Abstract 950: Engineered oncolytic vesiculovirus downsizes pancreatic tumor and boosts immune response

Abstract Vesicular stomatitis virus (VSV) is one of the leading oncolytic virus prototypes used in both preclinical and clinical cancer research. A newly engineered chimeric vesiculovirus, VMG, has been tested against various cancer types, including pancreatic ductal adenocarcinoma (PDAC). However, the effectiveness of virotherapies for PDAC is often limited by the immunosuppressive factors present in the tumor microenvironment. Moreover, the presence of hyaluronic acid (HA) and collagen (CN) in the microenvironment contributes to increased tumor stiffness and interstitial fluid pressure, which impede the delivery of drugs, oncolytic viruses, and immune cells into the tumor. To address these challenges, we developed VMG expressing bacterial collagenase (CNase), mouse hyaluronidase (mPH20), or a special enzyme (Enz) having both CNase and PH20-like effects; and evaluated their efficacy in a preclinical Pan02 PDAC model. Genetic modifications to VMG did not compromise its oncolytic activity or replicability in vitro, as shown by MTS assays and kinetic studies. In vivo studies revealed that VMG-Enz significantly reduced tumor volume compared to other synthetic viruses. Immunohistochemistry (IHC) and quantitative polarized light imaging (QPLI) confirms that the hybrid VMG viruses effectively dismantled stromal components, facilitating enhanced viral infection and propagation into the tumor. Flow cytometry analysis indicated a substantial increase in CD8+ T cells, granzyme B+ T cells, dendritic cells, and natural killer cells, alongside a decrease in M-MDSCs, which are indicators of successful onco-immunotherapy. However, we also noticed an elevation of immune checkpoint markers, including PD-1, PDL-1, PDL-2, and anti-viral resistance genes for IFN-α, IFN-β and Mx-1 after viral treatment which may have limited complete tumor remission by the VMG vectors. We conclude that VMG-Enz successfully enhanced immune response and significantly reduced tumor volume by altering stromal HA and collagen levels. Further studies are needed to explore VMG-Enz's potential as combination therapy with immune checkpoint inhibitors or type I interferon antagonists to achieve complete tumor eradication and enhance survival benefits in experimental animals. Citation Format: Khandoker Usran Ferdous, Mulu Z. Tesfay, Aleksandra Cios, Isabelle R. Miousse, Bolni Marius Nagalo. Engineered oncolytic vesiculovirus downsizes pancreatic tumor and boosts immune response [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 950.