Abstract 6189: Development of an anti hepatocellular carcinoma CAR T strategy targeting PDL1

[Purpose] Immunosuppressive tumor microenvironment (TME) is the major hurdle to cancer immunotherapy. Advanced hepatocellular carcinoma (aHCC) is one of the representative cold tumors with immunosuppressive TME and presents obvious correlation between immune check point expression, such as programmed cell death ligand 1 (PD-L1), and poorer prognosis. In aHCC patients, cancer cells and stellate cells in TME appeared to express high level of PD-L1, which should suppress activities of antitumor immune cells. In this context, the combination of PD-1/PD-L1 inhibitors and other therapeutic modalities are tried to treat aHCC. The chimeric antigen receptor (CAR) T cell therapy is a potent way of eradicating cells expressing targetable antigens. Removal of PD-L1 expressing cells in the aHCC TME will improve the clinical outcomes of current therapies against aHCC. In the present study, we developed an autologous anti-PD-L1 CAR T strategy and show high efficacy of tumor suppression using an HCC xenograft model. [Result] We constructed second generation CAR lentiviral vector expressing an unique anti-PD-L1 scFv manifesting moderated affinity. The scFv was specifically generated by phage display technique using human B cell-derived naïve cDNA library, which targets PD-L1 with intermediate affinity in solid tumor TME. As the secondary signaling motif, CD28 was chosen and tested along with CD3 zeta chain. The effector CAR T, named VPC1, cells specifically recognized PD-L1 expressing HCC cells and exhibited rapid and robust cytotoxic activity in 2D and 3D culture experiments. In an HCC xenograft NSG mouse model, VPC1 CAR T cells significantly suppressed the tumor growth. More importantly, VPC-1-treated animals have well tolerated the CAR T therapy with no significant adverse manifestations during one month observation period and exhibited gradual weight gains since 3 days after CAR T cell injection. [Conclusion] We hereby report that a new autologous PD-L1 CAR-T therapeutic is capable of eradicating solid tumors expressing PD-L1, which would significantly potentiate efficacies of current conventional and immunotherapeutic strategies. Citation Format: Kyung-Sik Lee, Hye-Seong Park, Guk-Yeol Park, Gi-Chan Lee, Eun-Ji Choi, Jae-in Yu, Seung-Joo Yang, Mihwa Kim, Yoonjoo Choi, Je-Jung Lee, Joon Haeng Rhee, Bum Chan Park, Jae Eun Park. Development of an anti hepatocellular carcinoma CAR T strategy targeting PDL1 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6189.