BACKGROUND: Thiopurine co-therapy with anti-tumour necrosis factor-alpha (anti-TNFα) agents is associated with higher anti-TNFα drug levels and reduced immunogenicity in inflammatory bowel disease (IBD).
OBJECTIVE: We aimed to evaluate the association between 6-thioguanine nucleotide (6-TGN) and anti-TNFα levels and the optimal 6-TGN threshold level associated with higher anti-TNFα levels in combination therapy.
METHODS: We performed a retrospective cross-sectional multicentre study of patients with IBD on combination anti-TNFα and thiopurine maintenance therapy between January 2015 and August 2021. Primary outcomes were infliximab and adalimumab levels. Secondary outcomes were antibodies to infliximab (ATI) or adalimumab (ATA). Univariable and multivariable linear regression were performed to identify variables associated with anti-TNFα levels. Receiver operator characteristic curves were used to define the optimal 6-TGN cut-off levels associated with therapeutic anti-TNFα levels.
RESULTS: The study included 743 paired 6-TGN and anti-TNFα levels (640 infliximab and 103 adalimumab). 6-TGN levels were associated with infliximab levels, but not adalimumab levels, on univariable and multivariable regression. The optimal 6-TGN cut-off associated with therapeutic infliximab levels (≥5 mcg/mL) was 261 pmol/8 × 108 red blood cell (RBC) (area under the curve (AUC) = 0.57) for standard infliximab dosing and 227.5 pmol/8 × 108 RBC (AUC = 0.58) for escalated dosing. For therapeutic adalimumab levels (≥7.5 mcg/mL), the 6-TGN cut-off was 218.5 pmol/8 × 108 RBC (AUC = 0.59) for standard adalimumab dosing and 237.5 pmol/8 × 108 RBC (AUC = 0.63) for escalated dosing.
CONCLUSIONS: 6-TGN levels were weakly associated with infliximab but not adalimumab levels in combination therapy. 6-TGN levels in the lower end of the therapeutic range (230-260 pmol/8 × 108 RBC) may be adequate to maintain higher infliximab levels, particularly with escalated infliximab dosing.

The management of inflammatory bowel diseases (IBD) requires weighing an individual patient\'s therapeutic benefits and therapy-related complication risks. The immunomodulators that have been commonly used so far in IBD therapy are thiopurines, including 6-mercaptopurine and azathioprine. As our understanding of the IBD pathomechanisms is widening, new therapeutic approaches are being introduced, including the Janus kinase (JAK) inhibitors and Sphingosine 1-phosphate receptor (S1PR) modulators\' development. Non-selective JAK inhibitors are represented by tofacitinib, while selective JAK inhibitors comprise filgotinib and upadacitinib. As for the S1PR modulators, ozanimod and etrasimod are approved for UC therapy. The number of elderly patients with IBD is growing; therefore, this review aimed to evaluate the effectiveness and safety of the oral immunomodulators among the subjects aged ≥60. Possible complications limit the use of thiopurines in senior patients. Likewise, the promising effectiveness of new drugs in IBD therapy in those with additional risk factors might be confined by the risk of serious adverse events. However, the data regarding this issue are limited.

OBJECTIVE: Conventional thiopurines (azathioprine and mercaptopurine) remain standard therapy to maintain steroid sparing remission in inflammatory bowel disease (IBD), but are regularly discontinued due to adverse drug reactions (ADRs). Measurement of the metabolites 6-thioguanine nucleotides (6-TGN), 6-methylmercaptopurine ribonucleotides (6-MMPR) and the 6-MMPR/6-TGN ratio, may predict the development of these ADRs. Our aim was to evaluate whether early thiopurine metabolite measurements were associated with clinical outcomes.
METHODS: A post-hoc analysis was conducted of a multicentre, prospective, observational study on thiopurine-induced hepatotoxicity. IBD patients who initiated thiopurine therapy were included and thiopurine metabolite concentrations were assessed after 7 days (±1) (T1). Patients were monitored for 12 weeks to document the occurrence of ADRs, early treatment discontinuation and effectiveness.
RESULTS: In total, 181 patients were evaluated. At T1, 6-MMPR concentrations and 6-TGN/6-MMPR ratios were independently related to treatment discontinuation within 12 weeks after correction for sex, age and body mass index (BMI) (P = .034 and .002, respectively). The largest effects were observed for 6-MMPR ≥3000 pmol/8 × 108 RBC and 6-TGN/6-MMPR ratio ≥17. Furthermore, 6-MMPR concentrations and 6-TGN/6-MMPR ratios at T1 were independently related to skewed metabolism at steady state (Week 8, 6-MMPR/-6TGN ratio ≥11 and ≥20) (both P < .001). The occurrence of ADRs and effectiveness were not independently related to T1 thiopurine metabolite concentrations.
CONCLUSIONS: Thiopurine metabolite concentrations at T1 were related to early treatment discontinuation and skewed metabolism at steady state, but not to effectiveness, helping to identify patients with a high risk of thiopurine treatment failure.

