The Diversity of CYP2C19 Polymorphisms in the Thai Population: Implications for Precision Medicine.

Introduction: CYP2C19 plays a major role in the metabolism of various drugs. The most common genetic variants were the CYP2C19*2 and *3 alleles (rs4244285 and rs4986893, non-functional variants). In previous studies, we found that genetic polymorphisms in CYP2C19 variants influenced the active metabolites of clopidogrel and caused major adverse cardiovascular and cerebrovascular effects. However, the distribution of CYP2C19 varies among ethnic groups and according to adverse drug reactions. This study aimed to investigate the frequency of CYP2C19 genetic polymorphisms in the Thai population and analyze the differences in the frequency of CYP2C19 genetic polymorphisms between Thai and other populations. Methods: This study enrolled 211 unrelated healthy Thai individuals in total. We performed a real-time polymerase chain reaction to genotype CYP2C19*2 (681G > A) and CYP2C19*3 (636G > A). Results: In the Thai population, the CYP2C19*1 allele was the most prevalent at 70.14%, while the CYP2C19*2 and *3 alleles were found at frequencies of 25.36% and 4.50%, respectively. Conversely, the CYP2C19*3 allele was not detected in Caucasian, Hispanic, African, Italian, Macedonian, Tanzanian, or North Indian populations. The phenotypic profile of this gene revealed that the frequency of intermediate metabolizers (IMs) is nearly equal to that of extensive metabolizers (EMs), at 42.65% and 48.82% respectively, with genotypes *1/*2 (36.02%) and *1/*3 (6.63%). Likewise, poor metabolizers (PMs) with genotypes *2/*2 (6.16%), *2/*3 (2.37%), and *3/*3 (<1%) are more prevalent in our population as well. Conclusion: The distribution of CYP2C19 genotype and phenotype influenced by non-functional alleles has potential as a pharmacogenomics biomarker for precision medicine and is dependent on an ethnic-specific genetic variation database.

CYP450 and drug efflux transporters polymorphism influence clinical outcomes of Thai osimertinib-treated non-small cell lung cancer patients.

Background: Osimertinib has shown greater efficacy than standard epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) and fewer grade 3 or higher adverse drug reactions (ADRs) in patients with advanced non-small cell lung cancer (NSCLC) harboring epidermal growth factor receptor (EGFR) mutations. However, the clinical outcomes of osimertinib treatment vary depending on the patient's ethnicity. Therefore, further research is necessary to evaluate the impact of single nucleotide polymorphisms (SNPs) in cytochrome P450 (CYP450) and drug transporters on the therapeutic outcomes and ADRs to osimertinib in Thai patients, to provide improved pharmacological treatments for cancer patients. Methods: This retrospective and prospective cohort study enrolled 63 Thai patients with NSCLC treated with 80 mg of osimertinib once daily as monotherapy. Seventeen SNPs in candidate genes related to drug metabolism and transport pathways were analyzed in each patient. Chi-square or Fisher's exact tests were used to evaluate the associations between SNPs and clinical outcomes, including ADR incidence and objective response rate (ORR). In addition, the correlation between the genotype and median time to treatment failure (TTF) or progression-free survival (PFS) was assessed using Kaplan-Meier analysis and a log-rank test. Results: We identified six SNPs (rs2231142 and rs2622604 in ABCG2, rs762551 in CYP1A2, rs1057910 in CYP2C9, rs28371759 in CYP3A4, and CYP2A6 deletion polymorphism (CYP2A6*4)) that significantly increased the incidence of ADRs. In addition, we found two SNPs (rs2069514 in CYP1A2 and rs1057910 in CYP2C9) that significantly decreased the median TTF, and two SNPs (rs28399433 in CYP2A6 and rs1057910 in CYP2C9) that significantly decreased the median progression-free survival (PFS). Specifically, we found that one of these SNPs (rs1057910 in CYP2C9) influenced ADRs, TTF, and PFS. Additionally, SNPs in the CYP2A6 heterozygous variant (non4/*4) significantly increased ADR incidence, leading to a high frequency of dose reduction (27.0%). Conclusion: Our study demonstrated significant SNPs associated with increased ADR incidence, decreased PFS, and decreased TTF in Thai patients with NSCLC treated with osimertinib. The CYP2C9 (*3) and CYP2A6 (*4) allele frequencies differed between ethnicities and were associated with an increased incidence of ADRs. These findings highlight the importance of considering genetic factors in NSCLC treatment and may facilitate personalized medicine approaches. Moreover, our study showed a higher incidence of ADRs than the previous trials, including FLAURA and AURA2, and a higher frequency of dose reduction than reported in the AURA 3 trial, possibly due to genetic differences among the study populations.

