Long term efficacy and safety of allopurinol and azathioprine or 6-mercaptopurine in patients with inflammatory bowel disease

Long-term safety and effectiveness of azathioprine in the management of inflammatory bowel disease: A real-world experience

Background and Aim

Azathioprine (AZA) forms the cornerstone for maintenance of sustained remission in inflammatory bowel disease (IBD). There is apprehension regarding the long-term effectiveness and safety of AZA in IBD. We present our experience with AZA use and outcomes in a cohort of IBD patients followed up over a long period of time.

Methods

Records of 507 IBD patients under treatment at a single, tertiary care center in south India between 2013 and 2022 were evaluated retrospectively. Long-term compliance, tolerance, clinical outcome at the point of last follow-up, type and duration to the onset of adverse events, and subsequent amendment to treatment with regard to AZA were analyzed.

Results

Of 507 patients with IBD, 320 patients (207 Crohn's disease [CD], 113 ulcerative colitis [UC]) who received AZA were included. The median follow-up was 41 months (interquartile range 15.5-77.5). Total duration of exposure was 1359 patient-years with median usage of 33 months. Of the patients, 26.9% received AZA for >5 years. Mean initiation and maximum doses of AZA were 0.97 and 1.72 mg/kg/day. Among the participants, 20.6% experienced side effects, including myelotoxicity (7.2%) and gastrointestinal intolerance (5.6%). Six patients developed malignancy. Among the side effects, 39.4% of side effects were dose-dependent. Among the patients, 38.1% had relapses requiring pulse corticosteroid therapy, and 16.2% had more than one relapse after commencement of AZA. AZA was continued till the last follow-up in 76.5%. Among the patients, 49.7% (UC 51.3, CD 48.8) attained durable remission without biologics, and 5.3% continued to have active disease.

Conclusion

AZA is safe and effective in the long-term in IBD. Effectiveness, tolerance, and compliance with AZA are well sustained beyond 5 years of usage and comparable between UC and CD.

Low-dose azathioprine and allopurinol versus azathioprine monotherapy in patients with ulcerative colitis (AAUC): An investigator-initiated, open, multicenter, parallel-arm, randomised controlled trial

BACKGROUND

Retrospective studies suggest that for patients with ulcerative colitis (UC) combination therapy with low-dose azathioprine and allopurinol (L-AZA/ALLO) may result in higher remission rates than monotherapy with azathioprine (AZA). We prospectively investigated the effects of these drugs for remission in patients with moderate-to-severe UC.

METHODS

Open-label, unblinded, randomised, controlled, investigator-initiated, multicentre study conducted at eight hospital sites in Denmark. Adult patients with established UC, who were steroid dependent/refractory, thiopurine naïve, had a normal thiopurine methyltransferase, and achieved remission with steroids or infliximab were eligible for inclusion. Patients were randomly assigned by the investigators (1:1) to 52 weeks of treatment with once daily oral AZA (median dose 50 mg) combined with ALLO 100 mg versus AZA monotherapy (median dose 200 mg), using a computer-generated randomisation list with blocks of six. The trial was open without masking. All randomised patients who received at least one dose of study drug were included in primary and safety analyses (intention to treat population). The primary outcome was steroid and infliximab free remission after 52 weeks, defined as a Mayo Score of ≤1 and no rectal bleeding. The trial is completed and is registered in ClinicalTrials.gov (ClinicalTrials.gov NCT03101800).

FINDINGS

Between January 9, 2017 and February 10, 2021, 47 patients were randomised to l-AZA/ALLO and 42 to AZA and received at least one dose of the study drug. After 52 weeks, 20 of 47 (43%) patients in the l-AZA/ALLO group and nine of 42 (21%) patients in the AZA group achieved remission (odds ratio 2·54 [95% CI 1·00 to 6.78, p < 0·048]). Fourteen patients (30%) in the l-AZA/ALLO group and 16 (38%) in the AZA group were withdrawn from the study due to adverse events.

INTERPRETATION

This study suggests that after one year l-AZA/ALLO therapy may be associated with a beneficial effect on steroid- and infliximab-free clinical remission in patients with moderate-to-severe UC and should be considered as first line therapy.

FUNDING

Funding for AAUC was provided by The Capital Region of Denmark (Regionernes Medicinpulje (6062/16)).

Azathioprine with Allopurinol Is a Promising First-Line Therapy for Inflammatory Bowel Diseases

BACKGROUND

Beneficial response to first-line immunosuppressive azathioprine in patients with inflammatory bowel disease (IBD) is low due to high rates of adverse events. Co-administrating allopurinol has been shown to improve tolerability. However, data on this co-therapy as first-line treatment are scarce.

AIM

Retrospective comparison of long-term effectiveness and safety of first-line low-dose azathioprine-allopurinol co-therapy (LDAA) with first-line azathioprine monotherapy (AZAm) in patients with IBD without metabolite monitoring.

METHODS

Clinical benefit was defined as ongoing therapy without initiation of steroids, biologics or surgery. Secondary outcomes included CRP, HBI/SCCAI, steroid withdrawal and adverse events.

RESULTS

In total, 166 LDAA and 118 AZAm patients (median follow-up 25 and 27 months) were evaluated. Clinical benefit was more frequently observed in LDAA patients at 6 months (74% vs. 53%, p = 0.0003), 12 months (54% vs. 37%, p = 0.01) and in the long-term (median 36 months; 37% vs. 24%, p = 0.04). Throughout follow-up, AZAm patients were 60% more likely to fail therapy, due to a higher intolerance rate (45% vs. 26%, p = 0.001). Only 73% of the effective AZA dose was tolerated in AZAm patients, while LDAA could be initiated and maintained at its target dose. Incidence of myelotoxicity and elevated liver enzymes was similar in both cohorts, and both conditions led to LDAA withdrawal in only 2%. Increasing allopurinol from 100 to 200-300 mg/day significantly lowered liver enzymes in 5/6 LDAA patients with hepatotoxicity.

CONCLUSIONS

Our poor AZAm outcomes emphasize that optimization of azathioprine is needed. We demonstrated a long-term safe and more effective profile of first-line LDAA. This co-therapy may therefore be considered standard first-line immunosuppressive.

Optimizing Thiopurine Therapy with a Xanthine Oxidase Inhibitor in Patients with Systemic Autoimmune Diseases: A Single-Centre Experience

Background

Thiopurines are a mainstay of therapy for autoimmune diseases. However, up to 20% to 30% of patients experience overproduction of the methylated metabolites, known as 6-MMP, to the detriment of the active metabolite, 6-thioguanine nucleotide (6-TGN). These patients, commonly referred to as "shunters", are predisposed to thiopurine resistance and hepatotoxicity. In patients with inflammatory bowel diseases, the combination of thiopurine with a xanthine oxidase inhibitor (XOI) is used to reverse this skewed metabolism and to prevent treatment failure or hepatotoxicity. Data on the use of this strategy for patients with other diseases are limited.

Objectives

To investigate and describe the use of thiopurine-XOI combination therapy in shunters with systemic autoimmune diseases.

Methods

Shunters treated in the study hospital between January 1, 2005, and December 31, 2015, were identified using the hospital's laboratory database, and clinical data were collected retrospectively. For each patient with optimization of thiopurine therapy, clinical and laboratory data were assessed over a 6-month period.

