Boosting Oncolytic HSV Immunotherapy by Enabling Necroptosis - PROJECT SUMMARY Oncolytic viruses (OVs) are a promising class of cancer therapeutics due to their dual ability to directly lyse tumor cells and stimulate anti-tumor immune responses. Talimogene laherparepvec (T-Vec), a genetically engineered herpes simplex virus-1 (HSV-1), is FDA-approved for treating melanoma, but a recent Phase III trial combining T-Vec with immune checkpoint blockade (ICB) failed to show a significant survival benefit in patients with advanced melanoma. We hypothesize that T-Vec’s failure in this setting is due to its inability to induce necroptosis, a highly immunogenic form of cell death, because of the viral protein ICP6, which inhibits necroptosis by blocking receptor-interacting protein kinase 3 (RIPK3). To address this, we have engineered a novel oncolytic HSV-1 variant, oHSV-1(ICP6mut), by mutating the RIP Homology Interaction Motif (RHIM) in ICP6, thereby restoring Z-NA Binding Protein 1 (ZBP1)-dependent nuclear necroptosis. This form of cell death releases immunogenic nuclear contents, transforming the tumor microenvironment (TME) and potentially enhancing ICB therapy efficacy. Our proposal aims to evaluate whether oHSV-1(ICP6mut) can overcome T-Vec’s limitations by activating nuclear necroptosis to boost anti-tumor immunity. Specifically, we will (1) determine how oHSV-1(ICP6mut)-triggered necroptosis reshapes the melanoma TME compared to T-Vec in syngeneic mouse models, and (2) assess whether oHSV-1(ICP6mut) enhances systemic immune activation and long-term outcomes when combined with ICB, and how it compares to T-Vec in a human organoid system.
