Mountain View, CA-based Vivus (Nasdaq: VVUS) suffered a setback today at an important meeting for the future of obesity drug development, with implications for San Diego's Arena Pharmaceuticals (Nasdaq: ARNA) and Orexigen Therapeutics (Nasdaq: OREX). A panel of experts who advise the FDA said today in a 9-7 vote that Vivus' experimental weight loss [drug] shouldn't be cleared for sale in the U.S.

The FDA panel essentially said that the negative effects on concentration and memory outweigh the weight loss benefit offered by the Vivus drug, according to this Associated Press story.

The FDA has the final say on whether Vivus' combination treatment of phentermine and topiramate (Qnexa), should be approved for sale, although the agency usually follows the advice of its expert panels. The FDA's deadline to make that decision is Oct. 28. Vivus shares were halted today during the FDA proceedings, but they are sure to fall tomorrow, as investors had been optimistically bidding up shares in anticipation of an FDA green light. The negative sentiment from the FDA panel sent a ripple effect through the industry. Shares of Vivus' main competitors, San Diego-based Arena and Orexigen, both fell about 10 percent in extended trading after the FDA panel vote.

The stakes are huge for obesity drug development, as an estimated two-thirds of Americans are considered overweight or obese, with little in the way of pharmaceutical alternatives to diet and exercise. I laid out what's at stake in a preview story yesterday. For more of the real-time coverage from the event earlier today, check out posts from Minyanville's Lisa LaMotta and TheStreet.com's Adam Feuerstein.

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Luke Timmerman is the National Biotech Editor of Xconomy, and the Editor of Xconomy Seattle. You can email him at [email protected], or follow him at twitter.com/ldtimmerman.