T-VEC was first tested in a phase I study where it was able to demonstrate GM-CSF expression, tumor apoptosis and necrosis, inflammation and erythema, and viral replication upon analysis of post-treatment biopsies in patients with unresectable stage IIIB, IIIC, or IV melanoma with injectable cutaneous, subcutaneous, or nodal lesions. Here, CSF2 is linked to melanoma.