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

Eligibility Criteria

• * 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 \<120 kg
• * A female study participant is eligible to participate if they are not pregnant, not breastfeeding, and at least 1 of the following conditions applies:
• * Study participant must be ≥18 years of age at the time of signing the informed consent
• * Study participants who are overtly healthy as determined by medical evaluation including medical history, physical examination, and vital signs
• * Study participant has body weight \<120 kg
• * Female study participant is eligible to participate if they are not pregnant and not breastfeeding
• * Study participant has a form of PSO other than plaque type (eg, pustular, erythrodermic and guttate PSO, or drug induced PSO)
• * Study participant has an active infection or history of infection(s) as follows:
• 1. Any active systemic infection within 14 days prior to Baseline
• 2. A serious infection, defined as requiring hospitalization or intravenous anti-infective(s) within 2 months prior to the Baseline Visit
• 3. A history of opportunistic, recurrent, or chronic infections that, in the opinion of the investigator, might cause this study to be detrimental to the study participant
• * At investigator's discretion, study participant with chronic (medically controlled) viral hepatitis B or C or human immunodeficiency virus (HIV) infection, or history of hepatitis B.
• * Study participant has any of the following:
• 1. Known active tuberculosis (TB) disease.
• 2. History of active TB involving any organ system unless adequately treated
• 3. High risk of acquiring TB infection
• * Study participant has a verified diagnosis of inflammatory conditions other than PSO or PsA, including but not limited to rheumatoid arthritis (RA), sarcoidosis, inflammatory bowel diseases (IBD), or systemic lupus erythematosus. Note: Study participants with a diagnosis of IBD are allowed if they have no active symptomatic disease at Screening or Baseline
• * Study participant 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
• * Study participant has any medical or psychiatric condition that, in the opinion of the investigator, could jeopardize or would compromise the study participant's ability to participate in this study
• * Study participant has a known hypersensitivity to any components of the IMP as stated in this protocol
• * Study participant has a history of primary failure to any biologic (ie, no response within the first 12 weeks of treatment)
• * Study participant has laboratory abnormalities at Screening
• * Study participant has a current history of alcohol or drug use disorder, as defined in Diagnostic and Statistical Manual of Mental Disorders (DSM) V, within the previous 6 months prior to Screening, as evaluated by the investigator based on medical history, and/or site interview