Thiopurine S-methyltransferase genotype and the use of thiopurines in paediatric inflammatory bowel disease Greek patients

Saudi consensus guidance for the diagnosis and management of inflammatory bowel disease in children and adolescents

ABSTRACT

The management of inflammatory bowel disease (IBD) in children and adolescents is challenging. Clear evidence-based guidelines are required for this population. This article provides recommendations for managing IBD in Saudi children and adolescents aged 6-19 years, developed by the Saudi Ministry of Health in collaboration with the Saudi Society of Clinical Pharmacy and the Saudi Gastroenterology Association. All 57 guideline statements are based on the most up-to-date information for the diagnosis and management of pediatric IBD.

The Role of Pharmacogenetics in the Therapeutic Response to Thiopurines in the Treatment of Inflammatory Bowel Disease: A Systematic Review

This study focuses on the use of thiopurines for treating inflammatory bowel diseases (IBD). These drugs undergo enzymatic changes within the body, resulting in active and inactive metabolites that influence their therapeutic effects. The research examines the role of genetic polymorphisms in the enzyme thiopurine S-methyltransferase (TPMT) in predicting the therapeutic response and adverse effects of thiopurine treatment. The TPMT genotype variations impact the individual responses to thiopurines. Patients with reduced TPMT activity are more susceptible to adverse reactions (AEs), such leukopenia, hepatotoxicity, pancreatitis, and nausea, which are common adverse effects of thiopurine therapy. The therapeutic monitoring of the metabolites 6-thioguanine nucleotides (6-TGN) and 6-methyl mercaptopurine (6-MMP) is proposed to optimize treatment and minimize AEs. Patients with higher 6-TGN levels tend to have better clinical responses, while elevated 6-MMP levels are linked to hepatotoxicity. Genotyping for TPMT before or during treatment initiation is suggested to tailor dosing strategies and enhance treatment efficacy while reducing the risk of myelosuppression. In conclusion, this study highlights the importance of considering genetic variations and metabolite levels in optimizing thiopurine therapy for IBD patients, focusing on balance therapeutic efficacy with the prevention of adverse effects and contributing to personalized treatment and better patient outcomes.

Drug-Related Adverse Events Necessitating Treatment Discontinuation in Pediatric Inflammatory Bowel Disease Patients

OBJECTIVES

Inflammatory bowel disease (IBD) requires long-term drug therapy in most patients, posing a risk for adverse drug events with the need for discontinuation. In this study, we investigated adverse events (AE) necessitating drug discontinuation in pediatric and adolescent IBD patients.

METHODS

We used data prospectively collected from IBD patients below the age of 18 enrolled in the Swiss Inflammatory Bowel Disease Cohort Study (SIBDCS), namely demographic variables, medical characteristics, drug treatments, and related AE. We analyzed the frequency, type, and risk factors for AE necessitating drug discontinuation.

RESULTS

A total of 509 pediatric IBD patients fulfilled the inclusion criteria of which 262 (51.5%) were diagnosed with Crohn disease (CD), 206 (40.5%) with ulcerative colitis (UC), and 41 (8%) with IBD-unclassified (IBD-U). In total, 132 (25.9%) presented with at least 1 drug-related AE that required drug cessation. Immunomodulators [methotrexate 29/120 (24.2%), azathioprine 57/372 (15.3%)] followed by tumor necrosis factor (TNF)-alpha antagonists [adalimumab 8/72 (11.1%), infliximab 22/227 (9.7%)] accounted for the highest proportions of AE necessitating treatment discontinuation. Treatment schemes with at least 3 concomitant drugs significantly amplified the risk for development of drug-related AE [odds ratio = 2.50, 95% confidence interval (1.50-4.17)] in all pediatric IBD patients.

CONCLUSIONS

Drug-related AE necessitating discontinuation are common in pediatric and adolescent IBD patients. Caution needs to be taken in the case of concomitant drug use.

Associations between the NUDT15 R139C polymorphism and susceptibility to thiopurine-induced leukopenia in Asians: a meta-analysis

Background and aim

Despite several studies being conducted to examine the associations between the NUDT15 R139C polymorphism and thiopurine-induced leukopenia in the Asian population, the results remain inconsistent. This meta-analysis determined the risk of thiopurine-induced leukopenia conferred by the NUDT15 R139C polymorphism.

