CHEK1 and head and neck squamous cell carcinoma: However in this study, we now clearly expand on this evidence base by demonstrating that Chk1 and Wee1 inhibition through MK-8776 and MK-1775, respectively are not only effective at enhancing the sensitivity of cell lines, spheroids and patient-derived organoid models of HNSCC to X-ray irradiation, but also can increase the efficacy of PBT at both low and relatively high-LET relative to the Bragg peak.