UPDATE 2-Arena files for approval for weight loss drug

* Drug expected to compete with Vivus, Orexigen

* Arena shares rise 0.8 pct on Nasdaq
(Updates share price, adds details)

BOSTON, Dec 22 (Reuters) - Arena Pharmaceuticals Inc
(ARNA.O) said on Tuesday it has submitted an application with
regulators to market its experimental weight loss drug
lorcaserin.

The company has said a 4,000-patient trial found that 47.2
percent of subjects taking lorcaserin twice a day lost 5
percent or more of their weight after a year, compared with 25
percent of patients taking a placebo. The average weight loss
in patients taking lorcaserin was 12.7 pounds.

In patients who completed the trial and did not drop out,
63.2 percent lost at least 5 percent of their weight compared
with 34.9 percent of patients on placebo. About 35 percent lost
at least 10 percent of their weight.

The average weight loss for lorcaserin patients after one
year was 17 pounds, compared with 8.7 pounds for the placebo
group.

The company is competing with rivals Vivus Inc (VVUS.O) and
Orexigen Therapeutics Inc (OREX.O) to develop the first new
prescription weight loss drug in a decade.

Orexigen plans next year to file for approval of its drug,
Contrave, which combines the antidepressant Wellbutrin, known
generically as bupropion, with naltrexone, an opioid blocker
used to treat alcoholism.

The biggest hope in the space, however, is Qnexa, an
experimental drug being developed by Vivus. In a late-stage
clinical trial, 1,267 morbidly obese patients who completed the
trial with Qnexa lost an average of 37 pounds, or 14.7 percent
of their body weight, in the course of a year, compared with a
body weight loss of 2.5 percent for patients taking a placebo.

Qnexa combines relatively low doses of the generic
stimulant phentermine with the epilepsy drug topiramate, sold
under the brand name Topamax.

Arena shares were up 0.8 percent at $3.77 on Tuesday
afternoon on the Nasdaq.
(Reporting by Toni Clarke; editing by John Wallace and Matthew
Lewis)