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

Percentage of Participants With a PASI90 Response at Week 16 in the Subgroup of Participants With PSO Involving at Least 3% BSA at Baseline

The PASI90 response assessments are based on at least 90% improvement in PASI score from Baseline. Body divided into 4 areas: head, arms, trunk to groin, and legs to top of buttocks. Assignment of an average score for redness, thickness, and scaling for each of the 4 body areas with a score of 0 (clear) to 4 (very marked). Determining the percentage of skin covered with PSO for each of the body areas and converting to a 0 to 6 scale. Final PASI = average redness, thickness, and scaliness of the psoriatic skin lesions, multiplied by the involved psoriasis area score of respective section, and weighted by the percentage of the person's affected skin for respective section. The minimum possible PASI score is 0 = no disease, the maximum score is 72 = maximal disease.

Time frame: Baseline, Week 16

Change From Baseline in the Short Form 36-item Health Survey (SF-36) Physical Component Summary (PCS) at Week 16 for Placebo and BKZ

SF-36 (version 2, standard recall):36-item generic health-related Quality of Life instrument that uses recall period of 4 weeks. Questionnaire has 36 questions composing scale that represent 8 domains:physical functioning; role physical; bodily pain;general health;vitality; social functioning;role emotional; and mental health. Scores for 8 domains were combined into two summary scores: physical component summary (PCS) score and mental component summary (MCS) score. Scores for 2 components summary (PCS and MCS) and 8 domains have been calculated and computed as raw/observed score to norm-based T-score metric(mean=50, standard deviation=10), raw score min=0(worst), max=100(best). Individual respondent's score falls outside T-score range of 45 to 55 was considered outside average range and when considering group-level data, score below 47 was considered indicative of impaired functioning within that health domain or dimension. Positive value in change from Baseline indicated improvement.

Time frame: Baseline, Week 16

Percentage of Participants With a Minimal Disease Activity (MDA) at Week 16

MDA is measure to indicate disease remission, and is based on composite score of 7 domains. Participant is considered having achieved MDA if participant fulfills at least 5 of following 7 criteria: Tender joint count (0-68 joints) less than or equal to (≤1); Swollen joint count (0-66 joints) ≤ 1; PASI ≤ 1 or BSA ≤ 3: In PASI, body divided into four parts, head and neck, upper limb, trunk and lower limbs. Each area assessed for erythema, induration and scaling, each rated on a scale of 0 to 4. Total score ranges from 0(no disease) to 72 (maximal disease)\]; Patient's Assessment of Arthritis Pain ≤ 15 \[using VAS on a scale of 0 (no pain) to 100 (severe pain)\]; Patient's Global Assessment of Disease Activity ≤ 20 \[using VAS on a scale of 0 (very well) to 100 (very poor)\]; HAQ-DI score ≤ 0.5, HAQ-DI score ranges from 0 (no difficulty) to 3 (maximum difficulty); Leeds Enthesitis Index score ≤ 1 for participants with enthesitis at baseline.

Time frame: Week 16

Change From Baseline in Van Der Heijde Modified Total Sharp Score (vdHmTSS) in Participants With Elevated Hs-CRP and/or at Least 1 Bone Erosion at Baseline at Week 16 for Placebo and BKZ

The degree of joint damage was assessed using the vdHmTSS by quantifying the extent of bone erosions and joint space narrowing for 64 and 52 joints, respectively. The vdHmTSS ranges from 0 to 528, with higher scores representing greater damage. Descriptive statistics for ADA 40 mg reference arm was not calculated and reported since reference based imputation analysis method is used with Placebo as reference. As pre-specified in the SAP, this analysis was performed only for the participants randomized to Placebo and BKZ.

Time frame: Baseline, Week 16

Percentage of Participants With an Enthesitis-free State in the Leeds Enthesitis Index (LEI) at Week 16 in the Subgroup of Participants With Enthesitis at Baseline in the Pooled Population of PA0010 and PA0011

Presence of enthesitis was assessed in the subgroup of participants with enthesitis by palpation on the lateral epicondyles of the humerus (elbows), medial femoral epicondyles (knees), and Achilles tendons (heels) bilaterally and scored as 0 (no tenderness) and 1 (tenderness) at Baseline. The LEI consists of 6 items, 3 for the right part and 3 for the left part of the body. LEI is derived as the sum of the enthesitis score over the 6 sites mentioned above. The total score ranges from 0 to 6, higher scores indicates greater degree of enthesitis. Descriptive/Inferential statistics for ADA 40 mg reference arm was not calculated and reported since pooled data with PA0011 study is used which did not have ADA 40 mg arm.

