A significant milestone was reached in 2015 when the U.S. Food and Drug Administration approved T-VEC (Talimogene laherparepvec), a genetically modified HSV-1 encoding the granulocyte-macrophage colony-stimulating factor (GM-CSF) for the treatment of unresectable lesions in melanoma patients post-primary surgery [7]. The gene discussed is CSF2; the disease is melanoma.