CYP2D6 allele
and have therapeutic failure.
 AR

30. 30

31. • CYP2D6:-
-Tricyclic antidepressants
• Poor metabolisers – high plasma concentration – toxic
effects(tardive dyskinesia)
• Rapid metabolisers – low plasma concentrations –
therapeutic failure
– Codeine (as analgesic)
• Poor metabolisers – therapeutic failure
• Rapid metabolisers - toxic effects of morphine is
seen. 31

32. 32

33. CYP2C19
 MEDIATOR OF BIOTRANSFORMATION OF TERITIARY AMINE
TRICYCLIC ANTIDEPRESSANTS
 METABOLIZES MEPHENYTOIN,PPI,CLOPIDOGRIL,BIOACTIVATION OF
PROGUANIL,DIAZEPAM.
 3-5% EUROPEANS AND 15-20 % ASIANS ARE POOR METABOLIZERS.
 POOR METABOLIZERS:-
 CLOPIDOGRIL IS IN INACTIVE FORM(15%)
 OMEPRAZOLE HAS 100% CURE RATE
 FAILURE OF PROGUANIL METABOLISM TO CYCLOGUANIL
SO LOSS OF PROTECTION FROM MALARIA.
 IMPAIRED MEPHENYTOIN METABOLISM 33

34. CYP2C19
34

35. CYP2C9
35
Major enzyme catalyzing the biotransformation of warfarin,
phenytoin, fluvastatin and several NSAIDS,tolbutamide and other
oral antidiabetic drugs.
patients with either “CYP2C9*2 or
CYP2C9*2 variant require lower
warfarin maintenance dose” .
The risk for bleeding doubled in
these patients, as they metabolize
warfarin slower than the wild-type
patient.

36. 36

37. CYP450
gene
MutantAlleles 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
37

38. ACETYLATION
• Several drugs acetylated by hepatic NAT2 of the enzyme
N-acetyltransferase.
• The difference between fast and slow acetylators depends on the
amount of hepatic N-acetyltransferase.
• Fast acetylators are autosomal dominant slow are recessive
• Drugs that undergo acetylation are isoniazid, hydralazine,
procainamide,phenelzine,dapsone,sulfamethoxypyradizine
• In slow acetylators there is enhanced response to treatment but
increased drug toxicity.
• Hence slow acetylators require lower doses. 38

39. Pharmacogenetic variations.
 Acetylation
• Polymorphism of N-acetyltransferase
Acetylation of Isoniazid
Fast acetylators
High N-acetylase
Eskimos,japanese
hepatotoxicity
slow acetylators
Low N-acetylase
Egyptians,swedes,
mediterranian jews
peripheral neuropathy
So pyridoxine(vit B6) is added with isoniazid Therapy
39

40. Succinylcholine hydrolysis
Psuedocholinest
Succinylcholine
Atypical Psuedocholinesterase
Sleep apnoea
Doesn’t metabolize succinylcholine rapidly so levels of
succinylcholine and Continue to produce neuromuscular blockade for
several hours.
Results in respiratory paralysis need prolonged ventilation.
40

41. Gene MutantAlleles 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
41

42. Gene product Drugs Responses affected
CYP2C9
Warfarin, Tolbutamide, Phenytoin,
NSAIDs
Anticoagulant effect of warfarin
CYP2C19
Omeprazole, clopidogrel,
mephenytoin, propranolol
Peptic ulcer response to
omeprazole, Cardio-vascular
events after clopidogrel
CYP2D6
Beta blockers, codeine,
antidepressants, tamoxifen
antipsychotics, debrisoquine,
Codeine efficacy,
Tardive dyskinesia from
antipsychotics
CYP3A4/A5/A7
Macrolides, cyclosporine,
tacrolimus, CCBs,etc
Efficacy of immunosuppressive
effect of tacrolimus
UGT1A1(UDP
glucuronos
yl
transferase)
Irinotecan,bilirubin Irinotecan toxicity
Thiopurine methyl
transferase(TPMT)
Mercaptopurine, thioguanine,
azathioprine
Thiopurine toxicity andefficacy
Dihydropyramidine
dehydrogenase
Fluorouracil, capacitabine 5-fluorouracil toxicity 42

