A Study of Golimumab in Participants With Active Psoriatic Arthritis

The purpose of this study is to evaluate the efficacy of intravenously (administration of a fluid into the vein) administered golimumab 2 milligram per kilogram (mg/kg) in participants with active psoriatic arthritis (a chronic inflammatory arthritis that is associated with psoriasis).

This is a Phase 3, multicenter (when more than one hospital or medical school team work on a medical research study), randomized (study drug assigned by chance), double-blind (neither the researchers nor the participants know what treatment the participant is receiving), placebo-controlled (an inactive substance; a pretend treatment \[with no drug in it\] that is compared in a clinical trial with a drug to test if the drug has a real effect) study of golimumab compared with placebo in participants with active psoriatic arthritis. The study will include 4 phases: Screening phase (up to 6 weeks), Double-blind placebo-controlled phase (Week 0 to Week 24), Active treatment phase (Week 24 to Week 52), and Safety follow-up phase (8 weeks from last study drug administration). Total duration of the study will be 60 weeks per participant. Eligible Participants will be randomly assigned to either Treatment Group 1: Placebo or Treatment Group 2: Golimumab. Participants randomized to Placebo Group, will receive intravenous infusions of placebo at Weeks 0, 4, 12 and 20. At Week 24, all participants receiving placebo will begin receiving intravenous infusions of golimumab (2 mg/kg) at Week 24, 28 and thereafter every 8 weeks up to Week 52. Participants randomized to Golimumab Group, will receive intravenous infusions of golimumab 2 mg/kg at Week 0, 4 and thereafter every 8 weeks up to Week 52. At Week 24, participants randomized to golimumab Group will receive a placebo infusion to maintain the blind. The efficacy will be assessed primarily by measuring percentage of participants who achieve a 20 percent improvement from baseline in the assessment used in active psoriatic arthritis at Week 14. Participants' safety will be monitored throughout the study.

Eligibility Criteria:
Inclusion Criteria:

* Have had psoriatic arthritis (PsA) for at least 6 months prior to the first administration of study agent
* Have a diagnosis of active PSA as defined by 5 or more swollen joints and 5 or more tender joints at Screening and at Baseline and C-reactive protein \>=0.6 milligram per deciliter (mg/dL) at Screening
* Have active plaque psoriasis or a documented history of plaque psoriasis
* Have active PsA despite current or previous disease-modifying antirheumatic drugs (DMARD) and/or nonsteroidal anti-inflammatory drug (NSAID) therapy. DMARD therapy is defined as taking a DMARD for at least 3 months, or evidence of DMARD intolerance. NSAID therapy is defined as taking an NSAID for at least 4 weeks or evidence of NSAID intolerance

Exclusion Criteria:

* Have other inflammatory diseases that might confound the evaluations of benefit of Golimumab therapy, including but not limited to rheumatoid arthritis, ankylosing spondylitis, systemic lupus erythematosus, or Lyme disease
* Are pregnant, nursing, or planning a pregnancy or fathering a child while enrolled in the study or within 4 months after receiving the last administration of study agent
* Have used any biologic agents that are targeted for reducing tumor necrosis factors (TNF) alpha, including but not limited to Infliximab, Etanercept, Adalimumab, Golimumab, and Certolizumab Pegol
* Have ever used cytotoxic drugs, including Chlorambucil, Cyclophosphamide, Nitrogen mustard, or other Alkylating agents