• Participants must be ≥18 years of age .

• Participants have a confirmed diagnosis of psoriatic arthritis (PsA) per the 2006 Classification for Psoriatic Arthritis (CASPAR) criteria with symptoms for ≥6 months before the Screening Visit.

• Participants have moderate to severe active disease (defined by a 68 tender joint count \[TJC68\] of ≥3 and a 66 swollen joint count \[SJC66\] of ≥3).

• Participants have current active plaque psoriasis (PsO) or a dermatologist-confirmed history of plaque PsO.

• Participants test negative for both rheumatoid factor and anti-cyclic citrullinated peptide at the Screening Visit.

• Participants must have received 1 or 2 TNFα inhibitors for PsA or PsO and must have experienced an inadequate response to treatment with the TNFα inhibitor(s) given at an approved dose for ≥3 months or have stopped treatment due to safety/tolerability problems after ≥1 administration of a TNFα inhibitor.