Oxford Pharmascience Ltd (the Sponsor) is developing a new naproxen tablet formulation (the study drug, OXP005), for the potential treatment of rheumatic and painful conditions. The study will compare the study drug to an already marketed formulation of prescription strength naproxen (Naprosyn® the reference product) by looking at the relative impact of both products on gastroduodenal (GD) irritation by performing a specialist procedure called an endoscopy (or more specifically, a gastroscopy). The safety and tolerability of the study drug will also be assessed.

Inclusion Criteria:

• Healthy male or female subject
• Healthy, normal upper GI tract as indicated by no ulcers or erosions at baseline, as assessed by the gastroenterologist conducting the endoscopy (ie Lanza score of 0 in both the stomach and duodenum)
• H. pylori negative

Exclusion Criteria:

• Clinically significant abnormal laboratory parameters
• Any clinically significant diseases or conditions affecting the haematopoietic, cardiovascular, renal, hepatic, endocrine, pulmonary, centralcnervous, immunological, dermatological, GI or any other body system