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(Fierce) - On a rocky road toward hoped-for approvals, Sanofi's ($SNY) mipomersen has hit a serious rut with European regulators. A European Medicines Agency panel handed down a negative opinion late this week on the antisense drug from Isis Pharmaceuticals ($ISIS) for treating a genetic disease that causes blood cholesterol to jump, citing safety concerns such as signs of liver toxicity and cardiovascular risks in patients in clinical trials