Results from the Oncovex (GM-CSF) Pivotal Trial in Melanoma (OPTiM) show that a genetically modified version of herpes simplex virus type 1, designated talimogene laherparepvec (T-VEC), shrank melanoma in patients who were in the late stages of the disease. The T-VEC virus works through direct destruction of melanoma cells and contains the gene encoding a cytokine called GM-CSF that helps to initiate an immune response against the melanoma. This is the first prospectively, randomized phase 3 clinical trial of an oncolytic virus cancer immunotherapy to demonstrate a clinical benefit in cancer patients. The Society for Immunotherapy of Cancer Vice President, Howard Kaufman, MD was the principal investigator on the study, which was conducted in four countries with several SITC members as co-investigators, including Drs. Igor Puzanov, Ernest Borden, Brendan Curti, and Theodore Logan. The study consisted of treating one group of patients with T-VEC, while the other group was treated with a control drug, GM-CSF. Sixteen percent of those who were treated with the virus saw their tumors partially or completely shrink for at least six months. This is compared to only 2 percent of patients from the GM-CSF group who saw their tumors shrink partially or completely.