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The impact of thiopurine de-escalation while on vedolizumab versus continuing thiopurine therapy in ulcerative colitis (UC) is unclear. We aimed to determine the effect of thiopurine withdrawal for patients with UC in remission on vedolizumab. This multicenter randomized controlled trial recruited UC patients on vedolizumab 300 mg intravenously every 8 weeks and a thiopurine. Patients in steroid-free clinical remission for ≥6 months and endoscopic remission/improvement (Mayo endoscopic subscore ≤1) were randomized 2:1 to withdraw or continue thiopurine. Primary outcome was comparing week 48 vedolizumab trough concentrations. Secondary outcomes were clinical relapse (partial Mayo score ≥3 and fecal calprotectin >150 μg/g or increase in Mayo endoscopic subscore ≥1 from baseline), fecal calprotectin remission (<150 μg/g), C-reactive protein remission (<5 mg/L), centrally read endoscopic remission (Mayo endoscopic subscore = 0), histologic remission (Nancy index = 0), histo-endoscopic remission, and adverse events. In total, 62 patients were randomized to continue (n = 20) or withdraw (n = 42) thiopurine. At week 48, vedolizumab trough concentrations were not significantly different between continue and withdrawal groups (14.7 μg/mL, interquartile rate [IQR], 12.3–18.5 μg/mL versus 15.9 μg/mL, IQR, 10.1–22.7 μg/mL, respectively, P = 0.36). The continue group had significantly higher fecal calprotectin remission (95.0%, 19/20 versus 71.4%, 30/42; P =.03), histologic remission (80.0%, 16/20 versus 48.6%, 18/37; P =.02), and histo-endoscopic remission (75.0%, 15/20 versus 32.4%, 12/37; P =.002) than the withdrawal group. Histologic activity (hazard ratio [HR], 15.5; 95% confidence interval [CI], 1.6–146.5; P =.02) and prior anti-tumor necrosis factor exposure (HR, 6.5; 95% CI, 1.3–33.8; P =.03) predicted clinical relapse after thiopurine withdrawal. Thiopurine withdrawal did not affect vedolizumab trough concentrations. However, it may increase fecal calprotectin, histologic, and histo-endoscopic activity. Histologic activity and prior anti-tumor necrosis factor exposure may predict disease relapse on thiopurine withdrawal for patients using vedolizumab for UC. Australian and New Zealand Trial Registry, number ACTRN12618000812291. [Display omitted] [ABSTRACT FROM AUTHOR]

Background: This study evaluated the effectiveness of NUDT15 codon 139 genotyping in optimizing thiopurine treatment for inflammatory bowel disease (IBD) in Japan, using real-world data, and aimed to establish genotype-based treatment strategies. Methods: A retrospective analysis of 4628 IBD patients who underwent NUDT15 codon 139 genotyping was conducted. This study assessed the purpose of the genotyping test and subsequent prescriptions following the obtained results. Outcomes were compared between the Genotyping group (thiopurine with genotyping test) and Non-genotyping group (thiopurine without genotyping test). Risk factors for adverse events (AEs) were analyzed by genotype and prior genotyping status. Results: Genotyping test for medical purposes showed no significant difference in thiopurine induction rates between Arg/Arg and Arg/Cys genotypes, but nine Arg/Cys patients opted out of thiopurine treatment. In the Genotyping group, Arg/Arg patients received higher initial doses than the Non-genotyping group, while Arg/Cys patients received lower ones (median 25 mg/day). Fewer AEs occurred in the Genotyping group because of their lower incidence in Arg/Cys cases. Starting with < 25 mg/day of AZA reduced AEs in Arg/Cys patients, while Arg/Arg patients had better retention rates when maintaining ≥ 75 mg AZA. Nausea and liver injury correlated with thiopurine formulation but not dosage. pH-dependent mesalamine reduced leukopenia risk in mesalamine users. Conclusions: NUDT15 codon 139 genotyping effectively reduces thiopurine-induced AEs and improves treatment retention rates in IBD patients after genotype-based dose adjustments. This study provides data-driven treatment strategies based on genotype and identifies risk factors for specific AEs, contributing to a refined thiopurine treatment approach. [ABSTRACT FROM AUTHOR]

Background and Aims SELECTION is the first study to assess the impact of concomitant thiopurine and other immunomodulator [IM] use on the efficacy and safety of a Janus kinase inhibitor, filgotinib, in patients with ulcerative colitis. Methods Data from the phase 2b/3 SELECTION study were used for this post hoc analysis. Patients were randomised [2:2:1] to two induction studies [biologic-naive, biologic-experienced] to filgotinib 200 mg, 100 mg, or placebo. At Week 10, patients receiving filgotinib were re-randomised [2:1] to continue filgotinib or to switch to placebo until Week 58 [maintenance]. Outcomes were compared between subgroups with and without concomitant IM use. Results At Week 10, similar proportions of patients in the +IM and −IM groups treated with filgotinib 200 mg achieved Mayo Clinic Score [MCS] response [biologic-naive: 65.8% vs 66.9%; biologic-experienced: 61.3% vs 50.5%] and clinical remission [biologic-naive: 26.0% vs 26.2%; biologic-experienced: 11.3% vs 11.5%]. At Week 58, similar proportion of patients in the +IM and −IM groups treated with filgotinib 200 mg achieved MCS response [biologic-naive: 74.2% vs 75.0%; biologic-experienced: 45.5% vs 61.4%] and clinical remission [biologic-naive: 51.6% vs 47.4%; biologic-experienced: 22.7% vs 24.3%]. The probability of protocol-specified disease worsening during the maintenance study in patients treated with filgotinib 200 mg did not differ between +IM and −IM groups [ p  = 0.6700]. No differences were observed in the incidences of adverse events between +IM and −IM groups in the induction/maintenance studies. Conclusions The efficacy and safety profiles of filgotinib treatment in SELECTION did not differ with or without concomitant IM use. ClinicalTrials.gov identifier NCT02914522. [ABSTRACT FROM AUTHOR]

Background: Although immunomodulators are widely prescribed in patients with Crohn's disease (CD), it is unclear whether there is a difference in treatment outcomes between thiopurines and methotrexate (MTX). Objective: To compare the risk of clinical failure between thiopurines and MTX in bio-naïve patients with CD. Design: Nationwide, population-based study. Methods: We used claims data from the Korean National Health Insurance Service. After inverse probability of treatment weighting, logistic regression and Cox proportional hazard analyses were used to evaluate the risk of clinical failure in bio-naïve patients with CD treated with thiopurine (thiopurine group) or MTX (MTX group). Results: Overall, 10,296 adult and pediatric patients with CD [9912 (96.3%) and 384 (3.7%) in the thiopurine and MTX groups, respectively] were included. The odds ratios (ORs) of failure to induce remission were significantly higher in the MTX group than in the thiopurine group [adjusted OR (aOR), 1.115; 95% confidence interval (CI), 1.045–1.190; p = 0.001]. However, the opposite result was observed only in patients without concomitant steroid use: the MTX group had a lower risk of induction failure than the thiopurine group (aOR, 0.740; 95% CI, 0.673–0.813; p < 0.001). The risk of overall maintenance failure was higher in the MTX group than in the thiopurine group [adjusted hazard ratio (aHR), 1.117; 95% CI, 1.047–1.191; p = 0.001]. The risk of overall maintenance failure was higher in the standard-dose MTX group than in the low-dose MTX group (aHR, 1.296; 95% CI, 1.134–1.480; p < 0.001). There was no significant difference in the risk of maintenance failure according to the administration route of MTX. Conclusion: Thiopurine is more effective than MTX in inducing and maintaining remission in bio-naïve patients with CD; however, the concomitant use of steroids influences inducing remission. Plain language summary: Differences in treatment efficacy between thiopurine and methotrexate in patients with Crohn's disease who were not treated with biologics Immunomodulators (IMMs) used in the treatment of Crohn's disease (CD) include medications such as thiopurine and methotrexate (MTX). Although IMMs are widely prescribed for patients with CD, it remains unclear whether treatment outcomes differ according to the specific types and dosages of IMMs and administration routes of MTX. In this study, we investigated the risk of treatment failure between thiopurines and MTX in CD patients not undergoing biologic treatment. Patients treated with MTX had a higher risk of maintenance failure than those treated with thiopurines. There was no difference in the risk of treatment failure according to the dosage of thiopurine. However, the risk of maintenance failure was higher in patients receiving standard-dose MTX than in those receiving low-dose MTX. There was no difference in the risk of maintenance failure according to the administration route of MTX. Our study enriches the knowledge regarding the treatment efficacy of thiopurines and MTX for patients with CD and may help clinicians develop appropriate treatment plans. [ABSTRACT FROM AUTHOR]

