Thiopurine toxicity is related to genetic polymorphism. Thiopurine methyltransferase (TPMT) variants do not explain thiopurine toxicity in more than half of patients. Asians, despite the low prevalence of TPMT variants, are more susceptible to thiopurine toxicity. Since 2014, studies from many Asian countries have shown a strong association between nucleoside diphosphate-linked moiety X-type motif (NUDT) 15 polymorphism and thiopurine-induced myelotoxicity.

An English language literature search was performed for TPMT and NUDT15 genetic variants in inflammatory bowel disease and other diseases. This article discusses the merits of preemptive NUDT15 and TPMT testing in Asian and non-Asian IBD populations.

The NUDT polymorphism occurs in up to 27% of the Asian and Hispanic population. Hematological toxicity occurs in up to one-third of patients with this genetic variant. Given this, preemptive testing for NUDT15 variant is worthwhile and is probably more cost-effective than TPMT testing in these groups. Prevalence of NUDT15 variants is low in non-Finnish European population, but NUDT15 variants have been linked to myelotoxicity along with TPMT genetic variants. NUDT15 preemptive testing should be considered in the migrant Asian population in Europe and North America and in Caucasian populations who develop myelotoxicity.

Azathioprine (AZA) has been widely used for the treatment of various immune-related diseases and has become a mainstay in the treatment of inflammatory bowel disease. However, patients with genetic mutations may experience severe adverse events when treated with azathioprine. Most of the previous literature focused on the TPMP gene-related adverse reactions, herein, we report a case of Crohn's disease patient with nucleoside diphosphate-linked moiety X motif 15 gene (NUDT15) variation and wild-type TPMP gene who developed toxoplasma gondii infection after azathioprine treatment.

A 56-year-old Crohn's disease patient developed toxoplasma gondii infection within 2 months after the administration of azathioprine; however, he had no relevant high-risk factors.

Subsequent genetic testing revealed that the patient was heterozygous for NUDT15. Therefore, it was reasonable to consider that the patient's genetic mutation resulted in reduced tolerance to azathioprine, leading to low immunity and eventually toxoplasma infection.

AZA was then discontinued; after anti-infection, antipyretic and other supportive treatments were administered, the patient's condition gradually improved.

The patient was followed up at 1, 3, and 6 months after discharge; fortunately, he was in good health.

We report a case of Crohn's disease in a patient who developed severe pneumonia caused by toxoplasma gondii infection due to the administration of AZA, with normal TPMP gene but NUDT15 gene mutation. This indicates that NUDT15 variation may contribute to severe adverse events in patients treated with azathioprine, and we suggest that NUDT15 genotype be detected before the use of azathioprine in order to provide personalized therapy and reduce side effects.

Ulcerative colitis (UC) and Crohn's disease (CD) are chronic inflammatory bowel diseases (IBD) of unknown etiology, characterized by repeated relapse and remission. The efficacy of thiopurine in IBD was first reported in the late 1960s. Thiopurines are used to alleviate the symptoms of IBD, especially UC. These drugs have a steroid-sparing potential and are widely used for the purpose of maintaining long-term remission in steroid-dependent cases. Therefore, thiopurines tend to be used long-term, but adverse events that accompany long-term use, such as lymphoproliferative disorders, must be monitored with care. In contrast, thiopurine plays a critical role in controlling the immunogenicity of biologics. Furthermore, although thiopurine is an old drug, new findings, including the prediction of serious adverse events such as severe alopecia and acute advanced leukopenia, by nudix hydrolase 15 gene polymorphism analysis, as well as the possibility of appropriate drug monitoring by detailed analysis of 6-thioguanine nucleotides have been clarified. However, the consequences of thiopurine withdrawal have not been determined and further studies, including randomized controlled trials, are necessary to answer the clinical question regarding the scenarios in which thiopurine withdrawal is possible.

