AstraZeneca and partner Pozen have posted promising late-stage data on a potential treatment for arthritis which combines the pain reliever naproxen with the blockbuster antiulcerant Nexium.

The firms announced results from two Phase III studies of PN 400 (naproxen and esomeprazole), both of which showed that patients on the combo experienced statistically significantly fewer endoscopically-confirmed gastric ulcers than those taking naproxen alone. Around 400 subjects were treated in each of the trials, the full results of which “will be published in a timely manner”, AstraZeneca said. PN 400 is being developed for the treatment of osteoarthritis, rheumatoid arthritis, and ankylosing spondylitis in patients who are at risk of developing gastric ulcers.

One potential problem is that the US Food and Drug Administration recently informed Pozen that it is conducting an internal review on the acceptability of using endoscopic gastric ulcers as a primary endpoint in clinical studies. The agency has not indicated when that review will be completed, although it has scheduled an internal meeting to review the matter during the first quarter of next year.

AstraZeneca noted that two additional Phase III studies are still ongoing and once the entire PN 400 clinical programme is completed, it will make a final determination regarding regulatory filing. That is currently planned for mid-2009.