Study of Ipragliflozin in Patients With Type 2 Diabetes Mellitus Receiving Insulin Therapy

Inclusion Criteria: * The subject has been receiving insulin therapy for the treatment of diabetes mellitus. * The subject has type 2 diabetes mellitus and has been receiving insulin monotherapy or insulin therapy in combination with one or two oral hypoglycemic agents. * The subject has not modified diet or exercise therapies or dosage regimen of oral hypoglycemic agents, or has not switched to another pharmacotherapy for 12 weeks before Visit 1. * The subject has an HbA1c value between 6.5% and \<8.0%. * The subject has a body mass index (BMI) of \>23.0 kg/m2. * If the subject is a female, she must satisfy the following criteria. The subject is not of childbearing potential and satisfies any of the following criteria. * The subject is post-menopausal (absence of menses for at least 1 year). * The subject is surgically sterile. The subject is of childbearing potential but satisfies all of the following criteria: * The subject agrees not to get pregnant to 28 days after the last dose of the study drug. * The subject has a negative pregnancy test. The subject agrees to use two of the established contraceptive methods listed below to 28 days after the last dose of the study drug when having heterosexual intercourse. * If the subject is a female, she must agree not to breastfeed to 28 days after the last dose of the study drug. * If the subject is a female, she must agree not to donate their eggs during the period from the assessment to 28 days after the last dose of the study drug. * In case a male subject's spouse or partner is of childbearing potential, the subject must agree to use two of the established contraceptive methods to 28 days after the last dose of the study drug. * If the subject is a male, he must agree not to donate their sperm to 28 days after the last dose of the study drug. Exclusion Criteria: * The subject has type 1 diabetes mellitus. * The subject has any symptom of dysuria, anuria, oliguria or urinary retention. * The subject has proliferative retinopathy. * The subject has diabetic ketoacidosis. * The subject has a history or complication of medically significant renal disease such as renovascular occlusive disease, nephrectomy and/or renal transplant. * The subject has a history of recurrent urinary tract infection. * The subject has symptomatic urinary tract infection or symptomatic genital infection. * The subject has chronic disease(s) that require the continuous use of corticosteroids, immunosuppressants, etc. * The subject has a history of cerebral vascular attack, unstable angina, myocardial infarction, vascular intervention, and serious heart disease within 1 year (52 weeks) before signing of the informed consent. * The subject has a complication or surgical history of serious gastrointestinal disorder. * The subject has severe hepatic dysfunction. * The subject has uncontrolled blood pressure. * The subject has unstable psychiatric disorder. * The subject has severe infection or serious trauma, or perioperative. * The subject has drug addiction or alcohol abuse. * The subject has a history of malignant tumors. * The subject has a history of an allergy to ipragliflozin and/or similar drugs (drugs possessing SGLT2 inhibitory action). * The subject has used SGLT2 inhibitors, GLP-1 receptor agonists, sulfonylureas (SU), glinide agents, or insulin products other than long-acting insulin within 12 weeks before signing of the informed consent.