Background Thiopurines such as mercaptopurine (MP) are widely used to treat acute lymphoblastic leukemia (ALL). Thiopurine-S-methyltransferase (TPMT) and Nudix hydrolase 15 (NUDT15) inactivate thiopurines, and no-function variants are associated with drug-induced myelosuppression. Dose adjustment of MP is strongly recommended in patients with intermediate or complete loss of activity of TPMT and NUDT15. However, the extent of dosage reduction recommended for patients with intermediate activity in both enzymes is currently not clear. Methods MP dosages during maintenance were collected from 1768 patients with ALL in Singapore, Guatemala, India, and North America. Patients were genotyped for TPMT and NUDT15, and actionable variants defined by the Clinical Pharmacogenetics Implementation Consortium were used to classify patients as TPMT and NUDT15 normal metabolizers (TPMT/NUDT15 NM), TPMT or NUDT15 intermediate metabolizers (TPMT IM or NUDT15 IM), or TPMT and NUDT15 compound intermediate metabolizers (TPMT/NUDT15 IM/IM). In parallel, we evaluated MP toxicity, metabolism, and dose adjustment using a Tpmt / Nudt15 combined heterozygous mouse model (Tpmt +/−/ Nudt15 +/−). Results Twenty-two patients (1.2%) were TPMT/NUDT15 IM/IM in the cohort, with the majority self-reported as Hispanics (68.2%, 15/22). TPMT/NUDT15 IM/IM patients tolerated a median daily MP dose of 25.7 mg/m2 (interquartile range = 19.0-31.1 mg/m2), significantly lower than TPMT IM and NUDT15 IM dosage (P  < .001). Similarly, Tpmt +/−/ Nudt15 +/− mice displayed excessive hematopoietic toxicity and accumulated more metabolite (DNA-TG) than wild-type or single heterozygous mice, which was effectively mitigated by a genotype-guided dose titration of MP. Conclusion We recommend more substantial dose reductions to individualize MP therapy and mitigate toxicity in TPMT/NUDT15 IM/IM patients. [ABSTRACT FROM AUTHOR]

Silver nitrate reacts with 6‐methylmercaptopurine riboside (6‐MMPR) in aqueous solution containing methanol and dimethyl sulfoxide at room temperature to give a colourless crystalline complex, namely, bis(6‐methylmercaptopurine riboside‐κN7)(nitrato‐κ2O,O′)silver(I) 2.32‐hydrate, [Ag(NO3)(C11H14N4O4S)2]·2.32H2O. The crystal structure, determined from synchrotron diffraction data, shows a central AgI ion on a crystallographic twofold rotation axis, coordinated in an almost linear fashion by two 6‐MMPR ligands via atom N7 (purine numbering), with the nitrate counter‐ion loosely coordinated as a bidentate ligand, forming a discrete molecular complex as an approximate dihydrate. The complex and water molecules are connected in a three‐dimensional network by hydrogen bonding. [ABSTRACT FROM AUTHOR]

Background: Thiopurines are commonly used to treat inflammatory bowel disease but withdrawal due to side effects are common. Thioguanine has been suggested to be better tolerated than conventional thiopurines. Objectives: We studied drug-survival of low dose of thioguanine in real-life clinical practice in comparison to conventional thiopurines. Design: Retrospective observational study. Methods: All patients born 1956 and later, and who at least once started thiopurine treatment between 2006 and 2022 were included. A medical chart review was performed that noted drug-survival for every thiopurine treatment attempt. The Mantel–Cox rank test was used to test differences in drug-survival for different thiopurines. Blood chemistry analysis and faecal calprotectin levels were registered for the first 5 years of treatment. Results: In the study population, there was 379 initiated thiopurine treatments (210 for Crohn's disease and 169 for ulcerative colitis) in 307 patients with inflammatory bowel disease (IBD). Low-dose thioguanine (median dose 11 mg; 25–75th percentile 7–19 mg) had been initiated in 31 patients. Overall, when including all thiopurine attempts, thioguanine had the longest drug-survival [Mantel–Cox rank test: thioguanine versus azathioprine p = 0.014; thioguanine versus 6-mercaptopurine (6-MP) p < 0.001]. For second-line thiopurine treatment thioguanine had longer drug-survival than 6-MP (Mantel–Cox rank test: p = 0.006). At 60 months, 86% of the patients who started low-dose thioguanine were still on treatment compared to 42% of the patients who started 6-MP (p = 0.022). The median 6-thioguanine nucleotide levels in patients treated with thioguanine was 364 pmol/8 × 108. Patients on thioguanine treatment showed significantly lower values of median mean corpuscular volume at follow-up than patients treated with azathioprine and 6-MP. Patients treated with 6-MP showed significantly lower levels of FC in the third year of treatment compared to patient treated with azathioprine (59 versus 109 µg/g; p = 0.023), but there was no significant difference in FC levels for thioguanine compared to azathioprine (50 versus 109 µg/g; p = 0.33). Conclusion: Treatment with a low dose of thioguanine is well-tolerated in patients with IBD and had a significantly higher drug-survival than conventional thiopurines. Plain language summary: Low-dose of the immunomodulator drug thioguanine are well tolerated by patients with inflammatory bowel disease Thiopurines are commonly used to treat inflammatory bowel disease but it is common that patients end treatment due to side-effects. The thiopurine thioguanine has been suggested to be better tolerated than other thiopurines. We aimed to study if a low-dose of thioguanine had been tolerated better and used longer than other thiopurines in patients with inflammatory bowel disease at our clinic. In the study population there was 379 initiated thiopurine treatments in 307 patients with inflammatory bowel disease. Among those patients a low-dose thioguanine had been initiated in 31 patients. Overall, when including all thiopurine attempts, thioguanine had longest drug-survival of all thiopurines. For second line thiopurine treatment thioguanine had longer drug-survival than the thiopurine 6-mercaptopurine that are usually used as second line thiopurine treatment. At 60 months, 86% of the patients who started low dose thioguanine was still on treatment compared to 42% of the patients who started 6-mercaptopurine.There was a similar response on inflammatory markers the first five years from starting treatment with thioguanines compared to conventional used thiopurines. We conclude that treatment with a low-dose of thioguanine is well tolerated in patients with inflammatory bowel disease and have a significantly higher drug survival than conventional thiopurines. [ABSTRACT FROM AUTHOR]

Recent clinical data have identified infant patients with lethal ITPA deficiencies. ITPA is known to modulate ITP concentrations in cells and has a critical function in neural development which is not understood. Polymorphism of the ITPA gene affects outcomes for both ribavirin and thiopurine based therapies and nearly one third of the human population is thought to harbor ITPA polymorphism. In a previous site-directed mutagenesis alanine screen of the ITPA substrate selectivity pocket, we identified the ITPA mutant, E22A, as a gain-of function mutant with enhanced ITP hydrolysis activity. Here we report a rational enzyme engineering experiment to investigate the biochemical properties of position 22 ITPA mutants and find that the E22D ITPA has two- and four-fold improved substrate selectivity for ITP over the canonical purine triphosphates ATP and GTP, respectively, while maintaining biological activity. The novel E22D ITPA should be considered as a platform for further development of ITPA therapies. [ABSTRACT FROM AUTHOR]

The usefulness of NUDT15 genotyping as a pharmacogenomic test for thiopurine has been established. The first such test developed to date, NUDT15 genotyping was approved for reimbursement in Japan in February 2019 for all indicated patients. We retrospectively examined claims data in Japan and confirmed that the proportion of patients who undergo genotyping before initiating a new thiopurine regimen has increased; furthermore, genotyping has improved the rate of treatment continuation and reduced on-treatment hospitalization. However, the genotyping rate before thiopurine induction was >50% for patients with inflammatory bowel disease and

Synthesis of new nido-carborane-containing 6-thiopurines and thioguanines based on nucleophilic substitution of the chlorine atom in the specially synthesized chloroacetyl derivative of 3-amino-nido-carborane by the action of 6-thiopurine or thioguanine in the presence of sodium hydride in ethanol was developed. The resulting 6-thiopurine derivatives containing a nido-carborane moiety and unsubstituted at the position 9 are of interest as potential biologically active compounds, boron delivery agents to tumor cells, and as the basis for nido-carborane-containing nucleosides. [ABSTRACT FROM AUTHOR]