43. PHARMACOGENETIC VARIATION IN DRUG RESPONSE DUE TO ENZYME
DEFICIENCY: RED CELL ENZYME DEFECT.
 Glucose – 6 – phosphate dehydrogenase deficiency(G-6-PD) :
 Deficiency in RBC’s
 Sex – linked recessive trait( X – linked)
 Africans,American negroes, Mediterranean Jews, middle east and south east
races.
 Drugs having oxidising properties can cause haemolytic anaemia in persons
having G-6-PD deficiency.
 Reduced NADPH production & glutathione accumulates.
Eg: Primaquine, Sulphonamides, Dapsone, Nitrofurantoin, Quinine, Chloroquine,
Quinidine, nalidixic acid, doxorubicin.
HEINZ BODIES IN BLOOD FILM.
43

44. GLUTATHIONE REDUCTASE DEFICIENCY
• Autosomal dominant.
• Directly cause a deficiency of reduced glutathione
and hemolysis will result from effects of oxidizing agents
METHAEMOGLOBIN REDUCTASE DEFICIENCY
• In normal individuals methaemoglobin is reduced to haemoglobin.
• In methaemoglobin reductase deficiency, methaemoglobin is
accumulated and causes impairement of oxygen delivery to the
tissues and causes hypoxaemia
• On exposure to oxidant drugs the condition worsens.
44

45. 45

46.  Porphyria is due to enzymatic abnormality in haem biosynthetic
pathway.
 In acute intermittent porphyria basic defect is in the gene HMBS for
enzyme porphobilinogen deaminase,which catalyses the production
of porphyrins, the precursor of haem.
 The reduction in haem synthesis switches ALA SYNTHASE,with excess
production of ALA ,porphobilinogen and its metabolite causing
ACUTE INTERMITTENT PORPHYRIA.
 Drugs that induce CYP 450 precipitate porphyria
 CYP 450 is a haeme containing enzyme, induction of CYP450
demands more haem production exaggerating ALA synthase
response and overproduction of porphobilinogen and its metabolite
products.
 Drugs that are unsafe in porphyria are
barbiturates,carbamazepine,phenytoin,isoniazid,dapsone,diclofenac.
ACUTE INTERMITTENT PORPHYRIA
46

47. • Management of acute attack of porphyria:
 No specific measures
 High intake of carbohydrates inhibits ALA synthase activity and a
high carbohydrate diet will not do any harm.
 Hematin(Hemin) IV 3-4mg /kg/day for 3-4 days has been used as a
specific therapy.
47

48. 48

49. MALIGNANT HYPERTHERMIA
• Fatal complication of general anaesthetics with haolthane,
methoxyflurane, succinylcholine.
• RYNODINE RECEPTOR mutation in sarcoplasmic reticulum.
• Excessive release of calcium into cytoplasm trigerred by anaesthetics.
• AD.
• CLINICAL FEATURES:-
• ACUTE RISE IN TEMPERATURE
• MUSCLE STIFFNESS
• TACHYCARDIA & TACHYPNOEA
• SWEATING,CYANOSIS.
49

50.  streptomycin and gentamicin are primarily vestibulotoxic, whereas
amikacin, neomycin, dihydrosterptomycin, and kanamicin are
primarily cochleotoxic.
 Cochlear damage can produce permanent hearing loss, and damage
to the vestibular apparatus results in dizziness, ataxia, and/or
nystagmus.
 Aminoglycosides appear to generate free radicals within the inner
ear, with subsequent permanent damage to sensory cells and
neurons, resulting in permanent hearing loss.
 Two mutations in the mitochondrial 12S ribosomal RNA gene have
been previously reported to predispose carriers to aminoglycoside-
induced ototoxicity.
 As aminoglycosides are indispensable agents both in the treatment of
infections and Meniere's disease, a great effort has been made to
develop strategies to prevent aminoglycoside ototoxicity.
 Anti-free radical agents, such as salicylate, have been shown to
attenuate the ototoxic effects of aminoglycosides.
AMINOGLYCOSIDE OTOTOXICITY
50

51. INSULIN RESISTANCE
Different mutations in the insulin receptors alpha subunit were
proposed in Different families ( Ark-i, Atl, Minn.)
Based on phenotype, cellular insulin binding and insulin receptor
structure.
Arrhythmogenic effects of antiarrhythmic drugs
• Torsade de pointes is associated with long QT syndrome.
• AD.
• Drugs like clarythromycin,levofloxicin,haloperidol with are QT
prolonging medications when given with cyp450 inhibitors like
FLUOXETINE, CIMITIDINE and also grape fruit.
• Genetic abnormality in potassium channel function has been
attributed to torsade de pointes.
51