Inflammatory bowel diseases are chronic relapsing immune-mediated diseases of the intestinal tract with multifaceted manifestations and treatment related morbidity. Faecal and blood tests, radiological, endoscopic and histologic investigations are now widely used for managing both ulcerative colitis and Crohn's disease. Over the years, a number of new investigations have been proposed but not widely adopted yet. Patients with Crohn's disease may have multiple causes of diarrhoea, not always attributable to disease exacerbation, but sometimes linked to bile acid malabsorption; we have a reliable serum test, C4, that allows us to recognize and treat this cause of diarrhoea efficaciously and not empirically, but it is not available or used widely. There is genetic inter-individual variability in drug responses, in terms of both efficacy and toxicity, leading to high rates of therapeutic failure. Patients treated with thiopurine or, more rarely, 5-aminosalicylic acid may suffer from unpredictable and serious adverse events, some of these with pathogenesis related to genetic variants: myelosuppression, acute pancreatitis and nephrotoxicity. The identification of pre-treatment genetic tests can optimize therapeutic choice and avoid adverse events. With regard to biological drugs, patients can experience primary non-response or loss of response due to induction of immune responses to the drugs affecting drug efficacy and determining hypersensitivity reactions. We have specifically reviewed a number of investigations, whose use is currently limited, and highlighted four tests that deserve to be more widely incorporated in clinical practice as these could improve medical decision-making and patient outcomes.

Thiopurines have been widely used for the maintenance of remission or steroid sparing in patients with inflammatory bowel disease. However, potential drug-related adverse events frequently interfere with their use. Indeed, drug withdrawals associated with adverse reactions have been reported in approximately 25% of patients. To balance the efficacy, safety, and tolerability of thiopurines, regular monitoring of biomarkers (complete blood cell count, liver function test, and metabolic profiles), steady dose escalation, and pretreatment thiopurine S-methyltransferase (TPMT) genotype screening have been routinely recommended. However, the complex thiopurine metabolic pathway and individual differences attributed to pharmacogenetic diversity limit the effectiveness of these strategies in the optimization of thiopurine therapy. Recently, in an effort to facilitate more accurate and personalized prediction of thiopurine response or toxicity, novel genetic markers including NUDT15 and FTO genes were discovered. These discoveries are remarkable because TPMT screening has minimal efficacy for predicting myelosuppression especially in Asian populations, despite the fact that thee populations have a higher frequency of myelosuppression than Western populations. This review focuses on the current understanding of the metabolic pathway and the pharmacogenetics of thiopurines and suggests a personalized preventive strategy against potential adverse drug reactions to optimize their therapeutic application.

Decreased thiopurine S-methyltransferase [TPMT] enzyme activity increases the risk of haematological adverse drug reactions [ADRs] in patients treated with thiopurines. Clinical studies have shown that in patients with inflammatory bowel disease [IBD], pharmacogenetic TPMT-guided thiopurine treatment reduces this risk of ADRs. The aim of this study was to investigate whether this intervention impacts on healthcare costs and/or quality of life.

An a priori defined cost-effectiveness analysis was conducted in the Thiopurine response Optimization by Pharmacogenetic testing in Inflammatory bowel disease Clinics [TOPIC] trial, a randomized controlled trial performed in 30 Dutch hospitals. Patients diagnosed with IBD [age ≥18 years] were randomly assigned to the intervention [i.e. pre-treatment genotyping] or control group. Total costs in terms of volumes of care, and effects in quality-adjusted life years [QALYs], based on EuroQol-5D3L utility scores, were measured for 20 weeks. Mean incremental cost savings and QALYs with confidence intervals were calculated using non-parametric bootstrapping with 1000 replications.

The intervention group consisted of 381 patients and the control group 347 patients. The mean incremental cost savings were €52 per patient [95% percentiles -682, 569]. Mean incremental QALYs were 0.001 [95% percentiles -0.009, 0.010]. Sensitivity analysis showed that the results were robust for potential change in costs of screening, costs of biologicals and costs associated with productivity loss.

Genotype-guided thiopurine treatment in IBD patients reduced the risk of ADRs among patients carrying a TPMT variant, without increasing overall healthcare costs and resulting in comparable quality of life, as compared to standard treatment.

Thiopurine S-methyltransferase (TPMT) testing, either by genotyping or phenotyping, can reduce the incidence of adverse severe myelotoxicity episodes induced by azathioprine. The comparative cost-effectiveness of TPMT genotyping and phenotyping are not known.

Our aim was to assess the cost-effectiveness of phenotyping-based dosing of TPMT activity, genotyping-based screening and no screening (reference) for patients treated with azathioprine.

A decision tree was built to compare the conventional weight-based dosing strategy with phenotyping and with genotyping using a micro-simulation model of patients with inflammatory bowel disease from the perspective of the French health care system. The time horizon was set up as 1 year. Only direct medical costs were used. Data used were obtained from previous reports, except for screening test and admission costs, which were from real cases. The main outcome was the cost-effectiveness ratios, with an effectiveness criterion of one averted severe myelotoxicity episode.

