A Double-blinded Trial Comparing the Efficacy and Safety of Insulin Degludec/Liraglutide and Insulin Degludec Both in Combination With Metformin in Japanese Subjects With Type 2 Diabetes Mellitus Inadequately Controlled With Basal or Pre-mix/Combination Insulin Therapy and Oral Anti-diabetic Drugs

Inclusion Criteria

• Male or female Japanese subjects, age at least 20 years at the time of signing informed consent
• T2DM (type 2 diabetes mellitus) subjects (diagnosed clinically) for at least 6 months prior to screening
• HbA1c (glycosylated haemoglobin) 7.5-11.0 per cent [58 mmol/mol-97 mmol/mol] (both inclusive) by central laboratory analysis
• Subjects on stable daily insulin doses for at least 60 days prior to screening administered once or twice daily, either as basal insulin (e.g. IDeg, insulin glargine, insulin detemir, NPH insulin) or pre-mix/combination insulin (e.g. biphasic insulin aspart, insulin degludec/insulin aspart). Total daily insulin dose in the previous 60 days should be within 20-50 units, both inclusive, and on the day of screening, but fluctuations of plus/minus 20 per cent within the 60 days prior to screening are acceptable. The specified insulin treatment should be administered in combination with a stable daily dose of metformin within current approved Japanese label for at least 60 days prior to screening - additionally, the anti-diabetic treatment can be with or without a stable daily dose of one of the following other OADs (oral anti-diabetic drug): SU (sulfonylureas), glinides, alpha-glucosidase inhibitor, SGLT2i (sodium glucose co-transporter 2 inhibitor) or TZD (thiazolidinedione) within current approved Japanese label for at least 60 days prior to screening
• Body Mass Index (BMI) equal or above 23 kg/m^2

Exclusion Criteria

• Receipt of any investigational medicinal product (IMP) within 30 days before screening
• Use of any anti-diabetic drug in a period of 60 days before screening (except premix/ combination or basal insulin, metformin, SU, glinides, α-GI, SGLT2i, or TZD) or anticipated change in concomitant medication, which in the investigators opinion could interfere with glucose metabolism (e.g. systemic corticosteroids or bolus insulin)
• Treatment with glucagon-like peptide-1 (GLP-1) receptor agonist during the last 60 days prior to screening and furthermore, the discontinuation of GLP-1 receptor agonist at any point in time must not have been due to safety concerns, tolerability issues or lack of efficacy, as judged by the investigator
• Treatment with dipetidyl peptidase-4 (DPP-4) inhibitors during the last 60 days prior to screening - Impaired liver function, defined as alanine aminotransferase (ALT) or aspartate aminotransferase (AST) equal or above 2.5 times upper limit of normal
• Renal impairment estimated Glomerular Filtration Rate (eGFR) below 60 mL/min/1.73m^2 as per Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI)
• Screening calcitonin equal or above 50 ng/L
• History of pancreatitis (acute or chronic)
• Personal or family history of medullary thyroid carcinoma (MTC) or multiple endocrine neoplasia type 2 (MEN 2)
• Subjects presently classified as being in New York Heart Association (NYHA) Class IV