The purpose of this study is to prove effect of glucose reduction that CKD-501 and metformin combination treatment group is non inferiority compare to pioglitazone and metformin combination.

The aim of this phase 3 study was to evaluate the efficacy and safety of CKD-501 and metformin combination for 24 weeks in type 2 diabetes mellitus. Furthermore, the extension study for additional 28weeks is designed to confirm long term safety of CKD-501 as an oral hypoglycemic agent.

Inclusion Criteria:

• Between 18 years and 80 years old(male or female)
• Type Ⅱ diabetes mellitus
• The patient who has been taking oral hypoglycemic agent since 2 months with HbA1c 7 to 10% at screening test
• BMI between 21kg/㎡ and 40kg/㎡
• C-peptide level is over 1.0 ng/ml
• Agreement with written informed consent

Exclusion Criteria:

• Type I diabetes or secondary diabetes
• Continuous or non continuous treatment(over 7 days) insulin within 3 month prior to screening
• Treatment with thiazolidinediones within 60 days or patient who have experience such as hypersensitivity reaction, serious adverse event or no effect by treatment with glitazones
• Chronic(continuous over 7 days) oral or non oral corticosteroids treatment within 1 month prior to screening
• Past history: lactic acidosis or metformin contraindication
• Acute or chronic metabolic acidosis including diabetic ketoacidosis
• History of proliferative diabetic retinopathy
• Severe infection, severe injury patients (pre and post operation)
• Oligotrophy,starvation, hyposthenia, pituitary insufficiency or capsular insufficiency
• Drug abuse or history of alcoholism
• History of myocardial infarction, heart failure, cerebral infarction, hematencephalon or unstable angina within 6 months
• Fasting Plasma Glucose level is over 270 mg/dl
• Triglyceride level is 500 mg/dl and over
• Significant abnormal liver dysfunction: AST, ALT level over or equal to 2.5 times, Total bilirubin level over or equal 2 times as high as upper normal limit(UNL)
• Significant abnormal renal dysfunction
• Anemia
• Abnormality of thyroid function(out of significant normal TSH range )
• Hepatitis B or C test is positive
• Pregnant women or nursing mothers
• Has a contraindication to treatment
• Fertile women who not practice contraception with appropriate methods
• Participated in other trial within 4 weeks
• Participating in other trial at present
• In investigator's judgment