CSF2 and neoplasm: Key design elements of T-VEC include deletion of both copies of RL1 encoding ICP34.5 (designed to restrict viral replication to tumor cells with defective interferon response), deletion of US12 encoding ICP47 (preventing viral suppression of major histocompatibility complex (MHC) class I molecules, resulting in more effective antigen presentation), and insertion of human granulocyte–monocyte colony-stimulating factor (GM-CSF; promoting dendritic cell recruitment with goal of augmenting systemic anti-tumor immunity).