Immunotherapy With Nivolumab or Nivolumab Plus Ipilimumab vs. Double Placebo for Stage IV Melanoma w. NED

Inclusion Criteria: * Stage IV melanoma arising from a primary cutaneous site or metastatic from an unknown primary site with no evidence of disease (NED) after surgery or radiation therapy (conducted within 8 weeks before enrolment) * Signed written informed consent * Known BRAF status * Subjects must be willing and able to comply with scheduled visits, treatment schedule, laboratory testing, and other requirements of the study * Minimum life expectancy of five years excluding their melanoma diagnosis * ECOG performance status of 0 or 1 * Tumor tissue from the resected site of disease must be provided for biomarker analyses. In order to be randomized a subject must have a PD-L 1 expression classification (positive (≥ 5% tumor cells expressing PD-L1) or negative (\< 5% tumor cells expressing PD-L1)). If an insufficient amount of tumor tissue from the resected site is provided for analysis, acquisition of additional archived tumor tissue (block and/or slides) for the biomarker analyses is required. * Prior radiotherapy must have been completed at least 2 weeks prior to study drug administration * Required laboratory values * Negative pregnancy test for female subjects and effective contraception (Pearl-Index \<1) for both male and female subjects if the risk of conception exists Exclusion Criteria: * History of primary uveal or mucosal melanoma * Prior therapy with CTLA4 or PD1 antibodies * The patient has psychiatric or addictive disorders that may compromise his/her abili…