This is a study of guselkumab in participants with active Psoriatic Arthritis (PsA) who had inadequate response to standard therapies. It will evaluate the clinical efficacy of guselkumab in the reduction of signs and symptoms and the safety profile of guselkumab in the treatment of PsA. The study will consists of 4 phases: a screening phase of up to 6 weeks, a blinded treatment phase of approximately 1 year (that is, 52 weeks), including a placebo controlled period from Week 0 to Week 24 and double-blind active treatment period from Week 24 to Week 52, and a safety follow-up phase of 8 weeks after Week 52 (Week 52 to 60) and will be 12 weeks from the last administration of study agent (at Week 48) to the final safety follow-up visit. Efficacy, safety, pharmacokinetic, immunogenicity, and biomarker evaluations will be performed in the study at defined schedule.
