Imlygic (talimogene laherparepvec) is a genetically modified herpes virus used to treat melanoma. Imlygic was approved by the FDA at October 27, 2015 and by the EMA at December 17, 2015. It was originally developed by BioVex and continued by Amgen after the acquisition of BioVex by Amgen in 2011. Although melanomas shrink due to Imygic, there is no statistically significant benefit in overall survival. In other words, Imlygic does not extend lifes of patients with melanoma. The lack of benefits in combination with the price tag of approximately $65,000 makes Imlygic unpopular to prescribe for doctors.

Imlygic is an oncolytic viral therapy with attenuated life herpes simplex virus type 1 (HSV-1). In HSV-1, two genes are removed and one gene is added. The genes who are removed originally code for the proteins infected cell protein 34.5 (ICP34.5) and infected cell protein 47 (ICP47). ICP34.5 blocks the response of healthy cells to stop replicating and die after viral infection. However, cancer cells lack this system. By removing ICP34.5, HSV-1 cannot replicate and kill normal cells, but in cancer cells they can. ICP47 suppresses an immune response to viral infection. Removing ICP47 should trigger an immune response, in theory. A gene coding for granulocyte colony-stimulating factor (GM-CSF) is inserted to promote an immune response to cancer cells infected by Imlygic. Despite these efforts, clinical evidence for an immune response to cancer cells due to Imlygic is not available.