This is a randomized withdrawal, double blind, placebo controlled study of pediatric subjects (2 to <18 years of age) with JIA. The primary objective is to compare the efficacy of tofacitinib versus placebo for the treatment of signs and symptoms of JIA at Week 26 of the double blind phase as measured by the percentage of subjects with disease flare (according to PRCSG/PRINTO Disease Flare criteria) after Week 18 of the open label run in phase.All eligible subjects enrolled in the study will initially receive open label tofacitinib for 18 weeks (run in phase). At the end of the 18 week run in phase, only subjects who achieve at least a JIA ACR 30 response will be randomized to the 26 week double blind, placebo controlled phase. Subjects who do not achieve a JIA ACR 30 response at this time point will be discontinued from the study. In addition, subjects who experience a single episode of disease flare at any time during the study (including the open label run in and double blind phase) will also be discontinued from the study. All subjects participating in this study, including those discontinued from the study, will have the option, if eligible (based on inclusion and exclusion criteria), of enrolling in the tofacitinib JIA long term extension study (A3921145).~Subjects who are eligible for the 26 week double blind phase will be randomized (1:1 ratio) to either active tofacitinib or placebo. For subjects with polyarticular course JIA (ie, extended oligoarthritis, polyarthritis RF+, polyarthritis RF , systemic JIA with active arthritis but without active systemic features), randomization will be stratified by JIA category and baseline CRP (normal, above normal). For subjects with psoriatic and enthesitis related arthritis, randomization will be stratified by JIA category.~Approximately 210 subjects will be enrolled in the open label run in phase. Among subjects with polyarticular course JIA, stratification will target at least 50% with a baseline CRP above the upper limit of normal. The first cohort (ie, polyarticular course JIA) will have at least 170 subjects enrolled in the run in phase with the minimum number of JIA categories as follows: 24 with extended oligoarthritis, 20 with polyarthritis RF+, 62 with polyarthritis RF-, and no minimum for subjects with systemic JIA with active arthritis but without active systemic features. Additional cohorts (ie, psoriatic and enthesitis related arthritis) will include a minimum of 20 subjects with psoriatic arthritis, and 20 subjects with enthesitis related arthritis. The overall target minimum number of subjects to be enrolled in the study by age is as follows: 20 subjects 2 to <6 years, 20 subjects 6 to <12 years, and 20 subjects 12 to <18 years. The duration of subject participation among those who complete the study (without discontinuation) is expected to be approximately 44 weeks.
Evaluate efficacy, safety and tolerability of tofacitinib in pediatric JIA patients.