UNASSIGNED: The clinical consequences for patients with inflammatory bowel disease (IBD) who stop treatment owing to side effects have not been fully investigated.
UNASSIGNED: This retrospective observational study aimed to compare patients who discontinued thiopurine treatment due to side effects with those who tolerated thiopurine treatment in the use of other IBD drugs, surgery, and fecal calprotectin values in the first 5 years after the start of thiopurine treatment.
UNASSIGNED: The proportion of patients with IBD who initiated thiopurine treatment at our clinic was 44% (32% ulcerative colitis and 64% Crohn\'s disease) and 31% (n = 94) of those patients had to stop thiopurine treatment within 5 years due to side effects. Patients who discontinued thiopurine treatment due to intolerance were significantly older (median age 33 vs. 27 years, p = 0.003), significantly more often used prednisolone (89 vs. 76%, p = 0.009), and used to a lesser extent TNF inhibitors at the start of thiopurine treatment (3% vs. 9%, p = 0.062). Budesonide treatment and non-TNF inhibitor second-line therapy were significantly more commonly used in patients who discontinued thiopurine treatment owing to side effects, but there were no statistically significant differences in the use of other treatments. The proportion of patients with a median FC >200 μg/g was significantly higher during follow-up in patients with UC who discontinued thiopurine treatment owing to side effects.
UNASSIGNED: Patients who discontinued thiopurines owing to side effects were prescribed more budesonide and non-TNF inhibitor second-line therapy, but there were no differences in the use of TNF inhibitors, prednisolone, or surgery.

BACKGROUND: Thiopurine drugs are effective treatment options in inflammatory bowel disease and other conditions but discontinued in some patients due to toxicity.
METHODS: We investigated thiopurine-induced toxicity in a pediatric inflammatory bowel disease cohort by utilizing exome sequencing data across a panel of 46 genes, including TPMT and NUDT15.
RESULTS: The cohort included 487 patients with a median age of 13.1 years. Of the 396 patients exposed to thiopurines, myelosuppression was observed in 11%, gastroenterological intolerance in 11%, hepatotoxicity in 4.5%, pancreatitis in 1.8%, and \"other\" adverse effects in 2.8%. TPMT (thiopurine S-methyltransferase) enzyme activity was normal in 87.4%, intermediate 12.3%, and deficient in 0.2%; 26% of patients with intermediate activity developed toxicity to thiopurines. Routinely genotyped TPMT alleles associated with defective enzyme activity were identified in 28 (7%) patients: TPMT*3A in 4.5%, *3B in 1%, and *3C in 1.5%. Of these, only 6 (21%) patients developed toxic responses. Three rare TPMT alleles (*3D, *39, and *40) not assessed on routine genotyping were identified in 3 patients, who all developed toxic responses. The missense variant p.R139C (NUDT15*3 allele) was identified in 4 patients (azathioprine 1.6 mg/kg/d), but only 1 developed toxicity. One patient with an in-frame deletion variant p.G13del in NUDT15 developed myelosuppression at low doses. Per-gene deleteriousness score GenePy identified a significant association for toxicity in the AOX1 and DHFR genes.
CONCLUSIONS: A significant association for toxicity was observed in the AOX1 and DHFR genes in individuals negative for the TPMT and NUDT15 variants. Patients harboring the NUDT15*3 allele, which is associated with myelosuppression, did not show an increased risk of toxicity.
This study reports thiopurine-induced toxicity in pediatric patients with inflammatory bowel disease. The findings are presented in the context of genetic variations, focusing on genes implicated in thiopurine drug metabolism, thereby contributing to the missing pharmacogenomic association in patients developing toxicity.

