The JIA ACR response criteria consisted of 6 core criteria:

• Physician global assessment of disease activity on a 0-100 mm VAS (0=very good and 100=very poor).
• Parent's or patients' global assessment of overall well-being on a 0-100 mm VAS (0=very well and 100=very poor).
• Functional ability (CHAQ: Childhood Health Assessment Questionnaire): 30 questions across 8 domains assessing the child's functional abilities. The total score was calculated as the average of the scores for each domain. It ranged from 0 (no disability) to 3 (very severe disability).
• Number of joints with active arthritis (as per ACR definition), ranging from 0 to 73.
• Number of joints with limited range of motion, ranging from 0 to 69.
• Index of inflammation: C-reactive Protein (CRP) levels The JIA ACR 30 response was achieved if 3 of any 6 core set variables improved by at least 30% from baseline of the core study, and no more than 1 variable worsening more than 30%

Participants who enrolled in the extension study. One patient enrolled with planned treatment secukinumab150 mg discontinued the study before receiving study treatment. This patient was not included in the analysis. At each time point, only participants with non-missing values were included in the analysis

The JIA ACR response criteria consisted of 6 core criteria:

• Physician global assessment of disease activity on a 0-100 mm VAS (0=very good and 100=very poor).
• Parent's or patients' global assessment of overall well-being on a 0-100 mm VAS (0=very well and 100=very poor).
• Functional ability (CHAQ): 30 questions across 8 domains assessing the child's functional abilities. The total score was calculated as the average of the scores for each domain (0 [no disability] to 3 [very severe disability]).
• Number of joints with active arthritis (as per ACR definition), ranging from 0 to 73.
• Number of joints with limited range of motion, ranging from 0 to 69.
• Index of inflammation: CRP levels The JIA ACR 50 responses were achieved if 3 of any 6 core set variables improved by at least 50% from baseline of the core study, and no more than 1 variable worsening > 30%

Participants who enrolled in the extension study. One patient enrolled with planned treatment secukinumab150 mg discontinued the study before receiving study treatment. This patient was not included in the analysis. At each time point, only participants with non-missing values were included in the analysis

The JIA ACR response criteria consisted of 6 core criteria:

• Physician global assessment of disease activity on a 0-100 mm VAS (0=very good and 100=very poor).
• Parent's or patients' global assessment of overall well-being on a 0-100 mm VAS (0=very well and 100=very poor).
• Functional ability (CHAQ): 30 questions across 8 domains assessing the child's functional abilities. The total score was calculated as the average of the scores for each domain (0 [no disability] to 3 [very severe disability]).
• Number of joints with active arthritis (as per ACR definition), ranging from 0 to 73.
• Number of joints with limited range of motion, ranging from 0 to 69.
• Index of inflammation: CRP levels The JIA ACR 70 responses were achieved if 3 of any 6 core set variables improved by at least 70%, from baseline of the core study, and no more than 1 variable worsening > 30%

Participants who enrolled in the extension study. One patient enrolled with planned treatment secukinumab150 mg discontinued the study before receiving study treatment. This patient was not included in the analysis. At each time point, only participants with non-missing values were included in the analysis

The JIA ACR response criteria consisted of 6 core criteria:

• Physician global assessment of disease activity on a 0-100 mm VAS (0=very good and 100=very poor).
• Parent's or patients' global assessment of overall well-being on a 0-100 mm VAS (0=very well and 100=very poor).
• Functional ability (CHAQ): 30 questions across 8 domains assessing the child's functional abilities. The total score was calculated as the average of the scores for each domain (0 [no disability] to 3 [very severe disability]).
• Number of joints with active arthritis (as per ACR definition), ranging from 0 to 73.
• Number of joints with limited range of motion, ranging from 0 to 69.
• Index of inflammation: CRP levels The JIA ACR 90 responses were achieved if 3 of any 6 core set variables improved by at least 90% from baseline of the core study, and no more than 1 variable worsening > 30%

Participants who enrolled in the extension study. One patient enrolled with planned treatment secukinumab150 mg discontinued the study before receiving study treatment. This patient was not included in the analysis. At each time point, only participants with non-missing values were included in the analysis

The JIA ACR response criteria consisted of 6 core criteria:

