Trails result of the experimental obesity drug by Arena Pharmaceuticals (ARNA. O) showed that the drug only helped in reducing 10 pounds. The trails results led to fall of shares of company.

Arena Pharmaceuticals said its two-year study on lorcaserin met all primary goals and showed the drug was well-tolerated by patients. The drug showed statistical significance in weight loss compared with patients on a placebo. After 12 months, patients on lorcaserin lost an average of 5.8% of body weight, or 12.7 pounds, compared with 2.2%, or 4.7 pounds, for the placebo group.

Study of 3,182 people showed that new drug showed no signs of heart valve damage after two-year treatment period. The problem that forced Wyeth (WYE. N) to recall its blockbuster "fen-phen" diet drugs in 1997.

However company new drug fell short of the 5% difference needed by FDA.

Arena said the 3.6 percentage-point figure wasn't the most important, saying the percentage of patients who lost 5% or more of their body weight was the first goal, and that did beat the FDA's benchmark. The study showed that 48% of lorcaserin patients lost 5% or more of their body weight, compared with 20% of the placebo group.