Liu et al. (2018) reported the transduction of an inducible caspase 9-based (iC9) suicide gene into CD19-CAR/IL-15-expressing NK cells isolated from cord blood (iC9/CAR.19/IL-15 CB-NK). IL-15 production increaseds significantly when challenged with CD19+ chronic lymphocytic leukemia (CLL) targets with minimal secretion in the absence of CD19+ targets. Administration of dimerizer (AP1903) in vivo successfully triggers the suicide response to reduce CAR-expressing NK cells in PB (98%→11%) and tissues within 3 days. This evidence concerns the gene CASP9 and B-cell chronic lymphocytic leukemia.