Entrance into the present study would be predicated on the confirmation of high grade dysplasia in Barrett's esophagus. If the prospective subject meets all of the inclusion and exclusion criteria set out in the protocol, endoscopic ultrasound of the esophagus would be done. If endoscopic ultrasound shows no invasion into the submucosa the patient would be asked to sign an informed consent. Once entered into the sudy the subject would be given the study drug twice weekly, 3-4 days apart, for 8 weeks. 852A will be supplied in sterile vials by 3M Pharmaceuticals. Five mg of 852A will be mixed with sterile 5% dextrose in water to give a final volume of 30 ml. The patient will promply swallow the study drug after it is mixed. The subject will then assume a recumbent position for 30 minutes in hopes that the medication will stay in contact with the mucosa of the esophagus long enough to get an effect. All doses of the study medication will be given in the principal investigator's clinic. After the first dose is given that patient will stay in the clinic under observation for 4 hours. Observation includes taking the temperature, pulse, and blood pressure every hour. If there are no adverse effects after the first dose, the observation period after subsequent doses will reduced to one hour. Laboratory tests will be repeated 1,2,4 and 8 weeks after the first dose is given. As set out in the study protocol, if the patient has any significant adverse event or laboratory deviation, the subject would be dropped from the study. Throughout the study the subjects will be treated with a double dose of a proton pump inhibitor to control gastric acid reflux.