1

Pharmacogeneticsof Antipsychotic Drug

Response

Anil K. Malhotra, MDThe Zucker Hillside Hospital

Glen Oaks, New YorkThe Albert Einstein College of Medicine

Bronx, New York

2

Dissecting the Heterogeneity of Antipsychotic Drug

Response

• Marked inter-individual variation in response to antipsychotic drugs

• Biologic predictors of drug response (plasma HVA, prolactin, CSF metabolites) have been inconsistent

• Need for molecular correlates of drug efficacy and drug-induced adverse events

• Molecular correlates may suggest new targets for future drug development

3

Pharmacogenetics ofClozapine Response

Candidate Frequency of Association WithReceptor Polymorphism Rare Allele Clozapine Response?

D3 Ser9Gly 35% Yes (Shaikh et al, 1996)1

No (Malhotra et al, 1998)2

D4 16 amino acid repeat multiple alleles No (Rao et al, 1994)3

in exon III

5HT2A His452Tyr 45% Yes (Arranz et al, 1996)4

No (Malhotra et al, 1996)5

T102C 9% No (Malhotra et al, 1996)5

5HT2C Cys23Ser 13% (males) Yes (Sodhi et al, 1995)6

24% (females) No (Malhotra et al, 1996)7

5HTT 20-34 bp repeat in 40% No (Tsai SJ et al, 2000)8

5 regulatory region

1. Shaikh S et al. Hum Genet. 1996;97:714-719; 2. Malhotra AK et al. Mol Psychiatry. 1998;3:72-75; 3. Rao PA et al. Arch Gen Psychiatry. 1994;51:912-917; 4. Arranaz MJ et al. Neurosci Lett. 1996;217:177-178; 5. Malhotra AK et al. Am J Psychiatry. 1996;153:1092-1094; 6. Sodhi MS et al. Neuroreport. 1995;29:169-172; 7. Malhotra AK et al. Neuroreport. 1996;7:2100-2102; 8. Tsai SJ et al. Schizophr Res. 2000;44:177-181;

4

Dopamine D2 Receptor Blockade and Antipsychotic

Potency

Seeman et al 1975

5

5’

1

-141C Ins/Del

2 543 6 8

Taq1 B

7

Ser311Cys

0.91 Kb

0.2 Kb

0.14 Kb

-50 Kb

-10 Kb

25.5 Kb

A-241G

Taq1 D TaqI A

3’

DRD2 (11q22-q23): Candidate Gene for Antipsychotic Drug

Response

6

0

50

100

150

200

250

A-241/-141C Del A-241/-141 Ins0

50

100

A-241/-141C Del A-241/-141 Ins

P <0.02 P <0.01

Transient expression of luciferase enzymatic activity driven by the DRD2 5’-flanking 304 bp containing the A-241 and -141C Del alleles, the A-241 and -141C Ins alleles in Y79 (A) and 293 (B) cells

From Arinami et al, 1997.

Functional Effects of the DRD2 -141C Ins/Del

Polymorphism

Percentage

7

Del-

Del+

BP

RS

tota

l 18

Baseline Week 10 Clozapine

25

30

35

40

45

DRD2 -141C Ins/Del and Clozapine Response

BPRS=Brief Psychiatric Rating Scale.

8

Dopamine D2 Receptor Upregulation after

Antipsychotic Treatment

Silvestri et al. 2000

9

DRD2 Promoter Region Polymorphisms in First-episode

Schizophrenia• 61 first-episode patients (schizophrenia/schizoaffective

disorder/schizophreniform disorder)– 74% male; mean age 24±5 years, range 16-38 years

• Random assignment to medication– Risperidone (1-6 mg, n=33) or olanzapine (2.5-20 mg, n=28)

• Raters blind to medication and genotype– Weekly (first 4 weeks), then biweekly ratings up to 16 weeks

• Response: absence of delusions, hallucinations, and substantial thought disorder– Mild (3) or less on SADS-C positive symptom items– “Much Improved” or “Very Much Improved” on CGI change

item– Sustained for two or more consecutive ratings

CGI=Clinical Global Impression; SADS-C=Schedule for Affective Disorders and Schizophrenia–Change Version.Lencz T et al. Am J Psychiatry. 2006;163:529-531.

10

DRD2 -141C Ins/Del and Response

to Atypical Antipsychotics

Del+ (n=30)

Del- (n=31)

Log rank=5.0, df=1, P=.025.

Time (wk)

1614121086420Init

iati

ng

su

sta

ined

resp

on

se (

%)

Modified from Lencz T et al. Am J Psychiatry. 2006;163:529-531.

