A Chimeric GM-CSF/IL18 Receptor to Sustain CAR T-cell Function

Abstract The inability of chimeric antigen receptor (CAR) T cells to sustain their effector function after repeated exposure to tumor cells is a major obstacle to their success in patients with solid tumors. To overcome this limitation, we designed a novel chimeric cytokine receptor to create an autocrine loop that links activation-dependent GM-CSF production by CAR T cells to IL18 receptor signaling (GM18). Expression of GM18 in CAR T cells enhanced their effector function in an antigen- and activation-dependent manner. In repeat stimulation assays, which mimic chronic antigen exposure, CAR.GM18 T cells had a significantly greater ability to expand and produce cytokines in comparison with their unmodified counterparts targeting EPHA2 or HER2. In vivo, CAR.GM18 T cells induced tumor regression at cell doses at which standard CAR T cells were ineffective in two solid tumor xenograft models. Thus, our study highlights the potential of hijacking cytokines that are physiologically secreted by T cells to bolster their antitumor activity. Significance: We designed a chimeric cytokine receptor (GM18) that links CAR T-cell activation to MYD88 signaling. GM18 endows CAR T cells with sustained effector function in the setting of chronic antigen exposure, resulting in potent antitumor activity in preclinical solid tumor models. This article is highlighted in the In This Issue feature, p. 1601