Patient outcomes and persistence of CAR T cells after therapy. (A) Progression-free survival (PFS) and overall survival (OS) of study patients. (B) Persistence of genetically modified T cells postinfusion was assessed by droplet digital PCR (ddPCR) and by flow cytometry as previously described.⁹  ddPCR was used to evaluate integrated CAR transgene copy number per microgram of genomic DNA (gDNA). Insets (bar graphs) show CAR copy number (mean ± standard deviation [SD], log-axis) at the latest time point. CAR⁺ Jurkat Clone 12 (stably expressing CD19-specific CAR [P]) was used as positive control, and Water (W) was used as negative control alongside patient sample (S). Using flow cytometry, total viable cells were gated to reveal CD3⁺CAR⁺ T cells and CD19⁺CD20⁺ B cells. Ex vivo expanded, genetically modified CD19-specific CAR^pos T cells were used as positive controls, and CAR^neg normal donor peripheral blood mononuclear cells or ex vivo expanded mock electroporated cells were used as negative controls.