Arena shares dive ahead of expert panel meeting

Arena Pharmaceuticals' stock was hit hard today as FDA staffers expressed concern about the company's weight loss drug lorcaserin. Preclinical data in rats show the drug was linked to "valvular heart disease, neuro-psychiatric and cognitive-related adverse events, and preclinical tumor development," according to TheStreet. The FDA notes, however, than an increased cancer risk wasn't apparent in the 7,000 subjects who participated in Arena's clinical trials.

Additionally, staffers note that clinical trials of the drug just barely met one of the two common standards for obesity drug effectiveness. Those enrolled in Arena's Bloom trial lost 5.8 percent of their body weight, compared with 2.2 percent in the placebo group. The FDA generally wants weight loss drugs to be 5 percentage points better than placebo, notes Xconomy, so lorcaserin misses that goal. But the agency also wants twice as many patients on experimental drugs to lose 5 percent to 10 percent of their body weight than the placebo group, and that's where Arena's drug succeeded.

An expert panel will review the drug Thursday. Arena has spent 12 years developing lorcaserin, and is in a race with two other drug developers to reach the market with the first new obesity drug in years. An FDA panel vote against Vivus' obesity drug Qnexa, while Orexigen Therapeutics will present its case for Contrave in December.

- read the FDA's briefing documents
- check out Arena's documents
- see Xconomy's take
- get more from TheStreet