52. RESISTANCE TO DRUG EFFECTS
VITAMIN D RESISTANT RICKETS:-
There are 3 varieties of rickets that
are resistant to effects of vitamin D.
1) FAMILIAL HYPOPHOSPHATAMIC RICKETS:
impaired phosphate reabsorption in the kidney.
2) TYPE II VITAMIN D DEPENDENT RICKETS:
impaired tissue sensitivity to vitamin D
and decreased receptor binding.
3) RICKETS IN FANCONI SYNDROME:
failure in tubular reabsorption of phosphate
52

53. http://mostgene.org/2009_conference/personalized_meds_Gettig.pdf
53

54. Clinically available
Pharmacogenomic tests
54
54

55. 1) HLA GENE TESTS:-
a) ABACAVIR & HLAB*5701
b) ANTICONVULSANTS & HLAB*1502
c) CLOZAPINE & HLA-DQ 1*0201
2) DRUG METABOLISM RELATED GENE TEST:-
a) THIOPURINE & TPMT
b) 5-FLUOROURACIL (5-FU) & DPYD
c) TAMOXIFEN & CYP2D6
d) IRINOTECAN & UGT1A1*28
Various type of tests
55
55

56. 3) DRUG TARGET RELATED GENE TEST
a) Trastuzumab & HER 2
b) DASATINIB, IMATINIB & BCR-ABL 1
4) COMBINED (METABOLISM & TARGET) GENE TEST
a) WARFARIN & CYP2C9 + VKORC 1
GENOTYPING
56
56

57. IDIOSYNCRATIC
1. ABACAVIR AND HLAB*5701: severe rashes.
2. ANTICONVULSANTS & HLAB*1502:
severe life-threatening rashes including Stevens
Johnson syndrome and toxic epidermal necrolysis
3. CLOZAPINE AND HLA DQB1*0201:
agranulocytosis.
57

58. • DRUG METABOLISM RELATED GENE TESTS.
• Fluorouracil is a chemotherapy agent that belongs to the drug class
of fluoropyrimidines.(CAPECITABINE & TEGAFUR)
• Fluorouracil is used in the palliative management of carcinoma of
the colon, rectum, breast, stomach, and pancreas.
• The DPYD gene encodes dihydropyrimidine dehydrogenase (DPD),
an enzyme that catalyzes the rate-limiting step in fluorouracil
metabolism.
• Individuals who carry at least one copy of non
function DPYD variants, such as DPYD*2A, may not be able to
metabolize fluorouracil at normal rates, and are at risk of potentially
life-threatening fluorouracil toxicity, such as bone marrow
suppression and neurotoxicity.
• The prevalence of DPD deficiency in Caucasians is approximately
3%-5%.
• The FDA-approved drug label for fluorouracil states that “rarely,
unexpected, severe toxicity associated with 5-fluorouracil has been
attributed to deficiency of dipyrimidine dehydrogenase activity”.58

59.  The FDA also states that fluorouracil therapy should be discontinued promptly
whenever one of the following signs of toxicity appears:
 Stomatitis or esophageal pharyngitis at the first visible sign,
 Leukopenia (WBC under 3500) or a rapidly falling white blood count,
 Vomiting,
 intractable Diarrhea,
 frequent bowel movements, or watery stools
 Gastrointestinal ulceration and bleeding
 Thrombocytopenia (platelets under 100,000)
 Hemorrhage from any site
TOXICITY
59

60. Likely phenotype Functional definition Genetic definition Example diplotypes
Normal metabolizer Fully functional DPD
enzyme activity
Combinations of
normal function and
decreased function
alleles
DPYD*1/*1
Intermediate
metabolizer
(~3–5% of patients)
Decreased DPD
enzyme activity
(activity between
normal and poor
metabolizer)
Combinations of
normal function,
decreased function,
and/or no function
alleles
*1/*2A; *1/*13; or
*1/rs67376798
Poor metabolizer
(~0.2% of patients)
Little to no DPD
enzyme activity
Combination of no
function alleles and/
or decreased function
alleles
*2A/*2A;
13/*13; *2/*13;
or rs67376798/ rs673
76798
60

