5-Fluorocytosine

White to off-white powder. Soluble in water. Fluorinated pyrimidine analog. Antimycotic prodrug that is converted by cytosine deaminase to 5-fluorouracil (a widely used cytotoxic drug) and further metabolized to fluorinated ribo- and deoxyribonucleotides. Inhibits DNA and RNA synthesis and interfers with ribosomal protein synthesis. Displays antifungal and antitumor activity. Lately with the development of gene therapy, it has been introduced as a prodrug in combination with the cytosine deaminase suicide gene as antitumor compound, significantly improving survival and reducing tumor size in selected tumors.