While current CAR T cell manufacturing protocols call for 9 to 14 days of ex vivo expansion, Ghassemi et al. showed that CAR T cells harvested at earlier time points (day 3 or 5) exhibited increased proliferation, an improved differentiation state (i.e. more central memory), and enhanced effector function compared to those harvested later (day 9). In a murine xenograft model of ALL, early-harvested CD19 CAR T cells showed improved persistence, robust tumor control, and higher potency than day 9 cells. Analysis of CAR T cell products manufactured under standard protocols suggested that an abbreviated culture would be feasible.
The success of chimeric antigen receptor (CAR)-mediated immunotherapy in acute lymphoblastic leukemia (ALL) highlights the potential of T-cell therapies with directed cytotoxicity against specific tumor antigens. The efficacy of CAR T-cell therapy depends on the engraftment and persistence of T cells following adoptive transfer. Most protocols for T-cell engineering routinely expand T cells ex vivo for 9-14 days. Because the potential for engraftment and persistence is related to the state of T-cell differentiation, we hypothesized that reducing the duration of ex vivo culture would limit differentiation and enhance the efficacy of CAR T-cell therapy. We demonstrated that T cells with a CAR targeting CD19 (CART19) exhibited less differentiation and enhanced effector function in vitro when harvested from cultures at earlier (day 3 or 5) compared with later (day 9) timepoints. We then compared the therapeutic potential of early versus late harvested CART19 in a murine xenograft model of ALL and showed that the anti-leukemic activity inversely correlated with ex vivo culture time: day 3 harvested cells showed robust tumor control despite using a 6-fold lower dose of CART19, whereas day 9 cells failed to control leukemia at limited cell doses. We also demonstrated the feasibility of an abbreviated culture in a large-scale cGMP-compliant process. Limiting the interval between T-cell isolation and CAR treatment is critical for patients with rapidly progressing disease. Generating CAR T cells in less time also improves potency, which is central to the effectiveness of these therapies.
Author Info: (1) Department of Pathology and Laboratory Medicine, Center for Cellular Immunotherapies. (2) Center for Cellular Immunotherapies, Perelman School of Medicine at the University of
Author Info: (1) Department of Pathology and Laboratory Medicine, Center for Cellular Immunotherapies. (2) Center for Cellular Immunotherapies, Perelman School of Medicine at the University of Pennsylvania. (3) Department of Pathology and Laboratory Medicine, Center for Cellular Immunotherapies. (4) Abramson Cancer Center, University of Pennsylvania. (5) Department of Pathology and Laboratory Medicine, Center for Cellular Immunotherapies. (6) Abramson Family Cancer Research Institute, University of Pennsylvania School of Medicine. (7) Division of Oncology, Department of Pediatrics, Children's Hospital of Philadelphia and Perelman School of Medicine at the University of Pennsylvania. (8) Department of Pathology and Laboratory Medicine, Center for Cellular Immunotherapies. (9) Pathology and Laboratory Medicine, Center for Cellular Immunotherapies, University of Pennsylvania. (10) Department of Pathology and Laboratory Medicine, Center for Cellular Immunotherapies. (11) Department of Pathology and Laboratory Medicine, Center for Cellular Immunotherapies. (12) Center for Cellular Immunotherapies, Perelman School of Medicine, University of Pennsylvania. (13) Center for Cellular Immunotherapies, Perelman School of Medicine, University of Pennsylvania. (14) Division of Oncology, Department of Pediatrics, Children's Hospital of Philadelphia and Perelman School of Medicine at the University of Pennsylvania. (15) Center for Cellular Immunotherapies, Perelman School of Medicine, University of Pennsylvania. (16) Pathology and Laboratory Medicine, University of Pennsylvania. (17) Department of Pathology and Laboratory Medicine, Perelman School of Medicine at the University of Pennsylvania milone@pennmedicine.upenn.edu.
