ABSTRACT Hepatocellular carcinoma (HCC) is the third most common cause of cancer deaths worldwide. Whilst immunotherapy combination regimens are now standard of care for advanced HCC, tyrosine kinase inhibitors (TKIs), such as the former first-line agent sorafenib, remain an important choice for those unable to tolerate immunotherapies but provide marginal efficacy. Therefore, we sought to determine whether the efficacy of sorafenib could be enhanced by combining it with human Orthoreovirus , an oncolytic virus possessing immunostimulatory properties. We discovered that uv -inactivated, replication-deficient reovirus, not live virus, significantly extended the survival of mice bearing HCC tumors when combined with sorafenib. This response was characterised by increased intra-tumoral expression of both CCL5 and IFNB, and a skewing of the T-cell ratio in favor of non-canonical, CD4 + cytotoxic T-cells expressing granzyme B, but not perforin. This study highlights both the therapeutic potential of uv -reovirus in TKI-conditioned HCC and the often-overlooked contributions of non-classical immune mechanisms to therapeutic success. One sentence summary A unique therapy combining TKI-conditioning and uv -inactivated reovirus suppresses the growth of hepatocellular carcinomas, mediated by GZMB + CD4 + cytotoxic T-cells.

TKI-conditioned immunotherapy using<i>uv</i>-inactivated reovirus promotes survival in hepatocellular carcinoma, mediated by cytotoxic CD4<sup>+</sup>T-cells

TKI-conditioned immunotherapy usinguv-inactivated reovirus promotes survival in hepatocellular carcinoma, mediated by cytotoxic CD4+T-cells