DexCom, Inc. (NasdaqGS:DXCM) said it isn't active merger talks, sending the stock up more than 8% after news reports last week that the company was in talks to buy Insulet Corporation (NasdaqGS:PODD). "We do not intend to comment further on this topic and we assume no obligation to make any further announcement or disclosure should circumstances change," Dexcom said.