Introduction

The pathophysiological mechanism involved in irritable bowel syndrome (IBS) is thought to be multifactorial, involving the gut-brain axis and the immune system. Despite this complexity, dietary restriction of fermentable oligo-, dis-, mono- saccharides, and polyols (FODMAPs) has become the first line of treatment, improving symptoms in up to 80% of patients (1). FODMAPs are poorly absorbed in the small intestine and serve as a substrate for the colonic microbiota, which has been proposed as a key mediator of FODMAP tolerance and symptom development. Considering that both the gut microbiota and the (in)tolerance to individual FODMAPs are highly personalised (2), there is a growing need to understand the host-microbiota interactions underlying individual responses to FODMAP restriction and intake. This personalised interplay may be key to more targeted dietary interventions for IBS.

Aims & Methods

We aimed to disentangle the role of the gut microbiota in FODMAP tolerance by exploring microbial dynamics upon restriction and reintroducing individual FODMAPs. To this end, we performed 16S rRNA gene sequencing of over 1,700 faecal samples from 463 IBS patients participating in two clinical trials: a) The DOMINO trial (3), where primary-care patients underwent a FODMAP-lowering diet and b) A cohort of 117 tertiary-care patients underwent a strict FODMAP-restriction followed by a blinded re-introduction of 6 FODMAPs powders (2). Response to the diet was defined as a reduction of at least 50 points on the IBS symptom severity scale. Linear and logistic mixed models were used to assess the relation between the microbiome, response to dietary intervention, host genetics and 32 blood and faecal parameters.

Results

Participants with dysbiotic microbiota at baseline were shown to be less likely to respond to the dietary restriction (p-value=0.01). These participants also showed higher levels of fecal calprotectin, secretory IgA and eosinophil-derived neurotoxin, suggesting immune activation in this subgroup of IBS patients (p-value<0.05). In both cohorts, limiting FODMAP intake was associated with decreased Bifidobacterium abundance (FDR<0.01). Moreover, a dose-dependent effect was observed as depletion was less severe in the FODMAP-lowering DOMINO diet. This effect was independent of response and IBS subtype. Furthermore, total bacterial biomass did not change during the restriction or the reintroduction period. However, we found 25 significant associations between individual FODMAPs and gut bacteria. The reintroduction of galacto-oligosaccharides and fructans restored the levels of Bifidobacterium, while polyols increased the abundance of Anaerostipes, regardless of participants’ tolerance (FDR<0.05). In addition, we observed distinct dynamics in the gut microbiota associated with the tolerance of specific FODMAPs, although they did not reach significance after multiple testing corrections at the current sample size. For example, participants intolerant to sorbitol showed an increase in Alistipes upon exposure to this compound (p-value<0.05, FDR>0.05).

Conclusion

Our results suggest that microbiota composition at baseline influences the clinical response to FODMAP restriction. A low-FODMAP diet does not induce drastic changes in the microbiome composition, although we confirmed the negative impact of dietary restriction on the abundance of Bifidobacterium. However, the less restrictive DOMINO diet results in a milder depletion, suggesting that moderate FODMAP reduction may better preserve beneficial microbiota while still offering symptom relief. Finally, we found evidence for a link between microbial dynamics and FODMAP tolerance, although this needs to be confirmed in larger cohorts.

References

(1) Staudacher HM, Whelan K The low FODMAP diet: recent advances in understanding its mechanisms and efficacy in IBS Gut 2017;66:1517-1527.
(2) Van den Houte K, Colomier E, Routhiaux K, Mariën Z, Schol J, Van den Bergh J, Vanderstappen J, Pauwels N, Joos A, Arts J, Caenepeel P, De Clerck F, Matthys C, Meulemans A, Jones M, Vanuytsel T, Carbone F, Tack J. Efficacy and Findings of a Blinded Randomized Reintroduction Phase for the Low FODMAP Diet in Irritable Bowel Syndrome. Gastroenterology. 2024
(3) Carbone F, Van den Houte K, Besard L DOMINO Study Collaborators, et al Diet or medication in primary care patients with IBS: the DOMINO study - a randomised trial supported by the Belgian Health Care Knowledge Centre (KCE Trials Programme) and the Rome Foundation Research Institute Gut 2022;71:2226-2232.

Disclosure

JT has given Scientific advice to AlfaWassermann, Allergan, Christian Hansen, Danone, Grünenthal, Ironwood, Janssen, Kiowa Kirin, Menarini, Mylan, Neutec, Novartis, Noventure, Nutricia, Shionogi, Shire, Takeda, Theravance, Tramedico, Truvion, Tsumura, Zealand and Zeria pharmaceuticals, has received research support from Shire, Sofar and Tsumura, and has served on the Speaker bureau for Abbott, Allergan, AstraZeneca, Janssen, Kyowa Kirin, Menarini, Mylan, Novartis, Shire, Takeda, Truvion and Zeria. Funding was provided by a Methusalem grant from Leuven University to JT This study was supported by a research grant from the Belgian Health Care Knowledge Centre (KCE).

Introduction

Non-celiac gluten/wheat sensitivity (NCGWS) is characterized by gastrointestinal and extra-intestinal symptoms triggered by gluten/wheat ingestion. Symptoms of NCGWS overlap with those of irritable bowel syndrome (IBS) or functional dyspepsia (FD). Due to diagnostic challenges and symptom overlap, data on the prevalence and predictors of NCGWS among patients with IBS or FD, especially those with refractory symptoms, are limited.

