Introduction

Perianal fistulas occur in up to 30% of patients with Crohn’s disease (pfCD) and frequently require a combined medical and surgical treatment approach. Hyperbaric Oxygen Therapy (HBOT) has previously shown benefit in treatment-refractory pfCD.

Aims & Methods

In this pilot study, we aim to assess the feasibility of surgical fistula closure 4 weeks after HBOT, and efficacy of combining surgical closure and 8 weeks HBOT.
Patients with complex pfCD refractory to at least 6 months of anti-TNF therapy were included in this study. All patients received a seton prior to starting treatment with 40 sessions (8 weeks) of HBOT (each lasting 110 minutes, with 5-minute air breaks) with 100% oxygen at 2.4 atmosphere. At week 4 the seton was removed, and surgical closure of the internal fistula opening was attempted. All patients continued stable dose of medical treatment during the study. Response was assessed by the fistula drainage assessment (FDA) and the perianal disease activity index (PDAI) at week 9, 26 and 52, and by pelvic MRI at week 9 and 26. MRI response was defined as a decrease of 2 points in MAGNIFI-CD score, MRI remission as a MAGNIFI-CD ≤6. (Serious) Adverse Events (AE) were reported for 52 weeks. Univariate logistical regression was used to explore potential variates associated with PDAI response (≤4) at week 26.

Results

Ten patients completed treatment and were analyzed (Table 1). All patients completed HBOT and underwent a technically successful surgical procedure at week 4. No proctitis was encountered at week 4 during examination under anesthesia. PDAI response was achieved by 30%, 60%, 58% at week 9, 26 and 52, respectively. FDA response/remission was achieved in 50%/20%, 80%/40% and 80%/50% of patients at week 9, 26 and 52, respectively. MRI response/remission was achieved in 60%/10% and 60%/20% of patients at week 9 and 26, respectively. No significant parameters were associated with PDAI response at week 26 in univariate logistical regression. (S)AEs included one patient with a potential oxygen toxicity seizure without long term effects, and one patient reported claustrophobia, no new AEs were reported.

Table 1 Patient and fistula characteristics (n=10)

Age (years), mean (95%CI)	30.5 (23.7 – 27.3)
Female, n (%)	9 (90)
Crohn’s disease duration (years), median [IQR]	9.0 [1.8 – 14,5]
Perianal disease duration (years), median [IQR]	3.5 [1.8 – 7.3]
Proctitis at baseline, n (%)	2 (20)
Internal fistula openings, n (%)	1: 7 (70) 2: 3 (30)
Primary fistula location, n (%)	anterior: 3 (30) lateral: 3 (30) posterior: 4 (40)
Fistula tracts, mean (95%CI)	3.5 (2.8 – 6.3)
Previous fistula surgeries, mean (95%CI)	4.1 (2.5 – 5.7)
Perianal fistula classification (Geldof et al.; class 1 – 4b), n (%)	2a: 3 (30) 2b: 1 (10) 2c-i: 1 (10) 2c-ii: 5 (50)

Conclusion

HBOT is feasible in combination with surgical therapy in patients with complex pfCD refractory to anti-TNF therapy. Patients had long-lasting benefit of the combined treatment approach. Further translational data are currently analyzed to clarify mechanisms of action and to explore potential biomarkers for therapy response.

