A Study of Ustekinumab or Guselkumab in Pediatric Participants With Active Juvenile Psoriatic Arthritis

Steady-state trough serum concentration of ustekinumab at Week 28 by baseline age groups will be reported.

Steady-state trough serum concentration of guselkumab at Week 28 by baseline age groups will be reported.

AUCss is defined as area under the curve at steady-state over a 12-week dosing interval of ustekinumab at Week 28 by baseline age groups.

AUCss is defined as area under the curve at steady-state over a dosing interval (4 or 8 weeks) of guselkumab at Week 28 by baseline age groups.

Percentage of Participants with jPsA achieving ACR pediatric 30 response at Week 24 will be reported. The ACR pediatric 30 response criteria is defined as a 30 percent (%) improvement (that is, a decrease in score) from baseline in greater than or equal to (>=) 3 of the following 6 components, with worsening of >=30% in no more than 1 of the following components: physician global assessment (PGA) of disease activity, patient/participant assessment of overall well-being, number of active joints (defined as swelling or loss of motion with pain and/or tenderness), number of joints with limited range of motion, physician function by childhood health assessment questionnaire (CHAQ) and C-reactive protein (CRP).

Percentage of Participants with jPsA achieving ACR pediatric 30 response at Week 24 will be reported. The ACR pediatric 30 response criteria is defined as a 30% improvement (that is, a decrease in score) from baseline in >=3 of the following 6 components, with worsening of >=30% in no more than 1 of the following components: PGA of disease activity, patient/participant assessment of overall well-being, number of active joints (defined as swelling or loss of motion with pain and/or tenderness), number of joints with limited range of motion, physician function by CHAQ and CRP.

Steady-state trough serum concentration of ustekinumab at Week 52 by baseline age groups will be reported.

Steady-state trough serum concentration of guselkumab at Week 52 by baseline age groups will be reported.

AUCss is defined as area under the curve at steady-state over a 12-week dosing interval of ustekinumab at Week 52 by baseline age groups.

AUCss is defined as area under the curve at steady-state over a dosing interval (4 or 8 weeks) of guselkumab at Week 52 by baseline age groups.

The ACR pediatric 30 response criteria is defined as a 30% improvement (that is, a decrease in score) from baseline in >=3 of the following 6 components, with worsening of >=30% in no more than 1 of the following components: PGA of disease activity, patient/participant assessment of overall well-being, number of active joints (defined as swelling or loss of motion with pain and/or tenderness), number of joints with limited range of motion, physician function by CHAQ and CRP.

The ACR pediatric 50 and 70 responses are defined as a 50% improvement or 70% improvement (that is, a decrease in score) from baseline in >=3 of the following 6 components, with worsening of >=30% in no more than 1 of the following components: 1 of the following components: PGA of disease activity, patient/participant assessment of overall well-being, number of active joints (defined as swelling or loss of motion with pain and/or tenderness), number of joints with limited range of motion, physician function by CHAQ and CRP.

Time to response measured as time to achieving ACR pediatric 30 will be reported.

Change from baseline in cJADAS 10 at Weeks 4, 8, 12, 16, 24, and 52 will be reported. The cJADAS is calculated as the sum of the scores of its 3 components: (1) physician global rating of overall disease activity, measured on a 10-cm horizontal visual analog scale; (2) parent/child ratings of well-being, assessed on a 10 cm horizontal line VAS; (3) number of active joints, assessed in 10 joints, for a total score ranging from 0 to 30 where 0=no activity and 30=maximum activity.

Change from baseline in JADAS 10, 27 and 71 at Weeks 4, 8, 12, 16, 24, and 52 will be reported. The JADAS is calculated as the sum of the scores of its 4 components: (1) physician global rating of overall disease activity, measured on a 10-cm horizontal visual analog scale; (2) parent/child ratings of well-being, assessed on a 10 cm horizontal line VAS; (3) number of active joints, assessed in 71, 27, or 10 joints (for JADAS 71, JADAS 27, and JADAS 10, respectively); (4) CRP (truncated to 0-10 mg/dL).

Change from baseline in PASI score at Week 24 among the participants with greater than or equal to (>=) 3% body surface area (BSA) psoriatic involvement and a PGA psoriasis score of >=2 (mild) at baseline will be reported. The PASI includes assessments of 4 areas of the body: the head and neck, the arms, the trunk, and the legs. The percentage of skin in each area affected by psoriasis is given a numeric score representing the proportion involved. The severity of the 3 plaque signs of erythema, thickness/induration, and desquamation/scaling, is assessed on a 5-point scale. The total PASI score is from 0-72, where 0=no disease and 72=more disease.

An AE is any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the pharmaceutical/biological agent under study.

A SAE is any untoward medical occurrence that at any dose results in any of the following outcomes: death; initial or prolonged inpatient hospitalization; life-threatening experience (immediate risk of dying); persistent or significant disability/incapacity; congenital anomaly/birth defect; suspected transmission of any infectious agent via a medicinal product or medically important.

Percentage of participants with reasonably related AEs (including injection-site reactions and infections) will be reported.

Number of participants with antibodies to ustekinumab (including peak titers) will be reported.

Number of participants with antibodies to guselkumab (including peak titers) will be reported.