Materials and methods

All eligible studies published in English up to May 2018 were identified by searching PubMed, Web of Science, Embase, and the Cochrane Library. Pooled OR and 95% CI were calculated using fixed- or random-effect model.

Results

In all, total of 14 studies containing 918 patients and 2,341 controls were included; of these, 8 studies concerned inflammatory bowel disease (IBD) and 4 concerned acute lymphoblastic leukemia (ALL). Overall, the results indicated that the NUDT15 R139C polymorphism was associated with leukopenia induced by thiopurines (OR =9.04, 95% CI 6.05–13.50, P<0.001 for the dominant model; OR =24.26, 95% CI 11.38–51.71, P<0.001 for the recessive model; OR =7.60, 95% CI 4.97–11.61, P<0.001 for the CT vs TT model; OR =38.47, 95% CI 17.78–83.24, P<0.001 for the CC vs TT model). In subgroup analyses, significant associations were found among patients with IBD (OR =7.57, 95% CI 5.16–11.12, P<0.001 for the dominant model), ALL (OR =13.13, 95% CI 3.43–50.23 P<0.001 for the dominant model), and other diseases (OR =31.22, 95% CI 1.20–814.07, P=0.04 for the dominant model). In addition, the R139C variant was strongly associated with early (<8 weeks) (OR =15.53, 95% CI 7.91–30.50, P<0.001 for the dominant model) and late leukopenia (≥8 weeks) (OR =2.92, 95% CI 2.01–4.24, P<0.001 for the dominant model). Moreover, these findings were sufficiently robust when studies without Hardy–Weinberg equilibrium test were excluded.

Conclusion

This meta-analysis verified the strong association between the NUDT15 R139C polymorphism and thiopurine-induced leukopenia (both early and late leukopenia) in an Asian population with IBD, ALL, and other diseases. NUDT15 R139C genotyping should be prioritized to predict leukopenia among Asians.

Comparison of TPMT and NUDT15 polymorphisms in Chinese patients with inflammatory bowel disease

AIM

To observe gene polymorphisms of TPMT and NUDT15, and compare their predictive value for azathioprine (AZA)-induced leukopenia in inflammatory bowel disease (IBD).

METHODS

This study enrolled 219 patients diagnosed with IBD in Xiangya Hospital, Central South University, Changsha, China from February 2016 to November 2017. Peripheral blood of all patients was collected to detect their genotypes of TPMT and NUDT15 by pyrosequencing at the Department of Clinical Pharmacology, Hunan Key Laboratory of Pharmacogenetics, Xiangya Hospital. Eighty patients were treated with AZA according to the disease condition. During the first month, patients who received AZA underwent routine blood tests and liver function tests once a week. The endpoint of the study was leukopenia induced by AZA. By analyzing patient characteristics, genotypes and leukopenia induced by drug use, we found the risk factors associated with AZA-induced leukopenia.

RESULTS

There were 219 patients with IBD (160 men and 59 women), including 39 who were confirmed with ulcerative colitis (UC), 176 with Crohn’s disease (CD) and 4 with undetermined IBD (UIBD). There were 44 patients (20.1%) with mutant genotype of NUDT15 (C/T); among them, 16 received AZA, and 8 (50%) developed leukopenia. There were 175 patients (79.7%) with wild genotype of NUDT15 (C/C); among them, 64 received AZA, and 11 (17.2%) developed leukopenia. A significant difference was found between NUDT15 C/T and its wild-type C/C (P = 0.004). There were only 3 patients with TPMT mutant genotype of A/G (1.4%) who participated in the research, and 1 of them was treated with AZA and developed leukopenia. The remaining 216 patients (98.6%) were found to bear the wild genotype of TPMT (A/A); among them, 79 patients received AZA, and 18 (22.8%) developed leukopenia, and there was no significant difference from those with A/G (P = 0.071). The frequency of TPMT mutation was 1.4%, and NUDT15 mutation rate was significantly higher and reached 20.1% (P = 0.000). Therefore, NUDT15 gene polymorphism was obviously a better biomarker than TPMT gene polymorphism in the prediction of AZA-induced leukopenia.

