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Pharmacogenomics-based individualization of drug therapy

Taisei Mushiroda, Ph.D.

Laboratory for Pharmacogenetics

Center for Genomic Medicine, RIKEN

ETH Zurich-JST Workshop on Medical Research, 15 Sep 2008

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Center for Genomic Medicine (CGM), RIKENProf. Yusuke

Nakamura

Director

Research Group for Genotyping

Research Group for Disease-Causing Mechanism

Research Group for Medical Informatics

Research Group for Pharmacogenomics

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Response rates of patients to a major drug:Physician's Desk Reference (2000)

Spear et al. TRENDS in Molecular Medicine 7：201-4 (2001)

0 20 40 60 80 100 (%)Analgesics (COX-2)

Depression (SSRI)Asthma

Cardiac arrhythmiasSchizophrenia

DiabetesMigraine (acute)

Rheumatoid arthritisMigraine (prophylaxis)

Osteoporosis HCV

IncontinenceAlzheimer’s

Oncology

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Individualization of drug therapyin personalized medicine

● To identify✓ Responders / non-responders to a drug✓ Patients with higher risk of adverse drug reactions (ADRs) before the administration

“Right drug at the appropriate dosage for each individual patient”

Effective Not effective

Drug A：

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Pharmacogenomics (PGx): ICH Guideline E15

● Study of variations of DNA and RNA characteristics

as related to drug response

● Applicable to activities such as drug discovery,

drug development, and clinical practice

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Application of PGx to personalized medicine

1. Avoid severe adverse drug reactions

✓ Docetaxel (anti-cancer reagent)

2. Predict efficacy

✓ Tamoxifen (treatment for breast cancer)

3. Predict appropriate dosage for each patient

✓ Warfarin (anti-coagulant)

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Docetacel (Taxotere®)

● Microtubule inhibitor

● Approved for treatment of patients with refractory

breast cancer, non-small-cell lung cancer, ovarian

cancer, and head and neck cancer

● Severe myelosuppression (leucopenia / neutropenia):

Frequency of ~36%

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Systemic circulation

Hepatic artery

Hepatic vein Docetaxel

Liver

Bile duct Excretion

Transporters responsible for biliary excretion of docetaxel

Blood

SLCO1B3

Hepatocyte

ABCC2

Bile duct

Hepatocyte

Docetaxel

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P valueABCC2 GG + GC CC GG + GC CC(rs12762549) 24 15 66 8 0.00080

(62%) (38%) (89%) (11%)

SLCO1B3 AA AG + GG AA AG + GG(rs11045585) 20 19 63 11 0.00017

(51%) (49%) (85%) (15%)

ADR (n =39) Non-ADR (n = 74)

SNPs in ABCC2 and SLCO1B3 were associated with docetaxel-induced

myelosupression

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Scoring

11 12 22SLCO1B3 rs11045585 0 1 1ABCC2 rs12762549 100

GenotypeSNP IDGene

Non-risk

ADR(n = 39)

Non-ADR(n = 74)

0

1

2

Sum

of s

core

7

20

12

1

17

56

39

288

605

Normal control(n = 932)

OR = 7.00, P = 0.0000057

Prediction system for docetaxel-induced myelosupression using ABCC2 rs12762549

and SLCO1B3 rs11045585

Risk

Usual dosage

Decreasingdosage

Contra-indication

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Tamoxifen (Nolvadex®)

● Widely used for prevention of recurrence for patients

with estrogen receptor-positive breast cancer (adjuvant

hormonal therapy)

● Potent in suppressing estrogen-dependent cell

proliferation

● Oral administration, 20～40 mg/day

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Tamoxifen, antagonist for estrogen receptor

Ovary

Breastcancer

Estrogen

Adrenal

Androgen

EstrogenAromatase

Tamoxifen

Premenopausal Postmenopausal Hypophysis

Stimulatinghormone

X X

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Metabolic activation of tamoxifen by CYP2D6

Jin et al. J Natl Cancer Inst 97:30-9 (2005)

CYP2D6

CYP2D6

CYP3A4/5 CYP3A4/5

Tamoxifen

Endoxifen(active)

ON

ON

OH

ONH O

NH

OH

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High frequency of CYP2D6*10 in JapaneseAllele

CYP2D6*1

CYP2D6*3

CYP2D6*4

CYP2D6*5

Normal

None

None

None

Total

Whole deletion

A2549del

G1846A (splicing defect)

0

0.5

6.1

6.6

Allele freq.in Japanese

(homozygote, <1%)

C100T(P34S)

Decreased 40.8CYP2D6*10

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Number of subjects (%)*1/*1 20 (29.9)*1/*4 1 (1.5)*1/*5 4 (6.0)*1/*10 23 (34.3)*5/*10 2 (3.0)*5/*41 1 (1.5)*10/*10 15 (22.4)*10/*21 1 (1.5)

CYP2D6 genotype frequencies in Japanese breast cancer patients treated with tamoxifen

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Effects of CYP2D6*10 on recurrence-free survival of breast cancer patients treated

with tamoxifen

Years

P = 0.00100

0.2

0.4

0.6

0.8

1

0 2 4 6 8 10Years

P = 0.00310

0.2

0.4

0.6

0.8

1

0 2 4 6 8 10

Rec

urre

nce-

free

rat

e

*10/*10 (n=15)