61.  The TPMT gene encodes enzyme thiopurine S-methyltransferase.
 TPMT is one of the main enzymes involved in the metabolism of
thiopurines, such as azathioprine,6 mercaptopurine, 6 thiogunanine.
 TPMT activity is inherited as a co-dominant trait, as the TPMT gene is
highly polymorphic with over 40 reported variant alleles.
 The wild-type TPMT*1 allele is associated with normal enzyme
activity. Individuals who are homozygous for TPMT*1 (TPMT normal
metabolizers) are more likely to have a typical response to
azathioprine and a lower risk of myelosuppression. This accounts for
the majority of patients (~86–97%).
 Individuals who are TPMT poor (approximately 0.3%) or intermediate
(approximately 3–14%) metabolizers carry variant TPMT alleles that
encode reduced or absent enzyme activity.
 Incresed levels of active metabolite Thioguanine nucleotide and
causes myelosuppression and hepatotoxicity
THIOPURINE AND TPMT POLYMORPHISM
61

62. Phenotype Phenotype details TPMT
Genotype
Examples of diplotypes Therapeutic recommendations
for azathioprine
Homozygous wild-type
(“normal”)
High enzyme activity.
Found in ~86–97% of patients.
Two or more
functional TPMT alleles
*1/*1 Start with normal starting dose
(e.g., 2–3 mg/kg/d) and adjust
doses of azathioprine based on
disease-specific guidelines.
Allow 2 weeks to reach steady
state after each dose
adjustment.
Heterozygous Intermediate enzyme activity.
Found in ~3–14% of patients.
One functional TPMT allele
plus one
nonfunctional TPMT allele
*1/*2
*1/*3A
*1/*3B
*1/*3C
*1/*4
If disease treatment normally
starts at the “full dose”,
consider starting at 30–70% of
target dose (e.g., 1–1.5
mg/kg/d), and titrate based on
tolerance.
Allow 2–4 weeks to reach
steady state after each dose
adjustment.
Homozygous variant Low or deficient enzyme
activity.
Found in ~1 in 178 to 1~3736
patients.
Two
nonfunctional TPMT alleles
*3A/*3A
*2/*3A
*3C/*3A
*3C/*4
*3C/*2
*3A/*4
Consider alternative agents. If
using azathioprine start with
drastically reduced doses
(reduce daily dose by 10-fold
and dose thrice weekly instead
of daily) and adjust doses of
azathioprine based on degree
of myelosuppression and
disease-specific guidelines.
Allow 4–6 weeks to reach
steady state after each dose
adjustment.
Azathioprine is the likely cause
of myelosuppression.
62

63. Case study
• A 72 year old male with metastatic
colorectal cancer was prescribed an
anticancer drug Irinotican 180mg/m2, as
an intravenous infusion, which was
repeated every 2weeks, along with
several other chemotherapeutic agents.
• Liver function and renal function were
normal.
• Blood samples were drawn.
63

64. • After the treatment cycle, the patient
experienced very severe neutropenia and
diarrhea.
• Plasma levels of SN-38, the active metabolite
of irinotecan, were 4fould higher than those
found in most patients.
• The irinotecan dose was reduced by 50%.
• Plasma levels of SN-38 were lower but still
more than twice normal.
• However after 2nd cycle, there was no
neutropenia and only grade 1 diarrhea.
• CT and MRI scan showed partial response
to the chemotherapy. 64

65. Case study answer
• Irinotecan is metabolized to the active cytotoxic
molecule SN-38, which is also responsible for
toxicity.
• Inactivation of SN-38 occurs via the
polymorphic UGT1A1 enzyme.
• Carriers of the UGT1A1*28 variant have
reduced enzyme activity.
• SN-38 G is inactive form 65

66. 66

67. Denomination Variants14 Allele frequency
(ethnicity)15,16
Expression level Enzymatic activity Clinical
consequence
UGT1A1*1 (TA)6TA Common allele 100% 100% None
TATA box polymorphisms
UGT1A1*28 c.–39_–40 ins
TA: (TA)7TA
29–45%
(Caucasians); 42–
51% (Africans);
16% (Asians)
Reduced Reduced Gilbert’s syndrome,
Crigler–Najjar
syndrome17
Polymorphisms in the promoter region
UGT1A1*60 c.–3279 T>G 23–39%
(Caucasian); 15%
(African
Americans); 17%
(Asians)
Reduced Unchanged Gilbert’s syndrome,
Crigler–Najjar
syndrome18
Polymorphisms in exon 1
UGT1A1*6 c.211 G>A
p.Gly71Arg
15–20% (Asians) Unchanged Reduced Gilbert’s syndrome,
Crigler–Najjar
syndrome19
UGT1A1*27 c.686 C>A
p.Pro229Gln
5–28% (Asians) Unchanged Reduced Gilbert’s syndrome,
Crigler–Najjar
syndrome19
67

