thioguanine-anhydrous and Inflammatory-Bowel-Diseases

Thiopurines are an important therapy for the maintenance of remission in inflammatory bowel disease (IBD). However, the use of thioguanine has been limited by concerns regarding its toxicity. We performed a systematic review to evaluate its effectiveness and safety in IBD.. Electronic databases were searched to identify studies reporting clinical responses and/or adverse events of thioguanine therapy in IBD. We calculated the pooled clinical response and clinical remission rates of thioguanine in IBD. Subgroup analyses were done for the dosage of thioguanine and the type of studies (prospective or retrospective). Meta-Regression was used to analyze the impact of dose on clinical efficacy and occurrence of nodular regenerative hyperplasia.. A total of 32 studies were included. The pooled clinical response rate of thioguanine therapy in IBD was 0.66 (95% C.I. 0.62 - 0.70; I. TG is an efficacious and well-tolerated drug in most patients with IBD. Nodular regenerative hyperplasia, cytopenias, and liver function abnormalities occur in a small subset. Future studies should look into TG as primary therapy in IBD.

Topics: Humans; Hyperplasia; Inflammatory Bowel Diseases; Prospective Studies; Retrospective Studies; Thioguanine

Drug rediscovery refers to the principle of using 'old' drugs outside the indications mentioned in the summary of product characteristics. In the past decades, several drugs were rediscovered in a wide variety of medical fields. One of the most recent examples is the unconditional registration of thioguanine (TG), a thiopurine derivative, in patients with inflammatory bowel disease in the Netherlands. In this paper, we aim to visualise potential hurdles that hamper drug rediscovery in general, emphasise the global need for optimal use and development of potentially useful drugs, and provide an overview of the registration process for TG in the Netherlands. With this summary, we aim to guide drug rediscovery trajectories in the near future.

Topics: Azathioprine; Gastroenterology; Humans; Immunosuppressive Agents; Inflammatory Bowel Diseases; Mercaptopurine; Netherlands; Off-Label Use; Thioguanine

Thiopurines in combination with glucocorticoids are used as first-line, second-line and maintenance therapies in autoimmune hepatitis and opportunities exist to improve and expand their use.. To describe the metabolic pathways and key factors implicated in the efficacy and toxicity of the thiopurine drugs and to indicate the opportunities to improve outcomes by monitoring and manipulating metabolic pathways, individualising dosage and strengthening the response.. English abstracts were identified in PubMed by multiple search terms. Full-length articles were selected for review, and secondary and tertiary bibliographies were developed.. Thiopurine methyltransferase activity and 6-tioguanine (6-thioguanine) nucleotide levels influence drug efficacy and safety, and they can be manipulated to improve treatment response and prevent myelosuppression. Methylated thiopurine metabolites are associated with hepatotoxicity, drug intolerance and nonresponse and their production can be reduced or bypassed. Universal pre-treatment assessment of thiopurine methyltransferase activity and individualisation of dosage to manipulate metabolite thresholds could improve outcomes. Early detection of thiopurine resistance by metabolite testing, accurate estimations of drug onset and strength by surrogate markers and adjunctive use of allopurinol could improve the management of refractory disease. Dose-restricted tioguanine (thioguanine) could expand treatment options by reducing methylated metabolites, increasing the bioavailability of 6-tioguanine nucleotides and ameliorating thiopurine intolerance or resistance.. The efficacy and safety of thiopurines in autoimmune hepatitis can be improved by investigational efforts that establish monitoring strategies that allow individualisation of dosage and prediction of outcome, increase bioavailability of the active metabolites and demonstrate superiority to alternative agents.

Topics: Allopurinol; Azathioprine; Drug-Related Side Effects and Adverse Reactions; Guanine Nucleotides; Hepatitis, Autoimmune; Humans; Inflammatory Bowel Diseases; Mercaptopurine; Purines; Quality Improvement; Thioguanine; Thionucleotides; Treatment Outcome

Thiopurine-derivates azathioprine and mercaptopurine are frequently used to maintain remission in inflammatory bowel diseases (IBD). Despite their efficacy, more than 50% of patients discontinue therapy, mainly due to the development of adverse events. Thioguanine is an alternative thiopurine and has been conditionally licensed in The Netherlands as IBD treatment for patients after conventional thiopurine therapy failure. In this review we will provide practical information on initiating and maintaining thioguanine therapy in IBD and provide information concerning safety issues and future perspectives. The thioguanine toxicity profile is relatively mild and the reported incidence of nodular regenerative hyperplasia related to thioguanine use seems comparable to conventional thiopurines and the background incidence in IBD patients. Routine monitoring of laboratory parameters and adverse events is recommended, comparable to the monitoring of patients on conventional thiopurine therapy.

Topics: Humans; Immunosuppressive Agents; Inflammatory Bowel Diseases; Thioguanine

Thiopurine drugs continue to be a cornerstone of inflammatory bowel disease (IBD) treatment. Thiopurines are economical compared with many newer medical treatments for IBD, other chronic inflammatory diseases and leukaemia, although they are not without their shortcomings. These include a slow-onset therapeutic action and many adverse drug reactions. This feature article surveys published data, unpublished in vitro and in vivo experiments, as well as clinical experience, underpinning a rationale for bringing a novel thiopurine drug formulation to market. This formulation has a rapid action making it suitable for the induction and maintenance treatment of IBD and avoids most thiopurine-associated adverse reactions.

Topics: Administration, Rectal; Animals; Chemical and Drug Induced Liver Injury; Humans; Immunosuppressive Agents; Inflammatory Bowel Diseases; Intestinal Mucosa; Thioguanine

The recently established association between higher levels of DNA-incorporated thioguanine nucleotides and lower relapse risk in childhood acute lymphoblastic leukaemia (ALL) calls for reassessment of prolonged 6-thioguanine (6TG) treatment, while avoiding the risk of hepatotoxicity.. To assess the incidence of hepatotoxicity in patients treated with 6TG, and to explore if a safe dose of continuous 6TG can be established.. Databases, conference proceedings, and reference lists of included studies were systematically searched for 6TG and synonyms from 1998-2018.. We included studies of patients with ALL or inflammatory bowel disorder (IBD) treated with 6TG, excluding studies with 6TG as part of an intensive chemotherapy regimen. We uploaded a protocol to PROSPERO (registration number CRD42018089424). Database and manual searches yielded 1823 unique records. Of these, 395 full-texts were screened for eligibility. Finally, 134 reports representing 42 studies were included.. We included data from 42 studies of ALL and IBD patients; four randomised controlled trials (RCTs) including 3,993 patients, 20 observational studies including 796 patients, and 18 case reports including 60 patients. Hepatotoxicity in the form of sinusoidal obstruction syndrome (SOS) occurred in 9-25% of the ALL patients in two of the four included RCTs using 6TG doses of 40-60 mg/m2/day, and long-term hepatotoxicity in the form of nodular regenerative hyperplasia (NRH) was reported in 2.5%. In IBD patients treated with 6TG doses of approximately 23 mg/m2/day, NRH occurred in 14% of patients. At a 6TG dose of approximately 12 mg/m2/day, NRH was reported in 6% of IBD patients, which is similar to the background incidence. According to this review, doses at or below 12 mg/m2/day are rarely associated with notable hepatotoxicity and can probably be considered safe.

Topics: Antimetabolites, Antineoplastic; Chemical and Drug Induced Liver Injury; Humans; Inflammatory Bowel Diseases; Liver; Precursor Cell Lymphoblastic Leukemia-Lymphoma; Publication Bias; Thioguanine

Thiopurines, available as azathioprine, mercaptopurine, and thioguanine, are immunomodulating agents primarily used to maintain corticosteroid-free remission in patients with inflammatory bowel disease. To provide a state-of-the-art overview of thiopurine treatment in inflammatory bowel disease, this clinical review critically summarises the available literature, as assessed by several experts in the field of thiopurine treatment and research in inflammatory bowel disease.

Topics: Azathioprine; Drug Therapy, Combination; Gastrointestinal Agents; Humans; Immunosuppressive Agents; Inflammatory Bowel Diseases; Infliximab; Mercaptopurine; Neoplasms; Risk Factors; Thioguanine

The potential therapeutic effect of thioguanine in the management of inflammatory bowel disease (IBD) is hindered due to association with vascular hepatotoxicity. The study aimed to assess the evidence for efficacy of thioguanine in IBD management and the association with nodular regenerative hyperplasia (NRH) and other thioguanine-related hepatotoxicities.. Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were used for literature search. Due to the lack of randomized controlled trials (RCTs), the search was extended to observational studies. Quality of the included studies were graded A to C based on evaluation tools used to determine efficacy (subjective and objective grading tools) and nodular regenerative hyperplasia safety (liver biopsy and imaging tools).. Two hundred and ninety studies were identified, but following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines only 13 studies were evaluated for efficacy and safety of thioguanine. Outcome measures were consistent across the included studies. Thioguanine appeared efficacious and well-tolerated in patients who were intolerant/non-responsive to existing immunomodulators. There was a trend toward a positive association between dose of thioguanine and NRH but not with other adverse events such as liver biochemical abnormalities or with portal hypertension.. The evidence to support thioguanine treatment is limited to observational studies. While encouraging, there is a need for prospective RCTs to determine the role of thioguanine in the management of IBD.

Topics: Gastrointestinal Agents; Humans; Hyperplasia; Inflammatory Bowel Diseases; Liver; Observational Studies as Topic; Thioguanine

Thiopurines are widely used in the management of inflammatory bowel diseases. However, their minimum effective dose and dose-response relationship remain undefined, and evidence about their use in clinical practice is mostly heterogeneous. This systematic review and meta-analysis aimed: i] to assess the clinical value of 6-thioguanine nucleotide thresholds; and ii] to compare mean 6-thioguanine nucleotide concentrations between patients in clinical remission vs. those with active disease.. A systematic literature search was carried out using four databases. Statistical heterogeneity was assessed with the I2 statistic followed by subgroup and sensitivity analyses. Odds ratios were computed using the random-effects model.. A total of 1384 records were identified in the systematic search, of which 25 were retained for further analysis: 22 were used in the cut-off comparisons and 12 were used in the 6-thioguanine nucleotide mean differences analysis. The global odds ratio for remission in patients with 6-thioguanine nucleotide levels above the predefined thresholds was 3.95 (95% confidence interval [CI], 2.63-5.94; p < 0.001]. When considering the different thresholds individually, the odd ratios were significant for values above 235 pmol/8 × 108 and 250 pmol/8 × 108 red blood cells [2.25 and 4.71, respectively]. Mean 6-thioguanine nucleotide levels were higher among patients in clinical remission, with a pooled difference of 63.37 pmol/8 × 108 red blood cells [95% CI, 31.81-94.93; p < 0.001].. This study reinforces the link between 6-thioguanine nucleotide levels and clinical remission in inflammatory bowel diseases, also exploring the validity of specific 6-thioguanine nucleotide thresholds to predict clinical outcomes.

Topics: Dose-Response Relationship, Drug; Humans; Inflammatory Bowel Diseases; Remission Induction; Thioguanine

The use of thiopurines in the treatment of inflammatory bowel disease (IBD) can be optimized by the application of therapeutic drug monitoring. In this procedure, 6-thioguanine nucleotides (6-TGN) and 6-methylmercaptopurine (6-MMP) metabolites are monitored and related to therapeutic response and adverse events, respectively. Therapeutic drug monitoring of thiopurines, however, is hampered by several analytical limitations resulting in an impaired translation of metabolite levels to clinical outcome in IBD. Thiopurine metabolism is cell specific and requires nucleated cells and particular enzymes for 6-TGN formation. In the current therapeutic drug monitoring, metabolite levels are assessed in erythrocytes, whereas leukocytes are considered the main target cells of these drugs. Furthermore, currently used methods do not distinguish between active nucleotides and their unwanted residual products. Last, there is a lack of a standardized laboratorial procedure for metabolite assessment regarding the substantial instability of erythrocyte 6-TGN. To improve thiopurine therapy in patients with IBD, it is necessary to understand these limitations and recognize the general misconceptions in this procedure.

Topics: Antimetabolites; Azathioprine; Drug Monitoring; Humans; Inflammatory Bowel Diseases; Mercaptopurine; Thioguanine

Thiopurines are commonly used drugs in inflammatory bowel disease. Intracellular levels of thiopurine metabolites [i.e. 6-thioguaninenucleotides (6-TGN)] are associated with efficacy and toxicity. Because 6-TGN measurement is not globally available, the mean corpuscular volume (MCV) has been proposed as a surrogate marker for monitoring thiopurine therapy.. To analyze the relationship between MCV and efficacy of thiopurines, defined as either response to therapy or 6-TGN levels.. A systematic search on PubMed was performed.. Fifteen studies were included. In six studies, a positive association was found between ΔMCV and 6-TGN. In four studies, it was suggested that ΔMCV can be used to predict clinical remission. In five articles, no association was found.. In the majority of articles, it was reported that ΔMCV is useful in guiding intracellular metabolite levels. However, there is insufficient evidence showing that ΔMCV can predict clinical remission.

Topics: Anti-Inflammatory Agents; Biomarkers; Drug Monitoring; Erythrocyte Indices; Gastrointestinal Agents; Humans; Inflammatory Bowel Diseases; Predictive Value of Tests; Purines; Thioguanine; Treatment Outcome

To critically assess the available literature regarding the efficacy of thioguanine treatment in inflammatory bowel disease (IBD) patients, irrespective of the (hepato-) toxicity profile.. A systematic literature search of the MEDLINE database using PubMed was performed using the keywords "thioguanine", "6-TG", "thioguanine", "inflammatory bowel disease", "IBD", "Crohn's disease", "Ulcerative colitis" and "effectiveness" in order to identify relevant articles published in English starting from 2000. Reference lists of the included articles were cross-checked for missing articles. Reviewed manuscripts concerning the effectiveness of thioguanine treatment in IBD were reviewed by the authors and the data were extracted. Data were subsequently analyzed with descriptive statistics. Due to the lack of standardized outcomes, a formal meta-analysis was not performed.. A total of 11 applicable studies were found that involved the effectiveness of thioguanine therapy in IBD. Eight studies were conducted in a prospective manner, in the remaining three studies, data was collected retrospectively. In total, 353 IBD-patients (225 patients with Crohn's disease, 119 with ulcerative colitis and nine with unclassified IBD) with prior azathioprine/mercaptopurine resistance and/or intolerance (. The efficacy of thioguanine therapy in IBD patients intolerant to conventional thiopurine therapy is observed in 65%, with short term adverse events in 20% of patients.

Topics: Antimetabolites, Antineoplastic; Humans; Inflammatory Bowel Diseases; Thioguanine

Thiopurine analogs and anti-tumor necrosis factor (TNF) agents have dramatically changed the therapeutics of inflammatory bowel diseases (IBD), improving short and long-term outcomes. Unfortunately some patients do not respond to therapy and others lose response over time. The pharmacokinetic properties of these drugs are complex, with high inter-patient variability. Thiopurine analogs are metabolized through a series of pathways, which vary according to the patients' pharmacogenetic profile. This profile largely determines the ratios of metabolites, which are in turn associated with likelihoods of clinical efficacy and/or toxicity. Understanding these mechanisms allows for manipulation of drug dose, aiming to reduce the development of toxicity while improving the efficacy of treatment. The efficacy of anti-TNF drugs is influenced by many pharmacodynamic variables. Several factors may alter drug clearance, including the concomitant use of immunomodulators (thiopurine analogs and methotrexate), systemic inflammation, the presence of anti-drug antibodies, and body mass. The treatment of IBD has evolved with the understanding of the pharmacologic profiles of immunomodulating and TNF-inhibiting medications, with good evidence for improvement in patient outcomes observed when measuring metabolic pathway indices. The role of routine measurement of metabolite/drug levels and antibodies warrants further prospective studies as we enter the era of personalized IBD care.

Topics: Adalimumab; Antibodies; Antibodies, Monoclonal; Antibodies, Monoclonal, Humanized; Azathioprine; Drug Monitoring; Genotype; Humans; Immunologic Factors; Inflammation; Inflammatory Bowel Diseases; Infliximab; Methyltransferases; Phenotype; Purines; Thioguanine; Thionucleosides; Treatment Outcome; Tumor Necrosis Factor-alpha

Colitis-associated cancer represents a long-standing problem, with two new factors adding to its importance: the diffusion of inflammatory bowel disease in developing countries, and the increased availability of effective drugs that control ulcerative colitis delaying or abrogating the need for a curative colectomy. The consolidated evidence that inflammation is the unique variable that factors in colitic cancer development has conferred impetus to the search and release of anti-inflammatory/immune suppressive molecules to pursue the goal of cancer chemoprevention. Cutting-edge research has provided breakthrough insights into the mechanism of the chemopreventive actions of mesalamines, thiopurines, and probiotics, and we expand on these topics. Despite these advancements, bedside evidence is still mixed and calls for further scrutiny. Nowadays, the clinician must continue to rely on classic preventive measures such as surveillance colonoscopy, and the early and aggressive use of drugs that permit to keep the degree of mucosal inflammation to a minimum.

Topics: Animals; Anti-Inflammatory Agents; Cell Transformation, Neoplastic; Chemoprevention; Colonoscopy; Colorectal Neoplasms; Humans; Inflammatory Bowel Diseases; Mesalamine; Probiotics; Thioguanine

Thiopurines represent an effective and widely prescribed therapy in inflammatory bowel disease (IBD). Concerns about toxicity, mainly resulting from a wide inter-individual variability in thiopurine metabolism, restrict their use. Optimal thiopurine dosing is challenging for preventing adverse drug reactions and improving clinical response.. To review efficacy and toxicity of thiopurines in IBD. To provide pharmacogenetic-based therapeutic recommendations.. We conducted a query on PubMed database using 'inflammatory bowel disease', 'thiopurine', 'azathioprine', '6-mercaptopurine', 'TPMT', 'pharmacogenetics', 'TDM', and selected relevant articles, especially clinical studies.. Thiopurine metabolism - key enzyme: thiopurine S-methyltransferase (TPMT) - modulates clinical response, as it results in production of the pharmacologically active and toxic metabolites, the thioguanine nucleotides (6-TGN). Adjusting dosage according to TPMT status and/or metabolite blood levels is recommended for optimising thiopurine therapy (e.g. improving response rate up to 30% or decreasing haematological adverse events of 25%). Other enzymes or transporters of interest, as inosine triphosphatase (ITPase), glutathione S-transferase (GST), xanthine oxidase (XO), aldehyde oxidase (AOX), methylene tetrahydrofolate reductase (MTHFR) and ATP-binding cassette sub-family C member 4 (ABCC4) are reviewed and discussed for clinical relevance.. Based on the literature data, we provide a therapeutic algorithm for thiopurines therapy with starting dose recommendations depending on TPMT status and thereafter dose adjustments according to five metabolite profiles identified with therapeutic drug monitoring (TDM). This algorithm allows a dosage individualisation to optimise the management of patients under thiopurine. Furthermore, identification of new pharmacogenetic biomarkers is promising for ensuring maximal therapeutic response to thiopurines with a minimisation of the risk for adverse events.

Topics: Algorithms; Azathioprine; Dose-Response Relationship, Drug; Humans; Immunosuppressive Agents; Inflammatory Bowel Diseases; Methyltransferases; Pharmacogenetics; Practice Guidelines as Topic; Thioguanine

Conventional thiopurines are considered to be effective and safe in the treatment of inflammatory bowel disease (IBD) patients; unfortunately more than 50% of patients discontinue thiopurine therapy, mainly due to the development of intractable adverse events. In recent years, the use of 6-thioguanine has been proposed as an alternative thiopurine in IBD patients failing to tolerate or to respond to conventional thiopurine therapy. In this clinical review, we describe the rationale for 6-thioguanine therapy and discuss the reported hepatotoxicity of 6-thioguanine (especially nodular regenerative hyperplasia). We propose expert-based guidelines for balanced treatment.

Topics: Anti-Inflammatory Agents; Chemical and Drug Induced Liver Injury; Drug Monitoring; Evidence-Based Medicine; Gastrointestinal Agents; Humans; Inflammatory Bowel Diseases; Practice Guidelines as Topic; Risk Assessment; Thioguanine; Treatment Outcome

The mean prevalence of azathioprine (AZA) or 6-mercaptopurine (MP)-induced liver injury in patients with inflammatory bowel disease was approximately 3%, and the mean annual drug-induced liver disorder rate was only 1.4%. However, this low figure calculated from retrospective studies contrasts with a much higher incidence (>10%) reported by a prospective study. Thiopurine-induced hepatotoxicity can be grouped into three syndromes: hypersensitivity, idiosyncratic cholestatic reaction, and endothelial cell injury (with resultant raised portal pressures, veno-occlusive disease, or peliosis hepatis). A small percentage of patients present with a slight elevation of liver tests (LTs) that do not have clinical implications and LTs return to normal values during the follow-up, indicating that it is not always necessary to adjust the dose of the immunomodulator. However, when abnormalities in LTs are more marked, the dose of AZA/MP may be reduced 50%, with posterior clinical and analytical controls. With this strategy, LTs frequently normalize spontaneously, and the initial AZA/MP dose may be cautiously prescribed again. Thiopurines may induce an unusual severe cholestatic jaundice that may not regress but even progress despite thiopurine withdrawal. Therefore, these drugs should be completely withdrawn, and not only tapered, in those patients presenting clinically significant jaundice. Despite a lack of evidence that monitoring of LTs is necessary in patients receiving AZA/MP, routinely performed laboratory controls including LTs seem recommendable. However, the optimal monitoring schedule remains to be established. As long-term hepatotoxicity seems to be an unpredictable and potentially severe adverse drug reaction of 6-thioguanine, this drug should not be administered outside a clinical trial setting. (Am J Gastroenterol 2007;102:1518-527).

