A Role for Thiopurine Metabolites in the Synergism Between Thiopurines and Infliximab in Inflammatory Bowel Disease

Detailed resume of S-methyltransferases: Categories, structures, biological functions and research advancements in related pathophysiology and pharmacotherapy

Methylation is a vital chemical reaction in the metabolism of many drugs, neurotransmitters, hormones, and exogenous compounds. Among them, S-methylation plays a significant role in the biotransformation of sulfur-containing compounds, particularly chemicals with sulfhydryl groups. Currently, only three S-methyltransferases have been reported: thiopurine methyltransferase (TPMT), thiol methyltransferase (TMT), and thioether methyltransferase (TEMT). These enzymes are involved in various biological processes such as gene regulation, signal transduction, protein repair, tumor progression, and biosynthesis and degradation reactions in animals, plants, and microorganisms. Furthermore, they play pivotal roles in the metabolic pathways of essential drugs and contribute to the advancement of diseases such as tumors. This paper reviews the research progress on relevant structural features, metabolic mechanisms, inhibitor development, and influencing factors (gene polymorphism, S-adenosylmethionine level, race, sex, age, and disease) of S-methyltransferases. We hope that a better comprehension of S-methyltransferases will help to provide a reference for the development of novel strategies for related disorders and improve long-term efficacy.

Therapeutic drug monitoring of vedolizumab therapy in inflammatory bowel disease

BACKGROUND

Therapeutic drug monitoring is effective for optimizing anti-tumor necrosis factor therapies in inflammatory bowel disease, but for vedolizumab, a gut-selective leucocyte migration inhibitor, data are scarce.

METHODS

Observational cohort study including 116 bio-experienced inflammatory bowel disease patients treated with vedolizumab for active luminal disease. Biobanked trough blood samples (n = 676) covering 96% of patients were analyzed using a drug-binding immunofluorometric assay. Steroid-free treatment outcomes were classified by clinical disease activity indices and objective findings, primarily endoscopy.

RESULTS

Patients with clinical remission to vedolizumab induction therapy (37%) had significantly higher trough levels than those without at weeks 6 (mean 34.1 vs 28.0 μg/mL, P = 0.03) and 10 (34.8 vs 27.5 μg/mL, P = 0.01). Optimal thresholds for discrimination were 32.4 μg/mL (AUCROC 0.66, P = 0.04) and 23.5 (AUCROC 0.67, P = 0.01), respectively. This positive association persisted during maintenance phase with 11.9 μg/mL (AUCROC 0.69, P < 0.01) associated with clinical remission (37%) and 15.3 (AUCROC 0.74, P < 0.001) for objective remission (46%). Stratification by temporal evolution of treatment effects revealed higher induction and maintenance vedolizumab levels in persistent and slow responders as compared to secondary or persistent failures. Pharmacokinetics was influenced by rare formation of anti-vedolizumab antibodies (2%), and to a lesser extent gender and albumin during induction, but not disease severity, concomitant steroids, or thiopurine metabolites. Switching to subcutaneous administrations resulted in 2.3-fold increase in steady-state trough levels.

CONCLUSION

Our study supports maintaining adequate drug exposure being essential for sustained positive outcomes of vedolizumab and emphasizes individualized, therapeutic drug monitoring-based treatment regimens. Controlled trials and pharmacokinetic modeling are, however, needed.

Choosing the Right Therapy at the Right Time for Pediatric Inflammatory Bowel Disease: Does Sequence Matter

Despite the enlarging therapeutic armamentarium, IBD is still plagued by a therapeutic ceiling. Precision medicine, with the selection of the "rights," may present a solution, and this review will discuss the critical process of pairing the right patient with right therapy at the right time. Firstly, the review will discuss the shift to and evidence behind early effective therapy. Then, it delves into promising future strategies of patient profiling to identify a patients' biological pathway(s) and prognosis. Finally, the review lays out practical considerations that drive treatment selection, particularly the impact of the therapeutic sequence.

Association between 6-thioguanine nucleotide levels and preventing production of antibodies to infliximab in patients with inflammatory bowel disease

OBJECTIVE

Combination therapy with infliximab and a thiopurine has been shown to be more effective than monotherapy in patients with inflammatory bowel disease (IBD). The therapeutic efficacy of thiopurines is correlated with 6-thioguanine (6-TGN) levels between 235 and 450 pmol/8×108 erythrocytes. The primary aim of the study was to investigate the association between 6-TGN levels and inhibition prevention of the production of antibodies to infliximab (ATI).

