P0128 IL-27 signalling, but not IL-1B, is functionally relevant in the pathophysiology of immune checkpoint inhibitor induced colitis

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Abstract Background Immune checkpoint inhibitors (CPI) augment T-cell responses to tumour cells and have transformed treatment paradigms in cancer. However, CPI frequently trigger autoimmune like events, including potentially life-threatening colitis. Current immunosuppressive treatments for CPI- colitis (CPI-c) incur significant side effects and may even reduce CPI efficacy. New treatments are urgently needed. Methods Changes at gene level, pathway level (GSEA) and predicted upstream regulators (Ingenuity Pathway Analysis-IPA), and enrichment scores (Gene Set Variation Analysis-GSVA) were investigated in colonic biopsies (RNA-sequencing) from patients with CPI-c (n=12), CPI (no colitis) (n=6), healthy controls (n=13) and ulcerative colitis (UC) (n=12). Potentially relevant pathways were functionally tested in preclinical disease models. CPI-c was induced in mice transplanted with a pro-inflammatory microbiota and administered anti-PD-1 and anti-CTLA-4 intraperitoneally (i.p). Anti-IL1R (anakinra), MCC950 (inflammasome inhibitor) and anti-IL27 were administered i.p. Colonic leukocytes were extracted to interrogate myeloid and lymphocyte compartments by flow cytometry. Whole colon segments were processed for histology. Results In CPI-c patients, IL-1B was the top differentially expressed cytokine at gene level with interleukin-1 signalling significantly enriched at pathway level. IPA also identified IL-1B and IL-27 as predicted upstream activators. Interestingly, in vivo blockade of IL-1B, or the inflammasome (MCC950), had no impact on colitis. Administration of IL-27-neutralising antibodies at the onset of CPI-colitis in mice, reduced disease susceptibility and improved histological colitis scores. This was associated with decreased infiltration of colonic lamina propria neutrophils, Ly6C+ inflammatory monocytes and the number of CD8+ IFNg+ T-cells. Conversely, administering neutralising anti-IL27 during established CPI-colitis did not ameliorate disease and was linked to an enhanced CD4+ effector response characterised by heightened production of TNFa and IFNg. Further analysis of colonic biopsies of CPI-c patients confirmed enrichment of IL27-responsive genes which we localised to CD8+ resident memory and CD8+ cytotoxic cells in single cell RNA-seq analyses. Additionally, serum IL-27 levels were significantly elevated in CPI-c patients. Conclusion IL-1B signalling was shown to be dispensable to disease in mice. However, IL-27 signalling has a context specific role, serving as a functionally important activator of innate immune responses, while inhibiting later phases of acquired immunity via suppressing cytotoxic lymphocyte responses. Targeting IL-27 presents an attractive therapeutic approach for CPI-c given its potential tumourogenic effects.