CONCLUSION

Mutation rate of NUDT15 in Chinese IBD patients is higher than that of TPMT. NUDT15 polymorphism is a better predictor for AZA-induced leukopenia than TPMT polymorphism.

Frequency of thiopurine methyltransferase mutation in patients of Mediterranean area with inflammatory bowel disease and autoimmune disorders

BACKGROUND AND AIMS

Few studies exist on the frequency of thiopurine methyltransferase (TPMT) mutation in patients from Southern Europe. We aimed to evaluate the frequency of TPMT mutation in a homogeneous Sicilian cohort of patients with inflammatory bowel disease (IBD), autoimmune and hematological disorders, the rate of thiopurine-related adverse events, and its association with the TPMT genotype.

RESULTS

Among 105 patients with IBD, 45 with autoimmune disease, and 34 with hematologic diseases, the homozygous TPMT variant genotype was found in one patient only (0.5%), while the heterozygous TPMT genotype was identified in 8 patients (4.3%). In patients with IBD, leukopenia was observed in ten patients: one had the homozygous TPMT genotype, one the heterozygous genotype, and the remaining eight the wild type genotype.

CONCLUSIONS

The frequency of TPMT mutation in a Mediterranean area was low. TPMT genotyping is not a sensitive tool for predicting thiopurine-induced leukopenia.

Pharmacogenomics in Pediatric Oncology: Review of Gene-Drug Associations for Clinical Use

During the 3rd congress of the European Society of Pharmacogenomics and Personalised Therapy (ESPT) in Budapest in 2015, a preliminary meeting was held aimed at establishing a pediatric individualized treatment in oncology and hematology committees. The main purpose was to facilitate the transfer and harmonization of pharmacogenetic testing from research into clinics, to bring together basic and translational research and to educate health professionals throughout Europe. The objective of this review was to provide the attendees of the meeting as well as the larger scientific community an insight into the compiled evidence regarding current pharmacogenomics knowledge in pediatric oncology. This preliminary evaluation will help steer the committee’s work and should give the reader an idea at which stage researchers and clinicians are, in terms of personalizing medicine for children with cancer. From the evidence presented here, future recommendations to achieve this goal will also be suggested.

Thiopurine monitoring in children with inflammatory bowel disease: a systematic review

AIMS

The aim was to systematically review the evidence on the clinical usefulness of thiopurine metabolite and white blood count (WBC) monitoring in the assessment of clinical outcomes in children with inflammatory bowel disease (IBD).

METHODS

Medline, Embase, Cochrane Central Register of controlled trials and http://www.clinicaltrials.gov were screened in adherence to the PRISMA statement by two independent reviewers for identification of eligible studies. Eligible studies were randomized controlled trials (RCTs), cohort studies and large case series of children with inflammatory bowel disease (IBD) (<18 years) who underwent monitoring of thiopurine metabolites and/or WBC.

RESULTS

Fifteen papers were identified (n = 1026). None of the eligible studies were RCTs. High 6-thioguanine nucleotide (6TGN) concentrations were not consistently associated with leucopenia. Leucopenia was not associated with achievement of clinical remission. A positive but not consistent correlation between 6TGN and clinical remission was reported. Haematological toxicity could not be reliably assessed with 6TGN measurements only. A number of studies supported the use of high 6-methylmercaptopurine ribonucleotides (6MMPR) as an indicator of hepatotoxicity. Low thiopurine metabolite concentration may be indicative of non-compliance.

CONCLUSION

Thiopurine metabolite testing does not safely predict clinical outcome, but may facilitate toxicity surveillance and treatment optimization in poor responders. Current evidence favours the combination of thiopurine metabolite/WBC monitoring and clinic follow-up for prompt identification of haematologic/hepatic toxicity safe dose adjustment, and treatment modification in cases of suboptimal clinical outcome or non-compliance. Well designed RCTs for the identification of robust surrogate markers of thiopurine efficacy and toxicity are required.

Thiopurine-methyltransferase variants in inflammatory bowel disease: Prevalence and toxicity in Brazilian patients

AIM: To analyze the prevalence of thiopurine-methyltransferase (TPMT) genotypes and their association with drug toxicity in inflammatory bowel disease (IBD) patients from southeastern Brazil.

