IL1R1 blockade augments CD40 agonist mediated immunity in pancreatic cancer.

Pancreatic ductal adenocarcinoma (PDAC) has a poor survival rate and limited treatments. Agonistic CD40 antibodies are promising, but clinical trials have shown only modest efficacy and significant hepatotoxicity. We previously reported that IL-1 pathway blockade enhances CD40 agonist efficacy against melanoma by depleting polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs; CD11b+Ly6C+Ly6G+). Because PMN-MDSCs also cause liver toxicity, we investigated the impact of IL-1R1 blockade on the efficacy and toxicity of agonistic CD40 antibody therapy in PDAC. Agonistic CD40 antibody therapy induced immune activation and significantly prolonged survival in orthotopic PDAC-bearing mice. The combination of an agonistic CD40 antibody and IL-1R1 blockade upregulated multiple immune-related pathways and enhanced innate and adaptive responses. However, it did not further improve CD40 efficacy or reduce liver toxicity. The efficacy of the CD40 agonist was partially dependent on CD8⁺ T cells. Our findings underscore the complex role of IL-1 signaling in modulating immune responses in PDAC and caution against pursuing IL-1R1 blockade, either as monotherapy or combined with agonistic CD40 antibodies, in clinical trials for PDAC.