Description_x000D_ Biochem/physiol Actions_x000D_ NCT-501 is a potent and selective inhibitor of Aldehyde dehydrogenase ALDH1A1, a dehydrogenase that has been found to be elevated in certain cancers and in cancer stem cells. NCT-501 had an IC50 value of 40 nM and was found to be 1000-fold selective for ALDH1A1 over other ALDH enzymes and other dehydrogenases. NCT-501 treatment of head and neck squamous-cell carcinoma (HNSCC) explants in combination with cisplatin resulted in a significant decrease in proliferating cells.