RecruitingPhase 3Drug trialA Study to Investigate Efficacy and Safety of Teplizumab Compared With Placebo in Participants 1 to 25 Years of Age With Stage 3 Type 1 DiabetesThis is a multicenter, randomized, double-blind, parallel, placebo-controlled Phase 3, 2-arm study for treatment. The purpose of this study is to measure change in glycemic control and prandial insulin independency over 52 weeks with teplizumab compared with placebo, both administered by intravenous (IV) infusion, in participants with recently diagnosed Stage 3 type 1 diabetes (T1D) aged 1 to 25 years, on standard insulin therapy.