Abstract 694: TG6050 an oncolytic vaccinia virus armed with interleukin 12 and anti-CTLA4 antibody induces TME remodeling and strong anti-tumoral responses

Abstract Background: By replicating specifically into tumor cells, oncolytic vaccinia viruses (VACV) can turn “cold” tumors “hot” while delivering therapeutic payloads into tumor. Thanks to its large genome capacity, multiple cloning loci, and availability of different promoters, VACV is an optimal vector for the design of advanced immunotherapies. Payloads with an established clinical efficacy but limited in terms of tolerability require local delivery. We report here the preclinical characterization of TG6050, a VACV encoding single chain interleukin 12 (IL12) and anti-CTLA4, targeting multiple cancer indications. Methods: TG6050 was generated by insertion of both the single chain IL-12p70, and an anti-CTLA-4 full-length (heavy and light chains independently) into the thymidine kinase (TK) and ribonucleotide reductase (RR) loci, of a triple deleted (ΔJ2R,ΔI4L,ΔM2L) VACV, Copenhagen strain. TG6050 was fully characterized in vitro, i.e. replication in tumor and normal cells, transgenes expression, functionality, and genetic stability. Its preclinical surrogate mTG6050, expressing murine payloads, was used to investigate the in vivo anti-tumoral activities in a broad range of immunocompetent murine models, as well as its mode of action in the reprograming of the tumor microenvironment (TME). Results: TG6050 displayed the same replicative, oncolytic activity, and genetic stability features as benchmark recombinant vaccinia viruses. IL-12 and anti-CTLA4 were both expressed at high levels, and as functional molecules by a broad panel of reference tumor cell lines. Local administration of mTG6050 induced accumulation of transgenes into tumor, with low systemic exposure. Noteworthy, expression of IL-12 did not accelerate the clearance of the viral vector. The combined effects of viral replication, IL-12 and anti-CTLA4 expression translated into impressive antitumoral activities in several syngeneic tumor models including immune-resistant ones such as B16F10 or LLC1. Transcriptomic analyses of the TG6050-treated tumors demonstrated a strong dynamic of infiltration by innate and adaptive immune cells. IFNy-ELISpot analysis on splenocytes confirmed induction of a strong systemic and specific anti-tumoral immune response. Moreover, the combination of TG6050 with ICI improved tumor regression in several challenging tumor models. Conclusion: TG6050 is a novel oncolytic VACV designed for multiple routes of administration, and several tumor indications. Its strong impact on the TME, by massive infiltration of innate and adaptive immune cells, translated into very remarkable therapeutic activities in resistant tumors. This anti-tumor activity was further enhanced by combination with anti-PD-1. Citation Format: Jean-Baptiste Marchand, Fadi Azar, Christelle Demeusoit, Patricia Kleinpeter, Jules Deforges, Fend Laetitia, Chantal Hoffmann, Huguette Schultz, Nathalie Silvestre, Eric Quéméneur. TG6050 an oncolytic vaccinia virus armed with interleukin 12 and anti-CTLA4 antibody induces TME remodeling and strong anti-tumoral responses [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 694.