Review article: the benefits of pharmacogenetics for improving thiopurine therapy in inflammatory bowel disease

Drug rediscovery in gastroenterology: from off-label to on-label use of thioguanine in inflammatory bowel disease

Drug rediscovery refers to the principle of using 'old' drugs outside the indications mentioned in the summary of product characteristics. In the past decades, several drugs were rediscovered in a wide variety of medical fields. One of the most recent examples is the unconditional registration of thioguanine (TG), a thiopurine derivative, in patients with inflammatory bowel disease in the Netherlands. In this paper, we aim to visualise potential hurdles that hamper drug rediscovery in general, emphasise the global need for optimal use and development of potentially useful drugs, and provide an overview of the registration process for TG in the Netherlands. With this summary, we aim to guide drug rediscovery trajectories in the near future.

Development and validation of a novel HPLC-UV method for simultaneous determination of azathioprine metabolites in human red blood cells

A rapid, specific and accurate high-performance liquid chromatography with tunable ultraviolet detection method was developed to simultaneously determine azathioprine metabolites, 6-thioguanine nucleotides (6-TGN) and 6-methyl mercaptopurine riboside (6-MMPr) in human red blood cells. Erythrocyte lysate sample was precipitated by perchloric acid under the protection of dithiothreitol, with 6-TGN and 6-MMPr being acid hydrolyzed to produce 6-thioguanine (6-TG) and 6-methymercaptopurine (6-MMP). A Waters Cortecs C₁₈ column (2.1 × 150 mm, 2.7 μm) was used for chromatographic separation with a water (containing 0.01 mol/L ammonium acetate and 0.2% acetic acid)/methanol linear gradient at a flow rate of 0.45 mL/min in a 5.5 min. UV detection wavelengths were 340 nm for 6-TG, 303 nm for 6-MMP and the IS (5-bromouracil). The calibration curves fitted a least squares model (weighed 1/x ²) from 0.15 to 15 μmol/L for 6-TG (r ²  = 0.9999) and from 1 to 100 μmol/L for 6-MMP (r ²  = 0.9998). This method was validated according to the FDA bioanalytical method validation guidance and ICH M10 bioanalytical method validation and study sample analysis guidance for industry, and successfully utilized in ten IBD patients receiving azathioprine therapy.

Genetic and Epigenetic Etiology of Inflammatory Bowel Disease: An Update

Inflammatory bowel disease (IBD) is a chronic disease with periods of exacerbation and remission of the disease. The etiology of IBD is not fully understood. Many studies point to the presence of genetic, immunological, environmental, and microbiological factors and the interactions between them in the occurrence of IBD. The review looks at genetic factors in the context of both IBD predisposition and pharmacogenetics.

Thiopurine S-Methyltransferase Polymorphisms Predict Hepatotoxicity in Azathioprine-Treated Patients with Autoimmune Diseases

Thiopurine methyltransferase (TPMT) is the rate-limiting enzyme in Azathioprine (AZA) metabolization. Although studies have discussed the association between the TPMT polymorphisms and myelosuppression, the data about the relationship between TPMT genotypes and hepatoxicity in Asian patients remain limited. This study investigated the correlation between TPMT polymorphisms and AZA-related hepatotoxicity. This study enrolled the patients who had prior exposure to AZA from the Taichung Veterans General Hospital (TCVGH)-Taiwan Precision Medicine Initiative (TPMI) cohort. Genetic variants were determined using a single nucleotide polymorphism (SNP) array. Participants were accordingly categorized into normal metabolizer (NM) and non-normal metabolizer (non-NM) groups. From the TCVGH-TPMI cohort, we included 50 TPMT non-NM patients, including 1 poor metabolizer (PM), 49 intermediate metabolizers (IMs), and 1000 NM patients. The non-NM genotype was associated with hepatotoxicity compared with the NM genotype (hazard ratio (HR): 3.85, 95% confidence interval (CI): 1.83−8.10). In the non-NM group, the 3-year cumulative incidence of hepatotoxicity was higher than that in the NM group at 8.5% in the first year and 18.6% in the second and third years (p < 0.001). A TPMT non-NM genotype was associated with the occurrence of hepatotoxicity following AZA therapy. Preemptive testing helps individualize AZA therapy by minimizing the risk of hepatotoxicity.

Anti-Inflammatory Activity of an In Vitro Digested Anthocyanin-Rich Extract on Intestinal Epithelial Cells Exposed to TNF-α

Background: The consumption of foods rich in anthocyanins (ACN) have been associated with beneficial properties in chronic inflammatory disorders such as intestinal bowel diseases (IBD). These effects were attributed not only to a direct antioxidant mechanism but also to the modulation of cell redox-dependent signaling. However, ACN bioavailability is low for their poor stability in the digestive tract, so ACN gastrointestinal digestion should be considered. Methods: To have a more realistic knowledge of the effects of ACN, we performed an in vitro simulated gastrointestinal digestion of an ACN-rich purified and standardized bilberry and blackcurrant extract (BBE), followed by an evaluation of ACN composition modification (HPLC-DAD and pH differential method) and antioxidant activity (FRAP assay). Then, we studied the effects of BBE gastrointestinal extract on Caco-2 exposed to TNF-α. Results: The results confirmed the high instability of ACN in the mild alkaline environment of the small intestine (17% recovery index). However, the digested BBE maintained part of its bioactivity. Additionally, BBE gastrointestinal extract inhibited the TNF-α-induced NF-κB pathway in Caco-2 and activated the Nrf2 pathway. Conclusions: Although ACN stability is affected by gastrointestinal digestion, the anti-inflammatory and antioxidant activity of digested extracts were confirmed; thus, the loss of ACN can probably be counterweighed by their metabolites. Then, ACN introduced by diet or food supplements could represent an approach for IBD prevention.

Association of genetic variants in TPMT, ITPA, and NUDT15 with azathioprine-induced myelosuppression in southwest china patients with autoimmune hepatitis

This study aimed to investigate the influence of TPMT*3C, ITPA, NUDT15, and 6-thioguanine nucleotides (6-TGN) on azathioprine (AZA)-induced myelosuppression in Southwest China patients with autoimmune hepatitis (AIH). A total of 113 Chinese patients with AIH receiving AZA maintenance treatment were evaluated. The relevant clinical data of the patients were collected from the hospital information system. Genotyping of TPMT*3C(rs1142345), ITPA (rs1127354) and NUDT15(rs116855232) was conducted using a TaqMan double fluorescent probe. The concentration of 6-TGN was determined using UPLC-MS/MS. Among AIH patients treated with AZA, 40 (35.4%) exhibited different degrees of myelosuppression. The NUDT15 variant was associated with leukopenia (P = 8.26 × 10^–7; OR = 7.5; 95% CI 3.08–18.3) and neutropenia (P = 3.54 × 10^–6; OR = 8.05; 95% CI 2.96–21.9); however, no significant association with myelosuppression was observed for TPMT*3C and ITPA variants (P > 0.05). There was no significant difference in 6-TGN concentration between AIH patients with or without myelosuppression (P = 0.556), nor was there a significant difference between patients with variant alleles of TPMT*3C, ITPA, or NUDT15 and wild-type patients (P > 0.05). Interestingly, it was found that patients with a lower BMI had higher adjusted 6-TGN levels and a higher incidence of myelosuppression (P = 0.026 and 0.003). This study confirmed that NUDT15 variants are a potential independent risk predictor for AZA-induced leukopenia and neutropenia. BMI may be a crucial non-genetic factor that affects the concentration of AZA metabolites and myelosuppression. In addition, the 6-TGN concentration in red blood cells does not reflect the toxicity of AZA treatment, and new biomarkers for AZA therapeutic drug monitoring need further research.

