This phase II trial compares the safety, side effects and effectiveness of anti-lag-3 (relatlimab) and anti-PD-1 blockade (nivolumab) to standard of care lomustine for the treatment of patients with glioblastoma that has come back after a period of improvement (recurrent). Relatlimab is a monoclonal antibody that may interfere with the ability of tumor cells to grow and spread. A monoclonal antibody is a type of protein that can bind to certain targets in the body, such as molecules that cause the body to make an immune response (antigens). Immunotherapy with monoclonal antibodies, such as nivolumab, may help the body's immune system attack the tumor, and may interfere with the ability of tumor cells to grow and spread. Lomustine is a chemotherapy drug and in a class of medications called alkylating agents. It damages the cell's deoxyribonucleic acid and may kill tumor cells. Giving relatlimab and nivolumab may be safe, tolerable, and/or effective compared to standard of care lomustine in treating patients with recurrent glioblastoma.

This study is researching an investigational drug called marlotamig (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 marlotamig is by itself and in combination with cemiplimab (with or without chemotherapy), and to find out what is the best dose of marlotamig 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 marlotamig 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 marlotamig by itself and in combination with cemiplimab with or without chemotherapy
* How marlotamig works in the body by itself and in combination with cemiplimab with or without chemotherapy
* How much marlotamig is present in the blood when given by itself and in combination with cemiplimab with or without chemotherapy
* To see if marlotamig 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
* Whether the body makes antibodies against the study drugs (marlotamig and cemiplimab) (which could make the drug less effective or could lead to side effects)