Aims & Methods

This was a prospective, multicentric, double-blind, placebo-controlled, crossover trial conducted from October 2021 to March 2023 in India.This was prospectivly registered with the clinical trials Registry, INDIA (CTRI/2021/10/037323). Adults aged 18–65 years with Rome IV-defined irritable bowel syndrome (IBS) or functional dyspepsia (FD) refractory to standard treatment were enrolled after excluding celiac disease, wheat allergy, and alarm features. Participants underwent a two-step diagnostic protocol. In Step I, patients adhered to a 6-week strict gluten-free diet (GFD) under dietitian supervision. Weekly assessments of gastrointestinal and extra-intestinal symptoms, health-related quality of life (HRQoL), and psychological scores were performed using validated instruments. Gluten responders—defined by ≥30% reduction in one to three primary symptoms—were advanced to Step II: a randomized, double-blind, placebo-controlled gluten challenge with crossover. Subjects received indistinguishable gluten or placebo cookies (8 g/day) for one week, followed by a one-week washout and crossover. A ≥30% symptom difference between gluten and placebo phases confirmed non-celiac gluten/wheat sensitivity (NCGWS). Primary outcome was NCGWS prevalence; secondary outcomes included symptom and HRQoL changes post-GFD and predictors of NCGWS. Statistical analyses included intention-to-treat principles and multivariable regression to identify baseline predictors.

Results

Of the 252 patients screened, 177 were enrolled for 6-week GFD (step I), and 154 patients completed this phase (mean age 41.9±14.2 years, 53.2% males). Eighty two (52.3%) patients responded to GFD, of whom 77 entered step 2 (DBPCGC). Thirty one (20.1%) patients had significant symptom worsening on blinded gluten ingestion, suggesting the presence of NCGWS. Independent predictors of NCGWS were female gender, FD-IBS overlap, headache, fatigue, and anxiety. Significant improvements in gastrointestinal symptoms, health-related quality of life, and psychological scores were observed after GFD in responders. No significant impact of diet sequence was noted.

Conclusion

Introduction

Current treatment options for IBD are limited by low clinical remission rates and loss of response. Most therapies target single pathogenic pathways and while combinations of biologics targeting different pathogenic cytokines can increase clinical remission rates, dosing schedules are inconvenient. JAK inhibitors, target multiple cytokine pathways, but are limited by safety concerns.
Salt-inducible kinases (SIKs) are a subfamily of serine/threonine kinases in the AMP-activated protein kinase (AMPK) family and act as key regulators of immune cell signaling. SIK inhibitors have been shown to target multiple cytokine pathways.
Three SIK isoforms exist: SIK1, SIK2 and SIK3. SIK inhibitors targeting multiple isoforms have been investigated in clinical trials. Although there have been signals of activity in patients with ulcerative colitis and psoriasis, limited efficacy and safety concerns related to SIK1 and 2 inhibition have hampered their development.

Aims & Methods

We performed structure based drug design to identify highly potent and selective SIK3 inhibitors that could offerbest in class efficacy and safety for the treatment of various auto-immune diseases. Our effort led to to the discovery of 100s of compounds spanning SIK3 binding sites. Compounds were tested in protein and cell-based assays to evaluate potency and selectivity against SIK3 and in a phenotypic human whole blood TNFα assay. Lead optimization involving rigorous testing in safety and pharmacology panels, resulted in the selection of lead candidates that were tested in a variety of translational models to identify the most efficacious compounds. Human PK predictions were performed using non-clinical in vivo PK assessments and allometric scaling leading to the selection of the drug candidate, which entered GLP toxicology studies.

Results

O3R-5671 is a highly potent and specific SIK3 inhibitor with sub-nanomolar potency for SIK3 and low activity against SIK1 and 2 and over all human kinases. It demonstrated potent activity in a panel of human primary phenotypic cell assays inhibiting TNFα, IL-12, and IL-23 release in LPS-stimulated myeloid cells, and inhibiting TNFa release in LPS-stimulated human whole blood. O3R-5671 also inhibited activation of TCR-stimulated human primary T cells and induced IL-10 secretion from myeloid cells.
In vivo, O3R-5671 demonstrated dose-dependent activity in a mouse LPS challenge model, dose-dependent efficacy in two distinct mouse models of IBD, and dose-dependent efficacy in mouse models of IL-23-induced psoriasis and psoriatic arthritis. Cross-species PK and allometric scaling were used to predict O3R-5671’s human PK profile- which is expected to be conducive to potent SIK3 inhibition and clinical efficacy in patients with IBD.
O3R-5671 demonstrated a highly attractive profile in ADME and in vitro safety panels. Six-week GLP toxicity studies in rats and dogs established no observed adverse effect levels (NOAELs) which support dosing in humans with doses that are predicted to be pharmacologically active with a large safety margin.

Conclusion

O3R-5671 is a highly specific and potent SIK3 inhibitor that is predicted to have a flat PK profile in humans. These properties should allow O3R-5671 to apply strong drug pressure on SIK3 while sparing SIK1 and 2. This is expected to result in the inhibition of multiple pathogenic cytokines including TNFa and IL-23, both of which have been validated as IBD targets. A clinical trial is ongoing to establish the safety and PK profile of O3R-5671 and understand its effect on pharmacodynamic biomarkers.

Disclosure

All authors were employed by Galapagos who discovered O3R-5671 or Novalix, a CRO that was employed by Galapagos. Some authors are employed by Onco3R therapeutics, who are currently developing O3R-5671