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Background: There are conflicting data as to whether co-treatment with 5-aminosalicylic acid (5-ASA) in patients with inflammatory bowel disease (IBD) under azathioprine (AZA) or 6-mercaptopurine (6-MP) therapy may influence 6-thioguanine nucleotide (6-TGN) concentrations, and whether this combination puts patients at risk of side-effects. The aim of the study was to determine 6-TGN levels in patients treated with AZA/6-MP, either alone or in combination with 5-ASA. Methods: Available blood samples from patients treated with AZA or 6-MP were retrieved from the Swiss IBD Cohort Study (SIBDCS). The eligible individuals were divided into 2 groups: those with vs. without 5-ASA co-medication. Levels of 6-TGN and 6-methylmercaptopurine ribonucleotides (6-MMPR) were determined and compared. Potential confounders were compared between the groups, and also evaluated as potential predictors for a multivariate regression model. Results: Of the 110 patients enrolled in this analysis, 40 received concomitant 5-ASA at the time of blood sampling. The median 6-TGN levels in patients with vs. those without 5-ASA co-treatment were 261 and 257 pmol/8×108 erythrocytes, respectively (P=0.97). Likewise, there were no significant differences in 6-MMPR levels (P=0.79). Through multivariate analysis, 6-TGN levels were found to be significantly higher in non-smokers, patients without prior surgery, and those without signs of stress-hyperarousal. Conclusions: Blood concentrations of 6-TGN and 6-MMPR did not differ between patients with vs. those without 5-ASA co-treatment. Our data warrant neither more frequent lab monitoring nor dose adaptation of AZA in patients receiving concomitant 5-ASA treatment. [ABSTRACT FROM AUTHOR]

Objective·To study whether mutations at the I72 site of phosphoribosyl pyrophosphate synthetase 1 (PRPS1) can induce resistance in acute lymphoblastic leukemia (ALL) cells to thiopurine chemotherapy drugs 6-mercaptopurine (6-MP) and 6-thioguanine (6-TG), and explain their mechanisms of action.Methods·The PRPS1 gene mutations (I72F, R177S and V316L) found in clinical practice and PRPS1 gene mutations (V208A and V289A) present in two ALL cell lines (KOPN72bi and RS4;11) were constructed into the vector pGV303 fused with green fluorescent protein (GFP), respectively. The PRPS1 A190T mutation that has been proven to be resistant to thiopurine chemotherapy drugs was used as the positive control, and the empty vector pGV303 (Vector), PRPS1 wild-type (WT) and PRPS1 I72V were used as the negative controls. The various mutants of PRPS1 were transiently transfected into HEK-293T cells (referred to as 293T cells), and the expression of these exogenous PRPS1 was detected by Western blotting. The half maximal inhibitory concentration (IC50) of 6-MP or 6-TG on the above 293T cell lines transiently transfected with PRPS1 mutants was detected and calculated by drug sensitivity experiments. Subsequently, in addition to PRPS1 I72F and I72V, multiple mutations I72M, I72L, I72N, I72S and I72T were constructed into the vector pGV303, respectively, by changing the isoleucine (I) at position 72 into other amino acids. The various mutants were transiently transfected into 293T cells, respectively, and the protein expression of each mutant and IC50 values of 6-MP or 6-TG were detected by Western blotting and drug sensitivity experiments. PRPS1 WT, I72F, I72V, A190T and pGV303 vectors were transfected into REH cell lines by lentivirus infection, and GFP-positive cells were sorted by flow cytometry to obtain cells with stable expression of PRPS1 mutants. The protein expression of each mutant in REH cells and IC50 values of 6-MP or 6-TG were detected by Western blotting and drug sensitivity experiments to verify the results of drug sensitivity experiments obtained by 293T cells. Annexin V/DAPI double staining was used to evaluate the apoptosis of each REH cell line, and Western blotting was used to detect the levels of DNA damage-related proteins [phosphorylation at S139 of histone H2AX (phosphorylated H2AX-S139, γ-H2AX), phosphorylated check point kinase 2 (pCHK2)], and apoptosis-related protein cleaved poly (ADP-ribose) polymerase (cleaved PARP) in each REH cell line. The diagrams of amino acid residues and spatial conformations of I72 locus, I72V and I72F were predicted and drawn through three-dimensional imaging and PyMOL software by using the crystal structure data of PRPS1-numbered 2HCR (PDB code 2HCR) in the PDB (Protein Data Bank) database.Results·Western blotting results showed that the transiently transfected exogenous PRPS1-mutated proteins were successfully expressed in 293T cells. The drug sensitivity experiment results showed that the IC50 values of 6-MP or 6-TG in 293T cells expressing PRPS1 I72F, R177S, V316L, V208A and the positive control A190T were much higher than those in cells expressing V289A and the negative control Vector, PRPS1 WT and I72V (all P =0.000). After mutating the isoleucine (I) at position 72 with other amino acids, Western blotting results showed successful expression of exogenous PRPS1-mutated proteins at position I72 after transient transfection in 293T cells. Drug sensitivity experiments revealed the IC50 values of 6-MP or 6-TG in 293T cells expressing PRPS1 I72M, I72F, I72L, I72N, I72S, I72T and positive control A190T were much higher than those in cells expressing negative control Vector, PRPS1 WT and I72V (all P=0.000). Western blotting results showed that the protein expression levels of PRPS1 WT, A190T, I72F and I72V in the REH stable cell lines constructed by lentivirus were high and similar. The drug sensitivity experiment results showed that the IC50 values of 6-MP or 6-TG in REH cells expressing PRPS1 I72F and positive control A190T were much higher than those in cells expressing negative control Vector, PRPS1 WT and I72V (all P=0.000), which was consistent with the drug sensitivity results obtained by transient transfection in 293T cells. The results of Annexin V/DAPI double staining method and the detection of DNA damage and apoptosis-related proteins by Western blotting showed that after 6-MP treatment, the DNA damage and apoptosis rates of REH cell lines expressing PRPS1 A190T and I72F were significantly lower than those of cells expressing negative control Vector, PRPS1 WT and I72V (all P=0.000). The protein structure analysis results showed that PRPS1 I72F could change the conformation of PRPS1.Conclusion·The PRPS1 I72F, R177S, V316L, V208A, I72M, I72L, I72N, I72S and I72T mutations can confer drug resistance to the thiopurine chemotherapy drugs in cells, while the PRPS1 V289A and I72V mutations do not affect cell sensitivity to the thiopurine chemotherapy drugs. The drug sensitivity experiment results in 293T cells are consistent with those in REH cells, demonstrating that 293T cells can serve as a rapid research model for detecting the resistance of PRPS1 mutations to thiopurine chemotherapy drugs. The effects of the PRPS1 I72 mutations on the resistance of the thiopurine chemotherapy drugs may be related to changes in the structure of PRPS1.

Patients with inflammatory bowel disease (IBD) are exposed to chronic systemic inflammation and are at risk for secondary malignancies. Here we review the literature on the risk of myeloid neoplasms (MN) in IBD and present the disease profiles of patients at a single institution with IBD who later developed MN, comparing them to those in the literature. No IBD characteristic was found to associate with MN disease severity, including the previously-identified association between MNs and thiopurine exposure. Of the somatic mutations identified in out cohort's MN, mutations in TET2 were most prevalent, followed by FLT3-ITD, BCR-ABL, and NPM1 mutations.

Primary hepatic lymphoma is a rare variant of non-Hodgkin's lymphoma with an incidence of 0.016% of all non-Hodgkin lymphomas. The most common histologic subtype is large diffuse B-cell lymphoma. Pathogenesis is not clearly established and undergoing immunosuppressive therapy has been proposed as a risk factor for primary hepatic lymphoma. We report an intriguing case study, featuring a 23-year-old male patient with Crohn's Disease who had been receiving a combination therapy of thiopurine and anti-TNF for 6 years and was diagnosed with primary hepatic diffuse large B-cell lymphoma.

ABSTRACTImmune-checkpoint inhibitors (ICI) are highly effective in reinvigorating T cells to attack cancer. Nevertheless, a large subset of patients fails to benefit from ICI, partly due to lack of the cancer neoepitopes necessary to trigger an immune response. In this study, we used the thiopurine 6-thioguanine (6TG) to induce random mutations and thus increase the level of neoepitopes presented by tumor cells. Thiopurines are prodrugs which are converted into thioguanine nucleotides that are incorporated into DNA (DNA-TG), where they can induce mutation through single nucleotide mismatching. In a pre-clinical mouse model of a mutation-low melanoma cell line, we demonstrated that 6TG induced clinical-grade DNA-TG integration resulting in an improved tumor control that was strongly T cell dependent. 6TG exposure increased the tumor mutational burden, without affecting tumor cell proliferation and cell death. Moreover, 6TG treatment re-shaped the tumor microenvironment by increasing T and NK immune cells, making the tumors more responsive to immune-checkpoint blockade. We further validated that 6TG exposure improved tumor control in additional mouse models of melanoma. These findings have paved the way for a phase I/II clinical trial that explores whether treatment with thiopurines can increase the proportion of otherwise treatment-resistant cancer patients who may benefit from ICI therapy (NCT05276284).