• Physician global assessment of disease activity on a 0-100 mm VAS (0=very good and 100=very poor).
• Parent's or patients' global assessment of overall well-being on a 0-100 mm VAS (0=very well and 100=very poor).
• Functional ability (CHAQ): 30 questions across 8 domains assessing the child's functional abilities. The total score was calculated as the average of the scores for each domain (0 [no disability] to 3 [very severe disability]).
• Number of joints with active arthritis (as per ACR definition), ranging from 0 to 73.
• Number of joints with limited range of motion, ranging from 0 to 69.
• Index of inflammation: CRP levels The JIA ACR 100 responses were achieved if 3 of any 6 core set variables improved with 100% from baseline of the core study, and no more than 1 variable worsening > 30%

Participants who enrolled in the extension study. One patient enrolled with planned treatment secukinumab150 mg discontinued the study before receiving study treatment. This patient was not included in the analysis. At each time point, only participants with non-missing values were included in the analysis

Inactive disease status was confirmed in a patient when all the following conditions were met:

• No joints with active arthritis
• No uveitis
• CRP value within normal limits for the laboratory where tested or, if elevated, not attributable to JIA
• Physician's global assessment of disease activity score ≤ 10mm
• Duration of morning stiffness attributable to JIA lasting ≥15 minutes.

Participants who enrolled in the extension study. One patient enrolled with planned treatment secukinumab150 mg discontinued the study before receiving study treatment. This patient was not included in the analysis. At each time point, only participants with non-missing values were included in the analysis

The JIA ACR response criteria consisted of 6 core criteria, one of which was the physician global assessment of disease activity. this assessment was conducted using a 100 mm VAS score, where 0 represented the best disease activity and 100 the worst. The change from baseline of the core study of the physician global assessment of disease activity was measured, with a negative change indicating improvement.

Participants who enrolled in the extension study. One patient enrolled with planned treatment secukinumab150 mg discontinued the study before receiving study treatment. This patient was not included in the analysis. At each time point, only participants with non-missing values were included in the analysis

The JIA ACR response criteria included six core components, one of which was the parent's or patients' global assessment of overall well-being. This assessment was conducted using a 100 mm VAS score, where 0 represented "very well" and 100 "very poor". The change from baseline of the core study in the parent's or patients' global assessment of overall well-being was measured, with a negative change indicating improvement

Participants who enrolled in the extension study. One patient enrolled with planned treatment secukinumab150 mg discontinued the study before receiving study treatment. This patient was not included in the analysis. At each time point, only participants with non-missing values were included in the analysis

The JIA ACR response criteria included six core components, one of which was the functional ability, measured by the CHAQ. The CHAQ questionnaire consisted of 30 questions across 8 domains: dressing/grooming, arising, eating, walking, hygiene, reach, grip, and activities. Each domain was scored on a 4-point scale, and the total score was calculated as the average of the scores for each domain. The total score ranged from 0 (no disability) to 3 (very severe disability). The change from baseline of the core study in the CHAQ was measured, with a negative change indicating improvement.

Participants who enrolled in the extension study. One patient enrolled with planned treatment secukinumab150 mg discontinued the study before receiving study treatment. This patient was not included in the analysis. At each time point, only participants with non-missing values were included in the analysis

The JIA ACR response criteria included six core components, one of which was the number of joints with active arthritis. This was determined using the ACR definition, which identifies active arthritis as any joint with swelling or, in the absence of swelling, limitation of motion accompanied by either pain on motion or tenderness not due to deformity. The active joint count ranged from 0 to 73. The change from baseline of the core study in the number of active joints was measured, with a negative change indicating improvement.

Participants who enrolled in the extension study. One patient enrolled with planned treatment secukinumab150 mg discontinued the study before receiving study treatment. This patient was not included in the analysis. At each time point, only participants with non-missing values were included in the analysis

The JIA ACR response criteria included six core components, one of which was the number of joints with limited range of motion. A total of 69 joints were assessed for limitation of motion. The change from baseline of the core study in the number of joints with limited range of motion was measured, with a negative change indicating improvement.

Participants who enrolled in the extension study. One patient enrolled with planned treatment secukinumab150 mg discontinued the study before receiving study treatment. This patient was not included in the analysis. At each time point, only participants with non-missing values were included in the analysis

The JIA ACR response criteria included six core components, one of which was CRP levels, an inflammation biomarker. Serum concentrations of CRP were determined, and the change from baseline of the core study was assessed, with negative changes indicating improvement.

