Treatment With hOKT3gamma1(Ala-Ala) in T1DM

This is a 2-arm, open-label phase II trial involving 0 or 3 cycles of treatment 6 months apart with hOKT3γ1 (Ala-Ala), over the first year of disease in participants with new onset T1DM. Each cycle consists of 12 daily doses of hOKT3γ1 (Ala-Ala). Participants will be randomized in a ratio of 2:1 to either the experimental arm or the control arm and will be stratified by study site. To be eligible, participants must be: male or female between 7-30 years of age, diagnosed with T1DM within the past 6 weeks, have a body weight ≥26 kg at the time of enrollment and have detectable anti-GAD, anti-ICA512/IA-2, or insulin autoantibodies (if the participant has been on insulin ≤10 days). Participants randomized to the experimental group will start the first cycle of hOKT3γ1 (Ala-Ala) within 4-8 weeks of T1DM diagnosis. Each participant randomized to the experimental group will receive 3 cycles of drug treatment, separated by 6 months each. Each cycle consists of 12 days of drug treatment. Both groups will undergo the Mixed Meal Stimulated C-Peptide Test and receive blood draws for mechanistic studies on the same schedule.