DESIGN

We performed a retrospective review of the medical records of patients being treated with infliximab for IBD at University Hospitals Bristol NHS Foundation Trust. Demographic and biochemical data were extracted, alongside thiopurine metabolite levels, trough levels of infliximab and the presence of ATI. χ2 tests were used to investigate the association between 6-TGN levels and prevention of ATI. Logistic regression was used to compare the odds of prevented ATI between those with a 6-TGN level between 235 and 450 pmol/8×108 erythrocytes, those with a 6-TGN level outside of this range, and the baseline group who were on infliximab monotherapy.

RESULTS

Data were extracted for 100 patients. Six of 32 patients with a 6-TGN level between 235 and 450 pmol/8×108 erythrocytes developed ATI (18.8%) compared with 14 out of 22 (63.6%) patients with a 6-TGN outside of this range and 32 out of 46 (69.6%) patients on monotherapy (p=0.001). The OR (95% CI) for prevented ATI in those with a 6-TGN between 235 and 450 pmol/8×108 erythrocytes compared with a 6-TGN outside of this range was 7.6 (2.2, 26.3) (p=0.001) and compared with monotherapy was 9.9 (3.3, 29.4) (p=0.001).

CONCLUSION

6-TGN levels between 235 and 450 pmol/8×108 erythrocytes prevented production of ATI. This supports therapeutic drug monitoring to help guide treatment and maximise the beneficial effects of combination therapy for patients with IBD.

GADECCU 2022 Guideline for the treatment of Ulcerative Colitis. Adaptation and updating of the GETECCU 2020 Guideline

INTRODUCTION

Ulcerative colitis (UC) is a chronic inflammatory disease that compromises the colon, affecting the quality of life of individuals of any age. In practice, there is a wide spectrum of clinical situations. The advances made in the physio pathogenesis of UC have allowed the development of new, more effective and safer therapeutic agents.

OBJECTIVES

To update and expand the evaluation of the efficacy and safety of relevant treatments for remission induction and maintenance after a mild, moderate or severe flare of UC.

RECIPIENTS

Gastroenterologists, coloproctologists, general practitioners, family physicians and others health professionals, interested in the treatment of UC.

METHODOLOGY

GADECCU authorities obtained authorization from GETECCU to adapt and update the GETECCU 2020 Guide for the treatment of UC. Prepared with GRADE methodology. A team was formed that included authors, a panel of experts, a nurse and a patient, methodological experts, and external reviewers. GRADE methodology was used with the new information.

RESULTS

A 118-page document was prepared with the 44 GADECCU 2022 recommendations, for different clinical situations and therapeutic options, according to levels of evidence. A section was added with the new molecules that are about to be available.

CONCLUSIONS

This guideline has been made in order to facilitate decision-making regarding the treatment of UC, adapting and updating the guide prepared by GETECCU in the year 2020.

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.

Discontinuation of Azathioprine could be considered in pediatric patients with Crohn's disease who have sustained clinical and deep remission

Few studies have demonstrated treatment strategies about the duration and cessation of medications in patients with Crohn's disease (CD). We investigated factors affecting clinical relapse after infliximab (IFX) or azathioprine (AZA) withdrawal in pediatric patients with CD on combination therapy. Pediatric patients with moderate-to-severe CD receiving combination therapy were analyzed retrospectively and factors associated with clinical relapse were investigated. Discontinuation of IFX or AZA was performed in patients who sustained clinical remission (CR) for at least two years and achieved deep remission. A total of 75 patients were included. Forty-four patients (58.7%) continued with combination therapy and 31 patients (41.3%) discontinued AZA or IFX (AZA withdrawal 10, IFX withdrawal 15, both withdrawal 6). Cox proportional-hazards regression and statistical internal validation identified three factors associated with clinical relapse: IFX cessation (hazard ratio; HR 2.982, P = 0.0081), IFX TLs during maintenance therapy (HR 0.581, P = 0.003), 6-thioguanine nucleotide (6-TGN) level (HR 0.978, P < 0.001). However, AZA cessation was not associated with clinical relapse (P = 0.9021). Even when applied in pediatric patients who met stringent criteria, IFX cessation increased the relapse risk. However, withdrawal of AZA could be contemplated in pediatric patients with CD who have sustained CR for at least 2 years and achieved deep remission.

Adverse Events of Thiopurine Therapy in Pediatric Inflammatory Bowel Disease and Correlations with Metabolites: A Cohort Study

BACKGROUND

In the recent era of growing availability of biological agents, the role of thiopurines needs to be reassessed with the focus on toxicity.

AIMS

We assessed the incidence and predictive factors of thiopurine-induced adverse events (AE) resulting in therapy cessation in pediatric inflammatory bowel disease (IBD), related to thiopurine metabolites and biochemical abnormalities, and determined overall drug survival.

METHODS

We performed a retrospective, single-center study of children diagnosed with IBD between 2000 and 2019 and treated with thiopurine therapy. The incidence of AE and overall drug survival of thiopurines were evaluated using the Kaplan-Meier method. Correlations between thiopurine metabolites and biochemical tests were computed using Spearman's correlation coefficient.

