Abstract
CAR T cell efficacy in solid tumors is limited due in part to the immunosuppressive TME. To improve anti-tumor responses, we hypothesized that enabling CAR T cells to secrete bifunctional fusion proteins consisting of a cytokine modifier (e.g., TGFβtrap, IL15, or IL12) combined with an immune checkpoint inhibitor (e.g., αPDL1) will provide tumor localized immunomodulation to improve CAR T cell functionality. To that end, we engineered CAR T cells to secrete TGFβtrap, IL15, or IL12 molecules fused to αPDL1 scFv, and assessed in vitro functionality and in vivo safety and efficacy in prostate and ovarian cancer models. CAR T cells engineered with αPDL1-IL12 were superior in safety and efficacy compared to CAR T cells alone and to those engineered with αPDL1 fused with TGFβtrap or IL15. Further, αPDL1-IL12 engineered CAR T cells improved T cell trafficking and tumor infiltration, localized IFNγ production, TME modulation, and anti-tumor responses, with reduced systemic inflammation-associated toxicities. We believe our αPDL1-IL12 engineering strategy presents an opportunity to improve CAR T cell clinical efficacy and safety across multiple solid tumor types.