Abstract 4177: Th17 inhibition with interleukin 6 blockade decouples immunotoxicity from tumor immunity

Abstract Durable remission rates with immune checkpoint inhibitor (ICI) monotherapy remain low. Combination ICI therapies could overcome immune resistance but are associated with higher rates of immune-related adverse events (irAEs). To elucidate the underlying irAE immunobiology, we profiled human intestinal tissue, enterocolitis (irEC), and tumor tissue from ICI-treated patients using NanoString PanCancer Immune Panel (NanoPCIP) and multiplex immunohistochemistry (mIHC); hypotheses generated from these translational results for potential irAE treatments were tested in parallel preclinical mouse model studies. In 23 patients identified with both normal intestinal and irEC tissue, we found genes encoding interleukin-6 (IL-6), Th17 differentiating cytokine, and neutrophil and monocyte chemotactic molecules were the highest significantly upregulated in irEC compared to patient-matched normal intestine. Using NanoPCIP cell scoring (23 patients) and mIHC (27 patients), Th17 cells were significantly higher in irEC than Th1 cells. T-cell subsets were similar between anti-CTLA-4 based regimen versus anti-PD-1monotherapy induced irEC, except Th17 memory cells were significantly higher CTLA-4i-induced irEC. We compared the degree of differential gene expression in irEC (normal intestine versus irEC) to the differential expression in tumors (baseline versus on-treatment tumors). The genes highest upregulated in irEC (including Th17 differentiating cytokines IL-6 and IL-1B) were not upregulated in responding tumors from patients receiving ICI. NanoPCIP Th17 cell score was significantly more upregulated than Th1 cells and neutrophils more upregulated than CD8 T cells in the irEC analysis, but not in the responding tumor analysis where IL-12 and CD8 cell score was significantly upregualted . Based on these discoveries, we used C57BL/6 and Balb/c mouse strains to address whether the antitumor effect of ICIs can be enhanced by IL-6 blockade while also improving irAEs. We found that IL-6 blockade + ICI was associated with improved tumor control and a higher density of CD4/CD8 effector T-cells, with reduced Th17, macrophages, and MDSCs compared to ICI alone. Furthermore, in the experimental autoimmune encephalomyelitis (EAE) mouse model, the pathogenesis of which is well documented to be Th17 mediated (Robinson et al., 2014), we demonstrated that combined IL-6 blockade and ICI enhanced tumor rejection while simultaneously mitigating EAE symptoms versus ICI alone. Based on the totality of the basic science, translational, and clinical data we hypothesize that IL-6 blockade combined with ICIs could de-couple autoimmunity from antitumor immunity. We are currently conducting a prospective phase 2 trials of combination ipilimumab (3mg/kg) + Nivolumab (1mg/kg) + Tocilizumab in patients with metastatic melanoma, EGFR mutant NSCLC, and urothelial carcinoma ( NCT04940299). Citation Format: Daniel H. Johnson, Yared Hailemichael, Salah-Eddine Bentebibel, Noha Abdel-Wahab, Sungnam Cho, Wai C. Foo, Khalida Wani, Stephanie S. Watowich, Suhendan Ekmekcioglu, Adi Diab. Th17 inhibition with interleukin 6 blockade decouples immunotoxicity from tumor immunity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4177.