Topics: Antimetabolites, Antineoplastic; Azathioprine; Chemical and Drug Induced Liver Injury; Global Health; Humans; Inflammatory Bowel Diseases; Liver Diseases; Mercaptopurine; Practice Guidelines as Topic; Prevalence; Thioguanine

Recently, the suggestion to use 6-thioguanine (6-TG) as an alternative thiopurine in patients with inflammatory bowel disease (IBD) has been discarded due to reports about possible (hepato) toxicity. During meetings arranged in Vienna and Prague in 2004, European experts applying 6-TG further on in IBD patients presented data on safety and efficacy of 6-TG. After thorough evaluation of its risk-benefit ratio, the group consented that 6-TG may still be considered as a rescue drug in stringently defined indications in IBD, albeit restricted to a clinical research setting. As a potential indication for administering 6-TG, we delineated the requirement for maintenance therapy as well as intolerance and/or resistance to aminosalicylates, azathioprine, 6-mercaptopurine, methotrexate and infliximab. Furthermore, indications are preferred in which surgery is thought to be inappropriate. The standard 6-TG dosage should not exceed 25 mg daily. Routine laboratory controls are mandatory in short intervals. Liver biopsies should be performed after 6-12 months, three years and then three-yearly accompanied by gastroduodenoscopy, to monitor for potential hepatotoxicity, including nodular regenerative hyperplasia (NRH) and veno-occlusive disease (VOD). Treatment with 6-TG must be discontinued in case of overt or histologically proven hepatotoxicity.

Topics: Antimetabolites, Antineoplastic; Chemical and Drug Induced Liver Injury; Congresses as Topic; Europe; Humans; Inflammatory Bowel Diseases; Thioguanine

In the past 10-20 years, knowledge of both thiopurine pharmacology and -pharmacogenetics has been extended dramatically and used to develop new strategies to improve efficacy and reduce toxicity.. To review thiopurine efficacy, toxicity, pharmacology, pharmacogenetics, interactions in patients with inflammatory bowel disease. Special attention was paid to new strategies for optimization of pharmacotherapy.. To collect relevant scientific articles, a Pubmed search was performed from 1966 through January 2006 with the following key words (MeSH terms preferentially) in multiple combinations: 'azathioprine', '6-mercaptopurine', '6-MP', '6-thioguanine', '6-TG', 'thiopurine(s)', 'metabolites', 'level(s)', 'TDM', 'TMPT', 'ITPA', 'genotype(s)', 'phenotype(s)', 'inflammatory bowel disease', 'Crohn('s) disease', 'ulcerative colitis'.. Strategies for optimization of pharmacotherapy include therapeutic drug monitoring of thiopurine metabolites, geno- or phenotyping crucial enzymes in thiopurine metabolism like thiopurine S-methyltransferase and inosine triphosphate pyrophosphatase, and the use of thioguanine as such.. Thiopurine S-methyltransferase genotyping and therapeutic drug monitoring are useful instruments for individualizing thiopurine pharmacotherapy of inflammatory bowel disease. Inosine triphosphate pyrophosphatase genotyping may be helpful in case of unexplainable myelotoxicity. In case of azathioprine- or mercaptopurine-intolerance, thioguanine seems a promising alternative. However, more knowledge needs to be gathered about its potential hepatotoxicity.

Topics: Azathioprine; Drug Interactions; Gastrointestinal Agents; Genotype; Humans; Inflammatory Bowel Diseases; Mercaptopurine; Methyltransferases; Phenotype; Purines; Thioguanine; Treatment Outcome; Xanthine Oxidase

Topics: Azathioprine; Bone Marrow; Drug Interactions; Drug Monitoring; Humans; Immunosuppressive Agents; Inflammatory Bowel Diseases; Lymphoma, Non-Hodgkin; Mercaptopurine; Methyltransferases; Structure-Activity Relationship; Thioguanine

Thioguanine derivatives, azathioprine and 6-mercaptopurine, represent major drugs in the treatment of chronic active inflammatory bowel disease. They are effective in two-thirds of the patients and safe over the long term in patients who can tolerate them (80-90%). Recent progress in understanding the metabolism of these drugs and its implication in clinical practice have brought up new tools and strategies that are proposed to optimize treatment. In particular, the measurement and characterization of key enzymes and metabolites may have clinical impact. Thus, thiopurine methyl transferase genotyping and activity measurement, as well as erythrocytes, 6-thioguanine nucleotides and 6-methyl mercaptopurine levels, may help in some situations of intolerance or inefficacy with these drugs. Indications for starting and stopping treatment with thioguanine derivatives are also discussed.

Topics: Azathioprine; Chronic Disease; Humans; Immunosuppressive Agents; Inflammatory Bowel Diseases; Mercaptopurine; Thioguanine

Chronotherapy is the timing of medication according to biological rhythms of the host to optimize drug efficacy and minimize toxicity. Efficacy and myelosuppression of azathioprine/6-mercaptopurine (AZA/6-MP) are correlated with the metabolite 6-thioguanine, while the metabolite 6-methylmercaptopurine correlates with hepatotoxicity.. This was a single-center, 10-week prospective crossover trial involving 26 participants with inactive inflammatory bowel disease (IBD) on a stable dose and time of AZA or 6-MP therapy. Participants were switched to the opposite delivery time (morning or evening) for 10 weeks, and metabolite measurements were at both time points.. In the morning vs evening dosing, 6-thioguanine levels were 225.7 ± 155.1 vs 175.0 ± 106.9 ( P < 0.01), and 6-methylmercaptopurine levels were 825.1 ± 1,023.3 vs 2,395.3 ± 2,880.3 ( P < 0.01), with 69% (18 out of 26) of participants had better metabolite profiles in the morning. Participants with optimal dosing in the morning had an earlier chronotype by corrected midpoint of sleep.. In the first study on a potential role of chronotherapy in IBD, we found (i) morning dosing of AZA or 6-MP resulted in more optimal metabolite profiles and (ii) host chronotype could help identify one-third of patients who would benefit from evening dosing. Circadian regulation of metabolic enzymes of AZA/6-MP activity in the liver is the likely cause of these differences. This pilot study confirms the need to incorporate chronotherapy in future multicenter clinical trials on IBD disease.

Topics: Azathioprine; Chronotherapy; Cross-Over Studies; Humans; Inflammatory Bowel Diseases; Mercaptopurine; Pilot Projects; Prospective Studies; Thioguanine

6-Thioguanine (6-TG) may be indicated in case of intolerance of or resistance to conventional thiopurines in the treatment of inflammatory bowel diseases (IBD). The aim of our study was to evaluate the intrapatient variability in the 6-TG metabolizing enzymes: hypoxanthine-guanine phosphoribosyl transferase (HGPRT), thiopurine S-methyl transferase and xanthine oxidase. We performed a pharmacokinetic study of 6-TG after oral and intravenous administration in IBD patients in remission. The enzyme activities were determined at baseline and 1 week after the initiation of 6-TG in red blood cells, peripheral blood mononuclear cells (PBMC) or plasma. From the results we conclude that HGPRT activity in erythrocytes decreases following the initiation of 6-TG therapy, which may imply that HGPRT is a rate limiting enzyme in 6-TG metabolism. Moreover, little intrapatient variability in enzyme activities was observed except for HGPRT activity in PBMC. These data may have implications in regard of future therapeutic drug monitoring.

Topics: Adult; Antimetabolites, Antineoplastic; Female; Genotype; Humans; Hypoxanthine Phosphoribosyltransferase; Inflammatory Bowel Diseases; Male; Methyltransferases; Middle Aged; Thioguanine; Xanthine Oxidase

A therapeutic level of 6-thioguanine nucleotides (6-TGN) has been reported in inflammatory bowel disease (IBD) patients under azathioprine (AZA). We investigated the threshold value of 6-TGN that may be predictive of AZA refractoriness and its impact on safety profile.. Patients with normal thiopurine methyltransferase (TPMT) activity (7.5-14 U/mL erythrocytes), suffering from steroid-dependent or active IBD despite AZA use for at least 6 months, were prospectively included. Clinical efficacy, adverse events, and thiopurine metabolite levels were recorded at baseline, 1 month after each dose escalation, and thereafter every 3 months.. Fifty-five patients were included (43 with Crohn's disease, 12 with ulcerative colitis). After a mean follow-up of 12 months, 31 patients (56.3%) did not reach clinical remission despite a gradual increase in AZA dose and 6-TGN level of >400 pmol/8 x 10(8) erythrocytes, and were considered refractory to AZA (sensitivity 45%, specificity 100%). Adverse events occurred more frequently in these patients than in responders (42%vs 25%, respectively, P= 0.02). Among 55 patients, 15 cases of myelotoxicity associated with elevated levels of total methylated metabolites (14,500 pmol/8 x 10(8) erythrocytes vs 5,230 pmol/8 x 10(8) erythrocytes in patients without myelotoxicity, P= 0.03) were observed. Patients with total methylated metabolites of >11,100 pmol/8 x 10(8) erythrocytes had an increased risk of developing myelotoxicity (odds ratio [OR] 11.0, 95% confidence interval [CI] 1.1-250, P= 0.05).. A 6-TGN level of >400 pmol/8 x 10(8) erythrocytes in IBD patients with normal TPMT activity and steroid-dependent or active disease despite an optimal AZA regimen may predict refractoriness to this drug. Furthermore, high levels of methylated derivatives are associated with an increased risk of myelotoxicity.

Topics: Adult; Azathioprine; Drug Resistance; Erythrocytes; Female; Guanine Nucleotides; Humans; Immunosuppressive Agents; Inflammatory Bowel Diseases; Male; Methyltransferases; Middle Aged; Prospective Studies; Thioguanine; Thionucleotides; Treatment Outcome

The use of 6-thioguanine has been proposed as a rescue drug for inflammatory bowel disease patients. Initial data on short-term efficacy and toxicity of 6-thioguanine were promising; however, these have been challenged by reports concerning its potential hepatotoxic effect (nodular regenerative hyperplasia). We proposed that these histological liver abnormalities may well be dose- or level-dependent.. We performed a prospective multi-centre study on the hepatotoxic potential of long-term and (as compared with prior studies) low-dose 6-thioguanine use.. Inflammatory bowel disease patients using 6-thioguanine for at least 30 consecutive months and consenting to undergo a liver biopsy were enrolled.. Liver biopsy specimens were scored by two pathologists, unaware of clinical data. Laboratory parameters, determined prior to initiation of 6-thioguanine therapy and prior to biopsy, were reviewed.. Twenty-eight biopsies were analysed. The majority of patients (89%) were azathioprine and/or 6-mercaptopurine intolerant inflammatory bowel disease patients. In 26 patients (93%) no signs of nodular regenerative hyperplasia were detected; in two additional patients nodular regenerative hyperplasia could not be excluded due to inconclusive pathological findings. The mean 6-thioguanine dosage, 6-thioguaninenucleotides level, duration of use and cumulative dosage were 19.5mg, 564 pmol/8 x 10(8) RBC, 38 months and 22491 mg, respectively.. We have demonstrated that low-dose 6-thioguanine maintenance therapy in inflammatory bowel disease patients is not likely to be associated with induction of nodular regenerative hyperplasia. The induction of nodular regenerative hyperplasia appears to be 6-thioguanine dose or 6-thioguaninenucleotides level dependent.

Topics: Adult; Aged; Antimetabolites, Antineoplastic; Female; Humans; Hyperplasia; Inflammatory Bowel Diseases; Liver; Male; Middle Aged; Prospective Studies; Thioguanine; Treatment Outcome

6-Thioguanine (6-TG) seems to be an attractive alternative in both AZA- and 6-MP-intolerant and -resistant IBD populations. However, little is known of 6-TG pharmacokinetics, metabolite levels, and their correlation with drug efficacy and toxicity in IBD patients. This study reports the 6-TG pharmacokinetics in a population of IBD patients and the predictive value of metabolite concentrations. Red blood cell (RBC) 6-thioguanine nucleotide (6-TGN) concentrations were measured in 28 IBD patients at t = 1, 2, 4, and 8 weeks after starting 6-TG, 20 mg once daily. Outcome measures included mean 6-TGN concentrations (+/-95% confidence interval [CI95%]) and their associations with TPMT genotype, 6-TG dose, and hematological, hepatic, pancreatic, and efficacy parameters during the 8 week period. Steady-state 6-TGN concentrations were reached after 4 weeks, indicating a half-life of approximately 5 days, and measured 856 (CI95% 715-997) pmol/8 x 10 RBCs. Large interpatient variability occurred at all time-points. No correlation was found between steady-state 6-TGN concentrations and drug dose per kilogram body weight. No significant differences in 6-TGN concentrations were found between patients with adverse events and patients without any event. Also, mean 6-TGN concentrations did not differ in patients with active disease versus patients in remission. In IBD patients on 6-TG treatment, large interindividual differences in metabolite concentrations occur. In our population, we could not demonstrate a clear relationship between 6-TGN concentrations on one hand and toxicity and efficacy on the other, as exist in AZA- and 6-MP-treated patients.

Topics: Adult; Aged; Aged, 80 and over; Antimetabolites, Antineoplastic; Drug Monitoring; Female; Humans; Inflammatory Bowel Diseases; Male; Middle Aged; Prospective Studies; Thioguanine

In vitro studies suggest interactions between mesalazine (mesalamine) and thiopurines by thiopurine S-methyltransferase (TPMT) inhibition, influencing the balance of hepatotoxic 6-methylmercaptopurine ribonucleotide and immunosuppressive tioguanine (thioguanine) metabolites.. To examine the in vivo pharmacokinetic interaction between mesalazine and mercaptopurine.. A prospective study was performed in quiescent inflammatory bowel disease patients using the combination of mercaptopurine and mesalazine. Laboratory parameters, 6-methylmercaptopurine ribonucleotide and tioguanine levels and thiopurine S-methyltransferase activity in erythrocytes were measured at stable medication, after mesalazine discontinuation and mesalazine reintroduction, further mercaptopurine was continued.. Seventeen patients were participated. Mean mercaptopurine dose was 0.78 mg/kg/day and median of mesalazine dose was 3000 mg/day. After mesalazine discontinuation, mean tioguanine levels changed significantly from 262 to 209 pmol/8 x 10(8) red blood cell, increasing to 270 after reintroduction. Mean 6-methylmercaptopurine ribonucleotide levels were 1422, 2149 and 1503 pmol/8 x 10(8) red blood cell respectively. Mean 6-methylmercaptopurine ribonucleotide/tioguanine ratio increased significantly from 6.3 at baseline to 11.2. Mean baseline thiopurine S-methyltransferase activity was 0.58 pmol/10(6) red blood cell/h and stable. All patients had wild-type thiopurine S-methyltransferase genotypes however, leucocyte counts were stable.. A significantly higher tioguanine levels and improving 6-methylmercaptopurine ribonucleotide/tioguanine ratio were found during mesalazine/mercaptopurine combination. Theoretically, mesalazine inhibits thiopurine S-methyltransferase activity. In vivo thiopurine S-methyltransferase activity did not change, however.. Mesalazine has synergistic effects on mercaptopurine therapy, but the mechanism is unclear. Combining these drugs may be further indication for mesalazine in inflammatory bowel disease treatment.

Topics: Adult; Anti-Inflammatory Agents, Non-Steroidal; Antimetabolites; Antimetabolites, Antineoplastic; Drug Combinations; Humans; Inflammatory Bowel Diseases; Mercaptopurine; Mesalamine; Prospective Studies; Thioguanine

6-Mercaptopurine (6-MP) and azathioprine (AZA) have proven efficacy in the treatment of inflammatory bowel disease (IBD). However, adverse events leading to discontinuation may occur in 10-20% of patients. The efficacy of AZA and 6-MP is based on formation of their active metabolites, the 6-thioguaninenucleotides (6-TGNs). Therefore, 6-thioguanine (6-TG), an agent leading more directly to the formation of 6-TGNs and until recently used only in patients suffering from leukaemia, may be an alternative in AZA or 6-MP intolerance. The purpose of our study was to assess the short-term safety of 6-TG.. Thirty-two IBD patients with previously established AZA or 6-MP intolerance were treated with 6-TG in doses of 20 mg (n = 19) or 40 mg (n = 13) once daily. Safety parameters were obtained at 0, 1, 2, 4 and 8 weeks after start of medication. Primary outcome measures were the ability to tolerate 6-TG and the occurrence of adverse events. Secondary outcome definitions included laboratory parameters.. Twenty-six (81%) patients were able to tolerate 6-TG during the first 8 weeks. In three of six patients, side effects leading to discontinuation were probably (n = 2) or obviously (n = 1) related to 6-TG. No clinically relevant haematological events or hepatotoxicity occurred in the observed period. Steady-state 6-TG levels were significantly higher with 40 mg once daily (1621 +/- 828 picomol/8 x 10(8) red blood cells (RBC)) than with 20 mg once daily (937 +/- 325 picomol/8 x 10(8) RBC; n = 0.001).. 6-TG treatment seems promising in AZA- or 6-MP-intolerant IBD patients. However, long-term safety and efficacy have yet to be determined.

Topics: Adult; Azathioprine; Chemical and Drug Induced Liver Injury; Dose-Response Relationship, Drug; Drug Monitoring; Erythrocytes; Female; Gastrointestinal Agents; Humans; Immunosuppressive Agents; Inflammatory Bowel Diseases; Male; Mercaptopurine; Middle Aged; Prospective Studies; Thioguanine

The effects of 6-mercaptopurine (6-MP) are mediated via its intracellular conversion to 6-thioguanine (6-TG) and 6-methylmercaptopurine (6-MMP) nucleotide metabolites, the latter genetically controlled by thiopurine methyltransferase (TPMT). We sought to determine optimal therapeutic 6-MP metabolite levels and their correlation with medication-induced toxicity and TPMT genotype.. Therapeutic response was determined in 92 pediatric patients with inflammatory bowel disease coincidentally with hematologic, pancreatic, and hepatic laboratory parameters, and compared with erythrocyte metabolite levels and TPMT genotype.. Clinical response was highly correlated with 6-TG levels (P < 0.0001) but not with any other variable, including 6-MMP levels, drug dose, gender, and concurrent medications. The frequency of therapeutic response increased at 6-TG levels > 235 pmol/8 x 10(8) erythrocytes (P < 0.001). Hepatotoxicity correlated with elevated 6-MMP levels (>5700 pmol/8 x 10(8) erythrocytes; P < 0.05). Although leukopenia was associated with higher 6-TG levels (P < 0.03), it was observed in only 8% of responders. Patients heterozygous for TPMT (8/92) had higher 6-TG levels (P < 0.0001), and all responded to therapy.. 6-MP metabolite levels and TPMT genotyping may assist clinicians in optimizing therapeutic response to 6-MP and identifying individuals at increased risk for drug-induced toxicity.

Topics: Adolescent; Child; Child, Preschool; Dose-Response Relationship, Drug; Female; Genotype; Humans; Immunosuppressive Agents; Infant; Inflammatory Bowel Diseases; Leukopenia; Liver; Male; Mercaptopurine; Mesalamine; Methyltransferases; Prospective Studies; Thioguanine; Treatment Outcome

Thioguanine is an alternative thiopurine for inflammatory bowel disease (IBD) patients.. To evaluate the short-term efficacy and safety of low-dose therapeutic drug-monitored (TDM) thioguanine.. A retrospective evaluation of IBD patients intolerant to conventional thiopurines started on thioguanine from 2017 to 2019 with dosing guided by TDM was conducted. Clinical response was defined for ulcerative colitis (UC) as a reduction of partial Mayo score ≥3 with reduction in rectal bleeding score of at least 1 and a final rectal bleeding subscore of 0-1 at Week 12 of therapy. Crohn disease (CD) response was defined as a reduction of Harvey-Bradshaw index ≥3 (HBI) at Week 12 of therapy. Remission was defined in UC as partial Mayo score of <2 and in CD as HBI score of <5.. Forty-six patients were included in the study. The median thioguanine dose was 20 mg/day (standard deviation 7.3; range: 10-40 mg/day) with a median 6-thioguanine nucleotide level of 577 pmol/8 × 108 (interquartile range (IQR) IQR 378.5-878.75) for CD and 677.5 pmol/8 × 108 (IQR 523.25-842.25) for UC. The overall clinical response rate was 62% (13/21), intention to treat (ITT). Maintenance of remission was 76% (19/25, ITT). Thirty-seven percent (17/46) of patients experienced an adverse effect. No early cases of nodular regenerative hyperplasia (NRH) were seen.. Thioguanine was tolerated well in 63% of patients. A clinical response was seen in 62% of patients, and maintenance of remission was high at 76%. No cases of early NRH were seen. Longer-term follow up is required to ensure safety and to assess durability of response.

Topics: Colitis, Ulcerative; Crohn Disease; Drug Monitoring; Humans; Inflammatory Bowel Diseases; Retrospective Studies; Thioguanine

Topics: Colitis; Colitis, Ulcerative; Drug Development; Humans; Inflammatory Bowel Diseases; Thioguanine

Safety of thioguanine in pregnant patients with inflammatory bowel disease [IBD] is sparsely recorded. This study was aimed to document the safety of thioguanine during pregnancy and birth.. In this multicentre case series, IBD patients treated with thioguanine during pregnancy were included. Data regarding disease and medication history, pregnancy course, obstetric complications, and neonatal outcomes were collected.. Data on 117 thioguanine-exposed pregnancies in 99 women were collected. Most [78%] had Crohn's disease and the mean age at delivery was 31 years. In 18 pregnancies [15%], IBD flared. Obstetric and infectious complications were seen in 15% [n = 17] and 7% [n = 8] of pregnancies, respectively. Ten pregnancies [8.5%] resulted in a first trimester miscarriage, one in a stillbirth at 22 weeks of gestational age and one in an induced abortion due to trisomy 21. In total, 109 neonates were born from 101 singleton pregnancies and four twin pregnancies. One child was born with a congenital abnormality [cleft palate]. In the singleton pregnancies, 10 children were born prematurely and 10 were born small for gestational age. Screening for myelosuppresion was performed in 16 neonates [14.7%]; two had anaemia in umbilical cord blood. All outcomes were comparable to either the general Dutch population or to data from three Dutch cohort studies on the use of conventional thiopurines in pregnant IBD patients.. In this large case series, the use of thioguanine during pregnancy is not associated in excess with adverse maternal or neonatal outcomes.

