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

Allopurinol Disrupts Purine Metabolism to Increase Damage in Experimental Colitis

Inflammatory bowel disease (IBD) is marked by a state of chronic energy deficiency that limits gut tissue wound healing. This energy shortfall is partially due to microbiota dysbiosis, resulting in the loss of microbiota-derived metabolites, which the epithelium relies on for energy procurement. The role of microbiota-sourced purines, such as hypoxanthine, as substrates salvaged by the colonic epithelium for nucleotide biogenesis and energy balance, has recently been appreciated for homeostasis and wound healing. Allopurinol, a synthetic hypoxanthine isomer commonly prescribed to treat excess uric acid in the blood, inhibits the degradation of hypoxanthine by xanthine oxidase, but also inhibits purine salvage. Although the use of allopurinol is common, studies regarding how allopurinol influences the gastrointestinal tract during colitis are largely nonexistent. In this work, a series of in vitro and in vivo experiments were performed to dissect the relationship between allopurinol, allopurinol metabolites, and colonic epithelial metabolism and function in health and during disease. Of particular significance, the in vivo investigation identified that a therapeutically relevant allopurinol dose shifts adenylate and creatine metabolism, leading to AMPK dysregulation and disrupted proliferation to attenuate wound healing and increased tissue damage in murine experimental colitis. Collectively, these findings underscore the importance of purine salvage on cellular metabolism and gut health in the context of IBD and provide insight regarding the use of allopurinol in patients with IBD.

Genome-wide multi-trait analysis of irritable bowel syndrome and related mental conditions identifies 38 new independent variants

BACKGROUND

Irritable bowel syndrome (IBS) is a chronic disorder of gut-brain interaction frequently accompanied by mental conditions, including depression and anxiety. Despite showing substantial heritability and being partly determined by a genetic component, the genetic underpinnings explaining the high rates of comorbidity remain largely unclear and there are no conclusive data on the temporal relationship between them. Exploring the overlapping genetic architecture between IBS and mental conditions may help to identify novel genetic loci and biological mechanisms underlying IBS and causal relationships between them.

METHODS

We quantified the genetic overlap between IBS, neuroticism, depression and anxiety, conducted a multi-trait genome-wide association study (GWAS) considering these traits and investigated causal relationships between them by using the largest GWAS to date.

RESULTS

IBS showed to be a highly polygenic disorder with extensive genetic sharing with mental conditions. Multi-trait analysis of IBS and neuroticism, depression and anxiety identified 42 genome-wide significant variants for IBS, of which 38 are novel. Fine-mapping risk loci highlighted 289 genes enriched in genes upregulated during early embryonic brain development and gene-sets related with psychiatric, digestive and autoimmune disorders. IBS-associated genes were enriched for target genes of anti-inflammatory and antirheumatic drugs, anesthetics and opioid dependence pharmacological treatment. Mendelian-randomization analysis accounting for correlated pleiotropy identified bidirectional causal effects between IBS and neuroticism and depression and causal effects of the genetic liability of IBS on anxiety.

CONCLUSIONS

These findings provide evidence of the polygenic architecture of IBS, identify novel genome-wide significant variants for IBS and extend previous knowledge on the genetic overlap and relationship between gastrointestinal and mental disorders.

Acral Skin Rash Caused by Altered Mercaptopurine Metabolism in Maintenance Therapy for B-Cell Acute Lymphoblastic Leukemia

6-mercaptopurine is a mainstay of acute lymphoblastic leukemia treatment. It has a narrow therapeutic window, dictated by its metabolite, thioguanine and 6-methylmercaptopurine. Skin manifestations usually consist of mild facial rash or hypersensitivity exanthems. We report a child who developed a painful acral rash and mucositis while undergoing maintenance therapy for B-cell acute lymphoblastic leukemia without infectious or known drug etiology. Thiopurine metabolites were skewed toward 6-methylmercaptopurine. Two weeks after allopurinol was added and 6-mercaptopurine (6-MP) dose adjusted, the cutaneous manifestations and other constitutional symptoms resolved. We posit that the rash was because of 6-MP toxicity related to skewed metabolism, adding to the growing list of toxicity related to altered 6-MP metabolism.

