A Study Evaluating the Efficacy and Safety of Guselkumab Administered Subcutaneously in Participants With Active Psoriatic Arthritis Including Those Previously Treated With Biologic Anti -Tumor Necrosis Factor (TNF) Alpha Agent(s)

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.

Inclusion Criteria:

- Have a diagnosis of Psoriatic Arthritis (PsA) for at least 6 months before the first
administration of study agent and meet Classification criteria for Psoriatic Arthritis
(CASPAR) at screening

- Have active PsA as defined by: at least 3 swollen joints and at least 3 tender joints
at screening and at baseline; and C-reactive protein (CRP) greater than or equal to
(>=) 0.3 milligram per deciLitre (mg/dL) at screening from the central laboratory

- Have at least 1 of the PsA subsets: distal interphalangeal joint involvement,
polyarticular arthritis with absence of rheumatoid nodules, arthritis mutilans,
asymmetric peripheral arthritis, or spondylitis with peripheral arthritis

- Have active plaque psoriasis, with at least one psoriatic plaque of >= 2 centimeter
(cm) diameter or nail changes consistent with psoriasis or documented history of
plaque psoriasis

- Have active PsA despite previous non-biologic disease-modifying antirheumatic drugs
(DMARD), apremilast, and/or nonsteroidal anti-inflammatory drug (NSAID) therapy :
Non-biologic DMARD therapy is defined as taking a non-biologic DMARD for at least 3
months or evidence of intolerance; Apremilast therapy is defined as taking apremilast
at the marketed dose approved in the country where the study is being conducted for at
least 4 months or evidence of intolerance; NSAID therapy is defined as taking an NSAID
for at least 4 weeks or evidence of intolerance

- Participants may have been previously treated with up to 2 anti-TNF (tumor necrosis
factor) alpha agents (approximately 30 percent [%] of the overall study population),
and must document the reason for discontinuation

Exclusion Criteria:

- Has other inflammatory diseases that might confound the evaluations of benefit of
guselkumab therapy, including but not limited to rheumatoid arthritis (RA), axial
spondyloarthritis (this does not include a primary diagnosis of PsA with spondylitis),
systemic lupus erythematosus, or Lyme disease

- Has ever received more than 2 anti-TNFalpha agents

- Has previously received any biologic treatment (other than anti-TNF alpha agents),
including, but not limited to ustekinumab, abatacept, secukinumab, tildrakizumab,
ixekizumab, brodalumab, risankizumab, or other investigative biologic treatment

- Has previously received any systemic immunosuppressants (for example, azathioprine,
cyclosporine, 6 thioguanine, mercaptopurine, mycophenolate mofetil, hydroxyurea,
tacrolimus) within 4 weeks of the first administration of study agent

- Has received apremilast within 4 weeks prior to the first administration of study
agent

- Has previously received tofacitinib, baricitinib, filgotinib, peficitinib (ASP015K),
decernotinib (VX‑509), or any other Janus kinase (JAK) inhibitor