T-VEC was approved following results from the international, phase 3 OncovexGM-CSF Pivotal Trial in Melanoma (OPTiM) trial, in which T-VEC demonstrated significantly improved overall survival (OS) in patients with stage IIIB-IVM1a melanoma treated with T-VEC compared to subcutaneous GM-CSF (median OS 23.3 vs. 18.9 months) [18]. The gene discussed is CSF2; the disease is melanoma.