A Study to Test the Efficacy and Safety of Bimekizumab in the Treatment of Subjects With Active Psoriatic Arthritis

Inclusion Criteria:

An Institutional Review Board (IRB)/Independent Ethics Committee (IEC) approved written Informed Consent form is signed and dated by the subject
Subject is male or female at least 18 years of age
Female subject must be postmenopausal, permanently sterilized or willing to use a highly effective method of contraception
Documented diagnosis of adult-onset Psoriatic Arthritis (PsA) meeting the Classification Criteria for Psoriatic Arthritis (CASPAR) for at least 6 months prior to Screening with active PsA and must have at Baseline tender joint count (TJC) >=3 out of 68 and swollen joint count (SJC) >=3 out of 66
Subject must be negative for rheumatoid factor and anti-cyclic citrullinated peptide (CCP) antibodies
Subject must have at least 1 active psoriatic lesion(s) and/or a documented history of psoriasis (PSO)
Subject must be a suitable candidate for treatment with adalimumab and has no contraindications to receive adalimumab as per the local label as assessed by the Investigator
Subjects currently taking NSAIDs, cyclooxygenase 2 (COX-2) inhibitors, analgesics (including mild opioids), corticosteroids, methotrexate (MTX), leflunomide (LEF), sulfasalazine (SSZ), hydroxychloroquine (HCQ) AND/OR apremilast can be allowed if they fulfill specific requirements prior to study entry

Exclusion Criteria:

Female subjects who are breastfeeding, pregnant, or plan to become pregnant during the study
Subjects with current or prior exposure to any biologics for the treatment of Psoriatic Arthritis (PsA) or Psoriasis (PSO)
Subject has an active infection or a history of recent serious infections
Subject has known tuberculosis (TB) infection, is at high risk of acquiring TB infection, or has current or history of nontuberculous mycobacterium (NTMB) infection
Subject has a diagnosis of inflammatory conditions other than PSO or PsA. Subjects with a diagnosis of Crohn's disease, ulcerative colitis, or other inflammatory bowel disease (IBD) are allowed as long as they have no active symptomatic disease at Screening or Baseline
Subject had acute anterior uveitis within 6 weeks of Baseline
Subject has any active malignancy or history of malignancy within 5 years prior to the Screening Visit EXCEPT treated and considered cured cutaneous squamous or basal cell carcinoma, or in situ cervical cancer
Subject has a form of PSO other than chronic plaque-type (eg, pustular, erythrodermic and guttate PSO, or drug-induced PSO)
Presence of active suicidal ideation, or moderately severe major depression or severe major depression
Subject has a history of chronic alcohol or drug abuse within 6 months prior to Screening