The purpose of this study is to determine if pumosetrag is effective in treating Gastroesophageal Reflux Disease (GERD) symptoms in patients who have a history of GERD symptoms and are currently taking an acid suppression therapy, such as a Proton Pump Inhibitor (PPI).

Inclusion Criteria:

• Patients with history of Gastroesophageal Reflux Disease (GERD) symptoms (heartburn, regurgitation, acid taste in mouth).
• Between ages of 18 - 70 inclusive.
• Develop GERD symptoms following ingestion of a refluxogenic meal.
• Able to take a stable Proton Pump Inhibitor (PPI) regimen for duration of study.
• Understand and sign the informed consent form.

Exclusion Criteria:

• Pregnant or lactating women.
• Allergic to pumosetrag or formulation excipients.