The purpose of the study is to evaluate the efficacy and safety of arbaclofen placarbil (XP19986) compared to placebo in patients with gastroesophageal reflux disease.

Inclusion Criteria:

1. History of GERD symptoms (e.g. heartburn episodes) at least 3 times per week
2. Discontinuation of drugs used to treat GERD (PPIs, H2-blockers) and/or drugs known to cause GERD symptoms (e.g. nonsteroidal anti-inflammatory drugs [NSAIDs]) for 7 days prior to baseline (Visit 2);
3. Had greater then or equal to 20 postprandial reflux episodes/2 hours recorded using impedance/pH monitoring during Screening/Baseline period (Visit 2)

Exclusion Criteria:

1. History of gastrointestinal disorders other than GERD that may have significantly affected the assessment of reflux episodes or GERD symptoms (e.g. Barrett's Esophagus, active gastric or duodenal ulcer disease, achalasia, scleroderma, etc.).
2. Medical conditions that could have affected assessments of reflux episodes or GERD symptoms (e.g. history of nausea and/or vomiting, neurologic/psychiatric disorders, cardiac disease [e.g. angina], lung disease [e.g. asthma, cough], etc.)