Abstract 691: Irradiated whole tumor cells pulsed with mannan-BAM, TLR ligands and anti-CD40 antibody serve as a potent tumor cell vaccine against glioblastoma

Abstract Despite numerous therapeutic advances in cancers, the treatment of glioblastoma multiforme (GBM) remains a challenge. Boosting T-lymphocyte mediated responses against GBM offers a promising approach towards solving this problem. Herein, we present a therapeutic vaccination strategy that promotes the phagocytosis of tumor cells, enhances tumor antigen presentation, and induces a tumor-specific adaptive immune response with subsequent tumor eradication. This strategy consists of subcutaneous injection of irradiated whole tumor cells (rWTC) pulsed with phagocytic agonists (Mannan-BAM), TLR ligands (LTA, Poly (I:C), and R-848), and anti-CD40 agonistic antibody (collectively abbreviated as rWTC-MBTA). We evaluated the therapeutic efficacy of rWTC-MBTA strategy in mouse syngeneic GBM tumor models with GL261 and SB28 cells. In GL261 GBM model, complete regression (CR) of intracranial tumors was achieved in 70% (7/10) of rWTC-MBTA treated animals while none survived in the control group. Of note, the therapeutic efficacy of rWTC-MBTA was abolished in CD4-T and/or CD8-T lymphocyte depleted mice. Immunophenotyping analyses of peripheral lymph nodes and brain tumors of rWTC-MBTA treated mice demonstrated increased antigen presenting cells (dendritic cells and MHC II+ monocytes) and increased cytotoxic IFNγ, TNFα, and granzyme B-secreting CD4-T and CD8-T cells. All three CR mice that were rechallenged with GL261 cells intracranially 14 months after their last rWTC-MBTA treatment resisted tumor development, confirming the establishment of long-term immunological memory. In SB28 GBM model, 80% (8/10) rWTC-MBTA treated mice survived past 95 days after tumor cell implantation without any GBM-related symptoms, with median survival being only 35 days in control groups. In summary, our study demonstrated that rWTC-MBTA strategy can induce potent adaptive immune response against GBM in pre-clinical models. Citation Format: Herui Wang, Rogelio Medina, Juan Ye, Samik Chakraborty, Ondrej Uher, Mitchell Sun, Jan Zenka, Mark R. Gilbert, Karel Pacak, Zhengping Zhuang. Irradiated whole tumor cells pulsed with mannan-BAM, TLR ligands and anti-CD40 antibody serve as a potent tumor cell vaccine against glioblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 691.