Efficacy and Safety of SYR-472 in Subjects With Type 2 Diabetes Mellitus

Inclusion Criteria: * Had a historical diagnosis of type 2 diabetes mellitus. * Had undergone less than 7 days of any antidiabetic therapy except lifestyle modification (diet/exercise) within 8 weeks prior to Screening; or has received metformin monotherapy for at least 8 weeks prior to Screening and maintained a stable daily dose of metformin for at least 12 weeks prior to randomization. * If receiving metformin monotherapy at randomization must have been at least 75% compliant with his or her regimen during the Run in/Stabilization Period as determined by subject diary and investigator assessment. * Had received no treatment with antidiabetic agents other than metformin within the 8 weeks prior to Screening. * The subject has an glycosylated hemoglobin concentration between 7.0% and 10.0%, inclusive, at Screening and at the Week -1 Visit. * Had a body mass index between 23 and 45 kg/m2. * A C-peptide concentration is greater than or equal to 0.8 ng/mL (greater than or equal to 0.26 nmol/L). * A fasting plasma glucose concentration is less than 275 mg/dL (less than 15.27 mmol/L) at Screening and at the Week -1 Visit. * If the subject regularly uses other non-excluded medications, he or she must be on a stable dose for at least the 4 weeks prior to Screening. * The subject has a systolic blood pressure reading of less than 160 mm Hg and a diastolic pressure reading of less than 100 mm Hg. * The subject has a hemoglobin value greater than or equal to 12 g/dL (greater than or equal to 120 g/L) for men and greater than or equal to 10 g/dL (greater than or equal to 100 g/L) for women. * Had an alanine aminotransferase level is less than or equal to 3 times the upper limit of normal. * A male subject has a serum creatinine value of less than 1.5 mg/dL (less than 133 μmol/L); a female subject has a serum creatinine value of less than 1.4 mg/dL (less than 124 μmol/L). * Had a urine albumin/creatinine ratio of less than 1000 μg/mg at Screening. * Had a thyroid-stimulating hormone level less than or equal to the upper limit of the normal range and the subject is clinically euthyroid. * A female subject of childbearing potential who is sexually active must agree to use adequate contraception, and must be neither pregnant nor lactating from Screening and throughout the duration of the study. * Was able and willing to monitor his or her own blood glucose concentrations with a home glucose monitor. * Had no major illness or debility that in the investigator's opinion prohibits the subject from completing the study. Exclusion Criteria: * Was being concurrently treated with antidiabetic therapy other than metformin and lifestyle intervention. * Had a history of cancer, other than squamous cell or basal cell carcinoma of the skin that has not been in full remission for at least 5 years prior to Screening. * Had a history of laser treatment for proliferative diabetic retinopathy within the 6 months prior to Screening. * Had a history of treated diabetic gastric paresis. * Had a New York Heart Association class III or IV heart failure regardless of therapy. * Had a history of coronary angioplasty, coronary stent placement or coronary bypass surgery, myocardial infarction, or stroke within the 6 months prior to Screening. * Had a history of hemoglobinopathy that may affect determination of glycosylated hemoglobin. * Had a history of infection with human immunodeficiency virus. * Had a history of a psychiatric disorder that in the investigator's opinion will affect the subject's ability to participate in the study. * Had a history of alcohol abuse (defined as regular or daily consumption of more than 4 alcoholic drinks per day) or substance abuse (defined as illicit drug use) within the 2 years prior to Screening. * Was required to take or intends to continue taking any disallowed medication, any prescription medication, herbal treatment or over-the counter medication that may interfere with evaluation of the study medication, including: * Ingested or received systemically injected glucocorticoids within the 3 months prior to randomization. * Used prescription or over-the-counter weight-loss drugs within the 3 months prior to randomization. * Received any investigational drug within the 30 days prior to Screening or has received an investigational antidiabetic drug within the 3 months prior to Screening. * Had received previous treatment in an investigational study of SYR-472. * Had a known hypersensitivity to any compound related to SYR-472 or Sitagliptin.