Evaluation of dasatinib and ponatinib for the control of CD123 CAR-T cell functionalities.

CD123 CAR-T cells (CAR123) represent a promising therapeutic approach for blastic plasmacytoid dendritic cell neoplasm (BPDCN) and CD123+ acute myeloid leukemia (AML). However, the pro-inflammatory environment resulting from CAR-T cell activation can induce CD123 upregulation on endothelial cells and potential on-target/off-tumor toxicity. We evaluated the capacity of two tyrosine kinase inhibitors (TKIs), dasatinib and ponatinib, to reversibly inhibit CAR-T cell functions. Using different in vitro models of CAR123 co-culture with BPDCN and AML cell lines, we show that both TKIs reduce CAR123 activation phenotype (CD69 and CD25), tumor necrosis factor α (TNF-α) and interferon-γ (IFN-γ) secretion; degranulation (CD107a); and killing of leukemia cells. Moreover, this inhibition was reversible after elimination of the TKIs. However, only dasatinib was effective at clinically relevant concentrations; 50 nM inhibited TNF-α and IFN-γ secretion, with only a slight reduction in cytotoxicity toward leukemia cells and allowed effective control of CAR-T cell cytotoxicity against endothelial cells in relation to the inhibition of cytokine secretion. Thus, dasatinib could be used to minimize potential CAR123 toxicity toward endothelial cells without compromising its anti-leukemic effects. However, a higher dose could be used to completely inhibit CAR-T cell functionality in the event of toxicity.