Clinical usefulness of therapeutic drug monitoring of thiopurines in patients with inadequately controlled inflammatory bowel disease

Clinical trial: Combination allopurinol-thiopurine versus standard thiopurine in patients with IBD escalating to immunomodulators (the DECIDER study)

BACKGROUND

Thiopurines are established treatments for inflammatory bowel disease (IBD), yet concerns remain regarding their safety.

AIM

To evaluate the use of thiopurine-allopurinol combination therapy compared to standard thiopurine therapy in IBD.

METHODS

We performed a multicentre, randomised, placebo-controlled trial to compare the efficacy and safety of thiopurine-allopurinol versus thiopurine with placebo for adults commencing a thiopurine for IBD. Patients had active disease at baseline; dosing of therapy was based on a pre-specified regimen and subsequent metabolites. The primary outcome was the proportion of patients achieving a composite of symptomatic disease activity remission (Harvey Bradshaw Index <5 for Crohn's disease, Simple Clinical Colitis Activity Index <4 for ulcerative colitis) and a faecal calprotectin <150 μg/g after 26 weeks of treatment.

RESULTS

The trial was terminated early due to slow recruitment. We randomised 102 participants (54 thiopurine-allopurinol, 48 thiopurine with placebo) with similar age (median 42 vs 48 years) and sex distribution (46% women per group). A higher proportion achieved the primary outcome in the thiopurine-allopurinol group (50% vs 35%, p = 0.14) and fewer participants stopped their allocated therapy due to adverse events (11% vs 29%, p = 0.02). Also, within the thiopurine-allopurinol group, thiopurine dose adjustments were less frequent (69% vs 92%, p = 0.03), a higher proportion achieved an early therapeutic 6-TGN level at week 6 (71% vs 53%, p = 0.19), and adverse events attributed to therapy were less frequent (15% vs 44%, p = 0.002).

CONCLUSION

Thiopurine-allopurinol therapy is safe and mitigates thiopurine adverse effects, thus enhancing tolerability without compromising efficacy (ACTRN12613001347752).

Therapeutic drug monitoring of disease-modifying antirheumatic drugs in circulating leukocytes in immune-mediated inflammatory diseases

The treatment of immune-mediated inflammatory diseases (IMIDs) is one of the main challenges of modern medicine. Although a number of disease-modifying antirheumatic drugs (DMARDs) are available, there is wide variability in clinical response to treatment among individuals. Therapeutic drug monitoring (TDM) has been proposed to optimize treatment; however, some patients still experience unsatisfactory outcomes, although the blood concentrations of drugs in these patients remain in the therapeutic range. One possible reason for this is that the conventional samples (e.g., whole blood or plasma) used in TDM may not accurately reflect drug concentrations or concentrations of their metabolites at the target site. Hence, more refined TDM approaches to guide clinical decisions related to dose optimization are necessary. Circulating leukocytes or white blood cells have a critical role in driving the inflammatory process. They are recruited to the site of injury, infection and inflammation, and the main target of small molecule DMARDs is within immune cells. Given this, assaying drug concentrations in leukocytes has been proposed to be of possible relevance to the interpretation of outcomes. This review focuses on the clinical implications and challenges of drug monitoring of DMARDs in peripheral blood leukocytes from therapeutic or toxicological perspectives in IMIDs.

Proactive Metabolite Testing in Patients on Thiopurine May Yield Long-Term Clinical Benefits in Inflammatory Bowel Disease

BACKGROUND

The thiopurine medications are well established in the treatment of inflammatory bowel disease (IBD). There is significant variation in levels of toxic and therapeutic metabolites. Current data from small or short-term studies support therapeutic drug monitoring (TDM) in assessing azathioprine (AZA) and 6-mercaptopurine (6MP). TDM of thiopurines involves measurement and interpretation of metabolites 6-TGN and 6-MMPR.

AIMS

This study aimed to assess long-cterm outcomes of patients on thiopurines following therapeutic drug monitoring.

METHODS

A multicenter retrospective observational study of outcomes post thiopurine TDM was conducted. Demographics, disease characteristics, physician global assessment, IBD therapy at baseline TDM and again at 12 months were collected. Clinical outcomes were analyzed according to TDM result, and indication for TDM including proactive and other indications.

RESULTS

The study included 541 patients. Only 39% of patients had appropriate dosing of thiopurines. AZA/6MP TDM informed a management change in 61.9%, and enabled 88.8% of the cohort to continue AZA/6MP following TDM. At 12 months following TDM the majority (74.1%) of the cohort remained on AZA/6MP. Clinical remission was higher at 12-months following thiopurines TDM (68%) compared to baseline (37%), including proactive TDM. Post TDM, 13.0% of patients were identified as shunters and commenced on thiopurine-allopurinol co-therapy.

CONCLUSION

Thiopurine TDM resulted in a change in management for the majority of patients. Post TDM significantly more patients were in remission. TDM allowed the identification of non-adherence and shunters who, without intervention, would not reach therapeutic drug levels. Proactive TDM allowed identification and management of inappropriate dosing, and was associated with increased levels of clinical remission.

Clinical utility of thiopurine metabolite monitoring in inflammatory bowel disease and its impact on healthcare utilization in Singapore

Background and Aim

Thiopurines are recommended for maintenance of steroid‐free remission (SFR) in inflammatory bowel disease (IBD). Thiopurine metabolite monitoring (MM) is increasingly used in the West but remains novel in Singapore, with limited information on its therapeutic and economic benefits. Hence, this study aims to investigate MM's clinical utility and its impact on healthcare resource utilization in Singaporean IBD patients.

Methods

A retrospective observational study was conducted at Singapore General Hospital outpatient IBD Centre. Patients with IBD, baseline MM during 2014–2017, and weight‐based thiopurine doses for ≥4 weeks were followed up for 1 year. Actions were taken to optimize therapy, and metabolite levels before and after the first action were documented. Outcomes assessed included SFR, no therapy escalation or surgery, healthcare resource utilization, and direct healthcare costs.

Results

Ninety IBD patients (50 Crohn's disease, 40 ulcerative colitis) were included. Among them, 40% had baseline metabolite levels within therapeutic range, 31.1% sub‐therapeutic, 21.1% supra‐therapeutic, and 7.8% shunters. Repeated MM with subsequent dose optimization helped 67.2% of patients achieve therapeutic levels after 1 year. Overall, 87.8% of patients achieved SFR and 90% had no therapy escalation or surgery. Despite greater outpatient visits and laboratory investigations with MM, the median total healthcare costs at 1 year only increased marginally (S$6407.66 [shunters] vs S$5215.20 [supra‐therapeutic] vs S$4970.80 [sub‐therapeutic] vs S$4370.48 [control (within therapeutic range)], P = 0.592).

