A Study of the Safety and Effectiveness of Ustekinumab in Patients With Psoriatic Arthritis

This is a randomized (participants are assigned different treatments based on chance), double-blind (neither the participant nor the physician knows whether drug or placebo is being taken, or at what dosage), parallel-group (each group of participants will be treated at the same time), and multicenter (study conducted at multiple sites) study. Approximately, 615 participants will participate in this study. Participants will be assigned to one of three treatment groups: Group I: ustekinumab 45 mg, Group II: ustekinumab 90 mg, and Group III: placebo group (an inactive substance). Participants will receive either 45 mg ustekinumab or 90 mg ustekinumab at Weeks 0, 4, and every 12 weeks until Week 88 as randomized to respective groups. Participants in placebo group will receive placebo at Weeks 0, 4, 16, and 20 and 45 mg ustekinumab at Weeks 24 and 28 followed by every 12 weeks dosing until Week 88. Participants who do not have greater than or equal to 5 percentage improvement in their disease (tender and swollen joints) will be eligible for an early escape. Specifically, during early escape at Week 16, participants in Group I will receive 90 mg ustekinumab, for participants in Group II same dosing schedule will be continued, and participants in placebo group will receive 45 mg ustekinumab. Safety evaluations will include assessments of adverse events, clinical laboratory tests, and physical examination. The maximum study duration will be approximately 108 weeks.