A novel Gorilla-derived oncolytic Adenovirus with natural selective replication in cancer cells

Oncolytic virotherapy exploits viruses to selectively infect and destroy cancer cells while sparing normal tissues and represents a promising strategy in oncology. Human adenovirus type 5 (HAd5), although widely used, shows limited clinical efficacy due to high levels of preexisting immunity and suboptimal tumor selectivity. In this study, we evaluated novel gorilla-derived adenoviruses (GRAd) as alternative oncolytic vectors. Two distinct GRAd groups, GRAdBs and GRAdCs, were characterized for replication and cytopathic activity. GRAd25 (GRAdB group) exhibited robust replication in both tumor and normal cells, whereas GRAd32 (GRAdC group) demonstrated selective replication in tumor cells. To broaden tumor tropism while preserving selectivity, we generated a chimeric GRAd32 vector, GRAd32Fk25, by replacing its native fiber knob with that of GRAd25, potentially shifting receptor usage from CAR to CD46, which is more abundantly expressed in tumor cells. The vector was further armed with a therapeutic antibody by inserting the coding sequence for the single-chain Fc form (scFv-Fc) of EV20, a humanized anti-HER3 antibody, under endogenous viral regulatory control. In vitro analyses showed that GRAd32Fk25 maintained tumor-restricted replication and produced functional EV20 capable of binding HER3 and inhibiting downstream PI3K/Akt signaling. These results indicate that engineered GRAd vectors, exemplified by GRAd32Fk25 armed with EV20, provide a selective and versatile platform for oncolytic virotherapy with potential advantages over HAd5-based approaches.