Interaction between azathioprine and aminosalicylates: an in vivo study in patients with Crohn's disease

Ulcerative Colitis in Adulthood and in Older Patients: Same Disease, Same Outcome, Same Risks?

The number of patients with inflammatory bowel disease (IBD) approaching an older age, together with the number of over-60-year-old patients newly diagnosed with IBD, is steadily increasing, reaching 25% of all patients. The present review focuses on late-onset ulcerative colitis (UC) and its initial disease course in comparison with that observed in younger adults in terms of extension at onset and the risk of proximal disease progression, medical treatment, surgery and hospitalization in the first years after diagnosis. We summarize the clues pointing to a milder disease course in a population which frequently presents major frailty due to comorbidities. With increasing age and thus increasing comorbidities, medical and surgical therapies frequently represent a challenge for treating physicians. The response, persistence, and risks of adverse events of conventional therapies indicated for late onset/older UC patients are examined, emphasizing the risks in this particular population, who are still being treated with prolonged corticosteroid therapy. Finally, we concentrate on data on biotechnological agents for which older patients were mostly excluded from pivotal trials. Real-life data from newer agents such as vedolizumab and ustekinumab show encouraging efficacy and safety profiles in the population of older UC patients.

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.

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

BACKGROUND

In inflammatory bowel disease (IBD), conventional thiopurine users cease treatment in 60% of cases within 5 years, mostly because of adverse events or nonresponse. In this study, the authors aimed to investigate the role of 6-thioguanine nucleotide (TGN) measurements, geno/phenotyping of thiopurine S-methyltransferase (TPMT), and their mutual relationship with TG therapy in IBD.

METHODS

An international retrospective, multicenter cohort study was performed at 4 centers in the Netherlands (Máxima Medical Centre) and the United Kingdom (Guy's and St. Thomas' Hospital, Queen Elizabeth Hospital, and East Surrey Hospital).

RESULTS

Overall, 526 6-TGN measurements were performed in 316 patients with IBD. The median daily dosage of TG was 20 mg/d (range 10-40 mg/d), and the median duration of TG use was 21.1 months (SD, 28.0). In total, 129 patients (40.8%) had a known TPMT status. In the variant-type and wild-type TPMT genotype metabolism groups, median 6-TGN values were 1126 [interquartile range (IQR) 948-1562] and 467.5 pmol/8 × 10E8 red blood cells (RBCs) (IQR 334-593). A significant difference was observed between the 2 groups (P = 0.0001, t test). For TPMT phenotypes, in the slow, fast, and normal metabolism groups, the median 6-TGN values were 772.0 (IQR 459-1724), 296.0 (IQR 200-705), and 774.5 pmol/8 × 10E8 RBCs (IQR 500.5-981.5), with a significant difference observed between groups (P < 0.001, analysis of variance).

CONCLUSIONS

Our findings indicated that TPMT measurements at TG initiation can be useful but are not necessary for daily practice. TPMT genotypes and phenotypes are both associated with significant differences in 6-TGN levels between metabolic groups. However, the advantage of TG remains that RBC 6-TGN measurements are not crucial to monitor treatments in patients with IBD because these measurements did not correlate with laboratory result abnormalities. This presents as a major advantage in countries where patients cannot access these diagnostic tests.

Advances in Thiopurine Drug Delivery: The Current State-of-the-Art

Thiopurines (mercaptopurine, azathioprine and thioguanine) are well-established maintenance treatments for a wide range of diseases such as leukemia, inflammatory bowel disease (IBD), systemic lupus erythematosus (SLE) and other inflammatory and autoimmune diseases in general. Worldwide, millions of patients are treated with thiopurines. The use of thiopurines has been limited because of off-target effects such as myelotoxicity and hepatotoxicity. Therefore, seeking methods to enhance target-based thiopurine-based treatment is relevant, combined with pharmacogenetic testing. Controlled-release formulations for thiopurines have been clinically tested and have shown promising outcomes in inflammatory bowel disease. Latest developments in nano-formulations for thiopurines have shown encouraging pre-clinical results, but further research and development are needed. This review provides an overview of novel drug delivery strategies for thiopurines, reviewing modified release formulations and with a focus on nano-based formulations.

Clinical Considerations Regarding the Use of Thiopurines in Older Patients with Inflammatory Bowel Disease

The number of older patients with inflammatory bowel disease (IBD) is increasing due to both improvements in the life expectancy of patients with long-lasting IBD and later onset of the disease. In spite of a less aggressive IBD phenotype, disease management in older patients is hampered by comorbidities and polypharmacy (which increase the risk of drug-related adverse events and errors in medication intake) and also by an increased risk of the infections and malignancies associated with the immunosuppressive drugs that are frequently used to treat IBD. Thiopurines are the most frequently used immunosuppressive drugs in IBD, though they are often discontinued due to adverse events. However, when tolerated, thiopurines are efficient in the maintenance of remission in ulcerative colitis and Crohn's disease. In fact, thiopurines still have a role to play in the treatment algorithm of older patients with IBD because anti-tumor necrosis factor agents do not provide clear advantages for this population in terms of their safety profile, while data on the new biological drugs are still scarce. In this article, we review the optimal use of thiopurines in older patients with IBD.

Review article: opportunities to improve and expand thiopurine therapy for autoimmune hepatitis

BACKGROUND

Thiopurines in combination with glucocorticoids are used as first-line, second-line and maintenance therapies in autoimmune hepatitis and opportunities exist to improve and expand their use.

AIMS

To describe the metabolic pathways and key factors implicated in the efficacy and toxicity of the thiopurine drugs and to indicate the opportunities to improve outcomes by monitoring and manipulating metabolic pathways, individualising dosage and strengthening the response.

METHODS

English abstracts were identified in PubMed by multiple search terms. Full-length articles were selected for review, and secondary and tertiary bibliographies were developed.

RESULTS

Thiopurine methyltransferase activity and 6-tioguanine (6-thioguanine) nucleotide levels influence drug efficacy and safety, and they can be manipulated to improve treatment response and prevent myelosuppression. Methylated thiopurine metabolites are associated with hepatotoxicity, drug intolerance and nonresponse and their production can be reduced or bypassed. Universal pre-treatment assessment of thiopurine methyltransferase activity and individualisation of dosage to manipulate metabolite thresholds could improve outcomes. Early detection of thiopurine resistance by metabolite testing, accurate estimations of drug onset and strength by surrogate markers and adjunctive use of allopurinol could improve the management of refractory disease. Dose-restricted tioguanine (thioguanine) could expand treatment options by reducing methylated metabolites, increasing the bioavailability of 6-tioguanine nucleotides and ameliorating thiopurine intolerance or resistance.

