Efficacy and Safety of THDB0206 Compared to Insulin Lispro Injection in Participants With Type 1 Diabetes

1. Male or female participants, 18 to 75 years of age at informed consent (inclusive).
2. BMI between 18.0 and 30.0 kg/m² (inclusive).
3. T1DM diagnosed ≥6 months per WHO diabetes classification (2019).
4. On insulin therapy ≥6 months prior to screening.

5. Stable insulin regimen ≥3 months prior to screening (no change in insulin class), with or without metformin or alpha-glucosidase inhibitors; willing to follow multiple daily injections:

   1. Intermediate/long-acting insulin once or twice daily (e.g., NPH, glargine, detemir, degludec); plus prandial insulin 1\~3 times daily (or as per usual diet) (e.g., regular human insulin, lispro, aspart, glulisine).
   2. Premixed insulin ≥2 times per day.
6. Screening HbA1c between 7.0% and 11.0% (inclusive), measured by the central laboratory.

Exclusion Criteria:

1. Diabetes other than T1DM.
2. History of pancreatectomy.
3. Prior pancreatic and/or islet cell transplantation.
4. ≥1 episode of Level 3 hypoglycemia within 6 months before screening (requires external assistance).

5. Hepatic or renal impairment at screening (per local laboratory reference ranges):

   1. AST or ALT ≥3× ULN; and/or
   2. TBL ≥2× ULN (except Gilbert syndrome); and/or
   3. Estimated creatinine clearance \<45 mL/min (Cockcroft-Gault).
6. Known hypersensitivity/allergy to study insulin products or excipients, or to any component of the standardized test meal.
7. Blood transfusion or major blood loss within 3 months before screening; hemoglobinopathies, moderate-severe anemia, or other conditions that may interfere with HbA1c measurement.
8. Use of oral antihyperglycemics within 3 months before screening (except metformin and alpha-glucosidase inhibitors), or use of non-insulin injectables (e.g., GLP-1 receptor agonists).
9. Systemic corticosteroid therapy for ≥14 consecutive days within 3 months prior to screening (including IV, IM, SC, or oral routes; excluding topical, intraocular, intranasal, intra-articular, and inhaled use), or systemic corticosteroid therapy within 8 weeks prior to screening (except physiologic replacement for adrenal insufficiency), or anticipated need for prolonged systemic corticosteroid therapy during the study.
10. Use within 3 months before screening, or current use, of traditional medicines (herbal or proprietary Chinese medicines) with known glucose-lowering effects.