Consumer group asks FDA to reject Arena diet drug Tue Jun 26, 2012 3:42pm EDT (Reuters) - Watchdog group Public Citizen on Tuesday urged U.S. regulators not to approve Arena Pharmaceuticals Inc's experimental diet pill lorcaserin, citing concerns it could increase patients' risk of heart valve damage. The U.S. Food and Drug Administration is expected to rule on whether to approve the drug by Wednesday. Public Citizen, a nonprofit consumer advocacy group, said physicians at last month's FDA advisory panel meeting on lorcaserin raised serious concerns about evidence of increased valve disease risks in patients who used the drug in clinical trials. The panel of independent experts recommended approval of the pill despite the concerns. If approved, lorcaserin would become the first new diet drug on the U.S. market in more than a decade. Arena's stock plunged 15 percent on Friday in what some traders attributed to profit-taking ahead of the FDA's decision. At one point during the day it had shed a third of its value. The stock has appreciated more than 400 percent this year in anticipation of a favorable ruling. Arena shares were up 0.4 percent at $9.23 on Tuesday afternoon on the Nasdaq. Reporting by Susan Kelly in Chicago; editing by Matthew Lewis