METHODS: A total of 219 consecutive patients with IBD, of which 146 had Crohn’s disease and 73 had ulcerative colitis, regularly seen at the outpatient unit of the Division of Gastroenterology at the University Hospital Pedro Ernesto of the State University of Rio de Janeiro, a tertiary referral center, were enrolled in this study from February 2009 to January 2011. We analyzed the presence of major TPMT genetic variants (TPMT*2, *3A, *3C) in IBD patients by means of a specific allele and RFLP-PCR. Genomic DNA was isolated from peripheral blood leukocytes by proteinase-K/Sodium Dodecyl Sulfate digestion and phenol-chloroform extraction. TPMT*2 (C238G), TPMT*3A (G460A/A719G), and TPMT*3C (A719G) genotypes were detected by real-time polymerase chain reaction followed by direct sequencing with specific primers. Clinical data were systematically recorded, and correlated with the genotype results.

RESULTS: The distribution of the selected TPMT gene polymorphism TPMT*2 (C238G), TPMT*3A (G460A/A719G), and TPMT*3C (A719G) genotypes was 3.6%, 5.4%, and 7.7% of the patients, respectively. Among the side effects recorded from patients taking azathioprine, 14 patients presented with pancreatitis and/or an elevation of pancreatic enzymes, while 6 patients had liver toxicity, and 2 patients exhibited myelosuppression/neutropenia. TPMT polymorphisms were detected in 37/219 patients (8 heterozygous for *2, 11 heterozygous for *3A, and 18 heterozygous for *3C). No homozygotic polymorphisms were found. Despite the prevalence of the TPMT*3C genotype, no differences among the genotype frequencies were significant. Although no association was detected regarding myelotoxicity or hepatotoxicity, a trend towards the elevation of pancreatic enzymes was observed for TPMT*2 and TPMT*3C genotypes.

CONCLUSION: The prevalence of TPMT genotypes was high among Brazilian patients. Variants genes *2 and *3C may be associated with azathioprine pancreatic toxicity in a IBD southeastern Brazilian population.

Management of pediatric ulcerative colitis: joint ECCO and ESPGHAN evidence-based consensus guidelines

BACKGROUND AND AIMS

Pediatric ulcerative colitis (UC) shares many features with adult-onset disease but there are some unique considerations; therefore, therapeutic approaches have to be adapted to these particular needs. We aimed to formulate guidelines for managing UC in children based on a systematic review (SR) of the literature and a robust consensus process. The present article is a product of a joint effort of the European Crohn's and Colitis Organization (ECCO) and the European Society for Paediatric Gastroenterology, Hepatology, and Nutrition (ESPGHAN).

METHODS

A group of 27 experts in pediatric IBD participated in an iterative consensus process including 2 face-to-face meetings, following an open call to ESPGHAN and ECCO members. A list of 23 predefined questions were addressed by working subgroups based on a SR of the literature.

RESULTS

A total of 40 formal recommendations and 68 practice points were endorsed with a consensus rate of at least 89% regarding initial evaluation, how to monitor disease activity, the role of endoscopic evaluation, medical and surgical therapy, timing and choice of each medication, the role of combined therapy, and when to stop medications. A management flowchart, based on the Pediatric Ulcerative Colitis Activity Index (PUCAI), is presented.

CONCLUSIONS

These guidelines provide clinically useful points to guide the management of UC in children. Taken together, the recommendations offer a standardized protocol that allows effective, timely management and monitoring of the disease course, while acknowledging that each patient is unique.

Thiopurine methyltransferase genotype and thiopurine S-methyltransferase activity in Greek children with inflammatory bowel disease

BACKGROUND

Azathioprine (AZA) and 6-mercaptopurine (6MP) are used in the treatment of pediatric inflammatory bowel disease (IBD). Genetic variations in thiopurine S-methyltranfarase (TPMT) gene have been correlated with enzyme activity and with the occurrence of adverse events to AZA and 6MP. The aim of the present study was to examine the sensitivity and specificity of TPMT genotyping for TPMT enzymatic activity, reducing harm from thiopurine by pretesting, and the association of thiopurine toxicity with TPMT status in children with IBD.

