Synergistic anti-tumor effects of oncolytic virus and anti-programmed cell death protein 1 antibody combination therapy: For suppression of lymph node and distant metastasis in a murine melanoma model.

It is believed that oncolytic viruses (OVs) exert both direct anti-tumor effects by intratumoral injection as well as indirect anti-tumor effects by activating systemic immunity. In phase III clinical trials, OV and anti-programmed cell death-1 (aPD-1) antibody combination therapy showed no significant differences in overall survival and progression-free survival in patients with unresectable advanced melanoma. In the study, OVs can exert only indirect anti-tumor effects in non-injected, systemic lesions. If the tumor is at a stage where both direct and indirect anti-tumor effects of OVs can be expected, OVs may further enhance the therapeutic effect, in addition to the clinically expected therapeutic effect. Therefore, we investigated whether canerpaturev (C-REV) and aPD-1 antibody combination therapy suppresses tumor progression in a murine melanoma model. Our findings showed that the C-REV and aPD-1 antibody combination therapy suppressed tumor progression in a murine melanoma model. The combination therapy stimulated systemic immunity in lymphoid tissues by activating helper T cells and B cells to enhance adaptive and humoral immunity, as well as by increasing effector/memory T cell fractions. Synergistically enhanced systemic anti-tumor effects suppressed lymph node and lung metastases. These findings suggest that direct anti-tumor effects by infecting and destroying cancer cells from within and indirect anti-tumor effects enhanced by the combination therapy worked simultaneously to suppress tumor progression. Our results may provide evidence to support the usefulness of OV and aPD-1 antibody combination therapy as a neoadjuvant therapy in the surgical treatment of melanoma.