Data from Mesothelin CAR T Cells Secreting Anti-FAP/Anti-CD3 Molecules Efficiently Target Pancreatic Adenocarcinoma and its Stroma

Abstract

<div>AbstractPurpose:<p>Targeting solid tumors with chimeric antigen receptor (CAR) T cells remains challenging due to heterogenous target antigen expression, antigen escape, and the immunosuppressive tumor microenvironment (TME). Pancreatic cancer is characterized by a thick stroma generated by cancer-associated fibroblasts (CAF), which may contribute to the limited efficacy of mesothelin-directed CAR T cells in early-phase clinical trials. To provide a more favorable TME for CAR T cells to target pancreatic ductal adenocarcinoma (PDAC), we generated T cells with an antimesothelin CAR and a secreted T-cell–engaging molecule (TEAM) that targets CAF through fibroblast activation protein (FAP) and engages T cells through CD3 (termed meso<sup>FAP</sup> CAR-TEAM cells).</p>Experimental Design:<p>Using a suite of <i>in vitro</i>, <i>in vivo</i>, and <i>ex vivo</i> patient-derived models containing cancer cells and CAF, we examined the ability of meso<sup>FAP</sup> CAR-TEAM cells to target PDAC cells and CAF within the TME. We developed and used patient-derived <i>ex vivo</i> models, including patient-derived organoids with patient-matched CAF and patient-derived organotypic tumor spheroids.</p>Results:<p>We demonstrated specific and significant binding of the TEAM to its respective antigens (CD3 and FAP) when released from mesothelin-targeting CAR T cells, leading to T-cell activation and cytotoxicity of the target cell. Meso<sup>FAP</sup> CAR-TEAM cells were superior in eliminating PDAC and CAF compared with T cells engineered to target either antigen alone in our <i>ex vivo</i> patient-derived models and in mouse models of PDAC with primary or metastatic liver tumors.</p>Conclusions:<p>CAR-TEAM cells enable modification of tumor stroma, leading to increased elimination of PDAC tumors. This approach represents a promising treatment option for pancreatic cancer.</p></div>