Sulofenur is an orally active diarylsulfonylurea derivative patented by American pharmaceutical company Eli Lilly and Co. as an antitumor agent. In preclinical studies, Sulofenur exhibits significant activity against advanced colon adenocarcinoma xenografts intrinsically resistant to virtually all standard chemotherapeutic agents and also had very significant activity against several pediatric tumors grown as xenografts. Clinically, Sulofenur was disappointing, and although some responses were reported in phase I trials this was not confirmed for ovarian cancer in the phase II setting. Toxicity in man was due mainly to methemoglobinemia and anemia, which limited the concentrations of drug that could be achieved to levels well below those shown to elicit a therapeutic response in the xenograft models.