CONCLUSIONS

The efficacy and safety of thiopurines in autoimmune hepatitis can be improved by investigational efforts that establish monitoring strategies that allow individualisation of dosage and prediction of outcome, increase bioavailability of the active metabolites and demonstrate superiority to alternative agents.

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.

Clinical Pharmacokinetic and Pharmacodynamic Considerations in the Treatment of Inflammatory Bowel Disease

According to recent clinical consensus, pharmacotherapy of inflammatory bowel disease (IBD) is, or should be, personalized medicine. IBD treatment is complex, with highly different treatment classes and relatively few data on treatment strategy. Although thorough evidence-based international IBD guidelines currently exist, appropriate drug and dose choice remains challenging as many disease (disease type, location of disease, disease activity and course, extraintestinal manifestations, complications) and patient characteristics [(pharmaco-)genetic predisposition, response to previous medications, side-effect profile, necessary onset of response, convenience, concurrent therapy, adherence to (maintenance) therapy] are involved. Detailed pharmacological knowledge of the IBD drug arsenal is essential for choosing the right drug, in the right dose, in the right administration form, at the right time, for each individual patient. In this in-depth review, clinical pharmacodynamic and pharmacokinetic considerations are provided for tailoring treatment with the most common IBD drugs. Development (with consequent prospective validation) of easy-to-use treatment algorithms based on these considerations and new pharmacological data may facilitate optimal and effective IBD treatment, preferably corroborated by effectiveness and safety registries.

Increased risk of thiopurine-related adverse events in elderly patients with IBD

BACKGROUND

Thiopurines are the most widely used immunosuppressants in IBD although drug-related adverse events (AE) occur in 20%-30% of cases.

AIM

To evaluate the safety of thiopurines in elderly IBD patients METHODS: Cohort study including all adult patients in the ENEIDA registry who received thiopurines. Patients were grouped in terms of age at the beginning of thiopurine treatment, specifically in those who started thiopurines over 60 years or between 18 and 50 years of age. Thiopurine-related AEs registered in the ENEIDA database were compared.

RESULTS

Out of 48 752 patients, 1888 started thiopurines when over 60 years of age and 15 477 under 50 years of age. Median treatment duration was significantly shorter for those who started thiopurines >60 years (13 [IQR 2-55] vs 32 [IQR 5-82] months; P < .001). Patients starting >60 years had higher rates of all types of myelotoxicity, digestive intolerance and hepatotoxicity. Thiopurines were discontinued due to AEs (excluding malignancies and infections) in more patients starting >60 years (67.2% vs 63.1%; P < .001). Elderly age and female sex were independent risk factors for most AEs.

CONCLUSION

In elderly IBD patients, thiopurines are associated with an increased risk of non-infectious, non-neoplastic, AEs.

Combined evaluation of genotype and phenotype of thiopurine S-methyltransferase (TPMT) in the clinical management of patients in chronic therapy with azathioprine

Background The thiopurine S-methyltransferase (TPMT)/azathioprine (AZA) gene-drug pair is one of the most well-known pharmacogenetic markers. Despite this, few studies investigated the implementation of TPMT testing and the combined evaluation of genotype and phenotype in multidisciplinary clinical settings where patients are undergoing chronic therapy with AZA. Methods A total of 356 AZA-treated patients for chronic autoimmune diseases were enrolled. DNA was isolated from whole blood and the samples were analyzed for the c.460G>A and c.719A>G variants by the restriction fragment length polymorphism (RFLP) technique and sequenced for the c.238G>C variant. The TPMT enzyme activity was determined in erythrocytes by a high-performance liquid chromatography (HPLC) assay. Results All the patients enrolled were genotyped while the TPMT enzyme activity was assessed in 41 patients. Clinical information was available on 181 patients. We found no significant difference in the odds of having adverse drug reactions (ADRs) in wild-type patients and variant allele carriers, but the latter had an extra risk of experiencing hematologically adverse events. The enzyme activity was significantly associated to genotype. Conclusions TPMT variant allele carriers have an extra risk of experiencing hematologically adverse events compared to wild-type patients. Interestingly, only two out of 30 (6.6%) patients had discordant results between genotype, phenotype and onset of ADRs.

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

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

Late-onset Rise of 6-MMP Metabolites in IBD Patients on Azathioprine or Mercaptopurine

BACKGROUND

The thiopurines azathioprine and mercaptopurine remain pivotal maintenance treatments in inflammatory bowel disease (IBD); however, up to 15%-20% of patients preferentially produce the hepatotoxic metabolite 6-methylmercaptopurine (6MMP) at the expense of the therapeutic 6-thioguanine nucleotides (6TGN). This metabolic shunting usually begins within 3 months of therapy. We noted patients developing shunting many months or years after starting treatment and aimed to determine how often this late shunting occurs and whether this could be explained by patient factors or concomitant medications.

METHODS

The New Zealand database of thiopurine metabolite results from 2002 to 2016 (19085 6TGN/6MMP pairs from 7130 patients) was interrogated to identify patients developing a 6MMP/6TGN ratio >20 after at least 4 months treatment. Dosing history, concomitant therapy, and comorbidity data were assessed.

RESULTS

Fifteen percent of database patients developed preferential 6-MMP production, and of these, 29 patients had late-onset shunting with sufficient data available for validation. This extrapolates to 90 patients in total, representing 1.7% of IBD patients on thiopurines, or 10% of all those with preferential 6-MMP production. Time from starting therapy to shunting was 5 months to 10.4 years (median, 21 months). Eleven patients had abnormal liver function when shunting was recognized, all with 6MMP >5900 pmol/8 × 108 red blood cells. No common factors were found to explain the late onset.

CONCLUSIONS

Some IBD patients develop preferential 6MMP production many months or years after commencing therapy. This is important when considering frequency of metabolite monitoring, failure of therapy, or abnormal liver function. 10.1093/ibd/izx081_video1izx081.video15746667546001.

Recommendations of the Spanish Working Group on Crohn's Disease and Ulcerative Colitis (GETECCU) on the use of thiopurines in inflammatory bowel disease

Thiopurines (azathioprine and mercaptopurine) are widely used in patients with inflammatory bowel disease. In this paper, we review the main indications for their use, as well as practical aspects on efficacy, safety and method of administration. They are mainly used to maintain remission in steroid-dependent disease or with ciclosporin to control a severe ulcerative colitis flare-up, as well as to prevent postoperative Crohn's disease recurrence, and also in combination therapy with biologics. About 30-40% of patients will not respond to treatment and 10-20% will not tolerate it due to adverse effects. Before they are prescribed, immunisation status against certain infections should be checked. Determination of thiopurine methyltransferase activity (TPMT) is not mandatory but it increases initial safety. The appropriate dose is 2.5mg/kg/day for azathioprine and 1.5mg/kg/day for mercaptopurine. Some adverse effects are idiosyncratic (digestive intolerance, pancreatitis, fever, arthromyalgia, rash and some forms of hepatotoxicity). Others are dose-dependent (myelotoxicity and other types of hepatotoxicity), and their surveillance should never be interrupted during treatment. If therapy fails or adverse effects develop, management can include switching from one thiopurine to the other, reducing the dose, combining low doses of azathioprine with allopurinol and assessing metabolites, before their use is ruled out. Non-melanoma skin cancer, lymphomas and urinary tract tumours have been linked to thiopurine therapy. Thiopurine use is safe during conception, pregnancy and breastfeeding.

