In vivo, treatment with the PI3Kδ inhibitor (idelalisib) enhances the proliferation of CAR-T cells, which are characterized by an expanded memory T cell compartment, longer survival, longer duration of tumor control [117], and increased anti-tumor activities against CD19+ [118], CD33+ [117], as well as mesothelin+ [119] target cells. This evidence concerns the gene CD33 and neoplasm.