The total expected cost of the no screening strategy was €409/patient, the total expected cost of the phenotyping strategy was €427/patient, and the total expected cost of the genotyping strategy was €476/patient. The incremental cost-effectiveness ratio was €2602/severe myelotoxicity averted in using the phenotyping strategy, and €11,244/severe myelotoxicity averted in the genotyping strategy compared to the no screening strategy. At prevalence rates of severe myelotoxicity > 1%, phenotyping dominated genotyping and conventional strategies.

The phenotype-based strategy to screen for TPMT deficiency dominates (cheaper and more effective) the genotype-based screening strategy in France. Phenotype-based screening dominates no screening in populations with a prevalence of severe myelosuppression due to azathioprine of > 1%.

The value of therapeutic drug monitoring during azathioprine (AZA) therapy with respect to clinical outcomes has been convincingly demonstrated in recent meta-analyses. However, the association between AZA metabolites and the mucosal state in inflammatory bowel disease is largely unclear.

We investigated the association between AZA's active metabolite 6-thioguanine nucleotides (6-TGN) and fecal calprotectin (FC) as a well-validated surrogate marker of mucosal inflammation in patients with Crohn's disease (CD) on AZA monotherapy.

Of 443 6-TGN measurements, 140 values from 88 patients with CD on AZA monotherapy visiting the inflammatory bowel disease outpatient clinic between 2009 and 2016 were retrospectively analyzed. In a subcohort with serial 6-TGN measurements, longitudinal FC measurements in patients with versus without intervention (dose increase, allopurinol, and education) were assessed.

In patients with 6-TGN concentrations within a predefined range (250-450 pmol/8×10 red blood cells), FC was significantly lower (median: 119.5 vs. 327.2 mg/kg, P=0.003), and hemoglobin as well as serum protein concentrations were significantly higher than in patients with 6-TGN outside of this range. C-reactive protein and transferrin saturation were not different. In the longitudinal cohort, 6-TGN increased in the intervention group, but only a minority reached the defined range; no significant change in FC was observed.

This study is the first to show that in patients with CD receiving AZA monotherapy, 6-TGN concentrations within a defined range (250-450 pmol/8×10 red blood cells) are associated with significantly lower FC. A treat-to-target concept directed by 6-TGN to reach mucosal healing may thus be a promising approach (DRKS00013246).

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.

There is evidence that genotyping for the thiopurine S-methyltransferase (TPMT) gene variants is useful for the prediction of response to thiopurine analogs (azathioprine and 6-mercaptopurine) in patients with inflammatory bowel disease (IBD). The aim of the present study was to determine the prevalence of TPMT gene polymorphisms in a genetic homogenous population of IBD patients in Crete and to correlate the results with adverse reactions to thiopurine drugs.

Genotyping for the most common TPMT variants TPMT*2, TPMT*3A, TPMT3*C, and TPMT*3B was performed using the PCR-restriction fragment length polymorphism method in 223 consecutive IBD patients and 119 age-matched and sex-matched healthy controls. The hospital medical records were reviewed for thiopurine use in these patients and related adverse events.

The prevalence of TPMT variants TPMT*2, TPMT*3A, TPMT*3B, and TPMT*3C was 1.8, 2.7, 1.3, and 1.8%, respectively. The G238C mutation was detected in four (1.8%) out of 223 patients, three (1.3%) patients were carriers of the G460A mutation, four (1.8%) of the A719G mutation, and six (2.7%) of both G460A and A719G mutations. In healthy controls, only one (0.8%) carried both the G460A and the A719G mutation, whereas TPMT*2, TPMT*3C, and TPMT*3B were not detected. None of the genotypes was homozygous. A statistically significant correlation between the presence of the G460A mutation and the development of leucopenia after the administration of thiopurines was observed (P=0.048).

This study showed a lower frequency of total TPMT variants and a higher frequency of TPMT*3B in Cretan IBD patients compared with other Caucasian populations. The presence of the G460A mutation is associated with the development of leukopenia.

To evaluate how Italian gastroenterologists use corticosteroids in clinical practice for the treatment of Crohn's disease (CD) and ulcerative colitis (UC).

All members of the Italian Group for Inflammatory Bowel Disease (IG-IBD) were invited to fill in a web-based questionnaire.