Safety of treatments for inflammatory bowel disease: Clinical practice guidelines of the Italian Group for the Study of Inflammatory Bowel Disease (IG-IBD)

Inflammatory bowel diseases are chronic conditions of unknown etiology, showing a growing incidence and prevalence in several countries, including Italy. Although the etiology of Crohn's disease and ulcerative colitis is unknown, due to the current knowledge regarding their pathogenesis, effective treatment strategies have been developed. Several guidelines are available regarding the efficacy and safety of available drug treatments for inflammatory bowel diseases. Nevertheless, national guidelines provide additional information adapted to local feasibility, costs and legal issues related to the use of the same drugs. These observations prompted the Italian Group for the Study of Inflammatory Bowel Disease (IG-IBD) to establish Italian guidelines on the safety of currently available treatments for Crohn's disease and ulcerative colitis. These guidelines discuss the use of aminosalicylates, systemic and low bioavailability corticosteroids, antibiotics (metronidazole, ciprofloxacin, rifaximin), thiopurines, methotrexate, cyclosporine A, TNFα antagonists, vedolizumab, and combination therapies. These guidelines are based on current knowledge derived from evidence-based medicine coupled with clinical experience of a national working group.

Physician Perspectives on Unresolved Issues in the Management of Ulcerative Colitis: The UC Horizons Project

BACKGROUND

There is still uncertainty about what constitutes the best therapeutic practice in ulcerative colitis (UC).

OBJECTIVE

The purpose of the "UC Horizons Project" was to raise a series of questions regarding the management of UC to provide responses based on the best scientific evidence available.

METHODS

The 11 members of the scientific committee prepared draft answers to the 10 questions from available evidence after a literature search. A total of 48 Spanish gastroenterology specialists nationwide participated in the project. The national meeting discussed the 10 issues in working groups and reached consensus regarding the recommendations by anonymous, interactive vote following the Delphi methodology. Final answers were developed, based on evidence and clinical experience of the participants.

RESULTS

All the recommendations achieved a high level of agreement in the plenary vote, although the quality of the evidence was markedly heterogeneous. The lowest percentage of agreement corresponded to the questions with the weakest level of evidence, highlighting the necessity of conducting further studies in these areas. The recommendations focused on (1) aminosalicylates therapy (regarding dose and appropriateness of coadministration with thiopurines), (2) corticosteroid therapy (regarding dose and route of administration), (3) thiopurine treatment (regarding indications and possibility of withdrawal), (4) anti-tumor necrosis factor therapy (regarding appropriateness of combination with thiopurines, intensification, or discontinuation of treatment), and (5) colorectal cancer (regarding risk and time trends).

CONCLUSIONS

The UC Horizons Project raised a series of eminently practical questions about the management of UC and provided responses based on the best scientific evidence available.

Allopurinol and 5-aminosalicylic acid influence thiopurine-induced hepatotoxicity in vitro

INTRODUCTION

The use of thiopurines is frequently accompanied by hepatotoxicity. Studies on hepatocyte cultures showed a time- and dose-dependent increase of thiopurine toxicity. 5-Aminosalicylic acid (5-ASA) and allopurinol can influence thiopurine metabolism; however, it is unknown whether this affects in vitro cytotoxicity.

METHODS

Human hepatoma cells (Huh7, HepG2 and HepaRG) were incubated with increasing concentrations of thiopurines, 5-ASA or allopurinol. Water-soluble tetrazolium salt-1 (WST-1) cytotoxicity assays were used to calculate cell survival curves and half maximal inhibitory concentrations (IC50). Combination experiments with thiopurines with a fixed dose of 200 μM 5-ASA or 100 μM allopurinol were conducted in HepaRG cells. Caspase-3/7 activation was evaluated, and single cell electrophoresis analysis was performed.

RESULTS

A time- and dose-related cytotoxic effect was seen with azathioprine (AZA) in all hepatoma cells, whereas Huh7 and HepG2 cells did not show toxicity to 6-mercaptopurine (6-MP). HepaRG cells expressed the highest levels of drug metabolising enzymes, and therefore, combination experiments were conducted in HepaRG cells. Addition of a non-toxic dose of allopurinol resulted in a twofold to threefold increased cytotoxicity of all thiopurines, which seemed to be mediated by apoptosis/DNA damage.

CONCLUSION

The addition of allopurinol to thiopurines leads to a two-threefold increased cytotoxicity in HepaRG cells.

Addition of mesalazine for subclinical post-surgical endoscopic recurrence of Crohn's disease despite preventive thiopurine therapy: A case-control study

BACKGROUND AND AIM

Thiopurines prevent Crohn's disease (CD) endoscopic recurrence (ER) at least in 50% of patients 1 year after surgery. This study aimed to evaluate the value of adding mesalazine in patients with subclinical ER despite preventive thiopurine therapy.

METHODS

Crohn's disease patients with ileocecal resection treated with thiopurines for postsurgical recurrence prevention in whom mesalazine was added (cases) to treat ER without clinical recurrence (CR) were identified and compared with those in whom no treatment was added to thiopurines (controls). All patients were followed up for at least 1 year from the index endoscopy. Development of CR as well as evolution of mucosal lesions was evaluated.

RESULTS

Thirty-seven patients were included (19 cases and 18 controls). Initial Rutgeerts' score was i2 in 16 patients (9 cases and 7 controls), and i3 in 21 patients (10 cases and 11 controls). After a median clinical follow-up of 59 months (interquartile range 22-100) from the index endoscopy, six cases (32%) and two controls (11%) developed CR (P = 0.2). After a median time to last endoscopic follow-up of 23 months (interquartile range 17-71), 18 patients (49%) showed improvement in Rutgeerts' score, 11 patients (30%) demonstrated progression of mucosal lesions, and 8 (22%) had no changes, with no differences between study groups.

CONCLUSIONS

The addition of mesalazine seems to be of no benefit in patients with subclinical endoscopic recurrence while on thiopurine prevention. Moderate endoscopic postsurgical recurrence while on thiopurines may even revert with no additional therapy in some patients.

