A Randomized, Double-blind, Placebo-controlled, 2-arm Phase III Study to Assess Efficacy and Safety of Xevinapant and Radiotherapy Compared to Placebo and Radiotherapy for Demonstrating Improvement of Disease-free Survival in Participants With Resected Squamous Cell Carcinoma of the Head and Neck, Who Are at High Risk for Relapse and Are Ineligible for High-dose Cisplatin (XRAY VISION)

The purpose of this study is to demonstrate the superior efficacy of Xevinapant (Debio 1143) versus placebo when added to radiotherapy in the treatment of high-risk participants with resected locally advanced squamous cell carcinoma of the head and neck (LA SCCHN) who are ineligible to receive cisplatin-based chemoradiation concurrently. Study details include: Study duration: Participants will be followed until the last on-study participant reaches his/her 60-month post-randomization visit, a decision to end the study has been triggered, or until premature discontinuation from study, whichever occurs first. Treatment duration: 18 weeks, consisting of six 3-week cycles. Health measurement/observation: Improved Disease-Free Survival. Visit frequency: Weekly visit during combination therapy period, once every 3 weeks during monotherapy period, and every 3, 4, or 6 months during the Disease-Free Survival Follow-up period in Year 1, 2 and 3, or 4 and 5 (with telephone contact in between), respectively, and every 3 months (telephone visits allowed) during the Overall Survival Follow-up period.