Predictors of azathioprine toxicity in children with autoimmune hepatitis

Aim of the study

Azathioprine (AZA) is an important steroid-sparing drug in the management of autoimmune hepatitis (AIH). Avoidance of its adverse events that could be severe and carry a risk of mortality in a few cases is important, preferably with cheap and easy assessments that could be feasible in developing countries with the unavailability of molecular assays. Assessment of thiopurine methyltransferase (TPMT), the key enzyme for the inactivation of AZA, as a predictor of AZA toxicity had been a matter of conflict. This work aimed to study the role of TPMT serum level assessment and other host-, disease-, and treatment-related factors in predicting AZA toxicity.

Material and methods

Sixty-six children with AIH, divided into two groups, were recruited. Group 1 included twelve children with AZA toxicity and group 2 included fifty-four children without AZA toxicities. Both groups were compared for demographic, clinical, laboratory, histopathological, and treatment-related factors, and serum TPMT level, measured by ELISA.

Results

TPMT serum level was comparable in both groups (p = 0.363). Duration of treatment until enzyme normalization and duration of AZA therapy were significantly associated with AZA toxicity (p = 0.007 and p = 0.01, respectively). At the first follow-up treatment with AZA, total leucocyte count (TLC) and neutrophil counts were significantly lower in group 1 (p = 0.005 and p = 0.002, respectively). Moreover, the percentage reduction of TLC and neutrophil counts were significantly higher in group 1 (p < 0.001, for both).

Conclusions

Monitoring for AZA adverse events in those with the defined predictors of AZA-related adverse events is more important than TPMT assessment.

Identification of rare defective allelic variants in cases of thiopurine S-methyltransferase deficient activity

Aim: To assess rare TPMT variants in patients carrying a deficient phenotype not predicted by the four more frequent genotypes (*2, *3A, *3B and *3C). Materials & methods: Next-generation sequencing of TPMT in 39 patients with a discordant genotype. Results: None of the variants identified explained the discordances assuming that they are of uncertain significance according to the Clinical Pharmacogenetics Implementation Consortium classification. Two unknown variants were detected and predicted to result in a splicing defect. We show that TPMT*16 and TMPT*21 are defective alleles, and TPMT*8 and TPMT*24 are associated with a normal activity. Conclusion: Whole-exon sequencing for rare TPMT mutations has a low diagnostic yield. A reassessment of the functional impact of rare variants of uncertain significance is a critical issue.

Porous graphitic carbon based chromatography hyphenated with mass spectrometry: A new strategy for profiling thiopurine nucleotides in patients with inflammatory bowel diseases

Thiopurine (TP) treatment is discontinued in up to 30% of patients suffering from inflammatory bowel diseases (IBD) due to various adverse effects. Therapeutic drug monitoring of biologically active TP metabolites, i.e. thiopurine nucleotides (TPN), can help to optimize the efficacy and safety of the TP treatment. In our work, a novel strategy for TPN profiling, based on a porous graphitic carbon (PGC) chromatography, was developed. The validated PGC-MS method was compared with ion-exchange LC-MS, a currently leading analytical approach established for the determination of TPN. The innovative approach enabled an enhancement of several key performance parameters demanded in a clinical routine use, namely (i) selectivity (time- and mass-recognition of all 12 TPN in one run), (ii) sensitivity (2-5-fold increase in intensities of the analytical signals), (iii) sample throughput (25% shorter analysis time). Application of the novel TPN profiling strategy to a pilot clinical study (12 patients) revealed significantly higher levels of 6-methylthioguanine 5'-diphosphate (MeTGDP) in non-responsive IDB patients treated with azathioprine. Some other TPN are very close to the critical level (p = 0.05) and they will need larger groups of IBD patients to confirm definitively their relevance. In conclusion, the developed PGC-MS method represents a significant improvement to currently available methods for detailed profiling of TPN and its use in bigger clinical studies should lead to a better understanding of the relationship between TPN profiles and therapeutic outcome.

Exploring two-dimensional graphene and boron-nitride as potential nanocarriers for cytarabine and clofarabine anti-cancer drugs

Development in two-dimensional (2D) drug-delivery materials have quickly translated into biological and pharmacological fields. In this present work, pristine graphene (PG) and hexagonal boron nitride (h-BN) sheets are explored as a drug carrier for cytarabine (CYT) and clofarabine (CLF) anti-cancer drugs using density functional theory (DFT). The obtained geometrical, energetic and electronic properties revealed that the PG sheet is more reactive and it adsorbs CYT and CLF anti-cancer drugs better than the h-BN sheet. The adsorption energies of CYT and CLF on PG sheet is -24.293 and -23.308 kcal/mol respectively, this is due to the delocalized electrons present in the PG sheet. The flow of electron direction between anti-cancer drugs and 2D sheet are calculated by ΔN, ΔE_A(B), and ΔE_B(A) parameters and Natural bond orbital analysis (NBO). The electronic and optical properties are calculated to understand the chemical reactivity and stability of the complex systems. The obtained results exhibit that the PG sheet retains significant therapeutic potential as a drug delivery vehicle for a drug molecule to treat cancer therapy.

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.

Role of Thiopurines in Pediatric Inflammatory Bowel Diseases: A Real-Life Prospective Cohort Study

OBJECTIVES

Use of thiopurines for inflammatory bowel diseases (IBDs) is declining in some parts of the world. We aimed to explore outcomes of thiopurines and predictors of response in a real-world prospective cohort of children with dose optimization.

METHODS

Children with IBD treated with thiopurines without biologics were enrolled. Dosing was guided by thiopurine S-methyltransferase-activity at baseline and by clinical response and toxicity at 4 months; 1 year into the study, therapeutic drug monitoring at 4 months was also considered in the decision making. The primary outcome was steroid-free remission without treatment escalation by 12 months (SFR), using the intention-to-treat approach.

