Thiopurine Therapy in Inflammatory Bowel Diseases: Making New Friends Should Not Mean Losing Old Ones

Thiopurines Have Longer Treatment Durability than Methotrexate in Adults and Children with Crohn's Disease: A Nationwide Analysis from the epi-IIRN Cohort

BACKGROUND

Thiopurines and methotrexate have long been used to maintain remission in Crohn's disease [CD]. In this nationwide study, we aimed to compare the effectiveness and safety of these drugs in CD.

METHODS

We used data from the epi-IIRN cohort, including all patients with CD diagnosed in Israel. Outcomes were compared by propensity-score matching and included therapeutic failure, hospitalisations, surgeries, steroid dependency, and adverse events.

RESULTS

Of the 19264 patients diagnosed with CD since 2005, 3885 [20%] ever received thiopurines as monotherapy and 553 [2.9%] received methotrexate. Whereas the use of thiopurines declined from 22% in 2012-2015 to 12% in 2017-2020, the use of methotrexate remained stable. The probability of sustaining therapy at 1, 3, and 5 years was 64%, 51%, and 44% for thiopurines and 56%, 30%, and 23% for methotrexate, respectively [p <0.001]. Propensity-score matching, including 303 patients [202 with thiopurines, 101 with methotrexate], demonstrated a higher rate of 5-year durability for thiopurines [40%] than methotrexate [18%; p <0.001]. Time to steroid dependency [p = 0.9], hospitalisation [p = 0.8], and surgery [p = 0.1] were comparable between groups. These outcomes reflect also shorter median time to biologics with methotrexate (2.2 [IQR 1.6-3.1 years) versus thiopurines (6.6 [2.4-8.5]; p = 0.02). The overall adverse events rate was higher with thiopurines [20%] than methotrexate [12%; p <0.001], including three lymphoma cases in males, although the difference was not significant [4.8 vs 0 cases/10 000 treatment-years, respectively; p = 0.6].

CONCLUSION

Thiopurines demonstrated higher treatment durability than methotrexate but more frequent adverse events. However, disease outcomes were similar, partly due to more frequent escalation to biologics with methotrexate.

Implications of Tioguanine Dosing in IBD Patients with a TPMT Deficiency

Tioguanine is metabolised by fewer enzymatic steps compared to azathioprine and mercaptopurine, without generating 6-methylmercaptopurine ribonucleotides. However, thiopurine S-methyl transferase (TPMT) plays a role in early toxicity in all thiopurines. We aimed to describe the hazards and opportunities of tioguanine use in inflammatory bowel disease (IBD) patients with aberrant TPMT metabolism and propose preventative measures to safely prescribe tioguanine in these patients. In this retrospective cohort study, all determined TPMT genotypes (2016-2021) were evaluated for aberrant metabolism (i.e., intermediate and poor TPMT metabolisers). Subsequently, all IBD patients on tioguanine with aberrant TPMT genotypes were evaluated for tioguanine dosages, adverse drug events, lab abnormalities, treatment duration and effectiveness. TPMT genotypes were determined in 485 patients, of whom, 50 (10.3%) and 4 patients (0.8%) were intermediate and poor metabolisers, respectively. Of these patients, 12 intermediate and 4 poor TPMT metabolisers had been prescribed tioguanine in varying doses. In one poor TPMT metaboliser, tioguanine 10 mg/day induced delayed pancytopenia. In general, reduced tioguanine dosages of 5 mg/day for intermediate TPMT metabolisers, and 10 mg two-weekly for poor TPMT metabolisers, resulted in a safe, long-term treatment strategy. Diminished or absent TPMT enzyme activity was related with a pharmacokinetic shift of tioguanine metabolism which is associated with relatively late-occurring myelotoxicity in patients on standard tioguanine dose. However, in strongly reduced dose regimens with strict therapeutic drug and safety monitoring, tioguanine treatment remained a safe and effective option in IBD patients with dysfunctional TPMT.

Drug rediscovery in gastroenterology: from off-label to on-label use of thioguanine in inflammatory bowel disease

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.