An Update on Current Pharmacotherapeutic Options for the Treatment of Ulcerative Colitis

The main goals of Ulcerative Colitis (UC) treatment are to both induce and maintain the clinical and endoscopic remission of disease, reduce the incidence of complications such as dysplasia and colorectal carcinoma and improve quality of life. Although a curative medical treatment for UC has not yet been found, new therapeutic strategies addressing specific pathogenetic mechanisms of disease are emerging. Notwithstanding these novel therapies, non-biological conventional drugs remain a mainstay of treatment. The aim of this review is to summarize current therapeutic strategies used as treatment for ulcerative colitis and to briefly focus on emerging therapeutic strategies, including novel biologic therapies and small molecules. To date, multiple therapeutic approaches can be adopted in UC and the range of available compounds is constantly increasing. In this era, the realization of well-designed comparative clinical trials, as well as the definition of specific therapeutic models, would be strongly suggested in order to achieve personalized management for UC patients.

Cytotoxicity of Thiopurine Drugs in Patients with Inflammatory Bowel Disease

The effectiveness of thiopurine drugs in inflammatory bowel disease (IBD) was confirmed more than a half-century ago. It was proven that these can be essential immunomodulatory medications. Since then, they have been used routinely to maintain remission of Crohn’s disease (CD) and ulcerative colitis (UC). The cytotoxic properties of thiopurines and the numerous adverse effects of the treatment are controversial. However, the research subject of their pharmacology, therapy monitoring, and the search for predictive markers are still very relevant. In this article, we provide an overview of the current knowledge and findings in the field of thiopurines in IBD, focusing on the aspect of their cytotoxicity. Due to thiopurines’ benefits in IBD therapy, it is expected that they will still constitute an essential part of the CD and UC treatment algorithm. More studies are still required on the modulation of the action of thiopurines in combination therapy and their interaction with the gut microbiota.

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.

Longitudinal Multi-omics Reveals Subset-Specific Mechanisms Underlying Irritable Bowel Syndrome

The gut microbiome has been implicated in multiple human chronic gastrointestinal (GI) disorders. Determining its mechanistic role in disease has been difficult due to apparent disconnects between animal and human studies and lack of an integrated multi-omics view of disease-specific physiological changes. We integrated longitudinal multi-omics data from the gut microbiome, metabolome, host epigenome, and transcriptome in the context of irritable bowel syndrome (IBS) host physiology. We identified IBS subtype-specific and symptom-related variation in microbial composition and function. A subset of identified changes in microbial metabolites correspond to host physiological mechanisms that are relevant to IBS. By integrating multiple data layers, we identified purine metabolism as a novel host-microbial metabolic pathway in IBS with translational potential. Our study highlights the importance of longitudinal sampling and integrating complementary multi-omics data to identify functional mechanisms that can serve as therapeutic targets in a comprehensive treatment strategy for chronic GI diseases. VIDEO ABSTRACT.

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.

Outcome of concomitant treatment with thiopurines and allopurinol in patients with inflammatory bowel disease: A nationwide Danish cohort study

BACKGROUND

Thiopurine and allopurinol in combination are associated with clinical remission in inflammatory bowel diseases but their influence on subsequent outcomes is unclear. We compared outcomes during exposure to both thiopurines and allopurinol versus thiopurines alone.

METHODS

We established a nationwide cohort of patients with inflammatory bowel diseases exposed to thiopurines ± allopurinol during 1999-2014, using registry data. Patients were followed until hospitalization, surgery, anti-TNFα, or death (as a primary composite outcome). We used Poisson regression analyses to calculate incidence rate ratios overall and stratified by calendar period (assuming the combined exposure was unintended before 2009).

RESULTS

A total of 10,367 patients with inflammatory bowel diseases (Crohn's disease, n = 5484; ulcerative colitis, n = 4883) received thiopurines. Of these, 217 (2.1%) also received allopurinol. During 24,714 person years of follow-up, we observed 40 outcomes among thiopurine-allopurinol-exposed patients, and 4745 outcomes among those who were thiopurine exposed; incidence rate ratio, 1.26 (95% confidence interval, 0.92-1.73). The incidence rate ratios decreased over time: 4.88 (95% confidence interval 2.53-9.45) for 1999-2003, 2.19 (95% confidence interval, 1.17-4.09) for 2004-2008 and 0.80 (95% confidence interval, 0.52-1.23) for 2009-2014.

