This is a single-center, single-arm Phase Investigational Intervention Trial (IIT) clinical trial aimed at evaluating the safety and efficacy of allogeneic regenerative islet transplantation for the treatment of brittle type 1 diabetes mellitus. Eighteen patients with brittle type 1 diabetes mellitus, who have inadequate blood glucose control despite intensified exogenous insulin therapy, will be enrolled. The primary endpoint is defined as the safety and improvement in blood glucose levels of the 12 months after allogeneic regenerative islet transplantation.

Inclusion Criteria:

1. Age 6-65 years, gender not specified.
2. Despite intensified exogenous insulin therapy, blood glucose control remains inadequate [glycated hemoglobin ≥7.5%, or TIR (time in range) <70%].
3. Able and willing to use the blood glucose meter provided by the sponsor, conduct self-blood glucose monitoring as required, and complete the patient log as instructed.
4. Fertile eligible subjects (male or female) must agree to use a reliable contraceptive method (hormonal or barrier method or abstinence) during the trial and for at least 90 days after the last dose; premenopausal female patients must have a negative pregnancy test before enrollment.
5. Diagnosed with type 1 diabetes for at least 1 year based on the World Health Organization (WHO) disease diagnostic criteria, and at least one positive result for diabetes-related autoantibodies [glutamic acid decarboxylase autoantibody (GADA), insulinoma-associated-2 autoantibody (IA-2A), insulin autoantibody (IAA), islet cell antibody (ICA), zinc transporter 8 antibody (ZaT8A)]. Experiencing two or more severe hypoglycemic events in the past year, with at least one severe hypoglycemic event in the past 3 months (severe hypoglycemia defined as blood glucose below 2.9 mmol/L or inability to self-correct during hypoglycemia).
6. Voluntarily participate and sign the informed consent form.

Exclusion Criteria:

1. Uncontrolled systemic infections, including but not limited to pulmonary tuberculosis, active hepatitis, a history of positive human immunodeficiency virus (HIV) testing, and positive syphilis treponemal antibody (TP);
2. Presence of significant organic lesions in vital organs such as the heart, lungs, or brain;
3. Complications of severe diabetes, including but not limited to retinal hemorrhage, diabetic foot, etc.;
4. Liver function tests with total bilirubin, ALT, and AST ≥2×ULN, and failure to normalize after drug treatment;
5. Untreated cancer or less than 1 year since cure;
6. Severe gastrointestinal dysfunction, gastrointestinal immune diseases, and inability to take immunosuppressant;
7. History of smoking, alcohol abuse, or drug misuse;
8. Severe mental or psychological disorders;
9. Various advanced metabolic diseases (such as hyperuricemia, etc.);
10. Participation in other clinical trials in the 3 months prior to enrollment;
11. Patients requiring long-term oral/intravenous administration of high-dose glucocorticoids due to various diseases;
12. Pregnant or lactating women;
13. Investigator judgment indicating clear evidence of severe, active, uncontrolled endocrine or autoimmune abnormalities other than type 1 diabetes;
14. Other situations judged by the investigator as unsuitable for participation in the trial.