CAR T cells secreting anti-EpCAM bispecific T cell engagers overcome tumor heterogeneity in targeting epithelial-originated carcinomas.

Chimeric antigen receptor (CAR) T cell therapy to treat solid tumors has seen limited success, partly due to tumor heterogeneity and antigen escape. These barriers remain major challenges, as heterogeneous tumors often consist of diverse populations of cancer cells, which can downregulate or lose the targeted antigens following the treatment, thereby evading CAR T cell recognition and killing. To address this challenge, we engineered CAR T cells to secrete bispecific T cell engagers (BTCEs) targeting epithelial cell adhesion molecule (EpCAM). EpCAM is a tumor-associated antigen widely expressed in epithelial-derived tumors but often considered "undruggable" by conventional targeted therapies due to its expression in normal epithelial cells. Secretion of the anti-EpCAM BTCEs by CAR T cells localizes BTCEs to the tumor site, preventing antigen escape while limiting systemic toxicity. This tactic successfully uses CAR T cells as carriers to restrict BTCE activity within the tumor microenvironment. Here, we show that in preclinical models, glypican-3 (GPC3)-, Delta-like ligand 3 (DLL3)-, and human epidermal growth factor receptor 2 (HER2)-targeted CARs that secrete anti-EpCAM BTCEs can completely eradicate heterogeneous tumors of epithelial origins and stop antigen escape. Our results highlight the versatility of this technology across various epithelia-originated carcinomas and imply that this strategy has significant translational potential to enhance solid tumor immunotherapy.