A Study to Evaluate the Efficacy and Safety of Bimekizumab Compared to Placebo and an Active Comparator in Adult Subjects With Moderate to Severe Chronic Plaque Psoriasis

Percentage of Participants With an IGA 0 Response at Week 16

The Investigator's Global Assessment (IGA) measures the overall psoriasis severity following a 5-point scale (0-4), where scale 0= clear, no signs of psoriasis; presence of post-inflammatory hyperpigmentation, scale 1= almost clear, no thickening; normal to pink coloration; no to minimal focal scaling, scale 2= mild thickening, pink to light red coloration and predominately fine scaling, 3= moderate, clearly distinguishable to moderate thickening; dull to bright red, clearly distinguishable to moderate thickening; moderate scaling and 4= severe thickening with hard edges; bright to deep dark red coloration; severe/coarse scaling covering almost all or all lesions. IGA response was defined as clear \[0\] with at least a two-category improvement from Baseline at Week 16.

Time frame: Week 16

Percentage of Participants With a PASI75 Response at Week 4

The PASI75 response assessments are based on at least 75% improvement in the PASI score from Baseline. This is a scoring system that averages the redness, thickness, and scaliness of the psoriatic lesions (on a 0-4 scale), and weights the resulting score by the area of skin involved. Body divided into 4 areas: head, arms, trunk to groin, and legs to top of buttocks. Assignment of an average score for the 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 the respective section, and weighted by the percentage of the person's affected skin for the respective section. The minimum possible PASI score is 0= no disease, the maximum score is 72= maximal disease.

Time frame: Week 4

Percentage of Participants With a Patient Symptom Diary Response for Pain at Week 16

As Patient-Reported-Outcome (PRO) measure, the PSD (further published as P-SIM) was used to assess key symptoms relevant to patients with moderate to severe plaque psoriasis. Site staff trained participants on the use of the electronic device used to collect ePRO diary data at Screening, device was then dispensed to the participant for home use until Week 16 Visit. The ePRO diary was completed on daily basis from Screening to Week 16 Visit. PSD pain item was assessed daily on a numeric rating scale (NRS) from 0 (no pain) to 10 (very severe pain). PSD score for pain at a given visit was an average of daily values over the week prior to the visit. The response was defined as an improvement (decrease) in pain score higher than the prespecified 1.98 response threshold at Week 16. The endpoint was characterized as percentage of participants with PSD pain response.

Time frame: Week 16

Percentage of Participants With a Patient Symptom Diary Response for Itch at Week 16

A PRO measure, the PSD (further published as P-SIM) was used to assess key symptoms relevant to patients with moderate to severe plaque psoriasis. Site staff trained participants on the use of the electronic device used to collect ePRO diary data at Screening, device was then dispensed to participant for home use until Week 16 Visit. The ePRO diary was completed on daily basis from Screening to Week 16 Visit. PSD itch item was assessed daily on a NRS from 0 (no itch) to 10 (very severe itch). PSD score for itch was an average of daily values over the week prior to the visit. The response was defined as an improvement (decrease) in itch score higher than the prespecified 2.39 response threshold at Week 16. The endpoint was characterized as percentage of participants with a PSD itch response.

Time frame: Week 16

Percentage of Participants With a Patient Symptom Diary Response for Scaling at Week 16

As PRO measure, the PSD (further published as P-SIM) was used to assess key symptoms relevant to patients with moderate to severe plaque psoriasis. Site staff trained participants on the use of the electronic device used to collect ePRO diary data at Screening, device was then dispensed to the participant for home use until Week 16 Visit. The ePRO diary was completed on daily basis from Screening to Week 16 Visit. PSD scaling item was assessed daily on a NRS from 0 (no scaling) to 10 (very severe scaling). PSD score for scaling was an average of daily values over the week prior to the visit. The response was defined as an improvement (decrease) in scaling score higher than the prespecified 2.86 response threshold at Week 16. The endpoint was characterized as percentage of participants with a PSD scaling response.

Time frame: Week 16

Percentage of Participants With a Scalp IGA Response (Clear or Almost Clear) at Week 16 for Participants With Scalp Psoriasis (PSO) >=2 at Baseline

Only participants with scalp involvement at Baseline completed the scalp IGA. Participants with scalp involvement at Baseline were defined as those with a scalp IGA score \>0 at Baseline. Scalp lesions were assessed in terms of clinical signs of redness, thickness, and scaliness using a 5-point scale (0=Clear, 1=Almost Clear, 2=Mild, 3=Moderate, 4= Severe). Scalp IGA 0/1 response at Week 16 was defined as clear (0) or almost clear (1) with at least a 2-category improvement from Baseline to Week 16.

