Abstract A041: Rejuvenation: Innovative technology to improve T-cell antitumor properties through partial reprogramming

The T-cell identity and age determine function and fitness over a T-cell’s lifespan. This is particularly relevant when T cells are derived from patients with chronic viral infection or cancer. It is well known that increased T-cell age and differentiation and increased effector and exhausted phenotypes are associated with reduced anti-tumor efficacy and the need for higher infusion T-cell numbers for the treatment of hematological or solid tumors during adoptive cell therapies (ACT) (Kishton 2022). In an effort to overcome these barriers, methods to de-differentiate T cells into induced pluripotent stem cells (iPSCs) that return to embryonic immaturity, but lose their functional identity, have been extensively explored in the past years. Early work revealed several challenges to re-differentiate iPSCs into T cells with the desired functional phenotype, requiring a complex and time-consuming process. Here, we bring our novel strategy that counters the impact of aging on T-cell function through cellular rejuvenation without de-differentiating to iPSCs. We achieved T-cell rejuvenation via partial reprogramming of aged T cells by transiently expressing transcription factors associated with iPSC reprogramming. This proprietary partial reprogramming methodology reduces epigenetic age and rejuvenates T cells while maintaining the phenotype and function of conventional T cells. We were the first to illustrate the ability to reduce the epigenetic age of T cells without fully de-differentiating to iPSCs. Our initial studies with PBMCs showed a significant reduction in epigenetic age. On subsequent RNAseq analyses, we observed that rejuvenated and conventional T cells have equivalent transcriptomes, suggesting the maintenance of identity. Functionally, the TRJ cells are characterized by greatly improved cell-expansion capacity, together with increased expression of markers associated with T-cell stemness, including CCR7 and CD62L. In vitro studies of NY-ESO-1-targeted T-cell receptor (TCR) or a CD19-targeted chimeric antigen receptor (CAR) TRJ cells exhibited improved antitumor properties compared with non-rejuvenated T-cell control (TCT) cells in sequential cell-killing assays. We also confirmed the enhanced in vivo antitumor efficiency of NY-ESO-1 TCR TRJ cells in a murine xenograft tumor model. When tumor-infiltrating lymphocytes (TILs) are rejuvenated with the same rejuvenation technology the TILs showed enhanced cell-expansion capacity, and improvements in T-c