NEW YORK (AP) — - Arena Pharmaceuticals Inc. says its obesity drug candidate lorcaserin succeeded in a clinical study, but the drug did not appear to be as effective as other treatments competitors have in development. Arena says lorcaserin met its goals in the study, as patients in the study who took the drug lost more weight than those who took a placebo. The drug also met minimum Food and Drug Administration standards of effectiveness required for approval. The company plans to file for FDA approval in December. However lorcaserin did not match the effectiveness of Orexigen Therapeutics Inc.'s drug Contrave and Vivus Inc.'s Qnexa. Those companies reported late-stage study results earlier this year. Arena shares fell as much as 15 percent in premarket trading. Arena said patients who took 10 milligrams of lorcaserin twice per day lost an average of 17 pounds, or 7.9 percent of their body weight, and 63.2 percent of the study patients lost at least 5 percent of their weight. Of those patients treated with a single, 10-mg dose each day, 53.1 percent lost at least 5 percent of their body weight and 26.3 percent lost at least 10 percent, with an average weight loss of 14.3 pounds, or 6.5 percent of their weight. Both were significantly better than the results for patients who took a placebo, and were in line with FDA goals required for approval. But in studies released earlier this year, Qnexa led to weight loss of 13 percent to 15 percent, and Contrave patients lost more than 8 percent of their weight. The trial was called Blossom, and involved 4,008 patients with a baseline weight of 220 pounds. Arena said a total of 7,190 patients were involved in two late-stage studies of the drug. According to FDA guidelines, obesity drug candidates must lead to weight loss of at least five percent for at least one-third of clinical trial patients to gain approval. At least twice as many patients on the drug must reach the five percent goal compared with patients taking a placebo. In the placebo group, 34.9 percent of patients met the 5 percent goal. Arena said lorcaserin also improved blood pressure and fat levels. The company said 35.1 percent of patients in the twice-a-day lorcaserin group lost at least 10 percent of their weight, compared with 26.3 percent for patients who took the drug once per day, and 16.1 percent for placebo patients. The company plans to report data from the most-recent study, called Blossom, and a previous study called Bloom at the 27th annual scientific meeting of The Obesity Society, scheduled for Oct. 24-28 in Washington, D.C. Shares of Arena recently fell 56 cents, to $4.35 in premarket trading on Friday. It closed at $4.91 on Thursday.