Abstract PO083: Treatment of CEA-positive solid tumors with anti-CEA chimeric antigen receptor T-cells in CEA transgenic mice

Chimeric antigen receptors (CARs) combine specificity of antibody to target antigen on cancer cells with the potent cytotoxic activity of T-cells without the need for MHC recognition. Chimeric antigen receptor (CAR) T-cells that were designed to express the single chain variable fragment binding domain of human anti-CEA antibody BW431/26 on mouse splenocytes were able to reduce CEA-expressing pancreatic adenocarcinoma tumor in CEA-transgenic (CEAtg) mice without significant off-target effects (Chmielewski et al., 2012). In this study, an anti-CEA CAR construct derived from murine anti-CEA antibody (T84.66) expressed on human T-cells targeted CEA+ colon carcinoma cells (LS174T/CEA and MC38CEA) with high specificity in vitro. When co-incubated with CEA-positive or CEA-negative mouse cancer cells, anti-CEA CAR expressed on mouse T-cells also specifically targeted CEA-positive cancer cells in vitro. Compared to mock T-cells control, anti-CEA CAR T-cells injected intravenously delayed subcutaneous MC38CEA tumor growth in CEA-transgenic mice (CEAtg). Lymphodepletion via cyclophosphamide injected before anti-CEA T-cells injection further delayed subcutaneous MC38CEA tumor growth and delayed orthotopic CEA+ breast carcinoma (E0771CEA) tumor growth in CEAtg mice. To improve the therapeutic potential of anti-CEA CAR T-cells, IL2 conjugated to humanized anti-CEA antibody (M5A-IL2, ICK) was interperitoneally injected after anti-CEA CAR T-cells into lymphodepleted CEAtg mice. A single injection of ICK after anti-CEA CAR T-cells delayed subcutaneous MC38CEA tumor growth even further. Two injections of ICK after anti-CEA T-cells delayed orthotopic E0771CEA tumor growth. Four injections of ICK after anti-CEA CAR T-cells eradicated subcutaneous MC38CEA tumors. These data show the therapeutic potential of anti-CEA CAR T-cells to target CEA-positive tumors. Citation Format: Seung Cha, Paul Yazaki, Christine Brown, John Shively. Treatment of CEA-positive solid tumors with anti-CEA chimeric antigen receptor T-cells in CEA transgenic mice [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2020 Oct 19-20. Philadelphia (PA): AACR; Cancer Immunol Res 2021;9(2 Suppl):Abstract nr PO083.