Abstract LB091: Design, characterization and preclinical validation of a combinatorial CAR-based immunotherapy against colorectal cancer with HER2 amplification
Authors: Cortese Marco , Torchiaro Erica , Invrea Federica , Petti Consalvo , D'Andrea Alice , Arena Sabrina , Medico Enzo 
Published: April 2023

Abstract
Adoptive immunotherapy based on chimeric antigen receptor (CAR)-T cells has led to successful treatment of some hematological malignancies, but it remains extremely challenging for solid tumors, mostly because of “on-target off-tumor” toxicity, as observed in the case of anti-HER2 CAR-T treatment of colorectal cancer (CRC) with HER2 amplification. To enable adoptive immunotherapy against HER2-amplified CRC, we therefore considered a combinatorial strategy based on the synNotch-based artificial regulatory network. A synthetic Notch receptor was employed in which the extracellular domain is an anti-HER2 scFv and the intracellular domain contains the GAL4-VP64 artificial transcription factor. Engagement of the anti-HER2 domain by target cells drives GAL4-VP64 cleavage and translocation to the nucleus, where it drives expression of a CAR under a GAL4-responsive promoter. In this way, only cells co-expressing both HER2 and the CAR target are killed. As a CRC-specific CAR target we selected CEA, product of the CEACAM5 gene. CEA expression is restricted to the digestive tract and is increased in cancer. For the generation of HER2-synNotch CEA-CAR effectors, we chose the natural killer cell line NK-92 and transduced it with two lentiviral vectors, encoding respectively the HER2 synNotch and the second-generation anti-CEA CAR with CD28 costimulatory domain. Transduced cells were repeatedly sorted in the ON and OFF state to select those with the best CAR induction after synNotch engagement; cloning of sorted cells led to identification of an optimally responsive clone (clone 5F), showing no basal CEA-CAR expression and massive induction in the presence of HER2-overexpressing cancer cells. In vitro, the 5F clone displayed selective cytotoxicity against HER2++/CEA++ CRC cells, with minimal killing activity against HER2++/CEA- breast cancer cells, or against CRC cells expressing CEA but without HER2 amplification. In vitro 3D models highlighted better recruitment and infiltration by NK-92 clone 5F respect to NK-92 WT cells, only of HER2++ organoids. In vivo, the clone 5F significantly impaired tumor growth in two different HER2++ CRC models. The observed selective efficacy both in vitro and in vivo of the HER2-synNotch/CEA-CAR approach opens a perspective for possible clinical applications in cases of HER2-amplified CRC displaying primary or secondary resistance to HER2/EGFR blockade.
Citation Format: Marco Cortese, Erica Torchiaro, Federica Invrea, Consalvo Petti, Alice D'Andrea, Sabrina Arena, Enzo Medico. Design, characterization and preclinical validation of a combinatorial CAR-based immunotherapy against colorectal cancer with HER2 amplification [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB091.