ADJUnct Semaglutide Treatment in Type 1 Diabetes

Inclusion Criteria: For an eligible subject, all inclusion criteria must be answered "yes" 1. Age ≥18 and ≤ 65 years 2. Patients with clinical diagnosis of T1D diagnosed for at least 12 months 3. Patient is on FDA- approved hybrid closed-loop system for ≥ 3 months 4. Willing to use once weekly semaglutide 5. Willing to share devices (HCL system) data uploads 6. HbA1c \>7.0% and \<10.0% 7. Body mass index ≥30 kg/m2 8. Has current glucagon product to treat severe hypoglycemia 9. Has current ketone meters to check ketones 10. Ability to provide informed consent before any trial-related activities Exclusion Criteria: 1. Age \<18 years and \>65 years 2. HbA1c ≤7.0 % or ≥ 10.0% at screening 3. Less than 12 months of insulin treatment 4. Use of unapproved insulin for HCL system. E.g. use of Fiasp in the Tandem Control-IQ system 5. Not willing to share the devices (HCL system) data uploads 6. Non compatible devices (e.g. pump, CGM or smart phones) for data transfer 7. Current use of multiple daily injection or inhaled insulin (Afrezza) 8. Patients with T1D using any glucose lowering medications other than insulin at the time of screening 9. Pregnancy, breast feeding, and positive pregnancy test during screening 10. Women of childbearing age wanting to become pregnant 11. Unwilling to use acceptable contraceptive methods (for both men and women) during the trial period 12. Current use (≥ 2 weeks of continuous use) of any steroidal medication, or anticipated long-term steroidal treatment (\>4 weeks continuously), during the study period 13. Use of GLP-1RA or weight loss medications in the past 3 month 14. Clinical diagnosis/history of gastroparesis or gastric motility disorders 15. Serum triglycerides \>500 mg/dL 16. Planning for bariatric surgery during the study period 17. eGFR below 45 ml/min/1.73 m\^2 using CKD-EPI formula 18. History of severe hypoglycemia in the previous 3 months 19. History of diabetic ketoacidosis requiring hospitalization in the past 3 months 20. History of allergy to any form of insulin, GLP-1RA or its excipients 21. History of any form of pancreatitis 22. History of stroke, myocardial infarction in the past 3 months 23. History of congestive heart failure class III or IV 24. History of acute or chronic liver disease 25. History of malignancy requiring chemotherapy, surgery or radiation in previous 5 years 26. Personal or family history of multiple endocrine neoplasia type 2 (MEN-2) or familial thyroid carcinoma or non-familial medullary thyroid carcinoma 27. Have a pacemaker, metal implants, or aneurysm clips or weigh \>330 lbs (exclusion only if doing MRI) 28. Use of investigational drugs within 5 half-lives prior to screening 29. Participation to other intervention trials during the study period 30. Any comorbidities or medical conditions such as severe psychiatric disorder that make a person unfit for the study at the discretion of the investigators