The Oncolytic virus VT1092M and an Anti-PD-L1 antibody synergize to induce systemic antitumor immunity in a murine bilateral tumor model

•VT1092 is an oncolytic herpes simplex virus armed with interleukin-12.•VT1092M combined with ICIs targeting PD-1, PD-L1, or TIM3 was first explored.•VT1092M combined with PD-L1 blockade induces abscopal and tumor-specific effects.•CD8+T cells play a crucial role in mediating potent systemic antitumor immunity. This study investigated the synergistic potential of an oncolytic herpes simplex virus armed with interleukin 12 (VT1092M) in combination with immune checkpoint inhibitors for enhancing antitumor responses. The potential of this combination treatment to induce systemic antitumor immunity was assessed using bilateral subcutaneous tumor and tumor re-challenge mouse models. The antitumor efficacy of various OV and ICI treatment combinations and the underlying mechanisms were explored through diverse analytical techniques, including flow cytometry and RNA sequencing. Using VT1092M, either alone or in combination with an anti-PD-L1 antibody, significantly reduced the sizes of both the injected and untreated abscopal tumors in a bilateral tumor mouse model. The combination therapy demonstrated superior antitumor efficacy to the other treatment conditions tested, which was accompanied by an increase in T cell numbers and CD8+T cell activation. Results from the survival and tumor re-challenge experiments showed that the combination therapy elicited long-term, tumor-specific immune responses, which were associated with tumor clearance and prolonged survival. Immune cell depletion assays identified CD8+T cells as the crucial mediators of systemic antitumor immunity during combination therapy. In conclusion, the combination of VT1092M and PD-L1 blockade emerged as a potent inducer of antitumor immune responses, surpassing the efficacy of each monotherapy. This synergistic approach holds promise for achieving robust and sustained antitumor immunity, with potential implications for preventing tumor metastasis in patients with cancer. [Display omitted]