METHODS

TPMT red blood cell (RBC) activity was measured by using a radiochemical method and genotype was determined for the TPMT alleles *2, *3A, *3B and *3C in 108 thiopurinetreated pediatric IBD patients with a mean age of 11.3 years (range 3-16).

RESULTS

Significant TPMT activity differences between wild-type and heterozygous and homozygous mutated subjects were observed. We divided TPMT activity into three categories according to frequency distribution: low (16.67%), intermediate (25.92%) and high (57.41%). The whole population included a total of 77.78% of homozygous wild-type subjects, 15.74% heterozygous variants, 1.85% homozygous variants and five (4.63%) compound heterozygous variant TPMT*3B/*3C. The overall concordance rate between TPMT genotypes and phenotypes was 88.2%. Seven carriers of at least one variant allele and low or intermediate TPMT activity developed adverse effects.

CONCLUSIONS

Our findings suggest that carriers of at least one variant allele and both intermediate and absent TPMT activity have an increased risk of developing thiopurine-induced myelotoxicity compared with individuals with normal genotype and TPMT activity.

Pharmacogenetics and individualized therapy in children: immunosuppressants, antidepressants, anticancer and anti-inflammatory drugs

Pharmacogenetic polymorphisms that change the amino acid sequences in coding regions only account for part of the interindividual differences in disease susceptibility and drug response. Additional pharmacogenomic and epigenetic factors are also involved. In children, pharmacogenetic studies are limited, although it has been clear for many years that the interactions between developmental patterns of drug-metabolizing enzymes and transporters have a major impact on dose exposure with age-specific dosage requirements. This article will analyze the factors affecting variability in drug response in children and focus on the pharmacogenetic polymorphisms of immunosuppressants, antidepressants, anticancer and anti-inflammatory drugs. Additional pharmacogenetic and epigenetic studies should be performed to allow the individualization of therapy in children.

APEX microarray panel for genotyping polymorphisms in cancer chemotherapy and estimation frequencies in a Slovak population

Aim: Many studies focus on monitoring response to chemotherapy, adverse effects and prediction of therapeutic effects, which depend on individual gene variability. The amount of various polymorphisms in genes involved in the folate cycle, and other metabolic pathways involved in the metabolism of chemotherapeutic drugs, are an essential topic of such studies. This work focuses on the design and establishment of a pharmacogenetically relevant panel, which could be applied to the rapid genotyping of patients treated with thiopurines, 5-fluorouracil, methotrexate, irinotecan and glucocorticoids. Materials & methods: A total of 97 variations in 36 genes associated with side effects of chemotherapeutic treatment were selected. Of these, 94 SNPs were genotyped by the arrayed primer extension (APEX; Asper Biotech Ltd) microarray method or direct sequencing. Variations of tandem repeats or gene deletions were genotyped by capillary electrophoresis and PCR detection. A total of 300 DNA samples from healthy volunteers were tested to estimate genotype frequencies for a Slovak population. All data were checked for Hardy–Weinberg equilibrium and genetic linkage between variations. Results: We designed an APEX microarray for genotyping pharmacologically relevant polymorphisms in patients undergoing chemotherapy. We estimated genotype frequencies for all 97 polymorphisms testing 300 individuals from the Slovak population, which may also serve as an estimate of central European frequencies. These data also allowed for the testing of genetic linkage between loci. Many of the determined genotype frequencies in this study were in similar ranges found in other European populations but four SNPs, rs11760837 (p = 0.018), rs1801265 (p = 0.0375), rs1801394 (p = 0.0066) and rs182455 (p = 0.0083), demonstrated stronger deviation. Conclusion: Genetic variability in genes involved in metabolic pathways of chemotherapeutic drugs, such as methotrexate, 5-fluorouracil, thiopurines or irinotecan, is responsible for individual therapy response and development of side effects. A comprehensive approach in genotyping of numerous variants is aimed to improve individual access to patients and the selection of appropriate drugs for treatment. The APEX microarray method is a valuable tool for fast, reliable and cost-effective genotyping of variants which can be used for the typing of known variants in patients prior to treatment as well as in studies searching for new genotype–phenotype associations. The opportunity of adding additional variants during the study makes the APEX microarray technology flexible and suitable for such trials.

Original submitted 4 October 2010; Revision submitted 23 November 2010.