A Study of Indoximod or Placebo Plus Pembrolizumab or Nivolumab for Subjects With Unresectable or Metastatic Melanoma

Inclusion Criteria: * Have histologically- or cytologically-confirmed unresectable stage III or stage IV melanoma not amenable to local therapy * At least one radiologically measurable lesion as per RECIST 1.1 * Have documentation of V600-activating BRAF mutation status or consent to BRAF V600 mutation testing during the screening period. * ECOG performance status 0 or 1 * Ability to ingest oral medications Exclusion Criteria: * Has Ocular Melanoma * Has received prior systemic treatment for unresectable or metastatic melanoma (except BRAF directed therapy). * Has received prior therapy with an anti-PD-1, anti-PD-L1, anti-PD-L2, anti-CD137, or IDO1 inhibitor or any other antibody or drug specifically targeting checkpoint pathways other than anti-CTLA-4 which is permitted in the adjuvant setting. * Has received prior adjuvant therapy, monoclonal antibody or an investigational agent or device within 4 weeks or 5 half-lives (whichever is longer) * Has received prior radiotherapy within 2 weeks of therapy. * Is pregnant or breast-feeding or expecting to conceive or father children within the projected duration of the study, starting with the screening visit through 120 days after the last dose of study treatment. * Patients who have active, chronic, or on active treatment for Hep B or Hep C are excluded.