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. [Display omitted] •ROR1-specific CAR-T cells induce lethal toxicity after cytotoxic pre-conditioning•Toxicity is due to attack of ROR1+ stroma needed for recovery from cytotoxic stress•SynNotch receptors restrict CAR activity to ROR1+ tumors expressing synNotch ligands•SynNotch receptors rescue toxicity only if tumor and normal cells are separated Srivastava et al. show that ROR1-targeted CAR-T cells expressing synthetic Notch receptors for EpCAM or B7-H3, which are expressed on tumor cells but not stromal cells, induce tumor regression without toxicity when ROR1+ tumor cells and ROR1+ normal cells are segregated, but not when they are co-localized.