This study is a pilot, ascending dose, multi-center, randomized, double blind, placebo controlled, pediatric study conducted in three phases.

Inclusion Criteria include, but are not limited to, the following:

• Patients aged 4 to less than 21 years who meet the criteria for active SJIA
• Must have been on a stable dose of non-steroidal anti-inflammatory drugs (NSAIDs) for at least 4 weeks prior to the screening visit

Exclusion Criteria include, but are not limited to, the following:

• Use of certain medications prior to the baseline visit
• History of recurrent infections