Human CD19-specific switchable CAR T-cells are efficacious as constitutively active CAR T-cells but cause less morbidity in a mouse model of human CD19 + malignancy

Christopher A. Pennell, Heather Campbell, Meghan D. Storlie, Sara Bolivar-Wagers, Mark J. Osborn, Yosef Refaeli, Michael Jensen, Sophie Viaud, Travis S. Young, Bruce R. Blazar

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


Current Food and Drug Administration (FDA)-approved CD19-specific chimeric antigen receptor (CAR) T-cell therapies for B-cell malignancies are constitutively active and while efficacious, can cause morbidity and mortality. Their toxicities might be reduced if CAR T-cell activity was regulatable rather than constitutive. To test this, we compared the efficacies and morbidities of constitutively active (conventional) and regulatable (switchable) CAR (sCAR) T-cells specific for human CD19 (huCD19) in an immune-competent huCD19 + transgenic mouse model. Conventional CAR (CAR19) and sCAR T-cells were generated by retrovirally transducing C57BL/6 (B6) congenic T-cells with constructs encoding antibody-derived single chain Fv (sFv) fragments specific for huCD19 or a peptide neoepitope (PNE), respectively. Transduced T-cells were adoptively transferred into huCD19 transgenic hemizygous (huCD19 Tg/0) B6 mice; healthy B-cells in these mice expressed huCD19 Tg. Prior to transfer, recipients were treated with a lymphodepleting dose of cyclophosphamide to enhance T-cell engraftment. In tumor therapy experiments, CAR19 or sCAR T-cells were adoptively transferred into huCD19 Tg/0 mice bearing a syngeneic B-cell lymphoma engineered to express huCD19. To regulate sCAR T cell function, a switch protein was generated that contained the sCAR-specific PNE genetically fused to an anti-huCD19 Fab fragment. Recipients of sCAR T-cells were injected with the switch to link sCAR effector with huCD19 + target cells. Mice were monitored for survival, tumor burden (where appropriate), morbidity (as measured by weight loss and clinical scores), and peripheral blood lymphocyte frequency. CAR19 and sCAR T-cells functioned comparably regarding in vivo expansion and B-cell depletion. However, sCAR T-cells were better tolerated as evidenced by the recipients' enhanced survival, reduced weight loss, and improved clinical scores. Discontinuing switch administration allowed healthy B-cell frequencies to return to pretreatment levels. In our mouse model, sCAR T-cells killed huCD19 + healthy and malignant B-cells and were better tolerated than CAR19 cells. Our data suggest sCAR might be clinically superior to the current FDA-approved therapies for B-cell lymphomas due to the reduced acute and chronic morbidities and mortality, lower incidence and severity of side effects, and B-cell reconstitution on cessation of switch administration.

Original languageEnglish (US)
Article numbere005934
JournalJournal for ImmunoTherapy of Cancer
Issue number12
StatePublished - Dec 15 2022

Bibliographical note

Funding Information:
This study was funded by National Institute of Allergy and Infectious Diseases (R37 AI34495), National Cancer Institute (P01 CA065493, R01 CA208398), Children's Cancer Research Fund (N/A), Randy Shaver Cancer Research and Community Fund (N/A), Masonic Cancer Center, University of Minnesota (Pre-R01 Award).

Publisher Copyright:
© Author(s) (or their employer(s)) 2022.


  • Adoptive
  • Cell Engineering
  • Chimeric Antigen
  • Cytotoxicity
  • Hematologic Neoplasms
  • Immunologic
  • Immunotherapy
  • Receptors


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