Durable Effect of Imeglimin on the Glycemic Control in Patients With Type 2 Diabetes Mellitus

Inclusion Criteria: 1. Patients diagnosed with type 2 diabetes mellitus who are 20 years of age or older at the time of obtaining consent. 2. Patients being treated with diet and exercise therapy only at the time of eligibility test However, if the patient is taking one oral hypoglycemic drug at the time of obtaining consent, the patient must be able to wash out the oral hypoglycemic drug for at least 12 weeks before the start of study treatment. 3. Patients whose HbA1c level is between 7.0% and 9.0% as measured at the time of the eligibility test. 4. Patients who have given written consent to participate in this study. Exclusion Criteria: When consent is obtained 1. Patients with type 1 diabetes mellitus 2. Patients who have been given more than 2 oral hypoglycemic drugs within 12 weeks 3. Patients who have received glucagon like peptide-1 receptor agonist (short-term use of insulin for trauma or educational admission) within 1 year or less 4. Patients with proliferative retinopathy (except for patients with stable treated proliferative retinopathy) 5. Patients with severe diabetic neuropathy (patients with severe symptoms and significant support for daily life) 6. Patients with a contraindication to Imeglimin, Metformin, or Vildagliptin 7. Patients with severe obesity (BMI 35 kg/m\^2 or more) 8. Patients with NYHA (New York Heart Association) cardiac function classification of Grade III or IV within 1 year of evaluation 9. Excessive regular drinkers 10. Patients with a previous history of lactic acidosis 11. Patients with severe cachexia, diabetic coma or precoma 12. Patients with severe infections, surgical patients and those with serious injuries 13. Patients who are pregnant, who are planning to be pregnant, or who are breastfeeding 14. Patients who are undergoing treatment for malignancy or those with a history of treatment for malignancy within 5 years 15. Patients who are participating in a clinical study with other interventions 16. Patients to whom a responsible physician/investigator judged inappropriate for participating in the study In case of eligibility testing 17. Patients with an estimated glomerular filtration rate(eGFR) of 45 mL/min/1.73m\^2 or less including those undergoing dialysis 18. Patients with severe hepatic disorders (Child-Pugh classification Grade C)