131/448 (29.2%) members completed the survey. In mild-to-moderate UC and CD relapses, low-bioavailability steroids (LBS) are first-line therapy for 37% and 42% of clinicians, respectively. In case of failure, immediate step-up to biologics or immunosuppressants is considered by 23% and 29%. Regarding conventional corticosteroids (CCS), a fixed starting dose is prescribed by 50%, and a weight-based dose by 22%. Tapering is started after 7-10days by 41% and after 14days by 32%. The preferred tapering schedule is 5mg/week. In case of CCS failure, 47% switch to parenteral steroids before considering shifting to different drug classes. In case of symptoms recurrence during tapering, 14% re-increase the dose and try tapering again. Before prescribing steroids, 72% do not prescribe any specific evaluation whereas during treatment some evaluation is performed by 85%. Vitamin D and calcium supplements are routinely prescribed along with steroids by 38%.

Several discrepancies and some deviation from the available guidelines were recorded among Italian gastroenterologists regarding corticosteroids use in IBD patients.

Improving the efficacy and reducing the toxicity of thiopurines and methotrexate (MTX) have been areas of intense basic and clinical research. An increased knowledge on pharmacodynamics and pharmacokinetics of these immunomodulators has optimized treatment strategies in inflammatory bowel disease (IBD). This review focuses on the metabolism and mode of action of thiopurines and MTX, and provides an updated overview of individualized treatment strategies in which efficacy in IBD can be increased without compromising safety. The patient-based monitoring instruments adapted into clinical practice include pretreatment thiopurine S-methyltransferase testing, thiopurine metabolite monitoring, and blood count measurements that may help guiding the dosage to improve clinical outcome. Other approaches for optimizing thiopurine therapy in IBD include combination therapy with allopurinol, 5-aminosalicylates, and/or biologics. Similar strategies are yet to be proven effective in improving the outcome of MTX therapy. Important challenges for the management of IBD in the future relate to individualized dosing of immunomodulators for maximal efficacy with minimal risk of side effects. As low-cost conventional immunomodulators still remain a mainstay in pharmacotherapy of IBD, more research remains warranted, especially to substantiate these tailored management strategies in controlled clinical trials.

Thiopurines (azathioprine and mercaptopurine) are one of the immunosuppressive mainstays for the treatment of inflammatory bowel disease. In spite of its widespread use, thiopurine metabolism is still not fully understood, and a significant proportion of patients suffer toxicity or lack of efficacy. Different enzymatic pathways with individual variations constitute a pharmacogenetic model that seems to be suitable for monitoring and therapeutic intervention. This review is focused on current concepts and recent research that may help clinicians to rationally optimise thiopurine treatment in patients with inflammatory bowel disease.

Whether low-dose azathioprine (AZA) is effective in maintaining remission in patients with steroid-dependent ulcerative colitis (UC) remains unclear. We assessed the efficacy and safety of low-dose AZA in a Chinese population with UC.

We identified steroid-dependent UC patients in clinical remission on AZA maintenance therapy from a territory-wide IBD Registry. Standard- and low-dose AZA were defined as at least 2 mg/kg/day and less than 2 mg/kg/day, respectively. Relapse rates were analyzed by Kaplan-Meier analysis and compared using log-rank test.

Among 1226 UC patients, 128 (53% male, median duration on AZA 44 months) were included. Median maintenance AZA dose was 1.3 mg/kg/day. 97.7% of the patients were on concomitant oral 5-aminosalicylic acid. Cumulative relapse-free rates in patients on standard-dose and low-dose AZA were 71.2%, 52.8% and 45.2%, and 71.8%, 55.3% and 46.2% at 12, 24 and 36 months, respectively (p = 0.871). Relapse rate within 12 months was higher in patients who withdrew compared with those who maintained on AZA (52.6% versus 29.4%; p = 0.045). Mean corpuscular volume increased after AZA therapy in both of the low-dose [median (interquartile range, IQR): 88.2 (81.4-92.2) versus 95.1 (90.1-100.9) fl, p < 0.001] and standard-dose subgroups [median (IQR) 86.8 (76.9-89.9) versus 94.7 (85.9-99.7) fl, p < 0.001]. Leukopenia occurred in 21.1% of the patients. Patients on standard dose had a higher risk for leukopenia than those on low-dose AZA [odds ratio (OR) 3.9, 95% CI 1.9-8.2, p < 0.001].

In the Chinese population, low-dose AZA is effective for maintaining remission in steroid-dependent UC patients. Standard-dose AZA was associated with more than threefold increased risk of leukopenia.

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.

Crohn's disease (CD) requires treatment beyond symptoms by enabling and maintaining mucosal healing and therefore clinical remission. However, with the increasing use of biologics there have been safety concerns and there is a significant cost implication with the early use of biologics. Therefore, it is imperative that patients with severe/complicated disease or poor prognostic factors are treated with an aggressive strategy while all remaining patients should be treated in a step-up strategy. The potential for disease modification with thiopurines and methotrexate is debated in CD when they are used as a monotherapy. In this review we discuss existing and newer therapies that have recently been developed for CD. We will also provide an algorithm for current management of adult CD patients in routine clinical practice.