Disclosure

LM, KB, JT and RvH have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this abstract. JS is President-elect of the European Society of Gastrointestinal and Abdominal Radiology. GD has served as consultant for AbbVie, Astrazeneca, Alimentiv, Bristol-Myers Squibb, Boehringer Ingelheim, Celltrion, Cosmo, Eli Lilly, Galapagos, GSK, Johnson and Johnson, Takeda, Pfizer Inc, Polpharma, Prometheus Biosciences, Tillotts and Ventyx; received speaker fees from AbbVie, Boehringer Ingelheim, Celltrion, Eli Lilly, Johnson and Johnson, Takeda, Pfizer Inc and Tillotts. CB has received grants from Boehringer Ingelheim and Roche; speakers honoraria from AbbVie, Janssen, Galapagos, Takeda, and Tillotts. KG has received grants from Pfizer Inc, Celltrion and Galapagos; consultancy fees from AbbVie, Arena Pharmaceuticals, Galapagos, Gilead, Immunic Therapeutics, Janssen Pharmaceuticals, Novartis, Pfizer Inc., Samsung Bioepis and Takeda and speaker’s honoraria from Celltrion, Ferring, Janssen Pharmaceuticals, Novartis, Pfizer Inc, Samsung Bioepis, Takeda and Tillotts.

Introduction

Short bowel syndrome (SBS) is a severe complication of extensive small intestinal resection, most commonly occurring in Crohn’s disease (CD), a chronic inflammatory disorder defined by transmural immune infiltration. Cytokines and chemokines are central mediators in the immune cascade driving intestinal inflammation and tissue damage^1,2. Despite advances in care, no biomarkers currently predict SBS onset or progression to intestinal failure (IF). Profiling systemic cytokine and chemokine signatures may thus offer novel insight into disease trajectory and risk stratification.

Aims & Methods

This study investigates circulating inflammatory mediators in patients with established IF/SBS and CD patients at high risk of progression. A total of 150 patients with CD were enrolled and stratified into five groups based on intestinal function and surgical history: A1, SBS with IF requiring parenteral nutrition (PN) or intravenous fluids; A3, SBS without IF and inactive disease; B, high risk of IF with multiple or extensive resections; C1, low risk for IF with no history of resection; and C2, low risk for IF with prior resection. Serum cytokine and chemokine profiles were quantified at baseline (T0) and after six months (T6) using the human 27-PLEX multiplex immunoassay.

Results

Serum cytokines and chemokines profiling at baseline (T0) and after six months (T6) revealed distinct inflammatory patterns across the study groups. Patients with SBS and IF (group A1) showed persistently elevated levels of IP-10, IL-12, MIP-1α, and G-CSF, reflecting sustained immune activation. Whereas, patients at high risk of IF (group B) displayed increased Eotaxin, bFGF, IL-15, and IL-6, indicative of subclinical inflammation and possible tissue remodelling.
A general reduction in cytokine levels was observed at T6, though anti-inflammatory mediators remained minimally modulated, suggesting ongoing low-grade inflammation. Comparisons between groups highlighted divergent cytokine signatures correlating with disease severity and nutritional support requirements.

Conclusion

These findings suggest that specific circulating cytokines may serve as potential biomarkers for early identification of patients at risk of IF. The differential expression patterns observed across groups support their relevance in stratifying disease severity in CD and SBS. Further large-scale studies are needed to validate these preliminary results and to fully establish their prognostic significance.
Funded by: 2.1 “Rafforzamento e potenziamento della ricerca biomedica del SSN”, finanziato dall’Unione europea – NextGenerationEU, CUP C53C22001140007. 2022 PNRR Project “Changing the future of intestinal failure in intestinal chronic inflammation: towards innovative predictive factors and therapeutic targets” code: PNRR-MAD-2022-12376791.

References

1. Friedrich M, Pohin M, Powrie F. Cytokine Networks in the Pathophysiology of Inflammatory Bowel Disease. Immunity. 2019;50(4):992-1006. doi:10.1016/j.immuni.2019.03.017
2. Singh UP, Singh NP, Murphy EA, et al. Chemokine and cytokine levels in inflammatory bowel disease patients. Cytokine. 2016;77:44-49. doi:10.1016/j.cyto.2015.10.008

Introduction

Targeting mitochondrial function and oxidative stress is successful in animal models of IBD. NLRX1 is a mitochondrial associated protein upregulating mitochondrial metabolism: It reduces oxidative stress and decreases pro-inflammatory cell differentiation and cytokine release. NX-13 is a first-in-class, orally active, once-daily, gut-selective NLRX1 agonist with low systemic exposure in development for Ulcerative Colitis (UC). In three mouse models of IBD, NX-13 effectively activated NLRX1 to reduce inflammatory responses and disease severity. In two phase 1 studies (56 healthy subjects; 38 UC patients) NX-13 was well tolerated. Low systemic drug exposure relative to stool levels suggested a gut-selective drug distribution. Phase 1B topline results were reported previously¹. We now present data demonstrating target engagement and downstream effects consistent with the preclinical mechanism of action (MOA).

