A Study of Baricitinib (LY3009104) in Participants From 1 Year to Less Than 18 Years Old With Systemic Juvenile Idiopathic Arthritis (sJIA)

Inclusion Criteria:

• Participants must have a diagnosis of systemic Juvenile Idiopathic Arthritis (sJIA)as defined by International League of Associations for Rheumatology (ILAR) criteriawith onset before the age of 16 years

• Participants must have at least 2 active joints at screening and baseline

• Cohort 1 (IL-6 inhibitor therapy naive): Participants who are at least 1 year andless than 18 years of age, except in countries that restrict use of tocilizumab inparticipants less than 2 years of age

• Cohort 2 (open-label baricitinib): Participants who are at least 1 year and lessthan 18 years of age

Exclusion Criteria:

• Participants must not have polyarticular JIA (positive or negative for rheumatoidfactor), extended oligoarticular JIA, enthesitis-related JIA, or juvenile psoriaticarthritis

• Participants must not have persistent oligoarticular arthritis as defined by theILAR criteria

• Participants must not have a history or presence of any autoimmune inflammatorycondition other than JIA

• Participants must not have active anterior uveitis or are receiving concurrenttreatment for anterior uveitis

• Participants must not have active fibromyalgia or other chronic pain conditionsthat, in the investigator's opinion, would make it difficult to appropriately assessdisease activity for the purposes of this study

• Participants must not have biologic features of Macrophage Activation Syndrome (MAS)over the past 12 weeks

• Participants must not have a current or recent (<4 weeks prior to baseline)clinically serious infection

• Participants must not have a positive test for hepatitis B virus

• Participants must not have evidence of active tuberculosis (TB) or untreated latentTB