About 15% to 28% of patients treated with thiopurines experienced adverse drug reactions, such as haematological and hepatic toxicities. Some of these related to the polymorphic activity of the thiopurine S‐methyltransferase (TPMT), the key detoxifying enzyme of thiopurine metabolism. We report here a case of thiopurine‐induced ductopenia with a comprehensive pharmacological analysis on thiopurine metabolism. A 34‐year‐old woman, with a medical history of severe systemic lupus erythematosus with recent introduction of azathioprine therapy, presented with mild fluctuating transaminase blood levels consistent with a hepatocellular pattern, which evolved to a cholestatic pattern over the next weeks. A blood thiopurine metabolite assay revealed low 6‐thioguanine nucleotides (6‐TGN) level and a dramatically increased 6‐methylmercaptopurine ribonucleotides (6‐MMPN) level, together with an unfavourable [6‐MMPN:6‐TGN] metabolite ratio and a high TPMT activity. After a total of about 6 months of thiopurine therapy, a transjugular liver biopsy revealed a ductopenia, and azathioprine discontinuation led to further clinical improvement. In line with previous reports from the literature, our case supports the fact that ductopenia is a rare adverse drug reaction of azathioprine. The mechanism of reaction is unknown but may involve high 6‐MMPN blood level, due to unusual thiopurine metabolism (switched metabolism). Early therapeutic drug monitoring with measurement of 6‐TGN and 6‐MMPN blood levels may help physicians to identify patients at risk of similar duct injury. [ABSTRACT FROM AUTHOR]

Objective·To study whether mutations at the I72 site of phosphoribosyl pyrophosphate synthetase 1 (PRPS1) can induce resistance in acute lymphoblastic leukemia (ALL) cells to thiopurine chemotherapy drugs 6-mercaptopurine (6-MP) and 6-thioguanine (6-TG), and explain their mechanisms of action. Methods·The PRPS1 gene mutations (I72F, R177S and V316L) found in clinical practice and PRPS1 gene mutations (V208A and V289A) present in two ALL cell lines (KOPN72bi and RS4;11) were constructed into the vector pGV303 fused with green fluorescent protein (GFP), respectively. The PRPS1 A190T mutation that has been proven to be resistant to thiopurine chemotherapy drugs was used as the positive control, and the empty vector pGV303 (Vector), PRPS1 wild-type (WT) and PRPS1 I72V were used as the negative controls. The various mutants of PRPS1 were transiently transfected into HEK-293T cells (referred to as 293T cells), and the expression of these exogenous PRPS1 was detected by Western blotting. The half maximal inhibitory concentration (IC50) of 6-MP or 6-TG on the above 293T cell lines transiently transfected with PRPS1 mutants was detected and calculated by drug sensitivity experiments. Subsequently, in addition to PRPS1 I72F and I72V, multiple mutations I72M, I72L, I72N, I72S and I72T were constructed into the vector pGV303, respectively, by changing the isoleucine (I) at position 72 into other amino acids. The various mutants were transiently transfected into 293T cells, respectively, and the protein expression of each mutant and IC50 values of 6-MP or 6-TG were detected by Western blotting and drug sensitivity experiments. PRPS1 WT, I72F, I72V, A190T and pGV303 vectors were transfected into REH cell lines by lentivirus infection, and GFP-positive cells were sorted by flow cytometry to obtain cells with stable expression of PRPS1 mutants. The protein expression of each mutant in REH cells and IC50 values of 6-MP or 6-TG were detected by Western blotting and drug sensitivity experiments to verify the results of drug sensitivity experiments obtained by 293T cells. Annexin V/DAPI double staining was used to evaluate the apoptosis of each REH cell line, and Western blotting was used to detect the levels of DNA damage-related proteins [phosphorylation at S139 of histone H2AX (phosphorylated H2AX-S139, γ -H2AX), phosphorylated check point kinase 2 (pCHK2)], and apoptosis-related protein cleaved poly (ADP-ribose) polymerase (cleaved PARP) in each REH cell line. The diagrams of amino acid residues and spatial conformations of I72 locus, I72V and I72F were predicted and drawn through threedimensional imaging and PyMOL software by using the crystal structure data of PRPS1-numbered 2HCR (PDB code 2HCR) in the PDB (Protein Data Bank) database. Results·Western blotting results showed that the transiently transfected exogenous PRPS1-mutated proteins were successfully expressed in 293T cells. The drug sensitivity experiment results showed that the IC50 values of 6-MP or 6-TG in 293T cells expressing PRPS1 I72F, R177S, V316L, V208A and the positive control A190T were much higher than those in cells expressing V289A and the negative control Vector, PRPS1 WT and I72V (all P =0.000). After mutating the isoleucine (I) at position 72 with other amino acids, Western blotting results showed successful expression of exogenous PRPS1-mutated proteins at position I72 after transient transfection in 293T cells. Drug sensitivity experiments revealed the IC50 values of 6-MP or 6-TG in 293T cells expressing PRPS1 I72M, I72F, I72L, I72N, I72S, I72T and positive control A190T were much higher than those in cells expressing negative control Vector, PRPS1 WT and I72V (all P=0.000). Western blotting results showed that the protein expression levels of PRPS1 WT, A190T, I72F and I72V in the REH stable cell lines constructed by lentivirus were high and similar. The drug sensitivity experiment results showed that the IC50 values of 6-MP or 6-TG in REH cells expressing PRPS1 I72F and positive control A190T were much higher than those in cells expressing negative control Vector, PRPS1 WT and I72V (all P=0.000), which was consistent with the drug sensitivity results obtained by transient transfection in 293T cells. The results of Annexin V/DAPI double staining method and the detection of DNA damage and apoptosis-related proteins by Western blotting showed that after 6-MP treatment, the DNA damage and apoptosis rates of REH cell lines expressing PRPS1 A190T and I72F were significantly lower than those of cells expressing negative control Vector, PRPS1 WT and I72V (all P=0.000). The protein structure analysis results showed that PRPS1 I72F could change the conformation of PRPS1. Conclusion·The PRPS1 I72F, R177S, V316L, V208A, I72M, I72L, I72N, I72S and I72T mutations can confer drug resistance to the thiopurine chemotherapy drugs in cells, while the PRPS1 V289A and I72V mutations do not affect cell sensitivity to the thiopurine chemotherapy drugs. The drug sensitivity experiment results in 293T cells are consistent with those in REH cells, demonstrating that 293T cells can serve as a rapid research model for detecting the resistance of PRPS1 mutations to thiopurine chemotherapy drugs. The effects of the PRPS1 I72 mutations on the resistance of the thiopurine chemotherapy drugs may be related to changes in the structure of PRPS1. [ABSTRACT FROM AUTHOR]

Summary: Background: Patients established on thiopurines (e.g., azathioprine) are recommended to undergo three-monthly blood tests for the early detection of blood, liver, or kidney toxicity. These side-effects are uncommon during long-term treatment. We developed a prognostic model that could be used to inform risk-stratified decisions on frequency of monitoring blood-tests during long-term thiopurine treatment, and, performed health-economic evaluation of alternate monitoring intervals. Methods: This was a retrospective cohort study set in the UK primary-care. Data from the Clinical Practice Research Datalink Aurum and Gold formed development and validation cohorts, respectively. People age ≥18 years, diagnosed with an immune mediated inflammatory disease, prescribed thiopurine by their general practitioner for at-least six-months between January 1, 2007 and December 31, 2019 were eligible. The outcome was thiopurine discontinuation with abnormal blood-test results. Patients were followed up from six-months after first primary-care thiopurine prescription to up to five-years. Penalised Cox regression developed the risk equation. Multiple imputation handled missing predictor data. Calibration and discrimination assessed model performance. A mathematical model evaluated costs and quality-adjusted life years associated with lengthening the interval between blood-tests. Findings: Data from 5982 (405 events over 16,117 person-years) and 3573 (269 events over 9075 person-years) participants were included in the development and validation cohorts, respectively. Fourteen candidate predictors (21 parameters) were included. The optimism adjusted R2 and Royston D statistic in development data were 0.11 and 0.76, respectively. The calibration slope and Royston D statistic (95% Confidence Interval) in the validation data were 1.10 (0.84–1.36) and 0.72 (0.52–0.92), respectively. A 2-year period between monitoring blood-test was most cost-effective in all deciles of predicted risk but the gain between monitoring annually or biennially reduced in higher risk deciles. Interpretation: This prognostic model requires information that is readily available during routine clinical care and may be used to risk-stratify blood-test monitoring for thiopurine toxicity. These findings should be considered by specialist societies when recommending blood monitoring during thiopurine prescription to bring about sustainable and equitable change in clinical practice. Funding: National Institute for Health and Care Research.

