Fluorocyclopentenylcytosine (RX-3117) is a novel small molecule nucleoside compound that is incorporated into DNA or RNA of cancer cells and inhibits both DNA and RNA synthesis which induces apoptotic cell death of tumor cells. Fluorocyclopentenylcytosine also mediates the down-regulation of DNA methyltransferase 1 (DNMT1), an enzyme responsible for the methylation of cytosine residues on newly synthesized DNA and also a target for anticancer therapies. Preclinical studies have shown Fluorocyclopentenylcytosine to be effective in both inhibiting the growth of various human cancer xenograft models, including colon, lung, renal and pancreas, as well as overcoming chemotherapeutic drug resistance. Fluorocyclopentenylcytosine has demonstrated a broad spectrum anti-tumor activity against 50 different human cancer cell lines and efficacy in 12 different mouse xenograft models. The efficacy in the mouse xenograft models was superior to that of gemcitabine. In addition, in human cancer cell lines made resistant to the anti-tumor effects of gemcitabine, Fluorocyclopentenylcytosine still retains its full anti-tumor activity. In August 2012, Rexahn reported the completion of an exploratory Phase I clinical trial of Fluorocyclopentenylcytosine in cancer patients conducted in Europe, to investigate the oral bioavailability, safety and tolerability of the compound. In this study, oral administration of Fluorocyclopentenylcytosine demonstrated an oral bioavailability of 34-58% and a plasma half-life (T1/2) of 14 hours. In addition, Fluorocyclopentenylcytosine was safe and well tolerated in all subjects throughout the dose range tested. Fluorocyclopentenylcytosine is in phase I/II clinical trials by Rexahn for the treatment of bladder cancer and pancreatic cancer. This compound was granted Orphan Drug Designation by the U.S. Food and Drug Administration (FDA) for the treatment of patients with pancreatic cancer in September 2014.