A Study to Evaluate the Effect of Bimekizumab on Gene Expression Biomarkers in Study Participants With Moderate to Severe Plaque Psoriasis

The purpose of this study is to evaluate the effect of bimekizumab on gene expression biomarkers at Week 48 in a subset of study participants with moderate to severe plaque psoriasis (PSO) and moderate to severe plaque PSO with concomitant active psoriatic arthritis (PsA) who have provided skin biopsies for reverse transcription-polymerase chain reaction (RT-PCR).

Inclusion Criteria: Cohort A and Cohort B * Study participant must be at least 18 years of age inclusive at the time of signing the Informed Consent Form (ICF) * Study participant must have: 1. Cohort A and Cohort B: Plaque psoriasis (PSO) diagnosed for at least 6 months prior to the Screening Visit 2. Cohort B only: In addition to the criteria specified above, study participant has a documented diagnosis of adult-onset psoriatic arthritis (PsA) and meets the CASPAR classification criteria for at least 6 months prior to Screening for active PsA and must have ≥1 tender joint count (TJC) out of 68 and ≥1 swollen joint count (SJC) out of 66 at Screening or up to 3 months before Screening (documented evidence) * Study participant must have Psoriasis Area and Severity Index (PASI) score ≥12 and body surface area (BSA) affected by PSO ≥10% and Investigator's Global Assessment (IGA) score ≥3 on a 5 point scale * Study participant must be a candidate for systemic PSO therapy and/or phototherapy * Study participant agrees not to change their usual sun exposure during the course of the study and to use ultraviolet A/ultraviolet B sunscreens if unavoidable exposure occurs * Study participant has body weight \