*1/*10 (n=23)

*1/*1 (n=20)

*10/*10 (n=15)

*1/*1+*1/*10(n=43)

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Warfarin (WF)● The most commonly-used oral anticoagulant for treatment of thromboembolism in the world

● Interferes with regeneration of vitamin K→ inhibits activation of vitamin K-dependent clotting factor II (prothrombin), VII, IX and X

● Difficult to adjust the appropriate dose to each patient due to large interindividual variation in dose requirement

Insufficient dose → failure of preventing thrombosisOver-dose → increase of unexpected bleeding risk

● The maintenance dose for Japanese was about 30% lower than those for Caucasian

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Impact of inappropriate dose of WF in USA

2 million people / year start warfarin treatment

Bleeding event:

184,000 people (9%)

Stroke:

40,000 (2%)

Cost: $2.4 billion Cost: $1.6 billion

Cost due to inappropriate dosage:

$4.0 billion / year

McWilliam et al.AEI-Brooking Joint Center，Working Paper (2006)

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0.0 2.0 4.0 6.0 8.0 10.0 12.0Dose (mg/day)

0

25

50

75

100

125

150

No.

of s

ubje

cts

Median: 2.5 mgMinimum: 0.5 mgMaximum: 10.5 mg

Distribution of daily maintenance dose in WF-treated 828 Japanese patients

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Flows of standard WF treatment

Initial dosage:1 mg

INR: Within target range?

Continue the dosage

A few days after

A few days after

Yes No

Increase / decrease / discontinue

INR monitoring

e.g., Prevention of stroke caused by atrial fibrillation in elder patients: 1.6 - 2.6

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Warfarin PGx: CYP2C9 and VKORC1

● CYP2C9

Hepatic drug-metabolizing enzyme of warfarin

● VKORC1

Responsible for recycle of vitamin K in liver

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The vitamin K cycle

Reduced formVitamin K epoxide

Factors II, VII, IX, XProteins C, S, Z

Functional factors

Vitamin K

OHCH3

ROH

O

O

CH3

R

O

O

CH3

RO

Inhibition

O

OH

O

O

H

WF

VKORC1

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Daily WF dose for Japanese patients with different genotypes for CYP2C9

*3/*3(n=1)

*1/*1(n=790)

0

246

810

12

*3/*1(n=37)

P = 3.9 × 10-4

Dos

e (m

g/da

y)

2.0 2.0 2.5

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Daily WF dose for Japanese patients with different genotypes for VKORC1

0

24

6

81012

CC(n=6)

TT(n=690)

Dos

e (m

g/da

y)

CT(n=132)

P = 5.1 × 10-11

4.0 3.52.5

Intron 1-136T>C

Japanese； <1% 16% 84%Caucasian 37% 48% 15%

(Wadelius et al., Pharmacogenomics J, 2005)

25

0

2

4

6

8

1012

Dos

e (m

g/da

y)

TT TT TT CT CT CCVKORC1

*3*3 *3*1 *1*1 *3*1 *1*1 *1*1CYP2C9(n=1) (n=34)(n=655)(n=3)(n=129)(n=6)

Daily WF dose for Japanese patients classified by Warfarin responsive index (WFRI)

TT CT CC0 1 1

*3/*3 *3/*1 *1/*10 0 1

VKORC1

CYP2C9

02

4

6

8

1012

Dos

e (m

g/da

y)

Score 0(n=35)

Score 1(n=658)

Score 2(n=135)

P = 4.4 × 10-13

2.0 2.53.5

Score 0 Score 1 Score 2

1 mg

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Prediction of initial WF dose based on WFRI

Although the dose adjustment with INR is necessary, ….

● Reducing period for achievement of maintenance dose● Avoiding risk of serious bleeding / stroke

GenotypingVKORC1 and CYP2C9

Score 0Started with 2 mg

Score 1With 2.5 mg

Score 2With 3.5 mg

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C 5’3’NInvader probe

T 5’3’NG

Flap 1

Allele probe

VIC

Flap 1

Allele probeG

Cleaved bycleavase

Not cleaved

G

Invader assay

Cleaved bycleavase

3’ FRET probe

QuencherVIC

FAM

3’ FRET probe

AFlap 2

QuencherFAM

Cleaved bycleavase

28Medical treatment support system

Time

SNP1

SNP2

SNP3

Fluo

resc

ence

FAMVIC

Prediction of appropriate dosage by genotyping based on Invader assay

SNP analysis system

Genotype

CC

CT

TT

Patient ID:12345Initial dosage:X mg

Transfer

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Considerations for Increased Bleeding Risk Identification of risk factors for bleeding and certain

genetic variations in CYP2C9 and VKORC1 in a patient may increase the need for more frequent INR monitoring and the use of lower warfarin doses.

Initial DosageThe lower initiation doses should be considered for

patients with certain genetic variations in CYP2C9 and VKORC1 enzymes as well as for elderly and/or debilitated patients and patients with potential to exhibit greater than expected PT/INR responses to COUMADIN.

Updated Warfarin Prescribing Information：August 16, 2007