STING activator 2′3′‐cGAMP enhanced HSV‐1‐based oncolytic viral therapy

Oncolytic viruses (OVs) can selectively replicate in tumor cells and remodel the microenvironment of immunologically cold tumors, making them a promising strategy to evoke antitumor immunity. Similarly, agonists of the stimulator of interferon genes (STING)‐interferon (IFN) pathway, the main cellular antiviral system, provide antitumor benefits by inducing the activation of dendritic cells (DC). Considering how the activation of the STING‐IFN pathway could potentially inhibit OV replication, the use of STING agonists alongside OV therapy remains largely unexplored. Here, we explored the antitumor efficacy of combining an HSV‐1‐based OV, C‐REV, with a membrane‐impermeable STING agonist, 2′3′‐GAMP. Our results demonstrated that tumor cells harbor a largely defective STING‐IFN pathway, thereby preventing significant antiviral IFN induction regardless of the permeability of the STING agonist. In vivo , the combination therapy induced more proliferative KLRG1‐high PD1‐low CD8 + T‐cells and activated CD103 + DC in the tumor site and increased tumor‐specific CD44 + CD8 + T‐cells in the lymph node. Overall, the combination therapy of C‐REV with 2′3′‐cGAMP elicited antitumor immune memory responses and significantly enhanced systemic antitumor immunity in both treated and non‐treated distal tumors.