Meta-Analysis of NUDT15 Genetic Polymorphism on Thiopurine-Induced Myelosuppression in Asian Populations.

Backgound: The high incidence of thiopurine-induced myelosuppression in Asians is known to be attributable to genetic variation in thiopurine metabolism. A quantitative synthesis to summarize the genetic association with thiopurine-induced myelosuppression in Asians was therefore conducted. Methods: A Literature search was performed from January 2016 to May 2021 in the following databases: PubMed, Web of Science, and Embase and addition search included the studies from Zhang et al. Two reviewers independently extracted the following data: the author's name, year of publication, ethnicity, drugs, diseases, genetic polymorphisms, onset, type of myelosuppression and results of Hardy-Weinberg equilibrium. The Newcastle-Ottawa Scale was used to assess the quality of the studies. The pooled odds ratios (OR) and 95% confidence intervals (CI) were calculated to evaluate the associations of NUDT15 and the risk of thiopurine-induced myelosuppression stratified by onset and type of myelosuppressive. Subgroup analysis by NUDT15 genetic polymorphisms was performed. Results: A total of 30 studies was included in this meta-analysis. The overall OR for the relationship between NUDT15 genetic polymorphisms and thiopurine-induced early onset of leukopenia and neutropenia in Asian populations were 11.43 (95% CI 7.11-18.35) and 16.35 (95% CI 10.20-26.22). Among NUDT15 polymorphisms, NUDT15*3 showed a significantly increased risk of early leukopenia (OR 15.31; 95% CI 9.65-24.27) and early neutropenia (OR 15.85; 95% CI 8.80-28.53). A significantly higher thiopurine-induced early neutropenic risk was also found for NUDT15*2 (OR 37.51; 95% CI 1.99-708.69). Whereas, NUDT15*5 and NUDT15*6 variants showed a lower risk of leukopenia. Conclusion: This study suggests that NUDT15*3 and NUDT15*2 are important genetic markers of thiopurine-induced early onset of myelotoxicity in Asians, therefore, early detection of these variants before initiating thiopurine therapy is necessary.

Thiopurine S-methyltransferase and Pemphigus Vulgaris: A Phenotype-Genotype Study.

BACKGROUND & OBJECTIVE: Thiopurine drugs are considered as a treatment modality in various autoimmune disorders including pemphigus vulgaris (PV). These drugs are metabolized by an enzyme "Thiopurine S-methyl transferase" (TPMT). Various variants of this enzyme may have decreased activity leading to serious drug side effects. To investigate the phenotype and genotype of TPMT in PV patients receiving thiopurine drugs. METHODS: A total of 50 patients (29 women and 21 men) with pemphigus vulgaris treating with standard dose of Thiopurine drugs were selected. Sex, age, result of liver function test and complete blood count were recorded. Genotyping of two common non-functional allele (TPMT*2 and TPMT*3C) by Allele-specific and RFLP-PCR was performed. TPMT enzymatic level was determined by an ELISA based method. RESULTS: Of patients, 36 (72%) were found to have normal TPMT level; and 12, (24%) had higher level of enzyme and 2, 4% had low TPMT enzyme, but none of the patients showed mutant TPMT*2 and TPMT*3C alleles. None of the patients showed hepatotoxicity and bone marrow suppression. CONCLUSION: The phenotypic assay based on ELISA method may have false positive and misleading results but genotyping using PCR-RFLP and allele specific PCR is accurate, simple and cost-effective and can be used in patients decided to undergo thiopurine treatment.

Clinical Application of Thiopurine Pharmacogenomics in Pediatrics.

BACKGROUND: Thiopurine drugs are used for the treatment of pediatric diseases. Inter-individual differences in the metabolism of these drugs greatly influence the risk of thiopurine induced toxicity and therapy failure. These differences are the consequence of genomic, epigenomic and transcriptomic variability among patients. Pharmacogenomics aims to individualize therapy according to the specific genetic signature of a patient. Treatment protocols based on thiopurine drugs have already been improved by applying pharmacogenomics in pediatric clinical practice. OBJECTIVE: The aim of this review was to summarize the application of thiopurine pharmacogenomics in pediatric patients suffering from acute leukemias, different types of autoimmune and inflammatory diseases, as well as in posttransplant care. METHODS: We searched PubMed/Medline database to identify thiopurine pharmacogenomic markers clinically relevant in pediatric diseases. RESULTS: TPMT and NUDT15 pharmacogenomic testing is done in pediatric care, contributing to the reduction of thiopurine induced toxicity. Data on numerous novel potential pharmacogenomic markers relevant for optimization of thiopurine treatment are still controversial (ITPA, ABCC4, NT5C2, PRPS1, GSTM1, FTO gene variants). Majority of evidences regarding thiopurine pharmacogenomics in pediatrics have been acquired by studying acute lymphoblastic leukemia and inflammatory bowel disease. For other pediatric diseases, namely acute myeloid leukemia, non-Hodgkin lymphoma, juvenile idiopathic arthritis, atopic dermatitis, juvenile autoimmune hepatitis and renal allograft transplantation, data are still scarce. CONCLUSION: Thiopurine pharmacogenomics has shown to be one of the best examples of successful application of pharmacogenomics in pediatrics.

A Practical Non-Extraction Direct Liquid Chromatography Method for Determination of Thiopurine S-Methyltransferase Activity in Inflammatory Bowel Disease.

