Fianlimab/Cemiplimab

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).

This study is researching an experimental drug called fianlimab (also called REGN3767), combined with a medication called cemiplimab compared against cemiplimab combined with placebo (a placebo looks like a treatment but does not contain any real medicine), collectively called "study drugs" in this form.
The study is focused on participants with head and neck cancers who have not been previously treated for head and neck cancer that has come back or spread to other parts of the body, referred to as recurrent or metastatic (R/M) head and neck squamous cell carcinoma (HNSCC).
The study is looking at several other research questions, including:
* What side effects may happen from taking the study drugs
* How much of each study drug is in the blood at different times
* Whether the body makes antibodies against the study drug(s) individually (which could make the study drugs less effective or could lead to side effects)
* Compatible research to better understand the study drugs and HNSCC