The purpose of this study is to find out if baricitinib can delay the onset of clinical type 1 diabetes (T1D) in people who are at high risk to develop T1D. Participation in the study will last up to approximately 5 years.

Inclusion Criteria:

• Have a history of at least one documented occasion of at least two diabetes-related autoantibodies, AND one occasion of at least two diabetes-related autoantibodies obtained at screening or prescreening
• Have Stage 1b or Stage 2 type 1 diabetes
• Have a body weight of ≥8 kilograms (kg) (18 pounds) at screening

Exclusion Criteria:

• Have any other type of diabetes
• Have uncontrolled high blood pressure
• Have had a heart attack, heart disease, stroke, or heart failure
• Have a history or high risk of venous thromboembolism, lymphoproliferative disease or malignancy
• Have a current or recent clinically serious infection

Anonymized individual patient level data will be provided in a secure access environment upon approval of a research proposal and a signed data sharing agreement.

Data are available 6 months after the primary publication or approval of the indication studied in the US and EU, whichever is later. Data will be indefinitely available for requesting.

A research proposal must be approved by an independent review panel and researchers must sign a data sharing agreement.