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Genetic epidemiology of pharmacogenetic variants in South East Asian Malays using whole-genome sequences

Sivadas A, Salleh MZ, Teh LK, Scaria V

Pharmacogenomics J, 2017 10;17(5):461-470.
PMID: 27241059 DOI: 10.1038/tpj.2016.39

Expanding the scope of pharmacogenomic research by including multiple global populations is integral to building robust evidence for its clinical translation. Deep whole-genome sequencing of diverse ethnic populations provides a unique opportunity to study rare and common pharmacogenomic markers that often vary in frequency across populations. In this study, we aim to build a diverse map of pharmacogenetic variants in South East Asian (SEA) Malay population using deep whole-genome sequences of 100 healthy SEA Malay individuals. We investigated the allelic diversity of potentially deleterious pharmacogenomic variants in SEA Malay population. Our analysis revealed 227 common and 466 rare potentially functional single nucleotide variants (SNVs) in 437 pharmacogenomic genes involved in drug metabolism, transport and target genes, including 74 novel variants. This study has created one of the most comprehensive maps of pharmacogenetic markers in any population from whole genomes and will hugely benefit pharmacogenomic investigations and drug dosage recommendations in SEA Malays.

Matched MeSH terms: Pharmacogenetics/methods*
Pharmacogenomics of CYP2D6: molecular genetics, interethnic differences and clinical importance

Teh LK, Bertilsson L

Drug Metab. Pharmacokinet., 2012;27(1):55-67.
PMID: 22185816

CYP2D6 has received intense attention since the beginning of the pharmacogenetic era in the 1970s. This is because of its involvement in the metabolism of more than 25% of the marketed drugs, the large geographical and inter-ethnic differences in the genetic polymorphism and possible drug-induced toxicity. Many interesting reviews have been published on CYP2D6 and this review aims to reinstate the importance of the genetic polymorphism of CYP2D6 in different populations as well as some clinical implications and important drug interactions.

Matched MeSH terms: Pharmacogenetics/methods
Roles of pharmacogenomics in non-anthracycline antineoplastic-induced cardiovascular toxicities: A systematic review and meta-analysis of genotypes effect

Leong SL, Chaiyakunapruk N, Tassaneeyakul W, Arunmanakul P, Nathisuwan S, Lee SWH

Int J Cardiol, 2019 04 01;280:190-197.
PMID: 30594345 DOI: 10.1016/j.ijcard.2018.12.049

BACKGROUND: Exploration on genetic roles in antineoplastic-related cardiovascular toxicity has increased with the advancement of genotyping technology. However, knowledge on the extent of genetic determinants in affecting the susceptibility to the cardiovascular toxicities of antineoplastic is limited. This study aims to identify potential single nucleotide polymorphism (SNP) in predicting non-anthracycline antineoplastic-related cardiovascular toxicity.
METHODS: We systematically searched for original research in PubMed, Cochrane Central Register of Controlled Studies, CINAHL Plus, EMBASE and HuGE Navigator from database inception until January 2018. Studies on association between polymorphism and antineoplastic-induced cardiovascular toxicity in patients treated for cancer of all antineoplastic agents were included except for anthracycline. Case reports, conference abstracts, reviews and non-patient studies were excluded. Data extracted by two independent reviewers were combined with random-effects model and reported according to PRISMA and MOOSE guidelines.
RESULTS: The 35 studies included examined a total of 219 SNPs in 80 genes, 11 antineoplastic and 5 types of cardiovascular toxicities. Meta-analyses showed that human epidermal growth factor receptor 2 (HER2) rs1136201, a risk variants (pooled OR: 2.43; 1.17-5.06, p = 0.018) is a potential predictors for trastuzumab-related cardiotoxicity. Gene dose effect analysis showed number of variant allele may contribute to the risk too.
CONCLUSIONS: This review found that HER2 rs1136201 can have the potential in predicting trastuzumab-related heart failure. As such, further studies are needed to confirm the validity of these results as well as determine the economic aspect of using SNPs prior to its implementation as a clinical practice.

Matched MeSH terms: Pharmacogenetics/methods*
Fulltext Distribution of alleles, genotypes and haplotypes of the CYP2B6 (rs3745274; rs2279343) and CYP3A4 (rs2740574) genes in the Malian population: Implication for pharmacogenetics

Kassogue Y, Diakite B, Kassogue O, Konate I, Tamboura K, Diarra Z, et al.

