Abstract 6655: Oncolytic adenovirus dually expressing interferon beta and membrane-stable CD40 ligand increases polyfunctional CD8+T cells associated with antitumor activity

Abstract MEM-288 is a dual-transgene armed oncolytic adenovirus in phase 1 clinical development as a standalone agent and in combination with immune checkpoint inhibitors (ICI). It encodes two potent immune agonists: IFNβ and a recombinant membrane-stable chimeric form of CD40L (MEM40). We previously demonstrated this agonist combination is better than either agonist individually to activate conventional dendritic cells type 1 (cDC1) crucial for CD8+ T cell cross-priming, and to increase tumor-antigen reactive CD8+ T cells. Furthermore, first-in-human Phase 1 clinical trial (NCT05076760) results of MEM-288 for advanced non-small cell lung cancer (NSCLC) and other solid tumors showed MEM-288 tumor shrinkage was associated with systemic antitumor T cell immunity as demonstrated by cytokine, T cell clonotype, and tumor neoantigen analysis. Here, we investigated the precise nature of the localized and systemic T cell response induced by MEM40 + IFNβ in preclinical tumor models. Single-cell RNA sequencing of tumor infiltrating T lymphocytes (TILs) revealed that MEM40 + IFNβ elicited a strong increase in T cells expressing Granzyme B and PRF1, key effector cytokines and cytotoxicity mediators. We tracked the CD8+ T cell response in CD45.1 C57BL/6 mice implanted with syngeneic B16 tumor expressing the model antigen OVA. Interestingly, intratumoral treatment with adenovirus encoding MEM40 + IFNβ did not cause an appreciable increase in absolute numbers of antigen-reactive CD8+ T cells, despite tumor growth inhibition. However, MEM40 + IFNβ compared to control unarmed adenovirus induced a significant (p < 0.005) 5-fold increase in polyfunctional IFNγ+TNFα+PRF1+ and IFNγ+TNFα+Granzyme B+ CD8+ T cells. Polyfunctional CD8+ T cells have the capacity to simultaneously produce effector cytokines and cytotoxicity mediators and are known to be strongly associated with antitumor T cell activity. The robust polyfunctional CD8+ T cell response in these studies is consistent with T cell-driven antitumor activity found in both our preclinical tumor experiments and our clinical studies in advanced NSCLC patients responding to MEM-288. Overall, our findings suggest MEM40 + IFNβ generates a strong polyfunctional CD8+ T cell response in the TME that warrants continued evaluation to understand the pleiotropic mechanisms of this cancer immunotherapy. Citation Format: Mark J. Cantwell, Andreas N. Saltos, Hong Zheng, Dana Foresman, Amer A. Beg. Oncolytic adenovirus dually expressing interferon beta and membrane-stable CD40 ligand increases polyfunctional CD8+T cells associated with antitumor activity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6655.