Conclusion

MM guided timely therapy escalation for non‐responders, identification of non‐adherence, and reversal of shunting. Therefore, it is a useful clinical tool to optimize thiopurines without significantly increasing healthcare costs.

Impact of a pharmacist led thiopurine monitoring service in outpatients with inflammatory bowel disease

BACKGROUND

Thiopurines are effective therapies for inflammatory bowel disease (IBD), however treatment comes with safety concerns and adverse effects. Knowledge of the impact of pharmacists performing thiopurine monitoring is limited.

AIMS

To determine the impact of a pharmacist led monitoring service in patients with IBD commencing thiopurine therapy managed in the ambulatory care setting.

METHODS

Patients commencing thiopurine therapy for IBD pre and post introduction of a pharmacist led monitoring intervention were assessed. Pre-intervention patients received standard of care, while the post-intervention cohort were managed by the pharmacist. Data was acquired via retrospective audit of hospital medical records. The primary endpoint was the proportion of patients with documented review for thiopurine adverse effects within the initial three weeks. Secondary endpoints included achievement of therapeutic drug levels, persistence with thiopurine therapy, IBD related episodes of care and number of outpatient medical reviews.

RESULTS

Pre and post intervention cohorts comprised of 37 and 33 patients respectively. Pharmacist intervention increased the proportion of patients with documented monitoring within three weeks from 8.1% to 84.8% (p <0.01). No difference in thiopurine dose optimisation was seen (27% vs 27.3%). Persistence with thiopurine therapy increased from 65.7 to 87.9% (p <0.03) at six months. IBD related emergency department presentations were not significantly decreased (8.1% vs 3%, p=0.62). No significant change was observed in hospital admissions (16.2% vs 12.1%, p=0.74) or outpatient medical reviews.

CONCLUSIONS

Pharmacist monitoring of thiopurine therapy initiation in IBD outpatients improves adverse effect monitoring and increases medication persistence. This article is protected by copyright. All rights reserved.

Thiopurine Monotherapy Is Effective in Maintenance of Mild-Moderate Inflammatory Bowel Disease

BACKGROUND

Crohn's disease (CD) and ulcerative colitis (UC) are complex, inflammatory bowel diseases (IBD) with debilitating complications. While severe IBD typically requires biologic agents, the optimal therapy for mild-moderate IBD is less clear.

AIMS

To assess the efficacy of thiopurine monotherapy for maintenance of mild-moderate IBD and clinical variables associated with treatment outcome.

METHODS

This retrospective study included adults with mild-moderate IBD who were started on thiopurines without biologic therapy. The primary outcome was therapy failure, defined by disease progression based on clinical, endoscopic, and radiologic criteria. Clinical variables were extracted at time of thiopurine initiation. Univariable and multivariable Cox proportional hazards models were used to examine the independent contribution of the clinical variables on treatment response.

RESULTS

From 230 CD patients, 64 (72%) were free of treatment failure with mean follow-up of 3.3 years. In our multivariable model, thiopurine failure was associated with concomitant systemic steroid administration (aHR 2.43, p = 0.001), whereas protective factors included concomitant oral 5-aminosalicylic acid (5-ASA) therapy (aHR 0.54, p = 0.02) and non-fistulizing, non-stricturing disease (aHR 0.57, p = 0.047). From 173 UC patients, 50 (71%) were free from treatment failure with mean follow-up of 3.3 years. On multivariable analysis, concomitant oral steroids were associated with thiopurine failure (aHR 2.71, p = 0.001). Only 13 (4%) discontinued thiopurines from adverse effects.

CONCLUSIONS

In mild-moderate uncomplicated IBD, thiopurine monotherapy was associated with longitudinal maintenance of remission and may represent a lower-cost, convenient, and effective alternative to biologics. Multiple clinical variables were predictive of treatment response.

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.

Low-Dose Azathioprine in Combination with Allopurinol: The Past, Present and Future of This Useful Duo

The inflammatory bowel diseases (IBD) are complex immune-mediated inflammatory diseases that are associated with significant morbidity around the world. As our understanding of IBD, and other immune-mediated inflammatory diseases, advances the number of therapeutic targets has increased which has rapidly driven the development and introduction of new therapies. While these new therapies have shown promise they come with the significant drawback of high costs. For many IBD patients around the world the cost of newer therapies is prohibitive which means treating clinicians often need to turn to optimising simpler, older, and inexpensive medications. The concept of optimising well established cheaper medications is not unique to the management of IBD as health systems all over the world look to reduce costs while simultaneously improving patient outcomes. Despite thiopurines being used in the management IBD for over 60 years, many clinicians are still hesitant to use them due to perceptions around limited efficacy and poor tolerance. One method identified to potentially increase utilisation of thiopurines involves the coadministration of allopurinol. In this review we will explore the history, pharmacology, recent studies and give recommendations for the utilisation of the usual duo of azathioprine combined with allopurinol.

Immunosuppressants and immune modulators in luminal gastroenterology

Heritage small molecule immunosuppressants and the immune-acting biologics have a major place in the management of luminal gastrointestinal disease and especially so in inflammatory bowel disease. This narrative review considers their current use, concentrating on issues not already well addressed in the literature. An evidence-based approach is taken, supplemented by advice based on observations from clinical practice when data are missing. There is a general trend towards earlier use of the biologics for perceived greater safety and impact on disease modification, despite their substantially greater cost and systemic administration. Early semi-prophylactic treatment is now considered for patients with high-risk Crohn's disease. In other conditions the immune active agents remain a back-up for those failing to respond to simpler options. There are few and mostly unimportant differences between the different antibodies to TNFα, but it is beginning to be possible to identify patients who could be preferentially treated with an anti-integrin approach or by addressing other cytokines.

First United Arab Emirates consensus on diagnosis and management of inflammatory bowel diseases: A 2020 Delphi consensus

Ulcerative colitis and Crohn’s disease are the main entities of inflammatory bowel disease characterized by chronic remittent inflammation of the gastrointestinal tract. The incidence and prevalence are on the rise worldwide, and the heterogeneity between patients and within individuals over time is striking. The progressive advance in our understanding of the etiopathogenesis coupled with an unprecedented increase in therapeutic options have changed the management towards evidence-based interventions by clinicians with patients. This guideline was stimulated and supported by the Emirates Gastroenterology and Hepatology Society following a systematic review and a Delphi consensus process that provided evidence- and expert opinion-based recommendations. Comprehensive up-to-date guidance is provided regarding diagnosis, evaluation of disease severity, appropriate and timely use of different investigations, choice of appropriate therapy for induction and remission phase according to disease severity, and management of main complications.

