The purpose of this study is to evaluate the effect of ADX10059 in patients with gastroesophageal reflux disease who are partial responders to proton pump inhibitors

Inclusion Criteria:

• diagnosis of typical GERD
• partial responder to a stable standard clinical symptoms control dose of PPI therapy
• body mass index ≤ 32 kg/m2

Exclusion Criteria:

• exclusively atypical symptoms of GERD
• symptoms that have been shown not to be associated with GERD
• erosive oesophagitis
• treated with a dose of PPI greater than the dose indicated for clinical symptom control of GERD
• hiatus hernia > 3 cm
• current diagnosis of co-existing psychiatric disease
• known clinical significant allergy or known hypersensitivity to drugs
• is pregnant or breast-feeding
• has received sodium valproate or topiramate within 30 days of Screening
• has a history of a significant medical condition that may affect the safety of the patient or preclude adequate participation in the study