Introduction

Very early onset inflammatory bowel disease (VEO-IBD) is often associated with a severe disease course and unique characteristics including an underlying monogenic defect. In this study, we identified new pathogenic mutations in CGNL1 associated with VEO-IBD and other inflammatory GI disease. CGNL1 (Cingulin Like 1) encodes an epithelial junctional protein whose function was previously unknown in the gastrointestinal tract.

Aims & Methods

Whole exome sequencing (WES) was performed on the affected patient with VEO-IBD and all first-degree relatives with IBD and other inflammatory disease. Intestinal epithelial organoids (IEOs) were generated from the affected patient and were characterized by transepithelial electrical resistance (TEER), FITC-dextran permeability assay on epithelial cell monolayer, immunostaining, RNA sequencing, and transmission electron microscopy (TEM). In addition, we generated a new Cgnl1^-/- mouse model, which was characterized using FITC-dextran permeability assay, TEM, dextran-sodium sulfate (DSS)-induced colitis, and infections by Citrobacter rodentium and Clostridioides difficile. Single-cell datasets were analyzed to determine CGNL1 expression in IBD, primary sclerosing cholangitis (PSC), and autoimmune hepatitis (AIH).

Results

In the affected patient with VEO-IBD who required early total colectomy and pouch formation with coexistent PSC and celiac disease, WES identified two rare, new, pathogenic variants in the CGNL1 gene. Both pathogenic variants were also present in the patient’s younger sister, who has a similar history including early-onset, fulminant ulcerative colitis requiring total colectomy with ileostomy and PSC-AIH overlap syndrome. Furthermore, multiple relatives of the patient suffer from IBD and other inflammatory conditions including celiac disease, eosinophilic esophagitis, and type-1 diabetes. The RNA and protein levels of CGNL1 were significantly diminished in the patient’s intestinal epithelial cells compared to that of healthy individuals and other IBD patients by RNA-seq, immunoblotting, and immunostaining. The patient’s IEOs from pouch body and pre-pouch ileum formed smaller 3D spheroids with altered cell composition and significantly impaired barrier function compared to those from healthy controls and other IBD patients. Immunofluorescence and TEM demonstrated that CGNL1 is required for the assembly of junctional complexes in human IEOs and an epithelial cell line. Similarly to findings from the patient, impaired junctional complexes in intestinal epithelial cells and elevated intestinal permeability were present in Cgnl1^-/- mice at steady state. Cgnl1^-/- mice showed substantial vulnerability to DSS-induced colitis and bacterial infections that directly compromise the epithelial barrier. In addition, 6-month-old Cgnl1^-/- mice exhibited spontaneous inflammation in the colon and terminal ileum due to disrupted intestinal barrier, which was microbiome-dependent. Furthermore, single-cell analysis revealed diminished expression of CGNL1 in the intestinal and hepatic epithelial cells from patients with IBD or PSC/AIH, respectively.

Conclusion

The pathogenic CGNL1 variants contribute to VEO-IBD by disrupting gut barrier integrity, as demonstrated by patient’s cells and novel murine models. This study expands our understanding of epithelial barrier impairment in the pathogenesis of VEO-IBD, and highlights intestinal epithelium as a therapeutic target in some IBD patients.

Introduction

Cholestatic pruritus is common, debilitating and undertreated in patients with primary biliary cholangitis (PBC). Here, we describe the results of GLISTEN (NCT04950127), a Phase 3 study investigating the efficacy and safety of the ileal bile acid transporter inhibitor linerixibat for pruritus in PBC.

Aims & Methods

In this double-blind, randomised, placebo-controlled study, patients with PBC and moderate-to-severe pruritus received oral linerixibat 40 mg or placebo twice daily. Pruritus severity and pruritus-related sleep interference were assessed using a 0–10 numerical rating scale. The primary endpoint was change from baseline in worst itch over 24 weeks. Secondary endpoints included: at Week 2, change in worst itch; over 24 weeks, change in sleep interference; at Week 24, proportion of responders (≥ 2-, ≥ 3-, ≥ 4-point reduction in worst itch) and analysis of responses to 2 patient global impression items (itch severity and change). Safety endpoints included adverse event (AE) reporting.

Results

238 patients were randomised; 95% were female, itch severity was mean (standard deviation [SD]) 7.34 (1.54), 52% had alkaline phosphatase < 1.67 times upper limit of normal, and 47% were receiving stable therapy for pruritus. Pruritus improvement over 24 weeks was significantly greater with linerixibat than placebo: least-squares (LS) mean change -2.86 versus -2.15, adjusted mean difference -0.72; p = 0.001. At Week 24, the observed mean (SD) difference from baseline in pruritus was -3.66 (2.50) with linerixibat and -2.82 (2.32) with placebo. The effect of linerixibat was rapid and superior to placebo at Week 2: LS mean change -1.78 versus -1.07, adjusted mean difference -0.71; p < 0.001. Linerixibat also significantly improved pruritus-related sleep interference over 24 weeks versus placebo: LS mean change ‑2.77 versus -2.24, adjusted mean difference -0.53; p = 0.024. At Week 24, more patients on linerixibat than placebo achieved a ≥ 2-point (68% vs 64%), ≥ 3-point (56% vs 43%) or ≥ 4-point (41% vs 29%) reduction in pruritus and a higher proportion of linerixibat than placebo-treated patients reported their pruritus was very much improved (55% vs 37%) or absent (21% vs 9%). AEs reported more frequently with linerixibat than placebo were predominantly gastrointestinal (GI), including diarrhoea (61% vs 18% of patients) and abdominal pain (18% vs 3% of patients); 4% of patients in the linerixibat group discontinued treatment due to diarrhoea.

Conclusion

In patients with PBC and moderate-to-severe pruritus, linerixibat rapidly and significantly improved pruritus and pruritus-related sleep interference versus placebo. While GI AEs were more common with linerixibat than placebo, they rarely led to treatment discontinuation.

Disclosure

Funded by GSK. Various authors declare conflicts of interest as consultants, employee, recipients of grants and stockholders. These will be reported in full during the presentation.