 The purpose of this study is to determine if imexon in combination with gemcitabine could improve overall survival as compared to gemcitabine alone in subjects with pancreatic cancer that has spread to other organs such as the liver or lungs. The study will also look at the safety of the combination as compared to gemcitabine alone. Participants in the study will be randomly assigned to either treatment and neither the participant or their doctors will know which treatment they will be receiving. 