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.

Primary Outcome Measures

1. Percentage of Participants Achieving Adapted systemic Juvenile Idiopathic Arthritis (sJIA) American College of Rheumatology (ACR) 30 Response
   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%.
2. Number of Participants with Adverse Events (AEs)
   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.

Secondary Outcome Measures

1. Percentage of Participants Achieving Adapted systemic Juvenile Idiopathic Arthritis (sJIA) American College of Rheumatology (ACR) 50 Response
   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.
2. Percentage of Participants Achieving Adapted systemic Juvenile Idiopathic Arthritis (sJIA) American College of Rheumatology (ACR) 70 Response
   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.
3. Percentage of Participants Achieving Adapted systemic Juvenile Idiopathic Arthritis (sJIA) American College of Rheumatology (ACR) 90 Response
   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.
4. Percentage of Participants Achieving Adapted systemic Juvenile Idiopathic Arthritis (sJIA) American College of Rheumatology (ACR) 100 Response
   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.
5. Change from Baseline in Number of Joints with Active Arthritis
   Change from Baseline in Number of Joints with Active Arthritis
6. Change from Baseline in Number of Joints with Limitation of Motion
   Change from Baseline in Number of Joints with Limitation of Motion
7. Change from Baseline in Childhood Health Assessment Questionnaire-Disability Index (CHAQ-DI)
   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.
8. Change From Baseline in Patient's Global Assessment (PtGA)
   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.
9. Change From Baseline in Physician's Global Assessment of Disease Activity (PhGA)
   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.
10. Change From Baseline in High-Sensitivity C-Reactive Protein (hsCRP)
    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.
11. Percentage of Participants with Absence of fever (> 38°C) Attributed to systemic Juvenile Idiopathic Arthritis (sJIA)
    Absence of fever (\> 38°C) Attributed to systemic Juvenile Idiopathic Arthritis (sJIA)
12. Change from Baseline in Glucocorticoid Dose
    Change from Baseline in Glucocorticoid Dose
13. Change from Baseline in Juvenile Arthritis Disease Activity Score (JADAS27-CRP)
    Juvenile Arthritis Disease Activity Score (JADAS27-CRP) will be assessed
14. Percentage of Participants Achieving Inactive Disease (ID) Status by Juvenile Arthritis Disease Activity Score (JADAS27)-CRP
    Inactive Disease (ID) status by 27-joint Juvenile Arthritis Disease Activity Score (JADAS27)-CRP will be assessed.
15. Percentage of Participants Achieving Minimal Disease Activity (MDA) by Juvenile Arthritis Disease Activity Score (JADAS27)-CRP
    Minimal Disease Activity (MDA) by 27-joint Juvenile Arthritis Disease Activity Score (JADAS27)-CRP will be assessed.
16. Percentage of Participants Achieving Clinical Remission by Juvenile Arthritis Disease Activity Score (JADAS27)-CRP
    Clinical Remission by 27-joint Juvenile Arthritis Disease Activity Score (JADAS27)-CRP will be assessed.