Time frame: Baseline of PA0010 for Participants of PA0010 and Baseline of PA0011 for Participants of PA0011, Week 16

Percentage of Participants With a Dactylitis-free State Based on the Leeds Dactylitis Index (LDI) at Week 16 in the Subgroup of Participants With Dactylitis at Baseline in the Pooled Population of PA0010 and PA0011

The LDI quantitatively measures dactylitis using the circumference of involved digits and control digits and tenderness of involved digits. Digits affected by dactylitis are defined as those with a 10% difference in the ratio of circumference of the affected digit to the contralateral digit. The control digit is either the contralateral digit (digit on opposite hand or foot). The ratio of circumference between an affected digit and the control digit is multiplied by the tenderness score for the affected digit. The results from each involved digit are summed to provide the final LDI score. A higher LDI indicates worse dactylitis. Tenderness score (0 = no tenderness, 1 = tender). Descriptive/Inferential statistics for ADA 40 mg reference arm was not calculated and reported since pooled data with PA0011 study was used which did not have ADA 40 mg arm.

Time frame: Baseline of PA0010 for Participants of PA0010 and Baseline of PA0011 for Participants of PA0011, Week 16

Percentage of Participants With an American College of Rheumatology (ACR) 20 Response at Week 16

The ACR20 response rate was based on a 20% or greater improvement of arthritis relative to Baseline. Participants who met the following 3 conditions for improvement from Baseline were classified as meeting the ACR20 response criteria: 1. ≥ 20% improvement in 68-tender joint count; 2. ≥ 20% improvement in 66-swollen joint count; and 3. ≥ 20% improvement in at least 3 of the 5 following parameters: Physician global assessment of disease activity (100 mm VAS \[0 = no symptoms; 100 = severe symptoms\]), Patient global assessment of disease activity (100 mm VAS \[0 = no limitation of normal activities; 100 = very poor\]), Patient assessment of pain (100 mm VAS \[0 = no pain; 100 = most severe pain\]), HAQ-DI assessed degree of difficulty experienced in 8 domains of daily living activities (20 questions), its score (0-3) computed from item scores, lower scores indicated less disability, hsCRP.

Time frame: Week 16

Change From Baseline in Van Der Heijde Modified Total Sharp Score (vdHmTSS) in the Overall Population at Week 16 for Placebo and BKZ

The degree of joint damage was assessed using the vdHmTSS by quantifying the extent of bone erosions and joint space narrowing for 64 and 52 joints, respectively. The vdHmTSS ranges from 0 to 448, with higher scores representing greater damage. Descriptive statistics for ADA 40 mg reference arm was not calculated and reported since reference based imputation analysis method was used with Placebo as reference.

Time frame: Baseline, Week 16

Percentage of Participants With an American College of Rheumatology (ACR) 70 Response at Week 16

The ACR70 response rate was based on a 70% or greater improvement of arthritis relative to Baseline. Participants who met the following 3 conditions for improvement from Baseline were classified as meeting the ACR70 response criteria: 1. ≥ 70% improvement in 68-tender joint count; 2. ≥ 70% improvement in 66-swollen joint count; and 3. ≥ 70% improvement in at least 3 of the 5 following parameters: Physician global assessment of disease activity (100 mm VAS \[0 = no symptoms;100 = severe symptoms\]), Patient global assessment of disease activity (100 mm VAS \[0 = no limitation of normal activities;100 = very poor\]), Patient assessment of pain (100 mm VAS \[0 = no pain; 100 = most severe pain\]), HAQ-DI assessed degree of difficulty experienced in 8 domains of daily living activities (20 questions), its score (0-3) computed from item scores, lower scores indicated less disability, hsCRP.

Time frame: Week 16

Percentage of Participants With Investigator Global Assessment (IGA) Response Defined as Score of 0 (Clear) or 1 (Almost Clear) AND at Least a 2-grade Reduction From Baseline at Week 4 in the Subset of Participants With Psoriatic Skin Lesions at Baseline

IGA measured the overall severity of PSO using the following 5-point scale and score was rated as 0 = clear (No signs of PSO; post-inflammatory hyperpigmentation may be present), 1 = almost clear (No thickening; normal to pink coloration; no to minimal focal scaling), 2 = mild (Just detectable to mild thickening; pink to light red coloration; predominately fine scaling), 3 = moderate (Clearly distinguishable to moderate thickening; dull to bright red, moderate scaling), and 4 = severe (Severe thickening with hard edges; bright to deep dark red coloration; severe/coarse scaling covering almost all or all lesions). The IGA response is defined as score of 0 (clear) or 1 (almost clear) with at least a 2-category improvement relative to Baseline.