Thiopurine drugs remain pivotal therapies for the wide varieties of diseases such as inflammatory bowel disease (IBD). Here, thiopurine S-methyltransferase (TPMT) phenotype, the main metabolizing enzyme of thiopurine-drugs, was studied. This is for the first time that TPMT activity is measured in Iranian IBD patients. We used an improved direct liquid chromatography assay without need for solvent extraction and minimize excess labor handling making it ideal for use in routine referral medical centers. TPMT activity in whole blood was determined by a non-extraction HPLC method. We evaluated 427 individuals including 215 IBD patients and 212 unrelated healthy individuals as control group from Iran's western population. TPMT phenotyping of this study demonstrated no frequency for deficient, 2.8 % for low and 97.2% for normal activity, which is different with results of other studies. There was a significant negative correlation between TPMT activities as calculated based on nmol/grHb/h and the Hb-levels in IBD and control groups (r= -0.54, P<0.001 and r= -0.27, P<0.001), respectively. Interestingly a significant positive correlation between Hb levels and TPMT-activities were seen when the activity calculated in mU/L in IBD patients and control subjects (r=0.14, P=0.05 and r=0.43, P<0.001), respectively. We strongly suggest the use of international unit (mU/L) is more appropriate than nmol6MTG/grHb/h for expressing TPMT-activity in IBD patients. In addition, in comparison with other providers of TPMT test activity and centers around the world the risk of toxicity is much lower after utilizing thiopurine drugs for IBD patients in this region.

Role of TPMT Genetic Polymorphism in the Individualized Treatment of Thiopurine Drug / 现代检验医学杂志

Thiopurine S-methyltransferase (TPMT) is an important and key cytoplasmic enzyme in the metabolism of thiopurine drugs,whose activity can directly determine the amount of thiopurine drugs metabolized to cytotoxic 6-thioguanine nucleotides and consequently influence clinical efficacy and adverse drug reactions of thiopurine drugs.In order to deepen knowledge and role of genetic polymorphism of tpmt in the individualized thiopurine drug treatment,this present review mainly covered the following three frequently concerned aspects,including i) whether or not to determine the activity of TPMT priot to treatment of thiopurine drugs;ii) to genotype or to phenotype;iii) how to choose genotype methods.

Polymorphisms of the thiopurine S-methyltransferase gene among the Libyan population.

BACKGROUND: Thiopurine S-methyltransferase (TPMT) is a cytosolic enzyme that catalyses the S-methylation of 6-mercaptopurine and azathioprine. Low activity phenotypes are correlated with polymorphism in the TPMT gene. Patients with low or undetectable TMPT activity could develop severe myelosuppression when they are treated with standard doses of thiopurine drugs. Since ethnic differences in the TPMT gene polymorphism have been demonstrated worldwide, assessing it in the Libyan population is worthwhile. METHODS: We investigated TPMT gene polymorphism in a total of 246 Libyan healthy adult blood donors from three different Libyan regions (Tripoli, Yefren, and Tawargha) and 50 children with acute lymphoblastic leukaemia (ALL). We used polymerase chain reaction restriction length polymorphism (PCR-RFLP) and allele-specific PCR-based assays to analyse the TPMT gene for the variants *2 c.238 G>C, *3A (c.460 G>A and c.719 A>G), *3B (c.460 G>A), and *3C (c.719 A>G). RESULTS: Our results show that the TPMT variants associated with low enzymatic activity were detected in 3.25% (8 in 246) of adult Libyan individuals and the frequency of total mutant alleles was 1.63%. Heterozygous genotypes were TPMT*3A in three subjects (0.61%) and TPMT*3C in five subjects (1.02%). No TPMT*2 and TPMT*3B allelic variants and no homozygous or compound heterozygous mutant alleles were detected. The normal allele (wild-type) was found in 98.4% of the adult individuals studied. No mutant alleles were detected among the 50 children who had ALL. CONCLUSIONS: We report on the presence of the TPMT*3C and *3A mutant alleles in the Libyan population. Therefore, monitoring the patients to be treated with doses of thiopurine drugs for TPMT variants is worthwhile to avoid the development of severe myelosuppression.

Evaluation of thiopurine methyltransferase genotyping and enzyme activity detection in treatment of patients with inflammatory bowel disease / 中华消化杂志

Objective To assess the predictive value of thiopurine methyltransferase genotyping and enzyme activity in relation to side effects in patients with inflammatory bowel disease (IBD) who were treated with azathioprine (AZA). Methods One hundred and eleven IBD patients (26 with ulcerative colitis and 86 with Cronh's disease) with indication of AZA administration between April 2004 and Dec. 2009 were enrolled. All patients received 2 mg/kg of AZA daily. Polymerase chain reaction and high performance liquid chromatography were used to genotype the TPMT * 2, * 3A, * 3B, * 3C and to detect TPMT activity, respectively. The association of TPMT genotype and activity with side effects was analyzed in patients treated with AZA for 24 weeks or more, or in those discontinued AZA because of adverse effects. Results Adverse effects were reported in 38(33. 9%) patients, the most frequent being myelosuppression (20. 5%). The frequency of TPMT * 3C heterozygous mutation was 0. 9% (1/112). The TPMT activity was (12. 9±4. 8) U/ml RBC with unimodal distribution. One patient with TPMT * 3C heterozygous mutation developed myelosuppression at the 4th week after AZA treatment. The TPMP genotype myelosuppression patients. Conclusions TPMT genotype mutation and low enzyme activity can be used to predict myelosuppression with high specifically and low sensitivity. In patients treated with AZA, co-administration of 5-ASA results in a high frequency of myelosuppression with no effect on TPMT activity.