Participants who enrolled in the extension study. One patient enrolled with planned treatment secukinumab150 mg discontinued the study before receiving study treatment. This patient was not included in the analysis. At each time point, only participants with non-missing values were included in the analysis

The JADAS-27 was used for assessment of disease activity, and it included 4 measures:

• Physician global assessment of disease activity (VAS range: 0 to 10; where 0=very good and 100=very poor)
• Parent/participant global assessment of well-being (VAS range: 0 to 10; 0=very well and 100=very poor)
• Count of joints with active disease (range: 0 to 27; where 0= no disease activity and 27= maximum disease activity)
• Index of inflammation determined by CRP concentration, calculated as: (CRP (mg/l) -10)/10. Before calculation, CRP values <10 mg/l were converted to 10 and CRP values >110 mg/l were converted to 110. The normalized scale ranged from 0 to 10; where 0= no disease activity and 10= maximum disease activity.

JADAS-27 score was calculated as the sum of the score of its 4 components, ranging from 0 to 57 where 0= no disease activity and 57= maximum disease activity. The change from baseline of the core study was assessed. A negative change from baseline indicated improvement.

Participants who enrolled in the extension study. One patient enrolled with planned treatment secukinumab150 mg discontinued the study before receiving study treatment. This patient was not included in the analysis. At each time point, only participants with non-missing values were included in the analysis

The JADAS-27 was used for assessment of disease activity, and it included 4 measures:

• Physician global assessment of disease activity (VAS range: 0 to 10; where 0=very good and 100=very poor)
• Parent/participant global assessment of well-being (VAS range: 0 to 10; 0=very well and 100=very poor)
• Count of joints with active disease (range: 0 to 71; where 0= no disease activity and 71= maximum disease activity)
• Index of inflammation determined by CRP concentration, calculated as: (CRP (mg/l) -10)/10. Before calculation, CRP values <10 mg/l were converted to 10 and CRP values >110 mg/l were converted to 110. The normalized scale ranged from 0 to 10; where 0= no disease activity and 10= maximum disease activity.

JADAS-27 score was calculated as the sum of the score of its 4 components, ranging from 0 to 101 where 0= no disease activity and 101= maximum disease activity. The change from baseline of the core study was assessed. A negative change from baseline indicated improvement.

Participants who enrolled in the extension study. One patient enrolled with planned treatment secukinumab150 mg discontinued the study before receiving study treatment. This patient was not included in the analysis. At each time point, only participants with non-missing values were included in the analysis

The following 16 entheseal sites were assessed for the presence or absence of tenderness (enthesitis) on each side of the body:

• Anterior Entheses: Greater trochanter of the Femur; Medial condyle of the femur; Lateral condyle of the femur
• Posterior Entheses: Greater tuberosity of humerus; medial epicondyle of humerus; lateral epicondyle of humerus, Achilles tendon; and calcaneal insertion of the plantar fascia.

Tenderness on examination was recorded as either present (1) or absent (0) for each of the 16 sites, The total enthesitis count ranged from 0 to 16.

The change from baseline of the core study was assessed. A negative change from baseline indicated improvement

Participants who enrolled in the extension study. One patient enrolled with planned treatment secukinumab150 mg discontinued the study before receiving study treatment. This patient was not included in the analysis. At each time point, only participants with non-missing values were included in the analysis

The dactylitis count was the number of fingers and toes presenting with swelling and inflammation.

Swelling and inflammation on examination was recorded as either present (1) or absent (0) for each of the 20 sites, The total dactylitis count ranged from 0 to 20.

The change from baseline of the core study was assessed. A negative change from baseline indicated improvement

Participants who enrolled in the extension study. One patient enrolled with planned treatment secukinumab150 mg discontinued the study before receiving study treatment. This patient was not included in the analysis. At each time point, only participants with non-missing values were included in the analysis

Serum concentration of secukinumab over time. Blood samples for pharmacokinetics were taken pre-dose at the scheduled time points.

Participants who enrolled in the extension study and received at least one dose of study treatment with quantifiable pharmacokinetic (PK) measurements of secukinumab. Participants with dose escalations were not included in the analysis post up-titration.

Number of participants with treatment-emergent Anti-Drug Antibodies (ADAs) of secukinumab. Blood samples were collected for immunogenicity (anti-AIN457 antibodies) assessments.

Participants who enrolled in the extension study and received at least one dose of study treatment with immunogenicity (anti-AIN457 antibodies) measurements of secukinumab in both the core and extension study