HLA-DP on Epithelial Cells Enables Tissue Damage by NKp44+ Natural Killer Cells in Ulcerative Colitis

BACKGROUND & AIMS

Ulcerative colitis (UC) is characterized by severe inflammation and destruction of the intestinal epithelium, and is associated with specific risk single nucleotide polymorphisms in HLA class II. Given the recently discovered interactions between subsets of HLA-DP molecules and the activating natural killer (NK) cell receptor NKp44, genetic associations of UC and HLA-DP haplotypes and their functional implications were investigated.

METHODS

HLA-DP haplotype and UC risk association analyses were performed (UC: n = 13,927; control: n = 26,764). Expression levels of HLA-DP on intestinal epithelial cells (IECs) in individuals with and without UC were quantified. Human intestinal 3-dimensional (3D) organoid cocultures with human NK cells were used to determine functional consequences of interactions between HLA-DP and NKp44.

RESULTS

These studies identified HLA-DPA1∗01:03-DPB1∗04:01 (HLA-DP401) as a risk haplotype and HLA-DPA1∗01:03-DPB1∗03:01 (HLA-DP301) as a protective haplotype for UC in European populations. HLA-DP expression was significantly higher on IECs of individuals with UC compared with controls. IECs in human intestinal 3D organoids derived from HLA-DP401pos individuals showed significantly stronger binding of NKp44 compared with HLA-DP301pos IECs. HLA-DP401pos IECs in organoids triggered increased degranulation and tumor necrosis factor production by NKp44+ NK cells in cocultures, resulting in enhanced epithelial cell death compared with HLA-DP301pos organoids. Blocking of HLA-DP401-NKp44 interactions (anti-NKp44) abrogated NK cell activity in cocultures.

CONCLUSIONS

We identified an UC risk HLA-DP haplotype that engages NKp44 and activates NKp44+ NK cells, mediating damage to intestinal epithelial cells in an HLA-DP haplotype-dependent manner. The molecular interaction between NKp44 and HLA-DP401 in UC can be targeted by therapeutic interventions to reduce NKp44+ NK cell-mediated destruction of the intestinal epithelium in UC.

Development and validation of a novel HPLC-UV method for simultaneous determination of azathioprine metabolites in human red blood cells

A rapid, specific and accurate high-performance liquid chromatography with tunable ultraviolet detection method was developed to simultaneously determine azathioprine metabolites, 6-thioguanine nucleotides (6-TGN) and 6-methyl mercaptopurine riboside (6-MMPr) in human red blood cells. Erythrocyte lysate sample was precipitated by perchloric acid under the protection of dithiothreitol, with 6-TGN and 6-MMPr being acid hydrolyzed to produce 6-thioguanine (6-TG) and 6-methymercaptopurine (6-MMP). A Waters Cortecs C₁₈ column (2.1 × 150 mm, 2.7 μm) was used for chromatographic separation with a water (containing 0.01 mol/L ammonium acetate and 0.2% acetic acid)/methanol linear gradient at a flow rate of 0.45 mL/min in a 5.5 min. UV detection wavelengths were 340 nm for 6-TG, 303 nm for 6-MMP and the IS (5-bromouracil). The calibration curves fitted a least squares model (weighed 1/x ²) from 0.15 to 15 μmol/L for 6-TG (r ²  = 0.9999) and from 1 to 100 μmol/L for 6-MMP (r ²  = 0.9998). This method was validated according to the FDA bioanalytical method validation guidance and ICH M10 bioanalytical method validation and study sample analysis guidance for industry, and successfully utilized in ten IBD patients receiving azathioprine therapy.

Predictive Algorithm for Thiopurine-Induced Hepatotoxicity in Inflammatory Bowel Disease Patients

BACKGROUND

Approximately 25% of patients with inflammatory bowel disease (IBD) discontinue azathioprine (AZA) or mercaptopurine (MP) therapy within 3 months of treatment initiation because of adverse drug reactions. Of these side-effects, about half are because of hepatotoxicity. The aim of this study was to validate and (subsequently) optimize a previously reported predictive algorithm for thiopurine-associated hepatotoxicity by increasing the number of patients with IBD benefitting from conventional thiopurine therapy.

