A multi-center, placebo-controlled, double blind, 1:1 randomized clinical trial testing low-dose ATG vs. placebo in pre-stratified ATG responders and non-responders in participants with Stage 3 T1D followed by open label combination therapy with either verapamil or no further treatment on a 1:1 basis.

Who can Participate

Diagnosis of Stage 3 T1D as defined by ADA criteria within 100 days in those aged 6-35 years who weigh at least 30 kg. INCLUSION: 1. Age 6 -35 years old at time of signing informed consent. 2. Fulfill the ADA criteria for diagnosis of T1D within 100 days of randomization. 3. Must be willing to provide informed consent or assent with a parent or legal guardian providing informed consent if < 18 years of age. 4. HbA1c of less than or equal to 12%. 5. Positive for at least one islet-cell autoantibody; GADA, mIAA (if obtained within 10 days of the onset of insulin therapy), IA-2A, ICA, or ZnT8A. 6. Must have stimulated peak C-peptide of ≥0.2 pmol/mL measured during mixed-meal tolerance test (MMTT) conducted at least 21 days after the diagnosis of diabetes. 7. Enrollees must be willing to comply with intensive diabetes management. 8. Body weight must be ≥ 30.0 kg for study agent administration. 21 9. Participants who are CMV and/or EBV seronegative at screening must be CMV and/or EBV PCR negative and may not have had signs or symptoms of a CMV and/or EBV compatible illness prior to randomization. 10. Female participants with reproductive potential must have a negative pregnancy test at screening and be willing to avoid pregnancy for the duration of treatment and until 3 months after ATG and verapamil administration. In addition, female participants with reproductive potential who are sexually active will be instructed to use a highly effective contraceptive method throughout the trial. 11. Male participants of reproductive age must use an adequate contraceptive method for the duration of trial. 12. The following additional inclusion criteria regarding vaccines must be met: a. More than 4 weeks from immunization with a live viral vaccine b. Be up to date on all recommended vaccinations based on age of participant* c. Receive non-live influenza vaccination at least 2 weeks prior to randomization when vaccine for the current or upcoming flu season is available d. Willingness to forgo vaccines (other than killed influenza or COVID-19) during the 3 months after the ATG treatment period 13. Participants must be willing to practice public health prevention measures such as social distancing, masking, and good hand hygiene, and/or receive therapeutics such as monoclonal antibodies and antivirals as directed by the study and recommended by local health authorities to prevent SARS-Cov-2 infection. * Adult participants must be fully immunized. Pediatric participants who have not completed their primary vaccination schedule must receive all vaccinations allowable per local public health immunization guidelines for their current age prior to study drug delivery. Any remaining vaccinations should be given and continue per the schedule at least 3 months after ATG is administered. For COVID-19 vaccination, all participants will be strongly encouraged to be up-to-date with COVID-19 vaccine(s) as indicated by state-specific guidelines at least 2 weeks prior to randomization. EXCLUSION One or more screening laboratory values as stated: a. Leukocytes <3,000/μL b. Neutrophils <1,500/μL c. Lymphocytes <800/μL d. Platelets <100,000/μL e. Hemoglobin <6.2 mmol/L (10.0 g/dL) f. Potassium >5.5 mmol/L or <3.0 mmol/L g. Sodium >150 mmol/L or <130 mmol/L h. AST or ALT ≥ 2.0 times the upper limits of normal i. Bilirubin ≥ 1.5 times upper limit of normal 2. History of immune deficiency 3. Current or ongoing use of non-insulin pharmaceuticals that affect glycemic control within 7 days of screening visit.

Study ID