Abstract 6658: TcE armed oncolytic virus VSV-GP combines oncolysis and T-cell retargeting for improved efficacy
Authors: Ponnurangam Aparna , Schwaiger Theresa , Walter Sophie , Bartl Simone , Mayr Melissa , Petersson Monika , Schoenberger Tanja , Heinemann Fabian , Gross Peter , Rist Wolfgang , Kasturirangan Srinath , Lempp Charlotte , Petschenka Jutta , Das Krishna , Tobias Nolden 
Published: March 2024

Abstract
Background: Oncolytic viruses, such as the chimeric vesicular stomatitis virus variant VSV-GP have dual modes of action, direct tumor-cell killing, and activation of tumor-specific immunity. While tumor cells deficient in type I interferon (IFN) response are permissive to VSV-GP replication and killing, IFN competent tumor cells are protected from VSV-GP-mediated oncolysis. Our previous data demonstrated that VSV-GP therapy turns immunologically ‘cold’ tumors ‘hot’ by increasing infiltration of T cells into the tumor. The aim of this study was to use the VSV-GP platform to locally express a T cell engager (TcE) molecule to redirect these T cells to destroy non-permissive IFN competent tumor cells expressing the target of the TcE on their cell surface.
Methods: We selected EpCAM as the target antigen and used a bispecific EpCAM-TcE molecule consisting of two variable single chain fragments against EpCAM and CD3, respectively. VSV-GP encoding EpCAM-TcE (VSV-GP-EpCAM-TcE) or an invariant control TcE (VSV-GP-TNP-TcE) were generated as previously described. T cells were co-cultured with human target cells expressing EpCAM on their cell surface, either infected with the VSV-GP-EpCAM-TcE virus or with supernatant from VSV-GP-EpCAM-TcE infected cells. T cell activation, proliferation, degranulation and cytokine secretion were analyzed by flow cytometry and multiplex cytokine assays as a measure of TcE mediated cross-linking of T cells to their target on cancer cells. Patient-derived head and neck squamous cell carcinoma (HNSCC) tumors were sectioned into approximately 200 µM slices and infected with the virus. T cell activation was measured by cytokine secretion. The therapeutic potential of VSV-GP-EpCAM-TcE was tested in vivo in cell-line derived xenograft (CDX) models implanted in immunodeficient mice humanized with donor-derived PBMCs or CD34+ cells.
Results: Virus fitness was maintained for VSV-GP encoding the TcE molecule. Using co-culture assays, we demonstrated that EpCAM-TcE molecule is successfully expressed by VSV-GP and can activate both CD4+ and CD8+ T cells resulting in proliferation, degranulation, and cytokine secretion. Furthermore, we validated the concept using patient-derived HNSCC tumor slices which are representative of complex human tumor ecosystems. We could confirm that cancer cells infected by VSV-GP-EpCAM-TcE virus express functional TcE molecule and activates T cells to secrete IFNγ and TNFα. Finally, we tested the concept in two different CDX models where VSV-GP-EpCAM-TcE showed improved tumor growth inhibition due to a combined effect of oncolysis and T cell activation by EpCAM-CD3 TcE.
Summary: The oncolytic virus VSV-GP can be successfully armed with a TcE to redirect tumor-infiltrating T cells to destroy tumor cells which are not permissive to viral replication. This resulted in an enhanced therapeutic efficacy compared to just the oncolytic effect.
Citation Format: Aparna Ponnurangam, Theresa Schwaiger, Sophie Walter, Simone Bartl, Melissa Mayr, Monika Petersson, Tanja Schoenberger, Fabian Heinemann, Peter Gross, Wolfgang Rist, Srinath Kasturirangan, Charlotte Lempp, Jutta Petschenka, Krishna Das, Nolden Tobias. TcE armed oncolytic virus VSV-GP combines oncolysis and T-cell retargeting for improved efficacy [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 6658.