Phase II study evaluating the benefit of the combination of anti-PD1 (pembrolizumab) and anti-CTLA4 (ipilimumab) antibodies in advanced melanoma. The study will determine the response rate of the combination and evaluate other clinical parameters such as progression-free survival and safety of the combination following anti-PD1/L1 antibody. The study will also provide the opportunity to investigate blood or tumor based factors that may predict response to anti-PD1 antibody in combination with anti-CTLA4.