WASHINGTON – Investors in Orexigen Therapeutics Inc. Wednesday were not only bubbling over with excitement about an FDA panel's backing of the firm's obesity drug Contrave (naltrexone/bupropion) – with the company's stock rocketing as high as 129 percent – but shares of potential competitors Arena Pharmaceuticals Inc. and Vivus Inc. also were on fire, leaping as high as 20.5 percent and 19.5 percent, respectively.