More than 20% of patients with inflammatory bowel disease (IBD) discontinue thiopurine therapy because of severe adverse drug reactions (ADRs); leukopenia is one of the most serious ADRs. Variants in the gene encoding thiopurine S-methyltransferase (TPMT) alter its enzymatic activity, resulting in higher levels of thiopurine metabolites, which can cause leukopenia. We performed a prospective study to determine whether genotype analysis of TPMT before thiopurine treatment, and dose selection based on the results, affects the outcomes of patients with IBD.

In a study performed at 30 Dutch hospitals, patients were assigned randomly to groups that received standard treatment (control) or pretreatment screening (intervention) for 3 common variants of TPMT (TPMT*2, TPMT*3A, and TPMT*3C). Patients in the intervention group found to be heterozygous carriers of a variant received 50% of the standard dose of thiopurine (azathioprine or 6-mercaptopurine), and patients homozygous for a variant received 0%-10% of the standard dose. We compared, in an intention-to-treat analysis, outcomes of the intervention (n = 405) and control groups (n = 378) after 20 weeks of treatment. Primary outcomes were the occurrence of hematologic ADRs (leukocyte count < 3.0*10(9)/L or reduced platelet count < 100*10(9)/L) and disease activity (based on the Harvey-Bradshaw Index for Crohn's disease [n = 356] or the partial Mayo score for ulcerative colitis [n = 253]).

Similar proportions of patients in the intervention and control groups developed a hematologic ADR (7.4% vs 7.9%; relative risk, 0.93; 95% confidence interval, 0.57-1.52) in the 20 weeks of follow-up evaluation; the groups also had similar mean levels of disease activity (P = .18 for Crohn's disease and P = .14 for ulcerative colitis). However, a significantly smaller proportion of carriers of the TPMT variants in the intervention group (2.6%) developed hematologic ADRs compared with patients in the control group (22.9%) (relative risk, 0.11; 95% confidence interval, 0.01-0.85).

Screening for variants in TPMT did not reduce the proportions of patients with hematologic ADRs during thiopurine treatment for IBD. However, there was a 10-fold reduction in hematologic ADRs among variant carriers who were identified and received a dose reduction, compared with variant carriers who did not, without differences in treatment efficacy. ClinicalTrials.gov number: NCT00521950.

The adequacy of exposure of purine analogs as measured by 6-thioguanine nucleotides concentrations in the setting of combination therapy remains poorly understood. The aim of this study was to investigate the relationship between the mean corpuscular volume (MCV) value (as a surrogate marker of 6-thioguanine nucleotides concentration) and Crohn's disease outcomes in the setting of combination therapy with infliximab.

The SONIC trial was a randomized controlled trial comparing infliximab to azathioprine and to infliximab plus azathioprine in 508 Crohn's disease patients. An increase of at least 7 femtoliter (fL) of the MCV (ΔMCV) was used for statistical analysis.

At week 26, the mean increase of MCV was similar among patients treated with azathioprine alone (mean of 7.9 fL) or in combination with infliximab (mean of 8.5 fL). In the azathioprine group, 63.6% of patients with ΔMCV >7 were in steroid-free clinical remission at week 26 as compared with 33.3% of patients without ΔMCV >7 (P = 0.0046). In the combination therapy group, ΔMCV above 7 was associated with mucosal healing (75.0% for ΔMCV >7 versus 47.1% for ΔMCV <7, P = 0.0172) but not with steroid-free clinical remission. Patients with a ΔMCV above 7 were more likely to have infliximab trough level above 3 μg/mL at week 30 (68.4% versus 38.8% for ΔMCV <7, P = 0.0032).

These results suggest that ΔMCV above 7 (which is a surrogate for a higher 6-thioguanine nucleotides concentration) leads to improved Crohn's disease outcomes, even when combined with infliximab. It also suggests the possibility that a lower azathioprine exposure might be less effective in combination therapy.

The ideal manner of thiopurine use in inflammatory bowel disease has not been defined. We aimed at investigating the attitudes of Italian gastroenterologists on thiopurine use.

A web-based survey was performed among 295 gastroenterologists.

