TG6050, an oncolytic vaccinia virus encoding interleukin-12 and anti-CTLA-4 antibody induces tumor regression through profound tumor microenvironment remodeling and strong antitumor adaptive immune response [scRNA-seq]
By their selective infection or replication into tumors, oncolytic viruses trigger profound modifications of tumor immune microenvironment with a massive infiltration and activation of T cells. This tumor warming up can be further amplified by the local delivery of powerful immunomodulatory molecules encoded into virus' genome. Those properties are particularly of interest for tumor poorly infiltrated or infiltrated with anergic T cells to reverse patient's unresponsiveness to immune checkpoint inhibitors (ICI).   TG6050 is a new oncolytic vaccinia virus encoding single-chain human Interleukin-12 (hIL-12) and full length anti-cytotoxic T-lymphocyte-associated antigen-4 (@CTLA-4) monoclonal antibody. Replication, oncolysis, selectivity, transgenes expression and functionality of TG6050 were characterized in vitro. Virus and IL-12 pharmacokinetics, antitumoral activities (alone or combined with ICI), and mechanism of action (MOA) were investigated in “hot” (highly infiltrated) and “cold” (poorly infiltrated) syngeneic murine tumor models. MOA was deciphered by monitoring both systemic and tumor immune responses, and tumor transcriptome analyses. Finally, TG6050 safety after repeated intravenous administrations was evaluated in cynomolgus monkeys and special attention was paid to the level of circulating IL-12 potentially associated with toxic effects.  In vitro or in vivo replication of TG6050 in tumor cells allows local expression of functional IL-12 and @CTLA-4. The expression of transgenes, together with the virus replication, translated into an antitumoral activity in both “cold and “hot” tumor murine models that was further amplified by combination with ICI. Analysis of tumor microenvironment (TME) after TG6050 treatment showed an increase of interferon gamma, CD8+ T cells, M1/M2 macrophages ratio and a drastic decrease of regulatory T cells. Those local modifications were observed together with an enhanced systemic and specific antitumor adaptive immune response. In toxicology studies, the virus did not produce any observable adverse effects in cynomolgus monkeys.    Conclusions: TG6050 allows the delivery of functional IL-12 and @CTLA-4 into tumor resulting in an excellent antitumor activity along with a shift towards an inflamed TME, and a boost of the systemic antitumor T-cells. Toxicological studies in macaques demonstrated the safety of TG6050. Together these results paved the way for clinical evaluation of TG6050 in metastatic non-small cell lung cancer (NCT05788926). Overall design: CT26 tumours treated with the vaccinia virus mTG6050 expressing anti-CTLA-4 and IL-12 (COPTG19859), or untreated