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Aim: Non-melanoma skin cancers are more common in people with inflammatory bowel disease. However, these tumors can rarely mimic a cutaneous manifestation of the disease, which delays diagnosis and clouds prognosis. Observation: A 35-year-old man with stenosing and fistulizing ileocolic Crohn\'s disease developed squamous cell carcinoma mimicking a groin fold abscess. After surgical drainage of the abscess, despite antibiotics and therapy combining azathioprine with infliximab, the abscess has recurred. Biopsies revealed a cutaneous squamous cell carcinoma. Palliative radiotherapy-chemotherapy was initiated, but the patient died after 3 months. Conclusion: This observation illustrates the increased risk of non-melanoma skin cancers in inflammatory bowel disease patients, particularly those exposed to thiopurines, and the value of diagnosing them at an early stage.

BACKGROUND: Patients with inflammatory bowel disease (IBD) exhibit considerable interindividual variability in medication response, highlighting the need for precision medicine approaches to optimize and tailor treatment. Pharmacogenetics (PGx) offers the ability to individualize dosing by examining genetic factors underlying the metabolism of medications such as thiopurines. Pharmacogenetic testing can identify individuals who may be at risk for thiopurine dose-dependent adverse reactions including myelosuppression. We aimed to evaluate PGx variation in genes supported by clinical guidelines that inform dosing of thiopurines and characterize differences in the distribution of actionable PGx variation among diverse ancestral groups.
METHODS: Pharmacogenetic variation in TPMT and NUDT15 was captured by genome-wide genotyping of 1083 pediatric IBD patients from a diverse Canadian cohort. Genetic ancestry was inferred using principal component analysis. The proportion of PGx variation and associated metabolizer status phenotypes was compared across 5 genetic ancestral groups within the cohort (Admixed American, African, East Asian, European, and South Asian) and to prior global estimates from corresponding populations.
RESULTS: Collectively, 11% of the cohort was categorized as intermediate or poor metabolizers of thiopurines, which would warrant a significant dose reduction or selection of alternate therapy. Clinically actionable variation in TPMT was more prevalent in participants of European and Admixed American/Latino ancestry (8.7% and 7.5%, respectively), whereas variation in NUDT15 was more prevalent in participants of East Asian and Admixed American/Latino ancestry (16% and 15% respectively).
CONCLUSIONS: These findings demonstrate the considerable interpopulation variability in PGx variation underlying thiopurine metabolism, which should be factored into testing diverse patient populations.
In a large, pediatric inflammatory bowel disease cohort comprised of 5 genetic ancestry groups, we evaluated the distribution of loss-of-function pharmacogenetic variants in TPMT and NUDT15 and predicted phenotypes (impact on thiopurine metabolism).

UNASSIGNED: Parents and pediatric patients with ulcerative colitis (UC) who progressed to systemic immunotherapy are concerned about lifelong risks from such treatments. There is limited knowledge about withdrawal of such agents and step-down (SD) to enteral 5-aminosalicylic acid (mesalamine) before transitioning to adult care.
UNASSIGNED: We studied nine pediatric cases with moderate to severe UC who after a median of 2.18 years of clinical remission on systemic immunotherapy stepped down to oral mesalamine treatment.
UNASSIGNED: Average follow-up time from SD was 3.49 years. Five patients (55.5%) had sustained remission (without any flare noted) after SD during follow-up. Sustained clinical remission was 88.9% (8/9) at 1 year, 87.5% (7/8) at 2 years, and 66.7% (4/6) at 3 years after SD. Out of those tested (one patient was not tested), 62.5% (5/8) had fecal calprotectin <50 μg/g. Four out of six patients examined (66.6%) had mucosal healing on post-SD colonoscopy.
UNASSIGNED: We propose that SD to mesalamine can be a reasonable therapeutic consideration for pediatric patients with UC before transitioning to adult gastroenterology care. Shared decision-making is important before such treatment changes.

METHODS: The purpose of this American Gastroenterological Association (AGA) Institute Clinical Practice Update (CPU) Commentary is to discuss the risks of various malignancies in patients with inflammatory bowel diseases (IBD) and the impact of the available medical therapies on these risks. The CPU will also guide the approach to the patient with IBD who develops a malignancy or the patient with a history of cancer in terms of IBD medication management.
METHODS: This CPU was commissioned and approved by the AGA Institute CPU committee and the AGA Governing Board to provide timely guidance on a topic of high clinical importance to the AGA membership and underwent internal peer review by the CPU committee and external peer review through standard procedures of Clinical Gastroenterology and Hepatology. This communication incorporates important and recently published studies in the field, and it reflects the experiences of the authors who are experts in the diagnosis and management of IBD.