UPDATE 1-Novartis, Portola heart drug moves to final tests

* 24,000-patient Phase III elinogrel trial starts Q1 2011

* Trial to study drug in stable coronary artery disease

* Elinogrel a rival to Plavix, as well as Astra's Brilinta

* Drug could be filed for approval late 2014

(Adds comment from doctors, Portola CEO, details)

By Ben Hirschler

STOCKHOLM, Aug 30 (Reuters) - Elinogrel, an experimental blood thinner being developed by Novartis (NOVN.VX) and Portola Pharmaceuticals, is to move into final-stage clinical testing following promising Phase II results.

The new drug targets a market dominated by Sanofi-Aventis (SASY.PA) and Bristol-Myers Squibb's (BMY.N) $9.5 billion-a-year blockbuster Plavix, or clopidogrel. Its backers say it has clinical advantages over Plavix and newer rivals.

Researcher Sunil Rao from the U.S. Duke Clinical Research Institute said on Monday tests showed elinogrel was more potent than Plavix, in both its intravenous and oral forms, without causing significantly increased bleeding risks.

The results of the Phase II trial, involving 652 patients undergoing non-urgent intervention to open clogged arteries, were presented at the European Society of Cardiology congress in Stockholm.

Elinogrel's potential will now be tested in a 24,000-patient Phase III trial that Novartis is expected to initiate in the first quarter of 2011.

That trial will assess two different doses of elinogrel given with aspirin in patients with stable coronary heart disease, compared to aspirin alone, and will last for a average 29 months. If all goes well, the drug could therefore be filed for approval around late 2014.

Rao said the side effects of elinogrel were acceptable for the move into pivotal Phase III testing. Some patients suffered mild and transient dyspnea, or shortness of breath, and some had a temporary increase in liver enzymes, which resolved even when treatment was continued.

MORE TRIALS PLANNED

Portola Chief Executive William Lis told Reuters that further large clinical trials would also be conducted in patients suffering acute coronary syndrome and those having artery-opening procedures.

Final plans for those clinical trials have not yet been concluded but Lis did not rule out that elinogrel might be tested head-to-head against AstraZeneca's (AZN.L) new drug Brilinta, or ticagrelor, which has proved superior to Plavix.

It is in the acute setting that elinogrel could display a key advantage since, unlike rivals, it can been given intravenously as well as a tablet.

"Where (Eli Lilly's (LLY.N)) prasugrel was an advance over clopidogrel, but with excess bleeding, and ticagrelor was an advance over prasugrel ... we hope to advance things one step further," Lis said.

With Plavix already off patent in parts of Europe and set to lose U.S. patent protection in 2012, companies are jostling to promote the advantages of newer, follow-up drugs. All are designed to prevent blood cells called platelets from clumping together to form clots. [ID:nLDE67R07I]

Doctors said the rapid reversability of elinogrel and its availability in intravenous form was attractive, since this meant it took effect very quickly and its blood-thinning effects could be quickly reversed if patients need major surgery.

"This is definitely worth pursuing," said Douglas Weaver of the Henry Ford Heart and Vascular Institute in Detroit, a spokesman for the American College of Cardiology who was not involved in the study.

"There is a niche for an IV (intravenous) drug that could be stopped and this one is great in that it is both an IV and an oral formulation, so you can stay on same drug the whole time."

Another blood thinner given intravenously, the Medicines Co's (MDCO.O) cangrelor, failed in a late-stage clinical study last year.

Novartis shares rose 1.3 percent by 0839 GMT while the STOXX 600 health care index .SXDP gained 0.7 percent. (Editing by David Cowell and Michael Shields)