The purpose of this study is to compare the efficacy and safety of ASP1941 50mg once daily in combination with metformin and sitagliptin against placebo in combination with metformin and sitagliptin over a 24 week treatment period in subjects with type 2 diabetes mellitus with inadequate glycemic control on metformin and sitagliptin.

Inclusion Criteria:

• Subject has been diagnosed with type 2 diabetes mellitus.
• Subject has an HbA1c value between 7.0% and 10.5 % at visit 1.
• Subject shows FPG (Fasting Plasma Glucose) value is less than 270mg/dL.
• Subject shows a BMI of 20.0 to 45.0 kg/m2.
• Subject is on stable diet and exercise program at least 8 weeks prior to study participation.
• Postmenopausal female or surgically sterile female or agree not to become pregnant.

Exclusion Criteria:

• Subject has type 1 diabetes mellitus.

• Subject has proliferative diabetic retinopathy.

• Subject has a history of clinically significant renal disease(s) such as renovascular occlusive disease, nephrectomy, or renal transplant.

• Subject has significant dysuria caused by a neurogenic bladder or a benign prostatic hypertrophy etc.

• Subject has a symptomatic urinary tract infection or genital infection.

• Subject has chronic disease(s) that require the continuous use of systemic corticosteroids or immunosuppressants.

• Subject has cardiovascular disease or cerebrovascular disease that may affect the administration of ASP1941 or its safety assessment in the opinion of the investigator or sub-investigator.

• Subject has uncontrollable psychiatric disorder(s) with medication.

• Male subject is not willing to use appropriate contraception during the study.

• Subject has severe infection, serious trauma, or perioperative subject.

• Subject has a malignant tumor or has a history of malignant tumor.

• Subject has severe gastrointestinal disease, or history of operation for serious gastrointestinal disease.

• Subject has diabetic ketoacidosis.

• Subject has lactic acidosis or has history of lactic acidosis.

• Subject has hepatitis or is a carrier of hepatitis B surface antigen (HBsAg), hepatitis C virus (HCV) antibody, or is positive for HIV-1 and/or HIV-2.

• Subject has a history of thyroid dysfunction and acute pancreatitis.

• Subject is on weight-loss program or weight-loss medication (e.g. orlistat, phentermine/topiramate, lorcaserin) within 12 weeks of study participation.

• Subject has a history of serious cardiac diseases (NYHA Class III to IV), congestive heart failure, arrhythmia in need of medical treatment.

• Subject has a history of cerebrovascular attack, unstable angina, myocardial infarction, angioplasty, within 52 weeks (364 days) of study participation.

• Subject has uncontrollable severe hypertension, i.e., systolic blood pressure of higher than 180 mmHg or diastolic blood pressure of higher than 110mmHg measured in a sitting position after a 5-minute rest.

• Subject has following AST or ALT value:

  • AST: Male > 100 U/L, Female > 80 U/L
  • ALT: Male > 102.5 U/L, Female > 82.5 U/L

• Subject has following serum creatinine value:

  • Creatinine: Male > 1.3 mg/dL, Female > 1.2 mg/dL

• Subject has estimated GFR values, of < 60 mL/min/1.73m2.

Access to anonymized individual participant level data collected during the study, in addition to study-related supporting documentation, is planned for studies conducted with approved product indications and formulations, as well as products terminated during development. Studies conducted with product indications or formulations that remain active in development are assessed after study completion to determine if Individual Participant Data can be shared. Further details on Astellas' data sharing policy can be found at https://www.clinicaltrials.astellas.com/transparency/.

Access to participant level data is offered to researchers after publication of the primary manuscript (if applicable) and is available as long as Astellas has legal authority to provide the data.

Researchers must submit a proposal to conduct a scientifically relevant analysis of the study data. The research proposal is reviewed by an Independent Research Panel. If the proposal is approved, access to the study data is provided in a secure data sharing environment after receipt of a signed Data Sharing Agreement.