CAR-T cells secreting BiTEs circumvent antigen escape without detectable toxicity.

Chimeric antigen receptor (CAR)-T-cell therapy for solid tumors is limited due to heterogeneous target antigen expression and outgrowth of tumors lacking the antigen targeted by CAR-T cells directed against single antigens. Here， we developed a bicistronic construct to drive expression of a CAR specific for EGFRvIII， a glioblastoma-specific tumor antigen， and a bispecific T-cell engager (BiTE) against EGFR， an antigen frequently overexpressed in glioblastoma but also expressed in normal tissues. CART.BiTE cells secreted EGFR-specific BiTEs that redirect CAR-T cells and recruit untransduced bystander T cells against wild-type EGFR. EGFRvIII-specific CAR-T cells were unable to completely treat tumors with heterogenous EGFRvIII expression， leading to outgrowth of EGFRvIII-negative， EGFR-positive glioblastoma. However， CART.BiTE cells eliminated heterogenous tumors in mouse models of glioblastoma. BiTE-EGFR was locally effective but was not detected systemically after intracranial delivery of CART.BiTE cells. Unlike EGFR-specific CAR-T cells， CART.BiTE cells did not result in toxicity against human skin grafts in vivo.