Exenatide belongs to a class of antidiabetic agents called incretin mimetics. In 2005, exenatide was first applied clinical therapy of type 2 diabetes mellitus patients in US, and it has now began to be used in Japanese type 2 diabetes mellitus patients since 2010. Large phase 3 clinical trials in Japan revealed that HbA1c, fasting glucose and postprandial glucose levels were improved with exenatide treatment, which were maintained over 52 weeks. Body weight reduction could be achieved with 10 microg treatment. HDL-C was significantly reduced. Exenatide was generally well tolerated, however incidence of hypoglycemia and gastro-intestinal side effect were elevated. Antibodies to exenatide were observed among approximately half of patients, however had no clinical relevant effects on the efficacy or safety.