Abstract B057: An optimized off-the shelf whole tumor cell vaccine activates T cells that recognize a diverse antigen repertoire with potential to provide meaningful clinical benefit to patients with NSCLC

Abstract Effective cancer immunotherapies rely on tumor reactive cytotoxic T cells to eliminate malignant cells. One critical challenge lies in the induction of a sufficiently broad repertoire of effector T cells that can address the heterogeneity of immunologically visible antigens. Therapeutic interventions, such as anti-PD1, can partially mitigate this challenge by releasing reactive T cells constrained by respective immune inhibitory mechanisms, such as intra-tumoral upregulation of the PDL1/PDL2 pathway. Cancer vaccines are now into clinical practice to further broaden effector T cells to increase immune recognition of tumor cells. Here we provide preclinical evidence that a carefully designed, off-the-shelf vaccine, derived from six immortalized tumor cell lines (NGEN-143) can provide the necessary requirements for effective translation into clinical benefit. Vaccine immunogenicity was enhanced by limiting the expression of proteins that dampen an effective immune response (B7-H3, TGFb1 TGFb2) and incorporating key cytokines that facilitate activation of dendritic cells (membrane-bound CD40L, GM-CSF, IL-12). In a human in vitro system NGEN-143 increased IFNg producing T cells (42,972 ± 4105 SFU, n=8 HLA diverse donors) by ELISpot against ten TAAs, compared to unmodified controls (2889 ± 993 SFU) without evidence of immunodominance. IFNg responses were not preferentially directed against a subset of TAAs and not limited to a single epitope within a TAA. NGEN-143 also significantly increased characteristics associated with a productive anti-tumor response including increasing the ratio CD4+ Th1 cells (Tbet+IFNg+) vs Th2 (GATA4+IL4+), expansion of CD4+ and CD8+ T cells with effector (CCR7-CD45RO+) and central memory (CCR7+CD45RO+) phenotypes that produced IFNg+/-TNFa+/-concurrently with granzyme B. Functional activation of CD8+ T cells was confirmed by significant upregulation of PD1 by CD8+ T cells, reflecting TCR signaling and activation, and caspase-3 mediated killing of two unique immortalized tumor cell targets. Consistent with in vitro data, administration of mouse analog vaccines, designed to include the same immunogenicity enhancing modifications as NGEN-143, significantly improved survival in both immunologically cold (B16-F10) and hot (CT26) syngeneic mouse models. In B16-F10 model, there was a significant increase in tumor infiltrate of both CD4+ and CD8+ T cells but not regulatory T cells compared to vehicle control. In the CT26 model, administration of vaccine alone after implantation leads to complete inhibition of tumor growth (7/10) and 7/7 mice were protected from rechallenge. Further characterization of immune infiltrate in mouse models is on-going. Overall, our data support that off-the shelf whole cell vaccine can induce a uniquely broad anti-tumor T cell repertoire optimized for clinical use in patients with NSCLC. Citation Format: Bernadette Ferraro, Justin Arndt, Grace Tan, Jian Yan, Mark L Bagarazzi, Natalia Savelyeva, Christian H Ottensmeier. An optimized off-the shelf whole tumor cell vaccine activates T cells that recognize a diverse antigen repertoire with potential to provide meaningful clinical benefit to patients with NSCLC [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor Immunology and Immunotherapy; 2024 Oct 18-21; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2024;12(10 Suppl):Abstract nr B057.