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

This study is a randomized (patients are assigned different treatments based on chance),
double-blind (neither the patient nor the physician knows whether drug or placebo is being
taken, or at what dosage), parallel-group, multicenter study to evaluate the effectiveness
and safety of ustekinumab compared to placebo in the treatment of patients with active
psoriatic arthritis. The primary effectiveness endpoint will be measured by the reduction in
signs and symptoms of arthritis, as defined by 20% improvement from baseline in American
College of Rheumatology (ACR) measurements of arthritis at Week 24. The study will
additionally look at higher levels of joint improvement (ie, 50% or 70% improvement from
baseline) and improvement in activity and quality of life, as well as the impact of
ustekinumab on psoriatic skin lesions. Safety assessments will be performed throughout the
study and include obtaining and evaluating laboratory tests, vital signs (eg, blood
pressure) and the occurrence and severity of adverse events (side effects). Patients will be
assigned to one of three treatment groups. Patients will receive either 45 mg ustekinumab,
90 mg ustekinumab or placebo at Weeks 0, 4, and every 12 weeks until Week 88. Patients who
do not have >=5% improvement in their disease (tender and swollen joints) at Week 16 may be
eligible to receive an increase or change to their ustekinumab dosage. Ustekinumab 45 mg, 90
mg, or placebo subcutaneous injections at Weeks 0 and 4 followed by every-12-week dosing
with the last dose at Week 88. Early escape possibility at Week 16. Patients randomized to
placebo will crossover to receive ustekinumab at Weeks 24 and 28 followed by every-12-week
dosing with the last dose at Week 88. Expected duration of exposure to study agent is 100
weeks.