This study is for people with a type of cancer called Head and Neck Squamous Cell Carcinoma (HNSCC) that has spread and can't be cured. It compares a drug called **petosemtamab** to a treatment chosen by the doctor. It's for patients who have already tried certain treatments, like anti-PD-1 therapy and platinum-containing therapy, but their cancer kept growing. **PD-1** is a protein that helps keep immune cells from attacking the body, and some cancer treatments target it. "Platinum-containing therapy" refers to a type of chemotherapy that uses platinum to kill cancer cells. **Key Points:** - Participants must be 18 or older, with a life expectancy of at least 12 weeks. - The study involves multiple centers, and patients will need to provide a tumor sample. - It excludes patients with certain medical conditions or treatments shortly before joining. Participants should be aware of the study's demands and ensure they meet all the eligibility criteria. Joining this study may help find better treatments for HNSCC in the future.