Screening will be made to select eligible participants before intervention. The trial will include 2-week run-in period of stable doses of glargine plus lispro insulin and 24-week treatment period. After the run-in period, patients were randomly assigned to one of two groups for antihyperglycaemic therapies for a total of 24-weeks: glargine plus exenatide and continued glargine plus lispro insulin. The treatment of exenatide will be initiated by 5ug bid, and uptitrated to 10 ug bid after 4 weeks and then maintained at 10ug bid until the completion of the study. Lispro insulin will be initially treated according to the insulin dosage of previous antihyperglycaemic therapies, and further titrated up at 4-week intervals until to reach the target fasting blood glucose (FPG).