This study is to evaluate the efficacy and safety after concomitant administration of ASP1941 and pioglitazone in patients with diabetes mellitus.

This study is to evaluate the efficacy (HbA1c change from baseline) and safety of ASP1941 in combination with pioglitazone in subjects with type 2 diabetes mellitus (T2DM) who have inadequate glycemic control with pioglitazone alone. The effects of ASP1941 are compared with those of placebo. Double blind period continues for 24 weeks followed by open period in each patient.

Inclusion Criteria:

• Type 2 diabetic patients receiving pioglitazone mono-therapy for at least 4 weeks
• HbA1c value between 7.0 and 9.5%
• Body Mass Index (BMI) 20.0 - 45.0 kg/m2

Exclusion Criteria:

• Type 1 diabetes mellitus patients
• Serum creatinine > upper limit of normal
• Proteinuria (albumin/creatinine ratio > 300mg/g)
• Dysuria and/or urinary tract infection, genital infection
• Significant renal, hepatic or cardiovascular diseases
• Severe gastrointestinal diseases
• Heart failure patients

Access to anonymized individual participant level data will not be provided for this trial. Further details on Astellas' data sharing policy can be found at https://www.clinicaltrials.astellas.com/transparency/.