Azathioprine and 6-mercaptopurine pharmacogenetics and metabolite monitoring in inflammatory bowel disease

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

BACKGROUND

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

RESULTS

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

CONCLUSION

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

New genetic associations in thiopurine-related bone marrow toxicity among inflammatory bowel disease patients

Background: The toxicity related to thiopurine drug therapy for inflammatory bowel disease (IBD) varies widely among patients. Almost 15–30% of patients with IBD develop side effects during treatment, often bone marrow suppression. Several factors have been implicated in determining this toxicity, mainly individual genetic variation related to formation of active thiopurine metabolites. The aim was to identify genes involved in thiopurine-related myelosuppression. Materials & methods: A two-stage investigation of 19,217 coding SNPs (cSNPs) was performed in a Spanish (Inflammatory Bowel Disease Group of Galicia [EIGA]) cohort of 173 IBD patients, 15 with bone marrow suppression. The top 20 cSNPs identified in the first stage with p < 10-3 for allelic test association and SNPs that define the common TPMT alleles were replicated in a different Spanish (ENEIDA) cohort (87 patients, 29 with bone marrow suppression). Results: Several cSNPs showed a significant p-value in the allelic joint analysis (p-Cochran–Mantel–Haenszel test ≤2.55 × 10-3) despite no cSNP passing correction for multiple testing in the first cohort. Of note is rs3729961 in the gene IL6ST, a transducer signal chain shared by many cytokines including IL6 (p-value combined = 2.36 × 10-4, odds ratio [95% CI]: 3.41 [1.71–6.78]). In addition, we detected association with rs3749598 in the FSTL5 gene that appears to interact with metalloproteases at the extracellular matrix level (p-value combined = 4.89 × 10-4), odds ratio (95% CI): 3.67 (1.68–8.01). Conclusion: We have identified IL6ST and FSLT5 as new bone marrow suppression susceptibility candidate genes after thiopurine treatment in IBD patients. This is the first report of variants associated with thiopurine-related myelosuppression that was identified by a genome-wide association study. Its validation awaits functional analyses and replication in additional studies.

Original submitted 14 September 2012; Revision submitted 13 February 2013

Thiopurines in inflammatory bowel disease revisited

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

Mucosal improvement in patients with moderate to severe postoperative endoscopic recurrence of Crohn's disease and azathioprine metabolite levels

BACKGROUND

The value of azathioprine metabolites (6-thioguanine nucleotides [6-TGN]) in monitoring clinical treatment response is still controversially discussed. Data regarding thiopurine metabolite levels and endoscopic improvement are lacking.

METHODS

Data were analyzed post hoc from a 1-year, multicenter, double-blind, double-dummy, randomized trial comparing azathioprine 2.0 to 2.5 mg/kg per day versus mesalamine 4 g/d in a subset of 23 postoperative patients with Crohn's disease (CD) treated with azathioprine and having moderate-to-severe endoscopic recurrence according to a modified 6-grade score. Red blood cell (RBC) concentrations of 6-TGN, 6-methyl-mercaptopurine ribonucleotides (6-MMPR), and 6-methyl-thioguanine nucleotides (6-MTGN) were indicated as follows: area under the concentration-time curve, average concentration (C av), and concentration at the final study visit.

RESULTS

Overall, 74% of patients showed an improvement in the modified endoscopic score (P = 0.022). Median endoscopic score reduced from 4 at the baseline to 2 at the final visit. Patients with a high C av for 6-TGN (≥ 193 pmol/8 × 10(8) RBC; P = 0.017) or 6-MTGN (≥ 79.2 pmol/8 × 10(8) RBC; P = 0.035) significantly improved in endoscopic score, and the improvement in endoscopic score correlated with C av for 6-TGN (r = -0.51; P = 0.013). For concentration at the final visit, higher values for 6-TGN (≥ 142 pmol/8 × 10(8) RBC; P = 0.017) were associated with a better postoperative score. Sensitivity analysis revealed a significant correlation between 6-TGN (area under the concentration-time curve) and postoperative endoscopic improvement.

CONCLUSIONS

Our post hoc analysis from a double-blind, randomized trial suggests that higher RBC 6-TGN levels are associated with endoscopic improvement in patients with severe postoperative endoscopic recurrence of CD. Thus, our study provides first evidence on the utility of monitoring of thiopurine metabolites to achieve mucosal response in CD.

The impact of introducing thioguanine nucleotide monitoring into an inflammatory bowel disease clinic

BACKGROUND

Thioguanine nucleotides (TGNs) are the active product of thiopurine metabolism. Levels have been correlated with effective clinical response. Nonetheless, the value of TGN monitoring in clinical practice is debated. We report the influence of introducing TGN monitoring into a large adult inflammatory bowel disease (IBD) clinic.

PATIENTS AND METHODS

Patients with IBD undergoing TGN monitoring were identified from Purine Research Laboratory records. Whole blood TGNs and methylated mercaptopurine nucleotides were hydrolysed to the base and measured using HPLC. Clinical and laboratory data were obtained retrospectively.

RESULTS

One hundred and eighty-nine patients with 608 available TGN results were identified. In non-responders, TGNs directed treatment change in 39/53 patients. When treatment was changed as directed by TGN, 18/20 (90%) improved vs. 7/21 (33%) where the treatment decision was not TGN-directed, p < 0.001. Where treatment change was directed at optimisation of thiopurine therapy, 14/20 achieved steroid-free remission at 6 months vs. 3/10 where the TGN was ignored, (p = 0.037). Six per cent of patients were non-adherent, 25% under-dosed and 29% over-dosed by TGN. Twelve per cent of patients predominantly methylated thiopurines, this group had low TGN levels and high risk of hepatotoxicity. In responders, adherence and dosing issues were identified and TGN-guided dose-reduction was possible without precipitating relapse. Mean cell volume (MCV), white blood cell count (WBC) and lymphocyte counts were not adequate surrogate markers. MCV/WBC ratio correlated with clinical response, but was less useful than TGN for guiding clinical decisions.