Topics: Abortion, Spontaneous; Adult; Child; Female; Humans; Infant, Newborn; Inflammatory Bowel Diseases; Pregnancy; Pregnancy Complications; Pregnancy Outcome; Stillbirth; Thioguanine

Thioguanine is a well-tolerated and effective therapy for inflammatory bowel disease [IBD] patients. Prospective effectiveness data are needed to substantiate the role of thioguanine as a maintenance therapy for IBD.. IBD patients who previously failed azathioprine or mercaptopurine and initiated thioguanine were prospectively followed for 12 months starting when corticosteroid-free clinical remission was achieved (Harvey-Bradshaw Index [HBI] ≤ 4 or Simple Clinical Colitis Activity Index [SCCAI] ≤ 2). The primary endpoint was corticosteroid-free clinical remission throughout 12 months. Loss of clinical remission was defined as SCCAI > 2 or HBI > 4, need of surgery, escalation of therapy, initiation of corticosteroids or study discontinuation. Additional endpoints were adverse events, drug survival, physician global assessment [PGA] and quality of life [QoL].. Sustained corticosteroid-free clinical remission at 3, 6 or 12 months was observed in 75 [69%], 66 [61%] and 49 [45%] of 108 patients, respectively. Thioguanine was continued in 86 patients [80%] for at least 12 months. Loss of response [55%] included escalation to biologicals in 15%, corticosteroids in 10% and surgery in 3%. According to PGA scores, 82% of patients were still in remission after 12 months and QoL scores remained stable. Adverse events leading to discontinuation were reported in 11%, infections in 10%, myelo- and hepatotoxicity each in 6%, and portal hypertension in 1% of patients.. Sustained corticosteroid-free clinical remission over 12 months was achieved in 45% of IBD patients on monotherapy with thioguanine. A drug continuation rate of 80%, together with favourable PGA and QoL scores, underlines the tolerability and effectiveness of thioguanine for IBD.

Topics: Azathioprine; Colitis; Humans; Immunosuppressive Agents; Inflammatory Bowel Diseases; Mercaptopurine; Prospective Studies; Quality of Life; Thioguanine

Topics: Azathioprine; Child; Drug Monitoring; Humans; Inflammatory Bowel Diseases; Mercaptopurine; Thioguanine

Topics: Azathioprine; Child; Drug Monitoring; Humans; Inflammatory Bowel Diseases; Mercaptopurine; Thioguanine

Exactly 70 years ago [1951] mercaptopurine was discovered by Gertrude Elion as a novel treatment option for acute leukaemia. A total of three thiopurines (also thioguanine [1950] and azathioprine [1957]) were developed over time. These immunosuppressive drugs were also successfully introduced a few decades later to prevent rejection of transplanted organs and to treat several autoimmune diseases. For her discovery of thiopurines and other antimetabolite drugs, in 1988 Elion was rewarded, together with George Hitchings and James Black, with the Nobel Prize in Physiology or Medicine. Important steps have been made in recent years to unravel its metabolism, mode of action and pharmacogenetics. Today thiopurine [based] therapy remains an essential immunosuppressive approach in treating patients with inflammatory bowel disease.

Topics: Antimetabolites; Azathioprine; Female; Humans; Immunosuppressive Agents; Inflammatory Bowel Diseases; Mercaptopurine; Thioguanine

Thioguanine (TG) has been shown as a safe alternative in adults with inflammatory bowel disease (IBD) who did not tolerate conventional thiopurines [azathioprine (AZA)/mercaptopurine]. However, data in pediatric IBD are scarce. Therefore, we aimed to assess the safety of TG as maintenance therapy.. A retrospective, multicenter cohort study of children with IBD on TG was performed in the Netherlands. TG-related adverse events (AE) were assessed and listed according to the common terminology criteria for AE.. Thirty-six children with IBD (median age 14.5 years) on TG (median dose 15 mg/day) were included in 6 centers. Five AE occurred during follow-up [pancreatitis (grade 3), hepatotoxicity (grade 3) (n = 2), Clostridium difficile infection (grade 2), and abdominal pain (grade 2)]. All patients (n = 8) with a previously AZA-induced pancreatitis did not redevelop pancreatitis on TG.. In pediatric IBD, TG seems a safe alternative in case of AZA-induced pancreatitis. Further research assessing long-term TG-related safety and efficacy is needed.

Topics: Adolescent; Adult; Azathioprine; Child; Chronic Disease; Cohort Studies; Humans; Immunosuppressive Agents; Inflammatory Bowel Diseases; Mercaptopurine; Pancreatitis; Retrospective Studies; Thioguanine

The thiopurine derivatives azathioprine (AZA), mercaptopurine (MP) and tioguanine (TG) remain standard treatment of inflammatory bowel disease (IBD). The immune suppressive effect of thiopurines is primarily based on blocking the Ras-related C3 botulinum toxin substrate 1 (Rac1) causing apoptosis of T lymphocytes by inhibition of the phosphorylated downstream transcription factor Signal Transducer and Activator of Transcription 3 (pSTAT3). A functional pharmacodynamic marker in T lymphocytes may be useful to predict therapeutic outcome of thiopurine therapy. The aim of this study was to explore whether protein levels of Rac1 and pSTAT3 in T lymphocytes may be applied as a specific pharmacodynamic marker for thiopurine therapy in IBD patients. Rac1 and pSTAT3 protein levels in T lymphocytes were explored in 57 IBD patients (median age 51 years, 56% female), subdivided into six groups based on IBD activity and its treatment: patients with active disease without IBD maintenance medication (1) or patients in remission on AZA/MP (2), TG (3), infliximab (IFX) (4), thiopurine and IFX combination-treatment (5) or without IBD medication (6). Reference values were obtained from healthy subjects. Rac1 and pSTAT3 protein levels in T lymphocytes from patients on thiopurine monotherapy (group 2 and 3) were compared to the other groups, and to healthy subjects. Absolute Rac1 and pSTAT3 protein levels showed no differences between the thiopurine monotherapy groups when compared to patients with active disease. However, the ratio of Rac1 and pSTAT3 protein levels was lower in thiopurine patients groups compared to patients with active disease. Rac1-corrected pSTAT3 protein levels may serve as a pharmacodynamic marker of thiopurine monotherapy and may be a potential tool to predict therapeutic effectiveness in IBD patients.

Topics: Azathioprine; Female; Humans; Immunosuppressive Agents; Inflammatory Bowel Diseases; Infliximab; Male; Mercaptopurine; Middle Aged; rac1 GTP-Binding Protein; STAT3 Transcription Factor; T-Lymphocytes; Thioguanine

Thiopurine drugs azathioprine (AZA) and 6-mercaptopurine (6-MP) are used extensively in pediatric and adult patients with inflammatory and neoplastic diseases. They are metabolized to 6-thioguanine nucleotides (6-TGN) or to 6-methyl-mercaptopurine nucleotides (6-MMPN). The balance between 6-TGN and 6-MMPN is highly variable and monitoring is recommended, but its benefit in outcome gives rise to conflicting results, potentially increased by differences in quantifying 6-MP metabolism. Our aim was to report (1) the HPLC-UV procedure used in our laboratory to quantify red blood cells (RBCs) with 6-TGN and 6-MMPN (as its derivate: 6-MMP(d)) in patients treated with thiopurines and (2) additional tests, sometimes confirmatory, to improve method standardization. The comparison of two methods to count RBCs shows that metabolite concentrations were slightly lower in the washed and resuspended RBCs than in whole blood. Perchloric acid (0.7 M), dithiothreitol (DTT, final 0.013 M sample concentration) and 60 min hydrolysis were selected for acid hydrolysis. (3) Monitoring data from 83 patients receiving AZA or 6-MP showed that at steady state, only 53/183 (29%) had 6-TGN and 6-MMPN in the recommended therapeutic range. Our method is discussed in light of the technical conditions and sample stability data from 17 publications identified since the first analytical report in 1987. Monitoring data demonstrate, if required, that inter-patient variability in 6-TGN and 6-MMPN concentrations is high in samples from treated patients.

Topics: Adult; Azathioprine; Child; Chromatography, High Pressure Liquid; Dithiothreitol; Erythrocytes; Humans; Immunosuppressive Agents; Inflammatory Bowel Diseases; Mercaptopurine; Nucleotides; Thioguanine

In inflammatory bowel disease (IBD), conventional thiopurine users cease treatment in 60% of cases within 5 years, mostly because of adverse events or nonresponse. In this study, the authors aimed to investigate the role of 6-thioguanine nucleotide (TGN) measurements, geno/phenotyping of thiopurine S-methyltransferase (TPMT), and their mutual relationship with TG therapy in IBD.. An international retrospective, multicenter cohort study was performed at 4 centers in the Netherlands (Máxima Medical Centre) and the United Kingdom (Guy's and St. Thomas' Hospital, Queen Elizabeth Hospital, and East Surrey Hospital).. Overall, 526 6-TGN measurements were performed in 316 patients with IBD. The median daily dosage of TG was 20 mg/d (range 10-40 mg/d), and the median duration of TG use was 21.1 months (SD, 28.0). In total, 129 patients (40.8%) had a known TPMT status. In the variant-type and wild-type TPMT genotype metabolism groups, median 6-TGN values were 1126 [interquartile range (IQR) 948-1562] and 467.5 pmol/8 × 10E8 red blood cells (RBCs) (IQR 334-593). A significant difference was observed between the 2 groups (P = 0.0001, t test). For TPMT phenotypes, in the slow, fast, and normal metabolism groups, the median 6-TGN values were 772.0 (IQR 459-1724), 296.0 (IQR 200-705), and 774.5 pmol/8 × 10E8 RBCs (IQR 500.5-981.5), with a significant difference observed between groups (P < 0.001, analysis of variance).. Our findings indicated that TPMT measurements at TG initiation can be useful but are not necessary for daily practice. TPMT genotypes and phenotypes are both associated with significant differences in 6-TGN levels between metabolic groups. However, the advantage of TG remains that RBC 6-TGN measurements are not crucial to monitor treatments in patients with IBD because these measurements did not correlate with laboratory result abnormalities. This presents as a major advantage in countries where patients cannot access these diagnostic tests.

Topics: Adult; Azathioprine; Female; Genotype; Guanine Nucleotides; Humans; Immunosuppressive Agents; Inflammatory Bowel Diseases; Male; Mercaptopurine; Methyltransferases; Middle Aged; Phenotype; Retrospective Studies; Thioguanine; Thionucleotides

Despite new treatment options for inflammatory bowel disease (IBD), conventional thiopurines remain a common treatment option for maintaining remission, particularly in non-Westernized countries. Therapeutic drug monitoring (TDM) is advised in standard care for optimizing therapy strategies to improve effectiveness, reveal nonadherence, and reduce toxicity. Still, the rationale of TDM is debated.. Key insights on TDM of thiopurine metabolites are discussed. The pharmacology of thiopurines is described, emphasizing the interindividual differences in pharmacogenetics, pharmacokinetics, and pharmacodynamics. Pharmacological differences between conventional thiopurines and tioguanine are outlined. Finally, several optimization strategies for thiopurine therapy in IBD are discussed.. TDM has been a useful, but limited, tool to individualize thiopurine therapy. Pharmacokinetic data on the active thiopurine metabolites, derived from measurements in erythrocytes, associated with clinical response only partially predict effectiveness and toxicity. An additional pharmacodynamic marker, such as Rac1/pSTAT3 expression in leukocytes, may improve applicability of TDM in the future.

Topics: Azathioprine; Drug Monitoring; Humans; Inflammatory Bowel Diseases; Mercaptopurine; Thioguanine

Both tioguanine and low-dose thiopurines combined with allopurinol (LDTA) can be considered for the treatment of inflammatory bowel disease (IBD) when conventional thiopurines fail due to adverse events.. To compare the safety of tioguanine and LDTA in IBD patients.. Inflammatory bowel disease patients who failed conventional thiopurines due to adverse events and initiated LDTA in standard care were identified in the prospective ICC Registry. IBD patients who failed conventional thiopurines due to adverse events and initiated tioguanine were enrolled in three university hospitals. Patients on concomitant biologicals were excluded. The primary outcome was discontinuation of therapy due to adverse events. Secondary outcomes included: safety outcomes and surgery-, biological- and corticosteroid-free clinical remission (physician global assessment = 0) after 104 weeks. Both multiple logistic regression and propensity score matching were used to correct for confounders.. In total, 182 IBD patients treated with tioguanine (n = 94) or LDTA (n = 88) were included with a median follow-up of 104 weeks (IQR 91-104). Of these, 19% (tioguanine: 20%, LDTA: 18%) of patients discontinued therapy due to adverse events. After adjusting for confounders, there were no differences in terms of discontinuation rate due to adverse events (OR 0.50, 95% CI 0.15-1.68, P = 0.26), adverse events (OR 0.89, 95% CI 0.44-1.81, P = 0.75), infections (OR 1.05, 95% CI 0.40-2.73, P = 0.93), hospitalisations (OR 2.00, 95% CI 0.64-6.23, P = 0.23) or clinical remission (OR 0.74, 95%CI 0.33-1.68, P = 0.48). All results are comparable with the propensity score matched cohort.. Nineteen percent of IBD patients with prior failure to conventional thiopurines due to adverse events discontinued therapy with tioguanine or LDTA due to adverse events. Either therapy may be considered before escalating to biological therapy.

Topics: Adult; Allopurinol; Cohort Studies; Dose-Response Relationship, Drug; Drug Therapy, Combination; Female; Humans; Inflammatory Bowel Diseases; Male; Middle Aged; Netherlands; Prospective Studies; Purines; Registries; Thioguanine; Treatment Outcome

Thioguanine (TG) is a thiopurine which has been used for patients with inflammatory bowel disease (IBD), who have failed azathioprine (AZA) or mercaptopurine (MP) due to adverse events or suboptimal response. Its widespread use has been hampered due to concerns about nodular regenerative hyperplasia (NRH) of the liver. The aim of this study was to investigate the long-term efficacy and safety of low-dose TG therapy in IBD patients failing AZA and MP.. A retrospective multicentre study was performed in IBD patients who failed prior treatment with conventional thiopurines with or without following immunomodulation (thiopurine-allopurinol, biologicals, methotrexate, tacrolimus) and were subsequently treated with TG as rescue monotherapy between 2003 and 2019 at three hospitals in the United Kingdom. Clinical response, adverse events, laboratory results, imaging and liver biopsies were retrospectively collected.. Long-term follow-up suggests that TG can be an effective and well-tolerated therapy in more than half of difficult-to-treat and multi-therapy failing IBD patients. Findings of this study indicate that TG can be used safely and the occurrence of hepatotoxicity was low. The incidence rate of NRH was within the background incidence.

Topics: Azathioprine; Female; Humans; Immunosuppressive Agents; Inflammatory Bowel Diseases; Male; Mercaptopurine; Pharmaceutical Preparations; Retrospective Studies; Thioguanine; Treatment Outcome; United Kingdom

Topics: Humans; Immunologic Factors; Inflammatory Bowel Diseases; Mercaptopurine; Thioguanine

Azathioprine and mercaptopurine are widely used in the treatment of inflammatory bowel disease. However, its use is limited by adverse drug event related to the relatively narrow therapeutic index of the active metabolites. Several patients discontinue treatment because of intolerable adverse events or toxicity such as leucopenia and hepatotoxicity. High 6-thioguanine nucleotides and 6-methylmercaptopurine ribonucleotides levels are associated with toxicity. Variations in the thiopurine S-methyltransferase (TPMT) gene can lead to diminished TPMT enzyme activity and to an increased incidence of myelotoxicity due to high 6-methylmercaptopurine ribonucleotides levels after treatment with azathioprine and mercaptopurine. Unlike azathioprine and mercaptopurine, thioguanine is more directly metabolized to the active metabolites without formation of the toxic 6-methylmercaptopurine ribonucleotides. Taking this into account, it seems likely that thioguanine is less associated with myelotoxicity due to TPMT deficiency. However, we report the case of a Crohn's disease patient with life-threatening complications on 6TG treatment due to TPMT deficiency. Our patient developed a severe pancytopenia on thioguanine therapy, with 6-thioguanine nucleotides levels more than 10 times higher than the upper limit of the therapeutic window and was found to be a TPMT poor metabolizer (TPMT *3A/*3A). This case strongly illustrates that knowledge of TPMT enzyme activity is very important in the use of all thiopurines, including thioguanine. In conclusion, clinicians should be aware of the impact of TPMT deficiency on the metabolism of thioguanine and should consider performing preemptive TPMT genotyping in combination with frequent blood test monitoring when using thiopurines in general.

Topics: Aspergillosis; Drug Hypersensitivity; Female; Humans; Inflammatory Bowel Diseases; Middle Aged; Pancytopenia; Purine-Pyrimidine Metabolism, Inborn Errors; Severity of Illness Index; Thioguanine

Therapeutic drug monitoring of thiopurine erythrocyte levels is not available in all centers and it usually requires quite a long time to obtain the results. The aims of this study were to build a model predicting low levels of 6-thioguanine and 6-methylmercaptopurine in pediatric inflammatory bowel disease (IBD) patients and to build a model to predict nonadherence in patients treated with azathioprine (AZA).. The study consisted of 332 observations in 88 pediatric IBD patients. Low AZA dosing was defined as 6-thioguanine levels <125 pmol/8 × 10 erythrocytes and 6-methylmercaptopurine levels <5700 pmol/8 × 10 erythrocytes. Nonadherence was defined as undetectable levels of 6-thioguanine and 6-methylmercaptopurine <240 pmol/8 × 10 erythrocytes. Data were divided into training and testing part. To construct the model predicting low 6-thioguanine levels, nonadherence, and the level of 6-thioguanine, the modification of random forest method with cross-validation and resampling was used.. The final models predicting low 6-thioguanine levels and nonadherence had area under the curve, 0.87 and 0.94; sensitivity, 0.81 and 0.82; specificity, 0.80 and 86; and distance, 0.31 and 0.21, respectively, when applied on the testing part of the dataset. When the final model for prediction of 6-thioguanine values was applied on testing dataset, a root-mean-square error of 110 was obtained.. Using easily obtained laboratory parameters, we constructed a model with sufficient accuracy to predict patients with low 6-thioguanine levels and a model for prediction of AZA treatment nonadherence (web applications: https://hradskyo.shinyapps.io/6TG_prediction/ and https://hradskyo.shinyapps.io/Non_adherence/).

Topics: Adolescent; Area Under Curve; Child; Drug Monitoring; Erythrocytes; Female; Humans; Immunosuppressive Agents; Inflammatory Bowel Diseases; Male; Medication Adherence; Mercaptopurine; Models, Biological; Predictive Value of Tests; Sensitivity and Specificity; Thioguanine

Topics: Adolescent; Adult; Aged; Azathioprine; Female; Humans; Hyperplasia; Inflammatory Bowel Diseases; Liver Diseases; Male; Mercaptopurine; Middle Aged; Thioguanine; Young Adult

Sperm DNA integrity, concentration, and motility are suspected to be altered by thiopurines (azathioprine [AZA] and 6-mercaptopurine [6-MP]). We investigated the impact of thiopurines on semen quality in men with inflammatory bowel disease [IBD], by a comprehensive panel of semen analyses.. Semen from 40 men with IBD, in remission on AZA/6-MP therapy, was prospectively collected and compared with samples from 40 healthy volunteers. Paired samples [off and on AZA/6-MP] were obtained from a subset of IBD patients, and blood and semen were collected to determine 6-MP transmission to the ejaculate. Sperm DNA fragmentation was evaluated via sperm chromatin structure assay [SCSA] and Comet analysis. Conventional World Health Organization [WHO] parameters, i.e. semen volume and sperm concentration, motility, and morphology, were assessed. Additionally, we measured thioguanine nucleotide [TGN] incorporation in sperm cell DNA.. Sperm DNA fragmentation levels did not differ between men with IBD on AZA/6-MP and healthy volunteers when evaluated by SCSA [p = 0.23] and Comet analysis [p = 0.72]. IBD patients on AZA/6-MP had significantly lower total and progressive sperm motility than healthy volunteers [48.5% versus 64.5%, p = 0.0003; 27.4% versus 43.3%, p = 0.0004; respectively], with no differences in concentration, volume, or morphology. The same trend was observed in the 10 paired samples. TGN incorporation was not detectable in sperm DNA, but 6-MP was detected in seminal plasma and correlated to blood levels [rs = 0.79, p = 0.02].. Thiopurines do not increase sperm DNA fragmentation but may impair sperm motility in this IBD cohort. Our findings support existing epidemiological data that thiopurine therapy is safe during preconception and should not be abandoned.