CONCLUSION

Our nationwide inflammatory bowel disease cohort study shows that concomitant thiopurine-allopurinol is as safe to use as thiopurines alone, with a tendency towards a positive effect on clinical outcomes in recent calendar periods when combined use was intended.

Real-life study of safety of thiopurine-allopurinol combination therapy in inflammatory bowel disease: myelotoxicity and hepatotoxicity rarely affect maintenance treatment

BACKGROUND

Low-dose thiopurine-allopurinol (LDTA) combination therapy is a commonly applied optimisation strategy in IBD patients with a skewed thiopurine metabolism.

AIM

To assess continued LDTA maintenance treatment at annual intervals and explore risk factors for treatment cessation METHODS: Adult IBD patients treated with LDTA between 2009 and 2016 were retrospectively included. Data on the incidence of clinical and laboratory adverse events (AEs), including hepatotoxicity and myelotoxicity resulting in imposing LDTA therapy cessation and associated risk factors were collected.

RESULTS

In total, 221 IBD patients (46% male, median age 42 years) were included. Maintenance LDTA treatment was continued in 78% of patients at 1 year (n = 145), 66% at 2 years (n = 83), 57% at 3 years (n = 52) and 52% at 4 years (n = 33). Treatment in patients receiving LDTA therapy for AEs during thiopurine monotherapy was more often continued than in patients initiating LDTA for other indications (eg, ineffectiveness of thiopurine monotherapy, routinely discovered skewed metabolism) (P = 0.016). Myelotoxicity during thiopurine monotherapy resolved in 87% and hepatotoxicity in 86% after median of 1.2 and 1.4 months after LDTA initiation. Cumulative incidence of AEs during LDTA resulting in therapy cessation within total follow-up of 449 treatment-years was 7% for clinical AEs, 4% for myelotoxicity and 1% for hepatotoxicity.

CONCLUSION

LDTA therapy is a safe and beneficial optimisation strategy in IBD patients. Continued maintenance LDTA treatment is 52% after 4 years of treatment and most commonly affected by ineffectiveness of LDTA rather than LDTA-attributed toxicity. LDTA optimisation strategy is most advantageous in patients failing thiopurine monotherapy due to AEs.

Fecal calprotectin is significantly linked to azathioprine metabolite concentrations in Crohn's disease

BACKGROUND

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

AIMS

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

PATIENTS AND METHODS

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

RESULTS

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

CONCLUSION

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

Low-dose thiopurine with allopurinol co-therapy overcomes thiopurine intolerance and allows thiopurine continuation in inflammatory bowel disease

AIMS

To assess the utility and tolerability of thiopurine-allopurinol co-therapy in inflammatory bowel disease (IBD) patients with intolerance to thiopurine monotherapy.

METHODS

A retrospective observational study assessed cases of thiopurine intolerance then switched to thiopurine allopurinol co-therapy between 2011 and 2015 at two centres. Indications for switch, dosing and subsequent clinical outcomes (including thiopurine persistence) were recorded.

RESULTS

Of 767 patients on thiopurines for IBD, 89 (12%) were switched to co-therapy for intolerance. 64/89 (72%) had Crohn's disease, 38 (43%) were males, median age at switch was 40y (range 17-78), median IBD duration 6y (0-29). Median follow-up was 1.9y (0-5). Reasons for switching to co-therapy included fatigue (37%), hepatotoxicity (23%), nausea (23%), arthralgia (10%), headache (12%) and hypersensitivity reaction (4%). Overall, 66 (74%) patients remained on co-therapy until most recent review and achieved a clinical response. High rates of overcoming intolerance (62-100%) occurred with co-therapy for all reasons above, although fatigue was less amenable to switching than non-fatigue indications (62% vs 91%, p = <0.001). Of 34 patients not escalated to biologics with endoscopic data, 15 were in remission (44%) at most recent review.

CONCLUSION

Low-dose thiopurine combined with allopurinol appears safe and effective in overcoming intolerances to thiopurine monotherapy in many cases.