CONCLUSIONS

Monitoring TGNs enables thiopurine therapy to be optimised and individualised, guiding effective treatment decisions and improving clinical outcomes.

The long-term risk of continuous immunosuppression using thioguanides in inflammatory bowel disease

The efficacy of thiopurine treatment in the induction, and especially maintenance, of remission in inflammatory bowel disease is well proven; however, it is associated with side effects in both medium and long-term use. The potential harmful effects may be anticipated and minimised by due diligence prior to commencing these drugs followed by close monitoring of haematological and biochemical parameters once started. Careful clinical examination and history taking are also essential. Affected patients are expected to lead lives that include travel, employment and pregnancy - the implications of continued thiopurine therapy in such patients are discussed.

Azathioprine and 6-mercaptopurine for maintenance of remission in ulcerative colitis

BACKGROUND

Maintenance of remission is a major issue in inflammatory bowel disease. In ulcerative colitis, the evidence for the effectiveness of azathioprine and 6-mercaptopurine for the maintenance of remission is still controversial.

OBJECTIVES

To assess the effectiveness and safety of azathioprine and 6-mercaptopurine for maintaining remission of ulcerative colitis.

SEARCH METHODS

The MEDLINE, EMBASE and Cochrane Library databases were searched from inception to June 2012. A manual search was also performed using references from these articles as well as review articles, and proceedings from major gastrointestinal meetings. Authors of maintenance trials were asked about unpublished studies.

SELECTION CRITERIA

Randomized controlled trials of at least 12 months duration that compared azathioprine or 6-mercaptopurine with placebo or standard maintenance therapy (e.g. mesalazine) were included.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data using standard forms. Disagreements were solved by consensus including a third author. Study quality was assessed using the Cochrane risk of bias tool. The primary outcome was failure to maintain clinical or endoscopic remission. Secondary outcomes included adverse events and withdrawal due to adverse events. Analyses were performed separately by type of control (placebo, or active comparator). Pooled risk ratios were calculated based on the fixed-effect model unless heterogeneity was shown. The GRADE approach was used to assess the overall quality of evidence for pooled outcomes.

MAIN RESULTS

Six studies including 286 patients with ulcerative colitis were included in the review. The risk of bias was high in three of the studies due to lack of blinding. Azathioprine was shown to be significantly superior to placebo for maintenance of remission. Fourty-four per cent (51/115) of azathioprine patients failed to maintain remission compared to 65% (76/117) of placebo patients (4 studies, 232 patients; RR 0.68, 95% CI 0.54 to 0.86). A GRADE analysis rated the overall quality of the evidence for this outcome as low due to risk of bias and imprecision (sparse data). Two trials that compared 6-mercaptopurine to mesalazine, or azathioprine to sulfasalazine showed significant heterogeneity and thus were not pooled. Fifty per cent (7/14) of 6-mercaptopurine patients failed to maintain remission compared to 100% (8/8) of mesalamine patients (1 study, 22 patients; RR 0.53, 95% CI 0.31 to 0.90). Fifty-eight per cent (7/12) of azathioprine patients failed to maintain remission compared to 38% (5/13) of sulfasalazine patients (1 study, 25 patients; RR 1.52, 95% CI 0.66 to 3.50). One small study found that 6-mercaptopurine was superior to methotrexate for maintenance of remission. In the study, 50% (7/14) of 6-mercaptopurine patients and 92% (11/12) of methotrexate patients failed to maintain remission (1 study, 26 patients; RR 0.55, 95% CI 0.31 to 0.95). All of the studies which used active comparators were open label. When placebo and active comparator studies were pooled to assess adverse events, there was no statistically significant difference between azathioprine and control in the incidence of adverse events. Nine per cent (11/127) of azathioprine patients experienced at least one adverse event compared to 2% (3/130) of placebo patients (5 studies, 257 patients; RR 2.82, 95% CI 0.99 to 8.01). Patients receiving azathioprine were at significantly increased risk of withdrawing due to adverse events. Eight per cent (8/101) of azathioprine patients withdrew due to adverse events compared to 0% (0/98) of control patients (5 studies, 199 patients; RR 5.43, 95% CI 1.02 to 28.75). Adverse events related to study medication included acute pancreatitis (3 cases) and significant bone marrow suppression (5 cases). Deaths, opportunistic infection or neoplasia were not reported.

AUTHORS' CONCLUSIONS

Azathioprine therapy appears to be more effective than placebo for maintenance of remission in ulcerative colitis. Azathioprine or 6-mercaptopurine may be effective as maintenance therapy for patients who have failed or cannot tolerate mesalazine or sulfasalazine and for patients who require repeated courses of steroids. More research is needed to evaluate superiority over standard maintenance therapy, especially in the light of a potential for adverse events from azathioprine. This review updates the existing review of azathioprine and 6-mercaptopurine for maintenance of remission in ulcerative colitis which was published in the Cochrane Library (Issue 1, 2007).

Split-dose administration of thiopurine drugs: a novel and effective strategy for managing preferential 6-MMP metabolism

BACKGROUND

Mercaptopurine and azathioprine (AZA) are efficacious in treating IBD. 6-tioguanine (6-TGN) levels correlate with therapeutic efficacy, whereas high 6-methylmercaptopurine (6-MMP) levels are associated with hepatotoxicity and myelotoxicity. Some IBD patients exhibit dose-limiting preferential 6-MMP production, which may lead to undesired side effects and impact efficacy.

AIM

To review the outcomes of thiopurine split-dosing in patients with preferential 6-MMP metabolism.

METHODS

A retrospective chart review of 179 IBD patients treated at the Cedars-Sinai IBD Center with AZA or mercaptopurine was performed. Preferential 6-MMP metabolisers with 6-MMP levels greater than 7000 pmol/8 × 10(8) erythrocytes who underwent split-dosing were identified and assessed for biochemical and clinical responses to these dose modifications.