RESULTS

A total of 129 children were included (74% Crohn disease [CD] and 26% ulcerative colitis [UC]). SFR was achieved in 37 (39%) CD and 13 (39%) UC patients, and SFR with normal erythrocyte sedimentation rate/C-reactive protein in 20 (21%) and 9 (27%), respectively. At 4 months, mean corpuscular volume/white blood cell ratio and Δ absolute neutrophil count weakly correlated with 6-thioguanine (r = 0.33, P = 0.02 and r = 0.32, P = 0.02, respectively). In CD, SFR was associated with 4-month median weighted Pediatric Crohn Disease Activity Index (2.5 [IQR 0-7.5] in responders vs 5 in nonresponders [0-12.5], P = 0.048) and Δabsolute neutrophil count (1.7 [IQR 0.7-4.1] vs 0.05 [-2.3-0.9]; P = 0.03). Mild drug-related adverse events were recorded in 30 children (22%), 3 required stopping the drug.

CONCLUSIONS

In this real-life prospective cohort using dose optimization, thiopurines were safe and effective in 21% of CD and 27% of UC patients, including normalization of C-reactive protein and erythrocyte sedimentation rate. Thiopurines remain a viable option in the treatment algorithm of mild-moderate pediatric IBD, especially in girls whose risk for lymphoma is lower.

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

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

Highly sensitive and rapid determination of azathioprine metabolites in whole blood lysate by liquid chromatography-tandem mass spectrometry

Individualized therapy involves genetic test of drug metabolism, which provides information about the initial dose and therapeutic drug monitoring for adjusting the subsequent dose. Consequently, toxic side effects are expected to be minimized and therapeutic effects to be maximized. In this study, an ultra-performance liquid chromatography tandem mass spectrometry method that was specific, accurate and sensitive was developed to simultaneously determine azathioprine two metabolites, 6-thioguanine nucleotides (6-TGN) and 6-methyl-mercaptopurine riboside (6-MMPr) in the whole blood lysate. We precipitated the sample by trifluoroacetic acid under the protection of dithiothreitol, with 6-MMPr and 6-TGN being hydrolyzed to produce 6-methymercaptopurine and 6-thioguanine. In the chromatographic separation, Waters ACQUITY BEH C18 (2.1 × 100 mm, 1.7 μm) chromatographic column was applied and gradient elution was conducted with 0.02 mol/L ammonium acetate buffer (which contains 0.3% formic acid) and acetonitrile at a flow rate of 0.4 ml/min. Tandem mass spectrometry in multiple reaction monitoring mode was applied for detection via electrospray ionization source in positive ionization mode. The analyzing process lasted for no more than 2 min. The calibration curve for each metabolite fitted a least squares model (weighed 1/X) from 1.25 to 5000 ng/ml (r² > 0.99). The ion pairs were detected as 6-MMP m/z 167.07 → 152.15, 6-TG m/z 168.06 → 134.13, and internal standard m/z 171.07 → 137.14. Under the guidance of FDA guidelines for bioanalytical method validation, we carried out validation and obtained satisfactory results. The method was successfully utilized for monitoring the concentrations of each metabolite from 65 affected patients who had received azathioprine maintenance therapy and achieved optimal results.

Correlation between Thiopurine S-Methyltransferase Genotype and Adverse Events in Inflammatory Bowel Disease Patients

Background and Objectives: In patients with inflammatory bowel diseases (IBD), the use of azathioprine results in adverse events at a rate of 5% to 20%. The aim of the study was to assess a possible correlation between genetic variability of the enzyme thiopurine S-methyltransferase (TPMT) and the development of toxicity to azathioprine. Materials and Methods: A retrospective, single center, blind, case-control study was conducted on 200 IBD patients, of whom 60 cases suspended azathioprine due to toxicity (leukopenia, pancreatitis, hepatitis, and nausea or vomiting), and 140 controls continued treatment with the drug without adverse events. Results: In the entire cohort, only 8 cases of heterozygous mutations of TPMT were observed, corresponding to 4% mutated haplotype rate, much lower than that reported in literature (close to 10%). No homozygous mutation was found. Regarding the TPMT allelic variants, we did not find any statistically significant difference between patients who tolerated azathioprine and those who suffered from adverse events. (OR = 0.77, 95% CI = 0.08–7.72; p = 0.82). Conclusions: According to our study, in IBD patients, the search for TPMT gene mutations before starting treatment with azathioprine is not helpful in predicting the occurrence of adverse events. Importantly, patients with allelic variants should not be denied the therapeutic option of azathioprine, as they may tolerate this drug.

Development and validation of a UPLC-UV method for the quantification of thiopurine methyltransferase enzyme activity in human erythrocytes

Thiopurines are drugs widely used for the treatment of autoimmune conditions, inflammatory bowel disease or acute lymphoblastic leukemia. Determination of thiopurine methyltransferase activity (TPMT), a major determinant of thiopurines toxicity, has been suggested before implementing thiopurine treatment. An ultraperformance liquid chromatography (UPLC) method was developed and validated for the quantification of TPMT enzyme activity based on the conversion of 6-mercaptopurine (6-MP) to 6-methylmercaptopurine (6-MMP) using S-adenosyl-L-methionine (SAM) as methyl donor in red blood cell lysates (RBC). This method was improved from a previous laborious high performance liquid chromatography (HPLC) method, using a lower volume of injection and with a shorter runtime. After incubation and protein precipitation 6-MMP was separated on a HSS-T3 (2.1 × 50 mm, 1.8 μm) column and monitored by UV detection (290 nm). A change on the organic solvent used to dissolve 6-MP resulted in a reduction of interference by endogenous or non-enzymatic methylated 6-MMP. A full validation of the 6-MMP assay was performed according to the FDA and EMA guidelines. The method was linear from 0.125 to 2 nmol/mL, with acceptable values of accuracy and precision. The method was applied in 106 patients treated with thiopurines whose TPMT activity was previously quantified by HPLC. Evaluation through Bland-Altman plot showed that TPMT activities were in agreement between both methods.

Modeling the Outcome of Systematic TPMT Genotyping or Phenotyping Before Azathioprine Prescription: A Cost-Effectiveness Analysis

BACKGROUND

Thiopurine S-methyltransferase (TPMT) testing, either by genotyping or phenotyping, can reduce the incidence of adverse severe myelotoxicity episodes induced by azathioprine. The comparative cost-effectiveness of TPMT genotyping and phenotyping are not known.

OBJECTIVE

Our aim was to assess the cost-effectiveness of phenotyping-based dosing of TPMT activity, genotyping-based screening and no screening (reference) for patients treated with azathioprine.

METHODS

A decision tree was built to compare the conventional weight-based dosing strategy with phenotyping and with genotyping using a micro-simulation model of patients with inflammatory bowel disease from the perspective of the French health care system. The time horizon was set up as 1 year. Only direct medical costs were used. Data used were obtained from previous reports, except for screening test and admission costs, which were from real cases. The main outcome was the cost-effectiveness ratios, with an effectiveness criterion of one averted severe myelotoxicity episode.