Association of NUDT15*3 and FPGS 2572C>T Variants with the Risk of Early Hematologic Toxicity During 6-MP and Low-Dose Methotrexate-Based Maintenance Therapy in Indian Patients with Acute Lymphoblastic Leukemia

Genetic variants influencing the pharmacokinetics and/or pharmacodynamics of the chemotherapeutic drugs used in Acute Lymphoblastic Leukemia (ALL) therapy often contribute to the occurrence of treatment related toxicity (TRT). In this study, we explored the association of candidate genetic variants with early hematological TRT (grade 3–4) occurring within the first 100 days of low-dose methotrexate and 6-mercaptopurine based maintenance therapy (n = 73). Fourteen variants in the following candidate genes were genotyped using allele discrimination assay by real-time PCR: ABCB1, DHFR, GGH, FPGS, MTHFR, RFC1, SLCO1B1, TPMT, and NUDT15. Methotrexate polyglutamate (MTXPG3-5) levels in red blood cells were measured by LC-MS/MS. Early hematological TRT (grade 3–4) was seen in 54.9% of patients. The NUDT15c.415T allele was associated with early TRT occurrence [HR: 3.04 (95% CI: 1.5–6.1); p = 0.007]. Sensitivity of early TRT prediction improved (from 30.7% to 89.7%) by considering FPGS variant (rs1544105’T’) carrier status along with NUDT15c.415T allele [HR = 2.7 (1.5–4.7, p = 0.008)]. None of the considered genetic variants were associated with MTXPG3-5 levels, which in turn were not associated with early TRT. NUDT15c.415T allele carrier status could be used as a stratifying marker for Indian ALL patients to distinguish patients at high or low risk of developing early hematological TRT.

How, When, and for Whom Should We Perform Therapeutic Drug Monitoring?

The implementation of therapeutic drug monitoring (TDM) in the inflammatory bowel disease practice has evolved over the years. In the early days, the focus was merely on measuring and reporting drug concentrations. Later, these concentrations were considered in light of target concentrations that are related to clinical response. This not only allowed passively predicting a patient's future response, but it also triggered physicians and pharmacists to actively use the information to optimize the drug dosage to induce and maintain a clinical response in the future. Although reactive TDM, testing at time of loss of response, is widely accepted in practice, especially for anti-tumor necrosis factor antibodies, there are less data for the other monoclonal antibodies belonging to other classes. Besides reactive testing, there is a movement toward proactively adjusting biologic dosing to prevent loss of response, in keeping with the tight control philosophy of inflammatory bowel disease care. This review highlights the various assays available to measure drug concentrations and antidrug antibodies, as well as algorithmic approaches to TDM, the unmet needs and required studies to enable pharmacokinetics principles to be applied in the future.

Real-World Use of Azathioprine Metabolites Changes Clinical Management of Inflammatory Bowel Disease

Background

Thiopurines such as 6-mercaptopurine and azathioprine have complex metabolism, resulting in significant inter-individual differences in clinical efficacy and risk of drug toxicity, making conventional weight-based dosing inaccurate and potentially unsafe. Therapeutic drug monitoring (TDM) of thiopurine metabolites improves clinical outcomes through dose optimization and toxicity monitoring. Despite evidence for TDM, use is limited, due in part to test availability and awareness. The objectives of this study were twofold: (1) to investigate how thiopurine TDM impacts clinical management of IBD patients and (2) to evaluate proportion of patients outside therapeutic 6TGN levels or exhibiting signs of toxicity

Methods

Patients who received thiopurine TDM as part of routine care underwent chart review of demographics, disease activity, medication dosing, metabolite levels, and adverse events. Changes in clinical management following TDM were measured. Additionally, we conducted a retrospective review of clinical decision making blinded and unblinded to TDM result.

Results

A total of 92 IBD patients were included. Levels of 6TGN were therapeutic in 29% of patients. 6TGN levels correlated weakly with weight-based dosing (r² = 0.057, P = 0.02). Adverse reactions were observed in 6.5%. TDM informed clinical management in 64%. Significantly more changes to clinical management occurred in those with active disease than in remission (73% versus 48%; P = 0.02) and in those on mono- versus combination therapy (48% versus 27.5%; P = 0.03).

Conclusions

TDM informs clinical decision making in over two-thirds of patients. The demonstrated poor efficacy of weight-based dosing and impact of TDM on clinical management contributes to the evidence supporting the need for greater availability and uptake of thiopurine TDM.

Review article: determination of the therapeutic range for therapeutic drug monitoring of adalimumab and infliximab in patients with inflammatory bowel disease

BACKGROUND

Clinical application of therapeutic drug monitoring (TDM) to optimise anti-TNF therapies in patients with IBD depends upon target ranges.

AIMS

To review methodology used to determine therapeutic ranges and critically compare and contrast its application to infliximab and adalimumab.

METHODS

A systematic review was performed, and relevant literature was summarised and critically examined.

RESULTS

Upper limits of the therapeutic range are determined by toxicity, a plateau response and cost. Lower limits are determined by optimal concentration on the target of action in vitro and/or in vivo, or by correlation of drug levels with clinical efficacy using area-under-receiver-operator-curve (AUROC) analysis. In 43 studies, there were huge variations in time at which infliximab and adalimumab levels were measured, the end-points used (clinical remission to mucosal healing), the clinical setting (active disease vs maintenance phase) and the reason for TDM (proactive vs reactive). In the maintenance phase for infliximab, lower trough limits 2.8-5.7 µg/mL are reported depending upon end-points used, with consistent AUROC 0.68-0.77. Adalimumab TDM targets are even less consistent with a lower limit 5.9-11.8 µg/mL (AUROC 0.66-0.83) in some studies, but no cut-off can be identified that is significantly associated with outcome in others, related to inherent pharmacokinetic and pharmacodynamic differences, and heterogeneity of study design.

CONCLUSIONS

Evidence for exposure-response relationship is stronger for infliximab than adalimumab. Due to heterogeneity in settings for drug level measurements, therapeutic ranges vary. These factors need to be taken into account when interpreting the evidence and extending this to therapeutic strategies for IBD patients.

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.