RESULTS

A total of 20 of 179 patients met the criteria for preferential 6-MMP metabolism and underwent thiopurine split-dosing. Dividing the total daily thiopurine dose led to a reduction in 6-MMP levels (11785 vs. 5324 pmol/8 × 10(8) erythrocytes; P < 0.0001) without negatively affecting clinical disease activity or 6-TGN levels (239 vs. 216 pmol/8 × 10(8) erythrocytes; P = N.S.) and led to resolution of 6-MMP associated side effects (elevated transaminases, leucopenia and flu-like symptoms) in all but two patients. After mean follow-up of 36 months, 12 patients remained in clinical remission on split-dose mercaptopurine. Five of the remaining eight patients escalated to anti-TNF therapy, two progressed to surgery, and one switched to tioguanine therapy.

CONCLUSION

Split-dose administration of mercaptopurine/AZA represents an alternative option in IBD patients with preferential 6-MMP metabolism who might otherwise require steroid exposure or escalation of therapy.

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.

Mesalamine in the treatment and maintenance of remission of ulcerative colitis

Ulcerative colitis (UC) is a chronic disease of the GI tract that is characterized by mucosal inflammation in the colon. Mesalamine (mesalazine) is a 5-aminosalicylic acid compound that is the first-line treatment for patients with mild-to-moderate UC. There are multiple formulations of mesalamine available, primarily differentiated by their means of delivering active mesalamine to the colon. Mesalamine has been demonstrated in randomized controlled trials to induce both clinical response and remission, and maintain clinical remission, in these patients. It has few serious adverse effects and is generally well tolerated by patients. The main areas of uncertainty with use of mesalamine in patients with UC center on the optimal dose for induction of response, how to maintain patient adherence and the role of mesalamine in cancer chemoprophylaxis. Generic forms of mesalamine have yet to be approved by regulatory bodies in the USA.

Thiopurine methyltransferase genotype and thiopurine S-methyltransferase activity in Greek children with inflammatory bowel disease

BACKGROUND

Azathioprine (AZA) and 6-mercaptopurine (6MP) are used in the treatment of pediatric inflammatory bowel disease (IBD). Genetic variations in thiopurine S-methyltranfarase (TPMT) gene have been correlated with enzyme activity and with the occurrence of adverse events to AZA and 6MP. The aim of the present study was to examine the sensitivity and specificity of TPMT genotyping for TPMT enzymatic activity, reducing harm from thiopurine by pretesting, and the association of thiopurine toxicity with TPMT status in children with IBD.

METHODS

TPMT red blood cell (RBC) activity was measured by using a radiochemical method and genotype was determined for the TPMT alleles *2, *3A, *3B and *3C in 108 thiopurinetreated pediatric IBD patients with a mean age of 11.3 years (range 3-16).

RESULTS

Significant TPMT activity differences between wild-type and heterozygous and homozygous mutated subjects were observed. We divided TPMT activity into three categories according to frequency distribution: low (16.67%), intermediate (25.92%) and high (57.41%). The whole population included a total of 77.78% of homozygous wild-type subjects, 15.74% heterozygous variants, 1.85% homozygous variants and five (4.63%) compound heterozygous variant TPMT*3B/*3C. The overall concordance rate between TPMT genotypes and phenotypes was 88.2%. Seven carriers of at least one variant allele and low or intermediate TPMT activity developed adverse effects.

CONCLUSIONS

Our findings suggest that carriers of at least one variant allele and both intermediate and absent TPMT activity have an increased risk of developing thiopurine-induced myelotoxicity compared with individuals with normal genotype and TPMT activity.

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.

Facilitating pharmacogenetic studies using electronic health records and natural-language processing: a case study of warfarin

OBJECTIVE

DNA biobanks linked to comprehensive electronic health records systems are potentially powerful resources for pharmacogenetic studies. This study sought to develop natural-language-processing algorithms to extract drug-dose information from clinical text, and to assess the capabilities of such tools to automate the data-extraction process for pharmacogenetic studies.

MATERIALS AND METHODS

A manually validated warfarin pharmacogenetic study identified a cohort of 1125 patients with a stable warfarin dose, in which 776 patients were managed by Coumadin Clinic physicians, and the remaining 349 patients were managed by their providers. The authors developed two algorithms to extract weekly warfarin doses from both data sets: a regular expression-based program for semistructured Coumadin Clinic notes; and an advanced weekly dose calculator based on an existing medication information extraction system (MedEx) for narrative providers' notes. The authors then conducted an association analysis between an automatically extracted stable weekly dose of warfarin and four genetic variants of VKORC1 and CYP2C9 genes. The performance of the weekly dose-extraction program was evaluated by comparing it with a gold standard containing manually curated weekly doses. Precision, recall, F-measure, and overall accuracy were reported. Associations between known variants in VKORC1 and CYP2C9 and warfarin stable weekly dose were performed with linear regression adjusted for age, gender, and body mass index.

RESULTS

The authors' evaluation showed that the MedEx-based system could determine patients' warfarin weekly doses with 99.7% recall, 90.8% precision, and 93.8% accuracy. Using the automatically extracted weekly doses of warfarin, the authors successfully replicated the previous known associations between warfarin stable dose and genetic variants in VKORC1 and CYP2C9.

The role of inosine-5'-monophosphate dehydrogenase in thiopurine metabolism in patients with inflammatory bowel disease

BACKGROUND

There is a large interindividual variability in thiopurine metabolism. High concentrations of methylthioinosine-5'-monophosphate (meTIMP) and low concentrations of 6-thioguanine nucleotides (6-TGNs) have been associated with a lower response rate and an increased risk of adverse events. In this study, the role of inosine-5'-monophosphate dehydrogenase (IMPDH) for differences in metabolite patterns of thiopurines was investigated.

METHODS

IMPDH activity and thiopurine metabolite concentrations were determined in patients with inflammatory bowel disease and a normal thiopurine methyltransferase (TPMT) phenotype and meTIMP/6-TGN concentration ratio > 20 (n = 26), in patients with a metabolite ratio ≤ 20 (n = 21), in a subgroup with a metabolite ratio <4 (n = 6), and in 10 patients with reduced TPMT activity. In vitro studies were conducted on human embryonic kidney cells (HEK293) with genetically engineered IMPDH and TPMT activities.

