503 Engineering GBM-specific T Cells Using Photothermal Prussian Blue Nanoparticles

INTRODUCTION: Adoptive T cell therapy (ATCT) has successfully treated hematological malignancies and is currently under investigation for solid tumor therapy. In contrast to existing chimeric antigen receptor (CAR) T cell and/or antigen-specific T cell approaches, which target defined antigens, our PBNP-based approach can target a broad repertoire of antigens in GBM in an antigen-agnostic manner. METHODS: We treated GBM cells with PBNP-based photothermal therapy (PBNP-PTT) prior to culturing with dendritic cells (DCs), and subsequent stimulation of T cells. RESULTS: When PBNP-PTT was administered to U87 cells at an immunogenic thermal dose, we effectively expanded U87-specific T cells. DCs cultured ex vivo with PBNP-PTT-treated U87 cells enabled 15- 30-fold expansion of CD4+ and CD8+ T cells. Upon co-culture with target U87 cells, these T cells secreted IFN-G in a specific and dose-dependent manner (up to 647-fold over controls). T cells manufactured using PBNP-PTT elicited specific cytolytic activity against target U87 cells (33-93% killing at an E:T ratio of 20:1), while sparing normal human astrocytes. Similarly, PBNP-PTT on SNB19 cells resulted in a 7-39-fold expansion of T cells, which elicited 25-66% killing of SNB19 cells at an E:T ratio of 20:1. U87-luc cells were then orthotopically inoculated into NSG mice to establish xenograft GBM, and U87-specific T cells developed via PBNP-PTT were intracranially injected. These T cells eliminated U87 tumors in vivo and significantly improved mouse survival compared to mice treated with PBS (p = 0.0047) or non-specific T cells (p = 0.0123) from the same donor. CONCLUSIONS: These findings provide proof-of-concept data supporting the use of PBNP-PTT to stimulate and expand tumor-specific T cells ex vivo for potential use as an ATCT approach for patients with GBM. We are currently using patient-derived tumor samples to generate IND-enabling data.