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

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

Best practices on immunomodulators and biologic agents for ulcerative colitis and Crohn's disease in Asia

The Asia-Pacific Working Group on Inflammatory Bowel Disease was established in Cebu, Philippines, under the auspices of the Asia-Pacific Association of Gastroenterology with the goal of improving inflammatory bowel disease care in Asia. This consensus is carried out in collaboration with Asian Organization for Crohn's and Colitis. With biologic agents and biosimilars becoming more established, it is necessary to conduct a review on existing literature and establish a consensus on when and how to introduce biologic agents and biosimilars in conjunction with conventional treatments for ulcerative colitis and Crohn's disease in Asia. These statements also address how pharmacogenetics influences the treatments of ulcerative colitis and Crohn's disease and provides guidance on response monitoring and strategies to restore loss of response. Finally, the review includes statements on how to manage treatment alongside possible hepatitis B and tuberculosis infections, both common in Asia. These statements have been prepared and voted upon by members of inflammatory bowel disease workgroup employing the modified Delphi process. These statements do not intend to be all-encompassing, and future revisions are likely as new data continue to emerge.

Variations in Insurance Policies Regarding Adherence to the AGA Guideline for Therapeutic Drug Monitoring in IBD

BACKGROUND

The American Gastroenterological Association (AGA) published guidelines on therapeutic drug monitoring (TDM) in inflammatory bowel disease (IBD) in August 2017 recommending use of reactive TDM to guide treatment changes in patients with active IBD who are being treated with anti-tumor necrosis factor (anti-TNF) agents or thiopurines. We sought to determine if changes in national clinical practice guidelines result in changes in health care insurance policies within 6 months of publication.

METHODS

Using the National Association of Insurance Commissioners Market Share Reports of the top 125 insurance companies by market share in 2016, we reviewed the largest 50 companies for their publicly available online policies regarding TDM of anti-TNF and thiopurine in IBD. For those with available policies, we looked for whether proactive and/or reactive TDM was covered. Policies were also looked for genetic or enzymatic activity of thiopurine methyltransferase (TPMT) testing before use of thiopurine. All these policies were reviewed within the week of publication of the AGA guideline. They were reviewed again 1, 3, and 6 months later for evaluation of any policy changes after the published AGA guidelines.

RESULTS

Fifty of the largest insurance company policies were included. With regards to TDM policy for anti-TNF, we did not find a difference between baseline and 6 months values (P=0.38). With regards to TDM policy for thiopurine, we did not find a difference between baseline and 6 months values (P=1.00). About half of the companies did not have a policy regarding TPMT testing for thiopurine use. Of those with available policies for TPMT testing, there was no difference between baseline and 6 months values (P=0.13).

CONCLUSIONS

Even after publication of national guidelines, a large number of the largest health insurance companies do not have a policy regarding reactive TDM for anti-TNF and/or thiopurines. Majority of those with a policy, fail to meet the current standards set forth by the practice guidelines. A significant gap remains between the insurance policies and AGA guidelines. Further studies are needed to determine how to effectuate change to improve insurance company adherence to clinical practice guidelines.

Best practices on immunomodulators and biologic agents for ulcerative colitis and Crohn's disease in Asia

The Asia-Pacific Working Group on inflammatory bowel disease (IBD) was established in Cebu, Philippines, under the auspices of the Asian Pacific Association of Gastroenterology with the goal of improving IBD care in Asia. This consensus is carried out in collaboration with Asian Organization for Crohn’s and Colitis. With biologic agents and biosimilars becoming more established, it is necessary to conduct a review on existing literature and establish a consensus on when and how to introduce biologic agents and biosimilars in the conjunction with conventional treatments for ulcerative colitis (UC) and Crohn’s disease (CD) in Asia. These statements also address how pharmacogenetics influence the treatments of UC and CD and provide guidance on response monitoring and strategies to restore loss of response. Finally, the review includes statements on how to manage treatment alongside possible hepatitis B and tuberculosis infections, both common in Asia. These statements have been prepared and voted upon by members of IBD workgroup employing the modified Delphi process. These statements do not intend to be all-encompassing and future revisions are likely as new data continue to emerge.

Azathioprine dosing and metabolite measurement in pediatric inflammatory bowel disease: does one size fit all?

Background

Azathioprine is widely used for the maintenance of remission in children with inflammatory bowel disease (IBD). Measuring thiopurine metabolites 6-thioguanine (6-TGN) and 6-methyl-mercaptopurine (6-MMP) can aid in optimizing treatment and preventing toxicity. We report a proactive approach combining early metabolite measurements with IBD activity index to achieve optimal azathioprine dosing.

Methods

The reporting of azathioprine dosing, IBD activity indexes and thiopurine metabolites was evaluated retrospectively in 40 children with IBD. Additional treatments and the effect of azathioprine on blood counts were also examined.

Results

Forty children (40% female) with IBD (26 Crohn's disease, 12 ulcerative colitis, and 2 unclassified IBD), mean age 12.2±3.4 years, were included in the study. The mean azathioprine dose was 1.3±0.4 mg/kg; mean 6-TGN level was 280±151 pmol/8 × 10⁸ red blood cells (RBC) and mean 6-MMP level 1022±1007 pmol/8 × 10⁸ RBC. Disease activity index (Crohn's and ulcerative colitis, pediatric specific) at the time of metabolite measurement was 6.5±8. Twenty-eight children did not require azathioprine dose adjustment, while it was increased in 12. Data from children with azathioprine monotherapy were analyzed separately and the results were similar.

Conclusion

Timely measurement of thiopurine metabolites and clinical assessment can provide a powerful tool to optimize azathioprine dosing and reduce serious adverse effects in children with IBD.

Do clinical and laboratory parameters predict thiopurine metabolism and clinical outcome in patients with inflammatory bowel diseases?

PURPOSE

The thiopurines azathioprine and 6-mercaptopurine are frequently used for remission maintenance in patients with inflammatory bowel diseases. However, there are therapy failures, and it is unclear whether clinical and laboratory parameters can be used to predict thiopurine metabolite concentrations (as a surrogate for adequate remission maintenance therapy) and clinical outcome in these patients.

METHODS

In this retrospective analysis of clinical routine patient data, multivariate statistical models based on Linear Mixed Models regression and Generalized Estimating Equations logistic regression were developed. The adequacy of the models was assessed using Pearson's correlation and a receiver operating characteristic curve.