RESULTS

Patients with metabolite ratios >20 had lower IMPDH activity than those with ratios ≤ 20 (P < 0.001). Metabolite ratios >20 were only observed in patients with normal TPMT activity. Downregulation of IMPDH activity in HEK293 cells was associated with an increase in the concentration of meTIMP (fold change: 17 up to 93, P < 0.001) but, unexpectedly, also of 6-thioguanosine monophosphate (fold change: 2.6 up to 5.0, P < 0.001).

CONCLUSIONS

These data question the general view of IMPDH as the rate-limiting enzyme in the phosphorylation of thiopurines. Investigations of other mechanisms are needed to more fully explain the various metabolite patterns and outcomes in patients under treatment.

Optimization of conventional therapy in patients with IBD

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

Common misconceptions about 5-aminosalicylates and thiopurines in inflammatory bowel disease

Misconceptions are common in the care of patients with inflammatory bowel disease (IBD). In this paper, we state the most commonly found misconceptions in clinical practice and deal with the use of 5-aminosalicylates and thiopurines, to review the related scientific evidence, and make appropriate recommendations. Prevention of errors needs knowledge to avoid making such errors through ignorance. However, the amount of knowledge is increasing so quickly that one new danger is an overabundance of information. IBD is a model of a very complex disease and our goal with this review is to summarize the key evidence for the most common daily clinical problems. With regard to the use of 5-aminosalicylates, the best practice may to be consider abandoning the use of these drugs in patients with small bowel Crohn’ s disease. The combined approach with oral plus topical 5-aminosalicylates should be the first-line therapy in patients with active ulcerative colitis; once-daily treatment should be offered as a first choice regimen due to its better compliance and higher efficacy. With regard to thiopurines, they seem to be as effective in ulcerative colitis as in Crohn’ s disease. Underdosing of thiopurines is a form of undertreatment. Thiopurines should probably be continued indefinitely because their withdrawal is associated with a high risk of relapse. Mercaptopurine is a safe alternative in patients with digestive intolerance or hepatotoxicity due to azathioprine. Finally, thiopurine methyltransferase (TPMT) screening cannot substitute for regular monitoring because the majority of cases of myelotoxicity are not TPMT-related.

Insight into the 6-thiopurine-mediated termination of the invasive motility of tumor cells derived from inflammatory breast cancer

Our study showed that a combination of 6-thiopurine (6-TP) drugs and a redox agent effectively inhibits the motility of SUM cells derived from human inflammatory breast cancer (IBC) cells and RhoC-overexpressed mammary epithelium cells. This 6-TP-mediated inhibition of cell motility occurs because the treated 6-TPs target and inactivate RhoC. A molecular mechanism for inactivation by the 6-TP-mediated RhoC is proposed by which treated TPs are converted in cells into 6-thioguanosine phosphate (6-TGNP). This 6-TGNP in turn reacts with the Cys(20) side chain of the redox-sensitive GXXXCGK(S/T)C motif of RhoC to produce a 6-TGNP-RhoC disulfide adduct. A redox agent synergistically enhances the formation process of this disulfide. The adduct that is formed impedes RhoC guanine nucleotide exchange, which populates an inactive RhoC. Our results suggest that 6-TGNP can also react with the redox-sensitive GXXXCGK(S/T)C and GXXXXGK(S/T)C motif of RhoA and Rac, respectively, to produce a 6-TGNP-RhoA and 6-TGNP-Rac disulfide adduct. However, given that RhoC has been shown to be overexpressed in ∼90% of IBC lesions, the populated RhoC but not other Rho proteins is likely to be a primary target for 6-TPs and a redox agent to terminate the metastasis of IBC.

Optimizing thiopurine therapy in inflammatory bowel disease

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

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

BACKGROUND

Circulating concentrations of 6-thioguanine nucleotide (6-TGN) and 6-methyl mercaptopurine (6-MMP) are associated with thiopurine efficacy and may predict toxicity. This study aimed to examine retrospectively the utility of measuring metabolite concentrations in patients with inflammatory bowel disease (IBD) who had continuing symptoms despite stable thiopurine treatment.

METHODS

Concentrations of 6-TGN and 6-MMP were measured in lysates of washed red cells by high-performance liquid chromatography in peripheral blood drawn from 63 symptomatic patients with IBD (63% men, mean age 37, range 14-74 years, 67% Crohn's disease, 33% ulcerative colitis) treated with azathioprine or 6-mercaptopurine. Short-term clinical outcomes were examined.

RESULTS

6-TGN concentrations weakly correlated with the thiopurine dose (r = 0.28, P = 0.08). On weight-based criteria, 50% of patients were underdosed. However, metabolite patterns suggested 7 (11%) patients were noncompliant, 18 (29%) were being underdosed, 33 (52%) were refractory to treatment with either appropriate (41%) or elevated (11%) metabolite concentrations, and 6 (10%) had a raised 6-MMP:6-TGN ratio consistent with aberrant thiopurine metabolism. The clinical outcome improved in 40 of 46 (87%) of patients in whom the course of action taken was as recommended by a metabolite-directed algorithm, while 3 of 17 patients (18%) improved where discordant actions were taken (P = 0.0001; Fisher's exact test). Fifteen patients (24%) avoided inappropriate escalation of therapy.

CONCLUSIONS

Dose-optimization or toxicity-avoidance strategies frequently result from metabolite testing in patients with inadequate efficacy from thiopurines, with evidence of better outcomes. Thiopurine metabolite testing is a potentially powerful tool for optimizing thiopurine usage in IBD.

Difficulties and possibilities with thiopurine therapy in inflammatory bowel disease--proceedings of the first Thiopurine Task Force meeting

BACKGROUND

Thiopurines, such as azathioprine and mercaptopurine, are of pivotal importance in the treatment of inflammatory bowel disease. Although these drugs have been used for several decades, still many questions remain unanswered.

AIM

To provide an overview of clinically and scientifically challenging topics concerning thiopurine therapy in inflammatory bowel disease treatment.