Purpose: Thiopurine drugs like 6-Mercaptopurine (6MP) are the cornerstone of maintenance therapy in acute lymphoblastic leukemia (ALL). A recently described variant in alpha-ketoglutarate dependent dioxygenase (FTO) gene has been reported to play an important role in thiopurine induced myelosuppression. Methods: In this study, we genotyped a coding variant (p.Ala134Thr, rs79206939) and an intronic variant (rs16952570) of FTO in 174 Indian children (age ≤ 12 years) with ALL on maintenance phase of chemotherapy and examined correlation with the risk of thiopurine induced myelosuppression and hepatic toxicity. Results: The prevalence of FTO-rs16952570 polymorphism was 18.4% (32/174) with 142 (82%) cases having TT genotype, 26 (15%) cases with TC genotype and 6 (3.4%) cases having CC genotype. FTO-rs79206939 was absent and non-polymorphic in our study group. The mean dose of 6-MP during 36 weeks of maintenance of TT, TC and CC carriers of FTO-rs16952570 was 53.7, 53.6 and 54.1 mg/m2/day. Number of patients tolerating starting dose of 60 mg/m2/day was significantly higher in CC (50%) than TT/TC (14%) genotype carrying cases (p = 0.014). However, no statistical significance was observed for total leukocyte count (TLC), absolute neutrophil count (ANC) as well as for platelets counts in patients harboring FTO-rs16952570 TT/TC/CC genotype at 4, 8, 12, 24 and 36 weeks after start of thiopurine therapy. Further, no significant correlation was noted between number of weeks of chemotherapy interruptions or episodes of febrile neutropenia and no evidence of hepatotoxicity was found with the genotype studied. Conclusion: Polymorphism in FTO-rs16952570 did not show any correlation with thiopurine related toxicity in ALL patients. [ABSTRACT FROM AUTHOR]

Background and Aims Few populaion-based studies have investigated the long-term colectomy rates of ulcerative colitis [UC]. We aimed to assess the colectomy rates over 40 years of different therapeutic eras in a prospective population-based inception cohort from Veszprem Province, Western Hungary. Methods Patient inclusion lasted between January1, 1977, and December31, 2018. Patient follow-up ended December 31, 2020. Colectomy rates and disease course were examined in three different eras based on the time of UC diagnosis; cohort A [1977–1995], cohort B [1996–2008], and cohort C [2009–2018]. Results A total of 1370 incident UC patients were included [male 51.2%, median age at diagnosis 37 years]. Median follow-up was 17 years (interquartile range [IQR] 9–24); 87 patients [6.4%] underwent colectomy. The cumulative probability of colectomy in the total population was 2.6% (95% confidence interval [CI] 2.2-3.0), 4.2% [95% CI 3.6-4.8], 7.0% [95% CI 6.2-7.8], and 10.4% [95% CI 9.1-11.7] after 5, 10, 20, and 30 years, respectively. The proportion of extensive colitis at diagnosis increased over time [24.2%/24.3%/34.9% in cohorts A/B/C, respectively, p  = 0.001]. Overall exposure to immunomodulators [11.3%/20.9%/34.4% in cohorts A/B/C, respectively, p  <0.001], as well as the probability for biologic therapy initiation increased over time (0%/3.3% [95% CI 2.6-4.0]/13.9% [95% CI 12.1-15.7], p  <0.001). There were no statistically significant differences in the cumulative probability of colectomies between cohorts A/B/C: 1.7% [95% CI 1.0-2.4], 2.5% [95% CI 1.9-3.1], and 3.7% [95% CI 2.7-4.7] after 5 years; 3.5% [95% CI 2.5-4.5], 4.2% [95% CI 3.4-5.0], and 4.5% [95% CI 3.3-5.7] after 10 years; and 7.5% [95% CI 6.1-8.9] and 6.3% [95% CI 5.2-7.4] in cohorts A/B after 20 years [log-rank = 0.588]. Extensive colitis (hazard ratio [HR] 2.24, 95% CI 1.55-3.23) and continuous active disease activity [HR 6.36, 95% CI 3.46-11.67] were independent predictors for colectomy. Conclusion No differences in colectomy rates have been observed in the incident UC patients over 40 years despite increasing use of immunomodulators and biologic therapies. [ABSTRACT FROM AUTHOR]

Abstract Background and Aim Thiopurines are recommended for maintenance of steroid‐free remission (SFR) in inflammatory bowel disease (IBD). Thiopurine metabolite monitoring (MM) is increasingly used in the West but remains novel in Singapore, with limited information on its therapeutic and economic benefits. Hence, this study aims to investigate MM's clinical utility and its impact on healthcare resource utilization in Singaporean IBD patients. Methods A retrospective observational study was conducted at Singapore General Hospital outpatient IBD Centre. Patients with IBD, baseline MM during 2014–2017, and weight‐based thiopurine doses for ≥4 weeks were followed up for 1 year. Actions were taken to optimize therapy, and metabolite levels before and after the first action were documented. Outcomes assessed included SFR, no therapy escalation or surgery, healthcare resource utilization, and direct healthcare costs. Results Ninety IBD patients (50 Crohn's disease, 40 ulcerative colitis) were included. Among them, 40% had baseline metabolite levels within therapeutic range, 31.1% sub‐therapeutic, 21.1% supra‐therapeutic, and 7.8% shunters. Repeated MM with subsequent dose optimization helped 67.2% of patients achieve therapeutic levels after 1 year. Overall, 87.8% of patients achieved SFR and 90% had no therapy escalation or surgery. Despite greater outpatient visits and laboratory investigations with MM, the median total healthcare costs at 1 year only increased marginally (S$6407.66 [shunters] vs S$5215.20 [supra‐therapeutic] vs S$4970.80 [sub‐therapeutic] vs S$4370.48 [control (within therapeutic range)], P = 0.592). Conclusion MM guided timely therapy escalation for non‐responders, identification of non‐adherence, and reversal of shunting. Therefore, it is a useful clinical tool to optimize thiopurines without significantly increasing healthcare costs.

Patients with inflammatory bowel disease (IBD) have an increased risk of cancer secondary to chronic inflammation and long-term use of immunosuppressive therapy. With the aging IBD population, the prevalence of cancer in IBD patients is increasing. As a result, there is increasing concern about the impact of IBD therapy on cancer risk and survival, as well as the effects of cancer therapies on the disease course of IBD. Managing IBD in patients with current or previous cancer is challenging since clinical guidelines are based mainly on expert consensus. Evidence is rare and mainly available from registries or observational studies. In contrast, excluding patients with previous/or active cancer from clinical trials and short-term follow-up can lead to an underestimation of the cancer or cancer recurrence risk of approved medications. The present narrative review aims to summarize the current evidence and provide practical guidance on the management of IBD patients with cancer. [ABSTRACT FROM AUTHOR]

Immune-checkpoint inhibitors (ICI) are highly effective in reinvigorating T cells to attack cancer. Nevertheless, a large subset of patients fails to benefit from ICI, partly due to lack of the cancer neoepitopes necessary to trigger an immune response. In this study, we used the thiopurine 6-thioguanine (6TG) to induce random mutations and thus increase the level of neoepitopes presented by tumor cells. Thiopurines are prodrugs which are converted into thioguanine nucleotides that are incorporated into DNA (DNA-TG), where they can induce mutation through single nucleotide mismatching. In a pre-clinical mouse model of a mutation-low melanoma cell line, we demonstrated that 6TG induced clinical-grade DNA-TG integration resulting in an improved tumor control that was strongly T cell dependent. 6TG exposure increased the tumor mutational burden, without affecting tumor cell proliferation and cell death. Moreover, 6TG treatment re-shaped the tumor microenvironment by increasing T and NK immune cells, making the tumors more responsive to immune-checkpoint blockade. We further validated that 6TG exposure improved tumor control in additional mouse models of melanoma. These findings have paved the way for a phase I/II clinical trial that explores whether treatment with thiopurines can increase the proportion of otherwise treatment-resistant cancer patients who may benefit from ICI therapy (NCT05276284). [ABSTRACT FROM AUTHOR]