Overall, 70 surveys were completed. At baseline, thiopurine methyltransferase genotype and phenotype were not assessed by 87.1% and 97.1% of respondents, respectively. At treatment onset, 17.1% adopted full weight-calculated dose while 80.0% preferred escalating the dose. During treatment, 87.1% and 64.3% reduced the dose for myelo- and liver toxicity, respectively; 48.6% for increased pancreatic enzymes, 17.1% for fever, and 5.7% for arthralgia. A systematic shift from one thiopurine to the other was reported by 4.3% of respondents in case of failure, and by 5.7% for adverse effects. Forty-four gastroenterologists (62.9%) stopped thiopurine treatment after 5-7 years.

Several discrepancies regarding the use of thiopurines in clinical practice were found, deviating from available guidelines. A more standardised attitude is needed in clinical practice.

The activity of the enzyme thiopurine methyltransferase (TPMT) is regulated by a common genetic polymorphism. One in 300 individuals lack enzyme activity and 11% are heterozygous for a variant low activity allele and have an intermediate activity. The thiopurine drugs azathioprine, mercaptopurine and thioguanine are substrates for TPMT; these drugs exhibit well documented myelosuppressive effects on haematopoietic cells and have a track record of idiosyncratic drug reactions. The development of severe bone marrow toxicity, in patients taking standard doses of thiopurine drugs, is associated with TPMT deficiency whilst the TPMT heterozygote is at an increased risk of developing myelosuppression. Factors influencing TPMT enzyme activity, as measured in the surrogate red blood cell, are discussed in this review to enable an appreciation of why concordance between TPMT genotype and phenotype is not 100%. This is particularly important for lower/intermediate TPMT activities to avoid misclassification of TPMT status. TPMT testing is now widely available in routine service laboratories. The British National Formulary suggests TPMT testing before starting thiopurine drugs. Dermatologists were quick to adopt routine TPMT testing whilst gastroenterologists do not specifically recommend TPMT screening. TPMT testing is mandatory prior to the use of mercaptopurine in childhood leukaemia. Thiopurine drug dose and other treatment related influences on cell counts explain some of the differing recommendations between clinical specialities. TPMT testing is cost-effective and the major role is in the identification of the TPMT deficient individual prior to the start of thiopurine drugs.

Many placebo controlled trials and meta-analyses evaluated the efficacy of different drugs for the treatment of inflammatory bowel disease (IBD), including immunosuppressants and biologics. Their use is indicated in moderate to severe disease in non responders to corticosteroids and in steroid-dependent patients, as induction and maintainance treatment. Infliximab, as well as cyclosporine, is considered a second line therapy in the case of severe ulcerative colitis, or non-responders to intravenous corticosteroids. An adequate dosage and duration of therapy with thiopurines should be reached before evaluating their efficacy. Methotrexate is a valid option in patients with Crohn's disease but its use is confined to patients who are intolerant or non-responders to thiopurines. Evidence for the use of methotrexate in ulcerative colitis is insufficient. The use of thalidomide and mycophenolate mofetil is not recommended in patients with inflammatory bowel disease, these treatments could be considered in case of failure of all other therapeutic options. In patients with moderately active ulcerative colitis, refractory to thiopurines, the use of tacrolimus is considered an alternative to biologics. An increase of the dose or a decrease in the interval of administration of biological treatment could be useful in the presence of an incomplete clinical response. In the case of primary failure of an anti-tumor necrosis factor alpha a switch to another one should be considered. Data on the efficacy of combination therapy are up to now insufficient to consider this strategy in all IBD patients. The final outcome of the treatment should be considered the clinical remission, with mucosa healing, and not the clinical response. The evaluation of serum concentration of thiopurine methyl transferase activity, thiopurine metabolites, biologic serum levels and antibiologic antibodies could be useful for the management of the treatment but it has not been routinely applied in clinical practice. The evidence of high risk development of lymphoma and cutaneous malignancies should be considered in patients treated with immunosuppressants and biologics for a long period.

Therapeutic objectives are currently evolving in inflammatory bowel diseases (IBD) from control of symptoms towards improvement of long-term disease outcomes. In patients achieving remission, safety concerns - infections or neoplasia - and economic issues are prompting de-escalation strategies.

To give a complete overview of studies on de-escalating therapy in IBD.

A structured search in Pubmed, the Cochrane Library and EMBASE was performed using defined key words (inflammatory bowel diseases, Crohn's disease, ulcerative colitis, immunosuppressants, azathioprine, methotrexate, anti-TNF, infliximab, adalimumab, de-escalation, dose reduction, cessation, stopping, withdrawal), including full text articles and abstracts in English language.

