Glucocorticoid-induced TNFR-related protein (GITR) is a member of the TNFR superfamily that is expressed on regulatory and activated T cells, B cells, NK cells, macrophages, and myeloid cells. Expression on tumor cells is less understood. Combination therapy with GITR antibody therapeutics has the potential for synergistic effectiveness by triggering immune response and inducing tumor cytotoxicity.