CASP9 and neoplasm: These include but are not restricted to the SUPRA CAR (with tunable availability and affinity) [54], CAR T cells using the synNotch receptor (that can induce transcription of CAR expression to target a second antigen) [55], bispecific CARs (can target two tumor antigens interchangeably) [56] and suicide CAR T cells (such as those using the inducible caspase 9 system, whereby small molecules can activate apoptosis independent of CAR activation) [57].