Aims & Methods

In this double-blind phase 1B trial, 36 patients with active UC (Total Mayo Score 4-10; Mayo endoscopic subscore 2-3) were randomly assigned to NX-13 250mg Immediate Release (IR), 500mg IR, 500mg Delayed Release (DR) or Placebo to be taken QD for 4 weeks. We report pharmacodynamic results based on expression of NLRX1 and downstream immunometabolic markers in colonic tissue samples collected at screening and week 4 of treatment. NLRX1 protein levels were measured by immunohistochemistry scored by a blinded pathologist, and immunometabolic markers were measured by qRT-PCR.

Results

All NX-13 treated groups showed target engagement through mean positive increases in NLRX1 expression versus placebo at week 4, with more pronounced upregulation observed in responding patients (Table 1A). Gene expression profiles after 4 weeks of treatment showed upregulation of the mitochondrial metabolism gene MT-ND3, with downstream reductions in HIF1α and NLRP3 in the NX-13 IR groups but not in the placebo group (Table 1B). NX-13 250mg IR dosed patients also displayed downstream decreases in IL-17α and IL-1β gene expression, and the 500mg IR group showed reduction in IL-1β. Changes in NLRX1 expression and immunometabolic markers correlated with clinical response to NX-13 and were numerically greater in responding IR-dosed patients compared to non-responding patients (Table 1).

A. Immunohisto-chemistry	Definition	Subgroup	Placebo (n=2)		NX-13 250mg IR (n=8)		NX-13 500mg IR (n=8)		NX-13 500mg DR (n=8)
NLRX1 Composite Score Change from Baseline	Mean (Standard Error) of 4-point score accounting for NLRX1 intensity and number of positive cells in the epithelium and lamina propria	Responder	n/a	n/a	0.54	(0.36)	2.58	(0.46)	1.42	(0.68)
		Non-responder	-0.38	(0.38)	0.25	(0.25)	1.35	(0.84)	0.7	(0.76)
B. Gene Expression	Definition		Placebo (n=1)		NX-13 250mg IR (n=7)		NX-13 500mg IR (n=6)		NX-13 500mg DR (n=5)
MT-ND3	Median (Interquartile Range) fold change over baseline expression	Responder	(n/a)	(n/a)	1.37	(1.2-1.54)	1.52	(1.14-1.90)	n/a	n/a
		Non-responder	0.71	(n/a)	0.86	(0.45-1.28)	1.04	(0.96-1.14)	0.76	(0.34-1.68)
HIF1α		Responder	(n/a)	(n/a)	0.74	(0.53-0.81)	0.83	(0.80-0.86)	n/a	n/a
		Non-responder	1.06	(n/a)	2.18	(1.07-3.29)	0.95	(0.55-1.5)	1.11	(0.69-2.50)
NLRP3		Responder	(n/a)	(n/a)	0.65	(0.58-0.88)	0.59	(0.56-0.62)	n/a	n/a
		Non-responder	1.26	(n/a)	1.89	(1.28-2.50)	0.92	(0.30-2.04)	1.35	(0.64-2.34)

Conclusion

Treatment with NX-13 induced upregulation of its target, NLRX1, as well as downstream immunometabolic signaling consistent with preclinical MOA studies. Most importantly, target engagement parallels clinical benefit. This novel mechanism of action warrants further study and is currently being evaluated in a phase 2 proof of concept study (NCT05785715).

