Solid tumour CAR-T cells engineered with fusion proteins targeting PD-L1 for localized IL-12 delivery

Chimeric antigen receptor (CAR)-T cell efficacy in solid tumours is limited due in part to the immunosuppressive tumour microenvironment (TME). To improve antitumour responses, we hypothesized that enabling CAR-T cells to secrete bifunctional fusion proteins consisting of a cytokine modifier such as TGFβ^trap, IL-15 or IL-12, combined with an immune checkpoint inhibitor such as αPD-L1, would provide tumour-localized immunomodulation to improve CAR-T cell functionality. Here we engineer CAR-T cells to secrete TGFβ^trap, IL-15 or IL-12 molecules fused to αPD-L1 scFv and assess in vitro functionality and in vivo safety and efficacy in prostate and ovarian cancer models. CAR-T cells engineered with αPD-L1-IL-12 are superior in safety and efficacy compared with CAR-T cells alone and those engineered with αPD-L1 fused with TGFβ^trap or IL-15. Further, αPD-L1-IL-12 engineered CAR-T cells improve T cell trafficking and tumour infiltration, and localize IFNγ production, TME modulation and antitumour responses, with reduced systemic inflammation-associated toxicities. We believe our αPD-L1-IL-12 engineering strategy presents an opportunity to improve CAR-T cell clinical efficacy and safety across multiple solid tumour types.