Low-dose azathioprine is effective in maintaining remission among Chinese patients with Crohn's disease

BACKGROUND

Azathiopurine (AZA) is efficacious for maintenance remission of Crohn's disease (CD) at the standard dose of 2.0-2.5 mg/kg for Caucasian. It has been reported that the lower dose (1.0-2.0 mg/kg) in some Asian countries was as effective as the standard dose. In the present study we analyzed the efficacy of <1.0 mg/kg AZA in maintaining remission for Chinese patients.

METHODS

The clinical data of all CD patients were reviewed from 1993 to December 2012. The patients who initiated AZA treatment and were followed for ≥ 2 years with complete medical data were included. We divided the patients into two groups according to their initial dose: <1.0 mg/kg group and 1.0-2.0 mg/kg group.

RESULTS

Among 77 patients, 39 (50.6%) started treatment with <1.0 mg/kg AZA and 38 (49.4%) with 1.0-2.0 mg/kg. The mean dose of <1.0 mg/kg group remained under 1.0 mg/kg at 6, 12 and 24 months, even if the doses were adjusted according to efficacy and tolerance. The remission rate in patients of <1.0 mg/kg group was significantly higher than that in those of 1.0-2.0 mg/kg group (P = 0.025). A dose of <1.0 mg/kg AZA was more commonly associated with male gender, older age, heavier body weight and L1 location. Adverse events were observed in 21 of 77 patients (27.3%) and no significant difference in occurrence of adverse events or leucopenia between two groups.

CONCLUSIONS

<1.0 mg/kg AZA was effective as 1.0-2.0 mg/kg in maintaining remission among Chinese patients with CD.

Should thiopurine methyltransferase genotypes and phenotypes be measured before thiopurine therapy in patients with inflammatory bowel disease?

BACKGROUND AND AIMS

Not all of the adverse effects to thiopurine therapy can be explained by thiopurine methyltransferase (TPMT) polymorphisms. This study was intended to evaluate the value of TPMT genotype and phenotype measurement during the first year of thiopurine therapy.

METHODS

Consecutive patients with inflammatory bowel disease (IBD) who were receiving azathioprine or 6-mercaptopurine were followed up for 12 months. TPMT genotypes and phenotypes were examined in patients with IBD before thiopurine therapy and in unrelated healthy volunteers by polymerase chain reaction and high-performance liquid chromatography.

RESULTS

A total of 199 patients and 300 healthy volunteers were included at 2 centers. Forty-seven of the 199 patients (23.62%) exhibited adverse effects during the entire course of thiopurine therapy. Two (1%) patients carrying TPMT*3C developed leucopenia at week 4 of azathioprine treatment. The TPMT*3C had a specificity of 100% (163/163) but a sensitivity of 5.56% (2/36) for predicting leucopenia. The calculated optimal cutoff activity for high TPMT activity and decreased TPMT activity was 4.75 U/mL red blood cells. The risk of leucopenia increased in the decreased TPMT group (odds ratio: 20.25; 95% confidence interval: 2.19-187.17; P = 0.004) and increased more during the initial 3 months of thiopurine therapy (odds ratio: 34.80; 95% confidence interval: 3.71-326.77; P = 0.001). Leucopenia occurred more frequently in the patients cotreated with 5-aminosalicylates than in those not cotreated (32.81% versus 11.11%, respectively, P < 0.001).

CONCLUSIONS

The results of this study suggest that the value of TPMT genotyping before thiopurine therapy is limited in Chinese patients with IBD, considering the low sensitivity of predicting leucopenia, and that phenotyping is a more cost-effective tool that can be successfully used in patients. The coadministration of 5-aminosalicylates results in a high frequency of leucopenia in patients receiving azathioprine or 6-mercaptopurine.

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

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

Usefulness of salicylate and thiopurine coprescription in steroid-dependent ulcerative colitis and withdrawal strategies

5-aminosalicylic acid (5-ASA) and thiopurines (azathioprine and mercaptopurine) are the most common drugs used as a maintenance treatment for ulcerative colitis. A considerable proportion of these patients develop corticosteroid dependency, and thiopurines are the standard treatment in this scenario. Dual prescriptions of both thiopurines and 5-ASA are common practice in steroid-dependent ulcerative colitis, in an attempt to optimize the efficacy of therapy. On the one hand, the potential protective role of 5-ASA against colorectal cancer argues in favour of prescription of both medications. The possible synergism between the two drugs, because of the inhibition of thiopurine methyltransferase (TPMT) enzyme activity by 5-ASA, has been postulated as another justification for dual prescription. However, existing evidence does not support that this combined strategy is superior to monotherapy with thiopurines. On the other hand, in patients showing prolonged disease remission, the possibility of discontinuing maintenance treatment can be considered on an individualized basis. The high frequency of relapses after thiopurine withdrawal should always be taken into account, but the potential adverse effects of the medication also need to be considered. A properly indicated treatment with thiopurines may need to be continued for life in many patients.

Insight into TPMT(∗)23 mutation mis-folding using molecular dynamics simulation and protein structure analysis

Thiopurine S-methyltransferase (TPMT) is an important enzyme that metabolizes thiopurine drugs. This enzyme exhibits a large number of interindividual polymorphism. TPMT(∗)23 polymorphism has been reported in a few cases in the world in co-dominance with TPMT(∗)3A. The phenotype has been reported to affect enzyme activity in vivo and in vitro. Its underlying structural basis is not clarified yet. In our study, the wild type (WT) protein structure was analyzed and the amino acids bordering water channels in thiopurine sites were identified. Molecular dynamics of both the WT and TPMT(∗)23 mutation was carried out. In addition, the effects of this mutation, especially on the thiopurine site which is closed with a pincer like mechanism, were investigated. We focused on explaining how a locally occurred A167G substitution propagated through hydrogen bonds alteration to induce structural modification which affects both thiopurine and S-adenosylmethionine receptors. Finally, a genetic prediction of mutation functional consequences has been conducted confirming altered activity. An animated Interactive 3D Complement (I3DC) is available in Proteopedia at http://proteopedia.org/w/Journal:JBSD:20.

The potential influence of 5-aminosalicylic acid on the induction of myelotoxicity during thiopurine therapy in inflammatory bowel disease patients

OBJECTIVE

To investigate the potential influence of 5-aminosalicylic acid (5-ASA) on the induction of myelotoxicity during thiopurine therapy in inflammatory bowel disease patients.

METHODS

(a) The retrospective study included inflammatory bowel disease patients treated with azathioprine (AZA)/6-mercaptopurine (6-MP). Thiopurine methyltransferase (TPMT) activity and 6-thioguanine nucleotide (6-TGN) levels were detected at stable medication points. (b) The prospective study was performed in active disease patients: 4 weeks of AZA 50 mg/day followed by concomitant 5-ASA 3 g/day for another 4 weeks. 6-TGN was analyzed at weeks 4 and 8.

