Tirzepatide Use in People With Obesity and Type 1 Diabetes

Inclusion Criteria: 1. Informed consent obtained before any trial-related activities. 2. Male or female, adults. 3. Documented diagnosis of T1DM (per ADA 2024definition/criteria) for at least 1 year before screening visit with C-peptide level of less than 0.01nm/L. 4. Body mass index (BMI) ≥ 27.0 kg/m2 5. History of at least one self-reported unsuccessful dietary effort to lose body weight. 6. Must be using a Continuous Glucose Monitoring (CGM) device for at least 2 months before the screening visit and be willing to wear a CGM device for the duration of the study. Exclusion Criteria: 1. Diabetes related: * Glycated hemoglobin (HbA1c) ≥86 mmol/mol (10%) as measured by the central laboratory at screening. * Treatment with a glucagon-like peptide-1 receptor agonist within 180 days before screening. * Preproliferative or proliferative retinopathy * Experienced diabetic ketoacidosis within 6 months of screening visit. * Experienced severe hypoglycemia (Level 3) within 6 months of screening visit. 2. Obesity-related: * A self-reported change in body weight \>5 kg (11 lbs) within 90 days before screening irrespective of medical records. * Treatment with any medication for the indication of obesity within the past 90 days before screening. * Previous or planned (during the trial period) obesity treatment with surgery or a weight-loss device. However, the following are allowed: (1) liposuction and/or abdominoplasty, if performed \>1 year before screening; (2) lap banding, if the band has been removed \>1 year before screening; (3) intragastric balloon, if the balloon has been removed \>1 year before screening; or (4) duodenal-jejunal bypass sleeve, if the sleeve has been removed \>1 year before screening. * Uncontrolled thyroid disease, defined as thyroid stimulating hormone \>6.0 mIU/L or \<0.4 mIU/L as measured by the central laboratory at screening. 3. Mental health: * History of major depressive disorder within 2 years before screening. * Diagnosis of other severe psychiatric disorder (e.g. schizophrenia, bipolar disorder). * A Patient Health Questionnaire-9 score of ≥15 at screening. * A lifetime history of a suicidal attempt. * Suicidal behavior within 30 days before screening. * Suicidal ideation corresponding to type 4 or 5 on the Columbia-Suicide Severity Rating Scale within the past 30 days before screening. 4. General safety: * Use of non-herbal Chinese medicine or other non-herbal local medicine with unknown/unspecified content within 90 days before screening. * Presence of acute pancreatitis within the past 180 days prior to the day of screening. * History or presence of chronic pancreatitis. * Calcitonin ≥100 ng/L as measured by the central laboratory at screening. * Personal or first-degree relative(s) history of multiple endocrine neoplasia type 2 or medullary thyroid carcinoma. * Renal impairment measured as estimated glomerular filtration rate value of \<15 mL/min/1.73m2 as defined by KDIGO 2012 by the central laboratory at screening. * History of malignant neoplasms within the past 5 years prior to screening. Basal and squamous cell skin cancer and any carcinoma in-situ are allowed. * Any of the following: myocardial infarction, stroke, hospitalization for unstable angina, or transient ischemic attack within the past 60 days prior to screening. * Subject presently classified as being in New York Heart Association Class IV. * Surgery scheduled for the duration of the trial, except for minor surgical procedures, in the opinion of the investigator. * Known or suspected abuse of alcohol or recreational drugs. * Known or suspected hypersensitivity to trial product(s) or related products. * Previous participation in this trial. Participation is defined as signed informed consent. * Participation in another clinical trial within 90 days before screening. * Other subject(s) from the same household participating in any semaglutide trial. * Female who is pregnant, breast-feeding, or intends to become pregnant, or is of child-bearing potential and not using a highly effective contraceptive method. * Any disorder, unwillingness, or inability, not covered by any of the other exclusion criteria, which in the investigator's opinion, might jeopardize the subject's safety or compliance with the protocol.