METHODS

This multicenter observational study included consecutive thiopurine-naive patients with IBD who received AZA or MP treatment. The primary outcome was hepatotoxicity within 12 weeks. The patients with and without hepatotoxicity were compared. Four determinants, namely, age, sex, body mass index (BMI), and 6-methylmercaptopurine ribonucleotide concentrations 1 week after treatment initiation (T = 1) were used to validate and optimize 2 (1 dichotomous and 1 continuous) algorithms using multivariable logistic regression analysis.

RESULTS

Of 229 patients, 21 (9%) developed hepatotoxicity and 93% of the patients received MP with a median dose of 0.7 mg/kg (95% confidence interval 0.3-1.4 mg/kg). A difference in BMI was found between with and without hepatotoxicity groups (median 27.6 versus 24.2, P = 0.022). Specificities of 68% (Algorithm 1) and 77% (Algorithm 2) and sensitivities of 56% (Algorithm 1) and 50% (Algorithm 2) were obtained.

CONCLUSIONS

Both algorithms demonstrated limited predictive accuracy for thiopurine-induced hepatotoxicity in the validation cohort. Relevant factors contributing to this outcome were changes in thiopurine prescription behavior over time, with more MP prescriptions at relatively lower dosages of MP.

A report on the potential of Rac1/pSTAT3 protein levels in T lymphocytes to assess the pharmacodynamic effect of thiopurine therapy in Inflammatory Bowel Disease patients

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.

Classic drugs in the time of new drugs: real-world, long-term outcomes of thiopurine monotherapy in 1016 patients with inflammatory bowel disease

BACKGROUND

Thiopurines remain recommended as maintenance therapy in patients with inflammatory bowel disease (IBD). Despite their widespread use, long-term effectiveness data are sparse and safety is an increasingly debated topic which thwarts proper delineation in the current IBD treatment algorithm.

AIMS

To document effectiveness and safety of thiopurine monotherapy in patients with IBD, using the population-based IBD South-Limburg (IBDSL) cohort METHODS: All patients starting thiopurine monotherapy as maintenance between 1991 and 2014 were included. Therapy was defined as effective if there was no escalation to biologicals, no course of corticosteroids, no surgery and no hospitalisation for active disease during treatment. Long-term effectiveness was assessed by adjusting for differences in follow-up using Kaplan-Meier analyses. Mid- to long-term safety regarding cancer incidence and clinically relevant liver disease was documented.

RESULTS

In total, 1016 patients (643 Crohn's disease [CD]; 373 ulcerative colitis [UC]) received thiopurine monotherapy at a median of 15.2 (Q1-Q3 4.2-48.5) months after diagnosis. During follow-up, effectiveness rates at 1, 5 and 10 years were 64%, 45%, 32%, respectively, in CD and and 66%, 41%, 36%, respectively in UC. No statistically significant differences in effectiveness were observed after stratification for era of initiation (pre-biological vs biological, CD: p = 0.56; UC: p = 0.43). Sixteen non-melanoma skin cancers (incidence rate [IR] 3.33/1000 PY), five lymphomas (IR 1.04/1000 PY) and one urinary tract cancer (IR 0.21/1000 PY) were recorded. Two cases of portal hypertension were identified.

CONCLUSION

In real-world practice, thiopurine monotherapy remains effective, safe and durable for patients with CD or UC, including in the era of biologics.

Gut Microbiota Metabolism of Azathioprine: A New Hallmark for Personalized Drug-Targeted Therapy of Chronic Inflammatory Bowel Disease