Background: Coronavirus disease 2019 (COVID‐19) vaccination is recommended for patients with inflammatory bowel disease (IBD); however, suppressed immune responses have been reported for fully vaccinated patients under immunosuppressive therapy, mainly from Western countries. We prospectively analyzed antibody titers of IBD patients in Asia induced by two‐dose and additional dose of messengerRNA COVID‐19 vaccine. Methods: After measuring high‐affinity antibody titers, factors associated with antibody titers were identified by multiple regression analyses using the following covariates: sex, age (≥60 or <60 years), disease type (Crohn's disease or ulcerative colitis), vaccine type (BNT162b2 or mRNA‐1273), time from second/third vaccination, molecular‐targeted agent (anti‐tumor necrosis factor [TNF] agents, ustekinumab, vedolizumab, tofacitinib, or no molecular‐targeted agents), thiopurine, steroid, and 5‐aminosalicylic acid. Results: Among 409 patients analyzed, mean titer was 1316.7 U/mL (SD, 1799.3); 403 (98.5%) were judged to be seropositive (≥0.8 U/mL), and 389 (95.1%) had neutralizing antibodies (≥15 U/mL). After the third vaccination, mean titer raised up to 21 123.8 U/mL (SD, 23 474.5); all 179 were seropositive, and 178 (99.4%) had neutralizing antibodies. In 248 patients with genetic data, there was no difference in mean titer after two/third doses between carriers and non‐carriers of HLA‐A24 associated with severe disease during COVID‐19 infection. A multiple regression analyses using covariates revealed that older age, vaccine type (BNT162b2), time from second/third dose, anti‐TNF agent, tofacitinib, and thiopurine were independently associated with lower antibody titers. Conclusions: Our findings further support the recommendation for COVID‐19 vaccination in patients under immunosuppressive therapy, especially additional third dose for patients receiving anti‐TNF agents and/or thiopurine or tofacitinib. [ABSTRACT FROM AUTHOR]

Background: The short‐term efficacy of tacrolimus (Tac) for steroid‐dependent and steroid‐resistant refractory ulcerative colitis (UC) has been demonstrated; however, its long‐term outcomes have not been well documented. Thus, this study aimed to clarify the long‐term outcomes of patients who achieved Tac‐induced remission and identify its predictors. Methods: This study included patients with moderate‐to‐severe active UC who started receiving Tac at our hospital between July 2004 and December 2016. Short‐term treatment response was assessed using the Lichtiger index 3 months after starting Tac, and responding patients were further followed up to assess long‐term outcomes. The primary endpoint was the relapse‐free survival after Tac‐induced remission, and the secondary endpoint was the identification of factors associated with relapse after Tac‐induced remission. Results: The cumulative relapse‐free survival rate at 10 years after Tac‐induced remission was 33.2%. Multivariate analysis revealed that being thiopurine naïve at Tac induction was associated with the absence of relapse (hazard ratio: 0.45; 95% confidence interval: 0.22–0.92). Conclusions: Approximately one‐third of patients who achieved Tac‐induced remission maintained long‐term remission. Being thiopurine naïve at Tac induction was a predictor of the absence of relapse. [ABSTRACT FROM AUTHOR]

Thiopurine monotherapy has an indication for IBD patients notably in case of steroid dependency. With infliximab (IFX) infusion, combotherapy must be preferred. For adalimumab, this point must be discussed depending of the case. We have no data to suggest combotherapy with ustekinumab but conversely, this combotherapy has to be discussed in some cases of Crohn's disease. With sub cutaneous IFX, combotherapy should not be necessary. These conclusions must be confirmed in the future. Finally, in case of immunogenic failure, switch of anti TNF on combotherapy must be suggested. [ABSTRACT FROM AUTHOR]

The inflammatory bowel diseases (IBD) are complex immune-mediated inflammatory diseases that are associated with significant morbidity around the world. As our understanding of IBD, and other immune-mediated inflammatory diseases, advances the number of therapeutic targets has increased which has rapidly driven the development and introduction of new therapies. While these new therapies have shown promise they come with the significant drawback of high costs. For many IBD patients around the world the cost of newer therapies is prohibitive which means treating clinicians often need to turn to optimising simpler, older, and inexpensive medications. The concept of optimising well established cheaper medications is not unique to the management of IBD as health systems all over the world look to reduce costs while simultaneously improving patient outcomes. Despite thiopurines being used in the management IBD for over 60 years, many clinicians are still hesitant to use them due to perceptions around limited efficacy and poor tolerance. One method identified to potentially increase utilisation of thiopurines involves the coadministration of allopurinol. In this review we will explore the history, pharmacology, recent studies and give recommendations for the utilisation of the usual duo of azathioprine combined with allopurinol. [ABSTRACT FROM AUTHOR]

Background: Thiopurine‐related adverse events such as leukopenia, liver dysfunction and pancreatitis are associated with variants in the NUDT15 gene. Loss‐of‐function (low or no enzyme activity) alleles are more common in Asian and Hispanic populations. The prevalence of these variants in the Australian inflammatory bowel disease (IBD) population has not yet been reported. Aim: To evaluate the presence of NUDT15 loss‐of‐function alleles *2,*3,*9 in the Australian IBD population. Methods: The NUDT15 screening cohort included 423 IBD patients from Brisbane, Australia. Study patients were recruited by: (i) retrospective review of clinical charts for thiopurine‐related severe adverse events; (ii) pathology data (white blood cell (WBC) and neutrophil counts). NUDT15 genotyping was performed using polymerase chain reaction (PCR)‐high‐resolution melt (HRM), TaqMan genotyping and Sanger sequencing. Results: NUDT15 mutation R139C (allele *3) was identified in 8 of 423 (1.9%) IBD patients. Seven of eight patients were R139C heterozygous (C/T) and one patient was R139C homozygous (T/T). One of the C/T group and the T/T patient developed thiopurine‐induced myelosuppression (TIM) within 60 days of dosing. One patient in the C/T group developed TIM after 60 days of thiopurine dosing. The remaining five patients in the C/T group did not show TIM; however, other thiopurine‐related events could not be ruled out and therefore careful monitoring over a long period is recommended. Conclusions: This is the first study to report the frequency of NUDT15 haplotypes *2,*3,*9 in an Australian IBD population. The most common variant detected was the R139C mutation. PCR and Sanger sequencing are efficient and cost‐effective approaches for NUDT15 genotyping. [ABSTRACT FROM AUTHOR]

We have developed an efficient method for the synthesis of 6-thiopurine and thioguanine conjugates containing a (S)-glutamic acid residue, which is based on the reaction of 6-thio derivatives of purine with di-tert-butyl N-chloroacetyl-(S)-glutamate and subsequent hydrolysis of the ester groups. [ABSTRACT FROM AUTHOR]

Abstract Background Eosinophilic enteritis is a chronic inflammatory disorder of the intestinal tract that is characterized by eosinophil infiltration. Cytomegalovirus (CMV), a common virus, has a broad infectivity range. CMV is retained in the host body after infection. Impairment of host immune defences may reactivate the latent CMV, leading to symptoms of overt disease. Case presentation A Japanese female in her 70 s was admitted to a hospital due to diarrhoea and then transferred to our hospital. Laboratory data showed hypoalbuminemia. Computed tomography (CT) revealed oedema of the small intestine. Lower gastrointestinal endoscopy revealed oedema of the submucosa, without any remarkable changes in the mucosa of the terminal ileum. Histological examination of the terminal ileum revealed infiltration of > 20 eosinophils per high-power field (HPF). These findings aided in diagnosing eosinophilic enteritis. We administered methylprednisolone (500 mg/day) for three days, followed by tapering prednisolone. However, the patient’s general condition and hypoalbuminemia failed to improve. Immunoglobulin (Ig) G- CMV and IgM-CMV tests were positive. CMV antigenemia was extremely high. Therefore, we administered ganciclovir intravenously, which improved the patient’s condition. Furthermore, azathioprine was administered to taper and discontinue prednisolone without relapse of eosinophilic enteritis. This treatment helped stabilize the patient’s condition for approximately four years. Conclusion We present a case of eosinophilic enteritis accompanied by CMV disease during prednisolone treatment. The patient’s condition improved after administration of ganciclovir. Azathioprine aided in discontinuing prednisolone and stabilizing the patient’s condition for approximately four years.

