['type 2 diabetes mellitus']
['ds-8500a 25 mg', 'ds-8500a 75 mg', 'placebo']

        Inclusion Criteria:

          -  Japanese patients with type 2 diabetes

          -  Patients aged ≥ 20 years at the time of informed consent

          -  Patients who have been treated with sitagliptin 50 mg monotherapy for the treatment of
             type 2 diabetes mellitus

          -  Patients who have HbA1c ≥ 7.0% and < 9.0%

        Exclusion Criteria:

          -  Patients with type 1 diabetes mellitus or with a history of diabetic coma, precoma, or
             ketoacidosis

          -  Patients receiving or requiring treatment with insulin

          -  Patients with a body mass index (BMI) of < 18.5 kg/m2 or ≥ 35.0 kg/m2

          -  Patients with clinically evident renal impairment (estimated glomerular filtration
             rate [eGFR] of < 45 mL/min per 1.73 m2) or clinically significant renal disease

          -  Patients with fasting plasma glucose ≥ 240 mg/dL
      