RESULTS

This study included 273 patients and 1158 thiopurine metabolite measurements as well as routine laboratory and clinical data. In the statistical models, thiopurine metabolite concentrations and the odds of non-remission based on different clinical and laboratory parameters were computed. Correlation (r²) between predicted and measured thiopurine metabolites were 0.40 (p < 0.001) for 6-thioguanine nucleotides and 0.53 (p < 0.001) for 6-methyl-mercaptopurine nucleotides, respectively. The model for remission classified data sets in remission and non-remission with a sensitivity of 63% and a specificity of 73%. The area under the receiver operating characteristic curve of the model was 0.72.

CONCLUSIONS

Although the models are not yet accurate enough to be used in clinical routine, model-based prediction of thiopurine metabolite concentrations and of outcome is feasible. Until more accurate models are developed and validated, traditional therapeutic drug monitoring of thiopurine metabolites in patients with inflammatory bowel diseases under thiopurine therapy stays the best tool to individualize therapy.

Using insurance claims to predict and improve hospitalizations and biologics use in members with inflammatory bowel diseases

OBJECTIVE

Inflammatory Bowel Disease (IBD) is an inflammatory disorder of the gastrointestinal tract that can necessitate hospitalization and the use of expensive biologics. Models predicting these interventions may improve patient quality of life and reduce expenditures.

MATERIALS AND METHODS

We used insurance claims from 2011 to 2013 to predict IBD-related hospitalizations and the initiation of biologics. We derived and optimized our model from a 2011 training set of 7771 members, predicting their outcomes the following year. The best-performing model was then applied to a 2012 validation set of 7450 members to predict their outcomes in 2013.

RESULTS

Our models predicted both IBD-related hospitalizations and the initiation of biologics, with average positive predictive values of 17% and 11%, respectively - each a 200% improvement over chance. Further, when we used topic modeling to identify four member subpopulations, the positive predictive value of predicting hospitalization increased to 20%.

DISCUSSION

We show that our hospitalization model, in concert with a mildly-effective interventional treatment plan for members identified as high-risk, may both improve patient outcomes and reduce insurance expenditures.

CONCLUSION

The success of our approach provides a roadmap for how claims data can complement traditional medical decision making with personalized, data-driven predictive medicine.

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.

Thiopurine Treatment in Ulcerative Colitis: A Critical Review of the Evidence for Current Clinical Practice

BACKGROUND

Due to toxicity problems and controversial evidence, thiopurine use in ulcerative colitis (UC) has faced a lot of criticism. We present a critical review of the literature on efficacy of thiopurines in UC.

METHODS

Studies evaluating therapeutic efficacy of thiopurine remission induction and/or maintenance treatment in UC were identified using the Cochrane Library, MEDLINE, and EMBASE.

RESULTS

Out of 5 randomized trials on thiopurine induction treatment, 3 demonstrated a significant effect of thiopurine treatment vs mesalamine or placebo in steroid-dependent UC patients: (1) lower endoscopic activity scores, (2) higher clinical remission rates, and (3) more patients who discontinued steroids. Two found no significant difference in clinical and endoscopic remission of azathioprine compared with sulfasalazine or placebo in patients with active UC. Out of 7 randomized trials on thiopurine maintenance treatment, 4 demonstrated significant higher clinical and endoscopic remission rates in thiopurine-treated patients compared with placebo or mesalamine. Three found no significant difference in clinical and endoscopic remission of thiopurine maintenance treatment compared with sulfasalazine or placebo.

CONCLUSIONS

All studies that investigated thiopurine treatment in UC had shortcomings, such as lack of sufficient power, no use of blinding, allowed concomitant treatment with steroids, and no endoscopy to confirm active disease at study entry or to evaluate therapeutic efficacy. Hence, current clinical practice of thiopurine treatment in UC is based on minimal and controversial evidence. This underscores the need for clinical studies with sufficient power and objective end points in order to determine efficacy of thiopurines in UC.

Rac1 as a Potential Pharmacodynamic Biomarker for Thiopurine Therapy in Inflammatory Bowel Disease

BACKGROUND

Azathioprine and mercaptopurine (MP) are effective in treating patients with inflammatory bowel disease (IBD). Immunosuppressive effects of thiopurines involve T-cell apoptosis after inhibition of GTPase Ras-related C3 botulinum toxin substrate 1 (Rac1). This study aimed to assess whether expression and activity of Rac1 or phosphorylated ezrin-radixin-moesin (pERM) in patients with IBD could provide a useful biomarker for the pharmacodynamic thiopurine effect and might be related to clinical effectiveness.

METHODS

This was a 2-stage study: stage 1 concerned a cross-sectional cohort of patients with IBD clinically in remission and treated with (n = 10) or without stable weight-based thiopurine therapy (n = 11) and healthy controls (n = 6); stage 2 concerned a prospective study regarding IBD patients with clinically active disease who initiated MP therapy (n = 11) compared with healthy controls (n = 11). Expression and activity of Rac1 and ERM and pERM were determined.

RESULTS

The median Rac1 expression was statistically significantly reduced by thiopurine maintenance therapy {0.54 [interquartile range (IQR) 0.47-0.88] versus 0.80 arbitrary units [IQR 0.64-1.46]} compared with patients without immunosuppressive therapy (P = 0.042), but not Rac1 activity and pERM. In responders to MP therapy (n = 6), both median active Rac1 [93 (IQR 81-151) to 76 ng Rac1/mg protein (IQR 62-98)] and Rac1 expression [16.2 (8.8-29.4) to 1.5 arbitrary units (0.9-5.3)] decreased (P = 0.028). In nonresponders (n = 3), Rac1 expression and activity increased.

CONCLUSIONS

IBD patients treated with thiopurines had a lower expression of Rac1 compared with those not treated with thiopurine. Effective MP therapy led to decreasing concentrations of Rac1-GTP and Rac1 expression. Therefore, Rac1-GTP and expression of Rac1, but not phosphorylation of ERM, form potentially pharmacodynamic markers of therapeutic thiopurine effectiveness in patients with IBD.

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.

Medication adherence in inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic idiopathic inflammatory condition with intestinal and extraintestinal manifestations. Medications are the cornerstone of treatment of IBD. However, patients often adhere to medication poorly. Adherence to medications is defined as the process by which patients take their medications as prescribed. Treatment non-adherence is a common problem among chronic diseases, averaging 50% in developed countries and is even poorer in developing countries. In this review, we will examine the adherence data in IBD which vary greatly depending on the study population, route of administration, and methods of adherence measurement used. We will also discuss the adverse clinical outcomes related to non-adherence to medical treatment including increased disease activity, flares, loss of response to anti-tumor necrosis factor therapy, and so forth. There are many methods to measure medication adherence namely direct and indirect methods, each with their advantages and drawbacks. Finally, we will explore different intervention strategies to improve adherence to medications.

