A Study to Evaluate the Efficacy and Safety of Bimekizumab in Adult Study Participants With Active Psoriatic Arthritis

Inclusion Criteria:

• Study participants must have a documented diagnosis of adult-onset PsA classified byand that meets the CASPAR classification criteria for at least 6 months prior toScreening with active PsA (despite previous csDMARD or apremilast therapy) and musthave at Baseline tender joint count (TJC) ≥3 out of 68 joints and swollen jointcount (SJC) ≥3 out of 66 joints (dactylitis of a digit counts as 1 joint each).

• Study participant must have at least 1 active psoriatic lesion(s) and/or adocumented history of chronic plaque-type psoriasis (PSO).

• Study participants may currently be on conventional synthetic disease-modifyingantirheumatic drug (csDMARD) therapy and must have previously been treated with atleast 1 csDMARD (methotrexate (MTX), leflunomide (LEF), sulfasalazine (SSZ)). Studyparticipants must have had an inadequate response to therapy or discontinued due tointolerance. (Inadequate response is determined by the Investigator and is definedas not achieving the minimal response after 12 weeks of therapy.)

• Study participants can either be biological disease-modifying antirheumatic drug (bDMARD)-naïve or have received not more than 1 prior tumor necrosis factor alpha (TNFα) inhibitor. Study participants who have been on a TNFα inhibitor previouslymust not have discontinued the TNFα inhibitor due to financial or health insurancereasons and must have either:

• experienced an inadequate response to previous treatment given at an approved dosefor at least 3 months, or

• been intolerant to administration (eg, had a side-effect/adverse event (AE) that ledto discontinuation).

Exclusion Criteria:

• Study participant has any medical or psychiatric condition that, in the opinion ofthe Investigator, could jeopardize or would compromise the study participant'sability to participate in this study.

• Female participants who are breastfeeding, pregnant, or plan to become pregnantduring the study.

• Participant has an active infection or a history of recent serious infections.

• Participant has known tuberculosis (TB) infection, is at high risk of acquiring TBinfection, or has current or history of nontuberculous mycobacterium (NTMB)infection.

• Study participant has a diagnosis of inflammatory conditions other than PSO or PsAincluding, but not limited to, rheumatoid arthritis, sarcoidosis, systemic lupuserythematosus, reactive arthritis, and axial spondyloarthritis.

• Study participants with a history of anterior uveitis are allowed if they have noactive symptoms at Screening or Baseline. Study participants with a diagnosis ofCrohn's disease or ulcerative colitis are allowed if they have no active symptomaticdisease at Screening or Baseline.

• Study participants with fibromyalgia or osteoarthritis symptoms that in theInvestigator's opinion would have potential to interfere with efficacy assessments.

• Participant has any active malignancy or history of malignancy within 5 years priorto the Screening Visit EXCEPT treated and considered cured cutaneous squamous orbasal cell carcinoma, or in situ cervical cancer.

• Participant has a history of chronic alcohol or drug abuse within 6 months prior toScreening.

• Study participants taking psoriatic arthritis (PsA) medications other than MTX, SSZ,apremilast, hydroxychloroquine (HCQ), LEF, nonsteroidal anti-inflammatory drug (NSAIDs)/ cyclooxygenase-2 (COX-2) inhibitors, oral corticosteroids, and analgesicsas outlined in the Inclusion criteria.

• Study participant is taking or has taken prohibited PsA or PSO medications withoutmeeting the mandatory wash-out period relative to the Baseline Visit.

• Study participant is taking or has taken janus kinase (JAK) inhibitor.

• Study participant is taking or has taken bDMARDs, including bimekizumab orrisankizumab, with the exception of having received 1 prior TNFα inhibitor.

• Study participant previously participated in another study of a medical device underinvestigation within the 4 weeks prior to the Screening Visit or is currentlyparticipating in another study of a medical device under investigation.