Orexigen Tanks After-Hours on Obesity Data

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 Quote) and Arena Pharmaceuticals (ARNA Quote)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.