Results

Thirty-four patients were identified as shunters; for 14 of these patients, thiopurine therapy was optimized with an XOI. In these 14 patients, the median dose of azathioprine was reduced from 1.95 to 0.78 mg/kg with combination therapy. In addition, median 6-TGN level increased from 135 to 385 pmol/8 × 10⁸ erythrocytes (p = 0.001); furthermore, 6-TGN levels rose to above 235 pmol/8 ×10⁸ erythrocytes for 11 of the 14 patients. Conversely, the median 6-MMP level decreased from 6267 to 271 pmol/8 × 10⁸ erythrocytes (p = 0.001). Except for a 12% increase in mean corpuscular volume, no clinically significant changes in blood count were recorded. Notable infections were reported in 3 patients, and 1 patient had to discontinue treatment because of cytopenia. After 6 months, median prednisone daily dose was reduced by 74%, from 16.7 mg to 4.4 mg (p = 0.005), and 4 patients had been weaned off corticosteroids. Of the 14 patients, 11 (79%) were in full remission, and 2 (14%) were in partial remission.

Conclusion

Optimizing thiopurine therapy with an XOI may be a safe and effective strategy for patients with systemic autoimmune diseases.

Influence of allopurinol on thiopurine associated toxicity: A retrospective population-based cohort study

Aims

Thiopurines are important for treating inflammatory bowel disease, but are often discontinued due to adverse effects. Concomitant use of allopurinol might lower the risk of these unwanted effects, but large studies in the general population are lacking. The aims of this study were to evaluate rates of hepatotoxicity, myelotoxicity, pancreas toxicity and therapy persistence in adult thiopurine users with or without allopurinol.

Methods

A retrospective population‐based cohort study was conducted within current thiopurine users (Clinical Practice Research Datalink). Among these patients, co‐use of allopurinol was compared to non‐use. Hazard ratios (HRs) for hepatotoxicity, myelotoxicity and pancreatitis were derived using time‐dependent Cox proportional hazards models, and were adjusted for potential confounders. Persistence of thiopurine use was evaluated using Log‐rank statistics.

Results

Patients using thiopurines (n = 37 360) were identified of which 1077 were concomitantly taking allopurinol. A 58% decreased risk of hepatotoxicity was observed in those concomitantly taking allopurinol (HR 0.42; 95% CI 0.30–0.60; NNT 46). Rate of myelotoxicity (HR 0.96; 95% CI 0.89–1.03) was not influenced. Risk of pancreatitis was increased (HR 3.00; 95% CI 1.01–8.93; NNH 337), but was only seen in those with active gout (suggesting confounding by indication). Finally, allopurinol co‐users were able to maintain thiopurine therapy over twice as long as those not on allopurinol (3.9 years vs. 1.8 years, P < 0.0001).

Conclusion

In thiopurine users, allopurinol is associated with a 58% reduced risk of hepatotoxicity. In addition, thiopurine persistence was prolonged by 2.1 years in allopurinol users. These data support the use of allopurinol in individuals requiring thiopurine therapy.

Biomarkers Predictive of Response to Thiopurine Therapy in Inflammatory Bowel Disease

The complex nature of inflammatory bowel disease (IBD) often results in treatment failure for many patients. With some patients cycling through multiple therapies before achieving a sustained period of remission, the ability to predict a patient's response to therapeutics could decrease the time from active disease to clinical remission and mucosal healing. The prospect of such individualized treatment of IBD would be aided by accurate biomarkers, both fecal and serological, which have to date shown value as indicators of IBD activity. Here we review the utility of generic biomarkers for inflammation or mucosal healing, such as calprotectin, C-reactive protein (CRP), and fecal hemoglobin (fHb) as predictors of response to treatment of IBD. We further provide a deeper insight into the utility of monitoring the thiopurine treatment by thiopurine metabolites or alternative hematologic parameters. In light of multiple recent publications of biomarkers and biological therapy, our focus in this review is predicting response to thiopurine treatment only, that is, Azathioprine and 6-Mercaptopurine.

British Society of Gastroenterology consensus guidelines on the management of inflammatory bowel disease in adults

Ulcerative colitis and Crohn's disease are the principal forms of inflammatory bowel disease. Both represent chronic inflammation of the gastrointestinal tract, which displays heterogeneity in inflammatory and symptomatic burden between patients and within individuals over time. Optimal management relies on understanding and tailoring evidence-based interventions by clinicians in partnership with patients. This guideline for management of inflammatory bowel disease in adults over 16 years of age was developed by Stakeholders representing UK physicians (British Society of Gastroenterology), surgeons (Association of Coloproctology of Great Britain and Ireland), specialist nurses (Royal College of Nursing), paediatricians (British Society of Paediatric Gastroenterology, Hepatology and Nutrition), dietitians (British Dietetic Association), radiologists (British Society of Gastrointestinal and Abdominal Radiology), general practitioners (Primary Care Society for Gastroenterology) and patients (Crohn's and Colitis UK). A systematic review of 88 247 publications and a Delphi consensus process involving 81 multidisciplinary clinicians and patients was undertaken to develop 168 evidence- and expert opinion-based recommendations for pharmacological, non-pharmacological and surgical interventions, as well as optimal service delivery in the management of both ulcerative colitis and Crohn's disease. Comprehensive up-to-date guidance is provided regarding indications for, initiation and monitoring of immunosuppressive therapies, nutrition interventions, pre-, peri- and postoperative management, as well as structure and function of the multidisciplinary team and integration between primary and secondary care. Twenty research priorities to inform future clinical management are presented, alongside objective measurement of priority importance, determined by 2379 electronic survey responses from individuals living with ulcerative colitis and Crohn's disease, including patients, their families and friends.

British Society of Gastroenterology consensus guidelines on the management of inflammatory bowel disease in adults

Ulcerative colitis and Crohn's disease are the principal forms of inflammatory bowel disease. Both represent chronic inflammation of the gastrointestinal tract, which displays heterogeneity in inflammatory and symptomatic burden between patients and within individuals over time. Optimal management relies on understanding and tailoring evidence-based interventions by clinicians in partnership with patients. This guideline for management of inflammatory bowel disease in adults over 16 years of age was developed by Stakeholders representing UK physicians (British Society of Gastroenterology), surgeons (Association of Coloproctology of Great Britain and Ireland), specialist nurses (Royal College of Nursing), paediatricians (British Society of Paediatric Gastroenterology, Hepatology and Nutrition), dietitians (British Dietetic Association), radiologists (British Society of Gastrointestinal and Abdominal Radiology), general practitioners (Primary Care Society for Gastroenterology) and patients (Crohn's and Colitis UK). A systematic review of 88 247 publications and a Delphi consensus process involving 81 multidisciplinary clinicians and patients was undertaken to develop 168 evidence- and expert opinion-based recommendations for pharmacological, non-pharmacological and surgical interventions, as well as optimal service delivery in the management of both ulcerative colitis and Crohn's disease. Comprehensive up-to-date guidance is provided regarding indications for, initiation and monitoring of immunosuppressive therapies, nutrition interventions, pre-, peri- and postoperative management, as well as structure and function of the multidisciplinary team and integration between primary and secondary care. Twenty research priorities to inform future clinical management are presented, alongside objective measurement of priority importance, determined by 2379 electronic survey responses from individuals living with ulcerative colitis and Crohn's disease, including patients, their families and friends.

[Hepatobiliary Manifestation of Inflammatory Bowel Disease]

The hepatobiliary system is one of the most common sites of extraintestinal manifestation in patients with inflammatory bowel disease (IBD). The progression of IBD can lead to a primary hepatobiliary manifestation and can occur secondary to multiple drugs or accompanying viral infections. Primary sclerosing cholangitis is the representative hepatobiliary manifestation of IBD, particularly in ulcerative colitis. Although most agents used in the treatment of IBD are potentially hepatotoxic, the risk of serious hepatitis or liver failure is low. The prevalence of HBV and HCV in IBD is similar to the general population, but the clinical concern is HBV reactivation associated with immunosuppressive therapy. Patients undergoing cytotoxic chemotherapy or immunosuppressive therapy with a moderate to high risk of HBV reactivation require prophylactic antiviral therapy. On the other hand, HCV has little risk of reactivation. Patients with IBD are more likely to have nonalcoholic fatty liver disease than the general population and tend to occur at younger ages. IBD and cholelithiasis are closely related, especially in Crohn's disease.

