Oral Presentation Eradicate Cancer 2020

New Strategy for Making CAR-T Cells with an Early Memory Phenotype and Improved Anti-tumour Efficacy (69597)

Joe Jiang Zhu 1 2 , Deborah Meyran 1 , Jeanne Butler 1 , Daniela Tantalo 1 , Lauren Giuffrida 1 , Michael H Kershaw 1 2 , Joseph A Trapani 1 2 , Phillip K Darcy 1 2 , Paul J Neeson 1 2
  1. Peter MacCallum Cancer Centre, Melbourne, VICTORIA, Australia
  2. Sir Peter MacCallum Department of Oncology, The University of Melbourne, Melbourne, Victoria, Australia

In our Phase I CAR-T trial, we found the clinical grade CAR-T cells had a minor frequency of memory T cells. This was correlated with only a transient increase in circulating CAR-T cells. Using the same protocol, CAR-T cells produced from healthy donors’ peripheral blood mononuclear cell (PBMC) also lacked early memory compartments.

We hypothesized that generating CAR-T cells with an early memory phenotype may enable better anti-tumour efficacy and persistence. The project aimed to (1) optimize the protocol and generate CAR-T cells with a higher proportion of early memory subsets, (2) evaluate the in vitro anti-tumour capacity and proliferation, and (3) investigate the in vivo anti-tumour efficacy and long-term persistence.

We optimized the protocol for activation and expansion of early CAR-T cells. This involved pre-sorting naïve T cells from healthy donors’ PBMC and patients’ lymphocytes before CAR-T activation. We generated CAR-T cells with > 60% T stem cell memory (TSCM) from healthy donors' PBMC and ~50% of TSCM from patients’ lymphocytes. In contrast, using the previous clinical protocol, TSCM only accounted for ~20% of conventional healthy donor CAR-T cells and < 5% of patients’ CAR-T products. For functional study, we performed chromium assays and LEGENDplex. The data demonstrated that early CAR-T cells had a competitive antigen-specific killing efficacy and cytokine production, such as TNF-α and IFN-γ. Proliferation assays indicated that early CAR-T cells had improved proliferation capacity. Notably, after a 30-day culture with stimulation, these early CAR-T cells still retained significant self-renewal capacity. The in vivo data also showed that early CAR-T cells exhibited improved tumour control, long-term persistence and overall survival.

In summary, we generated CAR-T cells with an early memory phenotype and also demonstrated that these CAR-T cells had a significant tumoricidal effect both in vitro and in vivo. More importantly, these CAR-T cells demonstrated improved long-term in vivo persistence. This approach may facilitate the development of CAR-T therapy by enhancing post-infusion persistence and long-term tumour control.