RESULTS

Of 391 patients with IBD, 233 patients (162 Crohn's disease, 62 ulcerative colitis, and 9 IBD-unclassified) were prescribed thiopurines (230 azathioprine and 3 mercaptopurine), of whom 50 patients (22%) discontinued treatment, at least temporary, due to thiopurine-induced AE (median follow-up 20.7 months). Twenty-six patients (52%) were rechallenged and 18 of them (70%) tolerated this. Sixteen patients (6%) switched to a second thiopurine agent after azathioprine intolerance and 10 of them (63%) tolerated this. No predictive factors for development of AE could be identified. Concentrations of 6-thioguanine nucleotides (6-TGN) were significantly correlated with white blood cell and neutrophil count, 6-methylmercaptopurine (6-MMP) concentrations with alanine aminotransferase and gamma-glutamyltranspeptidase.

CONCLUSIONS

Approximately 20% of pediatric patients with IBD discontinued thiopurine treatment due to AE. A rechallenge or switch to mercaptopurine is an effective strategy after development of AE. Concentrations of 6-TGN and 6-MMP are associated with biochemical abnormalities.

Biologic monotherapy versus combination therapy with immunomodulators in the induction and maintenance of remission of Crohn's disease and ulcerative colitis

Despite current guidelines, the optimal treatment of patients with inflammatory bowel disease (IBD) remains challenging. The available medications are not without risk and there is not a single correct treatment regimen for every patient. Personalizing treatment and selecting the most appropriate therapy is crucial for optimal response, remission, quality of life, and healthcare utilization. Biologics, especially anti-tumor necrosis factor-α medications, are widely used in the induction and maintenance of disease remission in patients with IBD. Similarly, immunomodulators, including thiopurines and methotrexate, are traditionally popular for the maintenance of remission. In this manuscript, we review the use of biologic monotherapy vs. combination therapy with immunomodulators for the treatment of ulcerative colitis and Crohn’s disease. We examine overall remission, immunogenicity and adverse effects, mainly serious infections and malignancy, in an effort to help guide treatment decisions and weigh the risks and benefits of biologic monotherapy vs. combination therapy.

Adding Thiopurine After Loss of Response to Infliximab Versus Early Combination in Treating Crohn's Disease: A Retrospective Study

BACKGROUND

Although combining thiopurine with infliximab (IFX) is considered to improve the clinical efficacy of IFX when treating Crohn's disease (CD), it also increases the risk of adverse events (AEs). We compared the efficacy and safety of delayed thiopurine addition after loss of response (LOR) to IFX with the efficacy and safety of an earlier combination of thiopurine and IFX.

METHODS

This retrospective study analyzed patients with CD who started IFX as a first-line biologic at Kyushu University Hospital between June 2002 and July 2018. Patients were assigned to either the early-combination (EC) group, who started IFX and thiopurine simultaneously, or the late-combination (LC) group, who were treated with IFX alone until they developed LOR. We compared the cumulative IFX continuation rates and AE incidence between the two groups.

RESULTS

One hundred seventy-six patients were enrolled in this study; 49 were enrolled in the EC group, and 127 were enrolled in the LC group. Disease activity at baseline did not significantly differ between the groups, nor did the cumulative IFX continuation rates differ between the groups (P = 0.30); however, the AE rate was significantly higher in the EC group than in the LC group (38.7% vs. 21.2%; P = 0.02). The severe AE rate was also higher in the EC group than in the LC group (18.3% vs 3.1%; P = 0.001).

CONCLUSION

Considering the risk-benefit balance, delayed addition of thiopurine after LOR to IFX might be an alternative strategy when using IFX to treat CD.

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

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

Thiopurines and their optimization during infliximab induction and maintenance: A retrospective study in Crohn's disease

BACKGROUND AND AIM

Combining therapy with a thiopurine is favored when commencing infliximab in Crohn's disease; however, the optimal 6-thioguanine nucleotide (TGN) level and how long to continue thiopurines after induction are uncertain. We aimed to compare outcomes after induction and during maintenance in combination therapy versus infliximab monotherapy in Crohn's and to examine whether TGN levels were associated with outcomes.

METHODS

Crohn's patients induced with infliximab with or without concomitant thiopurines were retrospectively identified. Response to induction and clinical outcomes in subsequent 6-month maintenance semesters were analyzed. A TGN level ≥235 pmol/8 × 10⁸ red blood cells was considered therapeutic.

