Parameters for success of CAR T-cell therapy. The success of CAR T-cell therapy depends on the interplay of multiple factors, including T cell fitness before apheresis and after the manufacturing process; the ability of CAR T cells to expand after infusion, both in the blood and at the site of disease; and the characteristics of the tumor, including density of the target antigen on tumor cells and the immunosuppressive nature of the tumor microenvironment. Figure adapted from a slide provided by David Miklos (Stanford, University, Stanford, CA). Professional illustration by Somersault18:24.