RESULTS

(a) Of the 139 retrospective study patients, 45 were on AZA/6-MP+5-ASA and 94 on AZA/6-MP alone. The myelotoxicity rates were 47 and 16%, respectively. Multivariates regression analysis indicated that the administration of concomitant 5-ASA was the only risk factor associated with myelotoxicity (odds ratio=3.45, 95% confidence interval 1.31-9.04, P=0.01). (b) Thiopurine methyltransferase activity was not significantly different between patients on AZA/6-MP+5-ASA and patients on AZA/6-MP alone (P=0.78). (c) 6-TGN levels were significantly higher in samples on AZA/6-MP+5-ASA than those on AZA/6-MP (P=0.003) alone. (d) Sixteen patients completed the prospective study. After 4 weeks on AZA 50 mg/day, 6-TGN levels of 13 patients were less than 230 pmol/8×10 RBC. After another 4 weeks' cotreatment with mesalazine 3 g/day, 12 patients had 6-TGN levels at least 230 pmol/8×10 RBC, five patients had 6-TGN levels at least 420 pmol/8×10 RBC, and two of these five patients developed myelotoxicity.

CONCLUSION

The risk of thiopurine-induced myelotoxicity markedly increases in patients treated with combined 5-ASA and 2 mg/kg/day AZA therapy, which may be correlated to the increase in 6-TGN. 50 mg daily AZA when concomitant 5-ASA might help maintain an effective 6-TGN level without increasing the risk of myelotoxicity.

Hypoxanthine guanine phosphoribosyltransferase activity is related to 6-thioguanine nucleotide concentrations and thiopurine-induced leukopenia in the treatment of inflammatory bowel disease

BACKGROUND

Thiopurine drugs are widely used in the treatment of inflammatory bowel disease (IBD). The polymorphic enzyme thiopurine S-methyltransferase (TPMT) is of importance for thiopurine metabolism and adverse events occurrence. The role of other thiopurine-metabolizing enzymes is less well known. This study investigated the effects of TPMT and hypoxanthine guanine phosphoribosyltransferase (HPRT) activities on 6-thioguanine nucleotides (6-TGNs) concentrations and thiopurine-induced leukopenia in patients with IBD.

METHODS

Clinical data and blood samples were collected from 120 IBD patients who were receiving azathioprine (AZA)/6-mercaptopurine (6-MP) therapy. Erythrocyte TPMT, HPRT activities and 6-TGNs concentrations were determined. HPRT activity and its correlation with TPMT activity, 6-TGNs level, and leukopenia were evaluated.

RESULTS

The HPRT activity of all patients ranged from 1.63-3.33 (2.31 ± 0.36) μmol/min per g Hb. HPRT activity was significantly higher in patients with leukopenia (27, 22.5%) than without (P < 0.001). A positive correlation between HPRT activity and 6-TGNs concentration was found in patients with leukopenia (r = 0.526, P = 0.005). Patients with HPRT activity > 2.70 μmol/min per g Hb could have an increased risk of developing leukopenia (odds ratio = 7.47, P < 0.001). No correlation was observed between TPMT activity and HPRT activity, 6-TGNs concentration, or leukopenia.

CONCLUSIONS

High levels of HPRT activity could be a predictor of leukopenia and unsafe 6-TGN concentrations in patients undergoing AZA/6-MP therapy. This could partly explain the therapeutic response or toxicity that could not be adequately explained by the polymorphisms of TPMT.

Biotransformation of 6-thioguanine in inflammatory bowel disease patients: a comparison of oral and intravenous administration of 6-thioguanine

BACKGROUND AND PURPOSE

Although 6-mercaptopurine and azathioprine are effective treatments in inflammatory bowel disease (IBD), many patients discontinue treatment because of side effects. 6-Thioguanine (6-TG) may be an alternative rescue therapy in these intolerant patients but the pharmacokinetics of 6-TG are not fully described. Here we have measured the pharmacokinetics of the biotransformation of 6-TG into the pharmacologically active metabolites, 6-thioguanine nucleotides (6-TGN), in IBD patients.

EXPERIMENTAL APPROACH

In 12 patients with IBD, levels of 6-TGN and activities of thiopurine S-methyltransferase, xanthine oxidase and hypoxanthine guanine-phosphoribosyl-transferase were measured in a two-stage (i.v. and p.o. administration of 0.3 mg·kg(-1) 6-TG), prospective study. Median exposure of 6-TGN in red blood cells (RBC) was expressed as the ratio of the area under the curve (AUC) per mg 6-TG after i.v. dosing and that after p.o. dosing.

KEY RESULTS

The median AUC per mg 6-TG was 1068 (p.o.) and 7184 (i.v.) pmol·h (8 × 10(8) RBC)(-1) . Median exposure of 6-TGN in RBC was 15% (9-28). Hypoxanthine guanine-phosphoribosyl-transferase activity correlated with peak 6-TGN and with AUC per mg (r= 0.7, P= 0.02 and r= 0.6, P= 0.03 respectively). Thiopurine S-methyltransferase activity was inversely related to AUC per mg (r=-0.8, P= 0.001), whereas that of xanthine oxidase was correlated with a lower peak 6-TGN (r=-0.7, P= 0.02).

CONCLUSIONS AND IMPLICATIONS

The great variability of the AUC per mg for 6-TG observed after p.o. and i.v. administration of 6-TG, was partly explained by variability in activities of metabolizing enzymes. Exposure of 6-TGN was low in all patients.

Pre-analytic and analytic sources of variations in thiopurine methyltransferase activity measurement in patients prescribed thiopurine-based drugs: A systematic review

OBJECTIVES

Low thiopurine S-methyltransferase (TPMT) enzyme activity is associated with increased thiopurine drug toxicity, particularly myelotoxicity. Pre-analytic and analytic variables for TPMT genotype and phenotype (enzyme activity) testing were reviewed.

DESIGN AND METHODS

A systematic literature review was performed, and diagnostic laboratories were surveyed.

RESULTS

Thirty-five studies reported relevant data for pre-analytic variables (patient age, gender, race, hematocrit, co-morbidity, co-administered drugs and specimen stability) and thirty-three for analytic variables (accuracy, reproducibility). TPMT is stable in blood when stored for up to 7 days at room temperature, and 3 months at -30°C. Pre-analytic patient variables do not affect TPMT activity. Fifteen drugs studied to date exerted no clinically significant effects in vivo. Enzymatic assay is the preferred technique. Radiochemical and HPLC techniques had intra- and inter-assay coefficients of variation (CVs) below 10%.

