Strategically engineering an oncolytic herpes simplex virus to improve systemic delivery

Oncolytic virotherapy (OV) has emerged as a promising cancer treatment strategy, utilizing viruses to selectively infect and destroy tumor cells while simultaneously stimulating anti-tumor immunity. OV has also been shown to modulate the tumor immune microenvironment, enhancing the efficacy of immunotherapy. Despite the recent regulatory approvals of oncolytic viruses such as T-VEC (JS1/34.5-/47-/GM-CSF), Oncorine (H101), and Teserpaturev (G47Δ), the clinical impact of OV remains limited by its reliance on intratumoral administration. Systemic delivery is essential for effectively treating metastatic and inaccessible tumors but is hindered by two major challenges: rapid clearance by the mononuclear phagocyte system (MPS) and neutralization by antiviral antibodies. To overcome these barriers, we developed FusOn-SD, an enhanced version of FusOn-H2 engineered for systemic delivery. Our strategy integrates both genetic and adaptive modifications: (1) incorporating the extracellular domain (ECD) of CD47 to evade MPS-mediated clearance and (2) serially passaging the virus in immune sera to enhance resistance to neutralizing antibodies. Preclinical studies demonstrate that FusOn-SD efficiently reaches tumor sites following systemic administration, exhibiting enhanced immune evasion and oncolytic potency. These findings position FusOn-SD as a promising candidate for advancing OV beyond localized injections, with the potential to transform virotherapy into a viable treatment for metastatic cancer.