Did you know that PD-1 was discovered in 1992? It is present in both, T- and B-cells and targeting the PD-1 pathways showed a clear evidence of clinical activity and a great promise in a vast range of cancer types, in particular the case of melanoma. J. Weber describes the promising future of this class of agents with many biomarkers available to test the clinical efficacy of PD-1 targeting antibodies.