Efficacy and Safety of Semaglutide Once-weekly Versus Placebo as add-on to Basal Insulin Alone or Basal Insulin in Combination With Metformin in Subjects With Type 2 Diabetes

This trial is conducted in Asia, Europe and the United States of America (USA). The aim of the trial is to investigate efficacy and safety of semaglutide once weekly versus placebo as add-on to basal insulin alone or basal insulin in combination with metformin in subjects with type 2 diabetes.

Inclusion Criteria: - Male or female, age at least 18 years at the time of signing inform consent. For Japan: Male or female, age at least 20 years at the time of signing informed consent - Subjects diagnosed with T2DM (type 2 diabetes mellitus) and on stable diabetes treatment (plus/minus 20 percent change in total daily dose) with basal insulin (minimum of 0.25 IU/kg/day and/or 20 IU/day of: insulin glargine, insulin detemir, insulin degludec and/or NPH insulin) alone or in combination with metformin (minimum of 1500 mg/day or maximal tolerable dose) for 90 days prior to screening - HbA1c (glycosylated haemoglobin) 7.0 - 10.0 percent (53 - 86 mmol/mol) both inclusive 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 throughout the trial including the 5 weeks follow-up period (adequate contraceptive measures as required by local regulation or practice). Germany: Only highly effective methods of birth control are accepted (ie one that results in less than 1% per year failure rate when used consistently and correctly such as implants, injectables, combined oral contraceptives, some intrauterine device), or sexual abstinence or vasectomised partner. Japan: Adequate contraceptive measures are abstinence (not having sex), diaphragm, condom (by the partner), intrauterine device, sponge, spermicide or oral contraceptives - Treatment with any glucose lowering agents 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 bolus insulin in connection with intercurrent illness - Experienced more than 3 episodes of severe hypoglycaemia within 6 months prior to screening, and/or hypoglycaemia unawareness - History of pancreatitis (acute or chronic) - Screening calcitonin value above or equal to 50 ng/L (pg/mL) - Personal or family history of medullary thyroid carcinoma (MTC) or multiple endocrine neoplasia syndrome 2 (MEN 2) - Severe renal impairment defined as eGFR (estimated glomerular filtration rate) below 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 (NYHA) Class IV