UPDATE 1-Orexigen drug shows 9.3 pct weight loss, shrs fall

(Adds analyst's comment, share price)

By Deena Beasley

LOS ANGELES, Jan 8 (Reuters) - Orexigen Therapeutics Inc (OREX.O) said on Thursday a first late-stage trial found that obese patients treated with experimental drug Contrave lost an average 9.3 percent of their weight, but the results fell short of the bar set by regulators and its shares slid 34 percent.

Orexigen said patients in the trial who were given a placebo lost an average 5.1 percent of their weight -- a differential of 4.2 percent between the two groups. Both groups also followed a diet and exercise regimen.

The U.S. Food and Drug Administration has said obesity drugs need to demonstrate weight loss at least 5 percentage points above that seen with a dummy pill.

"They didn't show that," said Canaccord analyst Adam Cutler, noting that some investors were looking for the drug to show double-digit weight loss.

Cutler said Orexigen has a better chance of meeting expectations in ongoing trials that do not include diet and exercise. Diet and exercise increase the amount of weight lost by all the patients, including those taking the placebo, which skews the effects of the drug itself.

The company said that 26 percent of Contrave patients dropped out of the 793-patient trial due to side effects, compared with 13 percent of the placebo group. Side effects included nausea, hives, anxiety, headache, constipation and dizziness.

Contrave is a pill that combines the antidepressant Wellbutrin, known generically as bupropion, with a sustained- release version of naltrexone, an opioid antagonist used to treat alcoholism and other addictions.

Orexigen said the 56-week study met its primary and secondary goals of a significant reduction in body weight, improvements in markers of cardiovascular risk and reductions in food cravings.

"The safety profile looks quite good. That's almost as important, if not more important, than efficacy," Cutler said.

Orexigen Chief Financial Officer Graham Cooper said the company still expects to file for U.S. regulatory approval of the drug toward the end of this year.

"Side effects and tolerability are going to be critical for the FDA (U.S. Food and Drug Administration). We had a very clean profile," Cooper said.

The company expects to report results this summer from three other late-stage trials of Contrave that do not include diet and exercise.

Orexigen's shares, which closed at $6.05 on Nasdaq, were trading at $3.99 after hours. (Editing by Andre Grenon and Ted Kerr)