References

¹ L Peyrin-Biroulet, S Danese, J F Colombel, F Rieder, A Yarur, B Verstockt, S Lichtiger, R Mosig, F Cataldi, B Feagan, P577 A Phase 1b Study to Evaluate Safety, Tolerability, Pharmacokinetics and Clinical Efficacy of the Nucleotide-binding oligomerization domain, Leucine rich Repeat containing X1 (NLRX1) agonist NX-13 in Ulcerative Colitis, Journal of Crohn's and Colitis, Volume 17, Issue Supplement_1, February 2023, Pages i705–i706

Disclosure

BV - AbbVie, Alimentiv, Applied Strategic, Atheneum, Biora Therapeutics, Biogen, Bristol Myers Squibb, Celltrion, Chiesi, Falk, Ferring, Galapagos, Guidepont, Inotrem, Ipsos, Janssen, MSD, Mylan, Pfizer, Progenity, R-Biopharm, Sandoz, Sossei Heptares and Takeda, Tillots Pharma, Truvion and Viatris;
SV - grants from: AbbVie, J&J, Pfizer, Takeda and Galapagos, consulting / speaking fees from: AbbVie, Abivax, AbolerIS Pharma, AgomAb, Alimentiv, Arena Pharmaceuticals, AstraZeneca, Avaxia, BMS, Boehringer Ingelheim, Celgene, CVasThera, Cytoki Pharma, Dr Falk Pharma, Ferring, Galapagos, Genentech-Roche, Gilead, GSK, Hospira, Imidomics, Janssen, J&J, Lilly, Materia Prima, MiroBio, Morphic, MrMHealth, Mundipharma, MSD, Pfizer, Prodigest, Progenity, Prometheus, Robarts Clinical Trials, Second Genome, Shire, Surrozen, Takeda, Theravance, Tillots Pharma AG, Zealand Pharma;
BS - consultant for AbbVie, Boehringer Ingelheim, Bristol Myers Squibb, Celgene, Falk, Janssen, Lilly, Pfizer, PredictImmune and Takeda; and received speaker’s fees from AbbVie, BMS, CED Service GmbH, Falk, Ferring, Janssen, Pfizer and Takeda (served as representative of the Charité);
FR - Adnovate, Agomab, Allergan, AbbVie, Arena, Boehringer-Ingelheim, Celgene/BMS, CDISC, Celsius, Cowen, Ferring, Galapagos, Galmed, Genentech, Gilead, Gossamer, Granite, Guidepoint, Helmsley, Horizon Therapeutics, Image Analysis Limited, Index Pharma, Jannsen, Koutif, Mestag, Metacrine, Mopac, Morphic, Organovo, Origo, Pfizer, Pliant, Prometheus Biosciences, Receptos, RedX, Roche, Samsung, Sanofi, Surmodics, Surrozen, Takeda, Techlab, Teva, Theravance, Thetis, UCB, Ysios, 89Bio;
SL – owns Landos Stock;
RM – employee of Landos;
FC – employee of Landos;
SD - AbbVie, Alimentiv, Allergan, Amgen, Applied Molecular Transport, AstraZeneca, Athos Therapeutics, Biogen, Boehringer Ingelheim, Bristol Myers Squibb, Celgene, Celltrion, Dr Falk Pharma, Eli Lilly, Enthera, Ferring Pharmaceuticals Inc., Gilead, Hospira, Inotrem, Janssen, Johnson & Johnson, Morphic, MSD, Mundipharma, Mylan, Pfizer, Roche, Sandoz, Sublimity Therapeutics, Takeda, Teladoc Health, TiGenix, UCB Inc., Vial, Vifor;

Introduction

Perianal fistulising Crohn’s disease (PFCD) affects up to 20% of patients with Crohn’s Disease (CD). PFCD can cause pain, purulent discharge and faecal incontinence, leading to significant morbidity and reduction in quality of life. The use of biologic therapy, antibiotics and surgical intervention remain the mainstay of management of perianal fistulas.