Despite the growing number of new drugs approved for the treatment of inflammatory bowel disease (IBD), the long-term clinical use of thiopurine therapy and the well-known properties of conventional drugs including azathioprine have made their place in IBD therapy extremely valuable. Despite the fact that thiopurine S-methyltransferase (TPMT) polymorphism has been recognized as a major cause of the interindividual variability in the azathioprine response, recent evidence suggests that there might be some yet unknown causes which complicate dosing strategies causing either failure of therapy or toxicity. Increasing evidence suggests that gut microbiota, with its ability to release microbial enzymes, affects the pharmacokinetics of numerous drugs and subsequently drastically alters clinical effectiveness. Azathioprine, as an orally administered drug which has a complex metabolic pathway, is the prime illustrative candidate for such microbial metabolism of drugs. Comprehensive databases on microbial drug-metabolizing enzymes have not yet been generated. This study provides insights into the current evidence on microbiota-mediated metabolism of azathioprine and systematically accumulates findings of bacteria that possess enzymes required for the azathioprine biotransformation. Additionally, it proposes concepts for the identification of gut bacteria species responsible for the metabolism of azathioprine that could aid in the prediction of dose-response effects, complementing pharmacogenetic approaches already applied in the optimization of thiopurine therapy of IBD. It would be of great importance to elucidate to what extent microbiota-mediated metabolism of azathioprine contributes to the drug outcomes in IBD patients which could facilitate the clinical implementation of novel tools for personalized thiopurine treatment of IBD.

Current status and future perspectives on the use of therapeutic drug monitoring of thiopurine metabolites in patients with inflammatory bowel disease

INTRODUCTION

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.

AREAS COVERED

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.

EXPERT OPINION

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.

Early thiopurine maintenance is associated with reduced proximal disease progression and colectomy rate in ulcerative colitis

BACKGROUND

Thiopurines effectively maintain remission in ulcerative colitis patients. Whether early initiation of thiopurines after ulcerative colitis diagnosis decreases proximal disease progression and colectomy rates is not known.

METHODS

We conducted a cohort study of ulcerative colitis subjects recruited from 1970 to 2009. Early thiopurine maintenance was defined as commencement of azathioprine or mercaptopurine within 5 years of diagnosis and maintenance for at least 6 months. Propensity score matching was conducted to correct for confounders influencing early thiopurine introduction. Outcomes of interest were colectomy rate and endoscopic proximal disease extension.

RESULTS

982 consecutive ulcerative colitis subjects (12 879 patient-years) were recruited with 116 requiring colectomy. Thiopurines initiation and maintenance increased over time with median time to thiopurine commencement decreasing from 23 years in the first decade to 2 years in the last decade (P < 0.0001). Multivariate analysis showed that early thiopurine maintenance significantly decreased the need for colectomy [hazard ratio, 0.13; 95% confidence interval (CI):0.03-0.55; P = 0.006]. The number of subjects needed to be treated to reduce one colectomy at 5 and 10 years was 18 (95% CI, 16- 36) and 12 (95% CI, 11-25). After propensity score matching, early thiopurine maintenance was significantly associated with decreased colectomy (hazard ratio, 0.10; 95% CI, 0.03-0.43; P = 0.002) and proximal progression of disease extent (hazard ratio, 0.26; 95% CI, 0.10-0.78; P = 0.015).

CONCLUSION

Early thiopurine maintenance for >6 months is significantly associated with reduced colectomy and proximal progression of disease extent in ulcerative colitis.

Relationship Between Thiopurine S-Methyltransferase Genotype/Phenotype and 6-Thioguanine Nucleotide Levels in 316 Patients With Inflammatory Bowel Disease on 6-Thioguanine

BACKGROUND

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.

METHODS

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).

RESULTS

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).

CONCLUSIONS

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.

Thiopurines in Inflammatory Bowel Disease. How to Optimize Thiopurines in the Biologic Era?

Thiopurines have been a cornerstone in the treatment of inflammatory bowel disease (IBD). Although they have been used for more than 50 years, there are still some unsolved issues about their efficacy and, also, some safety concerns, mainly the risk of myelosuppression and life-threatening lymphoproliferative disorders. Furthermore, the development of biological therapy raises the question whether there is still a role for thiopurines in the IBD treatment algorithm. On the other hand, limited cost and wide availability make thiopurines a reasonable option in settings of limited resources and increasing prevalence of IBD. In fact, there is a growing interest in optimizing thiopurine therapy, since pharmacogenomic findings suggest that a personalized approach based on the genotyping of some molecules involved in its metabolism could be useful to prevent side effects. Polymorphisms of thiopurine methyltransferase enzyme (TPMT) that result in low enzymatic activity have been associated with an increased risk of myelotoxicity, especially in Caucasians; however, in Asians it is assumed that the variants of nudix hydrolase 15 (NUDT15) are more relevant in the development of toxicity. Age is also important, since in elderly patients the risk of complications seems to be increased. Moreover, the primo-infection of Epstein Barr virus and cytomegalovirus under thiopurine treatment has been associated with severe lymphoproliferative disorders. In addition to assessing individual characteristics that may influence thiopurines treatment outcomes, this review also discusses other strategies to optimize the therapy. Low-dose thiopurines combined with allopurinol can be used in hypermethylators and in thiopurine-related hepatotoxicity. The measurement of metabolites could be useful to assess compliance, identify patients at risk of adverse events and also facilitating the management of refractory patients. Thioguanine is also a rescue therapy in patients with toxicity related to conventional thiopurine therapy. Finally, the current indications for thiopurines in monotherapy or in combination with biologics, as well as the optimal duration of treatment, are also reviewed.

