Thiopurines and the Risk of Cancer in Patients with Inflammatory Bowel Disease and Reference Individuals without Inflammatory Bowel Disease - A Danish Nationwide Cohort Study (1996-2018).

BACKGROUND AND AIMS: Thiopurine therapy is a cornerstone in the treatment of inflammatory bowel disease (IBD). We aimed to assess the effect of thiopurines on cancer risk in IBD according to drug exposure and age. METHODS: Danish national registers were used to identify incident IBD patients, exposure to drugs and status of cancers, in 1996-2018. Cox regressions were used to compare cancer risks in IBD and non-IBD individuals and to assess IBD patients' cumulative drug exposure and the association to first cancer, excluding non-melanoma skin cancer. RESULTS: We followed 43,419 IBD patients for a median of 8.2 years (IQR:3.7-14.2) after IBD diagnosis. Cancer was reported in 3,128 (7.2%) IBD patients. The risk of cancer was increased in IBD patients in all age categories compared to non-IBD individuals (<50 years (aHR: 1.59 (95%CI: 1.43-1.77)), 50-65 years (aHR: 1.31 (95%CI: (1.19-1.44)), and >65 years (aHR: 1.14 (95%CI: 1.05-1.24)). Monotherapy and combination therapy were associated with cancer (aHR:1.36 (95%CI:1.17-1.57) and (aHR:2.49 (95%CI:1.64-3.78), respectively) compared to unexposed IBD patients. Among elderly (>65 years), the aHR was 2.79 (95%CI:1.24-6.28) in those receiving combination therapy. In patients discontinuing thiopurines, aHRs returned to the level of unexposed (aHR:0.89 (95%CI:0.78-1.01)). The aHR was positively associated with cumulative thiopurine exposure and in patients with >5 years of exposure, reaching aHR 1.36 (95%CI:1.15-1.61). CONCLUSIONS: Thiopurines were associated with increased hazard of cancer, especially when used in combination therapy in the elderly. The hazard increased by 36% when patients were exposed to thiopurines for more than five years. Reassuringly, the hazard returned to baseline after discontinuation of thiopurines.

Comparative Efficacy and Safety of Upadacitinib vs. Vedolizumab, Ustekinumab, and Tofacitinib After Induction and Maintenance for Ulcerative Colitis: Three Matching-Adjusted Indirect Comparisons.

INTRODUCTION: Evidence on the comparative efficacy and safety of approved therapies for ulcerative colitis (UC) during induction and maintenance, including upadacitinib (UPA), vedolizumab (VEDO), ustekinumab (UST), and tofacitinib (TOFA), is limited. METHODS: Using data from phase 3 trials, three placebo (PBO)-anchored matching-adjusted indirect comparisons of the efficacy and safety of UPA versus VEDO, UST, and TOFA (U-ACHIEVE and U-ACCOMPLISH, GEMINI-1, UNIFI, and OCTAVE induction and maintenance trials) have been conducted. Baseline characteristics from UPA trials were weighted separately to match each comparator trial. Induction responders were re-randomized to oral UPA 15 or 30 mg, VEDO 300 mg intravenously every 8 weeks (Q8W), UST 90 mg SC Q8W, or oral TOFA 5 mg, or PBO in maintenance. Treat-through efficacy outcomes at weeks 44(UST)/46(VEDO)/52(UPA/TOFA) were adjusted by the likelihood of induction response and included clinical response, clinical remission, and endoscopic improvement. Safety outcomes included adverse events (AEs), serious AEs (SAEs), and AEs leading to discontinuation (except UPA vs. VEDO). Benefit-risk was assessed by numbers needed to treat (NNT)/harm, calculated as the inverse of the difference in proportions of patients achieving each efficacy/safety outcome for UPA versus comparator. RESULTS: The proportions of patients who demonstrated clinical response or endoscopic improvement was greater with UPA 15 mg versus VEDO and TOFA (p < 0.05). The proportions of patients demonstrating all treat-through efficacy outcomes were significantly greater with UPA 30 mg versus VEDO, UST, or TOFA with NNTs 3.2-8.7. No significant differences in proportions of AEs, SAEs, and AEs leading to discontinuation were observed between the two doses of UPA and comparators. CONCLUSION: In patients with active UC, greater clinical efficacy, and similar safety after 1 year of maintenance were observed with UPA versus VEDO, UST, and TOFA, suggesting a favorable benefit-risk profile for UPA. Despite matched baseline characteristics, differences in trial design and endpoints may persist.

