Percentages of CAR T cells in the blood and CSF. (A) Persistence of EGFR⁺ CAR T cells in blood circulation of patients after CAR T-cell infusion on days 0, 1, 7, 14, 21, and 28. The percentage of EGFR⁺ T cells are gated from live CD3⁺ cells. (B) Expansion and persistence of CD19CAR T cells in blood of patients, as measured by Woodchuck post-transcriptional regulatory element (WPRE) copy number per milliliter of blood. (C) Levels of CD19⁺ cells in blood circulation after CAR T-cell infusion. CD19⁺ cells are gated from live cells. (D) Persistence of EGFR⁺ CAR T cells in CSF from unique patient number (UPN) 272 on day 0 and on days 7 and 14 post–T-cell infusion. Absolute cells per milliliter of CSF (left panel) and flow cytometry plots of CD3⁺ cell and EGFR⁺ cells on day 7 (middle panel) and on day 14 (right panel) post–CAR T-cell infusion. (E) Brain MRI series of UPN 475 pre–CAR T-cell infusion (left panel) and post–CAR T-cell infusion (right panel). Images are T1 weighted postcontrast axial. The pretherapy scan shows an enhancing lesion in the left basal ganglia (arrow) that is no longer present at 28 days post–CAR T-cell infusion. SD, stable disease.