A Trial Comparing the Safety and Efficacy of Semaglutide Once Weekly Versus Sitagliptin Once Daily in Japanese Subjects With Type 2 Diabetes

Inclusion Criteria: * Male or female, age 20 years or older at the time of signing informed consent * Glycated hemoglobin (HbA1c) between 6.5% and 9.5% (48-80 mmol/mol) (both inclusive) for subjects treated with oral antidiabetic drug (OAD) monotherapy and between 7.0% and 10.5% (53-91 mmol/mol) (both inclusive) for subjects treated with diet and exercise therapy at screening * Japanese subjects diagnosed with type 2 diabetes who are: a) on stable OAD monotherapy at a half-maximum dose or below according to the approved Japanese labelling in addition to diet and exercise therapy for at least 30 days prior to screening (week -8) (For metformin only: the maximum dose of 750 mg/day is allowed except for METGLUCO®. For METGLUCO®, the allowable half-max dose of 1125 mg/day must be applied.). 'Stable' is defined as unchanged medication and unchanged dose, or b) on stable diet and exercise therapy for at least 30 days prior to screening (week -2) Exclusion Criteria: * Female who is pregnant, breast-feeding or intends to become pregnant or is of child-bearing potential and not using an adequate contraceptive method (e.g. abstinence, diaphragm, condom \[by the partner\], intrauterine device, sponge, spermicide or oral contraceptives) throughout the trial including the 5-week follow-up period * Treatment with once-weekly glucagon-like peptide-1 (GLP-1) receptor agonists within 90 days prior to screening * Treatment with any glucose lowering agent(s) (except for pre-trial OAD for subject treated with OAD monotherapy) in a period of 60 days prior to screening. An exception is short-term treatment (7 days or less in total) with insulin in connection with inter-current illness * Any disorder which, in the opinion of the investigator, might jeopardise subject's safety or compliance with the protocol * History of chronic or idiopathic acute pancreatitis * Screening calcitonin value of 50 ng/L (pg/mL) or greater * Personal or family history of medullary thyroid carcinoma (MTC) or multiple endocrine neoplasia syndrome type 2 (MEN2) * Impaired renal function defined as estimated glomerular filtration rate (eGFR) less than 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