IDO1 and metastatic melanoma: In a phase 1/2 study of first-in-class immune-modulatory vaccine against indoleamine 2,3-dioxygenase (IDO) and PD-L1, patients with metastatic melanoma were treated with the vaccine targeting immunosuppressive cells and tumor cells expressing IDO and/or PD-L1 (IDO/PD-L1)combined with nivolumab.An objective response rate of 80% was reached, with 43% of complete responses and a median progression-free survival of 26 months in patients with metastatic melanoma treated with the vaccine and nivolumab [19].