3,4,5,6-Tetrahydrouridine, is a derivative of Uridine (U829910). Tetrahydrouridine (THU), is a potent inhibitor of cytidine. It inhibits cell proliferation through cell cycle regulation regardless of cytidine deaminase expression levels deaminase (CDA), and thus can be used as a potential and promising treatment for tumors with highly expressed CDA.