UPDATE 2-NicOx says arthritis drug helps bloodpressure

* Reports positive naproxcinod test results

* Shares surge 20 percent

(Adds analyst, updates shares, adds more detail)

By Caroline Jacobs)

PARIS, Nov 4 (Reuters) - NicOx (NCOX.PA) said its experimental arthritis treatment naproxcinod proved to be more beneficial for blood pressure than a traditional painkiller, boosting its share price by as much as 44 percent on Tuesday.

Existing non-steroidal anti-inflammatory agents (NSAIDs) like naproxen and ibuprofen can raise blood pressure, which is a side effect of particular concern among people with osteoarthritis 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 current treatments.

A clinical trial compared NicOx's painkiller naproxcinod in three different doses to naproxen in 118 osteoarthritis patients with controlled hypertension. Good safety and tolerability were shown by all naproxcinod doses, NicOx said.

"These excellent results are an important addition to the consistent data we are accumulating on naproxcinod's potentially non-detrimental blood pressure profile and its clear differentiation from naproxen," Chairman and Chief Executive Michele Garufi said in a statement.

NicOx will publish more clinical trial data on naproxcinod this year -- another blood pressure study and a trial on osteoarthritis in the hip -- which 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.

"The results are positive," said Jefferies International analyst Robin Campbell. He has a "buy" rating on the stock with a price target of 11 euros.

NicOx shares rose 38.1 percent to 10.36 euros by 1155 GMT, yielding a market capitalisation of around 354 million euros.

"A lot depends on the policy of a future partner and abiltiy to be in position to market the product in the U.S.," Campbell said.

NicOx's Garufi told Reuters in September the company was in talks with several candidates to help sell naproxcinod in the United States and a deal could be reached next summer or earlier.

Naproxcinod seeks to treat arthritis in the knee and hip while protecting the stomach and keeping blood pressure under control or lowering it. That would give it a competitive edge over other anti-inflammatory drugs linked to heart problems and stomach ulcers.

Merck's (MRK.N) Vioxx made annual sales of $2.5 billion before the arthritis and chronic pain pill was withdrawn from U.S. drugstores nearly four years ago, when a Merck study showed that long-term users had twice the risk of heart attack and stroke.

Pfizer has a 2.86 percent stake in NicOx while Garufi and co-founder doctor Elizabeth Robinson have a combined stake of three percent.

NiCox was founded in 1996 in Sophia Antipolis, southern France, and focuses on the use of medical properties of nitric oxide. (Reporting by Caroline Jacobs; Editing by Chris Wickham)