Current treatment for gastroesophageal reflux disease (GERD) confirms an unmet need in patients, based on slow onset of action and an inability to provide 24-hour gastric-acid suppression. Clinical data on AH234844 demonstrates a rapid onset of action, high potency, and prolonged duration of effect. The present study endeavors, in part, to compare lavoltidine to two GERD drugs, NEXIUM and ranitidine.

A three-part study in healthy male volunteers to determine the most effective of four different lavoltidine doses on gastric pH and to compare the most effective dose with NEXIUM (esomeprazole) 40mg for the inhibition of gastric-acid secretion and with ranitidine (300mg/day) for the amount of pharmacodynamic tolerance

Inclusion criteria:

• Subject must have a Body Mass Index (BMI) from 19-30 kg/m2
• Subject does not present with abnormal clinical lab findings
• Subject is able to tolerate a nasogastric pH electrode.

Exclusion criteria:

• Subject is Helicobacter-positive on a C13 urea breath test
• Subject has a baseline median 24-hour gastric pH>3
• For Part B of the study, subjects are CYP 2C19 poor metabolizers.