Tu163 - Cytokine-driven Modulation of CART84 Phenotype and Function for AML Therapy

Abstract Text: CD84 antigen is an immunoreceptor overexpressed in acute myeloid leukemia (AML). We developed a Chimeric Antigen Receptor (CAR) T cell targeting CD84 (CART84), which has demonstrated efficacy against AML in preclinical models. Less differentiated T-cell subsets within CAR T-cell products are associated with improved persistence and potency. Interleukin (IL) 21 promotes the expansion of the long-lived memory stem T-cell (TSCM) compartment, which enhances CAR T-cell proliferation and antitumor activity. This study aimed to characterize the phenotype and functionality of CART84 cells expanded with different cytokine combinations.

Healthy donor T cells were transduced with a lentiviral vector encoding an anti-CD84 CAR (antiCD84scFv-CD8αTM-4-1BB-CD3z) and expanded in three conditions: IL-2; IL-7 and IL-15 (IL7+15); and IL-7, IL-15 and IL-21 (IL7+15+21). We then evaluated their memory phenotype, metabolic capacity, and cytotoxicity towards the CD84+ AML cell line MOLM-13.

We did not observe any differences in the TSCM compartment across conditions. However, the IL-7+15+21 condition yielded the highest proportion of central memory (TCM) CD4 cells, correlating with reduced differentiation into effector memory (TEM) and terminally differentiated effector (TTE) subsets, alongside increased ATP production. Regarding efficacy, both CART84 expanded under IL-7+15 and IL-7+15+21 conditions displayed greater cytotoxicity towards MOLM-13 cells in vitro compared to the IL-2 condition.

In conclusion, although CART84 expansion with IL-21 addition did not increase the TSCM compartment, it promoted a central memory-enriched phenotype in CART84 cells , enhancing metabolic activity and cytotoxic efficacy against CD84+ cells. These results further support the potential of IL-21 in optimizing CAR T-cell therapies for AML treatment.