Patients considered to be treatment responders at week @ according to the American College of Rheumatology ( ACR ) Pediatric @ ( Pedi @ ) criteria for improvement in juvenile arthritis entered the second phase , a @-week randomized , double-blind , placebo-controlled withdrawal study , for an additional @ weeks , for evaluation of the primary end point , occurrence of a disease flare from week @ to week @ , based on the ACR preliminary definition of disease flare in juvenile arthritis .