MELD-ATG

Have given written informed consent to participate or have a parent or legal guardian provide informed consent if the subject is under the age of consent (age may vary in different countries; <16 years of age in UK)

Age ≥7 years <25 years at consent

Must have a diagnosis of T1D of within 6 weeks duration at screening

Must have at least two diabetes-related autoantibody present at screening

Must have random C-peptide levels ≥200 pmol/L measured at screening

Must be Epstein-Barr virus (EBV PCR) negative within two weeks of randomization if EBV seronegative at screening

Be at least 6 weeks from last live immunization at randomisation

Participants are required to receive killed influenza vaccination at least 2 weeks prior to randomization when vaccine for the current or upcoming flu season is available

Be willing to forgo live vaccines for 3 months following last dose of study drug

Be willing to use appropriate contraception if sexually active

Be willing to comply with intensive diabetes management

Normal screening values for complete blood count (CBC), renal function and electrolytes (CMP).

Be immunodeficient or have clinically significant chronic lymphopenia: (Leukopenia (< 3,000 leukocytes /µL), neutropenia (<1,500 neutrophils/µL), lymphopenia (<800 lymphocytes/µL), or thrombocytopenia (<100,000 platelets/µL).

Have active signs or symptoms of acute infection at the time of treatment

Have evidence of prior or current tuberculosis infection as assessed by purified protein derivative (PPD), interferon gamma release assay (IGRA) or by history

Be currently pregnant or lactating, or anticipate getting pregnant within the two year study period

Require use of other immunosuppressive agents including chronic use of systemic steroids

Have evidence of current or past human immunodeficiency virus (HIV), Hepatitis B or Hepatitis C infection

Have any complicating medical issues or abnormal clinical laboratory results that may interfere with study conduct, or cause increased risk to include pre-existing cardiac disease, chronic obstructive pulmonary disease (COPD), sickle cell disease, neurological, or blood count abnormalities

Have a history of malignancies other than skin

Evidence of liver dysfunction with aspartate aminotransferase (AST) or alanine transaminase (ALT) greater than 3 times the upper limits of normal

Evidence of renal dysfunction with creatinine greater than 1.5 times the upper limit of normal

Vaccination with a live virus within the last 6 weeks

Current or ongoing use of non-insulin pharmaceuticals that affect glycemic control within prior 7 days of screening

Active participation in another T1D treatment study in the previous 30 days

Prior treatment with abatacept or anti-cd3

Known allergy to ATG

Prior treatment with ATG or known allergy to rabbit derived products

Any condition that in the investigator's opinion may adversely affect study participation or may compromise the study results