Topics: Adolescent; Adult; Azathioprine; Case-Control Studies; DNA; DNA Fragmentation; Humans; Immunosuppressive Agents; Inflammatory Bowel Diseases; Male; Mercaptopurine; Nucleotides; Prospective Studies; Semen; Semen Analysis; Spermatozoa; Thioguanine; Young Adult

Thiopurine metabolite monitoring to proactively dose optimize to achieve therapeutic levels has not been used consistently, and it is unclear if this would lead to better outcomes. We aimed to compare 6-month outcomes between standard and optimized dosing strategies and define long-term predictors of thiopurine durability.. Two hundred sixteen pediatric IBD patients with at least 2 6-thioguanine nucleotide (6-TGN) levels were grouped for analysis by start dose: >2.5 mg/kg/day AZA (group 1) or <2.5 mg/kg/day (group 2) and further subgrouped depending on whether dosing was optimized to achieve 6-TGN >235 pmol/8 × 108 RBC. The metabolites, 6TGN and 6MMP, were univariate and multivariate analyses tested associations among metabolite levels, laboratory data, and the primary outcome of 6-month steroid-free clinical remission (SFR) (HBI ≤4 for CD; partial Mayo Score [pMS] ≤2 for UC). Thiopurine durability was measured using Kaplan Maier survival analysis.. 6-MP, azathioprine, pediatrics, therapeutic drug monitoring, pediatrics were measured a median 59 (43-76) days after initiation of thiopurine. Both dosing strategies led to similar initial 6-TGN levels (group 1 = median 209 [IQR: 155-272] with 25% of patients >235; group 2 = 196 [139-274] with 29% >235). Steroid-free clinical remission was achieved in 74% of the 180 still on thiopurines at 6 months. Start dose was not associated with 6-month SFR-73% in group 1 and 77% in group 2 within those on thiopurines at 6 months (P = 0.61). Fixed- and optimized-dosing subgroups had similar 6-month 6-TGN levels, SFR rate, and percentage 6-TGN > 235. Only 6-TGN level >235 at 6 months predicted thiopurine durability (3 years [1.7-7.7] vs 2.5 years [0.83-5]; log-rank P < 0.001), and this did not retain significant in a multivariate model. Initial dosing strategy, first 6-TGN level, 6-month SFR, 6MMP:6TGN ratio, and delta-MCV did not predict durability. The rate of adverse events was 22%.. Steroid-free clinical remission and 6-TGN levels at 6 months were no different between a standardized, fixed dosing strategy and a metabolite-driven, optimized dosing strategy.

Topics: Adolescent; Azathioprine; Child; Drug Monitoring; Female; Follow-Up Studies; Humans; Immunosuppressive Agents; Inflammatory Bowel Diseases; Male; Mercaptopurine; Prognosis; Retrospective Studies; Thioguanine

Adherence to maintenance medication for inflammatory bowel disease (IBD) is essential for disease control, albeit often poor. Adherence can be measured by drug metabolites, self-report tools, and prescription data. The aim of this study was to test implementation of self-report tools in IBD clinics by evaluating consistency and to validate them by correlation with drug metabolite levels and medication possession ratios (MPRs).. Ambulatory IBD patients on thiopurine maintenance therapy for >3 months were recruited. Patients self-reported adherence using a visual analog scale (VAS) and Medication Adherence Report Scale (MARS). Thiopurine metabolites levels were assessed using blood, and MPRs were calculated from patient records as the reference standard. Consistency was assessed by McNemar's test (primary outcome), and correlation analysis was performed using Pearson tests.. Of 96 patients (58 Crohn's disease, 33 ulcerative colitis, 5 IBD unclassified) 16.6% were classified as nonadherent based on thiopurine metabolites, 14.9% based on VAS, 13.2% based on MARS, and 22.9% based on MPR. VAS and MARS were consistent with thiopurine metabolites (McNemar test P = 0.79, P = 0.45). All 4 methods were consistent with each other when compared directly 1 to 1. Spearman's analysis demonstrated that all 4 methods significantly correlated with each other: (correlation between VAS and thiopurine metabolites: rho = 0.435; P < 0.001; and correlation between MARS and thiopurine metabolites: rho = 0.29; P = 0.005).. Self-report tools correlate significantly with thiopurine metabolites and medication possession ratios. The Medication Adherence Report Scale and VAS are validated adherence assessment tools for IBD and can be used as simple screening tools in clinical practice.

Topics: Adolescent; Adult; Aged; Aged, 80 and over; Antimetabolites, Antineoplastic; Azathioprine; Female; Follow-Up Studies; Humans; Immunosuppressive Agents; Inflammatory Bowel Diseases; Male; Medication Adherence; Middle Aged; Prognosis; Self Report; Thioguanine; Visual Analog Scale; Young Adult

Topics: Antibodies, Antineutrophil Cytoplasmic; Antibodies, Fungal; Blood Sedimentation; Child; Clinical Laboratory Services; England; Feces; Health Services Accessibility; Hematologic Tests; Humans; Inflammatory Bowel Diseases; Infliximab; Laboratories; Leukocyte L1 Antigen Complex; Methyltransferases; Orosomucoid; Saccharomyces cerevisiae; Serologic Tests; Surveys and Questionnaires; Thioguanine; Viscosity

Tioguanine (or thioguanine) is an alternative drug for IBD patients who fail prior conventional immunomodulating therapy.. To report effectiveness, safety and therapeutic drug monitoring in a cohort of patients with prolonged tioguanine maintenance therapy.. In this nationwide, multicentre study, medical records of tioguanine- using IBD patients were retrospectively reviewed. Response to therapy was defined as clinical effectiveness without (re)initiation of corticosteroids, concurrent biological therapy or surgical intervention. All adverse events that occurred during the follow-up were listed and graded according to the common terminology criteria (CTC).. Two hundred and seventy-four patients (female 63%, Crohn's disease in 68%) were included with median treatment duration of 51 months, 1567 patient-years of follow-up and median 20 mg/d tioguanine dosage. Tioguanine was tolerated in 79%, clinical effectiveness at 6 months was documented in 66% and sustained clinical effectiveness during 12 months in 51% of patients. Forty-one per cent of patients developed adverse events: 5% were graded as severe. Adverse events comprised infection requiring hospitalisation in three and skin cancer in eight patients (two melanomas). Asymptomatic nodular regenerative hyperplasia of the liver occurred in two out of 52 patients with liver biopsies (3.8%) and portal hypertension in three whereof one potentially associated with tioguanine (0.4%). Clinical effectiveness was correlated with 6-thioguanine nucleotide threshold concentrations >682 pmol/8×10. Long-term tioguanine therapy for at least 12 months was effective in 51% and well tolerated as a maintenance treatment for IBD in about 70% of patients. Adverse events were common, but mainly mild or moderate. 6-Thioguanine nucleotide threshold concentration ≥ 700 pmol/8×10

Topics: Adolescent; Adult; Anti-Inflammatory Agents; Drug Monitoring; Female; Guanine Nucleotides; Humans; Inflammatory Bowel Diseases; Male; Middle Aged; Retrospective Studies; Thioguanine; Thionucleotides; Treatment Outcome; Young Adult

Topics: Adult; Biopsy; Chemical and Drug Induced Liver Injury; Cohort Studies; Disease Progression; Female; Focal Nodular Hyperplasia; Humans; Hypertension, Portal; Inflammatory Bowel Diseases; Liver; Male; Middle Aged; Netherlands; Thioguanine

Thiopurines are analogues of endogenous purines. They are pro-drugs which require the purine salvage pathway to convert them to the active drug nucleotides (TGN). These drugs are used to maintain clinical remission in patients with inflammatory bowel diseases. In our recent Gut paper, we showed that thioguanine worked quickly to improve colitis in the absence in the host animal of the key guanine salvage enzyme, hypoxanthine-guanine-phosphoribosyltransferase (HPRT). Current evidence favours the proposition that active drug delivery to the host lacking HPRT requires translocation of TGN-loaded bacteria across the inflamed mucosal barrier, and most likely delivery by phagocytosis. Alternatively, the efficacy of thioguanine in treating colitis could be mediated by modulation of the community of the microbiota in the intestine, or there are novel host pathways for conversion of the thioguanine pro-drug to TGN.

Topics: Administration, Oral; Administration, Rectal; Animals; Autophagy; Colitis; Colon; Disease Models, Animal; Gene Knockout Techniques; Host-Pathogen Interactions; Humans; Hypoxanthine Phosphoribosyltransferase; Inflammatory Bowel Diseases; Mice; Microbiota; Prodrugs; Thioguanine

Inflammatory bowel diseases (IBD) are chronic relapsing disorders of the gastrointestinal tract. Several mouse models for IBD are available, but the acute dextran sulfate sodium (DSS)-induced colitis model is mostly used for preclinical studies. However, this model lacks chronicity and often leads to significant loss of mice. The aim of this study was to establish a refined and translationally relevant model of DSS chronic colitis in BALB/c mice. In the first part, we compared several standard therapeutic (ST) treatments for IBD in the acute DSS colitis model to identify the optimal treatment control for a DSS colitis model as compared to literature data. In the second part, we tested the two most effective ST treatments in a refined model of chronic DSS colitis. Cyclosporine A (CsA) and 6-thioguanine (6-TG) caused considerable reduction of clinical scores in acute DSS colitis. The clinical outcome was confirmed by the results for colon length and by histopathological evaluation. Moreover, CsA and 6-TG considerably reduced mRNA expression of several pro-inflammatory cytokines in spleen and colon. Both compounds also showed a substantial therapeutic effect in the refined model of chronic DSS colitis with regard to clinical scores and histopathology as well as the expression of inflammatory markers. The refined model of chronic DSS colitis reflects important features of IBD and is well suited to test potential IBD therapeutics.

Topics: Animals; Anti-Inflammatory Agents; Chronic Disease; Colitis; Cyclosporine; Dextran Sulfate; Disease Models, Animal; Female; Inflammatory Bowel Diseases; Mice; Mice, Inbred BALB C; Thioguanine

The thiopurines azathioprine and mercaptopurine remain pivotal maintenance treatments in inflammatory bowel disease (IBD); however, up to 15%-20% of patients preferentially produce the hepatotoxic metabolite 6-methylmercaptopurine (6MMP) at the expense of the therapeutic 6-thioguanine nucleotides (6TGN). This metabolic shunting usually begins within 3 months of therapy. We noted patients developing shunting many months or years after starting treatment and aimed to determine how often this late shunting occurs and whether this could be explained by patient factors or concomitant medications.. The New Zealand database of thiopurine metabolite results from 2002 to 2016 (19085 6TGN/6MMP pairs from 7130 patients) was interrogated to identify patients developing a 6MMP/6TGN ratio >20 after at least 4 months treatment. Dosing history, concomitant therapy, and comorbidity data were assessed.. Fifteen percent of database patients developed preferential 6-MMP production, and of these, 29 patients had late-onset shunting with sufficient data available for validation. This extrapolates to 90 patients in total, representing 1.7% of IBD patients on thiopurines, or 10% of all those with preferential 6-MMP production. Time from starting therapy to shunting was 5 months to 10.4 years (median, 21 months). Eleven patients had abnormal liver function when shunting was recognized, all with 6MMP >5900 pmol/8 × 108 red blood cells. No common factors were found to explain the late onset.. Some IBD patients develop preferential 6MMP production many months or years after commencing therapy. This is important when considering frequency of metabolite monitoring, failure of therapy, or abnormal liver function. 10.1093/ibd/izx081_video1izx081.video15746667546001.

Topics: Adult; Aged; Aged, 80 and over; Azathioprine; Female; Humans; Inflammatory Bowel Diseases; Male; Mercaptopurine; Middle Aged; New Zealand; Thioguanine; Young Adult

Thiopurines (TP) represent an important therapeutic tool for the treatment of inflammatory bowel diseases (IBD) in the current situation of rising incidence and health care costs. The results of multiple clinical studies aimed at finding correlations between levels of TP metabolites and response of IBD patients to the treatment are, however, often controversial due to variability in analytical and sample preparation procedures among these studies. In this work, therefore, an updated analytical and sample preparation procedure for therapeutic drug monitoring (TDM) of TP metabolites in blood samples obtained from patients with IBD was proposed to establish a unified protocol. An advanced analytical method based on ion-exchange liquid chromatography hyphenated with tandem mass spectrometry (IEC-ESI-MS/MS) was used for the determination of the profiles of 12 individual TP metabolites in the particular steps of sample preparation procedure including blood collection, red blood cells (RBC) isolation, lysis, and storage. Favorable performance parameters of the IEC-ESI-MS/MS method (LLOQs 1⁻10 nmol/L, accuracy 95⁻105%, intra-day and inter-day precision < 10%, selectivity demonstrated via no sample matrix interferences) and acceptable stability (peak area fluctuations < 15%) of clinical samples under the proposed sample preparation conditions {(i) EDTA anticoagulant tube for the blood collection; (ii) 4 °C and 4 h between the sample collection and RBC isolation; (iii) phosphate-buffered saline for RBC washing and re-suspendation; (iv) -20 °C for RBC lysis and short-term storage; (v) 50 mmol/L phosphate buffer, pH 7.4, 10 mmol/L DTT as a stabilizing medium for TPN in RBC lysates} demonstrated the suitability of such protocol for a well-defined and reliable routine use in studies on thiopurines TDM.

Topics: Adult; Azathioprine; Drug Monitoring; Erythrocytes; Female; Humans; Inflammatory Bowel Diseases; Male; Mercaptopurine; Middle Aged; Thioguanine

Thiopurine therapy can be optimised by determining the concentration of the drug's metabolites.. Retrospective analysis on a prospective database of 31 patients with inflammatory bowel disease who failed therapy with thiopurines. Thiopurine metabolites (6-thioguanine, 6-TGN and 6-methylmercaptopurine, 6-MMP) were measured by high-performance liquid chromatography (Laboratorios Cerba, Barcelona) and treatment was duly adjusted in accordance with the results. Clinical response was reassessed after six months.. Despite the appropriate theoretical dose of thiopurines being administered, the dose was insufficient in 45.6% of patients (nonadherence to treatment suspected in 6.45%) and 16.2% received an excessive dose or the drug was metabolised by other metabolic pathways. After treatment was optimised based on metabolite levels, only 25.8% (8/31) were prescribed a biological agent, while 74.2% of cases (23/31) were managed through dose optimisation alone.. Monitoring thiopurine metabolite levels may help clinicians to assess non-responsive patients before adding or switching to another drug (generally a biological agent), thereby avoiding any additional costs or potential toxicity. This strategy may also help to identify patients receiving an insufficient dose and those with an alternative metabolic pathway, who could be candidates for low-dose AZA with allopurinol, as well as patients who are suspected of being non-adherent. In three out of four patients, switching to a biological agent can be avoided.

Topics: Adult; Aged; Azathioprine; Biotransformation; Dose-Response Relationship, Drug; Drug Monitoring; Female; Humans; Inflammatory Bowel Diseases; Male; Mercaptopurine; Middle Aged; Retrospective Studies; Thioguanine; Young Adult

Thiopurines (azathioprine and mercaptopurine) are frequently used immunosuppressive drugs to maintain remission in patients with inflammatory bowel disease. Half of the conventional thiopurine-derivative users have to discontinue treatment within 5 years, mainly because of intolerable adverse events. Over recent years, different strategies to optimize thiopurine treatment were suggested, yet, studies describing the clinical effectiveness of these strategies remain scarce. The aims of this study were to compare tolerability and sustained clinical benefit of conventional thiopurine derivatives therapy among two 5-year real-life intercept cohorts and to assess the clinical value of specifically allopurinol cotherapy.. In this retrospective single-center cohort study, we analyzed data from patients in whom weight-based thiopurine monotherapy was initiated between 2005 and 2009 (cohort 1) or between 2010 and 2014 (cohort 2). The initiation of the second cohort was synchronic to the start of allopurinol-based optimization in our center. Optimization strategies were extracted from patient charts.. In total, 105 patients were included (60 in cohort 1, and 45 in cohort 2). Metabolite measurement was performed in 37% versus 84% of the patients (P < 0.001). Subsequent optimization strategies were applied in 33% versus 58% of the patients because of inadequate metabolite concentrations, intolerance, or ineffectiveness (P = 0.01). Allopurinol was coadministered to therapy in 18 patients (40%) in the second cohort. Therapy was switched to thioguanine in 11 versus 6 patients (P > 0.05). Overall, total duration was longer in the second cohort (10.8 versus 34.1 months, P < 0.001). The number of ongoing thiopurine users (20% versus 49%) and sustained clinical benefit (13% versus 38%) were higher in the second cohort (both P < 0.05). This was mainly because of a decrease in hepatotoxicity after optimization (P < 0.01).. Optimization of thiopurine therapy by the use of therapeutic drug monitoring with subsequent administration of allopurinol cotherapy successfully enhanced sustained clinical benefit and tolerability in patients with inflammatory bowel disease.

Topics: Adult; Allopurinol; Azathioprine; Drug Monitoring; Drug Therapy, Combination; Drug-Related Side Effects and Adverse Reactions; Female; Humans; Immunosuppressive Agents; Inflammatory Bowel Diseases; Male; Mercaptopurine; Middle Aged; Retrospective Studies; Thioguanine; Treatment Outcome; Young Adult

Early-onset inflammatory bowel disease (IBD) is generally aggressive, with a high probability of complications and need of surgery. Despite the introduction of highly effective biological drugs, treatment with azathioprine continues to be important even for early-onset IBD; however, in these patients azathioprine response seems to be reduced. This study evaluated azathioprine doses, metabolite concentrations, and their associations with patients' age in children with IBD treated at 6 tertiary pediatric referral centers.. Azathioprine doses, metabolites, and clinical effects were assessed after at least 3 months of therapy in 17 early-onset (age < 6 yr, cases) and 51 nonearly-onset (aged > 12 and <18 yrs, controls) patients with IBD. Azathioprine dose was titrated on therapeutic efficacy (response and adverse effects). Azathioprine metabolites and thiopurine methyltransferase activity were determined by high-performance liquid chromatography with ultra violet-vis detection (HPLC-UV) methods.. Frequency of patients in remission was similar among early-onset and control groups, respectively (82% and 84%, P value = 0.72). Early-onset patients required higher doses of azathioprine (median 2.7 versus 2.0 mg·kg·d, P value = 1.1 × 10). Different doses resulted in comparable azathioprine active thioguanine nucleotide metabolite concentrations (median 263 versus 366 pmol/8 × 10 erythrocytes, P value = 0.41) and methylmercaptopurine nucleotide concentrations (median 1455 versus 1532 pmol/8 × 10 erythrocytes, P value = 0.60). Lower ratios between thioguanine nucleotide metabolites and azathioprine doses were found in early-onset patients (median 98 versus 184 pmol/8 × 10 erythrocytes·mg·kg·d, P value = 0.017). Interestingly, early-onset patients presented also higher thiopurine methyltransferase activity (median 476 versus 350 nmol methylmercaptopurine/mg hemoglobin/h, P-value = 0.046).. This study demonstrated that patients with early-onset IBD present increased inactivating azathioprine metabolism, likely because of elevated activity of the enzyme thiopurine methyltransferase.

Topics: Adolescent; Age of Onset; Antimetabolites; Azathioprine; Case-Control Studies; Child; Child, Preschool; Chromatography, High Pressure Liquid; Dose-Response Relationship, Drug; Erythrocytes; Female; Guanine Nucleotides; Humans; Inflammatory Bowel Diseases; Male; Mercaptopurine; Methyltransferases; Thioguanine

The thiopurine drugs, 6-mercaptopurine and azathioprine, remain the mainstay of immunomodulator therapy for inflammatory bowel disease (IBD). Optimal management depends on achieving therapeutic levels of 6-thioguanine (6-TGN), but measuring thiopurine metabolites is associated with significant cost. Thiopurines cause lymphopenia and an increase in mean corpuscular volume (MCV). It is unclear whether any clinically useful correlation exists between 6-TGN levels and lymphocyte count or MCV.. The aim of this study is to investigate the correlation between 6-TGN levels and lymphocyte count and MCV in thiopurine-treated patients with IBD.. We analysed a prospectively acquired database of 67 patients with IBD treated with thiopurine therapy. The data were analysed looking at the relationship between 6-TGN levels and both lymphocyte count and MCV by using the Spearman's rank correlation coefficient.. Twenty-seven (40%) patients had therapeutic 6-TGN levels. Thirty-three (49%) patients had sub-therapeutic 6-TGN levels. A weak positive correlation between 6-TGN levels and lymphocyte count was demonstrated, but this was not statistically significant (Spearman's R = 0.14, P = 0.23). Spearman's rank correlation coefficient between 6-TGN levels and MCV was statistically significant (R = 0.42, P = 0.0005). MCV >101 fL excluded a subtherapeutic 6-TGN level with positive predictive value of 92%.. There is no specific lymphopenia that can be assumed to indicate a therapeutic 6-TGN level. The relationship between 6-TGN levels and MCV is likely to be clinically relevant. If MCV is elevated, 6-TGN is unlikely to be sub-therapeutic. MCV is a potential surrogate marker which can rule out sub-therapeutic thiopurine metabolites in patients with IBD treated with azathioprine or 6-mercaptopurine.

Topics: Adult; Azathioprine; Biomarkers; Erythrocyte Indices; Female; Humans; Immunosuppressive Agents; Inflammatory Bowel Diseases; Lymphopenia; Male; Mercaptopurine; Retrospective Studies; Thioguanine; Treatment Outcome

Conventional thiopurine [azathioprine and mercaptopurine] treatment during pregnancy in patients with inflammatory bowel disease [IBD] is considered to be safe; however data on the safety and teratogenicity of the non-conventional thiopurine tioguanine [TG] in pregnant IBD patients are lacking. We aim to describe the safety and teratogenicity of TG treatment during pregnancy in IBD patients.. This was a retrospective, multicentre descriptive case series of female IBD patients using TG during pregnancy. Data on disease and medication history, pregnancy complications, pregnancy outcome, mode of delivery, preterm birth, birthweight, congenital abnormalities, laboratory signs of myelosuppression or hepatotoxicity, and 6-thioguaninenucleotide [6-TGN] concentrations in mother and neonate were collected.. In all, 13 patients [77% Crohn's disease, 23% ulcerative colitis] used TG [median dose 18 g/day] during pregnancy; 19 pregnancies, including 1 twin pregnancy, were included. Spontaneous abortion occurred in three pregnancies. In 7 of the 16 ongoing pregnancies a caesarean section was performed. One neonate had a mild congenital abnormality [distal shaft hypospadias]. In the singleton pregnancies, the median birthweight was 3410 g at a median of gestational age of 39 weeks. No preterm birth [< 37 weeks] or low birthweight [< 2500 g] was observed in the singleton newborns. In the twin pregnancy an induction of labour was performed at 35 + 1 weeks of gestation because of pre-eclampsia. Both neonates had a low birthweight.. This relatively small case series supports safe use of TG in pregnant IBD patients. Still, consideration should be given to the indication and continuation of TG during pregnancy.

