Insulin and Abatacept in Recently-diagnosed Type 1 Diabetes (IAA)

Inclusion Criteria: Age between 6 and 21 years and weight at least 20kg at Visit 1 Diabetes mellitus diagnosed according to ADA criteria (53) within 100 days of Visit 2 Presence of at least one antibody against insulin (if <10 days since starting insulin therapy), GAD, IA2 or ZnT8 Random C-peptide >0.3nmol/l, measured by a NATA-accredited pathology laboratory within 2 weeks of Visit 2 Willing to use CGM for the duration of the study Demonstrated ability to record home glucose measurements and insulin doses, as judged by the study doctor Willing to forego other forms of experimental treatment during the study Fully vaccinated against Covid-19, as recommended by the Australian Technical Advisory Group on Immunisation Up to date with other vaccinations recommended by the Australian Technical Advisory Group on Immunisation Willing to postpone any live vaccine immunisations for 3 months after treatment Exclusion Criteria: Clinical or laboratory evidence of active infection other than localised skin infection, including viral hepatitis, EBV, CMV or tuberculosis Immunodeficiency or chronic use of immunosuppressive drugs other than topical or inhaled glucocorticoid Vaccination with live or dead virus within 4 weeks of Visit 2 History of malignancy Pregnant or lactating, or of child-bearing potential not using an effective method of contraception Any pathology of the nasal passages that would preclude safe application of the nasal spray Any condition that would interfere with study conduct or participant safety