CONCLUSION

TPMT is a stable enzyme, and its assay is not affected by age, gender, race or co-morbidity.

Limitations of extensive TPMT genotyping in the management of azathioprine-induced myelosuppression in IBD patients

BACKGROUND AND AIMS

TPMT deficiency is associated with azathioprine (AZA)-induced myelosuppression (MS). However, in one previous study, only about ¼ of MS episodes in Crohn's Disease patients under AZA can be attributed to TPMT deficiency. Recently, new TPMT mutations have been described and our aim is to investigate their clinical relevance before and after a first MS episode on thiopurine therapy.

METHODS

Clinical data from 61 IBD patients having developed MS during AZA therapy were collected. Sequencing analysis was carried out on TPMT cDNA for the presence of all currently known mutations.

RESULTS

Only TPMT *2, *3A and *3C mutations were found in this cohort. TPMT mutations were observed in 15 out of 61 patients (25%). Four out of 15 were homozygous for a TPMT mutation (low methylator, LM genotype) and 11 were heterozygous (intermediate methylator, IM genotype). Median delays of MS onset were 2, 2.75 and 6months in the LM, IM and HM (high methylator, wild type TPMT) groups, respectively. After the first MS episode, 36 patients resumed thiopurine treatment of which 13 experienced a second MS episode. This second episode was also rarely associated with TPMT mutations.

CONCLUSIONS

One quarter of MS episodes during AZA were associated with TPMT deficient genotype. After a first leucopenia episode, thiopurine therapy may be resumed in a majority of patients independently of their TPMT genotype.

Thiopurine metabolism monitoring: implications in inflammatory bowel diseases

BACKGROUND

Thiopurines (TP) are widely used in the management of inflammatory bowel diseases. Side effects and inefficacy are a major concern as they lead to withdrawal of the drug.

MATERIALS AND METHODS

Tools investigating TP metabolism are useful to avoid inadequate cessation of TP therapy.

RESULTS

TP metabolism is complex and many enzymes are involved. Among them, Thiopurine methyl transferase is the only one routinely measured by pheno- or genotyping. A decreased TPMT activity results in a potential overdosing of TP drugs leading to myelotoxicity, whereas an ultra-high activity leads to TP ineffectiveness and overproduction of methylated compounds responsible for hepatotoxicity. TPMT determination prior to TP treatment results in an individual adapted dose. Xanthine oxidase/dehydrogenase (XOD), inosine triphosphate pyrophosphatase (ITPA) and glutathion-S-transferase (GST) are other promising enzyme targets that might help to explain TP efficacy or toxicity. ITPA and GST polymorphisms might potentially be related to some TP side effects, while a XOD inhibition by allopurinol could avoid TP-related hepatotoxicity.

CONCLUSIONS

Utilization of thiopurine metabolites, 6-thioguanine nucleotides and 6-methylmercaptopurine, is discussed, specifically, in case of thiopurine failure and recommendations are given about their interpretation and potential dose optimization. These enzymes and metabolites tests are complementary to the regular monitoring of blood cells count and liver tests which remains mandatory.

Influence of 5-aminosalicylic acid on 6-thioguanosine phosphate metabolite levels: a prospective study in patients under steady thiopurine therapy

BACKGROUND AND PURPOSE

5-aminosalicylate (5-ASA) raises levels of 6-thioguanine nucleotides (6-TGN), the active metabolites of thiopurines such as azathioprine (AZA). Changes in levels of each individual TGN - 6-thioguanosine mono-, di- and triphosphate (6-TGMP, 6-TGDP, 6-TGTP) - and of 6-methylmercaptopurine ribonucleotides (6-MMPR) after 5-ASA are not known.

EXPERIMENTAL APPROACH

Effects of increasing 5-ASA doses on AZA metabolites were investigated prospectively in 22 patients with inflammatory bowel disease in 4-week study periods. Patients started with 2 g 5-ASA daily, and then were increased to 4 g daily and followed by a washout period. Thiopurine doses remained unchanged throughout the entire study. Levels of 6-TGMP, 6-TGDP, 6-TGTP and 6-MMPR as well as of 5-ASA and N-acetyl-5-aminosalicylic acid (N-Ac-5-ASA) were determined each study period.

KEY RESULTS

Median baseline levels in 17 patients of 6-TGDP, 6-TGTP and 6-MMPR were 52, 319 and 1676 pmol per 8 x 10(8) red blood cells respectively. After co-administration of 2 g 5-ASA daily, median 6-TGDP and 6-TGTP levels increased but median 6-MMPR levels were unchanged. Increasing 5-ASA to 4 g daily did not affect median 6-TGDP and 6-TGTP levels, but median 6-MMPR levels decreased. After discontinuation of 5-ASA, both 6-TGDP and 6-TGTP levels decreased and median 6-MMPR levels increased. The 6-TGTP/(6-TGDP+6-TGTP)-ratio did not change during the study, but 6-MMPR/6-TGN ratios decreased.

CONCLUSIONS AND IMPLICATIONS

Individual 6-TGN metabolites increased after addition of 5-ASA, but 6-MMPR-levels and the 6-MMPR/6-TGN ratios decreased. Further studies are needed to decide whether this pharmacokinetic interaction would result in improvement of efficacy and/or increased risk of toxicity of AZA.

Thiopurines in Crohn's disease, is there something new?

IMPORTANCE OF THE FIELD

traditional immunosuppressants, including azathioprine, remain the mainstay of therapy in steroid dependent/refractory patients with inflammatory bowel diseases (IBD). The main limitations of its use are its side effects appearing in about a fifth of the patients, including myelosuppression and liver toxicity. Major complications occur in patients with low thiopurine-S-methyltransferase (TPMT) enzyme activity; however, the clinical relevance of these tests remains conflictive.

AREAS COVERED IN THIS REVIEW

in this review, the authors aim to summarize the new data regarding the relationship between the pharmacology of thiopurines and pathogenesis of adverse events.

WHAT THE READER WILL GAIN

readers will gain an understanding of the metabolism of thiopurines, side effect profile, pharmacological background of side effects, importance of metabolite monitoring, clinical relevance of inherited differences in drug metabolism and other conditions (e.g., concomitant use of allopurinol) which can modify enzyme activity. By gaining an understanding of the pharmacology and metabolism of thiopurines, clinicians will be able to optimize thiopurine therapy in IBD.

TAKE HOME MESSAGE

TPMT testing and metabolite monitoring are still not considered the standard of care, and clinicians will continue to choose the approach that best suits their clinical practice and patient needs. Regardless of what strategy is chosen, patients need to be carefully monitored and well informed about the potential risks.

