An Extension Study of Subcutaneous Secukinumab in Patients With Juvenile Psoriatic Arthritis (JPsA) and Enthesitis Related Arthritis (ERA)

This study is an extension of a previous core study (NCT03031782 \[CAIN457F2304\]) aiming to assess the long-term efficacy, safety, and tolerability of secukinumab treatment in patients who completed the core study and chose to participate in the extension study. The primary objective was to gather comprehensive data on the efficacy and safety of secukinumab over an extended period.

At Week 104 of the core study, all eligible patients could opt to roll over to the extension study and continue receiving secukinumab at either 75 mg or 150 mg, as they were at the Week 100 visit of the core study. The treatment involved subcutaneous injections using pre-filled syringes (PFS). The duration of patient participation could range from a minimum of one year to a maximum of four years, or until one of the following conditions was met: the drug was locally approved, marketed, and reimbursed, secukinumab could be provided free of charge to patients in compliance with local guidelines, or a maximum of 4 years study duration.

During the extension study (starting from Week 108), to maintain a high proportion of clinically meaningful response during the entire duration of the extension study, the dosing options available, at the Investigator's discretion, were as follows:

* The dose could be escalated from 75 mg to 150 mg for patients whose signs and symptoms were not fully controlled with the current dose of 75 mg and might improve with a higher dose as judged by the investigator

* Further, the dose could be escalated to 300 mg for patients weighing 50 kg and over currently on the 150 mg dose whose signs and symptoms were not fully controlled and might improve further with an increase in dose as judged by the investigator

* Dose escalation from secukinumab 75 mg to 300 mg had to be done in two steps (first 150 mg then 300 mg if the patient weighed 50 kg or over and based on the investigator's judgement), also considering the gap between the two escalations to review the response

Primary Outcome Measures

1. Percentage of Participants With Juvenile Idiopathic Arthritis American College of Rheumatology (JIA ACR) 30 Response
   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%

Secondary Outcome Measures

1. Percentage of Participants With JIA ACR 50 Response
   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%
2. Percentage of Participants With JIA ACR 70 Response
   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%
3. Percentage of Participants With JIA ACR 90 Response
   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%
4. Percentage of Participants With JIA ACR 100 Response
   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%
5. Number of Participants With Inactive Disease Status
   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.
6. Change From Baseline of Core Study CAIN457F2304 in JIA ACR Core Component - Physician Global Assessment of Disease Activity
   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.
7. Change From Baseline of Core Study CAIN457F2304 in JIA ACR Core Component - Parent's or Patients' Global Assessment of Overall Well-being
   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
8. Change From Baseline of Core Study CAIN457F2304 in JIA ACR Core Component - Functional Ability (CHAQ)
   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.
9. Change From Baseline of Core Study CAIN457F2304 in JIA ACR Core Component - Number of Joints With Active Arthritis
   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.
10. Change From Baseline of Core Study CAIN457F2304 in JIA ACR Core Component - Number of Joints With Limited Range of Motion
    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.
11. Change From Baseline of Core Study CAIN457F2304 in JIA ACR Core Component - CRP Levels
    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.
12. Change From Baseline of Core Study CAIN457F2304 of 27-joint Juvenile Arthritis Disease Activity Score (JADAS-27)
    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.
13. Change From Baseline of Core Study CAIN457F2304 of 71-joint Juvenile Arthritis Disease Activity Score (JADAS-71)
    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.
14. Change From Baseline of Core Study CAIN457F2304 in Total Enthesitis Count
    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
15. Change From Baseline of Core Study CAIN457F2304 in Total Dactylitis Count
    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
16. Serum Concentrations of Secukinumab Over Time
    Serum concentration of secukinumab over time. Blood samples for pharmacokinetics were taken pre-dose at the scheduled time points.
17. Number of Participants With Treatment-emergent Anti-Drug Antibodies (ADAs) of Secukinumab
    Number of participants with treatment-emergent Anti-Drug Antibodies (ADAs) of secukinumab. Blood samples were collected for immunogenicity (anti-AIN457 antibodies) assessments.