Medicine (Baltimore), 2021 Jul 23;100(29):e26614.
PMID: 34398016 DOI: 10.1097/MD.0000000000026614

Cytochrome P450 enzymes play a central role in the phase I biotransformation process of a wide range of compounds, including xenobiotics, drugs, hormones and vitamins. It is noteworthy that these enzymes are highly polymorphic and, depending on the genetic makeup, an individual may have impaired enzymatic activity. Therefore, the identification of genetic variants in these genes could facilitate the implementation of pharmacogenetic studies and genetic predisposition to multifactorial diseases. We have established the frequencies of CYP2B6 (rs3745274; rs2279343) and CYP3A4 (rs2740574) alleles and genotypes in 209 healthy Malian subjects using TaqMan drug metabolism genotyping assays for allelic discrimination. Allele frequencies were 37% for CYP2B6 rs3745274; 38% for CYP2B6 rs2279343; and 75% for CYP3A4 rs2740574 respectively. Overall, the frequencies observed in Mali are statistically comparable to those reported across Africa except North Africa. The major haplotypes in CYP2B6 rs3745274 and CYP2B6 rs2279343 were represented by GA (60.24%) followed by TG (35.36%). We noted a strong linkage disequilibrium between CYP2B6 rs3745274 and CYP2B6 rs2279343 with D' = 0.91 and r2 = 0.9. The frequencies of the genotypic combinations were 43.5% (GT/AG), 37.3% (GG/AA) and 11.5% (TT/GG) in the combination of CYP2B6-rs3745274 and CYP2B6-rs2279343; 26.8% (GT/CC), 25.4%, (GT/CT), 17.2% and GG/CT in the combination CYP2B6-rs3745274-CYP3A4-rs2740574; 26.8% (AG/CC), 23.9% (AA/CC), 19.1% (AG/CT), and 11% (AA/CT) in the combination CYP2B6-rs2279343-CYP3A4-rs2740574, respectively. The most common triple genotype was GT/AG/CC with 24.9%, followed by GG/AA/CC with 23.9%, GT/AG/CT with 16.7%, and GG/AA/CT with 10%. Our results provide new insights into the distribution of these pharmacogenetically relevant genes in the Malian population. Moreover, these data will be useful for studies of individual genetic variability to drugs and genetic predisposition to diseases.

Matched MeSH terms: Pharmacogenetics/methods
Polymorphisms of UGT1A1*6, UGT1A1*27 & UGT1A1*28 in three major ethnic groups from Malaysia

Teh LK, Hashim H, Zakaria ZA, Salleh MZ

Indian J Med Res, 2012 Aug;136(2):249-59.
PMID: 22960892

Genetic polymorphisms of uridine diphosphate glucuronyltransferase 1A1 (UGT1A1) have been associated with a wide variation of responses among patients prescribed with irinotecan. Lack of this enzyme is known to be associated with a high incidence of severe toxicity. The objective of this study was to investigate the prevalence of three different variants of UGT1A1 (UGT1A1*6, UGT1A1*27 and UGT1A1*28), which are associated with reduced enzyme activity and increased irinotecan toxicity, in the three main ethnic groups in Malaysia (Malays, Chinese and Indians).

Matched MeSH terms: Pharmacogenetics/methods
Pharmacogenetic screening of carbamazepine-induced severe cutaneous allergic reactions

Locharernkul C, Shotelersuk V, Hirankarn N

J Clin Neurosci, 2011 Oct;18(10):1289-94.
PMID: 21802305 DOI: 10.1016/j.jocn.2010.12.054

Recent studies associated the HLA-B 1502 allele with carbamazepine (CBZ)-induced Stevens-Johnson syndrome (SJS)/toxic epidermal necrolysis (TEN) in patients from China, Thailand and Malaysia. No association has been found in patients from Europe or Japan. Linkage summary reports from East and South-east Asia predict a highly significant odds ratio (OR) of 84.75 (95% confidence interval [CI]=42.53-168.91; p=8.96×10[-15]) with sensitivity and negative predictive values of 92% and 98%, respectively. The higher prevalence of HLA-B 1502 allele among certain Asian populations (10-15%) compared to Caucasians (1-2%) may explain a 10-fold to 25-fold higher incidence of CBZ-SJS/TEN in patients from Asia. Screening for HLA-B 1502 before using CBZ can prevent SJS/TEN in certain populations, but screening may be less beneficial in populations with low HLA-B 1502 allele frequency and in patients exposed to CBZ for more than 2 months. A retrospective study demonstrated that the costs of HLA-B 1502 screening were less than those of SJS treatment. This article reviews possible benefits and concerns of HLA-B 1502 screening in clinical practice.

Matched MeSH terms: Pharmacogenetics/methods*
Fulltext Systematic pharmacogenomics analysis of a Malay whole genome: proof of concept for personalized medicine

Salleh MZ, Teh LK, Lee LS, Ismet RI, Patowary A, Joshi K, et al.