Nonsynonymous Polymorphism in Guanine Monophosphate Synthetase Is a Risk Factor for Unfavorable Thiopurine Metabolite Ratios in Patients With Inflammatory Bowel Disease

BACKGROUND

Up to 20% of patients with inflammatory bowel disease (IBD) who are refractory to thiopurine therapy preferentially produce 6-methylmercaptopurine (6-MMP) at the expense of 6-thioguanine nucleotides (6-TGN), resulting in a high 6-MMP:6-TGN ratio (>20). The objective of this study was to evaluate whether genetic variability in guanine monophosphate synthetase (GMPS) contributes to preferential 6-MMP metabolizer phenotype.

METHODS

Exome sequencing was performed in a cohort of IBD patients with 6-MMP:6-TGN ratios of >100 to identify nonsynonymous single nucleotide polymorphisms (nsSNPs). In vitro assays were performed to measure GMPS activity associated with these nsSNPs. Frequency of the nsSNPs was measured in a cohort of 530 Caucasian IBD patients.

RESULTS

Two nsSNPs in GMPS (rs747629729, rs61750370) were detected in 11 patients with very high 6-MMP:6-TGN ratios. The 2 nsSNPs were predicted to be damaging by in silico analysis. In vitro assays demonstrated that both nsSNPs resulted in a significant reduction in GMPS activity (P < 0.05). The SNP rs61750370 was significantly associated with 6-MMP:6-TGN ratios ≥100 (odds ratio, 5.64; 95% confidence interval, 1.01-25.12; P < 0.031) in a subset of 264 Caucasian IBD patients.

CONCLUSIONS

The GMPS SNP rs61750370 may be a reliable risk factor for extreme 6MMP preferential metabolism.

Revisiting the Role of Thiopurines in Inflammatory Bowel Disease Through Pharmacogenomics and Use of Novel Methods for Therapeutic Drug Monitoring

Azathioprine and 6-mercaptopurine, often referred to as thiopurine compounds, are commonly used in the management of inflammatory bowel disease. However, patients receiving these drugs are prone to developing adverse drug reactions or therapeutic resistance. Achieving predefined levels of two major thiopurine metabolites, 6-thioguanine nucleotides and 6-methylmercaptopurine, is a long-standing clinical practice in ensuring therapeutic efficacy; however, their correlation with treatment response is sometimes unclear. Various genetic markers have also been used to aid the identification of patients who are thiopurine-sensitive or refractory. The recent discovery of novel Asian-specific DNA variants, namely those in the NUDT15 gene, and their link to thiopurine toxicity, have led clinicians and scientists to revisit the utility of Caucasian biomarkers for Asian individuals with inflammatory bowel disease. In this review, we explore the limitations associated with the current methods used for therapeutic monitoring of thiopurine metabolites and how the recent discovery of ethnicity-specific genetic markers can complement thiopurine metabolites measurement in formulating a strategy for more accurate prediction of thiopurine response. We also discuss the challenges in thiopurine therapy, alongside the current strategies used in patients with reduced thiopurine response. The review is concluded with suggestions for future work aiming at using a more comprehensive approach to optimize the efficacy of thiopurine compounds in inflammatory bowel disease.

Thiopurines in Inflammatory Bowel Disease: New Findings and Perspectives

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.

Randomised clinical trial: efficacy, safety and dosage of adjunctive allopurinol in azathioprine/mercaptopurine nonresponders (AAA Study)

BACKGROUND

Thiopurine hypermethylation towards 6-methylmercaptopurine (6MMP) instead of 6-thioguanine nucleotides (6TGN) is associated with inefficacy in patients with IBD. Allopurinol reverses such hypermethylation.

AIMS

To prospectively determine efficacy of allopurinol-thiopurine combination and to compare 2 doses of allopurinol.

DESIGN

In a multicentre, double-blind trial, patients with clinically active or steroid-dependent IBD and thiopurine shunting were randomised to 50 or 100 mg/d allopurinol and 25% of their screening thiopurine dose, which was subsequently optimised, aiming for 6TGN of 260-500 pmol/8x10⁸ RBCs. The primary endpoint was steroid-free clinical remission at 24 weeks.

RESULTS

Of 73 patients, 39 (53% [95% CI 42-65]) achieved steroid-free remission, (54% with 50 mg/d and 53% with 100 mg/d). 81% were able to discontinue steroids. Therapeutic 6TGN levels were achieved in both groups. Final thiopurine doses were lower with 100 mg/d allopurinol (P < 0.005). 6MMP: 6TGN ratio decreased from mean 64 to 4 (P < 0.001), being higher with 50 mg/d (6 ± 1.83) than for 100 mg/d ([1 ± 0.16], P = 0.003). Three patients on 50 mg/d failed to sustain low ratios at 24 weeks. Toxicity was minimal; three patients on 50 mg/d allopurinol developed transient leukopenia. Alanine aminotransferase concentrations decreased (P < 0.001) similarly in both arms. Faecal calprotectin levels at study end were lower in patients who achieved the primary endpoint (median 171 [85-541] vs 821[110-5892] ug/g, P = 0.03).

CONCLUSIONS

Low-dose allopurinol-thiopurine combination safely reverses shunting and optimises 6TGN with associated improvement in disease activity. 100 mg/d allopurinol is preferable due to greater metabolite profile stability and lower thiopurine dose without additional toxicity.

Addition of Allopurinol for Altering Thiopurine Metabolism to Optimize Therapy in Patients with Inflammatory Bowel Disease

Thiopurine drugs, including azathioprine and 6-mercaptopurine, are used commonly in patients with inflammatory bowel disease for maintenance of remission. Although generally well tolerated, adverse effects lead to discontinuation in a significant minority of patients. Pharmacogenomic studies have suggested that metabolic breakdown of azathioprine in an individual is genetically determined. Coupled with the fact that certain thiopurine metabolites, notably 6-thioguanine nucleotide and 6-methylmercaptopurine, are associated with antiinflammatory effects and adverse effects, respectively, some investigators have examined intentionally shunting the metabolism of azathioprine toward increasing 6-thioguanine nucleotide levels by using low doses of the xanthine oxidoreductase inhibitor allopurinol to improve efficacy and decrease toxicity of azathioprine in patients with inflammatory bowel disease. We performed a search of the MEDLINE and Embase databases for basic and clinical research reports of this modality. Pertinent articles were retrieved, reviewed, and assessed by the authors. Case series, cohort studies, and one randomized trial have investigated adding allopurinol to azathioprine therapy in patients with inflammatory bowel disease. Most reports primarily examined metabolite levels in these patients. In general, the literature suggests that this modality was successful at significantly increasing 6-thioguanine nucleotide levels while decreasing 6-methylmercaptopurine levels. Several small reports have suggested that patients with increased 6-thioguanine nucleotide levels had improved symptoms or symptom remission. Adverse effects and discontinuation rates remained similar or were improved in patients who were taking a thiopurine and started allopurinol. In conclusion, the addition of allopurinol may be an option for optimizing thiopurine metabolite production in select patients with low 6-thioguanine nucleotide levels. Appropriate care and monitoring of these patients are mandatory to prevent neutropenia or other adverse effects.

