Logic-Gated ROR1 Chimeric Antigen Receptor Expression Rescues T Cell-Mediated Toxicity to Normal Tissues and Enables Selective Tumor Targeting.

Many potential targets for CAR-T cells in solid tumors are expressed in some normal tissues, raising concern for off-tumor toxicity. Following lymphodepletion, CAR-T cells targeting the tumor-associated antigen ROR1 lysed tumors in mice but induced lethal bone marrow failure due to recognition of ROR1 stromal cells. To improve selectivity, we engineered T cells with synthetic Notch (synNotch) receptors specific for EpCAM or B7-H3, which are expressed on ROR1 tumor cells but not ROR1 stromal cells. SynNotch receptors induced ROR1 CAR expression selectively within the tumor, resulting in tumor regression without toxicity when tumor cells were segregated from, but not when co-localized with, normal ROR1 cells. This strategy, thus, permits safe targeting of tumors that are sufficiently separated from normal cells.