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 (DMARD)

Inclusion Criteria:

• Clinical diagnosis of PsA with symptom onset at least 6 months prior to theScreening 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 andBaseline Visits.

• Presence of either at Screening:

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

2. high-sensitivity C-reactive protein (hs-CRP) > laboratory defined upper limitof 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 weekduration of therapy) to previous or current treatment with at least 1 non-biologicDMARD at maximally tolerated dose (methotrexate (MTX), sulfasalazine (SSZ),leflunomide (LEF), cyclosporine, apremilast, bucillamin or iguratimod), orparticipant has an intolerance to or contraindication for DMARDs as defined by theinvestigator.

• Participant who is on current treatment with concomitant non-biologic DMARDs atstudy entry must be on <= 2 non-biologic DMARDs (except the combination of MTX andleflunomide). The following non-biologic DMARDs are allowed: MTX, sulfasalazine,leflunomide, apremilast, hydroxychloroquine (HCQ) , bucillamine or iguratimod, andhave been ongoing for >= 12 weeks and at stable dose for >= 4 weeks prior to theBaseline Visit. No other DMARDs are permitted during the study. i. Participants who need to discontinue DMARDs prior to the Baseline Visit to complywith this inclusion criterion must follow the procedure specified below or at leastfive times the mean terminal elimination half-life of a drug:

1. >= 8 weeks for LEF if no elimination procedure was followed, or adhere to anelimination procedure (i.e., 11 days with cholestyramine, or 30 days washoutwith 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 toruxolitinib, tofacitinib, baricitinib, and filgotinib).

• Current treatment with > 2 non-biologic DMARDs; or use of DMARDs other thanmethotrexate, 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 currentdiagnosis of inflammatory joint disease other than PsA (including, but not limitedto rheumatoid arthritis, gout, overlap connective tissue diseases, scleroderma,polymyositis, dermatomyositis, systemic lupus erythematosus). Prior history ofreactive arthritis or axial spondyloarthritis including ankylosing spondylitis andnonradiographic axial spondyloarthritis is permitted if documentation of change indiagnosis to PsA or additional diagnosis of PsA is made. Prior history offibromyalgia is permitted if documentation of change in diagnosis to PsA ordocumentation that the diagnosis of fibromyalgia was made incorrectly.