PRISE (Personalized Response and Immunologic Surveillance of Endogenous C-Peptide Preservation in New, Recent, and Established Onset Type 1 Diabetes Treated With Human Anti-Thymocyte Globulin [h-ATG]) Study

This Phase 3, multicenter, randomized, double-blind, placebo-controlled study will evaluate the efficacy, safety, and tolerability of SAB-142, a fully human anti-thymocyte globulin (h-ATG), in participants aged 5 to 40 years with Stage 3 type 1 diabetes (T1D). The study will enroll participants with recent-onset T1D (\>100 days to \0.2 nmol/L. Participants will be randomized in a 2:1 ratio to receive SAB-142 or placebo in addition to standard diabetes care. The primary objective is to determine whether SAB-142 preserves beta-cell function over 12 months as measured by stimulated C-peptide response during a mixed meal tolerance test (MMTT). External data from the SAB-142-201 SAFEGUARD study will be incorporated to include participants with new-onset T1D (\

Inclusion Criteria: 1. Participant and/or appropriate legal guardian for participants below the legal age of consent must have given written informed consent and/or assent according to local, regional and/or country specific guidance before any study-related activities are carried out and must be able to understand the full nature and purpose of the trial, including possible risks and adverse effects. Participants and legal guardians must be capable of providing informed consent and not be incapacitated. 2. Males and females 5-40 years old\*, inclusive, at the time of randomisation. \* Note: Age step-down rules apply, as described in protocol Section 6.1. 3. Weight ≥16.0 kg at time of randomisation. Participants age 18-40 will have a body mass index (BMI) between 16 to 32 (inclusive). 4. Participant has received a diagnosis of T1D according to American Diabetes Association criteria (refer Section 22.1) as following: * For Cohort 2: within \>100 days but \