TRAC and neoplasm: The precise integration of CARs at the TRAC locus has previously been shown to enhance tumor cell killing while conferring notable advantages over viral gene delivery (e.g., retrovirus, lentivirus): it ensures most T cells are monoclonal (only a single and unique CAR); it leads to transgene expression that is more consistent across cells and physiologically regulated, and it knocks out the endogenous TCR to avoid confounding effects20.