METHODS

The first meeting of the Thiopurine Task Force Interest Group was held during the 2009 United European Gastroenterology Week in London (GASTRO2009). The topics of this meeting were of particular clinical and scientific interest. Additional literature was identified by performing a Pubmed search using the search terms 'inflammatory bowel disease', 'azathioprine', '6-mercaptopurine' and 'thioguanine'.

RESULTS

The following topics were discussed: therapeutic drug monitoring; the synergy of thiopurines with aminosalicylates and allopurinol; serious adverse events such as opportunistic infections, hepatotoxicity, carcinogenicity and pancreatitis; prolongation of thiopurines during clinical remission; indications for thiopurines in the postoperative setting; and the potential use of thioguanine. Specific interesting and clinically relevant topics for potential future research are provided.

CONCLUSIONS

Thiopurines remain central to inflammatory bowel disease treatment, although future studies are required to substantiate a more personalised medicine approach to their use.

Using metabolomic analysis to understand inflammatory bowel diseases

Crohn's disease (CD) and ulcerative colitis (UC) are inflammatory bowel diseases (IBD) attributed to a dysregulated immune response towards intestinal microbiota. Although various susceptibility genes have been identified for CD and UC, the exact disease etiology is unclear and complicated by the influence of environmental factors. Metabolomic analysis enables high sample throughput measurements of multiple metabolites in biological samples. The use of metabolomic analysis in medical sciences has revealed metabolite perturbations associated with diseases. This article provides a summary of the current understanding of IBD, and describes potential applications and previous metabolomic analysis in IBD research to understand IBD pathogenesis and improve IBD therapy.

Azathioprine is effective in corticosteroid-dependent Asian inflammatory bowel disease patients

BACKGROUND

Azathioprine (AZA) is widely used to treat corticosteroid (CS)-dependent IBD patients but evidence supporting its use in Asian IBD patients is limited. We evaluated the efficacy of AZA in a single-center cohort of CS-dependent Asian IBD patients.

METHODS

Patients treated with AZA were identified from our registry and the medical records were reviewed. Inclusion criterion was: first course of AZA and treatment duration ≥ 6 months. Clinical response was assessed at 6 months and classified as complete response, partial response, and nonresponse. Factors associated with response (age, gender, ulcerative colitis [UC] extent, Crohn's disease [CD] behavior, ethnicity, concomitant 5-aminosalicylates/sulfasalazine, baseline activity, disease duration, leukocyte count, mean corpuscular volume, and AZA dose) were analyzed using the chi-square or Mann-Whitney U-test. Probability of sustained remission was estimated using the Kaplan-Meier method. Differences in survival curves between factors were tested with log-rank tests.

RESULTS

Sixty-four patients were included. At baseline the median age was 37.5 (range, 15-76) years, 50% male, 59.4% Chinese, 50% CD, 50% UC, and mean CS dose 20.2 (SD 10.9) mg. At month 6, complete response was 48.4% (95% confidence interval [CI], 36.7-61.3), partial response 45.1% (95% CI, 32.8-58.3), and nonresponse 7.8% (95% CI, 2.6-17.3). Partial responders had mean CS dose reductions of 11.7 mg (95% CI, 7.2-16.4, P < 0.001). The proportion of patients with sustained remission was 0.87 (95% CI, 0.73-1.0) at 2 years, 0.76 (95% CI, 0.57-0.95) at 3 years, and 0.61 (95% CI, 0.30-0.91) at 5 years of AZA treatment. Female gender was positively associated with sustained remission.

CONCLUSIONS

Our study demonstrates the short- and long-term effectiveness of AZA therapy among CS-dependent Asian IBD patients.

Thiopurine S-methyltransferase polymorphisms and thiopurine toxicity in treatment of inflammatory bowel disease

AIM: To evaluate the relationship between thiopurine S-methyltransferase (TPMT) polymorphisms and thiopurine-induced adverse drug reactions (ADRs) in inflammatory bowel disease (IBD).

METHODS: Eligible articles that compared the frequency of TPMT polymorphisms among thiopurine-tolerant and -intolerant adult IBD patients were included. Statistical analysis was performed with Review Manager 5.0. Sub-analysis/sensitivity analysis was also performed.

RESULTS: Nine studies that investigated a total of 1309 participants met our inclusion criteria. The incidence of TPMT gene mutation was increased 2.93-fold (95% CI: 1.68-5.09, P = 0.0001) and 5.93-fold (95% CI: 2.96-11.88, P < 0.00001), respectively, in IBD patients with thiopurine-induced overall ADRs and bone marrow toxicity (BMT), compared with controls. The OR for TPMT gene mutation in IBD patients with thiopurine-induced hepatotoxicity and pancreatitis was 1.51 (95% CI: 0.54-4.19, P = 0.43) and 1.02 (95% CI: 0.26-3.99, P = 0.98) vs controls, respectively.

CONCLUSION: This meta-analysis suggests that the TPMT polymorphisms are associated with thiopurine-induced overall ADRs and BMT, but not with hepatotoxicity and pancreatitis.

Review article: malignancy on thiopurine treatment with special reference to inflammatory bowel disease

BACKGROUND

Immunosuppression is a risk factor for carcinogenesis. Thiopurines specifically contribute to this. As thiopurines are used more aggressively in the treatment of IBD, it is likely that we will see more thiopurine-related malignancy.

AIM

To review the literature, exploring how immunosuppression, thiopurines specifically, might cause cancer and which malignancies occur in practice, placing specific emphasis on IBD cohorts.

METHODS

Search terms included 'malignancy' 'cancer' 'azathioprine' 'mercaptopurine' 'tioguanine (thioguanine)' 'thiopurine' and 'inflammatory bowel disease' 'Crohn's disease' 'ulcerative colitis'. We also searched for specific cancers (lymphoma, colorectal cancer, skin cancer, cervical cancer) and reviewed the reference lists of the articles detected.

RESULTS

Immunosuppression is associated with an increased risk of cancer. Thiopurines are associated with specific additional risks. In IBD cohorts, very few thiopurine-related malignancies have been reported. However, studies suggest a relative risk of 4-5 for lymphoma. This still translates into a low actual risk, (one extra lymphoma in every 300-1400 years of thiopurine treatment).

