RRX-001, also known as ABDNAZ, is a dinitroazetidine derivative with potential radiosensitizing activity. Upon administration, RRx-001 is able to dilate blood vessels, thereby increasing tumor blood flow and thus improving oxygenation to the tumor site. By increasing oxygen levels, these tumor cells may be more susceptible to radiation therapy. Tumor hypoxia is correlated with tumor aggressiveness, metastasis and resistance to radiotherapy. In mouse models, RRx-001 administered intravenously as a single agent was equipotent to cisplatin while better tolerated. RRx-001 also showed activity as a radiosensitizer in both in vitro and in vivo models. The activity of RRx-001 is thought to be associated with a nucleophilic substitution by circulating thiol compounds and covalent binding of RRx-001 to cysteinyl residues in Hb, followed by the generation of nitrogen oxides. During 2014-2015 EpicentRx has launched Phase 2 trials in brain, colorectal, non-small cell lung, small cell lung and cholangiocarcinoma both alone and in combination. The anti-proliferative effects of RRx-001 are not explainable via a single mechanism. RRx-001 exerts its anti-proliferative effect, at least partially, through interference with glucose 6 phosphate dehydrogenase (G6PD), a key enzyme in the pentose phosphate pathway, responsible for maintaining adequate levels of the major cellular reductant, NADPH.