Rac Attack: Modulation of the Small GTPase Rac in Inflammatory Bowel Disease and Thiopurine Therapy

The incidence and prevalence of inflammatory bowel disease (IBD) are increasing. Although the etiology of IBD is unknown, it is thought that genetically susceptible individuals display an inappropriate inflammatory response to commensal microbes, resulting in intestinal tissue damage. Key proteins involved in regulating the immune response, and thus in inflammation, are the small triphosphate-binding protein Rac and its regulatory network. Recent data suggest these proteins to be involved in (dys)regulation of the characteristic inflammatory processes in IBD. Moreover, Rac-gene variants have been identified as susceptibility risk factors for IBD, and Rac1 GTPase signaling has been shown to be strongly suppressed in non-inflamed mucosa compared with inflamed colonic mucosa in IBD. In addition, first-line immunosuppressive treatment for IBD includes thiopurine therapy, and its immunosuppressive effect is primarily ascribed to Rac1 suppression. In this review, we focus on Rac modification and its potential role in the development of IBD, Rac as the molecular therapeutic target in current thiopurine therapy, and the modulation of the Rac signal transduction pathway as a promising novel therapeutic strategy.

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.

American Gastroenterological Association Institute Technical Review on the Role of Therapeutic Drug Monitoring in the Management of Inflammatory Bowel Diseases

Therapeutic drug monitoring (TDM), which involves measurement of drug or active metabolite levels and anti-drug antibodies, is a promising strategy that can be used to optimize inflammatory bowel disease therapeutics. It is based on the premise that there is a relationship between drug exposure and outcomes, and that considerable inter-individual variability exists in how patients metabolize the drug (pharmacokinetics) and the magnitude and duration of response to therapy (pharmacodynamics). Therefore, the American Gastroenterological Association has prioritized clinical guidelines on the role of TDM in the management of inflammatory bowel disease. To inform these clinical guidelines, this technical review was developed in accordance with the GRADE (Grading of Recommendations Assessment, Development, and Evaluation) framework for interventional and prognostic studies, and focused on the application of TDM for biologic therapy, specifically anti-tumor necrosis factor-α agents, and for thiopurines. Focused questions address the benefits and risks of a strategy of reactive TDM (in patients with active inflammatory bowel disease) to guide treatment changes compared with empiric treatment changes, and the benefits and risks of a strategy of routine proactive TDM (during routine clinical care in patients with quiescent disease) compared with no routine TDM. Additionally, the review addresses the benefits and risks of routine measurement of thiopurine methyltransferase enzyme activity or genotype before starting thiopurine therapy compared with empiric weight-based dosing and explores the performance of different trough drug concentrations for anti-tumor necrosis factor agents and thiopurines to inform clinical decision making when applying TDM in a reactive setting. Due to a paucity of data, this review does not address the role of TDM for more recently approved biologic agents, such as vedolizumab or ustekinumab.

Thiopurines Dosed to a Therapeutic 6-Thioguanine Level in Combination with Adalimumab Are More Effective Than Subtherapeutic Thiopurine-based Combination Therapy or Adalimumab Monotherapy During Induction and Maintenance in Patients with Long-standing Crohn's Disease

BACKGROUND

The benefit of concomitant immunomodulation with adalimumab (ADA) in Crohn's disease is poorly understood. We aimed to compare ADA monotherapy with combination therapy with thiopurines, stratified by thioguanine nucleotides (TGNs).

METHODS

Retrospective observational study of ADA induction and maintenance. Thiopurines were classified according to TGNs (>235 pmol/8 × 10 red blood cell therapeutic).

RESULTS

At induction, response was more frequent in combination than ADA monotherapy (83% versus 61%, P = 0.02) and with therapeutic compared with subtherapeutic TGNs (87% versus 70% P = 0.011). Among 280 maintenance semesters in 91 patients, remission was higher with combination than monotherapy (81% versus 60%, P < 0.0001) and therapeutic versus subtherapeutic TGNs (85% versus 58%, P = 0.004). Therapeutic TGN (odds ratio [OR] 4.32, 95% CI, 1.41-13.29, P = 0.01) and albumin (OR 1.09, 95% CI, 1.01-1.18, P = 0.03) were predictors of response to induction. Therapeutic TGN (OR 3.71, 95% CI, 1.87-7.34, P < 0.0001) and ileal disease (OR 0.21, 95% CI, 0.08-0.57, P = 0.002) were predictors of remission semesters. Concomitant immunomodulation at induction was associated with longer time to failure (69 versus 36 months, P = 0.009). Therapeutic TGN at induction (P = 0.03) and male sex (P = 0.026) were associated with time to failure.

CONCLUSIONS

Combination therapy was superior to ADA monotherapy for induction and during maintenance. This benefit was increased further when thiopurines resulted in therapeutic TGNs. Early use of adequately dosed thiopurines (≥3 months before starting ADA) was associated with improved clinical outcomes.

Metabolite monitoring to guide thiopurine therapy in systemic autoimmune diseases

6-Thioguanine nucleotide (6-TGN) is the active metabolite of thiopurine drugs azathioprine and 6-mercaptopurine. 6-Methylmercaptopurine (6-MMP) is an inactive and potentially hepatotoxic metabolite. A subgroup of patients (shunters) preferentially produce 6-MMP instead of 6-TGN, therefore displaying thiopurine resistance and risk for hepatotoxicity. Outside inflammatory bowel disease literature, few data exist regarding individualized thiopurine therapy based on metabolite monitoring. This study sought to describe metabolite monitoring in patients receiving weight-based thiopurine for systemic autoimmune diseases. Patients were enrolled using a laboratory database, and data were retrospectively collected. The correlation between the highest thiopurine dose (mg/kg) and the 6-TGN concentration (pmol/8 × 10⁸ erythrocytes) was estimated with Pearson's correlation coefficient. Seventy-one patients with various systemic autoimmune conditions were enrolled. The correlation between the thiopurine dose and the 6-TGN level was weak for the overall patient sample (r = 0.201, p = 0.092) and for the subgroup of non-shunters (r = 0.278, p = 0.053). Subjects with 6-MMP levels >5700 pmol/8 × 10⁸ erythrocytes had more hepatic cytolysis compared to subjects with 6-MMP <5700, OR = 4.36 (CI 95% 1.18-16.13, p = 0.027). Twenty-two patients (31%) were identified as shunters. Six shunters developed hepatotoxicity, five of which had 6-MMP concentration >5700. Eleven non-shunters had hepatotoxicity, one of which had 6-MMP >5700. Thiopurine metabolite monitoring shows wide variability in 6-TGN levels among patients treated with weight-based thiopurine for systemic autoimmune diseases. Thirty-one percent of the patients in our series fulfilled the shunter definition. Thiopurine metabolite monitoring and dose adjustment to improve maintenance of remission and avoid hepatotoxicity should be studied prospectively.