Spine and sacroiliac joint involvement in newly diagnosed inflammatory bowel disease patients - clinical and magnetic resonance imaging findings from a population-based cohort.

BACKGROUND: In IBD patients, co-occurring spondyloarthritis (SpA) leads to poorer outcomes and impaired quality of life, highlighting the importance of early detection and effective treatment. This is the first study to assess the prevalence and distribution of axial symptoms and MRI-detected involvement of the spine and sacroiliac joints (SIJs) in early IBD. METHODS: Newly diagnosed IBD patients from a prospective, population-based cohort were consecutively recruited. Rheumatological interview, clinical, ultrasound and MRI assessment for SIJ and spine inflammatory and structural lesions were made using validated scoring methods and consensus definitions of axial (ax)SpA. RESULTS: Of 110 patients (ulcerative colitis: 70, Crohn's disease: 40, mean age 42 years, 40% male), 48 (44.9%) reported back and/or buttock pain and 10 (9.1%) had inflammatory back pain. Seventeen (16.7%) patients had MRI findings indicative of axSpA; only 10 of these patients had axial symptoms. Inflammatory MRI lesions were present in SIJs and the spine of 27 (26.5%) and 30 (30.3%) patients, respectively. The ASAS classification criteria for axSpA were met in 11 (10%) cases. MRI findings typical of axSpA were associated with peripheral joint and entheseal inflammation detected by ultrasound (p=0.04). No differences in clinical or imaging findings were found between UC and CD patients. CONCLUSION: One-in-six newly diagnosed IBD patients had MRI findings indicative of axSpA. As 40% of these patients were asymptomatic, this suggests that axSpA is underdiagnosed in early IBD. Multidisciplinary collaboration is essential to ensure early detection of axial inflammation and to enable optimal therapy preventing future structural damage and disability.

Development of an algorithm combining blood-based biomarkers, fecal immunochemical test, and age for population-based colorectal cancer screening.

BACKGROUND AND AIMS: Implementation of screening modalities have reduced the burden of colorectal cancer (CRC), but high false positive rates pose a major problem for colonoscopy capacity. We aimed to create a tailored screening algorithm that expands the fecal immunochemical test (FIT) with a blood specimen and current age to improve selection of individuals for diagnostic colonoscopy. METHODS: In this prospective multi-center study, eight blood-based biomarkers (CEA, Ferritin, hsCRP, HE4, Cyfra21-1, Hepsin, IL-8 and OPG) were investigated in 1,977 FIT positive individuals from the Danish national CRC screening program undergoing follow-up colonoscopy. Specimens were analyzed on ARCHITECT i2000®, ARCHITECT c8000® or Luminex xMAP® machines. FIT analyses and blood-based biomarker data were combined with clinical data (i.e., age and colonoscopy findings) in a cross-validated logistic regression model (algorithm) benchmarked against a model solely using the FIT result (FIT model) applying different cutoffs for FIT positivity. RESULTS: The cohort included individuals with CRC (n = 240), adenomas (n = 938) or no neoplastic lesions (n = 799). The cross-validated algorithm combining the eight biomarkers, quantitative FIT result and age performed superior to the FIT model in discriminating CRC versus non-CRC individuals (AUC 0.77 versus 0.67, p < 0.001). When discriminating individuals with either CRC or high- or medium-risk adenomas versus low-risk adenomas or clean colorectum, the AUCs were 0.68 versus 0.64 for the algorithm and FIT model, respectively. CONCLUSIONS: The algorithm presented here can improve patient allocation to colonoscopy, reducing colonoscopy burden without compromising cancer and adenomas detection rates or vice versa.

Network meta-analysis: Comparative onset of early effect of biologics and small molecules in moderately to severely active luminal Crohn's disease.

