A novel preclinical tool to unlock the potential of IL-18 in cancer immunotherapy: genO-hIL-18-hIL-18R mice

Interleukin-18 (IL-18) has emerged as a promising immunomodulatory cytokine in immuno-oncology due to its ability to enhance both innate and adaptive immune responses. It promotes IFN-gamma production by T and NK cells, thereby amplifying anti-tumor immunity, especially when combined with checkpoint inhibitors or engineered pro-drugs to resist natural inhibition by IL-18BP. Recent studies suggest that IL-18-based therapies may overcome resistance mechanisms in "cold" tumors, making them more responsive to immunotherapies. Humanized mouse models expressing human IL-18R are essential to accurately assess efficacy and guide development of human-directed IL-18-based therapies. Therefore, we describe here a new IL-18-IL-18R double humanized mouse model to assess the efficacy of therapeutics targeting the IL-18/IL-18R axis. The generated genO-hIL-18-hIL18-R mice show expression of human IL-18Ra on NK, monocytes and T cells under steady state conditions. Functional validation of genO-hIL-18/hIL18-R mice demonstrates robust in vitro IFN-gamma production by splenocytes upon stimulation with exogenous human IL-18, suggesting that hIL-18R is functional. Similarly to mouse IL-18 in wild-type mice, human IL-18 is not detected in naïve mice. However, its secretion can be induced in vivo by treatment with lipopolysaccharide (LPS), which also triggers IFN-gamma secretion. Importantly, humanization of the IL-18/IL-18Ra axis does not alter the physiological distribution of immune cells, as immune-profiling reveals comparable frequencies of main immune cells between genO-hIL-8-hIL-18R mice and wild-type control mice. Finally, the effectiveness of the genO-hIL-18-hIL-18R model in supporting drug efficacy was demonstrated by evaluating an engineered IL-18. Splenocytes from genO-hIL-18-hIL-18R mice treated with this engineered IL-18 exhibited enhanced cell proliferation and increased IFN-gamma production compared to those treated with an inactive IL-18. Altogether, these data support the suitability of the genO-hIL-18-hIL-18R mice for assessment of new therapies targeting this axis.