Transient elastography to assess liver stiffness in patients with inflammatory bowel disease

BACKGROUND

Liver injury during inflammatory bowel disease (IBD) is primarily diagnosed by liver biopsy, which has a small but serious risk of severe complications. The aim of this study was to assess liver stiffness, and subsequently the prevalence and associations of liver fibrosis in IBD patients with thiopurine therapy and other clinical factors, by using transient elastography (TE).

METHODS

In this prospective, international two-center study, included IBD-patients underwent TE measurements. Laboratory results and medication reports, radiology results and historical liver biopsy results were extracted from the patient charts.

RESULTS

Transient elastography results of 168 patients were presented. Moderate and severe fibrosis were detected in 4% (7/168) and 1% (1/168) of the cohort, respectively. Factors contributing to lower liver stiffness were female gender and (historical) exposure to azathioprine. Further, there was a statistical trend towards lower liver stiffness in patients using thiopurines overall (4.7 vs. 5.2kPa, p=0.07). Liver stiffness correlated positively with waist circumference, liver enzyme tests, hemoglobin and 6-methylmercaptopurine concentration and negatively with platelet count.

CONCLUSION

Exposure to thiopurine therapy was not associated with higher liver stiffness, although no clinical difference in severity of fibrosis was detected. Further research should robustly determine the accuracy of TE as an evaluation of liver fibrosis in IBD patients.

Optimizing Thiopurine Therapy in Inflammatory Bowel Disease Among 2 Real-life Intercept Cohorts: Effect of Allopurinol Comedication?

BACKGROUND

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.

METHODS

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.

RESULTS

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).

CONCLUSIONS

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.

Allopurinol in combination with thiopurine induces mucosal healing and improves clinical and metabolic outcomes in IBD

BACKGROUND

Thiopurines, azathioprine (AZA) and 6-mercaptopurine (6-MP) are common maintenance medications for inflammatory bowel disease (IBD). Excessive methylation via thiopurine methyltransferase (TPMT) frequently causes therapeutic failure. Allopurinol reduces excessive 6-methyl-mercaptopurine (6-MMP) while enhancing 6-thioguanine (6-TGN) levels. The aim of this study was to evaluate clinical, metabolic and endoscopic impact of allopurinol in combination with low-dose thiopurine in IBD.

METHODS

Retrospective review of consecutive cases treated with allopurinol. Metabolites and their ratios (6-MMP/6-TGN) were compared pre- and post-allopurinol. Clinical and endoscopic remission were assessed.

RESULTS

Allopurinol (n = 66) reduced mean dose of AZA by 70% (p < 0.01). Baseline levels (SD) 6-TGN, 6-MMP and 6-MMP/6-TGN were 165 (64), 9388 (5234) and 59.8 (30.3), respectively. These values improved on allopurinol to 297 (102), 896 (1031) and 3.4 (4.0), respectively (p < 0.0001). Therapeutic 6-TGN level (>235) was achieved in 49/58 cases on allopurinol combination therapy, versus 9/58 monotherapy (p = 0.0001). Among the thiopurine failure group (40 patients), clinical remission or response was observed in 65% and 22% of patients, respectively. In the asymptomatic group with excessive 6-MMP, 11/14 achieved sustained remission on allopurinol. Repeat colonoscopy (n = 28) showed mostly endoscopic remission (67.9%) or improvement (17.8%). Few had unimproved lesions (14.3%). Importantly, 46% of cases had complete mucosal healing. Two patients had cancer on combination therapy (de novo pancreatic cancer and fatal recurrence of metastatic testicular cancer). Elevated transaminases were reduced on allopurinol (48.2 versus 6.9%) (p < 0.001); no change in leukopenic or infectious events occurred.

CONCLUSION

Allopurinol in combination with low-dose thiopurine corrected excessive 6-MMP levels, resulting in clinical remission and mucosal healing in the majority of cases. The potential cancer risk of allopurinol and thiopurine combination therapy needs further research.

Time to clinical response and remission for therapeutics in inflammatory bowel diseases: What should the clinician expect, what should patients be told?

An awareness of the expected time for therapies to induce symptomatic improvement and remission is necessary for determining the timing of follow-up, disease (re)assessment, and the duration to persist with therapies, yet this is seldom reported as an outcome in clinical trials. In this review, we explore the time to clinical response and remission of current therapies for inflammatory bowel disease (IBD) as well as medication, patient and disease related factors that may influence the time to clinical response. It appears that the time to therapeutic response varies depending on the indication for therapy (Crohn's disease or ulcerative colitis). Agents with the most rapid time to clinical response included corticosteroids, calcineurin inhibitors, exclusive enteral nutrition, aminosalicylates and anti-tumor necrosis factor therapy which will work in most patients within the first 2 mo. Vedolizumab, methotrexate and thiopurines had a longer time to clinical response and can take several months to achieve maximal efficacy. Factors affecting the time to clinical response of therapies included use of concomitant therapy, disease duration, smoking status, disease phenotype and advanced age. There appears to be marked variation in time to clinical response for therapies used in IBD which is further influenced by disease and patient related factors. Understanding the expected time to therapeutic response is integral to inform further decision making, maintain a patient-centered approach and ensure treatment is given an appropriate timeframe to achieve maximal benefit prior to cessation.

Combination treatment with 6-mercaptopurine and allopurinol in HepG2 and HEK293 cells - Effects on gene expression levels and thiopurine metabolism

Combination treatment with low-dose thiopurine and allopurinol (AP) has successfully been used in patients with inflammatory bowel disease with a so called skewed thiopurine metabolite profile. In red blood cells in vivo, it reduces the concentration of methylated metabolites and increases the concentration of the phosphorylated ones, which is associated with improved therapeutic efficacy. This study aimed to investigate the largely unknown mechanism of AP on thiopurine metabolism in cells with an active thiopurine metabolic pathway using HepG2 and HEK293 cells. Cells were treated with 6-mercaptopurine (6MP) and AP or its metabolite oxypurinol. The expression of genes known to be associated with thiopurine metabolism, and the concentration of thiopurine metabolites were analyzed. Gene expression levels were only affected by AP in the presence of 6MP. The addition of AP to 6MP affected the expression of in total 19 genes in the two cell lines. In both cell lines the expression of the transporter SLC29A2 was reduced by the combined treatment. Six regulated genes in HepG2 cells and 8 regulated genes in HEK293 cells were connected to networks with 18 and 35 genes, respectively, present at known susceptibility loci for inflammatory bowel disease, when analyzed using a protein-protein interaction database. The genes identified as regulated as well as the disease associated interacting genes represent new candidates for further investigation in the context of combination therapy with thiopurines and AP. However, no differences in absolute metabolite concentrations were observed between 6MP+AP or 6MP+oxypurinol vs. 6MP alone in either of the two cell lines. In conclusion; the effect of AP on gene expression levels requires the presence of 6MP, at least in vitro. Previously described AP-effects on metabolite concentrations observed in red blood cells in vivo could not be reproduced in our cell lines in vitro. AP’s effects in relation to thiopurine metabolism are complex. The network-identified susceptibility genes represented biological processes mainly associated with purine nucleotide biosynthetic processes, lymphocyte proliferation, NF-KB activation, JAK-STAT signaling, and apoptotic signaling at oxidative stress.

Randomized clinical trial: a pilot study comparing efficacy of low-dose azathioprine and allopurinol to azathioprine on clinical outcomes in inflammatory bowel disease

BACKGROUND

Treating inflammatory bowel diseases (IBD) using thiopurines is effective; however, a high rate of adverse effects and lack of efficacy limit its use. Retrospective studies have suggested that treatment with low-dose thiopurines in combination with allopurinol is associated with higher remission rates and lower incidence of adverse events.

