Arena Defends Obesity Drug as Stock Plunges

Updated from 12:19 p.m. EDT

Arena Pharmaceuticals(ARNA Quote) executives spent the better part of an hour-long conference call Monday morning defending the clinical benefit and safety of the company's weight-loss drug lorcaserin as shares of the company sank in early trading.

The San Diego-based drug company reported that patients treated with lorcaserin lost an average of 12.7 pounds, or 5.8% of their body weight, over one year. However, patients in the study treated with a placebo lost an average of 4.7 pounds, or 2.2% of their body weight, over the same one-year period.

That puts the placebo-adjusted weight loss in the study at 3.6%, below the 5% weight-loss standard for approval mandated by the Food and Drug Administration for all experimental obesity drugs. ...