Topics: Adolescent; Antimetabolites, Antineoplastic; Birth Weight; Dose-Response Relationship, Drug; Female; Follow-Up Studies; Gestational Age; Humans; Infant, Newborn; Inflammatory Bowel Diseases; Male; Pregnancy; Pregnancy Complications; Pregnancy Outcome; Retrospective Studies; Thioguanine; Treatment Outcome; Young Adult

Thiopurine use in inflammatory bowel disease (IBD) is limited by drug toxicity and lack of therapeutic efficacy. We assessed the utility of thiopurine metabolite testing and the relationship between disease activity, dose, and metabolite levels in a real world setting.. Patients identified from pathology databases (2007-2012) at two tertiary IBD centers were included if they had thiopurines for at least four weeks. Demographics, dose, test indication, clinical status, action taken, and outcome were obtained by retrospective medical record review.. A total of 169 patients were included. 6-Thioguanine (TGN) levels were sub-therapeutic in 52%, therapeutic in 34%, and supratherapeutic in 14%. Test indication was active disease (79%), adverse effect (11%), or adherence assessment (7%). TGN trended lower in the active disease group compared to those with adverse effects (273 (+/- 23.2) versus 447 (+/- 117.7) pmol/8 × 10(8) RBC, P = 0.05). Weight-based dosing did not improve rates of therapeutic TGN levels (under-dosed 31.5% vs standard dose 35.4%), but was significantly associated with shunting toward 6-MMP (23.1% vs 6.8%, P = 0.008, OR = 4.1). Testing resulted in a change in patient treatment in 86% of patients with active disease and subtherapeutic levels and in 68% of tested patients overall.. Metabolite testing resulted in a change in management in most patients not responding to thiopurines or experiencing adverse events. Weight-based dosing did not increase rates of therapeutic levels but was associated with increased 6MMP shunting.

Topics: Azathioprine; Cohort Studies; Drug Monitoring; Humans; Inflammatory Bowel Diseases; Mercaptopurine; Retrospective Studies; Thioguanine; Treatment Outcome

Inflammatory bowel disease(IBD) is progressing rapidly in developing countries such as Iran. This research is intended to compile the frequency distribution of the drug metabolizing enzyme, thiopurine methyl transferase(TPMT) and the drug transporter, Multi drug resistance(MDR1) which are involved in metabolism of many therapeutics such as thiopurines in inflammatory bowel disease(IBD). Ethnicity is an important variable influencing drug response. The aims of this research were to investigate the association of TPMT phenotypes with MDR1 genotypes. TPMT activity was measured by using a non-extraction HPLC method and genotype for the C3435T polymorphism of MDR1 gene was determined in 215 unrelated IBD patients including of 85 males and 130 females and 212 unrelated healthy individuals consisted of 96 males and 116 females as control group by PCR-RFLP in Iran's western population. TPMT phenotypes demonstrated no frequency for deficient, 2.2% for low and 97.8% for normal activity that is different with results of other studies. Interestingly there were a significant negative correlation between TPMT activities as calculated based on nmol/grHb/h and positive correlation calculated in mU/L with Hb levels in IBD patients and control subjects. Dominant and codominant MDR1 C3435T gene polymorphism increased the risk of IBD by 1.45 and 1.46 times, respectively. IBD patients with MDR1 mutant genotypes C3435T, had lower TPMT activites and Hb concentrations. Using of mU/L is more appropriate than nmol6MTG/grHb/h for expressing TPMT activity. TPMT frequency of deficient and low activity in western Iran is low. The carriers of mutant C3435T MDR1 are not good TPMT methylators.

Topics: Adult; ATP Binding Cassette Transporter, Subfamily B; Body Mass Index; Case-Control Studies; Chromatography, High Pressure Liquid; Demography; Female; Humans; Inflammatory Bowel Diseases; Male; Methyltransferases; Odds Ratio; Pharmacogenetics; Phenotype; Polymorphism, Genetic; Risk Factors; Thioguanine

Nodular regenerative hyperplasia (NRH) of the liver is associated with inflammatory-mediated diseases and certain drugs. There is conflicting data on the prevalence of NRH and its clinical implications in inflammatory bowel disease (IBD) patients treated with thioguanine.. A retrospective cohort study involving 7 Dutch centers comprised all IBD patients who were being treated with thioguanine and underwent a liver biopsy as part of the standard toxicity screening. Liver biopsy specimens were reviewed by 2 experienced liver pathologists. Clinical data as well as liver chemistry, blood counts, and abdominal imaging were collected.. One hundred eleven IBD patients who submitted to liver biopsy were treated with thioguanine in a daily dose of 0.3 mg/kg for a median duration of 20 (4-64) months. NRH was detected in 6% of patients (7; 95% confidence interval, 3-14 patients). Older age (P = 0.02), elevated gamma-glutamyl transferase (P = 0.01) and alkaline phosphatase (P = 0.01) levels, a higher mean corpuscular volume (P = 0.02), and a lower platelet or leukocyte count (P < 0.01 and P = 0.02, respectively) were associated with NRH. Three of the 7 patients with NRH did not have any associated clinical symptoms or signs. The other 4 had minor biochemical abnormalities only. Ultrasonography revealed splenomegaly in 3 of the 78 patients (4%; 95% confidence interval, 0%-9%), only one of whom had NRH. There was no clinically overt portal hypertension.. The prevalence of NRH was 6% in liver biopsies obtained from IBD patients treated with thioguanine. Histopathological irregularities including NRH were not associated with clinically significant findings over the period of observation.

Topics: Adult; Aged; Antimetabolites, Antineoplastic; Chemical and Drug Induced Liver Injury; Female; Focal Nodular Hyperplasia; Humans; Inflammatory Bowel Diseases; Liver; Logistic Models; Male; Middle Aged; Multivariate Analysis; Netherlands; Retrospective Studies; Splenomegaly; Thioguanine; Ultrasonography; Young Adult

Thiopurines are extensively used immunosuppressants for the treatment of inflammatory bowel disease (IBD). The polymorphism of thiopurine S-methyltransferase (TPMT) influences thiopurine metabolism and therapy outcome. We used a TPMT knockdown (kd) model of human Jurkat T-lymphocytes cells to study the effects of treatment with 6-mercaptopurine (6-MP) and 6-thioguanine (6-TG) on proteome and phosphoproteome. We identified thirteen proteins with altered expression and nine proteins with altered phosphorylation signals. Three proteins (THIO, TXD17, and GSTM3) with putative functions in cellular oxidative stress responses were altered by 6-TG treatment and another protein PRDX3 was differentially phosphorylated in TPMT kd cells. Furthermore, reactive oxygen species (ROS) assay results were consistent with a significant induction of oxidative stress by both TPMT knockdown and thiopurine treatments. Immunoblot analyses showed treatment altered expression of key antioxidant enzymes (i.e., SOD2 and catalase) in both wt and kd groups, while SOD1 was downregulated by 6-TG treatment and TPMT knockdown. Collectively, increased oxidative stress might be a mechanism involved in thiopurine induced cytotoxicity and adverse effects (i.e., hepatotoxicity) and an antioxidant cotherapy might help to combat this. Results highlight the significance of oxidative stress in thiopurines' actions and could have important implications for the treatment of IBD patients.

Topics: Humans; Inflammatory Bowel Diseases; Jurkat Cells; Mercaptopurine; Methyltransferases; Oxidative Stress; Phosphorylation; Proteomics; T-Lymphocytes; Thioguanine

Thioguanine (TG) is a treatment for inflammatory bowel disease, but association with nodular regenerative hyperplasia has restricted its use. We conjectured that splitting a therapeutic daily dose of TG would be efficacious and should avoid liver toxicity.. We report on 62 patients with severe inflammatory bowel disease not responding to prednisolone, conventional thiopurines, biologics, or calcineurin inhibitors. Patients were prescribed oral split-daily TG to avoid individual doses >0.3 mg/kg. Data on concomitant medication, clinical efficacy measured by Harvey-Bradshaw Index for Crohn's, or Simple Clinical Colitis Score for ulcerative/indeterminate colitis (UC), and some paired endoscopies were available. Safety was followed clinically and with bloods at 2 centers. All patients at the U.K. center had a liver biopsy or magnetic resonance imaging after 6 months. Twenty-one patients had serial ultrasounds at the Australian center.. At 6 months, 19/21 of patients with Crohn's disease and 27/38 with ulcerative colitis had improved clinical activity. At study end, 53% of patients maintained improved clinical activity of steroids. Median duration of TG was 8 (0.3-45) months, median dose was 0.6 (0.3-1) mg/kg per day. Previous thiopurine-related adverse reactions were not encountered. Twenty-nine patients withdrew because of loss to follow-up, medical adverse events, or surgery. Possible early nodular regenerative hyperplasia was found on liver biopsy in 1 patient who was heterozygote deficient for thiopurine methyltransferase; the TG dose was lowered. TG was discontinued in a patient with nodular regenerative hyperplasia and concomitant antiphospholipid syndrome. There was 1 successful term pregnancy; cord blood and breast milk TG were low.. Split-dose TG seemed well tolerated and efficacious in this retrospective study of patients with difficult inflammatory bowel disease.

Topics: Adult; Aged; Antimetabolites, Antineoplastic; Chemical and Drug Induced Liver Injury; Cohort Studies; Dose-Response Relationship, Drug; Female; Follow-Up Studies; Humans; Hyperplasia; Inflammatory Bowel Diseases; Liver; Male; Middle Aged; Prognosis; Severity of Illness Index; Thioguanine; Young Adult

The thiopurines are widely used in the treatment of inflammatory bowel disease, but are limited by poor dose-effect relationship. The objective was to assess the ability of a novel assay, determining the mono-, di-, and triphosphates, of thioguanine as well as methylthioinosine as individual metabolites in erythrocytes, to predict clinical outcome compared to a routine assay, determining metabolites as sums.. Samples from 79 patients with Crohn's disease or ulcerative colitis treated with azathioprine or mercaptopurine were analysed by both assays. Clinical status was determined by the Harvey-Bradshaw and Walmsley indices. The genotypes of thiopurine methyltransferase (TPMT) and inosine triphosphatase were determined.. TPMT wild-type patients with thioguanine nucleotide (TGN) levels below the cut-off level were more likely to have active disease when TGN was measured by the novel assay (p=0.02), and when thioguanosine triphosphate (TGTP) was measured separately (p=0.01). When TGN was measured by the routine assay the correlation was not evident (p=0.12). Neither TGN levels nor TGTP correlated to disease activity in TPMT deficient patients. Patients with methyl thioinosine nucleotide (meTIN) levels above 1500 pmol/8×10^8 RBCs were more likely to have active disease (p=0.07). We observed good correlations between the mono-, di-, and triphosphates and their respective sums (R(2)>0.88).. The novel TGN assay was better in predicting clinical outcome compared to the routine assay, while determination of TGTP had no clinical advantage and TGTP ratio was not correlated to disease activity.

Topics: Adolescent; Adult; Aged; Azathioprine; Cross-Sectional Studies; Drug Monitoring; Erythrocytes; Female; GTP Phosphohydrolases; Guanine Nucleotides; Humans; Immunosuppressive Agents; Inflammatory Bowel Diseases; Male; Mercaptopurine; Methylthioinosine; Middle Aged; Thioguanine; Thioinosine; Thionucleotides; Young Adult

The drug-metabolizing enzyme thiopurine methyltransferase (TPMT) has become one of the best examples of pharmacogenomics to be translated into routine clinical practice. TPMT metabolizes the thiopurines 6-mercaptopurine, 6-thioguanine, and azathioprine, drugs that are widely used for treatment of acute leukemias, inflammatory bowel diseases, and other disorders of immune regulation. Since the discovery of genetic polymorphisms in the TPMT gene, many sequence variants that cause a decreased enzyme activity have been identified and characterized. Increasingly, to optimize dose, pretreatment determination of TPMT status before commencing thiopurine therapy is now routine in many countries. Novel TPMT sequence variants are currently numbered sequentially using PubMed as a source of information; however, this has caused some problems as exemplified by two instances in which authors' articles appeared on PubMed at the same time, resulting in the same allele numbers given to different polymorphisms. Hence, there is an urgent need to establish an order and consensus to the numbering of known and novel TPMT sequence variants. To address this problem, a TPMT nomenclature committee was formed in 2010, to define the nomenclature and numbering of novel variants for the TPMT gene. A website (http://www.imh.liu.se/tpmtalleles) serves as a platform for this work. Researchers are encouraged to submit novel TPMT alleles to the committee for designation and reservation of unique allele numbers. The committee has decided to renumber two alleles: nucleotide position 106 (G>A) from TPMT*24 to TPMT*30 and position 611 (T>C, rs79901429) from TPMT*28 to TPMT*31. Nomenclature for all other known alleles remains unchanged.

Topics: Alleles; Azathioprine; Genotype; Humans; Inflammatory Bowel Diseases; Mercaptopurine; Methyltransferases; Pharmacogenetics; Polymorphism, Genetic; Thioguanine

Few data on azathioprine (AZA) therapy for inflammatory bowel disease (IBD) exist for children. We evaluated whether the 6-thioguanine nucleotides (6-TGN) level predicts AZA refractoriness in children with IBD and whether children benefit an AZA dose escalation. Seventy-eight children with IBD initially treated with an AZA dose of 1.5-2.5 mg/kg/day were retrospectively included. The dose was adjusted based on the clinical status. The receiver operating characteristic curve and logistic regression were used to determine predictors for AZA resistance. Initially, 18 of 40 (45%) patients receiving a dose of <2 mg/kg/day and 11 of 38 (28.9%) patients receiving a dose of 2-2.5 mg/kg/day achieved remission. The 6-TGN level above 250 pmol/8.10(8) RBCs was associated with a higher remission rate, though non-significant. Among 35 patients with a dose escalation due to treatment failure, 12 (34.3%) achieved remission (the median 6-TGN level increased from 260 to 394 pmol/8.10(8) RBCs [P = .002]), 23 (67.6%) were AZA refractory. A 6-TGN level above 405 pmol/8.10(8) RBCs was the only predictor for AZA resistance (sensitivity 78.3%, specificity 75%, OR 10.8 [95% CI: 2.1-55.7, P = .004]). Serial metabolite monitoring is useful to identify children with IBD resistant to AZA. Children who cannot achieve remission despite a 6-TGN level above 405 pmol/8.10(8) RBCs should receive alternative therapies than dose increase.

Topics: Adolescent; Antimetabolites; Azathioprine; Child; Child, Preschool; Drug Resistance; Female; Humans; Inflammatory Bowel Diseases; Leukopenia; Male; Mercaptopurine; Thioguanine

The anti-leukemic drugs, azathioprine and 6-mercaptopurine (6MP), are important in the treatment of inflammatory bowel disease but an alternative faster-acting, less-allergenic thiopurine, 6-thioguanine (6TG), can cause hepatic veno-occlusive disease/sinusoidal obstructive syndrome (SOS). Understanding of SOS has been hindered by inability to ethically perform serial liver biopsies on patients and the lack of an animal model.. Normal and C57Bl/6 mice with specific genes altered to elucidate mechanisms responsible for 6TG-SOS, were gavaged daily for upto 28d with 6TG, 6MP or methylated metabolites. Animal survival was monitored and at sacrifice a histological score of SOS, haematology and liver biochemistry were measured.. Only 6TG caused SOS, which was dose related. 6TG and to a lesser extent 6MP but not methylated metabolites were associated with dose-dependent haematopoietic toxicity. SOS was not detected with non-lethal doses of 6TG. SOS did not occur in hypoxanthine-phosphoribosyl transferase-deficient C57Bl/6 mice, demonstrating that 6TG-SOS requires thioguanine nucleotides. Hepatic inflammation was characteristic of SOS, and C57Bl/6 mice deficient in P- and E-selectins on the surface of vascular endothelial cells showed markedly reduced SOS, demonstrating a major role for leukocytes recruited from blood. Split dosing of 6TG markedly attenuated SOS but still effected immunosuppression and prevented spontaneous colitis in Winnie mice, which have a single nucleotide polymorphism mutation in Muc2.. This novel model provides clinically relevant insights into how 6TG induces SOS, and how this dangerous adverse drug reaction may be avoided by either inhibition of endothelial activation or simple changes to dosing regimens of 6TG, while still being effective treatment for colitis.

Topics: Animals; Disease Models, Animal; Dose-Response Relationship, Drug; Hepatic Veno-Occlusive Disease; Inflammatory Bowel Diseases; Mice; Mice, Inbred C57BL; Statistics, Nonparametric; Survival Analysis; Thioguanine

A skewed thiopurine metabolism is a phenomenon associated with both poor treatment response and toxicity. Our aim was to evaluate the frequency of this phenomenon and the relationship to thiopurine methyltransferase (TPMT) function.. All thiopurine metabolite measurements in adult patients (n=4033) between January 2006 and April 2012 were assessed to evaluate the occurrence of a skewed metabolism and the relationship to TPMT genotype and activity.. A skewed metabolism was observed in 14% of all patients. It only developed in patients with a normal TPMT genotype, but was observed at all TPMT activity levels within the normal range (9.1-24.2 U/ml RBC). Two cases that illustrate typical clinical scenarios of a skewed metabolism and the effect of combination treatment with low-dose azathioprine and allopurinol are presented.. A skewed metabolism is a common clinical phenomenon in patients with a normal TPMT function, which can develop at all TPMT activity levels within the normal range. We suggest that metabolite measurements should be considered in patients not responding to treatment and in those with hepatotoxicity or myelotoxicity in order to detect a skewed metabolism, since this phenomenon can be successfully managed by a combination of low-dose azathioprine and allopurinol.

Topics: Adult; Allopurinol; Azathioprine; Chemical and Drug Induced Liver Injury; Dose-Response Relationship, Drug; Drug Resistance; Erythrocytes; Female; Free Radical Scavengers; Genotype; Humans; Immunosuppressive Agents; Inflammatory Bowel Diseases; Male; Methyltransferases; Middle Aged; Thioguanine

Although acute dextran sodium sulphate (DSS)-induced colitis in mice is frequently used as a preclinical model for testing drugs involved in inflammatory bowel disease (IBD), only limited data is available that compares the efficacy of established drug treatments and combinations employed in IBD. We have therefore compared the efficacy of aminosalicylates (mesalazine, olsalazine), corticosteroids (budesonide), thiopurines (6-thioguanine (6-TG)) and cyclosporine A (CsA) and combinations thereof as well as the EP4 agonist AGN205203 in the acute DSS-colitis model.. Female BALB/c mice were challenged with 4% DSS in drinking water for 7 days to induce colitis and treated daily with different drugs/combinations orally. Disease scores (diarrhoea, bleeding, disease activity index), systemic (body weight loss, serum amyloid A levels) and colonic (myeloperoxidase activity, length and histopathology) inflammation parameters were analysed.. Mesalazine, olsalazine (100mg/kg) and budesonide (0.5mg/kg) were only weakly active or even worsened colitis. 6-TG dose-dependently reduced systemic and colonic inflammation parameters with estimated ED50 values between 0.5-4 mg/kg. CsA (10, 25 and 50mg/kg) dose-dependently reduced colitis with high efficacy on systemic inflammation. A combination of CsA 25mg/kg+olsalazine 100mg/kg produced a more pronounced anti-inflammatory effect than the compounds given alone. AGN205203 (3, 10 and 30 mg/kg BID) was the most efficacious compound and almost completely inhibited colitis.. 6-TG and CsA are suitable reference compounds in the DSS mouse model. CsA+olsalazine, as a combination, was more efficacious than the compounds given alone, supporting combination treatments in IBD.

Topics: Aminosalicylic Acids; Animals; Anti-Inflammatory Agents; Budesonide; Colitis; Colon; Cyclosporine; Dextran Sulfate; Drug Therapy, Combination; Female; Gastrointestinal Agents; Humans; Inflammatory Bowel Diseases; Mesalamine; Mice; Mice, Inbred BALB C; Receptors, Prostaglandin E, EP4 Subtype; Thioguanine

Thiopurine drugs are widely used in the treatment of inflammatory bowel disease (IBD). The polymorphic enzyme thiopurine S-methyltransferase (TPMT) is of importance for thiopurine metabolism and adverse events occurrence. The role of other thiopurine-metabolizing enzymes is less well known. This study investigated the effects of TPMT and hypoxanthine guanine phosphoribosyltransferase (HPRT) activities on 6-thioguanine nucleotides (6-TGNs) concentrations and thiopurine-induced leukopenia in patients with IBD.. Clinical data and blood samples were collected from 120 IBD patients who were receiving azathioprine (AZA)/6-mercaptopurine (6-MP) therapy. Erythrocyte TPMT, HPRT activities and 6-TGNs concentrations were determined. HPRT activity and its correlation with TPMT activity, 6-TGNs level, and leukopenia were evaluated.. The HPRT activity of all patients ranged from 1.63-3.33 (2.31 ± 0.36) μmol/min per g Hb. HPRT activity was significantly higher in patients with leukopenia (27, 22.5%) than without (P < 0.001). A positive correlation between HPRT activity and 6-TGNs concentration was found in patients with leukopenia (r = 0.526, P = 0.005). Patients with HPRT activity > 2.70 μmol/min per g Hb could have an increased risk of developing leukopenia (odds ratio = 7.47, P < 0.001). No correlation was observed between TPMT activity and HPRT activity, 6-TGNs concentration, or leukopenia.. High levels of HPRT activity could be a predictor of leukopenia and unsafe 6-TGN concentrations in patients undergoing AZA/6-MP therapy. This could partly explain the therapeutic response or toxicity that could not be adequately explained by the polymorphisms of TPMT.