A comparative analysis of tioguanine versus low-dose thiopurines combined with allopurinol in inflammatory bowel disease patients

BACKGROUND

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.

AIM

To compare the safety of tioguanine and LDTA in IBD patients.

METHODS

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.

RESULTS

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.

CONCLUSION

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.

A Nucleotide Analog Prevents Colitis-Associated Cancer via Beta-Catenin Independently of Inflammation and Autophagy

BACKGROUND & AIMS

Chronic bowel inflammation increases the risk of colon cancer; colitis-associated cancer (CAC). Thiopurine treatments are associated with a reduction in dysplasia and CAC in inflammatory bowel disease (IBD). Abnormal Wnt/β-catenin signalling is characteristic of >90% of colorectal cancers. Immunosuppression by thiopurines is via Rac1 GTPase, which also affects Wnt/β-catenin signalling. Autophagy is implicated in colonic tumors, and topical delivery of the thiopurine thioguanine (TG) is known to alleviate colitis and augment autophagy. This study investigated the effects of TG in a murine model of CAC and potential mechanisms.

METHODS

Colonic dysplasia was induced by exposure to azoxymethane (AOM) and dextran sodium sulfate (DSS) in wild-type (WT) mice and mice harboring intestinal epithelial cell-specific deletion of autophagy related 7 gene (Atg7^ΔIEC). TG or vehicle was administered intrarectally, and the effect on tumor burden and β-catenin activity was assessed. The mechanisms of action of TG were investigated in vitro and in vivo.

RESULTS

TG ameliorated DSS colitis in wild-type but not Atg7^ΔIEC mice, demonstrating that anti-inflammatory effects of locally delivered TG are autophagy-dependent. However, TG inhibited CAC in both wild-type and Atg7^ΔIEC mice. This was associated with decreased β-catenin activation/nuclear translocation demonstrating that TG's inhibition of tumorigenesis occurred independently of anti-inflammatory and pro-autophagic actions. These results were confirmed in cell lines, and the dependency on Rac1 GTPase was demonstrated by siRNA knockdown and overexpression of constitutively active Rac1.

CONCLUSIONS

Our findings provide evidence for a new mechanism that could be exploited to improve CAC chemoprophylactic approaches.

Can We Predict the Toxicity and Response to Thiopurines in Inflammatory Bowel Diseases?

Thiopurines are a cheap, effective treatment option in the management of inflammatory bowel disease (IBD). However, with the growing choice of targeted therapies available, as well as the well-documented toxicities of thiopurines, the role of thiopurines has been questioned. Nevertheless, given their inexpense in an era of spiraling healthcare costs, thiopurines remain an attractive option in the right patients. In the age of personalized medicine, being able to predict patients who will respond as well as those that will develop toxicity to a treatment is vital to tailoring therapy. This review will summarize the available literature with respect to predictors of response and toxicity to thiopurines in order to guide management in IBD. Specifically, toxicities addressed will include myelotoxicity, hepatotoxicity, pancreatitis, alopecia, gastrointestinal and flu-like symptoms, and complications associated with Epstein-Barr virus. While more work needs to be done to further our ability to predict both response to and side effects from therapies, pharmacogenomic research shows significant promise in its ability to personalize our use of thiopurines.