CONCLUSIONS

Whilst we must be aware of this risk and counsel our patients appropriately, thiopurines remain a mainstay of IBD therapy. We present practical advice aimed at minimizing our patients' risk of developing malignancy, whilst optimizing the benefits that thiopurines can provide.

Differences among allelic variants of human glutathione transferase A2-2 in the activation of azathioprine

Azathioprine has been clinically used for decades in connection with organ transplantation, autoimmune disease, and treatment of cancer. Toxic side-reactions are common and have been linked to the liberation of excessively high concentrations of 6-mercaptopurine and corresponding toxic metabolites. An allelic variant of thiopurine methyltransferase with low activity is associated with elevated concentrations of 6-mercaptopurine. However, other genetic markers remain to be identified in order to fully account for adverse reactions and efficacy failure. In the present study, we studied the five known allelic variants of human glutathione transferase A2-2 (GST A2-2) (EC 2.5.1.18), abundantly expressed in liver and efficiently catalyzing the bioactivation of azathioprine to release 6-mercaptopurine. All five variants exhibited high activity with azathioprine, but allelic variant E of GST A2-2 displayed a 3-4-fold elevated catalytic efficiency compared to the other variants. High GST activity can lead to overproduction of 6-mercaptopurine, and the nature of the multiple forms of GSTs in a patient will obviously affect the metabolism of azathioprine. In addition to GST A2-2, the polymorphic GST M1-1 is also highly active with azathioprine. Considering our findings, it appears that the genotypic and phenotypic variations in the GST complement may influence the presentation of adverse reactions in patients treated with azathioprine. Clinical trials will be required to clarify the impact of the GST expression in comparison with the established biomarker thiopurine methyltransferase as predictors of adverse reactions.

Inflammatory bowel disease in Korea: epidemiological, genomic, clinical, and therapeutic characteristics

Inflammatory bowel disease (IBD) describes chronic inflammatory disease of the intestines and has a variable course; Crohn's disease and ulcerative colitis comprise the two main forms of the condition. Although IBD occurs worldwide, its epidemiologic and clinical characteristics vary depending upon the geographic location and the ethnicity of the population. Identifying the characteristic features of IBD in populations living in different geographical locations and with different ethnicities may provide significant clues about its etiology and pathophysiology, which in turn may be helpful in the development of more appropriate treatment strategies for IBD for these different populations. Therefore, it is important for each country and region to evaluate critically the epidemiology, genomics, and clinical characteristics of IBD among its own population. We have performed a critical review of the recent data in Korea, and describe herein the current epidemiologic and genotypic status, as well as the clinical manifestations and therapeutic responses of IBD that are unique to Korean patients.

Managing the risks of IBD therapy

Successful management of the patient with inflammatory bowel disease (IBD) involves not only the induction and maintenance of remission, but also the optimization of the benefit-to-risk equation to achieve the greatest gain in quality of life. These risks range from intolerance to prescribed medications to potentially life-threatening sequelae (eg, sepsis) of immune suppression. A proper awareness of risk on the part of the physician and education of the patient can lead to early detection and institution of an appropriate management plan, including risk management and, optimally, primary prevention (eg, prophylactic vaccination). One should take the opportunity regularly to reassess the utility and efficacy of existing therapy, with the provision of ineffective therapies mandating urgent review. Overall, optimal management of the patient with IBD requires open dialogue between clinician and patient so that both are cognizant of the goals, benefits, and potential risks of therapy.

Un-promoted issues in inflammatory bowel disease: opportunities to optimize care

Inflammatory bowel diseases (IBD), comprising Crohn's disease (CD) and ulcerative colitis (UC), are chronic inflammatory disorders of the gut, which lead to significant morbidity and impaired quality of life (QoL) in sufferers, without generally affecting mortality. Despite CD and UC being chronic, life-long illnesses, most medical management is directed at acute flares of disease. Moreover, with more intensive medical therapy and the development of biological therapy, there is a risk that management will become even more narrowly focused on acute care, and be directed only at those with more severe disease, rather than encompassing all sufferers and addressing important non-acute issues. This imbalance of concentration of medical attention on 'high-end' care is in part driven by the need to perform and publish randomized clinical trials of newer therapies to obtain registration and licensing for these agents, which thus occupy a large proportion of the recent IBD treatment literature. This leads to less attention on relatively 'low-technology' issues including: (i) the psychosocial burden of chronic disease, QoL and specific psychological comorbidities; (ii) comorbidity with functional gastrointestinal disorders (FGIDs); (iii) maintenance therapy, monitoring and compliance; (iv) smoking (with regard to CD); (v) sexuality, fertility, family planning and pregnancy; and (vi) iron deficiency and anaemia. We propose these to be the 'Un-promoted Issues' in IBD and review the importance and treatment of each of these in the current management of IBD.

Effects of interactions of antibacterial drugs with each other and with 6-mercaptopurine on in vitro growth of Mycobacterium avium subspecies paratuberculosis

OBJECTIVES

Mycobacterium avium subspecies paratuberculosis (MAP) has been targeted for treatment with clarithromycin and rifamycin derivatives in numerous cases of Crohn's disease (CD). 6-Mercaptopurine and its pro-drug azathioprine are widely used as immunomodulators in the treatment of CD and have recently been shown to have anti-MAP activity in vitro. The objectives of the study were to evaluate the in vitro effects on MAP of (i) 6-mercaptopurine when combined with each of eight conventional antibacterial agents with in vitro anti-MAP activity and (ii) antibacterial combinations consisting of two drugs (clarithromycin combined with amikacin, rifampicin, ciprofloxacin or ethambutol) and three drugs (clarithromycin, rifabutin and clofazimine).

METHODS

The drug interaction effects on nine human isolates of MAP were determined by the chequerboard method adapted for the BACTECMGIT960 culture system and by calculation of the fractional inhibitory concentration index (FICI) for drug combinations.