INTRODUCTION: Rapidity of effect of advanced therapies for patients with Crohn's disease (CD) can be an essential decision parameter; however, comparative evaluation is lacking. We aimed to compare early response for advanced CD therapies in a network meta-analysis (NMA). METHODS: We searched systematically MEDLINE, Embase, and CENTRAL up to 19 February 2024, for randomised controlled trials. The co-primary outcomes were induction of clinical remission (Crohn's Disease Activity Index (CDAI) ≤150) and clinical response (≥100-point reduction in CDAI) within the first 6 weeks of treatment. We incorporated any assessment within this time point in a Bayesian random-effects NMA following PRISMA-NMA guidance (PROSPERO ID: CRD42022368509). RESULTS: Twenty-five studies, comprising 7414 patients, were included. Infliximab combined with azathioprine or monotherapy ranked highest for induction of clinical remission within 6 weeks and was significantly superior to certolizumab, ustekinumab, guselkumab, vedolizumab, and upadacitinib. However, superiority over risankizumab 600 mg and adalimumab 160/80 mg was non-significant. Accordingly, infliximab in combination with azathioprine and guselkumab 600 mg ranked highest in the corresponding analysis of clinical response with no statistical significance demonstrated. Among bio-exposed patients, none of whom received infliximab, upadacitinib, and risankizumab induced the highest clinical responses. On the other hand, vedolizumab, certolizumab, and ustekinumab ranked lowest across the analyses. CONCLUSIONS: We found infliximab to be ranked highest and superior to all other agents but risankizumab and adalimumab, demonstrating the highest probability of early induction of remission. Upadacitinib and risankizumab induced the highest clinical responses in bio-exposed patients. However, infliximab was not investigated in this population.

Early intestinal ultrasound in severe ulcerative colitis identifies patients at increased risk of 1-year treatment failure and colectomy.

BACKGROUND AND AIMS: Reliable and easily accessible objective markers of disease activity to predict long-term treatment outcomes in severe ulcerative colitis (UC) are missing. We aimed to investigate if intestinal ultrasound (IUS) might predict long-term outcomes in hospitalized patients with severe UC treated with intravenous corticosteroids. METHODS: Hospitalized patients with severe UC and IUS inflammation (bowel wall thickness (BWT)>3.0mm) starting IV corticosteroids were recruited at three university hospitals in Denmark. IUS was performed before treatment, 48±24 hours (h), 6±1 days, and 3 months after treatment initiation. Time until colectomy or need for new interventions was registered together with Mayo score at 3 months and partial Mayo score (pMayo) at 12-months. Follow-up time was 12 months. RESULTS: Fifty-six patients were included in the final analysis. Forty-five (80%) patients needed intervention, including 9 colectomies, during the 12-month follow-up. After 48±24h: No patient with a BWT<3mm needed a colectomy, p=0.04. BWT≥4mm showed an increased risk of colectomy (odds ratio 9.5 (95%CI 1.5-186), p=0.03), while a BWT≥3mm showed an increased risk of intervention (3.6 (1.1-12.5), p=0.03). A BWT≥4mm resulted in a significantly shorter time until both colectomy, p=0.03, and treatment intensification (mean days 75 (95%CI24-127) vs. 176 (119-233), p=0.005. However, neither IUS parameters nor pMayo score, CRP, hemoglobin, or p-albumin could predict remission at 3- and 12-months. CONCLUSION: BWT assessed at 48h post intravenous corticosteroid initiation in patients hospitalized with severe UC may identify patients with an increased risk of short- and long-term colectomy and predict a more aggressive short-term disease course.

Probiotic Treatment of Ulcerative Colitis with Trichuris suis ova: A Randomized, Double-blinded, Placebo-controlled Clinical Trial (the PROCTO Trial).

BACKGROUND AND AIMS: To demonstrate that administration of 7500 Trichuris suis ova every second week over 24 weeks would reduce the intestinal inflammation in moderate ulcerative colitis. METHODS: A single-centre, randomized, double-blinded, placebo-controlled, phase 2b clinical trial of 7500 Trichuris suis ova every two weeks for 24 weeks compared to placebo in moderate activity of ulcerative colitis (Mayo score 6-10) were performed. Primary outcome: Clinical remission. Secondary outcomes: Clinical response at 24 weeks, complete corticosteroid-free clinical remission, endoscopic remission, symptomatic remission at 12 and 24 weeks and partial Mayo score over time. RESULTS: 119 patients were randomized to Trichuris suis ova (n=60) and placebo (n=59). At week 24, clinical remission was achieved in 30% of Trichuris suis ova-treated vs. 34% of placebo-treated (RR=0.89; CI:0.52-1.50; p=0.80, ITT). No difference was found in clinical response in any of the clinical response subgroups. However, in patients who did not need treatment with corticosteroids during the trial, a temporary effect of TSO was seen in the analysis of symptomatic remission of week 12 (p=0.01), and the partial Mayo score at week 14 and week 18 (p<0.05 and p=0.02). CONCLUSIONS: Compared to placebo, Trichuris suis ova was not superior in achieving clinical remission at week 24 in ulcerative colitis or in achieving clinical Mayo score reduction, complete corticosteroid-free clinical remission or endoscopic remission. However, Trichuris suis ova treatment induced symptomatic temporary remission at week 12.

