Xconomy -- Arena Pharmaceuticals (NASDAQ: ARNA) has spent a dozen years working on developing a new drug with potential to help millions of people lose weight. Now U.S. regulators have had a chance to comb through detailed clinical trial results, and found it passed one of the two common standards for effectiveness of an obesity drug by a “slim margin.” Plus, regulators raised questions from studies in which rats on extreme high doses of the drug had higher rates of cancer. Shares of the company fell 37 percent to $4.31 at 10:15 am Eastern.