68. • The cytochrome P450 2D6 (CYP2D6) is an enzyme known to
metabolize drugs.
• Genetic polymorphisms have been grouped as nonfunctional,
reduced function, functional, and multiplication alleles.
• Individuals carrying these alleles are presumed to correspond to
poor, intermediate, extensive, and ultrarapid metabolizers (UM),
respectively.
• Tamoxifen has been shown to be metabolized by CYP2D6 to the
more potent metabolite endoxifen.
• Poor metabolizers (PM) of tamoxifen have lower levels of endoxifen
and poorer clinical outcomes as compared to extensive metabolizers.
DRUG METABOLISM RELATED GENE TESTING
68

69. B.DRUG TARGETS
• The action of HALOPERIDOL depends on its ability to bind to the
DOPAMINE d2 Receptor site.
• 63% population who has large number of dopamine receptor shows
better response with haloperidol.
• When HER2 gene is over expressed in breast tissue extra protein
receptors are produced on the cell surface
• They trigger the cell to grow and divide out of control and becomes
cancerous.
• 20-30% breast cancer women express HER2 protein .
• TRASTUZUMAB works by binding to the receptor site on the cell
surface thereby limiting cell proliferation and prevent cancer to grow.69

70. • Dasatinib is a dual BCR/ABL and Src tyrosine kinase
inhibitor used in haematological malignancies
characterised by the presence of a Philadelphia
chromosome, namely chronic myeloid leukaemia (CML)
and some adults with acute lymphoblastic leukaemia
(ALL).
• The Philadelphia chromosome results from a
translocation defect btwn (9 and 22) swap places; part of a
‘breakpoint cluster region’ (BCR) in chromosome 22 links
to the ‘Abelson-1’ (ABL) region of chromosome 9. A
mutation (T315I) in BCR/ABL confers resistance to the
inhibitory effect of dasatinib and patients with this
variant do not benefit from this drug.
• Pharmacogenetic testing is also being evaluated for
imatinib associated with rearrangements in the gene for
platelet-derived growth factor receptor or for BCR-ABL.
DASATINIB/IMATINIB and BCR-ABL-1
70

71. • Warfarin (brand name Coumadin) is an anticoagulant (blood
thinner).
• Warfarin acts by inhibiting the synthesis of vitamin K-dependent
clotting factors and is used in the prevention and treatment of
various thrombotic disorders.
• Warfarin is a drug with narrow therapeutic index; thus, a small
change in its plasma levels may result in concentration dependent
adverse drug reactions or therapeutic failure.
• Therefore, the dose of warfarin must be tailored for each patient
according to the patient’s response, measured as INR (International
Normalized Ratio), and the condition being treated.
• Values of INR in normal individual < 1, 2-3 in patients on warfarin.
• If INR is high risk of bleeding
• If INR is low risk of thrombosis.
WARFARIN VKORC1 & CYP2C9 POLYMORPHISM
71

72. Phenotype/diplotype Recommendation
CYP2C9 IM Use 65% of the standard initial dose
CYP2C9 PM Use 20% of the standard initial dose
CYP2C9*1/*2 No action is required for this gene-drug
interaction.
CYP2C9*1/*3 Use 65% of the standard initial dose
CYP2C9*2/*2 Use 65% of the standard initial dose
CYP2C9*2/*3 Use 45% of the standard initial dose
CYP2C9*3/*3 Use 20% of the standard initial dose
VKORC1 C/T No action is required for this gene-drug
interaction
VKORC1 T/T Use 60% of the standard initial dose
72

73. P G S
H E C
A N R
R E E
M T E
A I N
C C I
O N
G
73

74. PHARMACOGENITIC SCREENING TESTS
AmpliChipCYP450
Detects polymorphism in drugmetabolizing
enzymes(DMEs) such as CYP2D6,CYP2C19
Affymetrix DMET
Detects polymorphism in DMEs – CYP1A2,
CYP2C9,CYP2C19,CYP2D6, CYP3A4A5 & A7and
transporters
PHARMAChip
Detects polymorphisms in CYP450enzymesandin
genes that code for drug receptors, transporters
and othertargets
TherascreenKit Foruse ofafatinib in non-small-cell lung cancer
Cobas EGFRMutation Test
Foruse of erlotinibin non-small-celllung cancer
74

