Double targeting oncolytic herpes simplex virus type 1 (oHSV-1) exhibits effective antitumor activity against EpCAM-expressing cancer cells

Abstract Oncolytic virotherapy is a new modality of immunotherapy using spontaneously occurring or genetically engineered viruses to selectively replicate in and kill cancer cells, no harming normal cells. Currently, various oncolytic herpes simplex virus (oHSVs) with enhanced tumor targeting, antitumor efficacy, and safety have been explored in many different models, and on a range of tumor targets. It has been a difficult task to completely retarget HSV to cancer-specific antigens at the plasma membrane of selected tumors, while maintaining the fully lytic potential of HSV. This approach achieved by a deep knowledge of virus natural receptor recognition, binding, and entry mechanisms. Two strategies have been employed including the incorporation of single-chain antibodies (scFv) into gD, gC or gH and the use of soluble adapter molecules that are capable of binding to both HSV and the specific receptor on the target cell. In the previous study, we first reported that HSV could retarget to gastric carcinoma cells by HVEM-CEA adapter molecule. Although we have been shown reasonable efficiency of retargeted cell transduction in vitro and in vivo, it required purification of the adapter protein and continuous addition to the virus prior to infection. To overcome the limitations of adapter molecules, we developed a self-retargeting system by incorporation of adapter expression cassette into the HSV genome that enables the sustained secretion of adapter protein while the viral replication in infected tumor cells. Furthermore, to strengthen the retargeting modality, we constructed a novel, double targeted oHSV, carries no deletion/attenuation, consisting of self-retargeting adapter and modified gH to EpCAM. Our results show that the initial infection and subsequent viral spread depend on cellular EpCAM expression. When injected intravenously (i.v.), they caused no harm to tumor-free mice up to the maximum tested dosage (2 x 108 PFU). When a single intratumoral dose of double targeting oHSV (2 x 106 infectious units) were administered in a xenograft model they rendered 80% of mice tumor-free. Our findings suggest that the double retargeting platform of HSV carrying self-retargeting adapter and modified gH may be potent in cancer-specific cell killing and thus useful for the treatment of EpCAM expressing various cancers. Citation Format: Hyunjung Baek, Hyun-Yoo Joo, Eun-Ran Park, Chun-Seob Ahn, Sujung Lee, Hyeri Kim, Mihee Han, Bora Kim, Heechung Kwon. Double targeting oncolytic herpes simplex virus type 1 (oHSV-1) exhibits effective antitumor activity against EpCAM-expressing cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3292.