Platform Trial to Delay Stage 3 Diabetes: Comparing Teplizumab With ATG

This is a 2-arm, multi-center, open label study to learn if ATG works the same or better than teplizumab in delaying or preventing Stage 3 Type 1 diabetes. Participants will be administered either 2 infusions of ATG or 14 infusions of teplizumab and will then be followed for at least 12-48 months after administration, depending on timepoint enrolled into the study. If the primary endpoint demonstrates a positive signal and as decided by TrialNet, there is potential for a study extention. This would extend follow-up visits for a possible study duration of about 9 years among the earliest enrollees of the initial study.