Landmark therapies such as Onyx-015 [a genetically modified adenovirus (AdV)], H101 (AdV variant), and Talimogene laherparepvec (T-VEC), a herpes simplex virus-1 [HSV-1 expressing granulocyte-macrophage colony-stimulating factor (GM-CSF)], have since transformed viruses from pathogens into precision-targeted cancer therapeutics (4, 5). The gene discussed is CSF2; the disease is cancer.