CD28/4-1BB CD123 CAR T cells in blastic plasmacytoid dendritic cell neoplasm.

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is associated with a remarkably poor prognosis and with no treatment consensus. The identification of relevant therapeutic targets is challenging. Here, we investigated the immune functions, antileukemia efficacy and safety of CD28/4-1BB CAR T cells targeting CD123 the interleukin (IL)-3 receptor alpha chain which is overexpressed on BPDCN. We demonstrated that both retroviral and lentiviral engineering CD28/4-1BB CD123 CAR T cells exhibit effector functions against BPDCN cells through CD123 antigen recognition and that they efficiently kill BPDCN cell lines and BPDCN-derived PDX cells. In vivo, CD28/4-1BB CD123 CAR T-cell therapy displayed strong efficacy by promoting a decrease of BPDCN blast burden. Furthermore we showed that T cells from BPDCN patient transduced with CD28/4-1BB CD123 CAR successfully eliminate autologous BPDCN blasts in vitro. Finally, we demonstrated in humanized mouse models that these effector CAR T cells exert low or no cytotoxicity against various subsets of normal cells with low CD123 expression, indicating a potentially low on-target/off-tumor toxicity effect. Collectively, our data support the further evaluation for clinical assessment of CD28/4-1BB CD123 CAR T cells in BPDCN neoplasm.