This study looks at using a drug called **tolinapant** with *radiation therapy* for people with advanced head and neck cancer who cannot use another drug called cisplatin. **Tolinapant** is a medicine that may help stop cancer cells from growing by blocking certain enzymes needed for cell growth. *Radiation therapy* is a treatment that uses high-energy x-rays to kill cancer cells. By combining **tolinapant** with *radiation therapy*, more cancer cells might be killed.

Participants will receive *radiation therapy* over 6-7 weeks and take **tolinapant** by mouth for 7 days during weeks 1, 3, 5, and 7. After treatment, there will be follow-ups at 1, 3, 6, 12, and 24 months.

• Participation involves 6-7 weeks of treatment.
• Follow-up visits are required after the treatment ends.
• The study checks the safety and effects of the treatment.

This study is for adults who haven’t had this cancer treatment before and cannot take cisplatin. Participants cannot have had prior head and neck radiation or certain health issues. Women must not be pregnant, and both men and women should use birth control during the study.