This study is researching an investigational drug called REGN7075 by itself and in combination with cemiplimab with or without chemotherapy. The study is focused on patients with certain solid tumors that are in an advanced stage. The aim of the study is to see how safe and tolerable REGN7075 is by itself and in combination with cemiplimab (with or without chemotherapy), and to find out what is the best dose of REGN7075 to be given to patients with advanced solid tumors when combined with cemiplimab (with or without chemotherapy). Another aim of the study is to see how effective REGN7075 by itself, or in combination with cemiplimab (with or without chemotherapy), is at treating cancer patients.

The study is also looking at:

* Side effects that may be experienced by people taking REGN7075 by itself and in combination with cemiplimab with or without chemotherapy
* How REGN7075 works in the body by itself and in combination with cemiplimab with or without chemotherapy
* How much REGN7075 is present in the blood when given by itself and in combination with cemiplimab with or without chemotherapy
* To see if REGN7075 by itself and in combination with cemiplimab with or without chemotherapy works to treat cancer by controlling the proliferation of tumor cells to shrink the tumor

This phase II trial studies the effect of pembrolizumab alone compared to the usual approach (chemotherapy \[cisplatin and carboplatin\] plus radiation therapy) after surgery in treating patients with head and neck squamous cell carcinoma that has come back (recurrent) or patients with a second head and neck cancer that is not from metastasis (primary). Radiation therapy uses high energy radiation or protons to kill tumor cells and shrink tumors. Cisplatin is in a class of medications known as platinum-containing compounds. It works by killing, stopping or slowing the growth of cancer cells. Carboplatin is also in a class of medications known as platinum-containing compounds. It works in a way similar to the anticancer drug cisplatin, but may be better tolerated than cisplatin. Carboplatin works by killing, stopping or slowing the growth of cancer cells. Immunotherapy with monoclonal antibodies, such as pembrolizumab, may help the body's immune system attack the cancer and may interfere with the ability of tumor cells to grow and spread. Giving pembrolizumab alone after surgery may work better than the usual approach in shrinking recurrent or primary head and neck squamous cell carcinoma.