RESULTS

Synergism (FICI < or = 0.5) was observed between 6-mercaptopurine and azithromycin (seven isolates), clarithromycin, rifampicin, rifabutin (four isolates each) and ethambutol (two isolates). 6-Mercaptopurine was not antagonistic with any of the antibacterial agents tested. Among the combinations of two and three antibacterials tested, the clarithromycin/rifampicin combination was synergistic against four isolates, while all other combinations showed no interaction.

CONCLUSIONS

This in vitro study suggests that 6-mercaptopurine may be synergistic with macrolides and rifamycin derivatives against MAP. The activity of clarithromycin against MAP seems to be enhanced by rifampicin.

Thiopurine methyltransferase and thiopurine metabolite testing in patients with inflammatory bowel disease who are taking thiopurine drugs

Thiopurine methyltransferase genotyping and thiopurine metabolite testing has been established as an adjunct to monitoring patients taking thiopurine drugs. This special report describes the clinical implications for this type of testing for patients with inflammatory bowel disease who are taking thiopurine drugs. A total of 10% of patients were found to be intermediate metabolizers and the mean dosage (in mg/kg equivalent) was lower in intermediate metabolizers than extensive metabolizers. The metabolite levels did not correlate with scores measuring clinical severity but levels of 6-methylmercaptopurine were related to the dosage of the drugs. Despite considerable study of thiopurine methyltransferase testing in the literature, it is still not widely used in many geographical areas. This study adds to the evidence about using such testing as well as expanding the role of simultaneously measuring thiopurine metabolites. Further work is planned to evaluate the uptake when such testing becomes available locally as a clinical service.

Pediatric inflammatory bowel diseases and the risk of lymphoma: should we revise our treatment strategies?

Inflammatory bowel diseases (IBDs) are lifelong inflammatory gastrointestinal diseases starting in about one third of patients during childhood. Treatment strategies aim to control this chronic inflammatory process. Owing to recent advances in the understanding of IBD, immunosuppressive agents (mainly against TNFalpha directed) as well as biological drugs are more and more often used. This therapeutic approach clearly improved the clinical condition of the majority of patients with IBD. However, with this more aggressive treatment strategy, safety concerns clearly arise. Recently, the description of a series of a particularly severe form of T cell lymphoma in pediatric and young adult patients with IBD under immunomodulator and biological combination therapy raised the question of the risks of treatment-induced side effects or complications. As reviewed in the present article, there is a slightly increased risk of not only lymphoma development in IBD patients, potentially related to the inflammatory process, but also to the use of immunosuppressive therapies. On the basis of the literature data, were analyzed current treatment strategies for children with moderate-to-severe IBD, who are candidates to receive immunomodulator and/or biological agents potentially accelerating the risk of lymphoma development. Comparative clinical studies in IBD are still missing; however, it is prudent to think about adapting immunosuppressive therapies to the inflammatory process of the underlying disorder and if possible to reduce them to monotherapy. Alternative treatment strategies for heavy immunosuppression exist (eg, enteral nutrition in Crohn disease or colectomy in patients with ulcerative colitis) and should be considered whenever appropriate. There is a major need for comparative studies before evidence-based guidelines can be established for safest and best treatment strategies of pediatric patients with IBD.

[Pharmacological and pharmacogenetic study of two immunomodulators: azathioprine and 6-mercaptopurine. Strategies for preventing complications]

Thiopurines are frequently used in gastroenterology for Crohn's disease or hemorrhagic rectocolitis. Their metabolism is regulated by a particular enzyme, thiopurine S-methyltransferase or TPMT. There are three ways to evaluate the effectiveness and the risk of side effects associated with this treatment. TPMT activity measurement or genotyping are recommended to decide for treatment, while metabolites determination is a used as marker of monitoring. Phenotypic approach (TPMT activity measurement or metabolites determination) requires delicate techniques and interindividual variations make the interpretation difficult. Genotyping is easier to interpret but cannot exclude some risk of side effects.

Improving pharmacovigilance in Europe: TPMT genotyping and phenotyping in the UK and Spain

Thiopurine S-methyltransferase (TPMT) is the rate-limiting step in the conversion of thiopurine drugs including azathioprine (AZA) to inactive metabolites. Heritable deficiency of TPMT activity increases risk for adverse events, most notably, myelosuppression leading to leukopenia and neutropenic sepsis. The reported European Commission study was undertaken to identify current evidence for the clinical utility of testing for TPMT status and extent of uptake, by either genotyping or phenotyping, in the clinical setting. Data presented here for the UK and Spain indicate that there has been a considerable increase in the uptake of TPMT testing in recent years. There are some data that support routine TPMT testing before AZA prescribing for reducing AZA-related adverse events. Key data include evidence in favor of TPMT testing in addition to the current practice of routine monitoring for reducing the number of AZA-related episodes of myelosuppression, averting deaths from neutropenic sepsis and improving health-related quality of life. Further data are needed for determining the cost-effectiveness of routine TPMT testing.

Azathioprine or 6-mercaptopurine for maintenance of remission in Crohn's disease

BACKGROUND

The therapeutic role of 6-mercaptopurine and azathioprine remains controversial due to their perceived relatively slow-acting effect and adverse effects. A meta-analysis was performed to evaluate the efficacy of these agents for the maintenance of remission of quiescent Crohn's disease.

OBJECTIVES

To assess the efficacy of azathioprine and 6-mercaptopurine for maintenance of remission in quiescent Crohn's disease.

SEARCH STRATEGY

Pertinent studies were selected using the MEDLINE data base (1966-May 1998), the Cochrane Controlled Trials Register, the Inflammatory Bowel Disease register, as well as abstracts from major gastrointestinal research meetings and references from published articles and review. This search strategy was updated (1998-May 2008) using the MEDLINE, EMBASE and International Pharmaceutical Abstracts databases, the Cochrane Central Register of Controlled Trials and the Cochrane IBD/FBD group Specialized Trials Register.

SELECTION CRITERIA

Randomized, double-blind, placebo-controlled trials of oral azathioprine or 6-mercaptopurine involving adult patients (> 18 years) with quiescent Crohn's disease.

