Avidio As A Novel Oncolytic Immunotherapy Platform For The Treatment Of Colorectal Cancer.

e15210 Background: Colorectal cancer is the third deadliest of all cancers causing more than 50,000 deaths per year in the U.S. Oncolytic viruses have seen limited use for the treatment of cancers, and further improvement of these methods with immune-modulating activities may prove crucial for the effectiveness of these agents in the treatment of human malignancies. To this end, we developed an artificial virus for infectious diseases and immuno-oncology (AVIDIO) platform that employs virus-like vesicles (VLV) for both the delivery of immunomodulatory agents to tumors and oncolytic activity. Methods: The AVIDIO platform is comprised of in vitro evolved RNA-dependent RNA polymerase from an alphavirus, Semliki forest virus, and envelope glycoproteins from vesicular stomatitis virus, which together form VLVs. Both unarmed VLVs and VLVs armed with the p35 subunit of IL-12 (VLV-IL12p35), an immunomodulatory cytokine that can induce Th1-mediated immunity, were tested for oncolytic activity against various cancer cell lines, including MC38 colorectal cancer cells, in vitro. Using the MC38 syngeneic murine tumor model, we evaluated the antitumor activity of VLV-IL-12p35 in vivo. We used tumor growth measurements and analyses of tumor-infiltrating cells after consecutive treatments with VLV-IL-12p35 to monitor its antitumor and immunomodulatory activities, respectively. Results: VLV-IL-12p35 showed robust oncolytic activity against MC38 cells in vitro, killing over 80% of cells within 24 h. Treatment of intradermal MC38 tumors by intra-tumoral delivery of VLV-IL-12p35 resulted in more than 65% suppression of tumor growth within 2 weeks ( p< 0.05). VLV-IL-12p35-treated tumors also harbored significantly more CD8+ T cells, IFN-gamma-producing CD4+ T cells, and reduced numbers of Foxp3+ regulatory T cells. Conclusions: Our results show that VLV-IL-12p35 derived from the AVIDIO platform has oncolytic activity in vitro and antitumor and immunomodulatory activities in vivo. Therefore, AVIDIO is a promising platform for the delivery of immunomodulatory agents to tumors. Further optimization of the platform, including the addition of other immunomodulatory agents, is in progress to advance the AVIDIO platform to clinical applications for colorectal cancer.