Study of Oral Upadacitinib and Subcutaneous/Intravenous Tocilizumab to Evaluate Change in Disease Activity, Adverse Events and How Drug Moves Through the Body of Pediatric and Adolescent Participants With Active Systemic Juvenile Idiopathic Arthritis.

ACR criteria measure improvements in tender and swollen joint counts, patient assessments of pain, global disease activity and physical function, physician global assessment of disease activity and acute phase reactant. ACR 30 Response is defined as absence of fever [> 38°C] in the previous 1 week preceding evaluation and improvement of ≥ 30% of the 6 variables of the JIA core set with no more than 1 variable worsening by > 30%.

An AE is defined as any untoward medical occurrence in a patient or clinical investigation in which a participant is administered a pharmaceutical product which does not necessarily have a causal relationship with this treatment.

ACR criteria measure improvements in tender and swollen joint counts, patient assessments of pain, global disease activity and physical function, physician global assessment of disease activity and acute phase reactant. ACR 50 Response is defined as absence of fever [> 38°C] in the previous 1 week preceding evaluation and improvement of ≥ 50% of the 6 variables of the JIA core set.

ACR criteria measure improvements in tender and swollen joint counts, patient assessments of pain, global disease activity and physical function, physician global assessment of disease activity and acute phase reactant. ACR 70 Response is defined as absence of fever [> 38°C] in the previous 1 week preceding evaluation and improvement of ≥ 70% of the 6 variables of the JIA core set.

ACR criteria measure improvements in tender and swollen joint counts, patient assessments of pain, global disease activity and physical function, physician global assessment of disease activity and acute phase reactant. ACR 90 Response is defined as absence of fever [> 38°C] in the previous 1 week preceding evaluation and improvement of ≥ 90% of the 6 variables of the JIA core set.

ACR criteria measure improvements in tender and swollen joint counts, patient assessments of pain, global disease activity and physical function, physician global assessment of disease activity and acute phase reactant. ACR 100 Response is defined as absence of fever [> 38°C] in the previous 1 week preceding evaluation and improvement of ≥ 100% of the 6 variables of the JIA core set.

Change from Baseline in Number of Joints with Active Arthritis

Change from Baseline in Number of Joints with Limitation of Motion

The CHAQ-DI consists of 30 items and assesses function in 8 areas: dressing and grooming, arising, eating, walking, hygiene, reach, grip, and activities. There are 5 response options ranging from no difficulty to unable to do, scored 0 to 3, and not applicable.

Participants rated their disease activity for the past 24 hours using a Patient's Global Assessment of Disease Activity Global visual analogue scale (VAS). The range is 0 to 100 mm, with 0 representing no disease activity and 100 representing severe disease activity. Negative values indicate improvement from baseline.

Participants rated their disease activity for the past 24 hours using a Patient's Global Assessment of Disease Activity Global visual analogue scale (VAS). The range is 0 to 100 mm, with 0 representing no disease activity and 100 representing severe disease activity. Negative values indicate improvement from baseline.

High sensitivity C-reactive protein was analyzed by a central laboratory. The median percent change from baseline in CRP is assessed at each time point.

Absence of fever (> 38°C) Attributed to systemic Juvenile Idiopathic Arthritis (sJIA)

Change from Baseline in Glucocorticoid Dose

Juvenile Arthritis Disease Activity Score (JADAS27-CRP) will be assessed

Inactive Disease (ID) status by 27-joint Juvenile Arthritis Disease Activity Score (JADAS27)-CRP will be assessed.

Minimal Disease Activity (MDA) by 27-joint Juvenile Arthritis Disease Activity Score (JADAS27)-CRP will be assessed.

Clinical Remission by 27-joint Juvenile Arthritis Disease Activity Score (JADAS27)-CRP will be assessed.