Time frame: Baseline, Week 4

Percentage of Participants With an IGA Response Defined as Score of 0 (Clear) or 1 (Almost Clear) AND at Least a 2-grade Reduction From Baseline at Week 16 in the Subset of Participants With Psoriatic Skin Lesions at Baseline

IGA measured the overall severity of PSO using the following 5-point scale and score was rated as 0 = clear (No signs of PSO; post-inflammatory hyperpigmentation may be present), 1 = almost clear (No thickening; normal to pink coloration; no to minimal focal scaling), 2 = mild (Just detectable to mild thickening; pink to light red coloration; predominately fine scaling), 3 = moderate (Clearly distinguishable to moderate thickening; dull to bright red, moderate scaling), and 4 = severe (Severe thickening with hard edges; bright to deep dark red coloration; severe/coarse scaling covering almost all or all lesions). The IGA response is defined as score of 0 (clear) or 1 (almost clear) with at least a 2-category improvement relative to Baseline.

Time frame: Baseline, Week 16

Change From Baseline in the Patient's Assessment of Arthritis Pain (PtAAP) at Week 16

The PtAAP VAS is part of the American College of Rheumatology core set of measures in arthritis. Participants assessed their arthritis pain using a VAS ranging from 0 (no pain) to 100 (most severe pain). A negative change from baseline indicates improvement.

Time frame: Baseline, Week 16

Percentage of Participants With an Enthesitis-free State Based on the Spondyloarthritis Research Consortium of Canada (SPARCC) Index at Week 16 in the Subgroup of Participants With Enthesitis at Baseline

Presence of enthesitis was assessed in the subgroup of participants with enthesitis at Baseline. The SPARCC index measures the severity of enthesitis through the assessment of 16 sites, 8 for the right part and 8 for the left part of the body: the greater trochanter (right/left), quadriceps tendon insertion into the patella (right/left), patellar ligament insertion into the patella and tibial tuberosity (right/left), achilles tendon insertion (right/left), plantar fascia insertion (right/left), medial and lateral epicondyles (right/left), and the supraspinatus insertion (right/left). Tenderness on examination is recorded as either present (1) or absent (0) for each of the 16 sites, for an average range of 0 (no enthesitis) to 16 (severe enthesitis).

Time frame: Baseline, Week 16

Change From Baseline in Psoriatic Arthritis Impact of Disease-12 (PsAID-12) Total Score at Week 16

The PsAID-12 is a patient-reported outcome measure for assessing the impact of Psoriatic Arthritis (PsA) in 12 physical and psychological domains, including pain, fatigue, skin problems, work and/or leisure activities, functional capacity, discomfort, sleep disturbance, coping, anxiety/fear/uncertainty, embarrassment and/or shame, social participation, and depression. Each domain is assessed with a single question using a 0 to 10 numerical rating scale. Each domain score was multiplied by a weighting factor and the results were then summed to provide the total score. The total score ranged from 0 to 10, with higher scores indicating a worse status. A negative change from baseline indicates improvement.

Time frame: Baseline, Week 16

Percentage of Participants With Treatment-emergent Adverse Events (TEAEs) During the Study

An Adverse Event (AE) is any untoward medical occurrence in a patient or clinical investigation participants administered a pharmaceutical product, which does not necessarily have a causal relationship with this treatment. An AE could therefore be any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease temporally associated with the use of a medicinal (investigational) product, whether or not related to the medicinal (investigational) product. TEAEs were defined as any AEs with an onset date on or after the date of first IMP administration and within 140 days after the final dose of IMP.

Time frame: From Baseline until Safety Follow-Up (up to Week 72)

Percentage of Participants With Treatment-emergent Serious Adverse Events (SAEs) During the Study

A SAE is any untoward medical occurrence that at any dose: Results in death, is life-threatening, requires in patient hospitalization or prolongation of existing hospitalization; is a congenital anomaly or birth defect; is an infection that requires treatment parenteral antibiotics, other important medical events which based on medical or scientific judgement may jeopardize the patients, or may require medical or surgical intervention to prevent any of the above. TEAEs were defined as any AEs with an onset date on or after the date of first IMP administration and within 140 days after the final dose of IMP.

Time frame: From Baseline until Safety Follow-Up (up to Week 72)

Percentage of Participants With TEAEs Leading to Withdrawal From IMP During the Study

An AE is any untoward medical occurrence in a patient or clinical investigation participants administered a pharmaceutical product, which does not necessarily have a causal relationship with this treatment. An AE could therefore be any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease temporally associated with the use of a medicinal (investigational) product, whether or not related to the medicinal (investigational) product. TEAEs were defined as any AEs with an onset date on or after the date of first IMP administration and within 140 days after the final dose of IMP.

Time frame: From Baseline until Safety Follow-Up (up to Week 72)