Aims & Methods

This study aims to review current practices in the management of PFCD across two large tertiary IBD centres. This retrospective cohort study assessed adult patients with PFCD between two tertiary Australian hospitals between 2006 to 2024. Patients with PFCD were identified using prescribing data. CD phenotype, therapy and fistula-related data were extracted. Biologic choice and therapeutic drug monitoring, antibiotic choice and duration, surgical intervention, and length of stay in hospital were monitored. Cross-sectional disease activity of perianal fistulizing disease was assessed at the time of data collection using clinical fistula symptom grade and radiological assessment were available. Clinical remission was defined as fistula symptom grade of 1 or less. Radiological remission was defined by healing fistula tracts or no active inflammation seen on MRI. The study was approved by the Central Adelaide Local Health Network Human Research Ethics Committee (HREC19145).

Results

Gender Male, n Female, n Age, y, median (IQR)	n = 57 30 27 40 (31-54)
Active Smoker, n (%)	14 (24.5)
Median length of clinical follow up, months, n (IQR)	46.5 (23.8-72.3)
Antibiotics Prescribed Metronidazole, n treated (%) Amoxicillin / Clavulanic acid, n treated (%) Others, n treated (%)	47 (68.1) 13 (27.7) 9 (4.2)
Duration of Antibiotics Metronidazole, median duration, days (IQR) Amoxicillin / Clavulanic acid, median duration, days (IQR) Others, median duration, days (IQR)	5 (5-7) 5 (5-10) 14 (7-14)
Biologic therapy Total patients on biologic therapy, n (%) Infliximab, n (%) Adalulimab, n (%) Ustekinumab, n (%)	56 (98.2) 43 (75.4) 11 (19.3) 2 (3.5)
Therapeutic Drug Monitoring (Infliximab) Infliximab level performed, n (%) Subtherapeutic (Infliximab level <10), n (%) Active disease and subtherapeutic (Infliximab level <10), n (%)	37 (86%) 30 (81.1%) 12 (40%)
Remission status Clinical Remission, n (%) - Defined as Fistula symptom grade of 1 or less Radiological Remission, n (%) - Defined as healing fistula tracts or no active inflammation seen on MRI	48 (84.2) 33 (57.8)
Subtherapeutic Therapeutic Drug Monitoring (All biologic agents) In Remission, n (%) Active Disease, n (%)	18 (56.2) 14 (43.8)

Table 1. Baseline characteristics

57 patients (median age, 40 years (31-54); 52.6% male) with PFCD were included in the study and followed over a median duration of 46.5 months (23.8-72.3). There were a total of 157 individual surgical procedures over the period, 2.75 per patient, most of which (94.2%) were examination under anaesthesia. Antibiotic therapy was dispensed for either perianal sepsis or an actively draining fistula in 26 patients, 2.65 number of courses per patient. The most common antibiotic prescribed was Metronidazole (68.1%), followed by Amoxicillin / Clavulanic acid (27.7%). The median duration of antibiotic therapy was 5 days (5-7) for Metronidazole and 5 days (5-10) for Amoxicillin / Clavulanic acid. There were 56 (98.2%) patients on biologic therapy. The most common biologic agent was Infliximab (75.4%), followed by Adalimumab (19.3%) and Ustekinumab (3.5%). At the time of analysis, 48 patients (84.2%) were in clinical remission and 33 patients (57.8%) were in radiographical remission. In patients treated with infliximab, 37/43 (86%) had therapeutic drug monitoring performed. Amongst these, 30 (81.1%) had subtherapeutic levels (defined as Infliximab level < 10), with 12/30 (40%) of patients having active PFCD.

Conclusion

Across two tertiary IBD centres, management of PFCD is variable and not in keeping with current guidelines. Short courses of antibiotic therapy were used, and the majority of patients had subtherapeutic drug levels when tested. Optimising outcomes for patients with PFCD requires awareness of best practice and a multidisciplinary team approach.