Topics: Adult; Aged; Erythrocytes; Female; Humans; Hypoxanthine Phosphoribosyltransferase; Inflammatory Bowel Diseases; Leukopenia; Male; Methyltransferases; Middle Aged; Polymorphism, Genetic; Prognosis; Thioguanine

High concentrations of methylated thiopurine metabolites, such as 6-methyl mercaptopurine, are associated with hepatotoxicity during administration of the conventional thiopurines azathioprine or 6-mercaptopurine in IBD patients. Metabolization of the non-conventional thiopurine 6-thioguanine does not generate 6-methyl mercaptopurine. Hence, the aim of our study was to evaluate hepatotoxicity during 6-thioguanine in IBD patients who previously failed conventional thiopurines due to 6-methyl mercaptopurine associated hepatotoxicity.. A retrospective single center intercept cohort study was performed of IBD patients using 6-thioguanine between January 2006 and July 2010 after failing conventional thiopurine therapy due to 6-methyl mercaptopurine associated hepatotoxicity. The primary outcome was the occurrence of 6-thioguanine induced hepatotoxicity, scaled according to the Common Terminology Criteria for Adverse Events.. Nineteen patients were included. Median duration of 6-thioguanine therapy (median daily dosage 21 mg (9-24)) was 23 weeks (6-96). Hepatotoxicity did not reoccur in 15 out of 19, whereas grade 1 toxicity persisted in 4 patients (p<0.001). Median aspartate aminotransferase and alanine aminotransferase concentrations decreased from 34 U/l (20-59) and 64 U/l (15-175) to 23 U/l (18-40; p=0.003) and 20 U/l (14-48; p=0.019), respectively.. Hepatotoxicity does not reoccur during 6-thioguanine treatment in most IBD patients who failed conventional thiopurines due to 6-methyl mercaptopurine associated hepatotoxicity. Hence, at least at short-term, 6-thioguanine appears a justifiable alternative thiopurine for these IBD patients.

Topics: Antimetabolites, Antineoplastic; Azathioprine; Chemical and Drug Induced Liver Injury; Female; Humans; Inflammatory Bowel Diseases; Male; Mercaptopurine; Retrospective Studies; Thioguanine; Treatment Outcome

Topics: Azathioprine; Humans; Immunosuppressive Agents; Inflammatory Bowel Diseases; Thioguanine

Topics: Azathioprine; Humans; Immunosuppressive Agents; Inflammatory Bowel Diseases; Thioguanine

Up to 20% of patients on thiopurine therapy fail to achieve adequate drug response. Many of these patients preferentially produce the toxic 6-methylmercaptopurine metabolites (6-MMP) rather than the active 6-thioguanine nucleotides (6-TGN) resulting in a high 6-MMP/6-TGN ratio (>20) and increased risk of hepatotoxicity.. To determine the prevalence of preferential 6-MMP producers and define the relationships between 6-TGN, 6-MMP and thiopurine methyltransferase (TPMT).. The database of 6-TGN, 6-MMP and TPMT measurements from patients throughout New Zealand was used to calculate patients' 6-MMP/6-TGN ratios and identify those with high (>20) or normal ratio (≤20).The TPMT enzyme activity was compared amongst the groups.. Of 1879 patients with TPMT, 6-TGN and 6-MMP results, 349 (19%) had a 6-MMP/6-TGN ratio >20. The mean TPMT enzyme activity was slightly lower for those with a 6-MMP/6-TGN ratio ≤20 vs. >20, which achieved statistical significance (12.2 vs. 13.2; P < 0.001). However, the distributions of TPMT enzyme activity were similar, with 97% of TPMT results falling between 5.0 and 17.6 IU/mL for both groups. In all, 17% of those with 6-MMP/6-TGN ratio ≤20 were intermediate TPMT metabolisers (TPMT 5.0-9.2 IU/mL) vs. 7% in those with a ratio >20.. In this patient population with measured 6-MMP/6-TGN ratios, 19% of patients were preferential 6-MMP producers. The results show that high TPMT enzyme activity is not the major reason for preferential 6-MMP production in most patients with a high metabolite ratio. This suggests that there are one or more important alternative mechanisms for preferentially producing 6-MMP.

Topics: Antimetabolites, Antineoplastic; Azathioprine; Chromatography, High Pressure Liquid; Drug Resistance; Erythrocyte Membrane; Female; Genotype; Guanine Nucleotides; Humans; Inflammatory Bowel Diseases; Male; Mercaptopurine; Methyltransferases; Statistics as Topic; Thioguanine; Thionucleotides

Infliximab-induced hepatotoxicity is reported in several case studies involving patients with inflammatory bowel disease (IBD) and a direct hepatotoxic effect has been proposed.. The aim of this study was to determine the direct in vitro toxicity of infliximab. As a proof of principle the in vitro toxicity of thiopurines and methotrexate was also determined.. Cell survival curves and the half maximal inhibitory concentrations (IC(50)) were obtained after 24, 48 and 72 h of incubation in HepG2 cells with the IBD drugs azathioprine, 6-mercaptopurine, 6-thioguanine, methotrexate or infliximab by using the WST-1 cytotoxicity assay.. No in vitro hepatotoxicity in HepG2 cells was seen with infliximab, while concentration-dependent cytotoxicity was observed when HepG2 cells were incubated with increasing concentrations of azathioprine, 6-mercaptopurine and 6-thioguanine.. Infliximab alone or given in combination with azathioprine showed no direct hepatotoxic effect in vitro, indicating that the postulated direct hepatotoxicity of infliximab is unlikely.

Topics: Analysis of Variance; Antibodies, Monoclonal; Azathioprine; Cell Survival; Dose-Response Relationship, Drug; Hep G2 Cells; Hepatoblastoma; Humans; In Vitro Techniques; Inflammatory Bowel Diseases; Infliximab; Liver Neoplasms; Mercaptopurine; Methotrexate; Sensitivity and Specificity; Thioguanine

Topics: Antimetabolites, Antineoplastic; Azathioprine; Female; Guanine Nucleotides; Humans; Inflammatory Bowel Diseases; Male; Mercaptopurine; Methyltransferases; Thioguanine; Thionucleotides

Circulating concentrations of 6-thioguanine nucleotide (6-TGN) and 6-methyl mercaptopurine (6-MMP) are associated with thiopurine efficacy and may predict toxicity. This study aimed to examine retrospectively the utility of measuring metabolite concentrations in patients with inflammatory bowel disease (IBD) who had continuing symptoms despite stable thiopurine treatment.. Concentrations of 6-TGN and 6-MMP were measured in lysates of washed red cells by high-performance liquid chromatography in peripheral blood drawn from 63 symptomatic patients with IBD (63% men, mean age 37, range 14-74 years, 67% Crohn's disease, 33% ulcerative colitis) treated with azathioprine or 6-mercaptopurine. Short-term clinical outcomes were examined.. 6-TGN concentrations weakly correlated with the thiopurine dose (r = 0.28, P = 0.08). On weight-based criteria, 50% of patients were underdosed. However, metabolite patterns suggested 7 (11%) patients were noncompliant, 18 (29%) were being underdosed, 33 (52%) were refractory to treatment with either appropriate (41%) or elevated (11%) metabolite concentrations, and 6 (10%) had a raised 6-MMP:6-TGN ratio consistent with aberrant thiopurine metabolism. The clinical outcome improved in 40 of 46 (87%) of patients in whom the course of action taken was as recommended by a metabolite-directed algorithm, while 3 of 17 patients (18%) improved where discordant actions were taken (P = 0.0001; Fisher's exact test). Fifteen patients (24%) avoided inappropriate escalation of therapy.. Dose-optimization or toxicity-avoidance strategies frequently result from metabolite testing in patients with inadequate efficacy from thiopurines, with evidence of better outcomes. Thiopurine metabolite testing is a potentially powerful tool for optimizing thiopurine usage in IBD.

Topics: Adolescent; Adult; Aged; Azathioprine; Chromatography, High Pressure Liquid; Colitis, Ulcerative; Crohn Disease; Female; Humans; Immunosuppressive Agents; Inflammatory Bowel Diseases; Male; Mercaptopurine; Middle Aged; Thioguanine; Treatment Failure; Young Adult

Topics: Colitis, Ulcerative; Crohn Disease; Evidence-Based Medicine; Gastrointestinal Agents; Humans; Inflammatory Bowel Diseases; Liver Cirrhosis; Thioguanine; Treatment Outcome

Although 6-mercaptopurine and azathioprine are effective treatments in inflammatory bowel disease (IBD), many patients discontinue treatment because of side effects. 6-Thioguanine (6-TG) may be an alternative rescue therapy in these intolerant patients but the pharmacokinetics of 6-TG are not fully described. Here we have measured the pharmacokinetics of the biotransformation of 6-TG into the pharmacologically active metabolites, 6-thioguanine nucleotides (6-TGN), in IBD patients.. In 12 patients with IBD, levels of 6-TGN and activities of thiopurine S-methyltransferase, xanthine oxidase and hypoxanthine guanine-phosphoribosyl-transferase were measured in a two-stage (i.v. and p.o. administration of 0.3 mg·kg(-1) 6-TG), prospective study. Median exposure of 6-TGN in red blood cells (RBC) was expressed as the ratio of the area under the curve (AUC) per mg 6-TG after i.v. dosing and that after p.o. dosing.. The median AUC per mg 6-TG was 1068 (p.o.) and 7184 (i.v.) pmol·h (8 × 10(8) RBC)(-1) . Median exposure of 6-TGN in RBC was 15% (9-28). Hypoxanthine guanine-phosphoribosyl-transferase activity correlated with peak 6-TGN and with AUC per mg (r= 0.7, P= 0.02 and r= 0.6, P= 0.03 respectively). Thiopurine S-methyltransferase activity was inversely related to AUC per mg (r=-0.8, P= 0.001), whereas that of xanthine oxidase was correlated with a lower peak 6-TGN (r=-0.7, P= 0.02).. The great variability of the AUC per mg for 6-TG observed after p.o. and i.v. administration of 6-TG, was partly explained by variability in activities of metabolizing enzymes. Exposure of 6-TGN was low in all patients.

Topics: Administration, Oral; Adult; Female; Guanine Nucleotides; Humans; Hypoxanthine Phosphoribosyltransferase; Inflammatory Bowel Diseases; Infusions, Intravenous; Male; Methyltransferases; Middle Aged; Prospective Studies; Thioguanine; Thionucleotides; Xanthine Oxidase; Young Adult

To perform a survey of thiopurine treatment in inflammatory bowel disease (IBD) among Swedish gastroenterologists.. A web-based questionnaire consisting of 25 multiple-choice questions was sent to 322 gastroenterologists in adult practice.. A total of 132 questionnaires were received giving a response rate of 41%. Thiopurines were used by all 122 gastroenterologists in IBD practice and azathioprine was the first-choice thiopurine among 118 (97%) of them. Almost all gastroenterologists (97%) used weight-based dosing that was gradually escalated. The vast majority (89%) considered that efficacy should be evaluated within 6 months of therapy, while opinions regarding the optimal duration of therapy varied considerably. It was seen that 74% switched thiopurine in case of intolerance to the first-line substance. Thiopurine S-methyltransferase (TPMT) determinations were performed by 74% of the gastroenterologists and 67% used metabolite measurements. TPMT analyzers were more likely to measure metabolites (74 vs. 43%, p = 0.002). A quarter of the respondents were familiar with unconventional immunomodulation (co-administration of allopurinol, 6-thioguanine, mycophenolate mofetil or tacrolimus) and these respondents were also more likely to measure metabolites (79 vs. 52%; p = 0.002).. Thiopurines are well established in the treatment of IBD among Swedish gastroenterologists. New and evolving knowledge about thiopurine therapy in IBD has been adapted to a large extent. Whether this change in clinical practice will have an impact on treatment outcomes has yet to be proven.

Topics: Allopurinol; Antibodies, Monoclonal; Antimetabolites; Azathioprine; Drug Therapy, Combination; Female; Gastroenterology; Humans; Immunosuppressive Agents; Inflammatory Bowel Diseases; Male; Methyltransferases; Mycophenolic Acid; Practice Patterns, Physicians'; Surveys and Questionnaires; Sweden; Tacrolimus; Thioguanine; Tumor Necrosis Factor-alpha

This study compared youth and parent-proxy reports of health-related quality of life (HRQoL) among youth with inflammatory bowel disease (IBD) to published comparison group data and examined concordance between youth and parent-proxy reports of HRQoL.. One hundred thirty-six youth and parent-proxy reports on the PedsQL 4.0 Generic Core Scales were compared to published data from chronically ill, acutely ill, and healthy comparison groups using independent samples t-tests. Reporter agreement was examined using paired samples t-tests and intraclass correlations (ICCs).. Youth with IBD reported lower psychosocial functioning than the healthy comparison group, higher physical and social functioning than the chronically ill group, and lower school functioning than all published comparison groups. Parent-proxy reports of youth HRQoL were higher than the chronically ill group, but lower than the healthy group on all scales except psychosocial functioning. Youth with active IBD reported lower physical health domain scores than youth with inactive disease. Concordance between youth and parent-proxy reports was moderate, with the lowest agreement in school and social functioning.. Youth with IBD and their parents rate HRQoL as lower than healthy youth but do not perceive the impact of IBD to be as limiting as in other chronic conditions. Youth report suggests that IBD may be particularly detrimental to HRQoL in the school functioning domain. Moderate agreement between parent and youth reports substantiates continued use of multiple informants in studies of pediatric HRQoL.

Topics: Adolescent; Adult; Child; Female; Humans; Inflammatory Bowel Diseases; Interpersonal Relations; Male; Mercaptopurine; Mesalamine; Methylthioinosine; Middle Aged; Parents; Quality of Life; Self Concept; Severity of Illness Index; Sickness Impact Profile; Social Adjustment; Thioguanine

The monitoring of 6-thioguanine nucleotides (6-TGN) levels is warranted during thiopurine therapy for patients with inflammatory bowel diseases.. The aim of this study was to elucidate the parameters that can predict the 6-TGN levels among Japanese patients with inflammatory bowel diseases undergoing thiopurine therapy.. The 6-TGN levels were measured in 54 patients with inflammatory bowel diseases (32 with ulcerative colitis and 22 with Crohn's disease), who had been administered azathioprine or 6-mercaptopurine for more than 90 days. Possible correlations between the hematologic parameters and 6-TGN levels were investigated. The clinical and hematologic variables were evaluated to determine the 6-TGN levels of less than or over 235 pmol/8 x 10(8) RBCs.. The 6-TGN levels correlated significantly with changes in the mean corpuscular volume (R = 0.423, p = 0.001) and the lymphocyte counts (R = -0.280, p = 0.04). A multivariate analysis revealed changes in the mean corpuscular volume (OR: 1.22, 95% CI: 1.07-1.40) and hemoglobin levels (OR: 0.59, 95% CI: 0.35-0.99) to be factors predictive of the 6-TGN levels. An increase in the mean corpuscular volume of 3.5 fl was determined to be the most preferable cut-off value to distinguish patients with 6-TGN >or= 235 pmol/8 x 10(8) RBCs from those with a lower concentration.. Changes in the mean corpuscular volume are considered to be predictive of the 6-TGN levels in patients with inflammatory bowel diseases receiving thiopurine therapy.

Topics: Adult; Azathioprine; Biomarkers, Pharmacological; Chi-Square Distribution; Erythrocyte Volume; Female; Humans; Inflammatory Bowel Diseases; Japan; Logistic Models; Male; Mercaptopurine; Nucleotides; Predictive Value of Tests; Retrospective Studies; Statistics, Nonparametric; Thioguanine

Portal hypertension (PH) is a complication that may occur in patients with inflammatory bowel disease (IBD). In these patients, the etiology of PH may not be alcoholic or viral cirrhosis (which cause 90% of cases in the general population). Consequently, etiologic study of PH in patients with IBD should always include a wide spectrum of possibilities. Moreover, the development of PH in IBD patients often requires a distinct therapeutic approach to IBD (both medical and surgical) as PH may be a contraindication for some drugs and is a risk factor for surgical morbidity and mortality. We present the cases of two patients with IBD who developed PH and review the most likely causes of PH in IBD, as well as preventive and therapeutic strategies.

Topics: Adult; Anti-Inflammatory Agents, Non-Steroidal; Arthritis, Juvenile; Ascites; Crohn Disease; Female; Humans; Hypertension, Portal; Immunosuppressive Agents; Inflammatory Bowel Diseases; Intestinal Pseudo-Obstruction; Liver Cirrhosis; Mesalamine; Mesenteric Veins; Methotrexate; Splenomegaly; Thioguanine; Thrombophilia; Varicose Veins

Monitoring of thiopurine metabolites 6-thioguanine nucleotides (6-TGN) and 6-methylmercaptopurine (6-MMP) is used to assess compliance and explain adverse reactions in IBD-patients. Correlations between dosage, metabolite concentrations and therapeutic efficacy or toxicity are contradictive. Research is complicated by analytical problems as matrices analyzed and analytical procedures vary widely. Moreover, stability of thiopurine metabolites is not well documented, yet pivotal for interpretation of analytical outcomes. Therefore, we prospectively investigated metabolite stability in blood samples under standard storage conditions.. Stability at room temperature and refrigeration (22 degrees C, 4 degrees C) was investigated during 1 week and frozen samples (-20 degrees C, -80 degrees C) were analyzed during 6 months storage. Ten patient samples were analyzed for each study period.. Median 6-TGN concentrations on day 7 decreased significantly to 53% and 90% during storage at ambient temperature or refrigeration. Median 6-MMP concentrations on day 7 decreased significantly to 55% and 86%, respectively. Samples stored at -20 degrees C also showed significant decreases in both 6-TGN and 6-MMP in comparison with baseline values. At -80 degrees C, only 6-MMP showed a significant decrease in values compared to baseline.. The stability of thiopurine metabolites is clearly a limiting factor in studies investigating utilisation of TDM and correlations with therapeutic outcome in IBD-patients. This has to be accounted for in clinical practice and (multi-center) trials investigating thiopurine drugs.

Topics: Chromatography, High Pressure Liquid; Drug Stability; Humans; Inflammatory Bowel Diseases; Mercaptopurine; Reproducibility of Results; Specimen Handling; Statistics, Nonparametric; Thioguanine

Monitoring of thiopurine metabolites is important due to a complex metabolism with large interindividual variation, but the suitability of currently used methods has been questioned. The drawbacks include poor reproducibility, the inability to differentiate between the different analytes, as well as the use of a nontarget matrix. Further research should be directed toward measuring thiopurine metabolites in mononuclear cells, measuring the different nucleotides specifically, as well as measuring the incorporation of thioguanine into DNA. The studies should not be limited to thioguanosine nucleotides but include methylthioinosine nucleotides as well.

Topics: Humans; Immunosuppressive Agents; Inflammatory Bowel Diseases; Mercaptopurine; Purines; Thioguanine

Individualised doses of azathioprine (AZA) may be prescribed by monitoring the levels of the enzyme thiopurine methyltransferase (TPMT). The measurements of thiopurine metabolites of AZA, 6-thioguanine (6-TGN) and 6-methylmercaptopurine (6-MMP), have also been reported as new markers of AZA activity.. To describe TPMT phenotype in our population and to establish a relationship between thiopurine metabolites,and therapeutic activity and adverse effects.. Data on TPMT were retrospectively collected from 107 patients, and 6-TGN and 6-MMP levels in 18 patients currently on treatment with AZA (Crohn's disease 5, ulcerative colitis 5, autoimmune hepatitis 5).. Mean value of TPMT was 20.19U/ml. None of the patients had a TPMT activity<5U/ml. Of the 18 patients on treatment, 13 showed sub-therapeutic levels of 6-TGN (<235pmol/8x10(8) red blood cells). Clinical remission was maintained in 45% of patients. Mean levels of 6-TGN in patients with clinical remission were 259pmol/8x10(8) red blood cells versus 209pmol/8x10(8) red blood cells in non-responders (p=0.37). There was an inverse relationship (r=-0.28) between TPMT and 6-TGN levels. Toxic effects occurred in 6 of 18 patients, with leukopenia in 5 and hyperamylasemia in 1.. Determination of TPMT and monitoring of thiopurine metabolites allows AZA treatment to be optimised, although further studies are necessary to establish therapeutic effectiveness and toxicity ranges.

Topics: Adolescent; Azathioprine; Female; Hepatitis, Autoimmune; Humans; Immunosuppressive Agents; Inflammatory Bowel Diseases; Male; Mercaptopurine; Methyltransferases; Retrospective Studies; Thioguanine

Topics: Administration, Oral; Azathioprine; Biomarkers, Pharmacological; Drug Monitoring; Erythrocyte Count; Humans; Immunosuppressive Agents; Inflammatory Bowel Diseases; Japan; Leukocyte Count; Mercaptopurine; Methyltransferases; Mutation; Remission Induction; Thioguanine; Treatment Outcome

6-Thioguanine is used in inflammatory bowel disease since 2001, with promising short-term results. In 2003, liver histology of some 6-thioguanine treated patients showed nodular regenerative hyperplasia. Recently, magnetic resonance imaging revealed nodular regenerative hyperplasia in patients with normal histology.. Investigating the presence of nodular regenerative hyperplasia in long-term 6-thioguanine treated patients.. Inflammatory bowel disease patients, using 6-thioguanine minimally 24 months, were asked to undergo liver biopsy and magnetic resonance imaging.. Fourteen patients used 6-thioguanine minimally 24 months, 13 participated. Mean 6-thioguanine therapy duration, daily dose and 6-thioguanine nucleotide levels were: 36 months, 18.8 mg (0.28 mg/kg) and 705 pmol/8x10(8) erythrocytes, respectively. Liver histology and magnetic resonance imaging showed no nodular regenerative hyperplasia.. Liver biopsy and magnetic resonance imaging showed no nodular regenerative hyperplasia in these long-term 6-thioguanine treated inflammatory bowel disease patients. 6-thioguanine dose and metabolite levels were lower compared with previous nodular regenerative hyperplasia reports, suggesting dose or metabolite level-dependent effects. Otherwise, nodular regenerative hyperplasia is related with inflammatory bowel disease itself and immunosuppressives, including azathioprine and 6-mercaptopurine.. 6-Thioguanine is debated due to nodular regenerative hyperplasia. We found no nodular regenerative hyperplasia in inflammatory bowel disease patients with long-term, low dosed 6-thioguanine, suggesting metabolite level-dependent effects. Therefore, 6-thioguanine still seems useful, but in selected patients, intolerant for other immunosuppressives, low dosed and under close surveillance of metabolite levels and hepatotoxity.

