Novel Immune Checkpoint Inhibitor FilC/PD-1 Recombinant Vaccinia Virus Inhibits Hepatocellular Carcinoma

Background: With few therapeutic choices for advanced stages, hepatocellular carcinoma (HCC) continues to be the primary cause of cancer-related death globally. Though still less than ideal in HCC, immunotherapy—especially immune checkpoint drugs aiming at the PD-1/PD-L1 axis—show promise. Combining direct tumor lysis with immune modulation provides a fresh strategy in oncolytic virotherapy with vaccinia virus. Designed to boost anti-tumor immunity by dual checkpoint inhibition and oncolysis, this study assessed the efficacy of FilC/PD-1 recombinant vaccinia virus. Methods: Homologous recombination developed a recombinant vaccinia virus expressing FilC and PD-1 inhibitors. In vitro experiments evaluated in HCC cell lines (Hepa1-6, Vero and NCTC-1496) and mouse models (H22, Hepa1-6) infection efficiency, cytotoxicity and transgene expression. Using BALB/c nude mice (xenograft) and C57BL/6 mice (syngeneic model), in vivo efficacy was assessed in HCC murine models assessing tumor volume reduction, immune cell infiltration, survival rates, and systemic toxicity. Findings: High infection efficiency (88.4% in HepG2), robust viral replication, and substantial oncolytic activity in HCC cells were displayed by the FilC/PD-1 recombinant virus. Compared to the PD-1 inhibitor virus alone, the virus greatly lowered tumor volume (84%) and raised CD8⁺ T cell infiltration (42.8%), hence prolonging survival (68 days). Histopathological study verified low toxicity in main organs. Conclusion: By means of synergistic immune checkpoint inhibition and oncolytic virotherapy, FilC/PD-1 recombinant vaccinia virus significantly increases anti-tumor immunity and slows down HCC growth.