Gemcitabine (formerly LY-188011, NSC-613327; LY188011, NSC613327; dFdC; dFdCyd; trade name: Gemzar), an approved antimetabolite anticancer drug, is a potent DNA synthesis inhibitor with potential antineoplastic activity. With IC50s of 50 nM, 40 nM, 18 nM, and 12 nM, respectively, it suppresses the growth of PANC1, MIAPaCa2, BxPC3, and Capan2 cells. Difluorodeoxycytidine di- and triphosphate (dFdCDP, dFdCTP) are the active metabolites of gemcitabine that are produced intracellularly. The deoxynucleotide pool available for DNA synthesis is reduced when dFdCDP inhibits ribonucleotide reductase.