S-Tenatoprazole-Na (STU-Na), a new drug currently under clinical development, belongs to a class of drugs, called proton pump inhibitors (PPls). Some PPIs are already commercially available. STU-Na will be used for treatment of acid related diseases (gastroduodenal ulcers, erosive or ulcerative esophagitis due to gastroesophageal reflux disease). This study evaluates the degree of acid suppression by different doses of STU-Na. The degree of acid suppression is considered to be correlated with clinical efficacy.

In this study four dosages of STU-Na (30 mg, 60 mg, 90 mg, and 120 mg) will be tested in each volunteer. First, one of the dosages will be orally administered for five days. Then, a nine to sixteen day period without study drug administration will follow prior to the administration of the next dosage, for again five days. Each volunteer will have a total of four study drug administration periods.

After the last study drug intake in period 1, 2 and 3 pharmacokinetic blood sampling will be done for four days. After the last study drug intake in period 4 pharmacokinetic blood sampling will be done for five days. Pharmacokinetic blood sampling consists of several blood draws over a pre-determined time period. The pharmacokinetic blood sampling measures the medication concentration in the blood at pre-defined time points.

After the last study drug intake in period 1, 2, 3, and 4, gastric acidity will be measured for 24 hours by means of a thin tube that will be inserted into the stomach through the nostril to evaluate the efficacy of the different dosages of STU-Na.

S-Tenatoprazole-Na (STU-Na), a new drug currently under clinical development, belongs to a class of drugs, called proton pump inhibitors (PPls). Some PPIs are already commercially available. STU-Na will be used for treatment of acid related diseases (gastroduodenal ulcers, erosive or ulcerative esophagitis due to gastroesophageal reflux disease). This study evaluates the degree of acid suppression by different doses of STU-Na. The degree of acid suppression is considered to be correlated with clinical efficacy.

In this study four dosages of STU-Na (30 mg, 60 mg, 90 mg, and 120 mg) will be tested in each volunteer. First, one of the dosages will be orally administered for five days. Then, a nine to sixteen day period without study drug administration will follow prior to the administration of the next dosage, for again five days. Each volunteer will have a total of four study drug administration periods.

After the last study drug intake in period 1, 2 and 3 pharmacokinetic blood sampling will be done for four days. After the last study drug intake in period 4 pharmacokinetic blood sampling will be done for five days. Pharmacokinetic blood sampling consists of several blood draws over a pre-determined time period. The pharmacokinetic blood sampling measures the medication concentration in the blood at pre-defined time points.

After the last study drug intake in period 1, 2, 3, and 4, gastric acidity will be measured for 24 hours by means of a thin tube that will be inserted into the stomach through the nostril to evaluate the efficacy of the different dosages of STU-Na.

Inclusion Criteria:

• Healthy male volunteers aged 18 to 55 years inclusive
• Able to understand the nature of the study and to give written informed consent
• Able to communicate well with the investigator himself or his/her representatives
• Able not to smoke during each hospitalization
• Normal physical examination at the screening visit
• Body Mass Index between 18 kg/m² and 35 kg/m² at the screening visit
• Normal blood pressure and heart rate measured under standardized conditions at the screening visit after at least 5 minutes of rest in a supine position: SBP within 90 and 140 mmHg, DBP within 40 and 85 mmHg, and HR within 40 to 85 bpm
• Normal 12-lead electrocardiogram at screening visit recorded after at least 5 minutes of rest: PR within 120 and 200 ms, QRS below or equal to 120 ms, and QTc below or equal to 440 ms
• Laboratory results within the normal ranges or considered not being of clinical relevance by the investigator

Exclusion Criteria:

• Vegetarians
• Positive to H. pylori by 13C urea breath test or stool antigen test at screening visit
• Contra-indication to proton pump inhibitors treatment
• Previous participation in a trial with PPIs within 3 months
• Current or historical evidence of clinically relevant cardiovascular, neurological, hematological, hepatic, gastrointestinal, renal, pulmonary, endocrinological, metabolic or psychiatric disease
• Any other acute or chronic disease which could influence the volunteer's health and/or the study results
• Presence or history of malabsorption or any gastrointestinal surgery except appendectomy or hernia repair
• Receipt of medication (including 'over the counter' preparations) within two weeks of dosing
• Use of enzyme inducers or enzyme inhibitor drugs within the last three months before the first drug administration
• Participation in a clinical trial involving receipt of a licensed (marketed) medicinal product or of an unlicensed (investigational) medicinal product within one month before the study
• Past or current drug exposure amounting to drug abuse or addiction
• Past or current alcohol exposure amounting to alcohol abuse or addiction; (i.e. > 28 units per week for males, where 1 unit = one measure of spirit (25 mL), one glass of wine (125 mL) or ½ pint beer)
• Currently smoke >10 cigarettes per day
• Donation of blood or any other major blood loss (>500 mL) within three months before the study
• Unwilling or unable to comply with the study protocol for any reason or in the opinion of the investigator should not participate in the study
• Positive test for hepatitis B surface antigen, hepatitis C antibody, HIV1 or HIV2 antibody at screening
• Known allergy or intolerance to lactose
• Known allergy or intolerance to any other compound in the study drug or any other closely related compound