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Shad. J Transl Genet Genom 2023;7:141-65 https://dx.doi.org/10.20517/jtgg.2023.11 Page 147

response than the 1-2 genotype group in African
American (P = 0.016)
Hwang et al., DRD2 Taq1A, Taq1B, 132 Caucasian and African NA BPRS At least 6 months -TaqIB frequencies differed b/w responders and
[64]
2005 rs1125394 American nonresponders in African Americans (P = 0.033)
-Allele 2 (B2) associated with response African
Americans. (P = 0.036).
-Allele 1 of rs1125394 (P = 0.029) and TaqIA,
allele A2 more frequent in African American
responders (P = 0.010)
- TaqIA A1 (-) associated with response in
African Americans (P = 0.032)
Malhotra DRD2 -141C Ins/Del 72 NA NA 10 weeks BPRS NA
[65]
1999
Hwang et al., -DRD4 120 bp tandem 232 Caucasians and African NA 6 months BPRS, BPOS, BNEG -Association b/w 1-copy allele of 120-bp tandem
[66]
2012 repeat and 142 bp/140 bp Americans repeat polymorphism and nonresponse in African
-DRD4 48 bp repeat in Americans (P = 0.004).
Caucasian samples -Short alleles (≤ 6R) with a better response on
the BPOS scale (P = 0.031) in the Caucasians
Zhao et al., DRD4 48 bp variant number 81 Chinese 200-450 mg/day 2 months PANSS Frequencies of DRD4 5 allele (P < 0.05) and 5/5
[67]
2005 tandem repeat (P < 0.05) genotypes were significantly higher in
nonresponders than that in responders
Hwang et al., -DRD1 rs265976 232 Caucasians and African NA At least 6 BPRS, BPOS, BNEG -DRD1 rs265976, genotype occurred more
[68]
2007 -Haplotype SNPs in Americans months frequently in responders in African Americans (P
rs265981, rs4532, rs686 = 0.03)
-T-G-A haplotype with poor response in
Caucasians (P = 0.027)

Potkin et al., DRD1 A-48G 15 Caucasian and African Average Dose = 460 ± 11 5 weeks BPRS DRD1 2,2 genotype significantly improved with
[69]
2003 American mg/day clozapine treatment, demonstrating a 30%
decrease in the BPRS-positive symptoms
compared to a 7% worsening for the 1,2
genotypes (P < 0.05)
Woodward et al., COMT Val108/158Met 86 Caucasian and African NA 6 months COWAT, CIGT, Better performance on global cognition (P =
[70]
2007 American DSST 0.01), attention and verbal fluency (P < 0.032),
ACTT and working memory (P < 0.001) in patients with
Met/Met than Val/Val genotype after clozapine
treatment
[71]
Xu et al., 2010 SLC6A3 rs2975226 160 Chinese Average dose = 415 ± 97 At least 8 weeks BPRS SNP rs2975226 (T-71A) in the 5′-regulatory
mg/day region frequencies were statistically different
between CLZ responders and nonresponders
allele-wise (adjusted P = 0.000674) and
genotype-wise (adjusted P = 0.024)

Serotonin-Associated Genes
Arranz et al., HTR2A His452Tyr (rs6314) 153 Caucasian Dose range 125-600 NA GAS Tyr452 was associated with poorer CLZ response
[72]
1996 mg/day than those without this allele (11% vs. 6%,
respectively