P0121 Molecular features of extracellular matrix activity persist in patients who achieve mucosal healing with ustekinumab induction
Authors: Saifuddin A , Cozzetto D , Powell N 
Published: January 2025

Abstract

Background
Phase 3 trials demonstrate rates of secondary loss of response of up to 40% for many advanced therapies in ulcerative colitis (UC). At a molecular level, this may be explained by persistence of inflammatory mediators in the mucosa despite successful treatment induction, and transcripts involved in leukocyte infiltration persist in patients responding to infliximab and vedolizumab compared to non-IBD controls [1]. We considered if any disease-relevant transcripts persisted in ustekinumab induction responders and if these differed depending on symptom resolution.

Methods
We interrogated data from the UNIFI trial, where baseline mucosal biopsies from patients treated with ustekinumab for moderate-to-severe UC underwent RNA profiling (Gene Expression Omnibus, GSE206285). Patients who achieved combined histo-endoscopic (mucosal) healing either with (disease clearance, “DC”) or without (mucosal healing, “MH only”) clinical remission at week 8 were included in subsequent analyses, along with non-IBD controls from this cohort (n=18). We compared gene expression and the enrichment of functional pathways using limma and GSEA (gene set enrichment analysis), respectively, between the two groups of responders and controls in R (v 4.2.3, Vienna). The Reactome database of pathway annotations was used. Gene signature enrichment was calculated by gene set variation analysis.

Results
Of the 54 patients who responded to ustekinumab, 15 experienced MH only and 39 had DC. Principal component analysis showed that these responders were distinct from controls but overlapped with each other (figure 1). For MH only compared to controls, there were 8375 differentially expressed genes (DEGs), of which 4936 were upregulated. There were 8778 DEGs between DC and controls, with 5331 upregulated. GSEA revealed that the DEGs in each comparison mainly represented pathways relating to the extracellular matrix (ECM), such as ECM degradation and collagen formation. There were no DEGs between MH only and DC but GSEA suggested that interleukin signalling and ECM organisation were upregulated in MH only. Interestingly, there was large heterogeneity in enrichment of the DEGs amongst all the responders. Similarly, there was wide variation in the enrichment of genes relating to the ECM.

Conclusion
Despite resolution of histo-endoscopic disease activity at week 8 in ustekinumab-treated UC patients, there was persistence of molecular inflammation, particularly ECM-related genes. However, the extent of this varied between patients; future work will examine if this explains why some eventually lose response whilst others maintain long-term remission. Ongoing inflammatory mechanisms may explain symptom persistence despite mucosal healing.

References
[1]Arijs I, De Hertogh G, Lemmens B, Van Lommel L, de Bruyn M, Vanhove W, Cleynen I, Machiels K, Ferrante M, Schuit F, Van Assche G, Rutgeerts P, Vermeire S. Effect of vedolizumab (anti-α4β7-integrin) therapy on histological healing and mucosal gene expression in patients with UC. Gut. 2018 Jan;67(1):43-52.