RESULTS

The total expected cost of the no screening strategy was €409/patient, the total expected cost of the phenotyping strategy was €427/patient, and the total expected cost of the genotyping strategy was €476/patient. The incremental cost-effectiveness ratio was €2602/severe myelotoxicity averted in using the phenotyping strategy, and €11,244/severe myelotoxicity averted in the genotyping strategy compared to the no screening strategy. At prevalence rates of severe myelotoxicity > 1%, phenotyping dominated genotyping and conventional strategies.

CONCLUSION

The phenotype-based strategy to screen for TPMT deficiency dominates (cheaper and more effective) the genotype-based screening strategy in France. Phenotype-based screening dominates no screening in populations with a prevalence of severe myelosuppression due to azathioprine of > 1%.

Azathioprine Biotransformation in Young Patients with Inflammatory Bowel Disease: Contribution of Glutathione-S Transferase M1 and A1 Variants

The contribution of candidate genetic variants involved in azathioprine biotransformation on azathioprine efficacy and pharmacokinetics in 111 young patients with inflammatory bowel disease was evaluated. Azathioprine doses, metabolites thioguanine-nucleotides (TGN) and methylmercaptopurine-nucleotides (MMPN) and clinical effects were assessed after at least 3 months of therapy. Clinical efficacy was defined as disease activity score below 10. Candidate genetic variants (TPMT rs1142345, rs1800460, rs1800462, GSTA1 rs3957357, GSTM1, and GSTT1 deletion) were determined by polymerase chain reaction (PCR) assays and pyrosequencing. Statistical analysis was performed using linear mixed effects models for the association between the candidate variants and the pharmacological variables (azathioprine doses and metabolites). Azathioprine metabolites were measured in 257 samples (median 2 per patient, inter-quartile range IQR 1-3). Clinical efficacy at the first evaluation available resulted better in ulcerative colitis than in Crohn’s disease patients (88.0% versus 52.5% responders, p = 0.0003, linear mixed effect model, LME). TGN concentration and the ratio TGN/dose at the first evaluation were significantly higher in responder. TPMT rs1142345 variant (4.8% of patients) was associated with increased TGN (LME p = 0.0042), TGN/dose ratio (LME p < 0.0001), decreased azathioprine dose (LME p = 0.0087), and MMPN (LME p = 0.0011). GSTM1 deletion (58.1% of patients) was associated with a 18.5% decrease in TGN/dose ratio (LME p = 0.041) and 30% decrease in clinical efficacy (LME p = 0.0031). GSTA1 variant (12.8% of patients) showed a trend (p = 0.046, LME) for an association with decreased clinical efficacy; however, no significant effect on azathioprine pharmacokinetics could be detected. In conclusion, GSTs variants are associated with azathioprine efficacy and pharmacokinetics.

The Nudix Hydrolase 15 (NUDT15) Gene Variants among Jordanian Arab Population

Background: Nudix Hydrolase 15 gene (NUDT15) encodes nucleotide triphosphate diphosphatase which metabolizes the purine analog drugs, such as anticancer thiopurine and anti-gout allopurinol. Genetic variants on Nudix Hydrolase 15 gene (NUDT15) gene effects the drug’s hydrolyses and hence increases the susceptibility to drug-induced toxicity. The NUDT15 gene has been genotyped in various ethnic groups, however, it has not been genotyped among the Middle Eastern Arab Jordanian population. Aim: The current study aimed to identify NUDT15 genetic variants among Jordanian Arab population. Method: The DNA samples were isolated from leukocytes of 85 unrelated Jordanian Arab volunteers. The coding regions of NUDT15 gene; Exon 1,2 and 3, in addition to some regions of intron 1,2 and 3’UTR, were amplified using polymerase chain reaction (PCR). the PCR products were then subjected to purification and sequenced using Applied Biosystems Model (ABI3730x1). Results: Six NUDT15 genetic variants were found among the volunteers.The results were as followed: A novel synonymous variant 36A>G on exon 1 (6%, 95%CI= 3- 9%), the intronic IVS1 +116C>T variant on intron 1 (0.6%, 95%CI= 0-2%), the non-synonymous variant on exon 3; 415C>T (0.6%, 95%CI= 0-2%), A novel non-synonymous variant on exon 3; 404C>A (0.6%, 95%CI= 0-2%) , and two novel variants on 3’UTR ;502G>A (2%, 95%CI= 0.5-4%) and 588T>C (0.6%, 95%CI= 0-2%). NUDT15 36A>G wasfound to be the most common allele among Jordanians was. In silico softwares predicted that the novel NUDT15 404C>A was harmful and affected NUDT15 enzyme’sstability and function. Furthermore, the frequency of NUDT15 IVS1 +116C>T , among Jordanians, showed to be significantly lower from what was reported in other ethnicities with ap value > 0.05 on the other hand, the frequency of 415C>T variant showed to be similar to Europeans in contrast to Asians and Indians that showed to be significantly lower (p value > 0.05). Conclusions: The frequency of NUDT15 genetic variants is low among the Jordanian volunteers and significantly lower than other ethnic groups. The findings of this study may increase our understanding of the inter-individual variation in the response to purine analog drugs. Further clinical studies are needed to investigate the influence of novel NUDT15 404C>A on drug metabolism and response.

Sperm DNA Integrity is Unaffected by Thiopurine Treatment in Men With Inflammatory Bowel Disease

BACKGROUND AND AIMS

Sperm DNA integrity, concentration, and motility are suspected to be altered by thiopurines (azathioprine [AZA] and 6-mercaptopurine [6-MP]). We investigated the impact of thiopurines on semen quality in men with inflammatory bowel disease [IBD], by a comprehensive panel of semen analyses.

METHODS

Semen from 40 men with IBD, in remission on AZA/6-MP therapy, was prospectively collected and compared with samples from 40 healthy volunteers. Paired samples [off and on AZA/6-MP] were obtained from a subset of IBD patients, and blood and semen were collected to determine 6-MP transmission to the ejaculate. Sperm DNA fragmentation was evaluated via sperm chromatin structure assay [SCSA] and Comet analysis. Conventional World Health Organization [WHO] parameters, i.e. semen volume and sperm concentration, motility, and morphology, were assessed. Additionally, we measured thioguanine nucleotide [TGN] incorporation in sperm cell DNA.

RESULTS

Sperm DNA fragmentation levels did not differ between men with IBD on AZA/6-MP and healthy volunteers when evaluated by SCSA [p = 0.23] and Comet analysis [p = 0.72]. IBD patients on AZA/6-MP had significantly lower total and progressive sperm motility than healthy volunteers [48.5% versus 64.5%, p = 0.0003; 27.4% versus 43.3%, p = 0.0004; respectively], with no differences in concentration, volume, or morphology. The same trend was observed in the 10 paired samples. TGN incorporation was not detectable in sperm DNA, but 6-MP was detected in seminal plasma and correlated to blood levels [rs = 0.79, p = 0.02].