AIM

To compare the rates of clinical remission and the rates of adverse events in IBD patients treated with either standard treatment with azathioprine or low-dose azathioprine in combination with allopurinol.

METHODS

A prospective, open-label study, randomizing thiopurine-naïve IBD patients with normal thiopurine methyltransferase to 24 weeks of treatment with either standard azathioprine dose or low-dose azathioprine and allopurinol.

RESULTS

A total of 46 patients with ulcerative colitis or Crohn's disease were randomized. We conducted an intention to treat analysis and found a significant (69.6%) proportion of the patients treated with low-dose azathioprine in combination with allopurinol was in clinical remission without the need for steroid or biologic treatment at week 24 compared to 34.7% of the patients treated with azathioprine monotherapy (RR, 2.10 [95% CI: 1.07-4.11]). In the azathioprine group, 47.8% of the patients compared to 30.4% of the patients in the azathioprine-allopurinol group had to withdraw from the study due to adverse events (RR, 1.47 [95% CI: 0.76-2.85]) Conclusions: This study indicated that by changing the treatment strategy from standard weight-based dosing of azathioprine to weight-based low-dose azathioprine in combination with allopurinol, we can increase remission rates in patients with IBD.

Pharmacology and Optimization of Thiopurines and Methotrexate in Inflammatory Bowel Disease

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.

Review article: acute severe ulcerative colitis - evidence-based consensus statements

BACKGROUND

Acute severe ulcerative colitis (ASUC) is a potentially life-threatening complication of ulcerative colitis.

AIM

To develop consensus statements based on a systematic review of the literature of the management of ASUC to improve patient outcome.

METHODS

Following a literature review, the Delphi method was used to develop the consensus statements. A steering committee, based in Australia, generated the statements of interest. Three rounds of anonymous voting were carried out to achieve the final results. Acceptance of statements was pre-determined by ≥80% votes in 'complete agreement' or 'agreement with minor reservation'.

RESULTS

Key recommendations include that patients with ASUC should be: hospitalised, undergo unprepared flexible sigmoidoscopy to assess severity and to exclude cytomegalovirus colitis, and be provided with venous thromboembolism prophylaxis and intravenous hydrocortisone 100 mg three or four times daily with close monitoring by a multidisciplinary team. Rescue therapy such as infliximab or ciclosporin should be started if insufficient response by day 3, and colectomy considered if no response to 7 days of rescue therapy or earlier if deterioration. With such an approach, it is expected that colectomy rate during admission will be below 30% and mortality less than 1% in specialist centres.

CONCLUSION

These evidenced-based consensus statements on acute severe ulcerative colitis, developed by a multidisciplinary group, provide up-to-date best practice recommendations that improve and harmonise management as well as provide auditable quality assessments.

Review article: recent advances in pharmacogenetics and pharmacokinetics for safe and effective thiopurine therapy in inflammatory bowel disease

BACKGROUND

Azathioprine and mercaptopurine have a pivotal role in the treatment of inflammatory bowel disease (IBD). However, because of their complex metabolism and potential toxicities, optimal use of biomarkers to predict adverse effects and therapeutic response is paramount.

AIM

To provide a comprehensive review focused on pharmacogenetics and pharmacokinetics for safe and effective thiopurine therapy in IBD.

METHODS

A literature search up to July 2015 was performed in PubMed using a combination of relevant MeSH terms.

RESULTS

Pre-treatment thiopurine S-methyltransferase typing plus measurement of 6-tioguanine nucleotides and 6-methylmercaptopurine ribonucleotides levels during treatment have emerged with key roles in facilitating safe and effective thiopurine therapy. Optimal use of these tools has been shown to reduce the risk of adverse effects by 3-7%, and to improve efficacy by 15-30%. For the introduction of aldehyde oxidase (AOX) into clinical practice, the association between AOX activity and AZA dose requirements should be positively confirmed. Inosine triphosphatase assessment associated with adverse effects also shows promise. Nucleoside diphosphate-linked moiety X-type motif 15 variants have been shown to predict myelotoxicity on thiopurines in East Asian patients. However, the impact of assessments of xanthine oxidase, glutathione S-transferase, hypoxanthine guanine phosphoribosyltransferase and inosine monophosphate dehydrogenase appears too low to favour incorporation into clinical practice.

CONCLUSIONS

Measurement of thiopurine-related enzymes and metabolites reduces the risk of adverse effects and improves efficacy, and should be considered part of standard management. However, this approach will not predict or avoid all adverse effects, and careful clinical and laboratory monitoring of patients receiving thiopurines remains essential.

Allopurinol Use During Maintenance Therapy for Acute Lymphoblastic Leukemia Avoids Mercaptopurine-related Hepatotoxicity

6-Mercaptopurine (6-MP) is the mainstay of treatment for acute lymphoblastic leukemia and lymphoblastic lymphoma. It is metabolized into the pharmacologically active, 6-thioguanine nucleotide (6-TGN), and 6-methyl mercaptopurine nucleotides (6-MMPN), which is associated with hepatotoxicity that jeopardizes antileukemic therapy. Allopurinol alters the metabolism of 6-MP to increase 6-TGN levels and decreases 6-methyl mercaptopurine nucleotides levels. We report 2 cases in which combination therapy of allopurinol with 6-MP was used successfully to avoid hepatotoxicity while delivering adequate 6-TGN levels. We suggest that this combination therapy can be used safely to change the metabolite production in patients who develop excessive hepatotoxicity.

Optimizing the use of thiopurines in inflammatory bowel disease

Immunomodulator drugs, of which thiopurines can be considered the backbone, are widely used in the treatment of inflammatory bowel disease. They have been shown to be highly effective and safe; however, a significant proportion of patients are deemed to have a poor response or suffer adverse reactions. Knowing how to monitor and optimize thiopurine therapy in these scenarios is crucial to effective management. We discuss the metabolism of thiopurines, the use of enzyme/metabolite testing to guide treatment, as well as strategies to circumvent toxicity and side effects, such as allopurinol coprescription. The indications, use in pregnancy, safety profile and duration of thiopurine therapy are also discussed.

Anti-TNF levels and anti-drug antibodies, immunosuppressants and clinical outcomes in inflammatory bowel disease

The anti-tumor necrosis factor-α (TNF) antibodies have revolutionized the management of ulcerative colitis and Crohn's disease. The development of assays to allow for the measurements of serum drug levels and anti-drug antibodies have provided a more objective means of therapeutic decision making, particularly among patients losing response to treatment. Additionally, more evidence is emerging that indicates the relationship between drug levels and response to therapy including clinical response, mucosal healing and sustained remission. The use of combination therapies of the anti-TNF agents and the thiopurine immunosuppressants may also decrease immunogenicity to the anti-TNF agents and potentiate response to therapy. With more evidence emerging evidence of the importance of therapeutic drug levels and anti-drug antibodies, clinicians may be able to better optimize the current arsenal of inflammatory bowel disease therapeutics to achieve greater rates of durable remission and improved quality of life.

A practical guide to the use of thiopurines in oral medicine

Thiopurines are widely used as first-line immunosuppressive therapies in the management of chronic inflammatory oral disease. However, despite over half a century of clinical experience, the evidence base for their use is limited. The aims of this paper were to review the evidence for the use of thiopurines in oral medicine and provide a contemporary model of thiopurine metabolism and mechanism of action and a rationale for clinical use and safe practice.