Effects of polymorphisms in the MTHFR gene on 5-FU hematological toxicity and efficacy in Thai colorectal cancer patients.

Background: The two common methylenetetrahydrofolate reductase (MTHFR) polymorphisms 677G>A and 1298A>C may have been affecting 5-FU toxicity in cancer patients for decades. Drug efficacy has also been shown by previous studies to be affected. In this study, we investigated the effects of these polymorphisms on 5-FU hematological toxicity and treatment efficacy, to provide enhanced pharmacological treatment for cancer patients. Methods: This is a retrospective study involving 52 Thai colorectal cancer patients who were treated with 5-FU based therapy, using TaqMAN real-time PCR to genotype the MTHFR polymorphisms (677G>A and 1298A>C). The toxicity and response rate were assessed using standardized measures. Results: Neutropenia was significantly more likely to be experienced (P=0.049, OR=7.286, 95% CI=0.697-76.181) by patients with the MTHFR 677G>A polymorphism, in the same way as leukopenia (P =0.036, OR=3.333, 95%CI=2.183-5.090) and thrombocytopenia (P<0.001, OR=3.917, 95%CI=2.404-6.382). The MTHFR 1298A>C polymorphism had no statistical association with hematological toxicity in 5-FU treatment. The response rate to 5-FU was not significantly affected by these two polymorphisms. Conclusion: The MTHFR polymorphism 677G>A is a significant risk factor for developing leukopenia, neutropenia and thrombocytopenia as toxic effects of 5-FU therapy in cancer patients. Therefore, patients receiving 5-FU-based therapy should be aware of their polymorphisms as one risk factor for experiencing severe toxicity.

Associations between UGT1A1 and SLCO1B1 polymorphisms and susceptibility to neonatal hyperbilirubinemia in Thai population.

Hyperbilirubinemia is the main mechanism that causes neonatal jaundice, and genetics is one of the risk factors of hyperbilirubinemia. Therefore, this study aims to explore the correlation between two genes, UGT1A1 and SLCO1B1, and hyperbilirubinemia in Thai neonates. One hundred thirty seven neonates were recruited from Division of Clinical Chemistry, Ramathibodi Hospital. UGT1A1*28 and *6 were determined by pyrosequencing whereas, SLCO1B1 388A > G and 521 T > C genetic variants were determined by TaqMan® real-time polymerase chain reaction. Neonates carrying with homozygous (AA) and heterozygous (GA) variants in UGT1A1*6 were significantly related to hyperbilirubinemia development compared with wild type (GG; P < 0.001). To the combined of UGT1A1, total bilirubin levels in homozygous variant were higher significantly than heterozygous variant and wild type (P = 0.002, P = 0.003, respectively). Moreover, SLCO1B1 combination was significant differences between the hyperbilirubinemia and the control group (P = 0.041). SLCO1B1 521 T > C variant provide protection for Thai neonatal hyperbilirubinemia (P = 0.041). There are no significant differences in UGT1A1*28 and SLCO1B1 388A > G for the different severity of hyperbilirubinemia. The combined UGT1A1*28 and *6 polymorphism is a strong risk factor for the development of severe hyperbilirubinemia in Thai neonates. Therefore, we suggest neonates with this gene should be closely observed to avoid higher severities of bilirubin.

Association of UGT1A1*6, UGT1A1*28, or ABCC2 c.3972C>T genetic polymorphisms with irinotecan-induced toxicity in Asian cancer patients: Meta-analysis.

