Abstract
2539 Background: On-target off-tumor toxicity is a significant concern in Chimeric Antigen Receptor (CAR)-T therapies, especially for solid tumors, leading to adverse effects on normal tissues and impacting on treatment efficacy. To address this challenge, a modified form of CAR-T cells named Peri Cruiser CAR-T has been developed by using miRNA technology to knock down three adhesion genes that mediate T cell transendothelial migration to normal tissues, aiming to block the extravasation of CAR-T cells so that the on-target off-tumor toxicity could be prevented without compromising anti-tumor efficacy. In this study, we provided a proof of concept by using the epithelial cell adhesion molecule (EpCAM) as a targeting tumor-associated antigen (TAA). Methods: An miRNA cassette was incorporated into the vectors of anti-human or mouse EpCAM CARs. The knockdown efficiency, endothelial adhesion efficiency, effector functions and memory phenotypes in vitro were evaluated. To determine the toxicity in vivo, the anti-mouse EpCAM CAR-T cells were administered to non-tumor bearing NSG mice, and the body weight and T cell infiltration in normal tissues was evaluated. Anti-tumor efficacy was also evaluated in NSG mice with subcutaneous and metastatic tumor models by anti-human EpCAM CAR-T cells. Results: Our Peri Cruiser CAR-T platform was capable to effectively downregulate the target genes by 10 folds. The knockdown is stable after extended culture and antigen engagement in vitro. This knockdown of targeted genes significantly decreased T cell adhesion to endothelial cells and corresponding ligands, but did not affect T cell activation or effector functions such as cytotoxicity and IFN gamma release. Surprisingly, lowering the levels of these adhesion molecules improved the memory phenotypes of CAR-T cells as indicated by increased portion of CCR7+CD45RO+ cells. In vivo studies showed that conventional EpCAM CAR-T-injected mice experienced severe weight loss and all had to be sacrificed before day 8, the IHC staining of CD3 revealing massive infiltration of T cells in lung, liver, and kidney. However, the incorporation of the miRNA cassette prevented T cell infiltration in normal tissues, reversed the toxicity, and ensured the survival of all mice. The anti-tumor efficacy of these T cells was evaluated in vivo and found to decrease metastasis as effectively as the conventional CAR-T cells in a metastasis model of HCT116-Luc, although there was a slightly but not significantly decreased efficacy in a subcutaneous model of HCT116. Conclusions: The Peri Cruiser CAR-T platform can significantly improve the safety of CAR-T cells without compromising their efficacy to eliminate tumor cells in primary site and metastasis. This technology opens another avenue to safely target a variety of other TAA by CAR-T even when there is the potential of on-target off-tumor toxicity in normal tissues for those antigens.
Published Version
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