The role of thiopurine metabolites in inflammatory bowel disease and rheumatological disorders

Thiopurines have been a cornerstone of medical management of patients with inflammatory bowel disease(IBD) and many rheumatological disorders. The thiopurines are metabolized to their end products, 6-methymercaptopurine (6MMP) and the 6-thioguanine nucleotides (6TGN), with 6TGN being responsible for thiopurine efficacy by causing apoptosis and preventing activation and proliferation of T-lymphocytes. In IBD, conventional weight-based dosing with thiopurines leads to an inadequate response in many patients. Utilizing measurement of these metabolites and then employing dose optimization strategies has led to markedly improved outcomes in IBD. Switching between thiopurines as well as the addition of low-dose allopurinol can overcome adverse events and elevate 6TGN levels into the therapeutic window. There is a paucity of data on thiopurine metabolites in rheumatological diseases and further research is required.

Thiopurine metabolite ratios for monitoring therapy in pediatric Crohn disease

OBJECTIVES

Thiopurines (azathioprine, 6-mercaptopurine) are a mainstay of treatment in Crohn disease (CD). Monitoring intracellular metabolite (6-thioguanine nucleotides [6-TGN] and 6-methylmercaptopurine [6-MMP]) levels can help optimize therapeutic efficacy and minimize potential toxicity. Determination of 6-MMP/6-TGN ratios may provide additional useful information, such as the identification of individuals with excessive thiopurine methyltransferase activity and disadvantageous 6-MMP overproduction. These patients are at increased risk of therapeutic failure and hepatotoxicity. The aim of the study was to evaluate the correlation of 6-MMP/6-TGN ratios with therapeutic efficacy and risk of hepatotoxicity in CD.

METHODS

The present study was a single-center cross-sectional study including pediatric patients with CD studied prospectively with clinical and laboratory assessments along with serial measurements of 6-MMP and 6-TGN. Clinical response was determined using established clinical indices.

RESULTS

The study included 238 pediatric patients with CD with a total of 1648 evaluation points. The patients were in steroid-free remission at 59.1% of the evaluation points. 6-MMP/6-TGN ratios of 4 to 24 were protective against relapse (odds ratio [OR] 0.52, 95% confidence interval [CI] -0.39 to 0.69, P = 0.001). Hepatotoxicity was associated with high 6-MMP levels (>3919  pmol/8 × 10 red blood cell count: OR 7.65, 95% CI 3.7-15.9, P = 0.001) and high 6-MMP/6-TGN ratios (>24: OR 5.35, 95% CI -3.43 to 8.43, P = 0.001).

CONCLUSIONS

We observed significant associations between 6-MMP/6-TGN ratios and clinical response, and risk of hepatotoxicity. Our results suggest that determination of thiopurine metabolite ratios is a valuable tool for identification of patients at increased risk of therapeutic failure and hepatotoxicity.

Evaluation of azathioprine-induced cytotoxicity in an in vitro rat hepatocyte system

Azathioprine (AZA) is widely used in clinical practice for preventing graft rejection in organ transplantations and various autoimmune and dermatological diseases with documented unpredictable hepatotoxicity. The potential molecular cytotoxic mechanisms of AZA towards isolated rat hepatocytes were investigated in this study using “Accelerated Cytotoxicity Mechanism Screening” techniques. The concentration of AZA required to cause 50% cytotoxicity in 2 hrs at 37°C was found to be 400 μM. A significant increase in AZA-induced cytotoxicity and reactive oxygen species (ROS) formation was observed when glutathione- (GSH-) depleted hepatocytes were used. The addition of N-acetylcysteine decreased cytotoxicity and ROS formation. Xanthine oxidase inhibition by allopurinol decreased AZA-induced cytotoxicity, ROS, and hydrogen peroxide (H₂O₂) formation and increased % mitochondrial membrane potential (MMP). Addition of N-acetylcysteine and allopurinol together caused nearly complete cytoprotection against AZA-induced hepatocyte death. TEMPOL (4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl), a known ROS scavenger and a superoxide dismutase mimic, and antioxidants, like DPPD (N,N′-diphenyl-p-phenylenediamine), Trolox (a water soluble vitamin E analogue), and mesna (2-mercaptoethanesulfonate), also decreased hepatocyte death and ROS formation. Results from this study suggest that AZA-induced cytotoxicity in isolated rat hepatocytes may be partly due to ROS formation and GSH depletion that resulted in oxidative stress and mitochondrial injury.

Are we using and monitoring thiopurines and biologics optimally?

The use of biologics and thiopurines in patients with inflammatory bowel disease has increased rapidly over the last 2 decades with both classes of drugs being used more frequently and earlier in the disease course. This vogue has come about through a realisation that for some patients Crohn's disease and ulcerative colitis are progressive diseases and that use of these therapies can sometimes prevent that progression. However, knowledge about the optimal way in which to use these drugs continues to evolve. In this paper, the evidence regarding optimal timing and dosing of thiopurines and biologics will be reviewed as will the role of thiopurine methyltransferase testing along with therapeutic drug monitoring of both thiopurines and biologics. In addition, possible future applications of biologic drug level and anti-drug antibody testing will be considered.

Can we get more from our current treatments?

Crohn's disease is a chronic incurable condition that normally requires lifelong treatment. Whilst the anti-TNF agents have revolutionised the management of Crohn's disease over the last fifteen years, they are not a panacea. In particular, in part due to their immunogenic nature, loss of response limits their long term effectiveness in many patients. The only other long term disease-modifying options are the immunomodulators, methotrexate, azathioprine and mercaptopurine. Therefore, given the limited number of drugs available to treat Crohn's disease, it is important that efforts are made to ensure that drugs are used in the best way possible as once a drug is deemed ineffective, it is rarely used again. For the growing number of patients who have active disease despite having been exposed to all standard therapies, failure to optimise drug therapy may lead to missed opportunities in the management of their disease. In this review, optimisation of drugs commonly used in the management of Crohn's disease will be discussed.

Randomised clinical trial: individualised vs. weight-based dosing of azathioprine in Crohn's disease

BACKGROUND

Azathioprine (AZA), a pro-drug metabolised to the active metabolites 6-tioguanine nucleotides (6TGN), is a steroid-sparing therapy for Crohn's disease (CD).

AIM

To investigate whether AZA therapy is optimised by individualised dosing based on thiopurine methyltransferase (TPMT) activity and 6TGN concentrations.

METHODS

This multicentre, double-blind, randomised controlled trial compared the efficacy and safety of weight-based vs. individualised AZA dosing in inducing and maintaining remission in adults and children with steroid-treated CD. The primary outcome was clinical remission (CR) at 16 weeks. In the weight-based arm, subjects received 2.5 mg/kg/day. In the individualised dosing arm, the initial AZA dose was 1.0 mg/kg/day (if intermediate TPMT) or 2.5 mg/kg/day (if normal TPMT). Starting at week 5, the dose was adjusted to target 6TGN concentrations of 250-400 pmol/8 × 10(8) red blood cells (RBC), or to a maximal dose of 4 mg/kg/day.

RESULTS

After randomising 50 subjects, the trial was stopped prematurely due to insufficient enrolment. In intention-to-treat analysis, CR rates at week 16 were 40% in the individualised arm vs. 16% in the weight-based arm (P = 0.11). In per-protocol (PP) analysis, week 16 CR rates were 60% in the individualised arm and 25% in the weight-based arm (P = 0.12). At week 16, median 6TGN concentrations in PP remitters and nonremitters were 216 and 149 pmol/8 × 10(8) RBC respectively (P = 0.07).

CONCLUSIONS

Despite trends favouring individualised over weight-based AZA dosing, there were no statistically significant differences in efficacy, likely due to low statistical power and inability to achieve the target 6TGN concentrations in the individualised arm. [Clinicaltrials.Gov Identifier Nct00113503].

