An analogue of the nucleoside deoxycytidine with potential antineoplastic activity. Nucleoside analogue TAS-109 is incorporated into DNA and directly inhibits the activity of DNA polymerase, which may result in inhibition of DNA replication and cell cycle arrest in the S and G2/M phases, DNA fragmentation, and tumor cell apoptosis. Check for active clinical trials using this agent. (NCI Thesaurus)