Evaluation of B7-H3-CAR T cells expressing leucine zipper-based cytokine receptors in immunocompetent mouse models 4339

Abstract Description Chimeric antigen receptor (CAR) T cell therapy shows promise in hematological malignancies but faces challenges in solid tumors. One of the challenges is their reduced functionality in the immunosuppressive tumor microenvironment. To overcome this, we developed a leucine-zipper-based cytokine receptor (ZipR) platform to constitutively activate cytokine signaling pathways and have demonstrated its benefits in NSG mouse models (Bell et al, Nat Biomed Eng, 2023). We now propose to evaluate ZipR-expressing B7-H3-CAR T cells in immunocompetent osteosarcoma (OS) mouse models, focusing on IL-7- based (Zip7R) and IL-18-based ZipR (Zip18R) which respectively activates JAK/STAT5 and MyD88 pathway. We used retroviral vectors encoding i) a mB7-H3-CAR with a CD28z endodomain and/or ii) a Zip7R or Zip18R to generate CAR.Zip7R, CAR.Zip18R, and control cells from activated murine T cells. Data confirmed the cytokine pathways were activated in ZipR-expressing T cells without inducing unspecific killing of OS cells. Its expression in CAR T cells did not interfere with CAR function nor induce antigen-independent killing. In repeat stimulation assays, the ability of CAR.Zip7R T cells to recursively kill tumor cells and expand was significantly increased in comparison to CAR T cells. We are characterizing CAR.Zip7R and CAR.Zip18R T cells in greater detail in vitro, and in vivo studies are in progress. The goal of this project is to select an optimal ZipR for early-phase clinical development. Funding Sources ALSAC Topic Categories Tumor Immunology: Checkpoints, Prevention, and Treatment (TIPT)