Positioning therapy for Crohn's disease

The therapy of Crohn's disease is constantly evolving. It is widely recognized that clinical assessment does not stage disease activity accurately and that endoscopic healing is associated with improved long-term outcomes. Disease management is therefore transitioning to a new paradigm that includes direct assessment of disease severity (endoscopically in most patients), followed by assessment of mucosal healing. New approaches have helped optimize the use of the thiopurines, methotrexate and anti-TNF agents. Novel agents with different mechanisms of action are expanding our therapeutic armamentarium. The major challenge of the future will be to identify patient subgroups best suited to particular therapeutic approaches. In the meantime, studies of comparative effectiveness will be crucial in positioning therapies relative to each other.

Thiopurine metabolite measurement leads to changes in management of inflammatory bowel disease

BACKGROUND

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.

AIMS

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

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Establishment of thiopurine S-methyltransferase gene knockdown in jurkat T-lymphocytes: an in vitro model of TPMT polymorphism

BACKGROUND

Thiopurine S-methyltransferase (TPMT) is an excellent example of an enzyme whose pharmacogenetic polymorphisms affect efficacy and toxicity of a drug. The association between TPMT activity and thiopurine-related myelosuppression is well recognized. To study the significance of TPMT deficiency in thiopurine metabolism and immunosuppressive activity in vitro, we established RNA interference-based TPMT knockdown (kd) in a Jurkat cell line.

RESULTS

In Jurkat TPMT kd cells, TPMT expression was reduced to 73% at the RNA level and 83% at the protein level. TPMT kd cells were more sensitive to 6-mercaptopurine (6-MP) (10 μmol/L) and 6-thioguanine (6-TG) (8 μmol/L) than wild-type (wt) cells, (32% versus 20%) and (18% versus 9%), respectively. Both Jurkat wt and kd cells were more sensitive to 6-TG-induced apoptosis than to 6-MP. 6-TG activity was also more affected by TPMT levels than was 6-MP as reflected by IC60, concentrations that is, 6-MP [4.6 μmol/L (wt) and 4.7 μmol/L (kd)], 6-TG [2.7 μmol/L (wt) and 0.8 μmol/L (kd)]. IC60 concentrations induced significant apoptosis in both Jurkat wt and kd cells (257%, versus 314%) with 6-MP and (323% versus 306%) with 6-TG, respectively. At IC60 (6-MP) 6-thioguanine nucleotides (6-TGN) accumulation in cells was 518 versus 447 pmol/million cells in wt and kd cells, respectively. On the other hand 6-TGN accumulation at IC60 (6-TG) was 477 versus 570 pmol/million cells in wt and kd cells, respectively. 6-Methylated mercaptopurine (6-MeMP) concentrations were more affected than 6-TGN by TPMT kd (194 versus 10 pmol/million cells) in wt and kd cells, respectively.

CONCLUSION

We conclude that TPMT kd cells are an appropriate in vitro model to investigate the significance of TPMT deficiency with thiopurine therapy and could be helpful in understanding possible clinical consequences of TPMT polymorphism.

Low allopurinol doses are sufficient to optimize azathioprine therapy in inflammatory bowel disease patients with inadequate thiopurine metabolite concentrations

PURPOSE

Recent studies in patients with inflammatory bowel diseases (IBD) on thiopurine therapy suggest that too low 6-thioguanine nucleotide concentrations (6-TGN) and too high methylmercaptopurine nucleotide concentrations (MMPN) can be reversed by a combination therapy of allopurinol and low-dose thiopurines. To date, however, optimal dosing has not been established. The aim of this study was to evaluate the minimal allopurinol doses necessary to achieve adequate 6-TGN concentrations in combination with low-dose azathioprine.

METHODS

A stepwise dose-escalation of allopurinol was performed in 11 azathioprine-pretreated IBD patients with inadequately low 6-TGN concentrations (<235 pmol/8 × 10(8) erythrocytes) and/or elevated MMPN concentrations (>5,000 pmol/8 × 10(8) erythrocytes) and/or elevated liver enzymes (alanine aminotransferase and/or aspartate aminotransferase levels one- to threefold the upper limit of normal). Six patients were recruited into an open study, and five were treated in the context of an individualized therapeutic approach. Adverse effects, azathioprine metabolites, liver enzymes and whole blood counts were monitored two to three times per month.

RESULTS

Adequate 6-TGN concentrations were achieved with a combination of 25 mg allopurinol and 50 mg azathioprine in one patient and with 50 mg allopurinol and 50 mg azathioprine in nine patients. Median 6-TGN concentrations (range) were 336 (290-488) pmol/8 × 10(8) erythrocytes after an 8-week-long intake of the final dose combination. One patient dropped out due to nausea after the first intake. MMPN concentrations and liver enzymes normalized immediately in all affected patients. All patients finishing the dose-escalation regimen tolerated the treatment without toxicity.

CONCLUSIONS

Combination therapy with only 50 mg allopurinol and 50 mg azathioprine daily is sufficient, efficacious and safe in most IBD patients with inadequate thiopurine metabolite concentrations to optimize azathioprine-based IBD therapy.

Thiopurines in inflammatory bowel disease revisited

Although a great variety of new drugs have been introduced for the therapy of inflammatory bowel diseases so far, a definite cure of the disease is still out of scope. An anti-inflammatory approach to induce remission followed by maintenance therapy with immunosupressants is still the mainstay of therapy. Thiopurines comprising azathioprine and its active metabolite mercaptopurine as well as tioguanine, are widely used in the therapy of chronic active inflammatory bowel disease (IBD). Their steroid sparing potential and efficacy in remission maintenance are out of doubt. Unfortunately, untoward adverse events are frequently observed and may preclude further administration or be life threatening. This review will focus on new aspects of thiopurine therapy in IBD, its efficacy and safety.

Role of thiopurine metabolite testing and thiopurine methyltransferase determination in pediatric IBD

Thiopurines have been used in inflammatory bowel disease (IBD) for >30 years, and measurements of both thiopurine methyltransferase (TPMT) and thiopurine (TP) metabolites, 6-thioguanine nucleotides (6-TGN) and 6-methylmercaptopurine (6-MMP), have been readily available. The North American Society for Pediatric Gastroenterology, Hepatology, and Nutrition (NASPGHAN) Committee on Inflammatory Bowel Disease thought it appropriate to review the present indications for use of TPMT and TP metabolite testing. Substantial evidence demonstrates that TP therapy is useful for both Crohn disease and ulcerative colitis. Review of the existing data yielded the following recommendations. TPMT testing is recommended before initiation of TPs to identify individuals who are homozygote recessive or have extremely low TPMT activity, with the latter having more reliability than the former. Individuals who are homozygous recessive or have extremely low TPMT activity should avoid the use of TPs because of concerns for significant leukopenia. TMPT testing does not predict all cases of leukopenia and has no value to predict hypersensitivity adverse effects such as pancreatitis. Any potential value to reduce the risk of malignancy has not been studied. All individuals taking TPs should have routine monitoring with complete blood cell count and white blood cell count differential to evaluate for leukopenia regardless of TPMT testing results. Metabolite testing can be used to determine adherence with TP therapy. Metabolite testing can be used to guide dose increases or modifications in patients with active disease. Consideration would include either increasing the dose, changing therapy or for those with elevated transaminases or an elevated 6-MMP, using adjunctive allopurinol to help raise 6-thioguanine metabolites and suppress formation of 6-MMP. Routine and repetitive metabolite testing has little or no role in patients who are doing well and taking an acceptable dose of a TP.

