The combination of DNA-damaging therapies and inhibitors of the DDR is already being investigated for HNSCCs in clinical trials (e.g., NCT03022409: ceralasertib (ATR), NCT02567422: berzosertib (ATR), NCT04576091: elimusertib (ATR), or NCT02555644 and NCT02555644: prexasertib (Chk1)); however, so far, only concerning tumor cytotoxicity as the major endpoint, e.g., through mechanisms of reproductive cell death or apoptosis [44,45,46]. Here, CHEK1 is linked to neoplasm.