Abstract Objective The nucleoside diphosphate linked moiety X (Nudix)-Type motif 15 (NUDT15) enzyme is involved in thiopurine metabolism. Genetic variants in the NUDT15 gene result in decreased NUDT15 activity, which in addition to decreased thiopurine S-methyltransferase (TPMT) activity, contributes to thiopurine toxicity. Current standard approaches of NUDT15 genetic analysis have mainly been targeting several common variants. We aimed to develop a clinical-grade DNA-based assay for genetic analysis of the NUDT15 gene using Sanger di-deoxy sequencing. Results Sanger sequencing results were fully concordant with the expected NUDT15 genotype in all 17 cell line samples with known NUDT15 variants (accuracy = 100%; 95% CI 80.49 to 100.00%). Precision studies showed 100% intra-run repeatability and 100% inter-run reproducibility, respectively. Genetic analysis of the NUDT15 gene was performed for 80 patients of Asian ethnicity with wildtype TPMT. 76% (N = 61) of the studied individuals had NUDT15 *1/*1 diplotype. 25% (N = 14) of Chinese and 36% (N = 5) of Malays were found to carry at least 1 non-functional NUDT15 allele. Our study confirmed a high frequency of NUDT15 c.415C>T and c.55_56insGAGTCG variants in the Chinese and Malay ethnic groups in Singapore, highlighting the importance of determining NUDT15 genotype prior to thiopurine dosing.

Background/Aims Thiopurines are key drugs for inflammatory bowel disease (IBD), including ulcerative colitis (UC) and Crohn’s disease (CD). Recently, NUDT15 polymorphism (R139C, c.415C > T) has been shown to be associated with thiopurine-induced adverse events in Asian populations. In patients with the C/T genotype, low-dose thiopurine treatment is recommended, but its long-term efficacy and tolerability remain unclear. This study aimed to uncover the long-term efficacy and appropriate dosage of thiopurine for IBD patients with the C/T genotype. Methods A total of 210 patients with IBD (103 UC and 107 CD) determined to have NUDT15 R139C variants were enrolled. Clinical data were retrospectively reviewed from medical records. Results Of 46 patients (21.9%) with the C/T genotype, 30 patients (65.2%) were treated with thiopurines. Three of whom (10.0%) discontinued thiopurine treatment due to adverse events and 27 of whom continued. The median maintenance dosage of 6-mercaptopurine was 0.25 mg/kg/day (range, 0.19–0.36 mg/kg/day), and 6-thioguanine nucleotides level was 230 (104–298) pmol/8 × 108 red blood cells. Cumulative thiopurine continuation rates for 120 months for patients with the C/C and C/T genotypes were not significantly different (P = 0.895). Cumulative non-relapse rates in the patients with UC treated with thiopurine monotherapy and surgery-free rates in CD patients treated with combination therapy (thiopurines and anti-tumor necrosis factor-α agents) for maintenance remission were not significantly different at 60 months (C/C vs. C/T, P = 0.339 and P = 0.422, respectively). Conclusions Low-dose thiopurine treatment is an effective and acceptable treatment for patients with C/T genotype.

Background and Aim: Thiopurines are recommended for maintenance of steroid‐free remission (SFR) in inflammatory bowel disease (IBD). Thiopurine metabolite monitoring (MM) is increasingly used in the West but remains novel in Singapore, with limited information on its therapeutic and economic benefits. Hence, this study aims to investigate MM's clinical utility and its impact on healthcare resource utilization in Singaporean IBD patients. Methods: A retrospective observational study was conducted at Singapore General Hospital outpatient IBD Centre. Patients with IBD, baseline MM during 2014–2017, and weight‐based thiopurine doses for ≥4 weeks were followed up for 1 year. Actions were taken to optimize therapy, and metabolite levels before and after the first action were documented. Outcomes assessed included SFR, no therapy escalation or surgery, healthcare resource utilization, and direct healthcare costs. Results: Ninety IBD patients (50 Crohn's disease, 40 ulcerative colitis) were included. Among them, 40% had baseline metabolite levels within therapeutic range, 31.1% sub‐therapeutic, 21.1% supra‐therapeutic, and 7.8% shunters. Repeated MM with subsequent dose optimization helped 67.2% of patients achieve therapeutic levels after 1 year. Overall, 87.8% of patients achieved SFR and 90% had no therapy escalation or surgery. Despite greater outpatient visits and laboratory investigations with MM, the median total healthcare costs at 1 year only increased marginally (S$6407.66 [shunters] vs S$5215.20 [supra‐therapeutic] vs S$4970.80 [sub‐therapeutic] vs S$4370.48 [control (within therapeutic range)], P = 0.592). Conclusion: MM guided timely therapy escalation for non‐responders, identification of non‐adherence, and reversal of shunting. Therefore, it is a useful clinical tool to optimize thiopurines without significantly increasing healthcare costs. [ABSTRACT FROM AUTHOR]

Conflicting data about inflammatory bowel disease [IBD] and immunosuppressants are risk factors for severe COVID-19 confuse patients and healthcare providers. Clinical reports with longer follow-up are lacking. A retrospective search was performed for severe COVID-19 (hospital admission and/or mortality) one year after the SARS-CoV-2 outbreak in an IBD cohort from one of the most affected Dutch regions. Cohort characteristics were explored by value-based healthcare data, including immunotherapy. COVID-19 cases were detected by ICD-10 codes and further examined for IBD determinants (including medication) and COVID-19 characteristics (intensive care admission, respiratory support, treatment, mortality). The national mortality register was consulted, ensuring detection of patients that died without admission. Results were compared with regional and national general population registries. The IBD cohort consisted of 1453 patients (51% Crohn's disease, 54% women, 39.9% using immunotherapy), including children. Biologics use increased during the study. Eight cases (0.55%) had severe COVID-19: seven were hospitalized (0.48%, 95% confidence interval [CI] 0.21–1.04), and two died (0.14%, CI 0.002–0.55). Six patients had comorbidity, one used immunotherapy, and four had no medication. Both deceased patients were older than 80 years, had severe comorbidity, but used no immunotherapy. Hospitalization occurred significantly more in the IBD cohort than regionally (0.18%, CI 0.17–0.19, p = 0.015), but not significantly more than nationally (0.28%, CI 0.279–0.284). Mortality was equal in IBD patients, regionally (0.11%, CI 0.10–0.12) and nationally (0.13%, CI 0.125–0.128). Neither IBD nor immunosuppressants are associated with increased risks of severe COVID-19 in an observational study with one-year follow-up. [ABSTRACT FROM AUTHOR]

Thiopurine prodrugs (azathioprine, AZA, and 6-mercaptopurine, 6MP) are embryotoxic to rodents and rabbits. Little is known about the developmental toxicity of 6-methylmercaptopurine riboside (6MMPr), a thiopurine drug metabolite that is thought to mediate its liver toxicity. A limb bud assay found that 6MMPr impairs the in vitro morphogenetic differentiation of mouse limb extremities, being more potent than 6MP in the assay. This study evaluated the embryotoxicity of 6MMPr (0, 7.5, 15, 30 mg/kg bw sc) in rats after single-dose exposure in mid organogenesis (GD10). One group of pregnant rats was similarly treated with 6MP (15 mg/kg bw sc). After C-section (GD21), fetuses were weighed, and examined for external abnormalities. One third of each litter was examined for soft-tissue abnormalities while the remaining fetuses were cleared and stained for skeleton evaluation. 6MMPr caused a dose-dependent maternal weight loss followed by recovery before term pregnancy. Except for a nonsignificant increase in embryolethality and slight reduction in fetal weight at 30 mg/kg bw, no indication of embryotoxicity was noted at this dose or at lower doses of 6MMPr. In contrast, 6MP led to nearly 98 % of post-implantation losses in the presence of slight-to-mild maternal toxicity. These results are consistent with the notion that maternal treatment with 6MMPr affects embryo development, causing a nonsignificant increase in embryolethality and a slight reduction in fetal weight at 30 mg/kg bw. However, there was no increase in abnormalities at this dose, which was severely toxic to the dams, as reflected in the maternal weight gain data. • Repeated dosing with 6MMPr (≥7.5 mg/kg bw/d) was lethal to non-pregnant female rats. • Single doses of 6MMPr ≥ 7.5 mg/kg bw were maternally toxic. • Even at maternally toxic doses, 6MMPr caused no increase in fetal abnormalities in rats. • 6MMPr given in mid-organogenesis (GD10) was not teratogenic. • In contrast to 6MMPr, 6MP was a developmental toxicant in rats. [ABSTRACT FROM AUTHOR]

Variants in thiopurine methyltransferase (TPMT) and nudix hydrolase 15 (NUDT15) are associated with an accumulation of cytotoxic metabolites leading to increased risk of drug-related toxicity with standard doses of thiopurine drugs. We established TPMT and NUDT15 genetic testing for clinical use and evaluated the utilization, service outcomes and potential value of multi-gene PGx testing for 210 patients that underwent pharmacogenetics (PGx) testing for thiopurine therapy with the aim to optimize service delivery for future prescribing. The test was most commonly ordered for Gastroenterology (40.0%) and Neurology (31.4%), with an average turnaround time of 2 days. Following testing, 24.3% patients were identified as intermediate or poor metabolizers, resulting in 51 recommendations for a drug or dose change in thiopurine therapy, which were implemented in 28 (54.9%) patients. In the remaining patients, 14 were not adjusted and 9 had no data available. Focusing on drug gene interactions available for testing in our laboratory, multi-gene PGx results would present opportunities for treatment optimization for at least 33.8% of these patients who were on 2 or more concurrent medications with actionable PGx guidance. However, the use of PGx panel testing in clinical practice will require the development of guidelines and education as revealed by a survey with the test providers. The evaluation demonstrated successful implementation of single gene PGx testing and this experience guides the transition to a pre-emptive multi-gene testing approach that provides the opportunity to improve clinical care.