Effects of UGT1A1*6 and UGT1A1*28 genetic polymorphisms on irinotecan-induced severe toxicities in Asian cancer patients are inconclusive. Also, ABCC2 c.3972C>T may affect toxicity of irinotecan. The aim was to assess the aggregated risk of neutropenia or diarrhea in Asian cancer patients taking irinotecan and inherited UGT1A1*6, UGT1A1*28, or ABCC2 c.3972C>T genetic variants. A PubMed literature search for eligible studies was conducted. Odds ratios (ORs) were measured using RevMan software where p values <0.05 were statistically significant. Patients that inherited both UGT1A1*6 and UGT1A1*28 genetic variants (heterozygous: UGT1A1*1/*6 + *1/*28 and homozygous: UGT1A1*6/*6 + *28/*28) were significantly associated with increased risk of neutropenia and diarrhea compared to patients with UGT1A1*1/*1 (neutropenia: OR 2.89; 95% CI 1.97-4.23; p < 0.00001; diarrhea: OR 2.26; 95% CI 1.71-2.99; p < 0.00001). Patients carrying homozygous variants had much stronger effects in developing toxicities (neutropenia: OR 6.23; 95% CI 3.11-12.47; p < 0.00001; diarrhea: OR 3.21; 95% CI 2.13-4.85; p < 0.00001) than those with heterozygous variants. However, patients carrying the ABCC2 c.3972C>T genetic variant were not significantly associated with neutropenia (OR 1.67; 95% CI 0.98-2.84; p = 0.06) and were significantly associated with a reduction in irinotecan-induced diarrhea (OR 0.31; 95% CI 0.11-0.81; p = 0.02). Asian cancer patients should undergo screening for both UGT1A1*6 and UGT1A1*28 genetic variants to reduce substantially irinotecan-induced severe toxicities.

Enteropathogenic Bacterial and Intestinal Parasitic Infections among Asymptomatic Food Handlers in Rangsit University Canteens, Central Thailand.

Food handlers play an important role in the transmission of foodborne diseases. 108 asymptomatic food handlers work in RSU canteens and have never been checked for intestinal bacteria and parasites, which might be a potential source of infection for customers. This study is aimed at estimating the prevalence of enteropathogenic bacterial and intestinal parasitic infections among food handlers in Rangsit University canteens, central Thailand. A total of 79 food handlers were enrolled, and each provided one stool sample (response rate of 73.2%). Females comprised 93.7% of study participants, and the largest age group was 41-50 years (34.2%). The prevalence of enteropathogenic bacteria in stool cultures was 2.5%, and only Aeromonas spp. were detected. The pathogenic protozoa Giardia duodenalis was detected in 1.3% of samples, and nonpathogenic protozoa was found in 11.4%. No helminths were found in any samples. Approximately 80% of food handlers demonstrated good hygiene practices, including regular hand washing after visiting the toilet, regular hand washing when preparing food, using soap when washing hands, wearing uniforms/gowns, practicing correct hand washing techniques, and having short fingernails. However, the results showed a lack of personal hygiene training and routine medical care (>50% of samples). Stronger intervention would help to eliminate future infections.

Effect of drug metabolizing enzymes and transporters in Thai colorectal cancer patients treated with irinotecan-based chemotherapy.

Genetic polymorphisms in drug metabolizing enzymes and drug transporters may affect irinotecan toxicity. Although genetic polymorphisms have been shown to influence the irinotecan toxicity, data are limited in Thai population. Thus, the aim of this study was to assess the allele and genotype frequencies and the relationship between CYP3A4/5, DPYD, UGT1A1, ABCB1, and ABCC2 genetic variations and irinotecan-induced toxicity in Thai colorectal cancer patients. One hundred and thirty-two patients were genotyped, and the effect of genetic variations on irinotecan-induced toxicity was assessed in 66 patients who received irinotecan-based chemotherapy. Allele frequencies of ABCB1 c.1236C > T, ABCB1 c.3435C > T, ABCC2 c.3972C > T, ABCG2 c.421C > A, CYP3A4*1B, CYP3A4*18, CYP3A5*3, DPYD*5, UGT1A1*28, and UGT1A1*6 were 0.67, 0.43, 0.23, 0.27, 0.01, 0.02, 0.64, 0.19, 0.16, and 0.09, respectively. DPYD*2A and DPYD c.1774C > T variants were not detected in our study population. The ABCC2 c.3972C > T was significantly associated with grade 1-4 neutropenia (P < 0.012) at the first cycle. Patients carrying both UGT1A1*28 and *6 were significantly associated with severe neutropenia at the first (P < 0.001) and second (P = 0.017) cycles. In addition, patients carrying UG1A1*28 and *6 had significantly lower absolute neutrophil count (ANC) nadir at first (P < 0.001) and second (P = 0.001) cycles. This finding suggests that UGT1A1*28, *6, and ABCC2 c.3972C > T might be an important predictor for irinotecan-induced severe neutropenia.

