A Study to Test Whether Survodutide Helps People With Type 2 Diabetes Control Their Blood Sugar

Inclusion criteria: 1. Male or female, age ≥18 years at the time of signing informed consent, and at least the legal age of consent in countries where it is \>18 years 2. Diagnosed with type 2 diabetes mellitus (T2D) (e.g. American diabetes association (ADA)/European association for the study of diabetes (EASD) guidelines) and must meet requirements for one of background therapy parts A, B or C: 1. Part A: Naïve to insulin therapy and have not used oral or injectable anti-hyperglycaemic (diabetes) medication for at least 90 days prior to screening (Visit 1) and glycosylated haemoglobin A1c (HbA1c) ≥7.0 (≥53 mmol/mol) and \<9.5% (\<80 mmol/mol) as measured by the central laboratory at screening (Visit 1); 2. Part B: Treated with stable dose of oral antidiabetic medication (OAD) for 90 days prior to screening (Visit 1) as monotherapy or combination of: Maximum tolerated dose of metformin and/or Maximum tolerated dose of sulfonylurea and/or Maximum tolerated dose of sodium-glucose cotransporter 2 inhibitor (SGLT2i) and HbA1c ≥7.0% (≥53 mmol/mol) and \<10.5% (\<91 mmol/mol) as measured by the central laboratory at screening (Visit 1); 3. Part C: Stable use of basal insulin at a dose of ≥20 international units (IU)/day with or without stable dose of metformin and/or SGLT2i for 90 days prior to screening (Visit 1) and HbA1c ≥7.0% (≥53 mmol/mol) and \<10.5% (\<91 mmol/mol) as measured by the central laboratory at screening (Visit 1) 3. Body mass index (BMI) ≥23 kg/m2 at screening (Visit 1) 4. Signed and dated written informed consent in accordance with international council for harmonisation - good clinical practice (ICH-GCP) and local legislation prior to admission to the trial 5. Woman (or women) of childbearing potential (WOCBP) must be ready and able to use highly effective methods of birth control per international council for harmonisation of technical requirements for pharmaceuticals for human use M3 (R2) that result in a low failure rate of less than 1% per year when used consistently and correctly. 6. In the investigator's opinion, participants are well-motivated, capable, and willing to: Learn how to self-inject the investigational medicinal product (IMP), as required for this protocol (persons with physical limitations who are not able to perform the injections must have the assistance of an individual trained to inject the IMP); Inject the IMP or accept injection from a designated person; Follow study procedures for the duration of the study, including, but not limited to: follow lifestyle advice (for example, dietary restrictions and exercise plan), maintain a diary, complete required questionnaires, and handle the IMP as described in the instructions for use (IFU) Exclusion criteria: 1. Type 1 diabetes mellitus (T1D) or latent autoimmune diabetes in adults (LADA) 2. Treatment within 90 days before screening (Visit 1) up to and including randomisation (Visit 2) with any: glucagon-like peptide-1 receptor (GLP-1R) agonists including GLP-1R agonist/glucose-dependent insulinotropic polypeptide (GIP) combinations, amylin or incretin combinations; Glucose-lowering drugs other than stated in the inclusion criteria for each part (i.e. metformin, Sodium-Glucose Cotransporter 2 Inhibitor (SGLT2i), basal insulin, depending on the background therapy part); Glucose-lowering investigational drug; Any anti-obesity medication including bupropion/naltrexone, orlistat, phentermine, and phentermine/topiramate 3. History of ketoacidosis or hyperosmolar state or coma within the last 6 months before screening (Visit 1) up to and including randomisation (Visit 2) 4. Hypoglycaemia unawareness or a history of severe hypoglycaemia within the last 3 months before screening (Visit 1) up to and including randomisation (Visit 2) 5. Diabetic retinopathy or maculopathy currently under treatment, or that is reasonably anticipated to require such treatment over the duration of the study 6. Body weight change (self-reported) \>5% within 90 days before screening (Visit 1) 7. Previous or planned (during the trial period) treatment for obesity with surgery or a weight loss device, including any prior bariatric surgery. The following are allowed: (1) liposuction and/or abdominoplasty, if performed \>1 year before screening (Visit 1), (2) lap banding, if the band has been removed \>1 year before screening (Visit 1), (3) intragastric balloon, if the balloon has been removed \>1 year before screening (Visit 1), (4) duodenal-jejunal bypass sleeve, if the sleeve has been removed \>1 year before screening (Visit 1). 8. Answered "yes" to any of the suicide-related behaviours (Actual attempt, Interrupted attempt, Aborted attempt, Preparatory act or behaviour) or to the non-suicidal self-injurious behaviour question on the "Suicidal Behaviour" section of the Columbia-Suicide Severity Rating Scale (C-SSRS) related to the past 2 years before screening (Visit 1) up to and including randomisation (Visit 2) 9. Further exclusion criteria apply.