2',2'-Difluorodeoxyuridine-13C,15N2 (dFdU-13C,15N2) is a 13C- and 15N-labeled compound. 2,2-Difluorodeoxyuridine (dFdU) is the main metabolite of Gemcitabine (HY-17026). 2,2-Difluorodeoxyuridine causes a concentration- and schedule- dependent radiosensitising effect in vitro. 2,2-Difluorodeoxyuridine arrests cell cycle at the early S phase and induces apoptosis in cancer cells[1][2][3][4].