Determination of irinotecan, SN-38 and SN-38 glucuronide using HPLC/MS/MS: Application in a clinical pharmacokinetic and personalized medicine in colorectal cancer patients.

BACKGROUND: Irinotecan (CPT-11) is chemotherapy used mainly in the metastatic colorectal cancer. The purpose of this study was to develop and validate the LC-MS/MS for the simultaneous determination of CPT-11, SN-38, and SN-38G. METHODS: A 100 µL of plasma was prepared after protein precipitation and analyzed on a C18 column using 0.1% acetic acid in water and 0.1% acetic acid in acetonitrile as mobile phases. The mass spectrometer worked with multiple reaction monitoring (MRM) in positive scan mode. The standard curves were linear on a concentration range of 5-10 000 ng/mL for CPT-11, 5-1000 ng/mL for SN-38, and 8-1000 ng/mL for SN-38G. RESULTS: In this assay, the intra and interday precision consisted of ≤9.11% and ≤11.29% for CPT-11, ≤8.70% and 8.31% for SN-38, and ≤9.90 and 9.64% for SN-38G. CONCLUSION: This method was successfully used to quantify CPT-11, SN-38, and SN-38G and applied to a pharmacokinetic study.

Correlation of UGT1A1(*)28 and (*)6 polymorphisms with irinotecan-induced neutropenia in Thai colorectal cancer patients.

UDP-glucuronosyltransferase1A1 (UGT1A1) polymorphisms have been related with irinotecan toxicity. The purpose of this study was to determine the associations between UGT1A1(*)28 and (*)6 polymorphisms and irinotecan toxicity in Thai patients with metastatic colorectal cancer. 44 metastatic colorectal cancer patients received irinotecan-based chemotherapy. Hematologic toxicities were determined in the first and second cycles of treatment. The genotypes of UGT1A1(*)28 and (*)6 were analyzed by pyrosequencing technique. The frequencies of genetic testing for UGT1A1(*)28 and (*)6 polymorphisms were 22.8% (TA6/TA7; 20.5%, TA7/TA7; 2.3%) and 15.9% (GA), respectively. No patients had the homozygous UGT1A1(*)6 (AA). Neither UGT1A1(*)28 nor UGT1A1(*)6 polymorphisms were significantly associated with severe hematologic toxicities. However, analysis of UGT1A1(*)28 and (*)6 in combination revealed an association with severe neutropenia in the first and second cycles (P = 0.044, P = 0.017, respectively). Both UGT1A1(*)28 and (*)6 polymorphisms may have an increased risk of irinotecan-induced neutropenia in Thai colorectal cancer patients.

Development of Pyrosequencing Method for Detection of UGT1A1 Polymorphisms in Thai Colorectal Cancers.

BACKGROUND: UGT1A1 is a polymorphic enzyme that has been associated with irinotecan drug metabolisms. We developed a pyrosequencing method to detect allele frequency and genotype of UGT1A1 polymorphisms (UGT1A1*28 and UGT1A1*6) in Thai colorectal cancer patients. METHOD: A pyrosequencing method was designed to determine UGT1A1 genetic polymorphisms including UGT1A1*28 (A[TA]7TAA) and UGT1A1*6 (211G>A) in 91 Thai colorectal cancers. RESULT: Genotyping by the pyrosequencing technique was 100% concordant with capillary electrophoresis sequencing. The allele frequencies for UGT1A1 genetic polymorphisms were *1/*1 (54.95%), *1/*6 (13.19%), *1/*28 (25.27%), *28/*6 (4.40%), and *28/*28 (2.20%). No homozygous mutation UGT1A1*6 was found in our population. CONCLUSIONS: We developed a rapid, reliable, more cost-effective, and simple assay to detect UGT1A1 genetic polymorphisms in routine practice before initiating irinotecan therapy. The UGT1A1*28 and UGT1A1*6 alleles were found to be similar in the Asian populations.