T-VEC has been approved in Europe for the treatment of unresectable IIIB, IIIC, and IV M1a stage melanoma with no bone, brain, lung, or other visceral disease, based on the results of the OPTiM phase 3 trial, which showed a durable response rate (lasting more than 6 months) and a significantly higher ORR following treatment with intralesional T-VEC in comparison with subcutaneous GM-CSF [110]. The gene discussed is CSF2; the disease is melanoma.