Re-resection Rates and Disease Recurrence in Crohn's Disease - A Population-Based Study Using Individual-Level Patient Data.

BACKGROUND AND AIMS: Despite advances in the medical treatment of Crohn's disease (CD), many patients will still need bowel resections and face the subsequent risk of recurrence and re-resection. We describe contemporary re-resection rates and identify disease-modifying factors and risk factors for re-resection. METHODS: We conducted a retrospective, population-based, individual patient data cohort study covering 47.4% of the Danish population, including all CD patients who underwent a primary resection between 2010 and 2020. RESULTS: Among 631 primary resected patients, 24.5% underwent a second resection, and 5.3% a third. Re-resection rates after one, five, and 10 years were 12.6%, 22.4%, and 32.2%, respectively. Reasons for additional resections were mainly disease activity (57%) and stoma reversal (40%). Disease activity-driven re-resection rates after one, five, and 10 years were 3.6%, 10.1%, and 14.1%, respectively. Most stoma reversals occurred within one year (80%). The median time to recurrence was 11.0 months. Biologics started within one year of the first resection revealed protective effect against re-resection for stenotic and penetrating phenotypes. Prophylactic biologic therapy at primary ileocecal resection reduced disease recurrence and re-resection risk (HR 0.58, 95% CI (0.34-0.99), p=0.047). Risk factors for re-resection were location of resected bowel segments at the primary resection, disease location, disease behavior, smoking, and perianal disease. CONCLUSION: Re-resection rates, categorized by disease activity, are lower than those reported in other studies and are closely associated with disease phenotype and localization. Biological therapy may be disease-modifying for certain subgroups when initiated within one year of resection.

Effects of prednisolone tapering on effectiveness of infliximab in patients with ulcerative colitis: data from a retrospective cohort.

BACKGROUND AND OBJECTIVE: The influence of concomitant prednisolone on clinical outcomes and safety in infliximab-treated ulcerative colitis (UC) patients is unknown. DESIGN, SETTING, PARTICIPANTS AND OUTCOME MEASURES: A retrospective cohort study was performed, including 147 UC patients treated with infliximab at a tertiary inflammatory bowel disease (IBD) centre. Primary outcome was corticosteroid-free clinical remission (CFCR) at week 14 and week 52. Patients were grouped according to prednisolone tapering regimens: standard (≤5 mg/week), fast (>5 mg/week), direct discontinuation or no prednisolone. Patients intolerant to corticosteroids and patients stopping corticosteroids in preparation for surgery including colectomy during their initial admission were excluded. RESULTS: There was no overall association between prednisolone exposure or no exposure and CFCR at weeks 14 or 52 of infliximab. The proportion of patients with C reactive protein ≤5 mg/L was higher in the standard tapering at week 14 as compared with faster regimens or no prednisolone. In subgroup analyses, the standard tapering was associated with a higher rate of CFCR at week 14 compared with the fast-tapering regimen in patients receiving ≥40 mg prednisolone at initiation of infliximab (64.3% vs 26.3%, p=0.04) and among patients admitted with acute severe UC (66.6% vs 23.5%, p<0.05). Similar data were seen at week 52. Prednisolone did not affect infliximab trough levels but increased infection rates (10/77 vs 2/70, p=0.03), in particular C. difficile infection. CONCLUSION: In UC patients with limited disease burden, prednisolone did not affect effectiveness of infliximab. However, patients with increased disease burden seem to benefit from corticosteroid combination therapy.

Biologics and targeted synthetic medicines for ulcerative colitis and Crohn's disease.

Ulcerative colitis and Crohn's disease are chronic inflammatory bowel diseases. Recent pivotal phase 3 trials involving treatments like interleukin-23-, sphingosin-1-phosphate- and Janus kinase inhibitors have demonstrated notable effectiveness. However, they have also unveiled significant side effects such as herpes zoster, lymphopenia and bradycardia. The introduction of novel treatments raises valid concerns necessitating increased collaboration with diverse medical specialities to address potentially severe side effects, and this is vital for enhancing the future care of individuals with inflammatory bowel diseases, as argued in this review.

Serum Extracellular Matrix Molecules and Their Fragments as Biomarkers of Inflammation and Fibrosis in Inflammatory Bowel Diseases - A Systematic Review.

