RESUMO
CD33 and CD123 are expressed on the surface of human acute myeloid leukemia blasts and other noncancerous tissues such as hematopoietic stem cells. On-target off-tumor toxicities may limit chimeric antigen receptor T cell therapies that target both CD33 and CD123. To overcome this limitation, we developed bispecific human CD33/CD123 chimeric antigen receptor (CAR) T cells with an "AND" logic gate. We produced novel CD33 and CD123 scFvs from monoclonal antibodies that bound CD33 and CD123 and activated T cells. Screening of CD33 and CD123 CAR T cells for cytotoxicity, cytokine production, and proliferation was performed, and we selected scFvs for CD33/CD123 bispecific CARs. The bispecific CARs split 4-1BB co-stimulation on one scFv and CD3ζ on the other. In vitro testing of cytokine secretion and cytotoxicity resulted in selecting bispecific CAR 1 construct for in vivo analysis. The CD33/CD123 bispecific CAR T cells were able to control acute myeloid leukemia (AML) in a xenograft AML mouse model similar to monospecific CD33 and CD123 CAR T cells while showing no on-target off-tumor effects. Based on our findings, human CD33/CD123 bispecific CAR T cells are a promising cell-based approach to prevent AML and support clinical investigation.
RESUMO
Graft-versus-host disease (GVHD) remains an important cause of morbidity and mortality after allogeneic hematopoietic cell transplantation (allo-HCT). For decades, GVHD prophylaxis has included calcineurin inhibitors, despite their incomplete efficacy and impairment of graft-versus-leukemia (GVL). Distinct from pharmacologic immune suppression, we have developed what we believe is a novel, human CD83-targeted chimeric antigen receptor (CAR) T cell for GVHD prevention. CD83 is expressed on allo-activated conventional CD4+ T cells (Tconvs) and proinflammatory dendritic cells (DCs), which are both implicated in GVHD pathogenesis. Human CD83 CAR T cells eradicate pathogenic CD83+ target cells, substantially increase the ratio of regulatory T cells (Tregs) to allo-activated Tconvs, and provide durable prevention of xenogeneic GVHD. CD83 CAR T cells are also capable of treating xenogeneic GVHD. We show that human acute myeloid leukemia (AML) expresses CD83 and that myeloid leukemia cell lines are readily killed by CD83 CAR T cells. Human CD83 CAR T cells are a promising cell-based approach to preventing 2 critical complications of allo-HCT - GVHD and relapse. Thus, the use of human CD83 CAR T cells for GVHD prevention and treatment, as well as for targeting CD83+ AML, warrants clinical investigation.