Comparison of outcomes of continuation/discontinuation of 5-aminosalicylic acid after initiation of anti-tumor necrosis factor-alpha therapy in patients with inflammatory bowel disease

BACKGROUND

Few maintenance therapeutic options are available for inflammatory bowel disease (IBD). Data on the effects of continuing 5-aminosalicylic acid (5-ASA) treatment in patients who commence on biologics as maintenance treatment remain scarce. We evaluated IBD patient outcomes after continuation/discontinuation of 5-ASA when biologics were administered as maintenance treatment.

METHODS

We retrospectively reviewed the clinical, laboratory, and imaging data of patients diagnosed with IBD (ulcerative colitis (UC), 763; Crohn's disease (CD), 537) in the Gil Medical Center (GMC) from February 2005 to June 2018. We divided patients administered with biologics as maintenance treatment into those who did and did not continue on 5-ASA and compared the efficacies of the two treatment options using the log-rank test and Cox proportional hazards models.

RESULTS

Of 1300 total IBD patients, 128 (UC, 63; CD, 65) were prescribed biologics as induction and maintenance treatments. The median follow-up period was 109.5 weeks. All cases were divided into those who did or did not combine 5-ASA with biologics as maintenance treatments. Kaplan-Meier analysis showed that the event-free survival (exacerbation of disease activity) of UC patients treated with biologics and 5-ASA (n = 42) was not significantly lower than that of those taking biologics alone (n = 21) (log rank test, P = 0.68). The same was true of CD patients (n = 42, biologics and 5-ASA; n = 23, biologics only) (log rank test, P = 0.87).

CONCLUSIONS

Continuation of 5-ASA after initiation of anti-tumor necrosis factor-alpha agents did not improve prognosis in Korean IBD patients compared with that of those who discontinued 5-ASA during maintenance treatment, particularly in patients who experienced more than two disease aggravations.

Sustained effectiveness, safety and therapeutic drug monitoring of tioguanine in a cohort of 274 IBD patients intolerant for conventional therapies

BACKGROUND

Tioguanine (or thioguanine) is an alternative drug for IBD patients who fail prior conventional immunomodulating therapy.

AIM

To report effectiveness, safety and therapeutic drug monitoring in a cohort of patients with prolonged tioguanine maintenance therapy.

METHODS

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).

RESULTS

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/8×10⁸ RBC (P < 0.05).

CONCLUSIONS

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/8×10⁸ RBC is proposed as target level with higher odds for clinical effectiveness.

Off-label prescriptions of drugs used for the treatment of Crohn's disease or ulcerative colitis

BACKGROUND

Off-label prescribing is encountered across various fields of medicine and creates alternative treatment options, but is associated with unknown safety risks. The use of off-label drugs for the treatment of patients with inflammatory bowel diseases (IBD) has not been characterised before.

AIM

To assess the proportion and characteristics of off-label prescribing for IBD in tertiary care centres in the Netherlands.

METHODS

A prospective database of IBD patients from all Dutch university hospitals was used to collect data on drug prescriptions for IBD and demographics. Drugs were classified as off-label if they were unlicensed for Crohn's disease and/or ulcerative colitis by the Medicines Evaluation Board. Uni- and multivariable analyses were used to identify patient-specific characteristics predictive of increased off-label use.

RESULTS

For the induction and/or maintenance treatment of 4583 IBD patients, 12 651 historical and current drug records were available in the database. Of these, 2374 (19%) were considered off-label prescriptions. Out of 4583 IBD patients, 1477 (32%) were exposed to off-label drugs. Commonly prescribed off-label IBD drugs were mercaptopurine (18%), beclomethasone (12%), thioguanine (4%) and allopurinol (3%). Non-thiopurine/methotrexate off-label drugs were prescribed in 243 patients (6%), including biological agents or tofacitinib in 47 IBD patients (1%). Off-label prescriptions were more common in ulcerative colitis than Crohn's disease (37% vs 29%, P < 0.001). Smokers and patients that received ≥5 drug types during their disease course were more likely to be exposed to off-label drugs (smoking 33% vs 27% and multiple drug use 66% vs 22%, both P < 0.001).

CONCLUSION

About one-fifth of prescriptions for IBD were off-label and one-third of IBD patients, especially ulcerative colitis patients, were exposed to off-label drugs.