BACKGROUND AND AIM: Contemporary techniques to assess disease activity or bowel damage in patients with inflammatory bowel disease (IBD), such as endoscopy and imaging, are either invasive or lack accuracy. Non-invasive biomarkers for this purpose remain an unmet medical need. Herein, we provide a comprehensive systematic review of studies evaluating blood extracellular matrix (ECM) biomarkers and their relevance in IBD. METHODS: We conducted a systematic review of PubMed, EMBASE, Web of Science, and Scopus to identify citations pertaining ECM biomarkers of IBD up to March 1, 2024. Studies were categorized based on marker subtype and clinical use. RESULTS: Thirty-one ECM markers were identified, 28 of these demonstrated the ability to differentiate IBD disease activity. Collagen III emerged as the most extensively investigated (1212 IBD patients), with the degradation marker C3M and deposition marker PRO-C3 being associated with IBD and subtypes. Collagen V markers C5M and PRO-C5 emerged as the most accurate single markers for diagnosis of IBD, with an area under the curves of 0.91 and 0.93, respectively. Overall, studies were characterized by variable endpoints. None of the studies included histological grading of intestinal damage, repair, or fibrosis formation as the primary outcome in relation to the ECM blood markers. CONCLUSIONS: Multiple ECM markers are linked with IBD and its phenotypes. However, more rigorous study designs and clearly defined endpoints are needed to ensure reproducibility and develop reliable and accurate biomarkers. ECM markers hold promise as they provide a 'window' into transmural tissue remodeling and fibrosis burden, warranting further investigation.

Non-TGFß profibrotic signaling in ulcerative colitis after in vivo experimental intestinal injury in humans.

Although impaired regeneration is important in many gastrointestinal diseases including ulcerative colitis (UC), the dynamics of mucosal regeneration in humans are poorly investigated. We have developed a model to study these processes in vivo in humans. Epithelial restitution (ER) and extracellular matrix (ECM) regulation after an experimental injury of the sigmoid colonic mucosa was assessed by repeated high-resolution endoscopic imaging, histological assessment, RNA sequencing, deconvolution analysis, and 16S rDNA sequencing of the injury niche microbiome of 19 patients with UC in remission and 20 control subjects. Human ER had a 48-h lag before induction of regenerative epithelial cells [wound-associated epithelial (WAE) and transit amplifying (TA) cells] along with the increase of fibroblast-derived stem cell growth factor gremlin 1 mRNA (GREM1). However, UC deconvolution data showed rapid induction of inflammatory fibroblasts and upregulation of major structural ECM collagen mRNAs along with tissue inhibitor of metalloproteinase 1 (TIMP1), suggesting increased profibrotic ECM deposition. No change was seen in transforming growth factor ß (TGFß) mRNA, whereas the profibrotic cytokines interleukin 13 (IL13) and IL11 were upregulated in UC, suggesting that human postinjury responses could be TGFß-independent. In conclusion, we found distinct regulatory layers of regeneration in the normal human colon and a potential targetable profibrotic dysregulation in UC that could lead to long-term end-organ failure, i.e., intestinal damage.NEW & NOTEWORTHY The study reveals the regulatory dynamics of epithelial regeneration and extracellular matrix remodeling after experimental injury of the human colon in vivo and shows that human intestinal regeneration is different from data obtained from animals. A lag phase in epithelial restitution is associated with induction of stromal cell-derived epithelial growth factors. Postinjury regeneration is transforming growth factor ß-independent, and we find a profibrotic response in patients with ulcerative colitis despite being in remission.

Peripheral Joint and Enthesis Involvement in Patients With Newly Diagnosed Inflammatory Bowel Disease: Symptoms, and Clinical and Ultrasound Findings - A Population-Based Cohort Study.