CONCLUSIONS

Thiopurines do not increase sperm DNA fragmentation but may impair sperm motility in this IBD cohort. Our findings support existing epidemiological data that thiopurine therapy is safe during preconception and should not be abandoned.

Pharmacokinetics and Immune Reconstitution Following Discontinuation of Thiopurine Analogues: Implications for Drug Withdrawal Strategies

BACKGROUND AND AIMS

Discontinuation of thiopurine analogues is common prior to live vaccines, during infection or when de-escalating therapy. Data regarding clearance of active metabolites and immune re-constitution is scant. We aimed to determine drug elimination and immune re-constitution following thiopurine cessation.

METHODS

The elimination kinetics of 6-thioguanine nucleotides (6-TGN) were determined in nine inflammatory bowel disease [IBD] patients discontinuing thiopurines. Immune reconstitution was evaluated by toxic shock syndrome toxin 1 [TSST1] or anti-CD3 [OKT3]-induced CD4+ T-cell proliferation, following an initial exposure to TSST1 and 6-mercaptopurine [6MP], separately or combined.

RESULTS

All patients discontinuing thiopurines displayed first-order elimination kinetics of 6-TGN, with a median elimination half-life of 6.8 days [interquartile range 5.9-8.4]. Resting CD4+ T-cells exposed to 6MP preserved their response to subsequent polyclonal or Vβ2+-preferential stimulation. By contrast, exposure of TSST1-activated CD4+ T-cells to 6MP inhibited their subsequent Vβ2+clonal response to further stimulation [p = 0.008], whereas overall response to further non-Vβ2-selective stimulation with OKT3 was unaltered [p = 0.9].

CONCLUSIONS

Upon 6MP/azathioprine discontinuation, a 6-TGN elimination half-life of less than 10 days is expected in most patients. Immune reconstitution, however, may take longer for T-cell clones exposed to stimulation during thiopurine treatment. These findings may be useful when considering thiopurine cessation.

Thiopurine methyltransferase activity in children with acute myeloid leukemia

Activity of the enzyme thiopurine methyltransferase (TPMT) determines the anti-leukemic effect of thiopurines used in the chemotherapy of acute lymphoblastic leukemia (ALL) and acute myeloblastic leukemia (AML). TPMT status and its effects on treatment outcome have been studied extensively in ALL and autoimmune disorders, but few data is available on TPMT in AML. The present study assessed the genetic polymorphisms and activity of TPMT in children with AML at different treatment stages, and compared the results with those obtained for children with ALL. The study included 33 children with AML (0.7-19.7 years) treated with 6-thioguanine (6-TG) according to the AML-BFM 2004 Protocol. Blood samples were collected at diagnosis, during and following maintenance chemotherapy from 8, 10 and 17 patients with AML (the assay was performed at two time points in 2 patients), respectively. Blood samples from 105 children with ALL were obtained at diagnosis, during the maintenance chemotherapy and following the cessation of the chemotherapy from 16, 55 and 34 children, respectively. The activity of TPMT in red blood cells lysates was measured using an enzymatic reaction based on the conversion of 6-mercaptopurine into 6-methylmercaptopurine, involving S-adenozyl-L-methionine as the methyl group donor. TPMT mutations were determined using a polymerase chain reaction/restriction fragment length polymorphism method. Median TPMT activity at diagnosis, during maintenance chemotherapy and following chemotherapy was 43.1, 47,3 and 41.7 nmol 6-mMP g^-1 Hb h^-1, respectively. All patients with AML exhibited the homozygous TPMT*1/*1 genotype, with the exception of 1, who was a heterozygote with the TPMT*1/*3C genotype and demonstrated a TPMT activity level at diagnosis of 42.5 nmol 6-mMP g^-1 Hb h^-1. At each chemotherapy stage, the median TPMT activities in children with AML were significantly increased compared with the median TPMT activities in children with ALL. The preliminary results suggest that the TPMT activity in AML may be increased compared with that in ALL. Comprehensive studies on the association between thiopurine metabolism and treatment outcome in AML are required, with regard to the cytogenetic and molecular factors currently used for AML risk stratification.

Analytical and Sample Preparation Protocol for Therapeutic Drug Monitoring of 12 Thiopurine Metabolites Related to Clinical Treatment of Inflammatory Bowel Disease

Thiopurines (TP) represent an important therapeutic tool for the treatment of inflammatory bowel diseases (IBD) in the current situation of rising incidence and health care costs. The results of multiple clinical studies aimed at finding correlations between levels of TP metabolites and response of IBD patients to the treatment are, however, often controversial due to variability in analytical and sample preparation procedures among these studies. In this work, therefore, an updated analytical and sample preparation procedure for therapeutic drug monitoring (TDM) of TP metabolites in blood samples obtained from patients with IBD was proposed to establish a unified protocol. An advanced analytical method based on ion-exchange liquid chromatography hyphenated with tandem mass spectrometry (IEC-ESI-MS/MS) was used for the determination of the profiles of 12 individual TP metabolites in the particular steps of sample preparation procedure including blood collection, red blood cells (RBC) isolation, lysis, and storage. Favorable performance parameters of the IEC-ESI-MS/MS method (LLOQs 1⁻10 nmol/L, accuracy 95⁻105%, intra-day and inter-day precision < 10%, selectivity demonstrated via no sample matrix interferences) and acceptable stability (peak area fluctuations < 15%) of clinical samples under the proposed sample preparation conditions {(i) EDTA anticoagulant tube for the blood collection; (ii) 4 °C and 4 h between the sample collection and RBC isolation; (iii) phosphate-buffered saline for RBC washing and re-suspendation; (iv) -20 °C for RBC lysis and short-term storage; (v) 50 mmol/L phosphate buffer, pH 7.4, 10 mmol/L DTT as a stabilizing medium for TPN in RBC lysates} demonstrated the suitability of such protocol for a well-defined and reliable routine use in studies on thiopurines TDM.

6-Thioguanine inhibits rotavirus replication through suppression of Rac1 GDP/GTP cycling

Rotavirus infection has emerged as an important cause of complications in organ transplantation recipients and might play a role in the pathogenesis of inflammatory bowel disease (IBD). 6-Thioguanine (6-TG) has been widely used as an immunosuppressive drug for organ recipients and treatment of IBD in the clinic. This study aims to investigate the effects and mode-of-action of 6-TG on rotavirus replication. Human intestinal Caco2 cell line, 3D model of human primary intestinal organoids, laboratory rotavirus strain (SA11) and patient-derived rotavirus isolates were used. We have demonstrated that 6-TG significantly inhibits rotavirus replication in these intestinal epithelium models. Importantly, gene knockdown or knockout of Rac1, the cellular target of 6-TG, significantly inhibited rotavirus replication, indicating the supportive role of Rac1 for rotavirus infection. We have further demonstrated that 6-TG can effectively inhibit the active form of Rac1 (GTP-Rac1), which essentially mediates the anti-rotavirus effect of 6-TG. Consistently, ectopic over-expression of GTP-Rac1 facilitates but an inactive Rac1 (N17) or a specific Rac1 inhibitor (NSC23766) inhibits rotavirus replication. In conclusion, we have identified 6-TG as an effective inhibitor of rotavirus replication via the inhibition of Rac1 activation. Thus, for transplantation patients or IBD patients infected with rotavirus or at risk of rotavirus infection, the choice of 6-TG as a treatment appears rational.

