LT-NS001 is a prodrug of Naproxen, which is inactive as a cox inhibitor while intact and is rapidly metabolized to Naproxen once absorbed. This trial will compare the rate of gastric ulcer by endoscopy over three months in patients with knee osteoarthritis, with patients receiving either LT-NS001 at a dose which provides comparable dose levels of Naproxen, or Naprosyn® 500mg (an approved treatment for OA).

This is a double-blind, double-dummy, active-comparator study of LT-NS001 versus Naprosyn® for 12 weeks in patients aged 45-80 with osteoarthritis of the knee who are candidates for ongoing NSAID therapy. The percentage of patients with a gastric ulcer by endoscopy (EGD) at week 12 will be compared. EGD is performed at screening and months 1, 2, and 3. Secondary objectives include assessment of pain in the affected knee by WOMAC questionnaire to demonstrate non-inferior pain control using LT-NS001 as compared to Naprosyn®. Information about gastrointestinal pain and tolerability will be collected.

The length of the study is up to 19 weeks with a 2-3 week screening period, a 12 week treatment period and a 4 week post treatment monitoring period.

Inclusion Criteria:

• Osteoarthritis of knee
• Appropriate candidate for chronic NSAID therapy due to moderate or severe pain on most days in the 28 days before screening for study.

Exclusion Criteria:

• Pregnant/Nursing women
• History of GI bleeding, perforation or obstruction
• A documented symptomatic GI ulcer during past 5 years
• Presence of GI ulcer or more than 2 erosions on screening endoscopy
• Allergy to naproxen (or naproxen intolerance), acetylsalicylic acid, or other NSAID drug