PDCD1 and melanoma: These data, and the fact that TIGIT is overexpressed in the microenvironment of several tumor types, such as multiple myeloma, melanoma, gastric cancers and AML, has led to the development of several anti-TIGIT antibodies, all IgG1 with either Fc competent or silent Fcs, and the initiation of Phase I/II clinical studies alone or in combination with PD-1/PD-L1 blockade [154].