This study is researching the long-term effects of a combination of experimental drugs called fianlimab and cemiplimab. The study is being conducted in patients with advanced skin cancer (melanoma) who had previously been treated with fianlimab and cemiplimab in the study called R3767-ONC-1613 (NCT03005782). The aim of the current study is to see how safe and effective the study drugs are in a long-term follow-up. No study drug will be given during this study. Cancer status will be monitored, in addition to routine care. The study is also collecting information about general health status, and other treatments that may have been received since participation in study R3767-ONC-1613 (NCT03005782).