Arena falls on lorcaserin briefing documents

Arena Pharmaceuticals Inc. (NASDAQ:ARNA) fell $2.72 (40%) to $4.13 on Tuesday after FDA questioned the efficacy and safety of lorcaserin in briefing documents posted ahead of Thursday's Metabolic and Endocrine Drug Products Advisory Committee meeting to discuss the obesity candidate.

According to draft guidance for obesity candidates published by FDA in 2007, the placebo-adjusted weight loss must be 5% for those in the treatment arm of a study, or the proportion of patients who lose at least 5% of baseline body weight in the treatment group should be double the proportion in the placebo group. In its briefing materials, the agency said lorcaserin missed the first benchmark, and met the latter criterion by "a slim margin." In Arena's Phase III program, once- and twice-daily doses of the serotonin (5-HT2C) receptor agonist produced placebo-adjusted mean weight loss of about 3%. Also, 40% and 47% of subjects in the lorcaserin once- and twice-daily arms, respectively, lost at least 5% of baseline body weight compared to 23% of those in the placebo group. ...