OBJECTIVES: Musculoskeletal [MSK] manifestations in patients with inflammatory bowel disease [IBD] are common and associated with poorer outcomes. Hence, early detection is important to optimally tailor treatment. We aimed to determine the prevalence and distribution of inflammatory lesions in peripheral joints and entheses in newly diagnosed IBD patients. DESIGN: Patients with newly diagnosed IBD from a prospective population-based inception cohort were consecutively included. Data on MSK symptoms were collected by questionnaires and by structured rheumatological interview. Peripheral joints and entheses were assessed clinically and by ultrasound [US], using standardized definitions. RESULTS: Of 110 included patients (mean age: 42 years, 40% male, 70 with ulcerative colitis [UC], 40 with Crohn's disease [CD]), a history of ≥1 peripheral musculoskeletal symptom was reported by 49%. Clinical examination revealed peripheral MSK manifestations in 56 [52.3%] patients; 29 [27.1%] had ≥1 tender and/or swollen joints and 49 [45.8%] ≥1 tender entheses. Small peripheral joints were predominantly affected. US found inflammation in ≥1 joint or enthesis in 52 [49.5 %] patients; 29 [27.4 %] had US synovitis in ≥1 joint, while 36 [34%] had US enthesitis. Fibromyalgia classification criteria were fulfilled in seven [7.9%] patients. There was no difference in clinical or US findings between patients with UC and CD, nor between patients with active and inactive IBD. CONCLUSION: Half of the patients with newly diagnosed IBD had inflammation in their peripheral joints and/or entheses, documented by rheumatological clinical and US evaluations. This indicates a need for multidisciplinary collaboration to ensure an optimal therapeutic strategy for suppressing inflammation in all disease domains.

Intestinal ultrasound in inflammatory bowel disease.

Intestinal ultrasound (IUS) is non-invasive, fast, cheap, and well-tolerated and requires no preparation and is thus applicable as a point-of-care monitoring tool of inflammatory bowel disease (IBD). Evidence suggests that IUS is comparable to other standard monitoring modalities, i.e., endoscopy, MRI, calprotectin, and C-reactive protein and might be more accurate in predicting response to treatment at an early stage consequently allowing for timely optimised treatment. This review finds that integrating IUS as the standard of care in every IBD outpatient clinic and as the primary outcome in future medical trials seems inevitable.

Infant Ustekinumab Clearance, Risk of Infection, and Development After Exposure During Pregnancy.

BACKGROUND: Evidence on ustekinumab safety in pregnancy is gradually expanding, but its clearance in the postnatal period is unknown. The aim of this study was to investigate ustekinumab concentrations in umbilical cord blood and rates of clearance after birth, as well as how these correlate with maternal drug concentrations, risk of infection, and developmental milestones during the first year of life. METHODS: Pregnant women with inflammatory bowel disease were prospectively recruited from 19 hospitals in Denmark and the Netherlands between 2018 and 2022. Infant infections leading to hospitalization/antibiotics and developmental milestones were assessed. Serum ustekinumab concentrations were measured at delivery and specific time points. Nonlinear regression analysis was applied to estimate clearance. RESULTS: In 78 live-born infants from 76 pregnancies, we observed a low risk of adverse pregnancy outcomes and normal developmental milestones. At birth, the median infant-mother ustekinumab ratio was 2.18 (95% confidence interval, 1.69-2.81). Mean time to infant clearance was 6.7 months (95% confidence interval, 6.1-7.3 months). One in 4 infants at 6 months had an extremely low median concentration of 0.015 µg/mL (range 0.005-0.12 µg/mL). No variation in median ustekinumab concentration was noted between infants with (2.8 [range 0.4-6.9] µg/mL) and without (3.1 [range 0.7-11.0] µg/mL) infections during the first year of life (P = .41). CONCLUSIONS: No adverse signals after intrauterine exposure to ustekinumab were observed with respect to pregnancy outcome, infections, or developmental milestones during the first year of life. Infant ustekinumab concentration was not associated with risk of infections. With the ustekinumab clearance profile, live attenuated vaccination from 6 months of age seems of low risk.

IAPs and RIPK1 mediate LPS-induced cytokine production in healthy subjects and Crohn's disease.

Innate immune activity fuels intestinal inflammation in Crohn's disease (CD), an inflammatory bowel disease. Identification and targeting of new molecular regulators of the innate activity are warranted to control the disease. Inhibitor of apoptosis proteins (IAPs) regulate both cell survival and inflammatory signaling. We investigated the effects of IAP inhibition by second mitochondria-derived activator of caspases (SMAC) mimetics (SMs) on innate responses and cell death to pathogen-associated molecular patterns in peripheral blood mononuclear cells (PBMCs) and monocytes. IAPs inhibited lipopolysaccharide (LPS)-induced expression of proinflammatory interleukin (IL)-1ß, IL-6. Likewise, LPS (but not muramyl dipeptide or Escherichia coli) induced TNF-α was inhibited in CD and control PBMCs. The SM effect was partially reversed by inhibition of receptor-interacting serine/threonine-protein kinase 1 (RIPK1). The effect was mainly cell death independent. Thus, IAP inhibition by SMs leads to reduced production of proinflammatory cytokines and may be considered in the efforts to develop new therapeutic strategies to control CD.