Abstract 899: Deciphering the benefits of variable delivery routes and molecular armoring to enhance efficacy of MUC1-CAR T-cells in targeting triple-negative breast cancer

Abstract

Abstract As immune-therapies continue to develop for solid tumors, the tumor microenviroment (TME) poses many challenges that CAR T-cells need to overcome for efficient tumor cell clearance. Tumor immune evasion mechanisms, presence of immunosuppressive factors and cellular resistance to tumor infiltration are key mechanisms that the TME uses to reduce efficacy of T-cells against the tumor. Therapeutic options for triple negative breast cancer (TNBC) remain limited to date despite it being the most aggressive subtype of breast cancers and carrying the poorest prognosis. Tumor-associated MUC1 antigen is overexpressed in a large number of TNBC patients offering an effective discriminatory target for CAR T-cell therapy. Here, we present innovative strategies exploring alternative delivery routes and purposeful armoring of CAR T-cells to boost efficiency while preserving safety. To maintain anti-tumor CAR T-cell cytotoxic and proliferation in the hostile TME of solid tumors, we developed state-of-the-art multiplexed gene editing using high precision TALEN® technology. With that aim, we armored allogeneic CAR T-cells with specific attributes to release immune inflammatory cytokines and protect from inhibitory effects of the TGFB1 and PD1 pathways. A combination of strategies using allogeneic CAR T-cells with diverse attributes were evaluated against TNBC tumors in various in vivo pre-clinical models. Local CAR T-delivery resulted in effective control of tumor growth and robust antigen specific recognition. Furthermore, we assessed how the delivery route contributes to CAR-T cell distribution. CAR T-cell activity could also be increased systemically upon tumor-specific release of immunostimulatory cytokines without compromising safety. Our results demonstrate not only superior activity of armored MUC1-CAR T-cells resulting in tumor clearance but also in the recovery of normal glands. Thus, innovative strategies can be used to allow CAR T-cell efficiency in the hostile tumor microenvironment while preserving safety. Overall, our pre-clinical results underline the capability of armored allogenic MUC1-CAR T-cells to excel in the immune suppressive tumor micro-environment, suggesting that allogenic MUC1-CAR T-cell therapy could be an effective option in treating relapsed/refractory TNBC patients with limited therapeutic options. Citation Format: Piril Erler, Hana Cho, Jordan Skinner, Laurent Poirot, Beatriz Aranda-Orgilles. Deciphering the benefits of variable delivery routes and molecular armoring to enhance efficacy of MUC1-CAR T-cells in targeting triple-negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 899.