CARG-2020, an oncolytic artificial virus co-delivering three immunomodulators, to regress and cure established tumors in mice.

Abstract

e14560 Background: Colorectal cancer (CRC) is the third leading cause of cancer-related deaths in humans. Treatment of late-stage CRC remains ineffective, even with the use of latest immunotherapies. Oncolytic viruses have shown limited use for the treatment of cancers, and further improvement of these agents with immune-modulating activities may prove crucial for patients with CRC and other malignancies. To this end, we developed CARG-2020 as an artificial virus for infectious diseases and immuno-oncology (AVIDIO) that employs virus-like vesicles (VLV). VLVs, which are membrane-encapsulated RNA replicons, are oncolytic and can deliver multiple genes resulting in the modulation of several independent immune pathways. Methods: The AVIDIO platform is comprised of in\xa0vitro evolved RNA-dependent RNA polymerase from an alphavirus, Semliki Forest virus, and envelope glycoproteins from vesicular stomatitis virus, which together form VLVs. Unarmed or empty vector (VLV), VLV armed with IL-12 (VLV-IL-12) and a VLV that simultaneously expresses IL-12, a dominant-negative form of IL-17 receptor A (dn-1L17RA) and shRNAs targeting PD-L1 (CARG-2020), were given intratumorally to test their therapeutic potential against established (500-600mm3) MC38 tumors in mice. We used tumor growth measurements and analyses of tumor-infiltrating cells after consecutive treatments with these agents to monitor their antitumor and immunomodulatory activities, respectively. Results: Both VLV-IL-12 and CARG-2020 regressed the tumors to undetectable levels in most mice harboring syngeneic MC38 tumors when given intratumorally. CARG-2020, carrying IL-12, dn-IL17RA and PD-L1 shRNA, exerts broader spectrum of immuno-responses and higher number of complete response rates compared with VLV-IL-12. Treatment of primary tumors with VLV-IL-12 or CARG-2020 also significantly repressed the growth of secondary tumors on the other flank of mouse’s body, suggesting an effective systemic immunity elicited by these two agents against the same type of tumors. In addition to the marked local and systemic activation of Th1 cells and CD8+ T cells by both vectors, CARG-2020 also downregulated PD-L1 expression in tumors, and suppressed expression of IL-17A-activated chemokines CXCL1 and CXCL2 that are known to promote cancer development and therapy resistance. Conclusions: As an oncolytic RNA replicon, AVIDIO platform-derived CARG-2020 encodes IL-12, dn-IL-17RA and PD-L1 shRNAs which are expressed concurrently within the same vector. CARG-2020 modulates IL-12, IL-17RA and PD-L1 signaling, and exerts broad immune modulation in tumor microenvironment. Treatment with CARG-2020 eliminates the majority of grafted large tumors in mice, and is effective against both primary and distal tumors. Based on this impressive efficacy results, further development of CARG-2020 in colorectal patients is warranted.