Quadruple Oral Combination Therapy for Type 2 Diabetes Mellitus : Glycemic Control by Thiazolidinedione (TZD) or Sodium Glucose Co-transporter 2 (SGLT-2) Inhibitor as an add-on Therapy in Type 2 Diabetes Mellitus After Failure of an Oral Triple Antidiabetic Regimen

Inclusion Criteria: * 1\. 19 ≤ age ≤ 80, male or female * 2\. Type 2 diabetes patients who have taken triple combination therapy of OADs as followed : Metformin (≥1000 mg/day), Sulfonylurea (Glimepiride ≥ 4 mg/day or Gliclazide ≥ 60 mg/day), DPP-4 inhibitor (Full dose) for over 12 weeks * 3\. At screening, 7% \< HbA1c ≤ 10% * 4\. Patients who refused insulin therapy. * 5\. Subjects who understood the contents of the clinical trial and are cooperative in the trial progress, and are considered to be able to participate until the end of the trial. * 6\. Patients who have voluntarily agreed in writing to participate in the clinical trial after hearing the explanation of the trial. Exclusion Criteria: * 1\. Type 1 diabetes, gestational diabetes, and other types of diabetes than type 2 diabetes mellitus. * 2\. Patients who have the history of allergy of hypersensitivity for the medication of the clinical trial. * 3\. Patients who have the history of taking TZDs or SGLT-2 inhibitors within a year prior to screening visit, or have the history of discontinuation of them due to severe side effects. * 4\. Patients who have the history of acute or chronic metabolic acidosis including diabetic ketoacidosis (with or without coma), or any kinds of ketosis within 12 weeks prior to screening visit. * 5\. Patients who have genetic metabolic diseases, such as galactose intolerance, Lapp lactase deficiency, or glucose-galactose malabsorption * 6\. Patients who have the history of taking steroids for more than 2 weeks, within 8 weeks prior to screening visit. * 7\. Patients who have the history of malignancy within 5 years prior to screening visit (In case of bladder cancer, subjects will be excluded regardless of the time of diagnosis) * 8\. Patients who have the history of coronary artery bypass surgery or percutaneous coronary intervention, or suffered from heart failure (NYHA class III, IV) * 9\. Patients who have the history of uncontrolled arrhythmia, unstable angina, myocardial infarction, stroke, transient ischemic attacks, and cerebral vascular disease within 24 weeks prior to the screening date. * 10\. Patients of chronic renal failure, chronic kidney disease stage 3\~5 (estimated glomerular filtration rate calculated vial CKD-EPI \<60 mL/min/1.73m2) or on dialysis therapy. * 11\. Elevated liver enzymes (AST, ALT, ALP ≥ 2.5\*upper limit of normal (ULN) or Total bilirubin ≥ 2.5\*ULN) or Child-Pugh class B or C (for the patients of liver cirrhosis) * 12\. Subjects who are pregnant or lactating * 13\. Perioperative patients, patients with severe infections or severe trauma * 14\. Patients with unexamined gross hematuria * 15\. Any other subjects who is determined to be ineligible for the clinical trials by researchers.