7. Has a partial response to a PPI defined as having heartburn on 2 to 5 days and regurgitation on at least one day of the last week (Week 4) of a 4 week PPI Run-In Period with esomeprazole 40 mg and an increase of at least 2 symptom days of heartburn in the last week of a 2 week Placebo Run-In Period (4 to 7 symptom days) and at least one symptom day with regurgitation compared with the last week of the PPI Run-In Period.