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6-TG inhibits rotavirus infection.

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Rac1, the cellular target of 6-TG, supports rotavirus infection.

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6-TG inhibits the active form of Rac1 (GTP-Rac1) to exert the anti-rotavirus effect.

6-mercaptopurine promotes energetic failure in proliferating T cells

The anticancer drug 6-mercaptopurine (6-MP) inhibits de novo purine synthesis and acts as an antiproliferative agent by interfering with protein, DNA and RNA synthesis and promoting apoptosis. Metabolic reprogramming is crucial for tumor progression to foster cancer cells growth and proliferation, and is regulated by mechanistic target of rapamycin (mTOR) and AMP-activated protein kinase (AMPK) as well as the oncogenes Myc and hypoxia inducible factor 1α (HIF-1α). We hypothesized that 6-MP impacts metabolic remodeling through its action on nucleotide synthesis. The aim of our study is to provide a comprehensive characterization of the metabolic changes induced by 6-MP in leukemic T cells. Our results indicate that exposition to 6-MP rapidly reduces intracellular ATP concentration, leading to the activation of AMPK. In turn, mTOR, an AMPK target, was inhibited, and the expression of HIF-1α and Myc was reduced upon 6-MP incubation. As a consequence of these inhibitions, glucose and glutamine fluxes were strongly decreased. Notably, no difference was observed on glucose uptake upon exposition to 6-MP. In conclusion, our findings provide new insights into how 6-MP profoundly impacts cellular energetic metabolism by reducing ATP production and decreasing glycolytic and glutaminolytic fluxes, and how 6-MP modifies human leukemic T cells metabolism with potential antiproliferative effects.

A Severe Neonatal Lymphopenia Associated With Administration of Azathioprine to the Mother in a Context of Crohn's Disease

Azathioprine is commonly used in Crohn's disease. It has been administered to many pregnant women over many years without significant side effects. However, pancytopenia and severe combined immune deficiency-like disease have been reported in infants whose mothers received azathioprine throughout pregnancy. Moreover, myelotoxicity has been described in patients being treated with azathioprine and having a low or absent thiopurine S-methyl transferase [TPMT] activity.Here, we describe the case of a newborn girl found to be highly lymphopenic [< 300 CD3+ T cells] after a positive newborn screening for severe combined immuno deficiency. The clinical examination was normal. The mother was treated with azathioprine throughout her pregnancy, without any reduction of the dose. It was shown that the mother was heterozygous for the 3A [TPMT] activity mutation and that the baby was homozygous for the same mutation; 6-thioguanine nucleotides were high (744 pmol/8.108 red blood cells [RBC]) in the mother and detectable in the infant [177 pmol/8.108 RBC].Although rare, this case illustrates the potential grave consequences of unsuspected TPMT homozygosity in a newborn of a mother receiving thiopurines during pregnancy. Because of the severity of the risk for the newborn, consideration should be given to performing maternal genetic testing and newborn routine blood count in cases of thiopurine treatment during pregnancy.

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.

Thiopurine metabolite levels in patients with atopic dermatitis and/or chronic hand/foot eczema treated with azathioprine

BACKGROUND

Azathioprine is frequently used in severe eczema. It is converted in the liver into active metabolites, including 6-thioguanine nucleotide (6-TGN) and methylated 6-methylmercaptopurine (6-MMP). In the past, the therapeutic potential of azathioprine may have not been fully utilized. Recent investigations on inflammatory bowel disease have led to a better understanding of azathioprine metabolism and optimizing treatment.

OBJECTIVE

To investigate whether measuring thiopurine metabolites in circulation can improve the effectiveness and safety of azathioprine treatment in patients with atopic dermatitis and/or chronic hand/foot eczema.

METHODS

Azathioprine metabolite levels were measured in eczema patients during maintenance treatment (Part I) and dose escalation (Part II). Clinical effectiveness, hepatotoxicity, and bone marrow suppression were analyzed and TPMT genotype was assessed.

RESULTS

A wide variation in metabolite levels in all dose groups was observed. In Part I (32 patients), there were no significant differences in 6-TGN levels between clinical responders and non-responders (p = .806). No hepatoxicity or myelotoxicity was observed. In Part II, all 6-TGN and 6-MMP levels increased during dose escalation. Hypermethylation was observed in 2/8 patients.

CONCLUSION

For individual eczema patients treated with azathioprine, routinely measuring 6-TGN and 6-MMP can be helpful in optimizing azathioprine dose, improving clinical effectiveness, and preventing side effects.

Determination of thiopurine S-methyltransferase activity by hydrophilic interaction liquid chromatography hyphenated with mass spectrometry

Thiopurine S-methyltransferase (TPMT) plays an important role in the metabolism of thiopurines used in the therapy of inflammatory bowel diseases (IBD). In this work a new progressive method for the determination of TPMT activity in red blood cells lysates was developed. Analysis was carried out by means of hydrophilic interaction liquid chromatography (HILIC) hyphenated with mass spectrometry (MS). In comparison with reversed-phase high-performance liquid chromatography (RP-HPLC), that has been typically applied in determination of TPMT activity, the HILIC significantly improved the analytical signal provided by MS, shortened analysis time, and improved chromatographic resolution. The HILIC-HPLC-MS method was optimized and validated, providing favorable parameters of detection and quantitation limits (5.5 and 16.5pmol/mL, respectively), linearity (coefficient of determination 0.9999 in the range of 0.01-1.0nmol/mL), recovery and precision (93.25-100.37% with RSD 1.06-1.32% in the whole concentration range of QC samples). Moreover, in contrast to the conventional RP-HPLC-UV approach, the complex phenotype TPMT profiles can be reliably and without interferences monitored using the HILIC-HPLC-MS method. Such advanced monitoring can provide valuable detail information on the thiopurines (e.g. evaluating ratio of methylated and non-methylated 6-mercaptopurine) and, by that, TPMT action in biological systems before and during the therapy of IBD.

Pharmacogenetics of inflammatory bowel disease: a focus on Crohn's disease

Crohn's disease is an inflammatory bowel disease showing a high heterogeneity in phenotype and a strong genetic component. The treatment is complex, due to different severity of clinical parameters and to the fact that therapies only permit to control symptoms and to induce remission for short periods. Moreover, all categories of drugs present a great interindividual variability both in terms of efficacy and side effects appearance. For this reason, the identification of specific genomic biomarkers involved in drugs response will be of great clinical utility in order to foresee drug's efficacy and to prevent adverse reactions, permitting a more personalized therapeutic approach. In this review, we focus the attention on the pharmacogenetic studies regarding drugs commonly utilized in Crohn's disease treatment.

