Malignant Melanoma is considered the most fatal skin tumor albeit it is of the least common malignancies. The intensification of studies on intralesional melanoma therapy directed at specific genetic modification of the herpes simplex virus 1, lead to the manufacturing of T-VEC, the first live virus to be used clinically as a therapeutic agent against malignant disease. Through deletion of HSV-1 gamma 34.5 and alpha 47 genes, this virus became effective. Clinically, the innovative action of T-VEC translates into three outstanding effects: improved durable and overall response rate, a decrease in tumor size and in some cases complete resolution. Overall, with its low toxicity profile and safety, T-VEC is able to offer a promising outcome for patients in late stage melanoma.