L'intervalle thérapeutique étroit des médicaments utilisés en oncologie nécessite un recours fréquent aux analyses biologiques afin de personnaliser le choix de la molécule et d'adapter la posologie. La pharmacogénétique peut permettre l'optimisation du traitement anticancéreux, afin de limiter les effets indésirables sévères tout en préservant une efficacité optimale. La réalisation de tests de pharmacogénétique est recommandée en amont de la prescription des fluoropyrimidines et des thiopurines, qui sont disponibles en officine. The narrow therapeutic range of drugs used in oncology requires frequent recourse to biological analyses in order to personalize the choice of the molecule and to adapt the dosage. Pharmacogenetics can help optimize cancer therapy in order to limit severe side effects while maintaining optimal efficacy. Pharmacogenetic testing is recommended before prescribing fluoropyrimidines and thiopurines, which are available in pharmacies. [ABSTRACT FROM AUTHOR]

Background: Eosinophilic enteritis is a chronic inflammatory disorder of the intestinal tract that is characterized by eosinophil infiltration. Cytomegalovirus (CMV), a common virus, has a broad infectivity range. CMV is retained in the host body after infection. Impairment of host immune defences may reactivate the latent CMV, leading to symptoms of overt disease.Case Presentation: A Japanese female in her 70 s was admitted to a hospital due to diarrhoea and then transferred to our hospital. Laboratory data showed hypoalbuminemia. Computed tomography (CT) revealed oedema of the small intestine. Lower gastrointestinal endoscopy revealed oedema of the submucosa, without any remarkable changes in the mucosa of the terminal ileum. Histological examination of the terminal ileum revealed infiltration of > 20 eosinophils per high-power field (HPF). These findings aided in diagnosing eosinophilic enteritis. We administered methylprednisolone (500 mg/day) for three days, followed by tapering prednisolone. However, the patient's general condition and hypoalbuminemia failed to improve. Immunoglobulin (Ig) G- CMV and IgM-CMV tests were positive. CMV antigenemia was extremely high. Therefore, we administered ganciclovir intravenously, which improved the patient's condition. Furthermore, azathioprine was administered to taper and discontinue prednisolone without relapse of eosinophilic enteritis. This treatment helped stabilize the patient's condition for approximately four years.Conclusion: We present a case of eosinophilic enteritis accompanied by CMV disease during prednisolone treatment. The patient's condition improved after administration of ganciclovir. Azathioprine aided in discontinuing prednisolone and stabilizing the patient's condition for approximately four years. [ABSTRACT FROM AUTHOR]

Objective: The nucleoside diphosphate linked moiety X (Nudix)-Type motif 15 (NUDT15) enzyme is involved in thiopurine metabolism. Genetic variants in the NUDT15 gene result in decreased NUDT15 activity, which in addition to decreased thiopurine S-methyltransferase (TPMT) activity, contributes to thiopurine toxicity. Current standard approaches of NUDT15 genetic analysis have mainly been targeting several common variants. We aimed to develop a clinical-grade DNA-based assay for genetic analysis of the NUDT15 gene using Sanger di-deoxy sequencing. Results: Sanger sequencing results were fully concordant with the expected NUDT15 genotype in all 17 cell line samples with known NUDT15 variants (accuracy = 100%; 95% CI 80.49 to 100.00%). Precision studies showed 100% intra-run repeatability and 100% inter-run reproducibility, respectively. Genetic analysis of the NUDT15 gene was performed for 80 patients of Asian ethnicity with wildtype TPMT. 76% (N = 61) of the studied individuals had NUDT15 *1/*1 diplotype. 25% (N = 14) of Chinese and 36% (N = 5) of Malays were found to carry at least 1 non-functional NUDT15 allele. Our study confirmed a high frequency of NUDT15 c.415C>T and c.55_56insGAGTCG variants in the Chinese and Malay ethnic groups in Singapore, highlighting the importance of determining NUDT15 genotype prior to thiopurine dosing. [ABSTRACT FROM AUTHOR]

There is an increasing trend of malignancy worldwide. Disease-modifying antirheumatic drugs (DMARDs) are the cornerstones for the treatment of immune-mediated inflammatory diseases (IMIDs), but risk of malignancy is a major concern for patients receiving DMARDs. In addition, many IMIDs already carry higher background risks of neoplasms. Recently, the black box warning of malignancies has been added for Janus kinase inhibitors. Also, the use of biologic DMARDs in patients with established malignancies is usually discouraged owing to exclusion of such patients in pivotal studies and, hence, lack of evidence. In contrast, some conventional synthetic DMARDs (csDMARDs) have been reported to show antineoplastic properties and can be beneficial for patients with cancer. Among the csDMARDs, chloroquine and hydroxychloroquine have been the most extensively studied, and methotrexate is an established chemotherapeutic agent. Even cyclosporine A, a well-known drug associated with cancer risk, can potentiate the effect of some chemotherapeutic agents. We review the possible mechanisms behind and clinical evidence of the antineoplastic activities of csDMARDs, including chloroquine and hydroxychloroquine, cyclosporine, leflunomide, mycophenolate mofetil, mycophenolic acid, methotrexate, sulfasalazine, and thiopurines. This knowledge may guide physicians in the choice of csDMARDs for patients with concurrent IMIDs and malignancies. [ABSTRACT FROM AUTHOR]

Background: Immunomodulator therapy (e.g., thiopurines) has been linked to an increased malignancy risk, in patients with inflammatory bowel diseases (IBDs), which increases with treatment duration, based on studies mainly in Caucasian patients. However, our previous real-world study, of Japanese patients with IBDs, indicated no overall increased risk of non-Hodgkin lymphoma (NHL) with thiopurine treatment. Objectives: This subanalysis investigated the influence of thiopurine IBD treatment dose and duration, on incidence of NHL in Japanese patients. Method: The Medical Data Vision (MDV) claims database (17.8 million patients; April 2008–January 2018) was used to analyze incidence rate ratios (IRRs) of NHL, in eligible patients (≥1 diagnosis of ulcerative colitis or Crohn's disease) and no malignancy at diagnosis or first prescription of a thiopurine. Age- and sex-adjusted IRRs and 95% confidence interval for NHL were calculated as the incident cases compared in the subgroups versus the overall IBD population. Results: Among 75,673 patients with IBDs, 103 cases of NHL were recorded. There was no overall increase in the risk of developing NHL among Japanese patients treated with thiopurines. The IRRs relative to the overall IBD population were 1.88, 1.42, and 0.38 for <1 year, 1–3 years, and ≥3 years of thiopurine treatment. There were no differences in NHL incidence when grouping patients by mean daily thiopurine dose prescribed, age, or disease subgroups. Conclusion: Dose or duration of thiopurine treatment did not explain a lack of increased risk of NHL with thiopurine use in Japanese patients with IBDs. [ABSTRACT FROM AUTHOR]

The detection of cytomegalovirus (CMV) in the setting of inflammatory bowel disease often creates confusion whether CMV is a 'bystander' or 'disease.' This review discusses the clinical conundrum of CMV in ulcerative colitis, approach to discriminate infection from disease, and therapeutic considerations (immunosuppressive and anti-CMV treatment). CMV disease should be considered in corticosteroid refractory- dependent and thiopurine refractory disease. Endoscopy may reveal deep punched out ulcers, irregular ulcers, or cobble-stoning. The diagnosis rests on the presence and abundance of viral inclusion bodies on hematoxylin and eosin stain, positive immunohistochemistry, and/or positive tissue polymerase chain reaction. CMV disease is associated with worse outcomes including increased colectomy rates. The timing and duration of antiviral drugs in CMV disease is debatable but depends on the load of CMV in tissue. In high-grade infection, CMV needs to be treated while increasing immunosuppression may work in the setting of low-grade infection. Ganciclovir is the drug of choice for treatment of CMV disease. Tumor necrosis factor inhibitors may be useful for treating underlying disease activity in the setting of CMV. Other emerging therapies include fecal microbiota transplantation. Randomized studies are necessary to define the best timing and duration of anti-CMV therapy. [ABSTRACT FROM AUTHOR]