Topics: Adult; Biopsy; Chemical and Drug Induced Liver Injury; Cohort Studies; Female; Humans; Hyperplasia; Inflammatory Bowel Diseases; Liver; Magnetic Resonance Imaging; Male; Middle Aged; Thioguanine

6-Thioguanine nucleotides (6-TGN) are active metabolites of azathioprine (AZA) and 6-mercaptopurine (6MP). Higher remission rates have been observed in patients with higher 6-TGN levels. However, many physicians prescribe AZA/6MP using milligrams per kilogram (mg/kg) dosing regimens without measuring 6-TGN levels. The aim of this study was to examine the association between 6MP dose and 6-TGN levels.. We conducted a cross-sectional study of patients treated for inflammatory bowel disease (IBD) with AZA or 6MP, whose 6-TGN levels were measured. Patients with low or intermediate thiopurine methyl transferase (TPMT) activity were excluded. AZA dose was converted to 6MP equivalents. The relationship between dose and 6-TGN levels was assessed with the Spearman correlation coefficient. We used logistic regression to assess the relationship between dose and 6-TGN levels of >230 pmol/8 x 10(8).. In this study, 155 patients met our inclusion criteria (median dose, 1.01 +/- 0.40; range, 0.61-1.41 mg/kg). There was a weak correlation between 6-TGN levels and the absolute dose (rho = 0.18, P = 0.04) and the dose in mg/kg (rho = 0.19, P = 0.03). The correlation between mg/kg dosage and 6-TGN levels was slightly stronger in those using concomitant 5-aminosalicylate (5-ASA) medications (rho = 0.24, P = 0.02). Compared with <1.0 mg/kg per day, doses of > or =1.5 mg/kg per day were strongly associated with 6-TGN levels of >230 pmol/8 x 10(8) RBC (adjusted odds ratio [OR] = 3.7, 95% confidence interval [CI] = 1.1-11.8). However, only 37% of patients receiving > or =1.0 mg/kg per day had 6-TGN levels of >230 pmol/8 x 10(8) RBC.. 6MP dose is weakly associated with 6-TGN levels. The use of standard mg/kg dosing regimens will result in low 6-TGN levels in most patients.

Topics: Adult; Biological Availability; Cross-Sectional Studies; Dose-Response Relationship, Drug; Female; Humans; Immunosuppressive Agents; Inflammatory Bowel Diseases; Male; Mercaptopurine; Thioguanine

The aim of this study was to evaluate the diagnostic value of different magnetic resonance (MR) techniques for the diagnosis of nodular regenerative hyperplasia (NRH). Thirty-one patients with inflammatory bowel disease, who received 6-thioguanin, underwent liver biopsy and liver MRI on a 1.5-T MR system, with gadolinium and superparamagnetic iron oxide particles (SPIO). MR imaging (MRI) was evaluated independently as well as in consensus by two blinded readers, who received the following image sets: pre-contrast; pre-contrast and gadolinium-enhanced; pre-contrast and SPIO-enhanced and all images. The results were correlated with histopathology and diagnostic efficacy parameters were calculated. NRH was found in 13/31 patients. The set "all images" showed the highest sensitivity (84.6%), accuracy (77.4%) and negative predictive value (86.7%). However, results for gadolinium were only slightly inferior. The highest specificity (76.5%) was found for SPIO. The A(z) values of both readers were highest for gadolinium (mean A(z) = 0.824). It can be concluded that gadolinium-enhanced and SPIO-enhanced MRI enable an accurate diagnosis of NRH. Since gadolinium-enhanced MRI is very sensitive, it should be used for screening high-risk patients. SPIO-enhanced MRI is less sensitive, but more specific. The combination of both guarantees a high sensitivity and specificity and, therefore, is the diagnostic procedure of choice.

Topics: Adult; Biopsy, Needle; Contrast Media; Dextrans; Female; Ferrosoferric Oxide; Focal Nodular Hyperplasia; Gadolinium DTPA; Humans; Image Enhancement; Image Processing, Computer-Assisted; Inflammatory Bowel Diseases; Iron; Liver; Liver Regeneration; Magnetic Resonance Imaging; Magnetite Nanoparticles; Male; Meglumine; Middle Aged; Organometallic Compounds; Oxides; Thioguanine

Many IBD patients not responding to azathioprine (AZA) or 6-mercaptopurine (6-MP) preferentially metabolize 6-MP to 6-methylmercaptopurine (6-MMP). We describe the use of allopurinol in AZA/6-MP nonresponders to deliberately shunt metabolism of 6-MP toward 6-thioguanine (6-TGN) and improve clinical responses.. Twenty outpatients who were AZA/6-MP nonresponders and had high 6-MMP metabolite levels were included. Subjects were commenced on allopurinol 100 mg daily, and the dose of 6-MP/AZA was reduced to 25%-50% of the original dose.. After allopurinol was started, mean 6-TGN levels increased from 191.3 (+/- standard error of the mean) +/- 17.1 to 400.3 +/- 36.9 pmol/8 x 10(8) red blood cells (P < .001), whereas mean 6-MMP levels decreased from 10,604.7 +/- 1278.2 to 2000.6 +/- 437.1 pmol/8 x 10(8) red blood cells (P < .001). The addition of allopurinol led to a reduction in the mean partial Harvey Bradshaw Index in Crohn's disease patients from 4.9 +/- 1.0 to 1.5 +/- 0.3 points (P = .001), and in ulcerative colitis patients mean Mayo Scores decreased from 4.1 +/- 0.7 to 2.9 +/- 0.7 points (P = .13). The addition of allopurinol enabled a reduction in mean daily prednisone dosage from 17.6 +/- 3.9 to 1.8 +/- 0.7 mg (P < .001) and led to normalization of transaminase levels, with mean AST levels reducing from 42.5 +/- 8.1 to 23.5 +/- 1.6 IU (P = .12) and mean ALT levels reducing from 101.6 +/- 26.9 to 33.9 +/- 5.2 IU (P = .01).. The addition of allopurinol to thiopurine nonresponders with high 6-MMP metabolite levels is an effective and safe means of optimizing 6-TGN production, leading to improved disease activity scores, reduced corticosteroid requirements, and normalization of liver enzymes.

Topics: Allopurinol; Azathioprine; Drug Synergism; Humans; Immunosuppressive Agents; Inflammatory Bowel Diseases; Mercaptopurine; Thioguanine; Treatment Outcome

6-Thioguanine has been used as an alternative immunomodulator in the treatment of inflammatory bowel disease but data on its efficacy and safety are limited. The aim of this study was to analyse our experience of the efficacy and safety of 6-thioguanine in inflammatory bowel disease.. Patients attending the inflammatory bowel disease clinic who were started on 6-thioguanine therapy were included in this prospective observational study. Indications for initiating 6-thioguanine therapy and other related clinical, pharmacological and laboratory parameters prior to and during therapy were recorded to determine the efficacy and safety of 6-thioguanine.. A total of 40 patients were treated with 6-thioguanine, 28 with Crohn's disease, 10 with ulcerative colitis and 2 with indeterminate colitis, at a fixed daily dose of 40 mg and continued for a median duration of 34 weeks (range 2-90 weeks). The indications for 6-thioguanine therapy included previous clinical resistance to thiopurine analogues (n=21), intolerance to thiopurine analogues (n=8) and de novo 6-thioguanine use in steroid refractory disease (n=11). Disease remission was reached in 44%, 73% and 89% of these patient groups at 3, 6 and 12 months, respectively. Inflammatory markers and steroid use were significantly lower during 6-thioguanine therapy compared with in the period before therapy. Therapy was discontinued in 13 patients (33%), mainly because of thrombocytopenia and associated hepatotoxicity.. 6-Thioguanine is a useful addition to treatment in inflammatory bowel disease but the frequent occurrence of hepatotoxicity limits its routine use.

Topics: Adolescent; Adult; Aged; Antimetabolites, Antineoplastic; Dose-Response Relationship, Drug; Female; Follow-Up Studies; Humans; Inflammatory Bowel Diseases; Male; Middle Aged; Prospective Studies; Remission Induction; Thioguanine; Treatment Outcome

Measurement of thiopurine metabolite levels may be useful as a clinical tool to optimize thiopurine treatment of paediatric inflammatory bowel disease (IBD).. The authors evaluated correlations between 6-thioguanine nucleotide (6-TGN) and therapeutic response, metabolite levels and drug toxicity.. Fifty-six paediatric IBD patients treated with thiopurines had 326 metabolite level measurements and were retrospectively reviewed. Clinical status and laboratory parameters were compared with metabolite levels.. There was significant correlation between 6-TGN levels and therapeutic response, with higher median 6-TGN levels among patients with therapeutic response than those with non-therapeutic response (194 vs. 146 pmol/8 x 10(8) RBC; P = 0.0004). Patients with 6-TGN levels >235 pmol/8 x 10(8) RBC were more likely to achieve therapeutic response than those below the cut-off (odds ratio, 2.5; 95% CI, 1.5-4.1). Patients who developed leukopenia tended to have higher median 6-TGN levels than those without leukopenia (261 vs. 160 pmol/8 x 10(8) RBC) but the difference was not statistically significant. There was no correlation between 6-methylmercaptopurine levels and hepatotoxicity. Two patients developed acute pancreatitis. Metabolite level measurements were helpful in identifying non-compliance in nine patients.. Monitoring of thiopurine metabolite levels is useful to guide and optimize dosing, as an adjunct to clinical judgement, blood count and liver biochemistry measurements to minimize the risk of drug toxicity and to confirm non-compliance.

Topics: Adolescent; Azathioprine; Chemical and Drug Induced Liver Injury; Child; Child, Preschool; Drug Hypersensitivity; Female; Humans; Immunosuppressive Agents; Infant; Inflammatory Bowel Diseases; Leukopenia; Male; Mercaptopurine; Pancreatitis; Retrospective Studies; Thioguanine; Thrombocytopenia; Treatment Refusal

Recent studies suggest an association between 6-thioguanine (6-TG) therapy and hepatic nodular regenerative hyperplasia (NRH) in patients with inflammatory bowel disease (IBD). An influence of 6-TG on portal pressure remains to be determined. The aim of the study was to examine the functional relevance of long-term 6-TG treatment on hepatic hemodynamics in IBD patients and its association with NRH.. Patients treated with 6-TG for IBD underwent measurement of the hepatic venous pressure gradient (HVPG) and liver biopsy. 6-TG therapy was stopped when NRH was diagnosed. If elevated, HVPG measurement was repeated after 1 yr.. Twenty-six patients (15 women, 11 men; median age 41 yr, range 23-76) treated with 6-TG for 38 months (median; range 12-45) were included. Among 24 patients with sufficient liver biopsy, 6 patients (25%) were diagnosed with NRH. In these 6 patients, the HVPG was higher (median HVPG 7 mmHg, range 3-14) than in the 18 patients without NRH (median 3 mmHg, range 2-5; P < 0.001). In the patients with NRH, two had clinically significant portal hypertension (CSPH) (13 and 14 mmHg, respectively); in one patient the HVPG was slightly elevated (7 mmHg). No overt clinical signs of portal hypertension were observed. One year after stopping 6-TG therapy, HVPG decreased in all 3 patients with initially elevated HVPG levels.. We demonstrate that IBD patients under long-term 6-TG therapy are at a substantial risk for developing NRH. NRH results in elevation of HVPG and may cause CSPH. Discontinuation of 6-TG therapy extenuates portal hypertension and may thus reduce the risk of complications.

Topics: Adult; Aged; Antimetabolites, Antineoplastic; Biopsy; Female; Focal Nodular Hyperplasia; Humans; Hypertension, Portal; Inflammatory Bowel Diseases; Male; Middle Aged; Statistics, Nonparametric; Thioguanine

Drug-induced liver injury was recently reported as a major complication leading to hepatic nodular regenerative hyperplasia (NRH) in patients with inflammatory bowel disease (IBD) and 6-thioguanine (6-TG) therapy. The aim of the study was to evaluate the prevalence of 6-TG-related hepatotoxicity in a large multi-centered IBD population by means of a systematic online survey.. Clinical and laboratory data, imaging techniques (sonography, CT, MRI) and histology of liver biopsies were surveyed in IBD patients treated with 6-TG. The decision on whether liver imaging and/or liver biopsy were performed was exclusively at the discretion of the investigator.. 6-TG use was fully documented in 296 patients (median treatment duration 56 weeks, range < 1-207). Laboratory signs of drug-induced liver injury were found in 43 patients (14.5%). Liver imaging revealed pathologic results in 68/176 patients (38.6%). Liver biopsy was performed in a subset of 60 patients; using silver-reticulin staining (n = 59), NRH was considered in 16 patients (27.1%). Age was the only independent, albeit weak, risk factor for development of NRH.. This large online survey confirms the strong association between 6-TG treatment and the significant risk of development of NRH in patients with IBD. The definitive diagnosis of NRH depends solely upon liver biopsy.

Topics: Adolescent; Adult; Aged; Aged, 80 and over; Biopsy; Child; Data Collection; Data Interpretation, Statistical; Female; Focal Nodular Hyperplasia; Humans; Inflammatory Bowel Diseases; Internet; Liver; Magnetic Resonance Imaging; Male; Middle Aged; Risk Factors; Smoking; Surveys and Questionnaires; Thioguanine; Treatment Outcome; Ultrasonography

Topics: Azathioprine; Biopsy; Chemical and Drug Induced Liver Injury; Dose-Response Relationship, Drug; Drug Tolerance; Humans; Immunosuppressive Agents; Inflammatory Bowel Diseases; Liver; Liver Diseases; Mercaptopurine; Thioguanine

Topics: Antimetabolites; Azathioprine; Drug Monitoring; Genotype; Humans; Inflammatory Bowel Diseases; Methyltransferases; Pyrophosphatases; Thioguanine

Small uncontrolled trials have suggested that 5-aminosalicylate (5-ASA) medications increase 6-thioguanine nucleotide (6-TGn) levels in adults with Crohn's disease (CD) on azathioprine (AZA) or 6-mercaptopurine (6-MP), presumably through the inhibition of thiopurine methyltransferase (TPMT). We tested the theory that coadministration of 5-ASA agents with AZA/6-MP results in higher 6-TGn levels in a large cohort of children and adults with CD or ulcerative colitis (UC).. A retrospective cohort study identified all children and adults treated for IBD with AZA/6-MP at 2 tertiary medical centers. Patients were included if their TPMT genotype was known and 6-TGn and 6-methymercaptopurine (6-MMP) levels had been obtained after 3 months of clinical remission at a stable dose of AZA/6-MP. 6-TGn and 6-MMP levels were compared between patients taking and those not taking 5-ASA medications through the use of linear regression models to identify and adjust for potentially confounding variables.. Of the 126 patients included, 88 were taking 5-ASA medications. Patients on 5-ASA agents had higher mean 6-TGn levels after adjustment for confounding variables (Delta6-TGn, 47.6 +/- 21.8 pmol/8 x 10 red blood cells; P = 0.03). CD and TPMT heterozygosity was independently associated with higher 6-TGn levels (P = 0.01 and P = 0.03, respectively). 5-ASA exposure was not associated with a change in 6-MMP levels.. We found that 5-ASA therapy is associated with higher 6-TGn levels in children and adults with IBD on 6-MP/AZA. TPMT inhibition may not explain this effect because 5-ASA exposure did not affect 6-MMP levels. The observed association of CD with higher 6-TGn levels is novel and needs to be verified in prospective studies.

Topics: Adolescent; Adult; Aged; Anti-Inflammatory Agents, Non-Steroidal; Azathioprine; Biomarkers; Child; Cross-Sectional Studies; Female; Follow-Up Studies; Humans; Immunosuppressive Agents; Inflammatory Bowel Diseases; Male; Mercaptopurine; Mesalamine; Middle Aged; Remission Induction; Retrospective Studies; Severity of Illness Index; Thioguanine; Treatment Outcome

Although 6-thioguanine (6-TG) has been suggested as an effective treatment option for patients with inflammatory bowel disease (IBD), the recent description of its hepatotoxicity has led to the recommendation not to consider this drug. We initiated a multicenter safety study in IBD-patients treated with 6-TG to investigate hepatic changes by liver biopsy and magnetic resonance imaging (MRI).. Forty-five patients from three European centers treated with 6-TG (40-80 mg/d) at least for 8 weeks were enrolled. In all patients liver biopsy and MRI were performed. Slides and MR images were independently read by two pathologists and radiologists, respectively, and interpreted according to predefined criteria by consent.. In 8 patients nodular regenerative hyperplasia (NRH) was diagnosed by liver biopsy, in 8 additional patients NRH could not be excluded due to equivocal pathological findings. MRI demonstrated a sensitivity of 77% and a specificity of 72% in the detection of pathohistological findings consistent with and/or possibly related to NRH.. Our study suggests that 6-TG therapy in IBD patients is associated with NRH of the liver. Based on a special MRI protocol, non-invasive diagnosis of NRH with promising sensitivity and specificity was demonstrated.

Topics: Adult; Aged; Antimetabolites, Antineoplastic; Biopsy; Chemical and Drug Induced Liver Injury, Chronic; Diagnosis, Differential; Female; Follow-Up Studies; Humans; Hyperplasia; Inflammatory Bowel Diseases; Liver; Magnetic Resonance Imaging; Male; Middle Aged; Reproducibility of Results; Safety; Thioguanine; Time Factors; Treatment Outcome

Many non-responders to azathioprine or mercaptopurine (6-mercaptopurine) have high normal thiopurine methyltransferase activity and preferentially metabolize mercaptopurine to produce 6-methylmercaptopurine instead of the active 6-tioguanine (6-tioguanine) metabolites.. To describe the use of allopurinol in mercaptopurine/azathioprine non-responders to deliberately shunt metabolism of mercaptopurine towards 6-tioguanine.. Fifteen thiopurine non-responders whose metabolites demonstrated preferential metabolism towards 6-methylmercaptopurine are described. Subjects were commenced on allopurinol 100 mg po daily and mercaptopurine/azathioprine was reduced to 25-50% of the original dose. Patients were followed clinically and with serial 6-tioguanine and 6-methylmercaptopurine metabolite measurements.. After initiating allopurinol, 6-tioguanine levels increased from a mean of 185.73 +/- 17.7 to 385.4 +/- 41.5 pmol/8 x 10(8) red blood cells (P < 0.001), while 6-methylmercaptopurine decreased from a mean of 10 380 +/- 1245 to 1732 +/- 502 pmol/8 x 10(8) RBCs (P < 0.001). Allopurinol led to a decrease in white blood cell from a mean of 8.28 +/- 0.95 to 6.1 +/- 0.82 x 10(8)/L (P = 0.01).. The addition of allopurinol to thiopurine non-responders with preferential shunting to 6-methylmercaptopurine metabolites appears to be an effective means to shift metabolism towards 6-tioguanine.

Topics: Allopurinol; Antimetabolites; Azathioprine; Drug Combinations; Drug Resistance; Humans; Immunosuppressive Agents; Inflammatory Bowel Diseases; Mercaptopurine; Thioguanine

To determine the tolerability and safety profile of a low-dose maintenance therapy with 6-TG in azathioprine (AZA) or 6-mercaptopurine (6-MP) intolerant inflammatory bowel disease (IBD) patients over a treatment period of at least 1 year.. Database analysis.. Twenty out of ninety-five (21%) patients discontinued 6-TG (mean dose 24.6 mg; mean 6-TGN level 540 pmol/8 x 10(8) RBC) within 1 year. Reasons for discontinuation were GI complaints (31%), malaise (15%) and hepatotoxicity (15%). Hematological events occurred in three patients, one discontinued treatment. In the 6-TG-tolerant group, 9% (7/75) could be classified as hepatotoxicity. An abdominal ultrasound was performed in 54% of patients, one patient had splenomegaly.. The majority of AZA or 6-MP-intolerant IBD patients (79%) is able to tolerate maintenance treatment with 6-TG (dosages between 0.3 and 0.4 mg/kg per d). 6-TG may still be considered as an escape maintenance immunosuppressant in this difficult to treat group of patients, taking into account potential toxicity and efficacy of other alternatives. The recently reported hepatotoxicity is worrisome and 6-TG should therefore be administered only in prospective trials.

Topics: Adult; Aged; Azathioprine; Drug Tolerance; Female; Humans; Immunosuppressive Agents; Inflammatory Bowel Diseases; Male; Mercaptopurine; Middle Aged; Retrospective Studies; Safety; Thioguanine

Topics: Allopurinol; Antimetabolites; Azathioprine; Drug Combinations; Drug Synergism; Humans; Inflammatory Bowel Diseases; Mercaptopurine; Thioguanine

Nodular hyperplasia (also referred to as nodular regenerative hyperplasia and nodular regenerative hyperplasia of the liver) is a sequel to therapy with thioguanine in patients with hematologic malignancies. Recently, 6-thioguanine has been used to treat patients with inflammatory bowel disease who have been resistant to other forms of therapy.. To study liver biopsies from 3 patients with inflammatory bowel disease who had received thioguanine for more than a year, and who had elevated serum liver enzyme values and underwent percutaneous liver biopsy.. Percutaneous liver biopsies and histologic examinations were performed, including staining with the reticulin silver impregnation method.. All 3 patients had foci of nodular regenerative hyperplasia, which was best seen with the reticulin silver impregnation method.. Thioguanine-treated inflammatory bowel disease patients are at risk for the development of nodular hyperplasia. Reticulin-stained histologic sections are necessary to recognize this change. Further studies are needed to determine the frequency and significance of this change.