Pathomechanisms of Oxidative Stress in Inflammatory Bowel Disease and Potential Antioxidant Therapies

Inflammatory bowel disease (IBD) is a chronic gastrointestinal disease whose incidence has risen worldwide in recent years. Accumulating evidence shows that oxidative stress plays an essential role in the pathogenesis and progression of IBD. This review highlights the generation of reactive oxygen species (ROS) and antioxidant defense mechanisms in the gastrointestinal (GI) tract, the involvement of oxidative stress signaling in the initiation and progression of IBD and its relationships with genetic susceptibility and the mucosal immune response. In addition, potential therapeutic strategies for IBD that target oxidative stress signaling are reviewed and discussed. Though substantial progress has been made in understanding the role of oxidative stress in IBD in humans and experimental animals, the underlying mechanisms are still not well defined. Thus, further studies are needed to validate how oxidative stress signaling is involved in and contributes to the development of IBD.

Thiopurine S-methyltransferase polymorphisms in acute lymphoblastic leukemia, inflammatory bowel disease and autoimmune disorders: influence on treatment response

The thiopurine S-methyltransferase (TPMT) gene encodes for the TPMT enzyme that plays a crucial role in the metabolism of thiopurine drugs. Genetic polymorphisms in this gene can affect the activity of the TPMT enzyme and have been correlated with variability in response to treatment with thiopurines. Advances in the pharmacogenetics of TPMT allowed the development of dosing recommendations and treatment strategies to optimize and individualize prescribing thiopurine in an attempt to enhance treatment efficacy while minimizing toxicity. The influence of genetic polymorphisms in the TPMT gene on clinical outcome has been well-documented and replicated in many studies. In this review, we provide an overview of the evolution, results, conclusions and recommendations of selected studies that investigated the influence of TPMT pharmacogenetics on thiopurine treatment in acute lymphoblastic leukemia, inflammatory bowel disease and autoimmune disorders. We focus mainly on prospective studies that explored the impact of individualized TPMT-based dosing of thiopurines on clinical response. Together, these studies demonstrate the importance of preemptive TPMT genetic screening and subsequent dose adjustment in mitigating the toxicity associated with thiopurine treatment while maintaining treatment efficacy and favorable long-term outcomes. In addition, we briefly address the cost-effectiveness of this pharmacogenetics approach and its impact on clinical practice as well as the importance of recent breakthrough advances in sequencing and genotyping techniques in refining the TPMT genetic screening process.

Xanthine Oxidoreductase in Drug Metabolism: Beyond a Role as a Detoxifying Enzyme

The enzyme xanthine oxidoreductase (XOR) catalyzes the last two steps of purine catabolism in the highest uricotelic primates. XOR is an enzyme with dehydrogenase activity that, in mammals, may be converted into oxidase activity under a variety of pathophysiologic conditions. XOR activity is highly regulated at the transcriptional and post-translational levels and may generate reactive oxygen and nitrogen species, which trigger different consequences, ranging from cytotoxicity to inflammation. The low specificity for substrates allows XOR to metabolize a number of endogenous metabolites and a variety of exogenous compounds, including drugs.

The present review focuses on the role of XOR as a drug-metabolizing enzyme, specifically for drugs with anticancer, antimicrobial, antiviral, immunosuppressive or vasodilator activities, as well as drugs acting on metabolism or inducing XOR expression.

XOR has an activating role that is essential to the pharmacological action of quinone drugs, cyadox, antiviral nucleoside analogues, allopurinol, nitrate and nitrite. XOR activity has a degradation function toward thiopurine nucleotides, pyrazinoic acid, methylxanthines and tolbutamide, whose half-life may be prolonged by the use of XOR inhibitors.

In conclusion, to avoid potential drug interaction risks, such as a toxic excess of drug bioavailability or a loss of drug efficacy, caution is suggested in the use of XOR inhibitors, as in the case of hyperuricemic patients affected by gout or tumor lysis syndrome, when it is necessary to simultaneously administer therapeutic substances that are activated or degraded by the drug-metabolizing activity of XOR.

Pharmacogenetics of immunosuppressants: State of the art and clinical implementation - recommendations from the French National Network of Pharmacogenetics (RNPGx)

Therapeutic drug monitoring is already widely used for immunosuppressive drugs due to their narrow therapeutic index. This article summarizes evidence reported in the literature regarding the pharmacogenetics of (i) immunosuppressive drugs used in transplantation and (ii) azathioprine used in chronic inflammatory bowel disease. The conditions of use of currently available major pharmacogenetic tests are detailed and recommendations are provided based on a scale established by the RNPGx scoring tests as "essential", "advisable" and "potentially useful". Other applications for which the level of evidence is still debated are also discussed.

Metabolite monitoring to guide thiopurine therapy in systemic autoimmune diseases

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

Pharmacology and Optimization of Thiopurines and Methotrexate in Inflammatory Bowel Disease

Improving the efficacy and reducing the toxicity of thiopurines and methotrexate (MTX) have been areas of intense basic and clinical research. An increased knowledge on pharmacodynamics and pharmacokinetics of these immunomodulators has optimized treatment strategies in inflammatory bowel disease (IBD). This review focuses on the metabolism and mode of action of thiopurines and MTX, and provides an updated overview of individualized treatment strategies in which efficacy in IBD can be increased without compromising safety. The patient-based monitoring instruments adapted into clinical practice include pretreatment thiopurine S-methyltransferase testing, thiopurine metabolite monitoring, and blood count measurements that may help guiding the dosage to improve clinical outcome. Other approaches for optimizing thiopurine therapy in IBD include combination therapy with allopurinol, 5-aminosalicylates, and/or biologics. Similar strategies are yet to be proven effective in improving the outcome of MTX therapy. Important challenges for the management of IBD in the future relate to individualized dosing of immunomodulators for maximal efficacy with minimal risk of side effects. As low-cost conventional immunomodulators still remain a mainstay in pharmacotherapy of IBD, more research remains warranted, especially to substantiate these tailored management strategies in controlled clinical trials.

Experts Opinion on the Practical Use of Azathioprine and 6-Mercaptopurine in Inflammatory Bowel Disease

The relevance of azathioprine and 6-mercaptopurine therapy in inflammatory bowel disease, Crohn's disease, and ulcerative colitis, has been challenged in recent publications. In this article, a panel of experts gives advice, based on the relevant literature, on indications and practical use of azathioprine/6-mercaptopurine, prevention, and management of drug adverse reactions and special situations such as vaccination, pregnancy, and lactation.