Eleven studies were identified, investigating cessation of immunosuppressants (IS) and/or anti-TNF treatments. Patients exposed to a combination of IS and anti-TNF have an increased risk for infections, especially due to opportunistic agent, without any clear signal for associated cancers when compared to those receiving single therapy. In patients receiving IS alone, relapse rate at 12 months following IS cessation is close to 20% and 30% in Crohn's disease (CD) and ulcerative colitis (UC) respectively. There is no study specifically evaluating anti-TNF treatment withdrawal in case of scheduled anti-TNF monotherapy in IBD. In patients receiving combination therapy with IS and infliximab (IFX) for at least 6 months, relapse rate of IFX failure following IS cessation is near to 20% at 24 months and seems to be similar in patients who maintained combination therapy. In case of anti-TNF therapy, cessation in CD patients in combo-therapy proportion of relapse is high, close to 40% and 50% over 1 year and 2 years respectively. Regarding higher risk of adverse events, some special situations - young males, pregnancy and elderly - should be managed specifically and de-escalating treatment considered.

De-escalating treatment strategy should be mainly considered in patients with high risk of severe adverse events and low relapse risk (patients in deep remission) after drug withdrawal. For these reasons, cessation of anti-TNF treatment and/or immunosuppressants should be a case by case decision in highly selected patients.

Thiopurines are the mainstay of medical management in inflammatory bowel disease (IBD), especially in the maintenance of disease remission. Given the limited IBD armamentarium it is important to optimize each therapy before switching to an alternative drug. Conventional weight based dosing of thiopurines in IBD leads to intolerance or inefficacy in many patients. More recently increased knowledge of their metabolism has allowed for dose optimization using thiopurine metabolite levels, namely 6-thioguanine nucleotides and 6-methylmercaptopurine, with the potential for improved outcomes in patients with IBD. This review will outline the current understanding of thiopurine metabolism and pharmacogenomics and will describe the clinical application of this knowledge in the optimization of thiopurines in individual patients.

The thiopurines azathioprine and 6-mercaptopurine are recommended for maintenance of remission in inflammatory bowel disease (IBD). Measurement of concentrations of the metabolites 6-thioguanine nucleotide and 6-methylmercaptopurine helps delineate interindividual variation in metabolism that may underlie variability in efficacy and toxicity.

We aimed to perform a retrospective observational study to determine the utility of thiopurine metabolite testing following its introduction into South Australia.

All patients having thiopurine metabolite tests done at Flinders Medical Centre between November 2008 and January 2010 were identified. Case notes of patients with testing done in the context of treatment for IBD were interrogated to determine the reason for testing, clinical context and outcome.

One hundred and fifty-one patients were identified with thiopurine metabolite testing for IBD with 157 testing episodes. Eighty (51.0%) had testing done for flare or inefficacy, 18 (11.5%) for adverse effects, 5 (3.2%) for a combination of inefficacy and adverse effects, and 54 (34.4%) for routine or other reasons. Testing was followed by improved outcomes of increased efficacy, reduced toxicity or change to alternative therapy in 55.0% of the inefficacy/flare group, 27.8% of the suspected adverse reaction group, 60.0% of the combination group, and 13.0% of the routine/other group. Allopurinol was used as cotherapy in 16 patients and led to marked improvements in metabolite concentrations.

Thiopurine metabolite testing has quickly become established in South Australia. When used for inefficacy or adverse effects, it often leads to improved outcomes. Prospective studies are needed to determine whether routine testing to guide dosing is of benefit.

Considerable variety in how patients respond to treatments, driven by differences in their geno- and/ or phenotypes, calls for a more tailored approach. This is already happening, and will accelerate with developments in personalized medicine. However, its promise has not always translated into improvements in patient care due to the complexities involved. There are also concerns that advice for tests has been reversed, current tests can be costly, there is fragmentation of funding of care, and companies may seek high prices for new targeted drugs. There is a need to integrate current knowledge from a payer's perspective to provide future guidance. Multiple findings including general considerations; influence of pharmacogenomics on response and toxicity of drug therapies; value of biomarker tests; limitations and costs of tests; and potentially high acquisition costs of new targeted therapies help to give guidance on potential ways forward for all stakeholder groups. Overall, personalized medicine has the potential to revolutionize care. However, current challenges and concerns need to be addressed to enhance its uptake and funding to benefit patients.