75. AMPLICHIP
75
•Determine the genotype of the
patient in terms of two CYP450
enzymes: 2D6 and 2C19
•FDA approved the test on Dec 24, 2004.
The Amplichip CYP450 test is the first
FDA approved pharmacogenetic test.
75

76. 76

77. 77

78. 78

79. DNA Test in India DNA Test Cost in India
Paternity DNA Test Price (Father
+ 1 Child) in India
₹ 13,382
Paternity DNA Test Price (Father
+ 2 Children) in India
₹ 19,823
Maternity DNA Test Price
(Mother + 1 Child) in India
₹ 13,382
COST OF TEST IN INDIA
79

80. METHODOLOGY
80
WBCs/ Buccal cells
*PharmGKB
80

81. Pharmacogenetics
& Drug development
81
81

82. 82
GOALS OF PHARMACOGENETICS

83. Potential Benefits of Pharmacogenetics
• Improve Drug Choices:
– Each year, ~100,0000 people die of adverse reactions
to medicine & ~2 million are hospitalized
– Pharmacogenitics will predict who's likely to have a
negative or positive reaction to a drug
• Safer Dosing Options
– Testing of Genomic Variation Improve Determination
of Correct Dose for Each Individual
83

84. • Improvement in Drug Development:
– Permit pharmaceutical companies to determine in which
populations new drugs will be effective
• Decrease Health Care Costs
– Reduce number of deaths & hospitalizations due to
adverse
drug
reactions
– Reduce purchase of drugs which are ineffective in
certain individuals due to genetic variations
• Speed Up Clinical Trials for New Drugs
Potential Benefits of Pharmacogenetics
84

85. Barriers of Pharmacogenomics
42
1. Complexity of finding gene variations that
affect drug response.
Millions of SNPs must be identified and
analyzed to determine their involvement in
drug response
2. Confidentiality, privacy and the use and
storage of genetic information

86. Barriers of Pharmacogenomics...
• 3. Educating healthcare providers and patients
Complicates the process of prescribing and
dispensing drugs
Physicians must execute an extra diagnostic
step to determine which drug is best suited
to each patient
43

87. Barriers of Pharmacogenomics..
44
4. Disincentives for drug companies to
make multiple pharmacogenomic
products
Most pharmaceutical companies have been
successful with their “one size fits all”
approach to drug development
For small market- Pharmaceutical
companies hundreds of millions of
dollars on pharmacogenomic based drug
development.

88. Understanding human
genome
Simpler methods
identify genetic
information
Genetic information
specific to individual
Preselect
effective drug
PERSONALIZED MEDICINE
No
toxicity
Notrial
& error
88

89. 89

90. Personalized
medicine
S M A R T C A R D
Person’s name
GENOME
(Confidential)
“Here is my
sequence”
90

91. The Goal of Personalized Medicine
The Right Dose of
The Right Drug for
The Right Indication for
The Right Patient at
The Right Time.
91

92. Clinomics
47
Clinomics is the study of genomics
data along with its associated clinical
data.
As personalized medicine advances,
clinomics will be a bridge between basic
biological data and its effect on human
health.

93. Scope of Pharmacogenomics
49
93

94. Drug development and approval
In vitro
studies
Preclinical testing
Animal
testing
Clinical trials
Average years
1 to 5 years 2 to 10 years 1 year
IND
NDA
Post-
marketing
surveillance
(Phase 4)
Phase 1 – normal volunteers: safety,
pharmacokinetics
Phase 2 – selected patients:
therapeutic efficacy, dose range
Phase 3 – large populations of
selected patients: therapeutic
efficacy, safety in double blind
studies
Long-term
toxicity studies
94

95. • › 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
Publicly accessible knowledge base
KNOWLEDGE BASE
95

96. 50

97. BIBLIOGRAPHY
1. THE PHARMACOLOGICAL BASIS OF
THERAPEUTICS ,GOODMAN & GILMAN,12TH
EDITION,2011,PAGE 145-165.
2. RANG & DALE’S PHARMACOLOGY,7TH
EDITION,2012,PAGE 132-137.
3. POSTGRADUATE TOPICS IN
PHARMACOLOGY,RITUPARNA MAITI PAGE
193-202.
97

98. • Pharmacogenomics has great potential to optimize
drug therapy.
• Newer molecular diagnostic test will have to be
develop to detect polymorphisms.
• Pharmacotherapeutics decisions will soon become
fundamental for diagnosing the illness & guiding the
choice & dosage of medications.
CONCLUSION
48
98

99. 99