TAS-106: Preclinical, clinical and beyond

5-Fluorouracil, other fluorinated pyrimidines and their derivatives are frequently used in chemotherapy to treat different types of cancer. These agents are classified as metabolic antagonists that target the DNA synthesis phase of the cell cycle. Therefore, these agents are more effective in rapidly growing tumors than in more indolent cancers. In order to develop new drugs that interfere with both DNA and RNA synthesis, the metabolism of pyrimidines was investigated, and new compounds were developed by the molecular design method, which analyzes the biochemical properties of the compounds. The nucleoside 3′-C-ethynylcytidine (TAS-106) was designed to inhibit RNA synthesis by blocking RNA polymerases I, II, and III, which occur throughout the cell cycle except for the M phase. This review article discusses the antitumor activity of TAS-106 as a single agent or in combination therapy with the focus on preclinical and clinical findings.