DATA COLLECTION AND ANALYSIS

Data were extracted by three independent observers (EP, MC, LRS) based on the intention to treat principle. Peto odds ratios and 95% confidence intervals for maintenance of remission, steroid sparing, and withdrawals due to adverse effects were calculated. Numbers needed to treat or harm (NNT, NNH respectively) for the maintenance of remission, steroid sparing, and withdrawals due to adverse effects were also determined.

MAIN RESULTS

Seven trials of azathioprine therapy and one of 6-mercaptopurine were included in the review. Azathioprine and 6-mercaptopurine had a positive effect on maintaining remission. The Peto odds ratio (OR) for maintenance of remission with azathioprine was 2.32 (95% CI 1.55 to 3.49) with a NNT of 6. The Peto OR for maintenance of remission with 6-mercaptopurine was 3.32 (95% CI 1.40 to 7.87) with a of 4. Higher doses of azathioprine improved response. A steroid sparing effect with azathioprine was noted, with a Peto OR of 5.22 (95% CI 1.06 to 25.68) and NNT of 3 for quiescent disease. Withdrawals due to adverse events were more common in patients treated with azathioprine (Peto OR 3.74; 95% CI 1.48 to 9.45, NNH = 20) than with placebo.

AUTHORS' CONCLUSIONS

Azathioprine and 6-mercaptopurine are more effective than placebo for maintenance of remission in Crohn's disease. Higher response rates were obtained with azathioprine than 6-mercaptopurine. However, the one study evaluating 6-mercaptopurine used a relatively low dose of the drug. Future studies should look at the effect of higher doses of 6-mercaptopurine. There is weak evidence for a steroid sparing effect with azathioprine treatment.

Thiopurine hepatotoxicity in inflammatory bowel disease: the role for adding allopurinol

BACKGROUND

Immunomodulator therapy with the thiopurine analogues azathioprine or 6-mercaptopurine is commonly prescribed for the treatment of inflammatory bowel disease (IBD). Drug adverse effects and the lack of efficacy, however, commonly require withdrawal of therapy. Allopurinol, a xanthine oxidase inhibitor, was recently evaluated in its role in modifying thiopurine metabolism and improving drug efficacy in IBD.

OBJECTIVE

This article reviews the role and safety of allopurinol co-therapy in the setting of thiopurine hepatotoxicity and/or non-responsiveness in IBD.

METHODS

Published articles on thiopurines in the treatment of IBD were examined.

CONCLUSION

The addition of low dose allopurinol to dose-reduced thiopurine analogue seems safe but careful monitoring for adverse effects and profiling of thiopurine metabolites is essential. There is evidence of improved immunomodulator efficacy and reduced hepatotoxicity clinically but further confirmatory studies are required before more definitive treatment recommendations can be given.

Monitoring 6-thioguanine nucleotide concentrations in Japanese patients with inflammatory bowel disease

BACKGROUND AND AIM

There have been no reports on 6-thioguanine nucleotide (6-TGN) concentrations in Japanese patients with inflammatory bowel disease (IBD) undergoing azathioprine (AZA) or 6-mercaptopurine (6-MP) therapy. The aim of this study was to assess 6-TGN concentrations in Japanese IBD patients.

METHODS

Eighty-three patients with Crohn's disease (n = 42) and ulcerative colitis (n = 41) were enrolled. In 69 patients, AZA was prescribed at 50 mg/day, and seven patients were given 75 (n = 5) or 100 mg/day (n = 2). 6-MP was administered at 30 mg/day (n = 7). The 6-TGN concentrations were then assayed by high-performance liquid chromatography.

RESULTS

The mean 6-TGN concentrations of the entire study population (n = 83) were 277.9 +/- 179.8 pmol/8 x 10(8) red blood cells (RBC). The mean 6-TGN concentrations in those patients with active disease (n = 38) and those in remission (n = 45) were 232.9 +/- 159.7(mean +/- SD) and 342.8 +/- 184.6 pmol/8 x 10(8) RBC, respectively (P < 0.05). The odds ratio of being in remission and having a 6-TGN value >235 pmol/8 x 10(8) RBC was 2.6 (95% CI 1.05-6.2). A significant inverse correlation was found between the white blood cell (WBC) counts and 6-TGN concentrations (r = -0.301, P < 0.05, n = 83); the mean WBC counts of the active patients (6780 +/- 2412) were significantly higher than the patients in clinical remission (5468 +/- 1920, P < 0.05). Three patients with severe leukopenia and 10 patients with high 6-TGN concentrations had no thiopurine S-methyl transferase mutations.

CONCLUSION

The 6-TGN concentrations in Japanese patients with IBD on low-dose AZA and 6-MP therapy were comparable to those reported from Western countries. The monitoring of 6-TGN concentrations may be helpful for developing a therapeutic strategy for Japanese IBD patients.

Predictive factors associated with immunosuppressive agent use in ulcerative colitis: a case-control study

BACKGROUND

Some patients with ulcerative colitis (UC) require immunosuppressants as maintenance therapy.

AIM

To assess epidemiological, clinical and disease factors at diagnosis that predict immunosuppressant use in UC.

METHODS

All UC patients diagnosed between 1992 and 2005 and currently managed in the inflammatory bowel disease (IBD) clinic were included. Forty-three patients who currently or previously received azathioprine (AZA) or mercaptopurine (MP) for UC were compared with 130 controls. Charts were reviewed and logistic regression analyses were applied to identify factors associated with AZA or MP use.

RESULTS

In univariate model, seven factors at diagnosis correlated with AZA use: male gender [odds ratio (OR) 2.2]; left-sided or extensive colitis or pancolitis (OR 8.7-14.1); systemic steroid use within the first 6 months of diagnosis (OR 5.1); more than 10 bowel movements daily (OR 6.4); persistent or mostly blood in stool (OR 2.8); endoscopic proven moderate to severe disease (OR 7.2-12.0) and requirement of hospitalization (OR 2.7) on diagnosis. In multivariate model, the first three factors were shown to be statistically significant.

CONCLUSION

Male gender, initial presentation with severe and extensive disease clinically and endoscopically, requirement of hospitalization on diagnosis or systemic steroids within 6 months of diagnosis are predictive factors for immunosuppressant use in UC.