* Says Contrave may be approved in 2014, if study succeeds
* Contrave could trail rival Vivus diet pill by years
* Orexigen shares jump 87 pct after hours
* Vivus rises 3.8 pct; Arena shares little changed (Adds analyst comment, updates shares of Orexigen, rivals)
By Ransdell Pierson
NEW YORK, Sept 20 (Reuters) - Orexigen Therapeutics Inc (OREX.O) said it plans in 2012 to begin a large heart-safety trial of its experimental Contrave obesity drug, and that favorable results could win over regulators who rejected the pill early this year.
Orexigen, whose shares jumped 87 percent in after-hours trading, said its pill could be approved as soon as 2014 if the study involving thousands of patients resolves concerns about the drug's cardiovascular safety.
"We're still three years and a hundred million dollars away from approval, but we've just gone from a company on the brink of disintegration to something that should yield outsize returns for those willing to be patient," said Jefferies & Co analyst Corey Davis.
Despite improved prospects for Contrave, if approved it could be several years behind Qnexa, a rival weight loss pill being developed by Vivus Inc. (VVUS.O) Vivus last week said it plans to resubmit by October a U.S. marketing application for its product, which the U.S. Food and Drug Administration spurned a year ago, also due to heart-safety concerns.
The FDA in January said it could not approve Orexigen's pill, citing Contrave's cardiovascular effects when used long-term in a population of overweight and obese subjects.
The agency told Orexigen it must first conduct a study "of sufficient size and duration" to demonstrate that the risk of heart attacks, strokes and other major cardiovascular events does not undermine the drug's risk-benefit profile.
Orexigen said on Tuesday that it and its partner Takeda Pharmaceutical Co Ltd (4502.T) are satisfied with design requirements for the required cardiovascular safety trial that had been suggested recently by FDA officials.
San Diego-based Orexigen said the study would require thousands of patients, and that interim results could be obtained less than two years after the trial begins in the first half of 2012.
The company said the FDA notified it Contrave could be approved before the trial is completed, if the interim analysis of data "exclude an unacceptable increased cardiovascular risk."
Contrave combines naltrexone, a medicine used to fight alcohol and drug addiction, with the antidepressant bupropion. It is intended to boost metabolism while curbing appetite and cravings. Japan's Takeda holds North American marketing rights to Contrave.
Before Contrave was rejected in late January, BioMedTracker had projected Contrave sales could reach $1.2 billion by 2018 if the drug reached the market.
Wall Street has also had to scale back initial high hopes for another experimental diet drug pill, Arena Pharmaceuticals Inc's (ARNA.O) lorcaserin. The FDA rejected the product last October due to safety concerns.
Shares of Orexigen rose to $2.75, from a closing price of $1.47 Tuesday on the Nasdaq. But they were trading at more than $11 in late 2010, before Contrave was rejected by the FDA.
Vivus shares rose 3.8 percent to $8.95, from their closing price of $8.62, also on the Nasdaq. Shares of Arena were little changed.