NUDT15 polymorphisms are better than thiopurine S-methyltransferase as predictor of risk for thiopurine-induced leukopenia in Chinese patients with Crohn's disease

BACKGROUND

Thiopurine-induced leukopenia is the most common dangerous adverse event in Asians. NUDT15 R139C was recently proposed to be a promising biomarker for leukopenia with thiopurine therapy in Asians, but this has not been replicated in the Chinese population.

AIM

To investigate the influence of NUDT15 R139C, thiopurine S-methyltransferase (TPMT), 6-TGN and 6-MMPR on thiopurine-induced leukopenia in Chinese patients with Crohn's disease.

METHODS

Clinical and epidemiological characteristics were reviewed from medical records. NUDT15 R139C and TPMT were genotyped. 6-TGN/6-MMPR concentrations were measured with high-performance liquid chromatography (HPLC).

RESULTS

A total of 253 patients were included, 65 (25.7%) of whom experienced leukopenia. The median follow-up with thiopurine treatment was 38.0 weeks (range, 1-192 weeks). NUDT15 R139C was strongly associated with the incidence of leukopenia (70.2% mutation vs. 12.8% wild type; P=8.61×10^-19 ; odds ratio, 10.80; 95% CI, 5.89-19.83). However, TPMT genotype was not found to be correlated with the incidence of leukopenia (P = 0.44). In subgroup of NUDT15 wild type, there was significant difference of 6TGN concentration between patients with and without leukopenia (413.0 (174.2-831.4) vs. 279.7 (77.3-666.9) pmol/8 × 10⁸ RBC, P = 0.0055). In contrast, no association was found in patients with NUDT15 R139C variant alleles (P = 0.26). 6-MMPR was not correlated with leukopenia (P = 0.84).

CONCLUSIONS

In Chinese patients, it is strongly recommended to detect NUDT15 genotype rather than TPMT before initiating thiopurine drugs. 6TGN concentration should be routinely monitored in CD patients with NUDT15 wild type. As for CT genotype, starting at low dose and careful monitoring for leukopenia and 6TGN levels is recommended.

Hepatosplenic T-cell lymphoma arising in patients with immunodysregulatory disorders: a study of 7 patients who did not receive tumor necrosis factor-α inhibitor therapy and literature review

Hepatosplenic T-cell lymphoma (HSTCL) is a rare and aggressive extranodal T-cell lymphoma that can arise in patients with underlying immune disorders. Others have suggested that tumor necrosis factor (TNF)-α inhibitor therapy for immune disorders increases the risk of HSTCL. To assess for a potential relationship between HSTCL and the use of TNF-α inhibitors, we searched for patients with HSTCL and underlying immune disorders at our institution. We identified 7 patients with a median age of 38 years. Five patients had Crohn disease, 1 ulcerative colitis, and 1 rheumatoid arthritis. In 6 patients, medication history for the immune disorder was available: 6 patients received 6-mercaptopurine or azathioprine, and 2 patients received steroids; no patients received TNF-α inhibitors. In all 7 patients, the histologic, immunophenotypic, and cytogenetic findings were similar to cases of HSTCL that arise in immunocompetent patients. We reviewed the literature and identified 60 patients with immune disorders who subsequently developed HSTCL. These patients were treated with immunosuppressive drugs in 89%, TNF-α inhibitors in 56%, and both therapies in 54%, and 1 (2%) patient was treated with TNF-α inhibitors only. Our cohort and literature review indicates that TNF-α inhibitor therapy is not essential for the development of HSTCL in patients with immunodysregulatory disorders, and implies that immunosuppressive drugs or other factors (eg, genetic predisposition, chronic antigenic stimulation) may be more critical in the pathogenesis in this context. Although these data are observational, they have implications for the use of TNF-α inhibitors in patients with inflammatory bowel disease and other immunodysregulatory disorders.

Genetic variation in IBD: progress, clues to pathogenesis and possible clinical utility

Epidemiological and clinical studies have suggested that the pathogenesis of inflammatory bowel disease (IBD) is strongly influenced by genetic predisposition. Beyond the limitations of linkage analysis, multiple genome-wide association studies, their meta-analyses, and targeted genotyping array techniques have broadened our understanding of the genetic architecture of IBD. Currently, over 200 single nucleotide polymorphisms are known to be associated with susceptibility to IBD and through functional analysis of genes and loci, a substantial proportion of pathophysiologic mechanisms have been revealed. However, because only a modest fraction of predicted heritability can be explained by known genes/loci, additional strategies are needed including the identification of rare variants with large effect sizes to help explain the missing heritability. Considerable progress is also being made on applying outcomes of genetic research in diagnostics, classification, prognostics, and the development of new therapeutics of IBD.

The Role of Laboratory Tests in Crohn's Disease

In the past, laboratory tests were considered of limited value in Crohn's disease (CD). In the era of biologics, laboratory tests have become essential to evaluate the inflammatory burden of the disease (C-reactive protein, fecal calprotectin) since symptoms-based scores are subjective, to predict the response to pharmacological options and the risk of relapse, to discriminate CD from ulcerative colitis, to select candidates to anti-tumor necrosis factors [screening tests looking for hepatitis B virus and hepatitis C virus status and latent tuberculosis], to assess the risk of adverse events (testing for thiopurine metabolites and thiopurine-methyltransferase activity), and to personalize and optimize therapy (therapeutic drug monitoring). Pharmacogenetics, though presently confined to the assessment of thiopurineme methyltransferase polymorphisms and hematological toxicity associated with thiopurine treatment, is a promising field that will contribute to a better understanding of the molecular mechanisms of the variability in response to the drugs used in CD with the attempt to expand personalized care and precision medicine strategies.

Review article: acute severe ulcerative colitis - evidence-based consensus statements

BACKGROUND

Acute severe ulcerative colitis (ASUC) is a potentially life-threatening complication of ulcerative colitis.

AIM

To develop consensus statements based on a systematic review of the literature of the management of ASUC to improve patient outcome.

METHODS

Following a literature review, the Delphi method was used to develop the consensus statements. A steering committee, based in Australia, generated the statements of interest. Three rounds of anonymous voting were carried out to achieve the final results. Acceptance of statements was pre-determined by ≥80% votes in 'complete agreement' or 'agreement with minor reservation'.

RESULTS

Key recommendations include that patients with ASUC should be: hospitalised, undergo unprepared flexible sigmoidoscopy to assess severity and to exclude cytomegalovirus colitis, and be provided with venous thromboembolism prophylaxis and intravenous hydrocortisone 100 mg three or four times daily with close monitoring by a multidisciplinary team. Rescue therapy such as infliximab or ciclosporin should be started if insufficient response by day 3, and colectomy considered if no response to 7 days of rescue therapy or earlier if deterioration. With such an approach, it is expected that colectomy rate during admission will be below 30% and mortality less than 1% in specialist centres.

CONCLUSION

These evidenced-based consensus statements on acute severe ulcerative colitis, developed by a multidisciplinary group, provide up-to-date best practice recommendations that improve and harmonise management as well as provide auditable quality assessments.