Additional Study Information: This research study is being done to see if the study drug, IMCgp100, works and is safe as treatment for subjects with uveal melanoma who also test positive for HLA-A*0201. In this study IMCgp100 will be compared to three standard treatments: dacarbazine (a chemotherapy drug), ipilimumab (an immunotherapy drug), or pembrolizumab (an immunotherapy drug). This study is designed to find out if IMCgp100 can make subjects with uveal melanoma live longer and if IMCgp100 can make uveal melanoma tumors stop growing (or shrink).