Abstract 6038: 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 One critical challenge of effective cancer therapies is addressing intertumoral and intratumoral heterogeneity of immunologically visible antigens. Antigenic diversity is a particular challenge for therapies that rely on the induction of a broad repertoire of cytotoxic T cells (CTLs) to eliminate malignant cells. Therapeutic interventions, such as αPD1, can partially mitigate this challenge by rescuing CTLs constrained by immune inhibitory mechanisms, such as intratumoral upregulation of the PDL1/PDL2 pathway. Cancer vaccines are rapidly advancing as a mechanism to expand the repertoire of effector T cells thereby broadening immune recognition and elimination 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) provides the necessary requirements for translation into clinical benefit. Vaccine immunogenicity was enhanced by limiting expression of proteins that suppress immune responses (B7H3, TGFβ1, TGFβ2) and by expression of key cytokines that facilitate activation of dendritic cells (CD40L, GMCSF, IL12). In human in vitro assays, NGEN-143 significantly increased the breadth and magnitude of T cells activated against tumor associated antigens (TAAs) and shared neoantigens (TSAs) across a wide range of HLA types. IFNɣ producing T cells measured by ELISpot (SFU/1e6 PBMCs) were increased to 10 TAAs (42, 972 ± 4, 105) and 22 TSAs (2, 493 ± 484) compared to unmodified controls (TAAs, 2, 889 ± 993; TSAs, 200 ± 71). IFNɣ responses were not preferentially directed against a subset of TAAs, TSAs or epitopes. NGEN-143 significantly increased activated T cells with anti-tumor effector function. NGEN-143 preferentially expanded CD8+ polyfunctional (IFNɣ+/-TNFα+/-GzmB+) T cells with effector (CCR7-CD45RO+) and central memory (CCR7+CD45RO+) phenotypes, skewed CD4+ T cells towards Th1 (Tbet+IFNɣ+) over Th2 (GATA4+IL4+) cells, and increased CD8+ T cell expression of PD1 demonstrating TCR engagement. Cytolytic function of NGEN-143 activated CD8+ T cells was confirmed by caspase-3 mediated killing of tumor cell targets. Consistent with in vitro data, murine vaccines with immunogenicity enhancing modifications homologous to NGEN-143 significantly improved survival outcome in immunologically ‘cold’ (B16F10) and ‘warm’ (CT26) syngeneic tumor models. In both models, vaccine significantly increased tumor infiltration of CD4+ and CD8+ T cells, inhibited tumor growth, and prolonged survival. In the CT26 model, vaccine monotherapy completely inhibited tumor growth (n=7/10) and mice were protected from rechallenge (n=7). Combination with αPD1 synergistically increased vaccine survival benefit. Our data demonstrate NGEN-143 has all the features to underpin clinical use in patients with NSCLC. Citation Format: Bernadette Ferraro, Justin J. Arndt, Grace Tan, Nicholas S. LeFlohic, 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 American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 6038.