Tanapoxvirus: From discovery towards oncolytic immunovirotherapy.

Insufficiency of standard cancer therapeutic agents and a high degree of toxicity associated with chemotherapy and radiotherapy have created a dearth of therapeutic options for metastatic cancers. Oncolytic viruses (OVs) are an emerging therapeutic option for the treatment of various human cancers. Several OVs, including poxviruses, are currently in preclinical and clinical studies and have shown to be effective in treating metastatic cancer types. Tanapoxvirus (TANV), a member of the Poxviridae family, is being developed as an OV for different human cancers due to its desirable safety and efficacy features. TANV causes a mild self-limiting febrile disease in humans, does not spread human to human, and its large genome makes it a relatively safer OV for use in humans. TANV is relatively well characterized at both molecular and clinical levels. Some of the TANV-encoded proteins that are a part of the virus' immune evasion strategy are also characterized. TANV replicates considerably slower than vaccinia virus. TANV has been shown to replicate in different human cancer cells in vitro and regresses human tumors in a nude mouse model. TANV is currently being developed as a therapeutic option for several human cancers including breast cancer, ovarian cancer, colorectal cancer, pancreatic cancer, retinoblastoma, and melanoma. This review provides a comprehensive summary from the discovery to the development of TANV as an OV candidate for a wide array of human cancers.