UPDATE 1-NicOx at 6-month high as third trial backs drug

* Third pivotal study endorses pain drug naproxcinod

* Pooled results of all three trials due in coming weeks

* Shares up 18 percent at six-month high

(Adds analyst comment, shares, background)

LONDON, Nov 24 (Reuters) - French biotech company NicOx (NCOX.PA) said on Monday its experimental arthritis treatment naproxcinod had proved to be safe and effective -- without raising blood pressure -- in a third pivotal Phase III study.

The positive outcome lifted shares in the group 18 percent to 11.07 euros by 0920 GMT, after touching a six-month high of 11.80.

NicOx will now pool the blood pressure data from all three Phase III studies, as previously agreed with the U.S. Food and Drug Administration, and disclose the top-line results of this statistical analysis in the coming weeks.

Piper Jaffray analyst Sam Fazeli said the result of the latest study in patients with osteoarthritis in their hips was "a significant relief" as studies in hip pain historically have a high risk of failure.

Existing non-steroidal anti-inflammatory agents (NSAIDs) like naproxen and ibuprofen can raise blood pressure, which is a side effect of particular concern among elderly people for whom the drug is intended.

The French firm is preparing for the possible launch of its potential blockbuster drug in 2010 and is looking for a partner to help market it. The drug's ability to tackle blood pressure could set it aside from other treatments.

Naproxcinod would be the company's first drug on the market and become the only branded rival to Pfizer's (PFE.N) Celebrex which had third quarter sales of $625 million.

The French firm expects to submit naproxcinod for U.S. marketing approval by mid 2009. (Reporting by Ben Hirschler; Editing by Sharon Lindores)