RESULTS

In 89 patients, response to induction was higher in combination therapy than monotherapy (74 vs 47%, P = 0.04). This benefit was only seen in patients with a therapeutic TGN (odds ratio 3.72, confidence interval 1.07-13.0, P = 0.04). Combination therapy during induction yielded a three times longer time to subsequent need for treatment escalation or treatment failure compared with monotherapy (29 vs 9 months, P = 0.01), with both therapeutic and subtherapeutic TGNs independent predictors on multivariate analysis. Among 370 semesters, there was no difference in outcomes between combination therapy and monotherapy (P = 0.42), nor when combination semesters were stratified by therapeutic versus subtherapeutic TGN (P = 0.56). In semester 1 only, a significantly higher remission rate was observed with therapeutic compared with subtherapeutic TGN (76% vs 33%, P = 0.02).

CONCLUSIONS

Combination therapy dosed with an optimized thiopurine was superior to infliximab monotherapy for induction of response, durability of response, and clinical outcomes in the first 6 months following induction. Thereafter, combination therapy yielded no clinical advantage, supporting consideration of thiopurine withdrawal on a case-by-case basis.

Positive pharmacokinetic effect of azathioprine co-medication on infliximab trough levels is dose-dependent

BACKGROUND

Thiopurines seem to have positive effect on the pharmacokinetics of anti-tumor necrosis factor biologics. It has been suggested that a reduced dose of thiopurines is sufficient to achieve this synergism.

AIMS

To assess the differences of infliximab (IFX) trough levels according to the dose of concomitantly used azathioprine (AZA).

PATIENTS & METHODS

All IBD patients treated with IFX (Remicade^®) in two IBD centres between November 2015 and April 2017 were eligible. Infliximab trough levels were assessed by ELISA (Ridascreen^®, R-Biopharm). The differences in IFX trough levels according to AZA dose were analyzed statistically.

RESULTS

In total, 125 patients were included, 42 pts (33.6%) on infliximab monotherapy, 83 pts (66.4%) using combined immune suppression. The respective median IFX levels according to AZA dose were as follows: group 1 (no concomitant AZA) 2.83 μg/ml (range 0-12); group 2 (AZA dose less than 1 mg/kg) 4.91 μg/ml (range 0.09-15.36); group 3 (AZA dose 1 < 2 mg/kg) 5.67 (range 0.16-16.97); group 4 (AZA dose above 2 mg/kg) 7.53 μg/ml (range 1.15-8.73). The differences in IFX trough levels between the respective groups according to AZA dose were statistically significant (p = 0.0159).

CONCLUSION

The positive effect of azathioprine on infliximab levels seems to be dependent on the dose of concomitantly used azathioprine.

Evaluation of de-escalation of anti-TNF-α therapy in inflammatory bowel disease

Anti-tumour necrosis factor α therapy in inflammatory bowel disease has been shown to be effective in clinical practice. After more than a decade using these therapies the question arises about whether there is an appropriate time to suspend these therapies, and how this should be done. This review aims to evaluate the current evidence on these topics concerning anti-tumour necrosis factor α therapies, and eventually identify conditions and subgroups of patients that could potentially be candidates for withdrawal.

Clinical experience of optimising thiopurine use through metabolite measurement in inflammatory bowel disease

INTRODUCTION

Thiopurine therapy can be optimised by determining the concentration of the drug's metabolites.

PATIENTS AND METHODS

Retrospective analysis on a prospective database of 31 patients with inflammatory bowel disease who failed therapy with thiopurines. Thiopurine metabolites (6-thioguanine, 6-TGN and 6-methylmercaptopurine, 6-MMP) were measured by high-performance liquid chromatography (Laboratorios Cerba, Barcelona) and treatment was duly adjusted in accordance with the results. Clinical response was reassessed after six months.

RESULT

Despite the appropriate theoretical dose of thiopurines being administered, the dose was insufficient in 45.6% of patients (nonadherence to treatment suspected in 6.45%) and 16.2% received an excessive dose or the drug was metabolised by other metabolic pathways. After treatment was optimised based on metabolite levels, only 25.8% (8/31) were prescribed a biological agent, while 74.2% of cases (23/31) were managed through dose optimisation alone.

DISCUSSION

Monitoring thiopurine metabolite levels may help clinicians to assess non-responsive patients before adding or switching to another drug (generally a biological agent), thereby avoiding any additional costs or potential toxicity. This strategy may also help to identify patients receiving an insufficient dose and those with an alternative metabolic pathway, who could be candidates for low-dose AZA with allopurinol, as well as patients who are suspected of being non-adherent. In three out of four patients, switching to a biological agent can be avoided.

Reviewing the therapeutic role of budesonide in Crohn's disease

Oral budesonide is a glucocorticoid of primarily local action. In the field of digestive diseases, it is used mainly in inflammatory bowel disease, but also in other indications. This review addresses the pharmacology, pharmacodynamics and therapeutic use of budesonide. Its approved indications are reviewed, as well as other clinical scenarios in which it could play a role, in order to facilitate its use and improve the accuracy of its prescription.