The US FDA now recognizes the need to individualize treatment paradigms using biomarkers that predict response to therapy. In clinical practice the best example of this is TPMT testing, which is used to rationalize the starting dose of azathioprine and mercaptopurine. The more recent addition of drug metabolite monitoring means that thiopurine therapy can now be personalized to unprecedented levels. Of interest, parallels exist between TPMT deficiency as an explanation for thiopurine toxicity and DPD deficiency in fluoropyrimidine toxicity. For these drugs, variations in a single locus predict severe toxicity. However, while TPMT testing has translated into routine clinical practice, DPD testing has not. This article summarizes the recent research investigating interindividual differences in the metabolism of thiopurine and fluoropyrimidine drugs, and explores the attitudes which influence the uptake of pharmacogenetic testing.

Therapeutic drug monitoring of active metabolites of thiopurines, azathioprine and 6-mercaptopurine, is relatively new. The proposed therapeutic threshold level of the active 6-thioguanine nucleotides (6-TGN) is ≥235 pmol/8×10(8) erythrocytes. The aim of this prospective cross-sectional study was to compare 6-TGN levels in adult thiopurine tolerant IBD patients with an exacerbation with those in remission, and to determine the therapeutic 6-TGN cut-off level.

Hundred IBD patients were included. Outcome measures were thiopurine metabolite levels, calculated therapeutic 6-TGN cut-off level, CDAI/CAI scores, thiopurine dose and TPMT enzyme activity.

Forty-one patients had an exacerbation, 59 patients were in remission. In 17% of all patients 6-TGN levels were compatible with non-compliance. The median 6-TGN levels were not significantly different between the exacerbation and remission group (227 versus 263 pmol/8×10(8) erythrocytes, p=0.29). The previous reported therapeutic 6-TGN cut-off level of 235 pmol/8×10(8) erythrocytes was confirmed in this study. Twenty-six of the 41 patients (63%) with active disease had 6-TGN levels below this threshold and 24 of 59 IBD patients (41%) in clinical remission (p=0.04).

Thiopurine non-compliance occurs frequently both in active and quiescent disease. 6-TGN levels below or above the therapeutic threshold are associated with a significant higher chance of IBD exacerbation and remission, respectively. These data support the role of therapeutic drug monitoring in thiopurine maintenance therapy in IBD to reveal non-compliance or underdosing, and can be used as a practical tool to optimize thiopurine therapy, especially in case of thiopurine non-response.

Thiopurines represent the mainstay of immunosuppressive therapy in inflammatory bowel diseases. Since it is likely that response to therapy and adverse events depends on the genetic background of patients our study aimed to evaluate retrospectively response to therapy and safety in a mixed IBD population in Southern Europe.

We evaluated demographic and clinical data of our patients treated with thiopurines. after 6 months in responders and non-responders to therapy. Moreover the likelihood to remain in thiopurine monotherapy was evaluated in responders, whereas adverse events were investigated in all patients.

Among disease- and patient-related parameters a shorter disease duration, female gender and ileal disease in Crohn's patients were associated with better response. By ROC analysis, the best predictors of response were decreasing values of C-reactive protein and erythrocyte sedimentation rate. In the long-term more than half of IBD patients who responded at 6 months remained on monotherapy at 42 months. Flu-like syndrome represented the most frequent adverse event followed by abnormalities of liver function tests and myelotoxicity. Adverse events did occur at any time and were frequently impredictable.

In this retrospective study, thiopurines showed a good clinical efficacy, especially in patients with short duration of disease. Normalization of markers of systemic inflammation represents the most useful tool to assess response. Careful monitoring of patients is required during the whole duration of treatment although it may not prevent all severe complications.

The need to accurately classify the severity of patients with acute pancreatitis is widely acknowledged but some questions pertinent to this remain debatable. The aim of this study was to benchmark opinions of pancreatologists worldwide with regard to the issues related to classifying the severity of acute pancreatitis.

An online survey was conducted using an independent commercial service. The corresponding authors of all articles pertinent to clinical aspects of acute pancreatitis published over the last 5 years were invited to participate.

A total of 528 invitations were sent and 240 (45%) responses from 49 countries, representing all the inhabited continents, were received. The Atlanta approach to classifying the severity of acute pancreatitis was considered adequate for modern clinical practice and clinical research by 40 (17%) of the respondents. The determinants-based approach to classifying the severity of acute pancreatitis was considered adequate for modern clinical practice and clinical research by 188 (78%) and 191 (80%) of the respondents, respectively. The definitions of local and systemic determinants of severity were also clarified.

Classifying the severity of acute pancreatitis on the basis of Atlanta approach was considered inadequate by the overwhelming majority of respondents. An international consensus on the new classification of severity of acute pancreatitis has to take into account the results of this survey.

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

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

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

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

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.