* Biotech to make case for approval of weight loss drug
* FDA reviewers cite safety issues though Contrave works
* Contrave sales could reach ${esc.dollar}1.2 billion by 2018
* Outside FDA advisers to vote on pill later on Tuesday
* Orexigen shares down 36 percent this year
By Susan Heavey
WASHINGTON, Dec 7 (Reuters) - The last of a trio of new weight loss drugs, Orexigen Therapeutics Inc's <OREX.O> Contrave, is set to face a panel of U.S. advisers on Tuesday who are likely to have tough questions on the pill's heart risks and other safety concerns.
Shares of Orexigen have fallen 36 percent this year as investors worry whether the biotech can succeed where rivals have failed, aiming to tap into a potentially major market in the United States, where rates of obesity continue to soar.
Drugmakers seeking a pill to help people slim down have been thwarted for decades by serious side effects, and few options remain on the U.S. market even though two out of three Americans are overweight or obese. [ID:nN29219928]
The U.S. Food and Drug Administration in October rejected two rival pills from Arena Pharmaceuticals Inc <ARNA.O> and Vivus Inc <VVUS.O>.
Orexigen, which has partnered with Takeda Pharmaceutical Co Ltd <4502.T> to help market its Contrave pill, will make its case before an FDA panel of outside experts on Tuesday.
Contrave combines the alcohol and drug addiction drug naltrexone and the antidepressant bupropion in an attempt to boost metabolism while curbing appetite and cravings.
"It's quite clear that the safety discussion will once again be key, especially with regard to cardiovascular risk," JP Morgan analysts said in a recent note. "We anticipate a tough panel."
FDA is expected to make a final decision by Jan. 31, after considering the advisory panel's recommendation.
Approval is key to California-based Orexigen, which focuses solely on obesity drugs and has no products on the market yet.
According to data from BioMedTracker, Contrave sales could reach ${esc.dollar}1.2 billion by 2018. That figure would make it the top player in a U.S. weight-loss drug market that sees just ${esc.dollar}382 million annually, according to IMS Health.
Although the pill meets FDA effectiveness guidelines, in that at least 35 percent of patients studied were able to loose at least 5 percent of their body weight, agency staff last week pointed to concerns over heart risks, seizures and suicidal behavior. [ID:nN0340431]
MODEST WEIGHT LOSS ENOUGH?
Analysts have said Orexigen's chances to win panel support and FDA approval hinge on its ability to convince the experts that Contrave's risks are manageable.
Orexigen has said even modest weight loss can significantly improve a patient's health by reducing the risk for chronic diseases linked to obesity such as diabetes and heart disease. It has said major heart problems were not common and occurred at a rate comparable to a placebo.
Also at issue is whether the panel will consider the company's 12 months of data as sufficient for a drug which many critics say may be used for far longer by many patients.
Orexigen's only other fat pill candidate, Empatic, combines the anti-seizure drug zonisamide with bupropion and is still in clinical trials.
Diet and exercise are proven to help people shed pounds, but some say such efforts can be so difficult that drugs or other options like surgery are needed. Critics say policy changes targeting foods, public transportation, and other lifestyle changes are needed more than new pills.
In October, the FDA rejected Arena's lorcaserin over concerns about cancer findings in animal studies and shot down Vivus's Qnexa by asking for more data on its heart risks. (Reporting by Susan Heavey; Editing by Tim Dobbyn)
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