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

Inclusion Criteria:

Have had a documented diagnosis of psoriatic arthritis (PsA) at least 6 months
Have a diagnosis of active PsA at the time of entry into the study
If the participant is using methotrexate they should have started treatment at a dose not to exceed 25 milligram per week at least 3 months prior to the beginning of the study and should have no serious toxic side effects attributable to methotrexate. Methotrexate route of administration and doses should be stable for at least 4 weeks prior to the first administration of study agent. If currently not using methotrexate, must have not received methotrexate for at least 4 weeks prior to the first administration of the study agent

Exclusion Criteria:

Have other inflammatory diseases, including but not limited to rheumatoid arthritis, ankylosing spondylitis, systemic lupus erythematosus, or Lyme disease
Have used any therapeutic agent targeted at reducing interleukin (IL)-12 or IL-23, including but not limited to ustekinumab and briakinumab (ABT-874)
Have used any biologic agents that are targeted for reducing tumor necrosis factor-alpha, including but not limited to infliximab, etanercept, adalimumab, and golimumab
Have a medical history of latent or active granulomatous infection
Have any known malignancy or have a history of malignancy (with the exception of basal cell carcinoma, squamous cell carcinoma in situ of the skin, or cervical carcinoma in situ that has been treated with no evidence of recurrence, or squamous cell carcinoma of the skin that has been treated with no evidence of recurrence within 5 years of the beginning of the study