P0084The IL-27/IFNg/JAK1 axis is functionally important in immune checkpoint inhibitor- induced colitis

Abstract Background Immune checkpoint inhibitors (CPI) have transformed cancer outcomes but trigger CPI-colitis (CPI-c) in up to 45%, leading to morbidity and CPI discontinuation. Current immunosuppressive treatments incur significant side effects and may impede CPI efficacy, highlighting the need for new therapies. Methods Molecular profiling (colonic biopsy RNA-sequencing and longitudinal serum proteome profiling) of CPI-c patients and controls (including healthy controls and UC patients) was performed. Gene expression, pathway level (GSEA) and upstream regulators were analysed. Publicly available single-cell sequencing datasets from CPI-c and CPI (no colitis)1 were also analysed to infer cell–cell interactions. Functional testing of mechanistically relevant candidate therapeutic targets was evaluated in 2 mouse models of disease and in CPI-c derived human organoid systems. Results Gene expression profiling of colonic biopsies highlighted overactivity of multiple cytokines in CPI-c patients, including IFNg, IL-27, IL1b, IL15 and IL18. IFNg-responsive transcripts (CXCL9, CXCL10, GZMB and STAT1) and IL27-related genes IL27RA, EBI3) were among the most upregulated transcripts. IFNg-signalling, JAK-STAT signalling and TNF signalling were among the most activated biological pathways. Analysis of a single cell RNA-seq dataset identified distinct IFNg and IL27 mediated interactions between TH17+PD1+ T-cells, epithelial cells, and inflammatory enterocytes; and engagement of IL27 signalling from mononuclear phagocytes to CD4+ T-cells and stromal cells. Serum IL-27 levels were significantly elevated in CPI-c patients. IFNg-responsive genes, such as CXCL9, CXCL10, were potently induced at transcript and protein level in our patient derived organoid system in response to recombinant IFNg in a JAK1 dependent manner when comparing healthy controls to CPI-c organoids. In our published in vivo animal model using wildtype mice treated with CPI-c2, blockade of IL27 or JAK1, using Upadacitinib, significantly attenuated disease severity. The same effect was observed in a humanised CTLA-4/PD-1 CPI-c mouse model. Strikingly, patients with severe, multidrug-refractory CPI-c (n = 10) treated with Upadacitinib achieved rapid symptom resolution within days, marked reductions in faecal calprotectin (median 3861→117 µg/g, p0.01), and complete mucosal healing (median UCEIS 5→0, p0.0001), with sustained clinical benefit at one year. Conclusion CPI-c is characterised by marked upregulation of an IL27/IFNg axis that is functionally important in preclinical and organoid models and is dependent on JAK1 signalling. Moreover, selective JAK1 blockade with Upadacitinib rapidly rescued treatment refractory patients and looks to be a highly promising treatment option. References: 1- Gupta T, Antanaviciute A, Lee CH, et al. Tracking in situ checkpoint inhibitor–bound target T cells in patients with checkpoint-induced colitis. Cancer Cell. 2024;42(5):797-814. 2- Lo JW, Cozzetto D, Alexander JL, et al. Immune checkpoint inhibitor–induced colitis is mediated by polyfunctional lymphocytes and is dependent on an IL-23/IFN-γ axis. Nat Commun. 2023;14(1):6719. Conflict of interest: Ibraheim, Hajir: No conflict of interest Lo, Jonathan: No conflict of interest Bohar, Balazs: No conflict of interest Olbei, Marton: No conflict of interest Cross, Emilia: No conflict of interest Cozzetto, Domenico: No conflict of interest Korcsmaros, Tamas: Grant: Unilever, Roche Powell, Nick: Grant: Takeda, BMS, Pfizer, Astra-Zeneca Personal Fees: Abbvie, Abivax, Allergan, Astra-Zeneca, Bristol-Myers Squibb, Celgene, Celltrion, Dr Falk Pharma UK Ltd, Ferring, Galapagos, GSK, Janssen, MSD, Roche, Pfizer, Sobi, Takeda, Tillotts