Topics: Adult; Humans; Hyperplasia; Inflammatory Bowel Diseases; Liver; Male; Thioguanine

Topics: Dose-Response Relationship, Drug; Humans; Inflammatory Bowel Diseases; Liver; Thioguanine; Time Factors

Topics: Humans; Hyperplasia; Inflammatory Bowel Diseases; Liver; Thioguanine

There are conflicting reports on the role of azathioprine (AZA) thioguanine nucleotide (TGN) metabolites in optimising therapy for inflammatory bowel disease (IBD). The aim of this study was to investigate TGN intrapatient variation, and the relationship between TGN concentrations and disease activity in IBD patients taking long term constant dose AZA.. TGN and methylmercaptopurine nucleotide (MeMPN) concentrations were measured at intervals over a two year period. Disease activity was assessed at each clinic visit using the Crohn's disease activity index or Walmsley simple index for ulcerative colitis.. Serial TGNs were measured in 159 patients (3-14 TGN assays, median 6). Intrapatient variation in TGN concentrations was 1-5-fold (median 1.6); the incidence of non-compliance was 13%. At the end of two years, 131 patients were evaluable at TGN steady state. Of this group, patients who remained in remission had significantly higher mean TGN concentrations than those patients who developed active disease (median TGNs 236 v 175, respectively; median difference 44 pmol (95% confidence interval 1-92); p = 0.04). MeMPN concentrations were not related to AZA efficacy or toxicity.. This study has shown that lower TGN concentrations were linked to the development of active disease, and that TGNs may act as useful markers of compliance. However, it is clear that repeat TGN measurements are required for an unambiguous index of active metabolite exposure. In view of the high intrapatient variability in TGN production over time, TGN measurements may not be currently advocated for routine clinical use.

Topics: Adolescent; Adult; Aged; Alanine Transaminase; Antimetabolites, Antineoplastic; Azathioprine; Child; Child, Preschool; Colitis, Ulcerative; Crohn Disease; Erythrocytes; Female; Humans; Inflammatory Bowel Diseases; Male; Mercaptopurine; Middle Aged; Patient Compliance; Thioguanine; Treatment Outcome

6-Thioguanine (6-TG) has been used as an alternative thiopurine for inflammatory bowel disease (IBD) patients not responsive to or intolerant of azathioprine (AZA) and 6-mercaptopurine (6-MP). 6-TG-related hepatotoxicity, including liver biochemistry value elevations, sinusoidal collagen deposition on electron microscopy, and veno-occlusive disease, have been described related to its use as therapy for neoplastic disease.. We studied 38 liver biopsies from patients treated with 6-TG, almost all of whom (n = 125) received 6-TG for 1 to 3 years at the Inflammatory Bowel Disease Center at Cedars-Sinai Medical Center. All biopsies were fixed in 4% buffered formalin and prepared in the usual manner. Hematoxylin and eosin, Masson's trichrome (trichrome), and reticulin silver impregnation (reticulin) stained slides were studied. In 23 cases, tissue was also prospectively fixed in glutaraldehyde and processed for electron microscopy.. In 20 of the 37 patients studied (53%), nodular regeneration of varying degree was seen with reticulin. In only 4 of these 20 instances (11% of the total) were the changes seen with hematoxylin and eosin and in 3 of the 4, only in retrospect after studying the reticulin preparation. Minimal fibrosis was seen with trichrome in only 13 biopsies (34%), but sinusoidal collagen deposition was observed in 14 of the 23 cases studied with electron microscopy (60%). The biopsy from the 1 patient with nodular hyperplasia obvious with hematoxylin and eosin also demonstrated changes of venous outflow obstruction.. 6-TG-treated IBD patients are at significant risk for nodular hyperplasia, early fibrosis and, less often, venous outflow disease (Budd-Chiari). The natural history of these changes is unknown and follow-up biopsies are needed to determine histologic and clinical sequela. Patients not demonstrating nodular hyperplasia or fibrosis who continue with 6-TG because there are no better therapeutic choices should be periodically rebiopsied.

Topics: Adolescent; Adult; Aged; Chemical and Drug Induced Liver Injury; Child; Female; Focal Nodular Hyperplasia; Humans; Inflammatory Bowel Diseases; Liver Cirrhosis; Male; Microscopy, Electron; Middle Aged; Thioguanine; Time Factors

We aimed at determining the utility of measuring 6-thioguanine (6-TG) and 6-methylmercaptopurine (6-MMP) in inflammatory bowel disease (IBD) patients on azathioprine (AZA) or 6-mercaptopurine (6-MP), whether the described therapeutic range for 6-TG (235-400 pmol/8 x 10(8) red blood cells, RBC) correlated with clinical remission or leukopenia, and if 6-MMP level was a marker for hepatotoxicity (>5,700 pmol/8 x 10(8) RBC).. Study eligibility included an IBD diagnosis of >6 months and either active disease or disease remission of <6 months and the use of AZA/6-MP for >10 wk consecutively. Metabolite levels were evaluated against clinical status, CBC, and hepatic parameters.. Seventy-four of 166 AZA/6-MP users were eligible. 6-TG levels >235 pmol/8 x 10(8) RBC were found in 22/59 (38%) with active disease and in 7/15 with remission (47%, p= 0.16). There was a trend of higher 6-TG levels among those in remission versus those with active disease (mean 325 +/- 284 vs 223 +/- 159 pmol/8 x 10(8) RBC, p= 0.2). No hepatotoxicity was observed, although 12.2% had 6-MMP levels > 5,700 pmol/8 x 10(8) RBC. The correlation between 6-MP dose and 6-TG levels was weak (r = 0.22, p= 0.08). The 6-TG level did not correlate with WBC. There were five instances, each of markedly low levels of both 6-TG and 6-MMP, suggesting noncompliance and of marked 6-MMP levels versus 6-TG.. There was a poor correlation between 6-TG levels and remission. Nonetheless, the measurements of these levels are helpful when patients are on high doses but not achieving remission since noncompliance or metabolism favoring 6-MMP can be established.

Topics: Adult; Azathioprine; Biomarkers; Cohort Studies; Colitis, Ulcerative; Crohn Disease; Dose-Response Relationship, Drug; Drug Administration Schedule; Female; Humans; Inflammatory Bowel Diseases; Male; Maximum Tolerated Dose; Mercaptopurine; Middle Aged; Predictive Value of Tests; Prognosis; Prospective Studies; Risk Assessment; Severity of Illness Index; Thioguanine; Treatment Outcome

Inosine triphosphate pyrophosphatase (ITPase) deficiency occurs with polymorphic frequencies in Caucasians and results in the benign accumulation of the inosine nucleotide ITP. In 62 patients treated with azathioprine for inflammatory bowel disease, the ITPA 94C>A deficiency-associated allele was significantly associated with adverse drug reactions (OR 4.2, 95% CI 1.6-11.5, p = 0.0034). Significant associations were found for flu-like symptoms (OR 4.7, 95% CI 1.2-18.1, p = 0.0308), rash (OR 10.3, 95% CI 4.7-62.9, p = 0.0213) and pancreatitis (OR 6.2, CI 1.1-32.6, p = 0.0485). Polymorphism in the ITPA gene thus predicts AZA intolerance. Alternative immunosuppressive drugs, particularly 6-thioguanine, should be considered for AZA-intolerant patients with ITPase deficiency.

Topics: Alleles; Antimetabolites, Antineoplastic; Azathioprine; Cohort Studies; Drug Resistance, Neoplasm; Genotype; Heterozygote; Humans; Immunosuppressive Agents; Inflammatory Bowel Diseases; Inosine Triphosphatase; Mutation; Odds Ratio; Phenotype; Polymorphism, Genetic; Pyrophosphatases; Retrospective Studies; Thioguanine

Thiopurine drugs are commonly used immunosuppressants in the treatment of inflammatory bowel disease (IBD) as well as in autoimmune hepatitis (AIH), rheumatic diseases and in transplantation medicine. The relatively narrow therapeutic range requires useful therapy control. Therefore, the purpose of this study was to further investigate the rationale and usefulness of therapeutic drug monitoring in the surveillance of thiopurine drug therapy in Crohn's disease, ulcerative colitis and autoimmune hepatitis.. 6-Thioguanine nucleotide (TGN) and 6-methylmercaptopurine nucleotide (MMPN) levels were measured in 182 IBD patients and 18 AIH patients using HPLC-UV.. In our cohort of IBD patients, 18% had TGN levels < 235 pmol/8 x 10 red blood cells (RBC) (recommended range, 235-450 pmol/8 x 10 RBC), 41% of these patients were sent for drug failure. Twenty-four per cent of the IBD patients had TGN levels > 450 pmol/8 x 10 RBC, but only 27% of these experienced adverse effects. Fifty-nine per cent of the patients having drug failure had TGN levels in the recommended range and could therefore be classified as non-responders. In the AIH cohort 33% of the patients had TGN levels below the recommended range but showed clinical response to therapy. MMPN levels increased with the duration of treatment and could be useful for controlling compliance. There was 8.8% of IBD patients who were heterozygous for non-functional TPMT alleles.. TGN monitoring did not identify significant differences between patient groups but allowed the identification of non-responders from non-compliant patients and allowed the differentiation of mild side effects, such as malaise, from genuine toxicity caused by highly increased TGN levels.

Topics: Adolescent; Adult; Aged; Child; Child, Preschool; Chromatography, High Pressure Liquid; Cohort Studies; Colitis, Ulcerative; Crohn Disease; Drug Monitoring; Female; Guanine Nucleotides; Hepatitis, Autoimmune; Heterozygote; Humans; Immunosuppressive Agents; Inflammatory Bowel Diseases; Male; Mercaptopurine; Middle Aged; Purines; Thioguanine; Thionucleotides

Azathioprine (AZA) and its active metabolite mercaptopurine (MP) are frequently used in the management of inflammatory bowel disease. Measurement of the AZA/MP metabolites, thioguanine (TG) and methylmercaptopurine (MMP), has been suggested as a means to optimize therapy with AZA/MP in inflammatory bowel disease.. To evaluate the results of initial AZA/MP metabolite panels sent by gastroenterologists during the first year of its widespread availability.. Initial AZA/MP metabolite panels sent by gastroenterologists to a single laboratory were reviewed and the metabolite panels were interpreted.. Initial metabolite levels were reviewed for 9187 patients. Noncompliance was detected in 263 patients (3%) and under-dosing in 4260 patients (46%). 534 patients (6%) had levels that were consistent with preferential metabolism via the TPMT pathway. The therapeutic goal was achieved in 2444 patients (27%) and an additional 552 patients (6%) had appropriate TG levels but potential hepatotoxicity. 936 patients (10%) had potential TPMT deficiency, and 58 patients (1%) had potential TPMT absence and were at risk for leukopenia. 140 patients (2%) had too high a dose.. Measurement of AZA/MP metabolites can be used by practising gastroenterologists to identify potential reasons for nonresponse to AZA or MP, and to identify patients at risk for certain drug-related toxicities.

Topics: Azathioprine; Humans; Inflammatory Bowel Diseases; Mercaptopurine; Patient Compliance; Risk Factors; Thioguanine

Topics: Humans; Inflammatory Bowel Diseases; Pilot Projects; Safety; Thioguanine

Approximately 10% of inflammatory bowel disease (IBD) patients receiving 6-mercaptopurine (6-MP) or azathioprine (AZA) develop drug hypersensitivity reactions necessitating early discontinuation of these traditional thiopurines. These allergic reactions typically reoccur upon rechallenge. Our recently published pilot study suggested that thioguanine (6-TG), a closely related thiopurine, was efficacious and well tolerated in IBD patients resistant to 6-MP/AZA. The aim of this study was to determine if hypersensitivity reactions to 6-MP/AZA reoccur with 6-TG therapy.. IBD patients allergic to 6-MP and/or AZA were treated with 6-TG as an alternate thiopurine. Hypersensitivity reactions to 6-MP/AZA must have been documented within 6 wk of 6-MP/AZA initiation.. 6-TG was initiated in 21 IBD patients at a median (range) dose of 20 (10-40) mg/day. 6-TG hypersensitivity reaction occurred in only four of 21 (19%) patients after a median time interval of 9 days. Pancreatitis did not reoccur with 6-TG. Eighty-two percent of 6-TG tolerant patients were assessed as improved at last follow-up.. These results suggest that 6-TG may be considered as a possible alternate thiopurine in patients allergic to traditional 6-MP/AZA. Despite these favorable results, candidates for 6-TG should be selected with caution, and its use should be reserved for IBD patients well informed about potential toxicities.

Topics: Adult; Azathioprine; Drug Hypersensitivity; Female; Humans; Immunosuppressive Agents; Inflammatory Bowel Diseases; Intestinal Mucosa; Male; Mercaptopurine; Middle Aged; Pilot Projects; Prospective Studies; Safety; Thioguanine; Treatment Outcome

Thioguanine (6-TG) has been studied as an alternative thiopurine in inflammatory bowel disease (IBD). Short-term safety and efficacy data were favorable. Experience with 6-TG in patients with acute lymphoblastic leukemia raised long-term safety concerns when implicated in nodular regenerative hyperplasia (NRH) of the liver and portal hypertension. The aim of this study was to describe the association between 6-TG and NRH in IBD.. Liver chemistries and complete blood counts were monitored, and patients were encouraged to undergo liver biopsy. Clinical data were collected by chart review, and associations were tested by univariate and multivariable analyses. Patients were classified based on the presence (group 1) or absence (group 2) of laboratory abnormalities.. Laboratory abnormalities occurred in 29 of 111 patients (26%). Elevations of liver enzymes and a decrease in platelet counts (<200,000) were most commonly observed. Male gender (odds ratio, 2.9; 95% CI, 1.1-7.3; P < 0.03) and preferential 6-methylmercaptopurine production on 6-mercaptopurine/azathioprine (odds ratio, 3.0; 95% CI, 1.2-7.4; P < 0.04) were independently associated with laboratory abnormalities. No association was seen with duration of 6-TG treatment, cumulative dose, or 6-TG nucleotide levels. The median increase in alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase levels was 39, 30, and 75 U/L, respectively, in group 1, and the median decrease in platelet count was 115,000 in group 1 versus 7000 in group 2 (P < 0.001). NRH occurred in 76% of patients undergoing biopsy in group 1 and 33% in group 2.. NRH is a common finding in 6-TG-treated patients with IBD. The progression or reversibility of NRH remains unknown. Our findings suggest that 6-TG should not be considered as therapy for patients with IBD.

Topics: Adolescent; Adult; Aged; Aged, 80 and over; Biopsy; Female; Humans; Hyperplasia; Inflammatory Bowel Diseases; Liver; Male; Middle Aged; Thioguanine

Topics: Humans; Inflammatory Bowel Diseases; Methyltransferases; Thioguanine

Topics: Humans; Inflammatory Bowel Diseases; Methyltransferases; Thioguanine

Topics: Azathioprine; Drug Hypersensitivity; Humans; Immunosuppressive Agents; Inflammatory Bowel Diseases; Mercaptopurine; Thioguanine

The immunosuppressive properties of 6-mercaptopurine and its parent compound azathioprine are mediated by their intracellular metabolism into active 6-thioguanine (6-TG) metabolites. Measurement of erythrocyte 6-TG metabolite levels has been proposed as a useful clinical tool for assessing treatment efficacy in patients with inflammatory bowel disease (IBD).. The purpose of the study was to establish a therapeutic index of treatment efficacy based on measurement of erythrocyte 6-TG metabolite levels, and apply it clinically to guide therapy.. Heparinised blood was obtained from 82 adult patients with IBD on long term (more than three months) antimetabolite therapy (63 Crohn's disease; 19 ulcerative colitis). Erythrocyte 6-TG metabolite levels were measured using reverse phase high performance chromatography, and correlated with treatment efficacy. In 22 patients with refractory Crohn's disease despite long term azathioprine therapy, their dosage was increased by 25 mg/day at eight week intervals as needed. Serial erythrocyte 6-TG metabolite levels were measured at each clinic visit and correlated with treatment efficacy.. Clinical remission, as defined by a low disease index score in patients weaned off or on a low alternate day dose (<20 mg on alternate days) of corticosteroid, was achieved in 68% of patients on long term antimetabolite therapy. Treatment efficacy correlated with erythrocyte 6-TG levels greater than 250 pmol/8x10(8) red blood cells in patients with colonic and fistulising Crohn's disease (p<0.01) but not in patients with ileocolonic disease. Eighteen of 22 patients with incompletely responsive Crohn's disease achieved disease remission by optimising their dose of azathioprine therapy. Median (range) erythrocyte 6-TG metabolite levels increased from 194 (67-688) to 303 (67-737) pmol/8x10(8) red blood cells (p<0.05). Clinical response associated well with a reduction in corticosteroid requirements. Mean (SEM) white blood cell count decreased from 8.6 (0.9) to 6.9 (0.6) x10(3)/microl with adjustment in azathioprine dosage. No patient incurred azathioprine induced leucopenia.. Measurement of erythrocyte 6-TG metabolite levels is helpful in determining the adequacy of azathioprine dosage and can be used to optimise the dose of antimetabolite therapy to achieve an improved clinical response without inducing leucopenia. Patients who are clinically refractory to azathioprine therapy despite achieving high erythrocyte 6-TG levels (>250) should be considered for adjunct or alternative forms of immunosuppressive therapy or surgery.

Topics: Adolescent; Adult; Aged; Azathioprine; Chromatography, High Pressure Liquid; Drug Administration Schedule; Erythrocytes; Female; Humans; Immunosuppressive Agents; Inflammatory Bowel Diseases; Male; Middle Aged; Reference Values; Remission Induction; Thioguanine; Treatment Outcome

The conversion of the cytotoxic and immunosuppressive 6-mercaptopurine (6MP) to the active 6-thioguanine nucleotides (6TGN) is necessary for clinical efficacy of 6MP and its prodrug azathioprine. Another metabolite, 6-methylmercaptopurine nucleotide (6MMPN), is formed via a competing pathway by thiopurine methyl transferase. The concentrations of 6TGN and 6MMPN are measured in washed erythrocytes as a surrogate to the intracellular levels of these metabolites in the target tissues. Analysis of 6TGN and 6MMPN in multi-center clinical studies is more complicated because of the requirement to wash erythrocytes. In this investigation, we found no differences in the concentrations of 6TGN and 6MMPN in blood versus washed erythrocytes in samples obtained from patients taking therapeutic doses of oral 6MP or azathioprine for inflammatory bowel disease. We concluded that whole blood could be used for the analysis of these analytes, thus saving sample preparation time. We also found that the erythrocyte 6TGN concentration in blood at ambient temperature declined 2-4% per day, a loss that can be avoided by shipping blood samples frozen. The loss of 6TGN in blood stored at approximately -80 degrees C was 1% after 1 week and 12% after 24 weeks, indicating the analyte was moderately stable. 6MMPN in blood did not significantly change after 24 weeks of storage at approximately -80 degrees C. In addition, the sensitivity of the 6TGN assay was improved by modifying the HPLC conditions, which made the method more suitable for quantifying low levels of 6TGN in human intestinal biopsy samples and blood.

Topics: Chromatography, High Pressure Liquid; Humans; Inflammatory Bowel Diseases; Mercaptopurine; Reproducibility of Results; Spectrometry, Fluorescence; Thioguanine

Some authors suggest that efficacy of 6-mercaptopurine (6-MP) in patients with inflammatory bowel disease correlates with circulating 6-thioguanine (6-TG) levels more than 235 pmol/8 x 10(8) red blood cells. The authors evaluated the relation between 6-MP metabolite levels and disease activity in children and adolescents with inflammatory bowel disease.. Clinical status and hematologic and hepatic parameters were determined in 101 children with inflammatory bowel disease from a single center and compared with 6-MP metabolite levels.. There was a trend for higher 6-TG levels among patients in remission than among those with active disease (217 vs. 173); however the difference was not statistically significant ( P = 0.09). The likelihood of therapeutic response did not increase significantly at 6-TG levels greater than 235 pmol/8 x 10(8) red blood cells (odds ratio 1.7; P = 0.1). In the current study, 58% of patients in remission had 6-TG levels less than 235. However, serial measurements of 6-MP metabolite levels in 50 patients with active disease showed that increasing 6-TG levels correlated significantly with disease remission in patients followed up longitudinally ( P = 0.04). Leukopenia was significantly associated with high 6-TG levels ( P = 0.03) but not with clinical response ( P = 0.2).. These data suggest that the target range of 6-TG levels previously described by others did not apply to 58% of the pediatric patients with IBD in remission. However, serial monitoring of 6-MP metabolite levels in individual patients with active disease should allow dose escalation and induction of remission while minimizing the risk of toxicity.

Topics: Adolescent; Antimetabolites, Antineoplastic; Azathioprine; Child; Cross-Sectional Studies; Erythrocytes; Humans; Inflammatory Bowel Diseases; Leukocyte Count; Leukopenia; Liver; Male; Mercaptopurine; Odds Ratio; Retrospective Studies; Thioguanine; Treatment Outcome

Topics: Antimetabolites, Antineoplastic; Azathioprine; Biomarkers; Humans; Inflammatory Bowel Diseases; Mercaptopurine; Methyltransferases; Pilot Projects; Prospective Studies; Thioguanine