PROJECT SUMMARY The goal of this STTR Phase I application is to establish the feasibility of commercializing a personalized and multi-targeted adoptive T cell therapy (ATCT) for glioblastoma (GBM). GBM is the most common primary brain tumor with a dismal prognosis and relative five-year survival rate of 7.5%. There has been no significant improvement in outcomes for these patients in two decades. In response to this urgent need for novel therapies for GBM patients, we have developed a personalized, autologous ATCT targeting multiple antigens in GBM unique to each patient. We envision administering the ATCT as an adjuvant therapy directly into the tumor bed through an Ommaya reservoir after standard-of-care surgery. Our strategy for generating a GBM- specific ATCT involves applying Prussian blue nanoparticle-based photothermal therapy (PBNP-PTT) to GBM cells ex vivo. During PBNP-PTT, PBNPs are administered to GBM cells that have been excised via surgery, and a near infrared laser is shone onto the mixture ex vivo, thereby generating heat. Under certain conditions, PBNP-PTT delivers a thermal dose that elicits immunogenic cell death (ICD) in GBM cells and facilitates the release of GBM-specific antigens unique to each patient. The PBNP-PTT-treated GBM cells are then co- cultured with autologous dendritic cells (DCs) and T cells, to expand GBM-specific T cells for subsequent infusion back into the patient. Importantly, this platform is designed to develop multi-targeted T cells in an antigen-agnostic manner. Since this approach uses a patient’s own tumor as the source of T cell targets, it does not require a priori chosen antigens. Our published data illustrates the feasibility of our novel ATCT development platform using PBNP-PTT to generate potent and functional GBM-specific T cells against two GBM cell lines, U87 and SNB19, using healthy donor PBMCs HLA-matched to the tumor cell lines. In another published study using an orthotopic U87 xenograft model, we have demonstrated that our ATCT is more effective in generating in vivo tumor regression and long-term survival relative to alternative and control ATCTs. Building on these published results, in this STTR Phase I study, we seek to establish the feasibility of developing autologous GBM-specific T cells with our PBNP-PTT-based platform using blood and GBM tumor samples from patients. Our overall hypothesis is that PBNP-PTT-treated GBM cells facilitate the generation of potent and personalized GBM-specific T cells in an antigen-agnostic manner that exert specific cytotoxicity against autologous patient-derived GBM cells in vitro and in vivo. In Aim 1, we evaluate whether PBNP-PTT- mediated ex vivo expansion generates potent and effective patient-derived GBM-specific T cells and define the mechanisms driving the observed responses. In Aim 2, we test the efficacy of the PBNP-PTT-derived T cells in GBM patient-derived xenograft (PDX) models in vivo compared to other T cell approaches (e.g. B7-H3 CAR T...