Optimising use of thiopurines in inflammatory bowel disease

Azathioprine (AZA) and 6-mercaptopurine (6-MP) are the most widely used immunosuppressive therapies in inflammatory bowel disease. Pretreatment measurement of thiopurine methyltransferase (TPMT) activity is recommended and although conventional practice is to use a dose of 2 mg/kg AZA (1 mg/kg 6-MP), higher doses of 2.5 mg/kg AZA or more may be required in some patients, particularly if TPMT activity is high. Dose raising is limited by toxicity, and a robust monitoring system is mandatory. Patients with side effects to AZA may tolerate 6-MP but pancreatitis is a contraindication to switching. Metabolite monitoring is not widely available but may be useful, particularly if non-compliance is possible or where metabolite shunting to 6-methylmercaptopurine is suspected, on the basis of non-response or toxicity. It may allow dose optimisation before switching to alternative immunosuppressants. The drug appears safe in pregnancy and breast feeding. Long term duration of therapy is a balance between benefits in relation to the underlying disease extent, activity and aggressiveness, and the risk of neoplasia, particularly lymphoma.

Sulfasalazine and pentoxifylline in psoriasis: a possible safe alternative

BACKGROUND

Conventional therapy of extensive psoriasis is effective but has complications. Biologics are safer but expensive.

OBJECTIVE

To assess the efficacy of sulfasalazine and pentoxifylline, which have TNF antagonizing and anti-proliferative action in the treatment of psoriasis.

METHODS

In this randomized controlled trial, 32 patients with extensive psoriasis were divided into four groups: group A received sulfasalazine; group B received pentoxifylline; group C received both drugs; and group D received methotrexate. The Psoriasis Area and Severity Index (PASI) score was done at weeks 0, 2, 4, 6 and 8.

RESULTS

A significant reduction in PASI score occurred in groups C and D (p = 0.043 and 0.018, respectively). A significantly higher percentage of PASI score reduction occurred in group D compared with groups A, B and C (p = 0.006, 0.003 and 0.030, respectively). An excellent response occurred in one patient (14.3%) in group D. A very good response occurred in two patients (22.2%) in group C, and in five patients (71.4%) in group D. A moderate response occurred in three patients (37.5%) in group A, one patient (12.5%) in group B, and one patient (14.3%) in group D.

CONCLUSION

Although incomparable to methotrexate, combined sulfasalazine and pentoxifylline produced a good response in cases of extensive psoriasis. Multicentre studies are needed to validate these results.

Patient considerations in the management of ulcerative colitis: role of once-daily MMX mesalamine

Mesalamine and its derivatives are effective and well-tolerated therapies for ulcerative colitis. However, patient adherence to traditional mesalamine-based therapy is poor, and is often limited by heavy pill burdens and frequent dosing intervals. This can lead to ineffective disease control, impaired quality of life, and preventable morbidity and mortality. Previous studies have suggested that a once-daily mesalamine regimen would be strongly adhered to in the outpatient setting, but at that time no such formulation of mesalamine existed. In 2007, clinical trial data showed a novel, once-daily, multi-matrix (MMX) formulation of mesalamine to be effective in both remission induction and remission maintenance. This breakthrough in drug delivery allowed the unification of an effective therapeutic with a formulation that enables outpatients to be increasingly adherent to their medication. In theory, this might result in improved outpatient disease control and a decreased number of flares. As the use of MMX mesalamine increases, studies examining the outpatient community adherence rate need to be performed.

Prospective study of the effects of concomitant medications on thiopurine metabolism in inflammatory bowel disease

BACKGROUND

Thiopurines are increasingly used in the treatment of inflammatory bowel disease (IBD), being the most common immunosuppressive therapy; however, potentially harmful interactions between thiopurines and other drugs (especially 5-aminosalicylic acid, 5-ASA) were described.

AIM

To explore potential interactions between thiopurines and concomitant medications.

METHODS

A total of 183 consecutive IBD patients were enrolled. Clinical characteristics and concomitant medications were recorded. Thiopurine metabolism was analysed with thiopurine S-methyl transferase (TPMT) genetic variants and enzyme activity assays. Comparisons were carried out with stratification of patients according to clinical characteristics and active treatments.

RESULTS

Based on TPMT genetics, 95% IBD patients were wild-type homozygous, the remaining being heterozygous. Median TPMT activity was 24.9 U/Hgb g (IQR 20.7-29.5). No difference in TPMT activity was noted according to 5-ASA exposure. IBD patients on thiopurines had higher TPMT activity levels, but no dose-effect was evident. No difference in TPMT activity was observed in 41 (63%) patients co-treated with 5-ASA. In patients on active thiopurines also, 6-TGN and 6-MMP levels were evaluated and no significant difference was observed based on co-medication. TPMT activity was independently associated only with thiopurines dose (P = 0.016).

CONCLUSIONS

Our data suggest the absence of significant interactions between thiopurines and 5-ASA.

Individually administered or co-prescribed thiopurines and mesalamines for inflammatory bowel disease

Data from both basic research and clinical experience continue to suggest that mesalamines and thiopurines are effective and efficient for the maintenance of remission of inflammatory bowel diseases. Several decades following the formalization of their indications, attention on these two drugs has been fostered by recent achievements. Demonstration of the ability of mesalamine to activate a colonocyte differentiation factor has shed light on its chemopreventive effects on colorectal cancer; in addition to their anti-proliferative efficacy, thiopurines have been shown to be specific regulators of apoptosis. The two drugs are often co-administered in clinical practice. Recent advancements have shown that mesalamines exert a positive synergism in this context, insofar as they can inhibit side-methylation of thiopurines and hasten the function of the main immunosuppressive pathways. Considering that up to 40% of patients cannot tolerate thiopurines, such renovated targets have stimulated efforts to improve compliance by research on the toxicity mechanisms. The definition of genetic polymorphisms in the enzymes of thiopurine metabolism, and the uncovering of synergistic drug interactions, such as that with allopurinol, are just two of the results of such efforts. Interaction between basic research and clinical practice has continued to inform indications and refine the prescriptions of mesalamines and thiopurines; these have not been restrained (they have been implemented in some cases) by the advent of the novel biological molecules with anti-cytokine activity.

Systematic review: does concurrent therapy with 5-ASA and immunomodulators in inflammatory bowel disease improve outcomes?

BACKGROUND

With greater use of immunomodulators in inflammatory bowel disease (IBD), it is uncertain whether concurrent therapy with both 5-aminosalicylic acid [5-ASA, mesalazine (mesalamine)] and an immunomodulator is necessary.

AIM

To determine whether concurrent therapy with both 5-ASA and immunomodulator(s) improves outcomes in IBD.

