PDCD1 and metastatic melanoma: Similarly, whilst the level of circulating mo-MDSC and PMN-MDSC subsets were not shown to be affected by PD-1 blockade in several clinical studies [97, 183, 184], high-dimensional single-cell analysis applied to the peripheral blood of metastatic melanoma patients treated with an anti-PD-1 revealed a striking remodeling of the myeloid compartment 12 weeks after initiation of therapy [183].