Efficacy and Safety of Semaglutide Once Weekly Versus Insulin Glargine Once Daily as add-on to Metformin With or Without Sulphonylurea in Insulin-naïve Subjects With Type 2 Diabetes

Inclusion Criteria: * Male or female, 18 years or older at the time of signing informed consent * Insulin-naïve subjects diagnosed with type 2 diabetes and on stable diabetes treatment with metformin or metformin and SU (metformin 1500 mg or higher or maximum tolerated dose and SU half of maximum allowed dose according to national label or higher) for at least 90 days before screening. Stable is defined as unchanged medication and unchanged dose * HbA1c 7.0 - 10.0% (53 - 86 mmol/mol) both inclusive Exclusion Criteria: * Female who is pregnant, breast-feeding or intends to become pregnant or of childbearing potential not using adequate contraceptive method (adequate contraceptive measures as required by local regulation or practice) throughout the trial including the 5 week follow-up period * Any disorder which, in the opinion of the Investigator might jeopardise subject's safety or compliance with the protocol * Treatment with any glucose lowering agent(s) other than stated in the inclusion criteria in a period of 90 days before screening. An exception is short-term treatment (7 days or less in total) with insulin in connection with intercurrent illness * History of chronic or idiopathic acute pancreatitis * Screening calcitonin value greater than or equal to 50 ng/L * Personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia syndrome 2 * Severe renal impairment defined as estimated glomerular filtration rate (eGFR) less than 30 mL/min/1.73 m\^2 per modification of diet in renal disease (MDRD) formula (4 variable version) * Acute coronary or cerebrovascular event within 90 days before randomisation * Heart failure, New York Heart Association Class IV * Known proliferative retinopathy or maculopathy requiring acute treatment according to the opinion of the investigator * Diagnosis of malignant neoplasm in the previous 5 years (except basal cell skin cancer or squamous cell skin cancer) * Mental inability, unwillingness or language barrier precluding adequate understanding of or compliance with study procedures