METHODS

Systematic review with search terms 'azathioprine, 6-mercaptopurine, thiopurine(s), 5 aminosalicylic acid, mesalazine, inflammatory bowel disease, ulcerative colitis, Crohn's disease, immunosuppressant(s), immunomodulator and methotrexate' in November 2007 to identify clinical trials on concurrent 5-ASA and immunomodulator therapy.

RESULTS

Two small controlled studies were found. Neither showed a benefit on disease control beyond immunomodulator monotherapy. Potential pharmacological interactions exist between 5-ASA and thiopurines. Whilst circumstantial, epidemiological and laboratory evidence suggests that 5-ASA may assist colorectal cancer (CRC) chemoprevention, it may simply be via anti-inflammatory effects. With changes in practice, ethical issues and the long lead-time needed to demonstrate or disprove an effect, no clinical studies can/will directly answer this. The costs of avoiding one CRC in IBD may be as low as 153 times the annual cost of 5-ASA therapy.

CONCLUSIONS

It is unclear whether concurrent 5-ASA and immunomodulator therapy improves outcomes of disease control, drug toxicity or compliance. Concurrent therapy of 5-ASA and immunomodulators may decrease CRC risk at 'acceptable' cost.

Co-prescribing azathiopurine or 6-mercaptopurine and 5-aminosalicylate compounds in ulcerative colitis

BACKGROUND

A total of 254 senior consultant gastroenterologists with valid e-mail addresses were identified from the membership list of the British Society of Gastroenterology (BSG) 2007.

METHODS

They were sent by e-mail a questionnaire which dealt with aspects of clinical practice and addressed cancer prevention in ulcerative colitis (UC). Replies were received from 97 clinicians (38% response rate).

RESULTS

Ninety-one (94%) advised patients with established UC to take 5-aminosalicylate (5-ASA) compounds for life. Seventy-two of the 91 (79%) clinicians co-prescribed 5-ASA compounds with immune modulators for patients with UC. Only 3 clinicians advised patients to take folic acid as a daily supplement. A median of 20% (interquartile range 10%-50%) of their patients with UC were co-prescribed a 5-ASA compound and azathioprine or 6-mercaptopurine. Of these, a median of 3.5% (interquartile 1%-5%) developed neutropenia.

CONCLUSIONS

Future research needs to be directed at the long-term maintenance treatment and to address questions about which drugs should be used, in what combinations, and with what frequencies.

Should azathioprine and 5-aminosalicylates be coprescribed in inflammatory bowel disease?: an audit of adverse events and outcome

BACKGROUND

An interaction between azathioprine and 5-aminosalicylates may exist, but the mechanism remains unclear.

OBJECTIVES

To investigate the occurrence of adverse events and efficacy of azathioprine with or without mesalazine.

METHOD

Retrospective study of 199 patients. In all, 95 patients received azathioprine alone (monotherapy); 104 received combination of 5-aminosalicylates and azathioprine (dual therapy). Data were recorded on adverse events, azathioprine dose and thiopurine methyl transferase (TPMT) level. In 85 of the patients, relapse rate was compared in the two groups.

RESULTS

Adverse events were more common in dual therapy group, 50/104, than in monotherapy group, 29/95; chi=6.4, P=0.05. Most patients had normal TPMT activity. No relationship between TPMT activity and adverse events was observed. A total of 105 patients took (>or=2 mg/kg) azathioprine; adverse events occurred in 26% compared with 54% taking less than 2 mg/kg (chi=15.8, P<0.0001). Discontinuation of azathioprine owing to adverse events was found to be higher in dual therapy group, 26/50, than in monotherapy group, 7/29 (chi=5.0, P<0.01). Relapse rate was higher in the dual therapy group (29/49) than with monotherapy (12/36) (chi=5.5, P<0.02).

CONCLUSION

Adverse events are more common in patients taking dual therapy than azathioprine monotherapy. Adverse events are unrelated to dose of azathioprine. Patients receiving dual therapy are more likely to relapse than patients receiving monotherapy.

Dose-dependent influence of 5-aminosalicylates on thiopurine metabolism

INTRODUCTION

Studies indicated that 5-aminosalicylates (5-ASA) may influence the metabolism of thiopurines; however, conclusions were restricted as a result of number of patients or study design.

AIM

To determine the influence of 5-ASA on thiopurine metabolism, we performed a prospective multicenter pharmacokinetic interaction study of two different 5-ASA dosages (2 g daily followed by 4 g daily) in 26 inflammatory bowel disease (IBD) patients during steady-state AZA or 6-MP therapy.

RESULTS

The 4-wk coadministration of 2 g 5-ASA daily, followed by a 4-wk period of 4 g 5-ASA daily, led to a statistical significant increase of 40% (absolute 84 pmol/8x10(8) RBC) and 70% (absolute 154 pmol/8x10(8) RBC) in 6-thioguaninenucleotide levels (6-TGN), respectively. A rise in 6-TGN levels was observed in 100% of patients after a 4-wk period of 4 g 5-ASA daily. The 6-methylmercaptopurine-ribonucleotide levels did not change. Signs of myelotoxicity were observed in 7.7% of patients (N=2).

CONCLUSIONS

The level of the pharmacologically active 6-TGN significantly increases in a dose-dependent manner during 5-ASA coadministration. IBD patients who are unresponsive or refractory to standard thiopurine therapy may benefit from the coadministration of 5-ASA, leading to an increase in 6-TGN levels.

Assessment of thiopurine methyltransferase enzyme activity is superior to genotype in predicting myelosuppression following azathioprine therapy in patients with inflammatory bowel disease

BACKGROUND

Myelosuppression occurs in 2-7% of inflammatory bowel disease (IBD) patients treated with azathioprine, and can be associated with reduced activity of thiopurine methyltransferase (TPMT) in some patients. It has been proposed that pretreatment assessment of TPMT status reduces the incidence of toxicity and is cost-effective.

AIMS

To determine if screening for TPMT status predicts side-effects to azathioprine in patients with IBD and to ascertain whether screening by TPMT enzyme activity or genotype is superior.

METHODS

Sequential IBD patients were identified and azathioprine tolerance recorded. Blood was collected for measurement of TPMT activity and TPMT*3C, TPMT*3A and TPMT*2 genotypes.

RESULTS

Of 130 patients, 25% stopped azathioprine because of toxicity. Four patients experienced severe myelosuppression (WCC < 2). Eleven of 17 patients with reduced TPMT activity were heterozygotes, including one patient with marked TPMT deficiency who experienced severe myelosuppression. There was no association between intermediate TPMT deficiency and any side-effect.

CONCLUSIONS

Moderate reduction of TPMT activity in heterozygotes was not associated with toxicity, but very low TPMT activity caused severe myelosuppression in one patient. This would have been predicted by measuring TPMT activity but not by genotyping. Measurement of TPMT activity may therefore be superior to genotype in predicting severe myelosuppression.