CJ-023,423 is a new medication being developed as an anti-inflammatory agent for the treatment of the signs and symptoms of osteoarthritis (OA). The purpose of this study is to evaluate whether patients treated with CJ-023,423 for 7 days (14 doses) have fewer gastrointestinal ulcers compared to patients treated with naproxen and placebo.

Inclusion Criteria:

• Is a healthy adult 18 to 75 years of age, inclusive; healthy is defined as no clinically relevant abnormalities identified as detailed medical history, full physical examination, including blood pressure [BP] and pulse rate [PR]measurement, 12-lead electrocardiogram [ECG], and clinical safety laboratory tests
• If female and of childbearing potential (includes women who have been postmenopausal for < 2 years ), must be using adequate contraception, must not be lactating and must have had a negative serum pregnancy test at Screening and a negative urine pregnancy test result within 24 hours prior to receiving study drug. The site investigator must ensure that female subjects are not pregnant prior to receiving the first dose of drug;

Exclusion Criteria:

• Endoscopic evidence of inflammation, ulceration, erosion, petechiae, or active bleeding in the esophagus, stomach, pyloric channel, or duodenum at the baseline/ randomization (Day 1) endoscopy (Mucosal Grading Scale score >0);
• Active GI disease (e.g. inflammatory bowel disease), a history of gastroduodenal ulcers or bleeding, or a history of any gastric or duodenal surgery;