Abstract 6335: Armoring CAR-T therapy with PD-1 blockade: a powerful strategy for enhancing anti-tumor effects in pancreatic cancer

Abstract Chimeric antigen receptor-modified T cells (CAR-T) have been widely applied in the treatment of hematological malignancies and are currently under investigation for their potential effectiveness against solid tumors. Nevertheless, the effectiveness of CAR-T in treating solid tumors remains unsatisfactory due to a range of factors, including CAR-T cell infiltration and heterogeneity. The efficacy of CAR-T therapy is substantially influenced by the tumor microenvironment. This is particularly evident when PD-L1 is activated through CAR-T, leading to the inhibition of CAR-T cell activity via the PD-1 pathway. In this study, we engineered a CAR-T therapy that targets mesothelin and concurrently expresses a membrane-bound PD-1 receptor. This design blocks the PD-1 on CAR-T cells, effectively counteracting the suppression of CAR-T function mediated by PD-L1. We observed a substantial upregulation of PD-L1 on AsPC-1 tumor cells after 4 hours of IFN-γ stimulation in vitro. CAR-T cells engineered to co-express PD-1 antibody (aMSLN-28BBZ-mPD-1) exhibited similar short-term cytotoxicity and cytokine secretion profiles to those of the traditional third-generation CAR-T (aMSLN-28BBZ). Notably, aMSLN-28BBZ-mPD-1 displayed significantly improved long-term target cell killing. Furthermore, in an in vivo model of pancreatic cancer, aMSLN-28BBZ-mPD-1 demonstrated enhanced anti-tumor activity when compared to the traditional aMSLN-28BBZ, as supported by RNAscope analysis and immunofluorescence assays of tumor tissues. These analyses revealed a marked upregulation of PD-L1 expression and enhanced CAR-T cell infiltration in the aMSLN-28BBZ-mPD-1 treatment group. In summary, our study demonstrates that co-expression of a membrane-bound PD-1 antibody overcomes PD-L1 mediated CAR-T suppression, as observed in both in vitro and in vivo. This innovative strategy underscores its therapeutic potential and value in treating solid tumors. Keywords: CAR-T, PD-1, Tumor Microenvironment, Pancreatic Cancer Citation Format: Zhixiang Zhang, Jingwei Huang, Zhifeng Zhao, Xiangyi Wang, Cnhui he, Sen Yang, Qingyang Gu. Armoring CAR-T therapy with PD-1 blockade: a powerful strategy for enhancing anti-tumor effects in pancreatic cancer abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 6335.