Obesity patients treated with a weight-loss pill from Orexigen Therapeutics ( OREX) lost an average of 20.3 pounds, or 9.3% of their body weight, over one year, according to results from a phase III study released Thursday.

Orexigen said the study of its weight-loss drug Contrave met all its pre-specified efficacy and safety goals. However, patients in the trial who took a sugar pill for one year lost an average of 11 pounds, or 5.1% of their body weight.

That puts the placebo-adjusted percentage of body weight lost by Contrave patients at 4.2% -- below the 5% weight-loss standard for approval mandated by the U.S. Food and Drug Administration for all experimental obesity drugs.

Orexigen Chief Financial Officer Graham Cooper says the company is pleased with the results of the study because Contrave patients lost significantly more weight than placebo patients. The study was made more challenging because all patients, whether treated with Contrave or placebo, received extensive counseling and were enrolled in strict exercise and diet programs.

"It's no surprise to us that placebo patients lost as much weight as they did given the extensive behavioral modifications in the study," said Cooper, in an interview. "We expected to see a smaller placebo-adjusted weight loss."

In a previous phase II study of Contrave, patients lost between 6% and 7% of their body weight, adjusted for placebo, lower than the 4.2% reported in the phase III study Thursday.

In the phase III study, 41.5% of the Contrave patients lost 10% or more of their body weight over one year compared to just over 20% of placebo patients. This doubling of the percentage of patients who lost significant weight is another way to win over FDA reviewers, added Cooper.

Contrave consists of two currently approved drugs combined together to suppress appetite and fight food cravings. One of the drugs in Contrave is naltrexone, currently used to fight opioid and alcohol addiction; the other drug is the antidepressant bupropion.

A change to the formulation of naltrexone included in the Contrave pills used in the phase III study drastically reduced the percentage of patients who stopped taking Contrave due to nausea to 4.6%, lower than the 11% discontinuation rate reported in previous studies.

The overall discontinuation rate due to adverse events was just under 26% for Contrave patients compared to 13% for placebo patients. The most commonly reported adverse events were nausea, hives and anxiety.

Importantly, Cooper says there were no reported adverse events related to increases in depression, suicidality or worsening blood pressure in Contrave patients. No patients in the study suffered heart attack or strokes.

Contrave patients did report improvements over placebo in some cardiovascular health measures, including higher levels of HDL, or good cholesterol, lower triglycerides and smaller waist circumference.

Results from three other, ongoing phase III studies of Contrave are expected in the middle of the year.

Orexigen is one of three relatively small drugmakers - Vivus ( VVUS - Get Report) and Arena Pharmaceuticals ( ARNA - Get Report)are the other two -- in a race to develop the next generation of obesity drugs.

Orexigen shares, which closed down 3 cents at $6.05, were plummeting more than 25% in after-hours trading.

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