Gene expression and thiopurine metabolite profiling in inflammatory bowel disease - novel clues to drug targets and disease mechanisms?

BACKGROUND AND AIMS

Thiopurines are effective to induce and maintain remission in inflammatory bowel disease (IBD). The methyl thioinosine monophosphate (meTIMP)/6-thioguanine nucleotide (6-TGN) concentration ratio has been associated with drug efficacy. Here we explored the molecular basis of differences in metabolite profiles and in relation to disease activity.

METHODS

Transcriptional profiles in blood samples from an exploratory IBD-patient cohort (n = 21) with a normal thiopurine S-methyltransferase phenotype and meTIMP/6-TGN ratios >20, 10.0-14.0 and ≤4, respectively, were assessed by hybridization to microarrays. Results were further evaluated with RT qPCR in an expanded patient cohort (n = 54). Additionally, 30 purine/thiopurine related genes were analysed separately.

RESULTS

Among 17 genes identified by microarray-screening, there were none with a known relationship to pathways of purines/thiopurines. For nine of them a correlation between expression level and the concentration of meTIMP, 6-TGN and/or the meTIMP/6-TGN ratio was confirmed in the expanded cohort. Nine of the purine/thiopurine related genes were identified in the expanded cohort to correlate with meTIMP, 6-TGN and/or the meTIMP/6-TGN ratio. However, only small differences in gene expression levels were noticed over the three different metabolite profiles. The expression levels of four genes identified by microarray screening (PLCB2, HVCN1, CTSS, and DEF8) and one purine/thiopurine related gene (NME6) correlated significantly with the clinical activity of Crohn's disease. Additionally, 16 of the genes from the expanded patient cohort interacted in networks with candidate IBD susceptibility genes.

CONCLUSIONS

Seventeen of the 18 genes which correlated with thiopurine metabolite levels also correlated with disease activity or participated in networks with candidate IBD susceptibility genes involved in processes such as purine metabolism, cytokine signaling, and functioning of invariant natural killer T cells, T cells and B cells. Therefore, we conclude that the identified genes to a large extent are related to drug targets and disease mechanisms of IBD.

Safety and effectiveness of long-term allopurinol-thiopurine maintenance treatment in inflammatory bowel disease

BACKGROUND

Thiopurines are the mainstay of conventional maintenance therapy in inflammatory bowel disease (IBD). Unfortunately, up to 50% of patients discontinue immunosuppressive therapy within 2 years due to intolerance or lack of efficacy. Allopurinol with low-dose thiopurine can optimize thiopurine metabolism for IBD patients with preferential shunting toward 6-methyl mercaptopurine (6-MMP) formation. The aim of this study was to assess long-term maintenance effectiveness and tolerability of allopurinol-thiopurine therapy in a larger multicenter cohort of IBD patients.

METHODS

Enrolled patients who failed monotherapy with thiopurines due to a skewed metabolism were subsequently treated with a combination therapy of allopurinol and low-dose thiopurine. Adverse events were monitored and therapeutic adherence was assessed. Seventy-seven IBD patients were enrolled with a mean follow-up of 19 months.

RESULTS

The median 6-thioguanine nucleotide concentration increased from 145 during monotherapy to 271 pmol/8 × 10(8) red blood cell (RBC) after at least 8 weeks of combination therapy while reducing the thiopurine dosage (P < 0.001). In contrast, median 6-MMP concentrations decreased from 10,110 to 265 pmol/8 × 10(8) RBC (P < 0.001). Leukopenia occurred in 12 patients (16%), requiring dose adaptation. Liver test abnormalities normalized in 81% of patients after the addition of allopurinol. Sixteen (21%) patients had to discontinue combination therapy. The percentage of patients still using combination therapy at 6, 12, 24, and 60 months was 87%, 85%, 76%, and 65%, respectively.

CONCLUSIONS

Long-term combination therapy with allopurinol and low-dose thiopurines is an effective and well-tolerated treatment in IBD patients with a skewed thiopurine metabolism.

Initiating azathioprine for Crohn's disease

Azathioprine (AZA) and 6-mercaptopurine are therapeutic options for patients with moderate to severe inflammatory Crohn's disease. AZA has both a complex metabolism and potential for adverse events that can be clinically challenging. AZA has been shown to maintain remission and reduce corticosteroid use in patients with Crohn's disease. There is heterogeneous thiopurine methyltransferase metabolism among patients, which has implications for clinical dosing and risk for adverse events. Routine thiopurine methyltransferase testing before the initiation of AZA will reduce early leukopenia and is mandatory to avoid potentially life-threatening myelotoxicity. Thiopurine metabolite assays may aid in the assessment of adherence and adverse events. Patients who do not respond to AZA therapy may benefit from the addition of biologic therapy or methotrexate.

Optimization of conventional therapy in patients with IBD

The majority of patients with IBD use conventional therapy (namely, aminosalicylates, antibiotics, corticosteroids and immunomodulatory agents) for prolonged periods of time, to both induce and maintain remission. Treatment paradigms in IBD have evolved towards a rapid escalation of therapy to achieve stringent goals, including mucosal healing and a reduction in the need for hospital admission and surgery. In this context, the failure to optimize conventional therapy can lead to a potentially effective treatment being abandoned too early, which is undesirable when only a limited number of drugs are effective in the management of IBD, and could also lead to patients being unnecessarily exposed to potentially toxic and/or expensive biologic drugs. This Review provides an overview of the many ways in which conventional therapy can be optimized, and describes strategies to improve adherence to drug regimens, such as simplifying the dosing regimen, optimizing drug delivery and dose, and tailoring medication on the basis of metabolite levels.

Optimizing thiopurine therapy in inflammatory bowel disease

Despite recent advances, the therapeutic armamentarium for inflammatory bowel disease (IBD) is still limited. In addition, a step-up approach is recommended for most IBD patients. Thus, optimizing each medical therapy before switching to another drug class is the rule in clinical practice. Conventional therapies for IBD have not received the same amount of attention as biologic therapies over the last decade. However, due to their efficacy, safety, and low cost the thiopurine drugs azathioprine and 6-mercaptopurine remain the backbone of therapy for IBD. Pharmacogenomic advances and increased knowledge of their metabolism are allowing dosage optimization. Herein, after describing the pharmacogenetics and pharmacokinetics of thiopurines, we will discuss how to optimize thiopurine therapy. We will then underscore the need to take into account safety issues when optimizing thiopurine treatment.

Review article: the role of non-biological drugs in refractory inflammatory bowel disease

BACKGROUND

Up to one-third of patients with inflammatory bowel disease (IBD) do not respond to, or are intolerant of conventional immunosuppressive drugs. Although biological agents are alternative treatments, they may not be suitable or available to some patients.

AIM

To review the evidence for use of nonbiological drugs in the treatment of patients with IBD refractory to corticosteroids or thiopurines.

METHODS

A literature search was performed using PubMed for English language publications with predetermined search criteria to identify relevant studies.

RESULTS

Published evidence from uncontrolled series and controlled clinical trials has been used to produce a practical approach relevant to clinical practice which incorporates the indication, optimal dose, and side effects of various therapies including tacrolimus, methotrexate, thalidomide, tioguanine, mycophenolate mofotil, leucocyte apheresis, nutritional therapy, antibiotics, probiotics, allopurinol, rectal acetarsol and ciclosporin in the treatment of patients with refractory ulcerative colitis and Crohn's disease. Approaches to optimise thiopurine efficacy are also discussed.

CONCLUSIONS

Patients with IBD refractory to corticosteroids or thiopurines may respond to alternative anti-inflammatory chemical molecules, but the evidence base for many of these alternatives is limited and further trials are needed.