PLoS One, 2013;8(8):e71554.
PMID: 24009664 DOI: 10.1371/journal.pone.0071554

BACKGROUND: With a higher throughput and lower cost in sequencing, second generation sequencing technology has immense potential for translation into clinical practice and in the realization of pharmacogenomics based patient care. The systematic analysis of whole genome sequences to assess patient to patient variability in pharmacokinetics and pharmacodynamics responses towards drugs would be the next step in future medicine in line with the vision of personalizing medicine.
METHODS: Genomic DNA obtained from a 55 years old, self-declared healthy, anonymous male of Malay descent was sequenced. The subject's mother died of lung cancer and the father had a history of schizophrenia and deceased at the age of 65 years old. A systematic, intuitive computational workflow/pipeline integrating custom algorithm in tandem with large datasets of variant annotations and gene functions for genetic variations with pharmacogenomics impact was developed. A comprehensive pathway map of drug transport, metabolism and action was used as a template to map non-synonymous variations with potential functional consequences.
PRINCIPAL FINDINGS: Over 3 million known variations and 100,898 novel variations in the Malay genome were identified. Further in-depth pharmacogenetics analysis revealed a total of 607 unique variants in 563 proteins, with the eventual identification of 4 drug transport genes, 2 drug metabolizing enzyme genes and 33 target genes harboring deleterious SNVs involved in pharmacological pathways, which could have a potential role in clinical settings.
CONCLUSIONS: The current study successfully unravels the potential of personal genome sequencing in understanding the functionally relevant variations with potential influence on drug transport, metabolism and differential therapeutic outcomes. These will be essential for realizing personalized medicine through the use of comprehensive computational pipeline for systematic data mining and analysis.

Matched MeSH terms: Pharmacogenetics/methods*
Cost-effectiveness analysis of pharmacogenetic-guided warfarin dosing in Thailand

Chong HY, Saokaew S, Dumrongprat K, Permsuwan U, Wu DB, Sritara P, et al.

Thromb Res, 2014 Dec;134(6):1278-84.
PMID: 25456732 DOI: 10.1016/j.thromres.2014.10.006

Pharmacogenetic (PGx) test is a useful tool for guiding physician on an initiation of an optimal warfarin dose. To implement of such strategy, the evidence on the economic value is needed. This study aimed to determine the cost-effectiveness of PGx-guided warfarin dosing compared with usual care (UC).

Matched MeSH terms: Pharmacogenetics/methods
Translational aspects of genetic factors in the prediction of drug response variability: a case study of warfarin pharmacogenomics in a multi-ethnic cohort from Asia

Chan SL, Suo C, Lee SC, Goh BC, Chia KS, Teo YY

Pharmacogenomics J, 2012 Aug;12(4):312-8.
PMID: 21383771 DOI: 10.1038/tpj.2011.7

Genetic markers displaying highly significant statistical associations with complex phenotypes may not necessarily possess sufficient clinical validity to be useful. Understanding the contribution of these markers beyond readily available clinical biomarkers is particularly important in pharmacogenetics. We demonstrate the utility of genetic testing using the example of warfarin in a multi-ethnic setting comprising of three Asian populations that are broadly representative of the genetic diversity for half of the population in the world, especially as distinct interethnic differences in warfarin dose requirements have been previously established. We confirmed the roles of three well-established loci (CYP2C9, VKORC1 and CYP4F2) in explaining warfarin dosage variation in the three Asian populations. In addition, we assessed the relationship between ethnicity and the genotypes of these loci, observing strong correlations at VKORC1 and CYP4F2. Subsequently, we established the additional utility of these genetic factors in predicting warfarin dose beyond ethnicity and clinical biomarkers through performing a series of systematic cross-validation analyses of the relative predictive accuracies of various fixed-dose regimen, clinical and genetic models. Through a pharmacogenetics model for warfarin, we show the importance of genetic testing beyond readily available clinical biomarkers in predicting dose requirements, confirming the role of genetic profiling in personalized medicine.

Matched MeSH terms: Pharmacogenetics/methods*
Interethnic comparisons of important pharmacology genes using SNP databases: potential application to drug regulatory assessments

Chen J, Teo YY, Toh DS, Sung C

Pharmacogenomics, 2010 Aug;11(8):1077-94.
PMID: 20712526 DOI: 10.2217/pgs.10.79

The frequencies of alleles implicated in drug-response variability provide vital information for public health management. Differences in frequencies between genetically diverse groups of individuals can hamper drug assessments, particularly in populations where clinical data are not readily available.

Matched MeSH terms: Pharmacogenetics/methods*
Fulltext Effect of polymorphisms within methotrexate pathway genes on methotrexate toxicity and plasma levels in adults with hematological malignancies

Suthandiram S, Gan GG, Zain SM, Bee PC, Lian LH, Chang KM, et al.

Pharmacogenomics, 2014 Aug;15(11):1479-94.
PMID: 25303299 DOI: 10.2217/pgs.14.97

Pharmacogenetics of methotrexate (MTX) contributes to interindividual differences in toxicity. We aimed to evaluate the impact of SNPs within the MTX pathway genes on MTX-induced toxicity and MTX plasma levels at 48 h following treatment in Asian adults with acute lymphoblastic leukemia or non-Hodgkin lymphoma.

Matched MeSH terms: Pharmacogenetics/methods