Does lymphopenia or macrocytosis reflect 6-thioguanine levels in patients with inflammatory bowel disease treated with azathioprine or 6-mercaptopurine?

BACKGROUND

The thiopurine drugs, 6-mercaptopurine and azathioprine, remain the mainstay of immunomodulator therapy for inflammatory bowel disease (IBD). Optimal management depends on achieving therapeutic levels of 6-thioguanine (6-TGN), but measuring thiopurine metabolites is associated with significant cost. Thiopurines cause lymphopenia and an increase in mean corpuscular volume (MCV). It is unclear whether any clinically useful correlation exists between 6-TGN levels and lymphocyte count or MCV.

AIMS

The aim of this study is to investigate the correlation between 6-TGN levels and lymphocyte count and MCV in thiopurine-treated patients with IBD.

METHODS

We analysed a prospectively acquired database of 67 patients with IBD treated with thiopurine therapy. The data were analysed looking at the relationship between 6-TGN levels and both lymphocyte count and MCV by using the Spearman's rank correlation coefficient.

RESULTS

Twenty-seven (40%) patients had therapeutic 6-TGN levels. Thirty-three (49%) patients had sub-therapeutic 6-TGN levels. A weak positive correlation between 6-TGN levels and lymphocyte count was demonstrated, but this was not statistically significant (Spearman's R = 0.14, P = 0.23). Spearman's rank correlation coefficient between 6-TGN levels and MCV was statistically significant (R = 0.42, P = 0.0005). MCV >101 fL excluded a subtherapeutic 6-TGN level with positive predictive value of 92%.

CONCLUSIONS

There is no specific lymphopenia that can be assumed to indicate a therapeutic 6-TGN level. The relationship between 6-TGN levels and MCV is likely to be clinically relevant. If MCV is elevated, 6-TGN is unlikely to be sub-therapeutic. MCV is a potential surrogate marker which can rule out sub-therapeutic thiopurine metabolites in patients with IBD treated with azathioprine or 6-mercaptopurine.

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.

Weight and Body Composition Compartments do Not Predict Therapeutic Thiopurine Metabolite Levels in Inflammatory Bowel Disease

OBJECTIVES:

Thiopurine drugs are the most commonly used steroid-sparing therapies in moderate-to-severe inflammatory bowel disease (IBD). Their complex metabolism and their narrow therapeutic windows means that optimal dosing is difficult. However, weight-based dosing is the norm. Similar antimetabolites are dosed by body composition parameters. In IBD, treatment response and toxicity has been shown to correlate with thiopurine metabolite levels. We sought to determine whether weight or body composition parameters predicted therapeutic 6-thioguanine nucleotide (6TGN) or toxic 6-methylmercaptopurine (6MMP) levels.

METHODS:

This single-center retrospective cohort study identified 66 IBD patients who had body composition analysis and thiopurine metabolite levels tested. Statistical analysis was performed using Spearman correlation, Kruskal–Wallis, Mann–Whitney, and unpaired t tests and receiver-operator operating characteristic curves. A P value of <0.05 was considered significant.

RESULTS:

No correlation was identified between 6TGN and any body composition parameters, absolute drug dose or drug dose/kg of fat mass, fat-free mass (FFM), subcutaneous adipose tissue area, or visceral adipose tissue area. However, 6MMP correlated with azathioprine dose, thiopurine dose/kg of body weight, and with several body composition parameters.

CONCLUSIONS:

No relationship was found between therapeutic metabolite levels and weight or body composition compartments. Higher thiopurine doses, especially in relation to FFM, are associated with higher levels of potentially hepatotoxic 6MMP and shunting toward this metabolite. Conventional weight-based dosing to attain therapeutic metabolite levels appears unreliable and may be replaced by metabolite level testing.

Measurement of red blood cell 6-thioguanine nucleotide is beneficial in azathioprine maintenance therapy of Chinese Crohn's disease patients

OBJECTIVE

It remains controversial whether 6-thioguanine nucleotide (6-TGN)-based dose adjusting can be beneficial in azathioprine (AZA) therapy. This study is designed to assess the role of 6-TGN concentrations in maintaining clinical remission in Chinese patients with Crohn's disease (CD).

MATERIAL AND METHOD

We performed a prospective observational study and collected data of CD patients in the First Affiliated Hospital of Anhui Medical University from June 2013 to April 2014. Demographic material, CD activity index, 6-TGN concentration, and laboratory tests were recorded at baseline and at each visit. In addition, 6-TGN was measured when drug adverse effects occurred. All patients achieved maintenance stage were administered a stable AZA dose at least 3 months before enrollment and were followed up at least 12 months. Thiopurine S-methyltransferase (TPMT) genotype was measured before AZA treatment.

RESULTS

Sixty-nine patients receiving maintenance therapy were analyzed. A positive correlation was found between 6-TGN levels and AZA dose (r = 0.258, p = 0.032). The mean 6-TGN concentration was 302.06 ± 115.84 in the remission group vs. 264.94 ± 164.53 pmol/8 × 10(8) RBC in those with active disease (t = 0.847, p = 0.40), and 197.74 ± 66.54 pmol/8 × 10(8) RBC in patients who relapsed vs. 310.26 ± 122.38 pmol/8 × 10(8) RBC for those in sustained remission (t= -2.541, p = 0.013). In the leukopenia group, the 6-TGN concentration was 469.11 ± 115.53 pmol/8 × 10(8) RBC vs. 257.31 ± 83.74 pmol/8 × 10(8) RBC in the non-leukopenia group (t = 7.622, p < 0.001). There was a significant negative correlation between leukocyte count and 6-TGN concentration (r= -0.326, p = 0.006).

CONCLUSIONS

6-TGN measurement is a helpful method of preventing disease relapse and avoiding leukopenia in individual azathioprine maintenance therapy.

Usefulness of mean corpuscular volume as a surrogate marker for monitoring thiopurine treatment in inflammatory bowel disease

BACKGROUND

Thiopurines are commonly used drugs in inflammatory bowel disease. Intracellular levels of thiopurine metabolites [i.e. 6-thioguaninenucleotides (6-TGN)] are associated with efficacy and toxicity. Because 6-TGN measurement is not globally available, the mean corpuscular volume (MCV) has been proposed as a surrogate marker for monitoring thiopurine therapy.

