To study of efficacy and safety of Naproxcinod vs. Naproxen and Placebo in the indication of signs and symptoms of osteoarthritis

This is a 53 week study consisting in a 26 week randomized, double-blind, parallel group, multicenter study comparing efficacy and safety of Naproxcinod, Placebo and Naproxen. The first 26 weeks will be followed by a naproxen-controlled treatment period up to 52 weeks and a 1-week post-treatment safety follow-up.

Inclusion Criteria:

• Men and Woman (40 or older) with a diagnosis of primary OA of the knee.
• Must be a current chronic user of NSAIDS or acetaminophen
• Must discontinue all analgesic therapy at Screening

Exclusion Criteria:

• Uncontrolled Hypertension or Diabetes
• Hepatic or Renal Impairment
• Current or expected use of anti-coagulant
• Clinical relevant abnormal ECG
• A history of alcohol or drug abuse
• Candidates for imminent joint replacement
• Participation within 30 days prior to screening in another investigational study