Phase I trail will be conducted to determine the MTD and safety of M2ES(administered intravenous infusion on Days 1,8,15,21of a 28-day cycle) in combination with gemcitabine (1000 m/m2). Gemcitabine will be administered as an intravenous infusion on Days 1, 8, and 15 of each 28-day cycle,at the same time determine the safety and efficiency of this combined regime.