Efficacy and Safety of Semaglutide Once-weekly Versus Sitagliptin Once-daily as add-on to Metformin in Subjects With Type 2 Diabetes (SUSTAIN - CHINA MRCT)

Inclusion Criteria: - Informed consent obtained before any trial-related activities. Trial-related activities are any procedures that are carried out as part of the trial, including activities to determine suitability for the trial - Male or female, age equal to or above 18 years at the time of signing informed consent - Subjects diagnosed with type 2 diabetes and on stable treatment in a period of 60 days prior to screening with metformin equal to or above 1500 mg (or maximum tolerated dose equal to or above 1000 mg). Stable is defined as unchanged medication and unchanged daily dose - HbA1c 7.0 - 10.5 % (53-91 mmol/mol) (both inclusive) Exclusion Criteria: - Female who is pregnant, breast-feeding or intends to become pregnant or is of childbearing potential not using an adequate contraceptive method throughout the trial including the 5 week follow-up period (adequate contraceptive measure as required by local regulation or practice) - Any disorder which, in the opinion of the investigator, might jeopardise subject's safety or compliance with the protocol - Treatment with glucose lowering agent(s) other than stated in the inclusion criteria in a period of 60 days before screening. An exception is short-term treatment (equal to or below 7 days in total) with insulin in connection with inter-current illness - History of chronic or idiopathic acute pancreatitis - Screening calcitonin value equal to or above 50 ng/L (pg/mL) - Personal or family history of medullary thyroid carcinoma (MTC) or multiple endocrine neoplasia syndrome type 2 (MEN 2) - Impaired renal function defined as estimated glomerular filtration rate (eGFR) below 60 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 (NYHA) class IV