The purpose of this study is to evaluate the safety and efficacy of S-707106 co-administered with metformin in subjects with type 2 diabetes mellitus.

Based on the unmet clinical need for more safe and effective type 2 diabetes mellitus therapies, together with the nonclinical efficacy and safety profile of S-707106, Shionogi USA, Inc. is initiating studies to further assess the efficacy, clinical pharmacology and safety profile of S-707106 in preparation for full clinical development as a novel treatment for type 2 diabetes mellitus. It is anticipated that S-707106 will provide clinicians and patients with a new therapeutic option to treat type 2 diabetes mellitus with potential advantages over existing therapy.

Main Inclusion Criteria:

• Subjects with type 2 diabetes mellitus receiving a stable dose of metformin for the past 3 months (with no other medication for glycemic control) and who are clinically stable as determined by medical history
• Body mass index (BMI) ≥25.0 and <45.0 (kg/m2) using http://www.bmicalculator.org/ as the BMI calculator
• No clinically significant abnormal laboratory tests as determined by the investigator except Hemoglobin A1c level ≥7.5% and ≤11.0% and C peptide level >1.0 ng/mL

Main Exclusion Criteria:

• Type 1 diabetes mellitus or gestational diabetes mellitus within last 6 months
• Use of any medication for glycemic control other than metformin during the past 3 months or thiazolidinediones within the past year
• Congestive heart failure as defined by New York Heart Association class III or IV
• Fasting glucose >270 mg/dL
• Creatinine clearance is <60 mL/minute
• History of myocardial infarction within the past 3 months, history of clinically significant cardiac arrhythmia, clinically significant hypotension or hypertension, or clinically significant abnormal electrocardiogram as determined by the investigator