GERD is a digestive system disorder characterized by an incomplete closure of the barrier between the stomach and the esophagus, resulting in backward flow of the acidic stomach content into the esophagus. This results in symptoms such as heartburn, an acidic taste in the mouth, and painful swallowing. Over time, damage to the lining of the esophagus and risk of esophageal cancer may occur. Approximately $17.0 billion is spent worldwide each year on GERD and heartburn medications. Approximately 10 percent of the population experiences GERD symptoms daily. While most patients are treated with drugs that reduce the acid content of the stomach, approximately 20 to 25 percent of patients (or 6.0 to 7.5 million people in the United States) do not obtain adequate relief from this type of treatment. Even when the treatment is effective, relief is often incomplete or only temporary. This is one of the large unmet need populations that is targeted with naronapride.