Abstract B85: Anticancer efficacy of a novel immune-stimulating oncolytic virus: VG161 in gastrointestinal cancers

Oncolytic viruses (OVs) are the wild-type or genomic modified viruses, which can specifically replicate in cancer cells but not in normal cells. They cause cancer cell lysis and more importantly, their replication in tumor cells induces an antitumor immune response from the host. As synergistic stimulation of antitumor immune response requires multiple immune-regulatory factors, OVs armed with multiple immune-modulating factors are of high potential in cancer immunotherapy. We have constructed a novel herpes simplex virus type-1 virus (HSV-1), VG161, that is armed with IL12, IL15, and a unique PDL-1 peptide blocker. The aim of this study is to investigate the anticancer efficacy of VG161 in gastrointestinal (GI) cancers including gastric, hepatic, and colorectal cancers. The immune-stimulating activities in tumor-bearing immune competent mice were also demonstrated. VG161 was given to the tumor-bearing animals by intratumor injection (5 × 106-5 × 107 PFU/animal, once a day for 3-5 days). Antitumor activity of VG161 was tested in both immune-deficient mice as well as in immune-competent mice. Oncolytic activity of VG161 was demonstrated in human gastric (SGC-7901), hepatic (patient-derived xenograft, PDX), and colorectal (LS174T) cancer-bearing nude mice as the human tumors are susceptible to HSV infection and the immune system is compromised in those models. To determine the antitumor immune response activated by VG161, colorectal cancer (CT26) syngeneic model was used in immune competent animals and T cell subpopulation analysis, ELISPOT, and tumor rechallenge assay was applied to measure specific antitumor immunity. VG161 caused complete tumor eradication in PDX and CT26 tumor models and significantly inhibited tumor growth in SGC-7901 and LS174T models. All animals treated with VG161 survived for many months till sacrificed. In the CT26 model, no tumor could be found after rechallenging with the same tumor cells. The number of CD8+ tumor infiltrated T cells was significantly increased, and systemic specific anticancer immunity was confirmed by ELISPOT assay on T cells isolated from spleen. VG161 is a novel oncolytic virus that is both strong in oncolysis and stimulating antitumor immunity for GI cancers. Intratumorally expressing multiple immune-regulatory factors by an oncolytic virus may significantly change the GI tumor immune microenvironment and stimulate anticancer immunity, to further enhance the efficacy of the oncolytic virus. Citation Format: Ronghua Zhao, Jun Ding, Tianchi Liu, Shuyun Liu, Dmitry Chouljenko, Yanal Murad, Erica Lee, Guoyu Liu, Luke Bu, William Jia. Anticancer efficacy of a novel immune-stimulating oncolytic virus: VG161 in gastrointestinal cancers [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2018 Nov 27-30; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(4 Suppl):Abstract nr B85.