100

90

80

70

60

50

40

30

20

100

11

DRD2 -141C Ins/Del and Antipsychotic Response: Meta –

Analytic Results

Study or Subgroup

Lencz 2006Malhotra 1999Shen 2008Wu 2005Xing 2007Yamanouchi 2003

Total (95% CI)

Total eventsHeterogeneity: Chi² = 9.23, df = 5 (P = 0.10); I² = 46%Test for overall effect: Z = 2.13 (P = 0.03)

Events

52

138

184

50

Total

302130292841

179

Events

1019505354

9

195

Total

315198

10697

125

508

Weight

13.5%16.5%21.9%27.2%14.2%

6.6%

100.0%

M-H, Fixed, 95% CI

0.42 [0.12, 1.42]0.18 [0.04, 0.85]0.73 [0.32, 1.67]0.38 [0.16, 0.94]1.43 [0.60, 3.42]1.39 [0.41, 4.79]

0.65 [0.43, 0.97]

Del Carrier Ins/Ins Odds Ratio Odds RatioM-H, Fixed, 95% CI

0.05 0.2 1 5 20Favours Ins/Ins Favours Del Carrier

12

DRD2 -141C Ins/Del and Antipsychotic Response: Meta –

Analytic Results

Study or Subgroup

Lencz 2006Wu 2005Yamanouchi 2003

Total (95% CI)

Total eventsHeterogeneity: Chi² = 2.90, df = 2 (P = 0.23); I² = 31%Test for overall effect: Z = 2.00 (P = 0.05)

Events

584

17

Total

302930

89

Events

10539

72

Total

3110690

227

Weight

28.7%57.7%13.6%

100.0%

M-H, Fixed, 95% CI

0.42 [0.12, 1.42]0.38 [0.16, 0.94]1.38 [0.39, 4.87]

0.53 [0.28, 0.99]

Del Carrier Ins/Ins Odds Ratio Odds RatioM-H, Fixed, 95% CI

0.05 0.2 1 5 20Favours experimental Favours control

13

DRD2 Predicts Acute Weight Gain

OLZRIS

6-W

EE

K W

T G

AIN

(P

OU

ND

S) 26

24

22

20

18

16

14

12

10

8

6

4

2

0

DRD2 DEL-141C

Non-Carrier

Carrier

MED p<.05

DRD2 p<.05

14

Affymetrix 500K Platform: Specifications and Quality

Control• Marker spacing: 2.5kb (median); 5.8kb (mean)

• Mean Call Rate = 97% (range: 90-99)

• Mean heterozygosity = 27%

• 22 samples repeated; all SNPs >

• 1 error dropped

• Concordance across 454,699 SNPs > 99%

• SNPs with <85% calls excluded: 1,526

• SNPs not in HWE (p<.001) in controls: 13,662

• Total SNPs analyzed: 439,511

15

Assessing Treatment Responsivity in Schizophrenia

• Clozapine usually reserved for patients who failed two prior antipsychotic drug trials or have severe side effects.

• Clozapine – treated patients are more severely ill and treatment nonresponsive.– McEvoy et al. 2006:

• Patients entering CATIE CLZ trial (N=99) : 58% with > 4 prior hosps vs 48% for others (N=444) (p=0.03)

• PANSS total: CLZ trial subjects: 87.6 + 20.2; Others: 77.0 +18.6 (p<0.001).

16

Treatment Response Phenotype in Phase I Whole

Genome Analyses

Clozapine(n = 62)

Non-Clozapine(n = 110)

P Value

Age 37.10 ± 10.38

38.47 ± 10.62 0.41

% Female 29.03% 39.10% 0.19

Age of Onset

20.89 ± 5.41 20.69 ± 6.49 0.84

% Positive Family History

31.58% 20.21% 0.12

17

Treatment Responsive vs. Treatment Nonresponsive:

Phase I Results

P = 5*10-6

18

Genes Associated with Treatment Response: Affy

500K Phase I Results

Chrom Gene (Function) P value3p Axonal cell

adhesion4.6*10-7

19p SNARE-related 9.4*10-7

8q Neuroreceptor (cannabinoid)

2.2*10-6

5q Lipid transport 3.0*10-6

8p Protein phosphatase

subunit

3.2*10-6

19

Pharmacogenetics of Antipsychotic Drug Response:

Conclusions

• Multiple candidate genes have been investigated in relatively small samples with inconsistent results

• DRD2: Candidate genes and meta-analytic support for role in antipsychotic efficacy

• Adverse events may be more amenable for pharmacogenetic targeting

• New genomic tools will markedly expand the opportunity for pharmacogenetic studies over the next few years