Pharmaceutical company Pozen Inc. saw its stock soar Thursday on the news that the FDA accepted its primary endpoint for two late-stage clinical trials PN 400, its arthritis drug. In 2006, Pozen and AstraZeneca signed a deal to co-develop PN 400, by which AstraZeneca would pay Pozen $40 million upfront and $160 million for certain development and regulatory milestones.

But an internal review the Food and Drug Administration started in October put into question whether Pozen and AstraZeneca could use the PN400 test results to ask for regulatory approval of the medicine. After completing its review, the FDA informed Pozen that no changes were necessary to submit the PN400 test results for regulatory review, according to documents filed with the Securities and Exchange Commission Thursday.

PN 400, an investigational product under development by POZEN and AstraZeneca, is a fixed dose combination of enteric-coated naproxen with immediate release esomeprazole for the treatment of the signs and symptoms of osteoarthritis, rheumatoid arthritis, and ankylosing spondylitis in patients who are at risk of developing NSAID associated gastric ulcers.

Pozen has already completed two studies of its experimental arthritis drug PN 400 that showed reduction of ulcers. Pozen said it plans to move ahead with a similar study of PA32540, which is designed to deliver the blood thinning affects of aspirin without causing ulcers.