CSF2 and melanoma: T-VEC encoding GM-CSF was the first OV approved by the US FDA for the treatment of melanoma in October 2015.20 Injection with T-VEC induces local and systemic antigen-specific T-cell responses and decreases the number of Tregs, suppressor T cells (Ts), and MDSCs in injected lesions, ultimately leading to an improved durable response rate (DRR) and a long-lasting complete response (CR).111,163 Despite T-VEC, GM-CSF is widely used for other types of OVs (HSV,110 VV,164 VSV,165 MV,166 AdV,167,168 and RV169) to enhance its antitumor efficacy.