AIMS

To analyze the relationship between MCV and efficacy of thiopurines, defined as either response to therapy or 6-TGN levels.

METHODS

A systematic search on PubMed was performed.

RESULTS

Fifteen studies were included. In six studies, a positive association was found between ΔMCV and 6-TGN. In four studies, it was suggested that ΔMCV can be used to predict clinical remission. In five articles, no association was found.

CONCLUSION

In the majority of articles, it was reported that ΔMCV is useful in guiding intracellular metabolite levels. However, there is insufficient evidence showing that ΔMCV can predict clinical remission.

Thiopurine metabolite testing in inflammatory bowel disease

BACKGROUND

Thiopurine use in inflammatory bowel disease (IBD) is limited by drug toxicity and lack of therapeutic efficacy. We assessed the utility of thiopurine metabolite testing and the relationship between disease activity, dose, and metabolite levels in a real world setting.

METHODS

Patients identified from pathology databases (2007-2012) at two tertiary IBD centers were included if they had thiopurines for at least four weeks. Demographics, dose, test indication, clinical status, action taken, and outcome were obtained by retrospective medical record review.

RESULTS

A total of 169 patients were included. 6-Thioguanine (TGN) levels were sub-therapeutic in 52%, therapeutic in 34%, and supratherapeutic in 14%. Test indication was active disease (79%), adverse effect (11%), or adherence assessment (7%). TGN trended lower in the active disease group compared to those with adverse effects (273 (+/- 23.2) versus 447 (+/- 117.7) pmol/8 × 10(8) RBC, P = 0.05). Weight-based dosing did not improve rates of therapeutic TGN levels (under-dosed 31.5% vs standard dose 35.4%), but was significantly associated with shunting toward 6-MMP (23.1% vs 6.8%, P = 0.008, OR = 4.1). Testing resulted in a change in patient treatment in 86% of patients with active disease and subtherapeutic levels and in 68% of tested patients overall.

CONCLUSIONS

Metabolite testing resulted in a change in management in most patients not responding to thiopurines or experiencing adverse events. Weight-based dosing did not increase rates of therapeutic levels but was associated with increased 6MMP shunting.

Getting the best out of thiopurine therapy: thiopurine S-methyltransferase and beyond

Thiopurines are the cornerstone of treatment for a wide variety of medical disorders, ranging from pediatric leukemia to inflammatory bowel disease. Because of their complex metabolism and potential toxicities, the use of biomarkers to predict risk and response is paramount. Thiopurine S-methyltransferase and thiopurine metabolite levels have emerged as companion diagnostics with crucial roles in facilitating safe and effective treatment. This review serves to update the reader on how these tools are being developed and implemented in clinical practice. A useful paradigm in thiopurine therapeutic strategy is presented, along with fresh insights into the mechanisms underlying these approaches. We elaborate on potential future developments in the optimization of thiopurine therapy.

Characteristics of azathioprine use and cessation in a longitudinal lupus cohort

Objective

Guidelines for azathioprine (AZA) use in systemic lupus erythematosus (SLE), including indications for initiation and cessation, are lacking. Clinical decision-making could be improved if reasons for cessation of AZA treatment were standardised.

Methods

We determined the characteristics of AZA use in a cohort of patients with SLE and evaluated reasons for AZA cessation. Patients with SLE in a single centre had longitudinal recording of disease activity (Systemic Lupus Erythematosus Disease Activity Index 2000 (SLEDAI)-2k), laboratory investigations and treatment from 2007 to 2012.

Results

Of 183 patients studied, 67 used AZA on at least one occasion. There was no significant difference between AZA users and non-users in age or American College of Rheumatology criteria. Compared with those not treated with AZA, patients treated with AZA had higher disease activity (time-adjusted mean SLEDAI 5.2±0.3 vs 3.8±0.3, p=0.0028) and damage (Systemic Lupus International Collaborating Clinics (SLICC)-SDI 1.6±0.3 vs 1.2±0.1, p=0.0445), and were more likely to have a positive dsDNA (p=0.0130) and receive glucocorticoids (p<0.0001). AZA therapy was ceased in 30/67 (45%) patients. The predominant reasons for cessation were treatment de-escalation 14 (47%), treatment failure 12 (40%) and toxicity 3 (10%). AZA was switched to mycophenolate mofetil (MMF) in 9/12 (75%) of treatment failures, and this choice was strongly associated with active lupus nephritis.

Conclusions

AZA toxicity was uncommon, and many patients ceased therapy in the context of treatment de-escalation. However, the frequent development of active lupus nephritis requiring MMF suggests the need to distinguish refractoriness, under-treatment and non-adherence to AZA in patients with SLE. These findings suggest that future studies of AZA metabolite measurement could prove valuable in the management of SLE.

Thiopurine monitoring in children with inflammatory bowel disease: a systematic review

AIMS

The aim was to systematically review the evidence on the clinical usefulness of thiopurine metabolite and white blood count (WBC) monitoring in the assessment of clinical outcomes in children with inflammatory bowel disease (IBD).

METHODS

Medline, Embase, Cochrane Central Register of controlled trials and http://www.clinicaltrials.gov were screened in adherence to the PRISMA statement by two independent reviewers for identification of eligible studies. Eligible studies were randomized controlled trials (RCTs), cohort studies and large case series of children with inflammatory bowel disease (IBD) (<18 years) who underwent monitoring of thiopurine metabolites and/or WBC.

RESULTS

Fifteen papers were identified (n = 1026). None of the eligible studies were RCTs. High 6-thioguanine nucleotide (6TGN) concentrations were not consistently associated with leucopenia. Leucopenia was not associated with achievement of clinical remission. A positive but not consistent correlation between 6TGN and clinical remission was reported. Haematological toxicity could not be reliably assessed with 6TGN measurements only. A number of studies supported the use of high 6-methylmercaptopurine ribonucleotides (6MMPR) as an indicator of hepatotoxicity. Low thiopurine metabolite concentration may be indicative of non-compliance.

CONCLUSION

Thiopurine metabolite testing does not safely predict clinical outcome, but may facilitate toxicity surveillance and treatment optimization in poor responders. Current evidence favours the combination of thiopurine metabolite/WBC monitoring and clinic follow-up for prompt identification of haematologic/hepatic toxicity safe dose adjustment, and treatment modification in cases of suboptimal clinical outcome or non-compliance. Well designed RCTs for the identification of robust surrogate markers of thiopurine efficacy and toxicity are required.