Idelalisib and VIPhyb enhance the expansion and functionality of CAR T cells in vitro. CD5 CAR T cells were produced from healthy donors (n = 3) in the presence or absence of idelalisib and VIPhyb and evaluated for growth, transduction efficiency, and in vitro cytotoxicity. (A) CD5 CAR vector design. (B) Transduction efficiency as assessed by GFP expression. (C) Expansion profiles of CD5 CAR T cells under the indicated culture conditions. (D) In vitro cytotoxicity of CD5 CAR T cells generated from healthy controls and expanded under the indicated conditions. eGFP, enhanced green protein; LTR, long terminal repeat; SIN, self-inactivating.