Diabetes AutoimmunitY Withdrawn in Established Patients (DAY)

The study is a prospective, randomized, double-blind, placebo-controlled, multicenter trial in subjects with established T1D.

The study will include 216 male or female subjects aged 12 to 35 years diagnosed with T1D, as defined by the American Diabetes Association (ADA) criteria and meeting enrollment criteria as follows. Initial enrollment will be restricted to subjects aged 18-35 until an analysis of data from subjects with 3 months' exposure to drug confirms safety. Upon completion of this assessment, enrollment will be open without further restrictions for subjects aged 12-35.

Eligibility Criteria:
Inclusion Criteria:

1. Diagnosis of Type 1 Diabetes Mellitus based on American Diabetes Association (ADA) criteria and within 1.0 to 5.0 years from diagnosis, defined as the first day of insulin administration.
2. Adequate glycemic control for \>14 days, defined as 3 consecutive fasting glucose levels by self-administered blood glucose (SMBG) or lab testing \<130 mg/dL.
3. Age at randomization of 12.0 - \<18.0 years (adolescent), 18.0 - \<36.0 years of age (adult) .
4. HbA1c \<8.5% based on point-of-care or local lab measurement.

   • Measurement can be repeated every 5-7 days if \>8.5%.
5. Presence of antibodies to at least one of the following antigens: GAD-65, IA-2, ZnT8; or insulin.
6. Peak C-peptide during screening 4-hour mixed meal tolerance test (MMTT) ≥ 0.2pmol/mL.
7. Willingness to wear a continuous glucose monitoring (CGM) device for specified periods of time.
8. Written informed consent, including authorization to release health information and assent for adolescent subjects.
9. Willingness and ability of subject or adult guardian to comply with all study procedures of the study protocol, including attending all clinic visits.

Exclusion Criteria:

1. Body Mass Index (BMI) \>30 kg/m2 for adults; \>95 percentile BMI-for-age for subjects under 18 years of age.
2. Previous immunotherapy for T1D.
3. Diagnosis of liver disease or hepatic enzymes, as defined by ALT and/or AST ≥ 2.5 times the upper limit of normal (ULN).
4. Hematology: white blood cells (WBC) \<3 x 109/L; platelets \<100 x 109/L; hemoglobin \<10.0 g/dL. (Low WBC values may be repeated every 3-7 days, and results to be discussed with the Medical Monitor.)
5. Serum creatinine \>1.5 times ULN.
6. History of malignancy, except for cancers in remission \>5 years, or basal cell or in situ squamous cell carcinoma of the skin.
7. Significant cardiovascular disease (including inadequately controlled hypertension), history of myocardial infarction, angina, use of anti-anginal medicines (e.g., nitroglycerin), or abnormal stress test, which, in the opinion of the Principal Investigator (PI), would interfere with participation in the trial.
8. Immunosuppressive therapy (systemic corticosteroids, cyclosporine, azathioprine, or biologics) within 30 days of screening.
9. Current or prior (within the last 30 days) use of metformin, sulfonylureas, glinides, thiazolidinediones, GLP1-RAs, DPP-IV inhibitors, pramlintide, or SGLT-2 inhibitors.
10. Current use of verapamil or α-methyldopa.
11. History of any organ transplant, including islet cell transplant.
12. Active autoimmune or immune deficiency disorder other than T1D or well-controlled autoimmune thyroid disease (e.g., sarcoidosis, rheumatoid arthritis, moderate-to-severe psoriasis, inflammatory bowel disease, and other autoimmune conditions that may require treatment with TNF or other biologics), unless approved by the Medical Monitor.
13. Thyroid-stimulating hormone (TSH) at screening \>2.5 mIU/L.
14. History of adrenal insufficiency.
15. Evidence of infection with HBV (as defined by hepatitis B surface antigen, HBsAg), HCV (anti-HCV antibodies), or HIV.
16. Positive urine pregnancy test: Females of childbearing potential must be excluded if they have a positive urine pregnancy test at screening or randomization or if they are not using medically acceptable methods of birth control. Acceptable methods of birth control include oral or transdermal contraceptives, condom, spermicidal foam, IUD, progestin implant or injection, abstinence, vaginal ring, or sterilization of partner. The reason for non-childbearing potential, such as bilateral tubal ligation, bilateral oophorectomy, hysterectomy, or 1 year or more postmenopausal must be specified in the subject's Case Report Form (CRF).
17. Males of reproductive potential who are unwilling to use medically acceptable birth control, unless the female partner is postmenopausal or surgically sterile.
18. Any social condition or medical condition that would, in the opinion of the PI, prevent complete participation in the study or would pose a significant hazard to the subject's participation.
19. Anticipated major surgery during the duration of the trial, which could interfere with participation in the trial.
20. History of drug or alcohol dependence within 12 months of screening.
21. Psychiatric disorder that would prevent subjects from giving informed consent.
22. Participation in other studies involving the administration of an investigational drug or device, including the administration of an experimental agent for T1D, at any time, or use of an experimental device for T1D within 30 days prior to screening, unless approved by the Medical Monitor.