A Study Comparing Upadacitinib (ABT-494) to Placebo and to Adalimumab in Participants With Psoriatic Arthritis Who Have an Inadequate Response to at Least One Non-Biologic Disease Modifying Anti-Rheumatic Drug

Inclusion Criteria:

- Clinical diagnosis of PsA with symptom onset at least 6 months prior to the Screening
Visit and fulfillment of the Classification Criteria for PsA (CASPAR) criteria.

- Participant has active disease at Baseline defined as >= 3 tender joints (based on 68
joint counts) and >= 3 swollen joints (based on 66 joint counts) at Screening and
Baseline Visits.

- Presence of either at Screening:

1. >= 1 erosion on x-ray as determined by central imaging review or;

2. hs-CRP > laboratory defined upper limit of normal (ULN).

- Diagnosis of active plaque psoriasis or documented history of plaque psoriasis.

- Participant has had an inadequate response (lack of efficacy after a minimum 12 week
duration of therapy) to previous or current treatment with at least 1 non-biologic
DMARD at maximally tolerated dose (MTX, SSZ, LEF, apremilast, bucillamin, cyclosporine
or iguratimod), or participant has an intolerance to or contraindication for DMARDs as
defined by the investigator.

- Participant who is on current treatment with concomitant non-biologic DMARDs at study
entry must be on <= 2 non-biologic DMARDs (except the combination of MTX and
leflunomide). The following non-biologic DMARDs are allowed: MTX, sulfasalazine,
leflunomide, apremilast, HCQ , bucillamine or iguratimod, and have been ongoing for >=
12 weeks and at stable dose for >= 4 weeks prior to the Baseline Visit. No other
DMARDs are permitted during the study.

i. Participants who need to discontinue DMARDs prior to the Baseline Visit to comply
with this inclusion criterion must follow the procedure specified below or at least
five times the mean terminal elimination half-life of a drug:

1. >= 8 weeks for LEF if no elimination procedure was followed, or adhere to an
elimination procedure (i.e., 11 days with cholestyramine, or 30 days washout with
activated charcoal or as per local label);

2. >= 4 weeks for all others.

Exclusion Criteria:

- Prior exposure to any Janus Kinase (JAK) inhibitor (including but not limited to
ruxolitinib, tofacitinib, baricitinib, and filgotinib).

- Current treatment with > 2 non-biologic DMARDs; or use of DMARDs other than
methotrexate, sulfasalazine, leflunomide, apremilast, hydroxychloroquine, bucillamine,
or iguratimod; or use of methotrexate in combination with leflunomide.

- History of fibromyalgia, any arthritis with onset prior to age 17 years, or current
diagnosis of inflammatory joint disease other than PsA (including, but not limited to
rheumatoid arthritis, gout, overlap connective tissue diseases, scleroderma,
polymyositis, dermatomyositis, systemic lupus erythematosus). Prior history of
reactive arthritis or axial spondyloarthritis including ankylosing spondylitis and
nonradiographic axial spondyloarthritis is permitted if documentation of change in
diagnosis to PsA or additional diagnosis of PsA is made. Prior history of fibromyalgia
is permitted if documentation of change in diagnosis to PsA or documentation that the
diagnosis of fibromyalgia was made incorrectly.