267 Pre-clinical evaluation of a new B7-H3 CAR in a human glioblastoma model

Background Glioblastoma (GBM) is the most common and aggressive type of cancer in the central nervous system, characterized by a poor prognosis and limited treatment efficacy. Consistent with findings in other cancer types, the high expression of the transmembrane protein B7-H3 in GBM correlates with enhanced tumor progression and poor prognosis. However, chimeric antigen receptor (CAR) T cell therapy—an effective strategy in hematologic malignancies—has emerged as a promising approach that could complement and enhance conventional treatments for GBM. Previously, we observed that a single intravenous dose of a novel B7-H3-targeted CAR T cell (Y111) significantly extended the survival of mice intracerebrally implanted with the human glioblastoma cell line GBM01, compared to those treated with untransduced T cells.In this study, we aimed to evaluate the efficacy Y111 CAR T cells via three distinct routes of administration: intravenous (IV), intratumoral (IT), and intracerebroventricular (ICV), in a human GBM orthotopic model using the GBM01 cell line.Methods Human GBM01 GFP-Luc cells were stereotaxically injected into the brain of NRG immunocompromised mice. The tumor growth was monitored weekly using in vivo imaging systems (IVIS), and the general condition of mice was evaluated daily. Once tumors became detectable, the animals were randomized into groups to receive Y111 CAR T or untransduced T cells via different routes of administration: a single Intratumoral (IT) dose, a single Intracerebroventricular (ICV) dose, or two Intravenous (IV) doses.Results IT treatment markedly reduced tumor size and, in most animals, eliminated detectable tumor signal, resulting in significantly extended survival compared to the control group. IV treatment also slowed tumor growth and improved survival relative to controls; however, no significant difference was observed using two doses in comparison to a single dose. Although ICV administration reduced tumor growth and prolonged survival compared to the control group, its efficacy was less than IT treatment.Conclusions We are investigating Y111 CAR T cells, a novel immunotherapy targeting B7-H3, for the treatment of glioblastoma. Our results demonstrate that intratumoral (IT) administration of Y111 CAR T cells achieves near-complete preclinical efficacy, establishing this approach as a promising alternative to conventional therapies. Although ICV and two-dose IV treatment were less effective than IT administration, all routes of administration reduced tumor growth and prolonged survival, suggesting Y111 CAR-T cells may have future potential for clinical translation.Ethics Approval Mouse experiments were reviewed and approved by the Animal Care and Use Committee (ACUC) at the National Institutes of Health.