Xevinapant (Debio 1143, Debiopharm/Merck KGaA) is an orally applicable Smac mimetic which has been shown to enhance RT in HNSCC cell lines in vitro and to sensitize HNSCC xenografts for RT in vivo via apoptosis induction and increased tumor necrosis factor alpha (TNFα) expression [109]. Here, TNF is linked to head and neck squamous cell carcinoma.