Time frame: Week 16

Percentage of Participants With a PASI90 Response at Week 12

The PASI90 response assessments are based on at least 90% improvement in the PASI score from Baseline. This is a scoring system that averages the redness, thickness, and scaliness of the psoriatic lesions (on a 0-4 scale), and weights the resulting score by the area of skin involved. Body divided into 4 areas: head, arms, trunk to groin, and legs to top of buttocks. Assignment of an average score for the 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 the respective section, and weighted by the percentage of the person's affected skin for the respective section. The minimum possible PASI score is 0= no disease, the maximum score is 72= maximal disease.

Time frame: Week 12

Percentage of Participants With a PASI90 Response at Week 52

The PASI90 response assessments are based on at least 90% improvement in the PASI score from Baseline. This is a scoring system that averages the redness, thickness, and scaliness of the psoriatic lesions (on a 0-4 scale), and weights the resulting score by the area of skin involved. Body divided into 4 areas: head, arms, trunk to groin, and legs to top of buttocks. Assignment of an average score for the 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 the respective section, and weighted by the percentage of the person's affected skin for the respective section. The minimum possible PASI score is 0= no disease, the maximum score is 72= maximal disease.

Time frame: Week 52

Percentage of Participants With an IGA (Clear or Almost Clear With at Least a 2-category Improvement From Baseline) Response at Week 12

The Investigator's Global Assessment (IGA) measures the overall psoriasis severity following a 5-point scale (0-4), where scale 0= clear, no signs of psoriasis; presence of post-inflammatory hyperpigmentation, scale 1= almost clear, no thickening; normal to pink coloration; no to minimal focal scaling, scale 2= mild thickening, pink to light red coloration and predominately fine scaling, 3= moderate, clearly distinguishable to moderate thickening; dull to bright red, clearly distinguishable to moderate thickening; moderate scaling and 4= severe thickening with hard edges; bright to deep dark red coloration; severe/coarse scaling covering almost all or all lesions. IGA response was defined as clear \[0\] or almost clear \[1\] with at least a two-category improvement from Baseline at Week 12.

Time frame: Week 12

Percentage of Participants With an IGA (Clear or Almost Clear With at Least a 2-category Improvement From Baseline) Response at Week 52

The Investigator's Global Assessment (IGA) measures the overall psoriasis severity following a 5-point scale (0-4), where scale 0= clear, no signs of psoriasis; presence of post-inflammatory hyperpigmentation, scale 1= almost clear, no thickening; normal to pink coloration; no to minimal focal scaling, scale 2= mild thickening, pink to light red coloration and predominately fine scaling, 3= moderate, clearly distinguishable to moderate thickening; dull to bright red, clearly distinguishable to moderate thickening; moderate scaling and 4= severe thickening with hard edges; bright to deep dark red coloration; severe/coarse scaling covering almost all or all lesions. IGA response was defined as clear \[0\] or almost clear \[1\] with at least a two-category improvement from Baseline at Week 52.

Time frame: Week 52

Number of Treatment Emergent Adverse Events (TEAEs) Adjusted by Duration of Subject Exposure to Study Treatment During the Initial Treatment Period

The number of TEAEs adjusted by duration of exposure to study treatment was scaled such that provided an incidence rate per 100 patient-years. If a participant had multiple events, the time of exposure was calculated to the first occurrence of the Adverse Event (AE) being considered. If a participant had no events, the total time at risk was used.

Time frame: From Baseline to end of Initial Treatment Period, including the Safety Follow-Up visit for those withdrawn from IMP (up to 36 weeks)

Number of Serious Adverse Events (SAEs) Adjusted by Duration of Subject Exposure to Study Treatment During the Initial Treatment Period

The number of SAEs adjusted by duration of exposure to study treatment was scaled such that it provided an incidence rate per 100 patient-years. If a participant had multiple events, the time of exposure was calculated to the first occurrence of the AE being considered. If a participant had no events, the total time at risk was used.

Time frame: From Baseline to end of Initial Treatment Period, including the Safety Follow-Up visit for those withdrawn from IMP (up to 36 weeks)

Number of TEAEs Leading to Withdrawal Adjusted by Duration of Subject Exposure to Study Treatment During the Initial Treatment Period

The number of TEAEs leading to discontinuation adjusted by duration of exposure to study treatment was scaled such that it provided an incidence rate per 100 patient-years. If a participant had multiple events, the time of exposure was calculated to the first occurrence of the AE being considered. If a participant had no events, the total time at risk was used.

Time frame: From Baseline to end of Initial Treatment Period, including the Safety Follow-Up visit for those withdrawn from IMP (up to 36 weeks)

Number of Treatment Emergent Adverse Events (TEAEs) Adjusted by Duration of Subject Exposure to Study Treatment During the Maintenance Treatment Period

The number of TEAEs adjusted by duration of exposure to study treatment was scaled such that it provided an incidence rate per 100 patient-years. If a participant had multiple events, the time of exposure was calculated to the first occurrence of the Adverse Event (AE) being considered. If a participant had no events, the total time at risk was used.

Time frame: From Week 16 to Safety Follow-Up (up to 52 weeks duration)

Number of Serious Adverse Events (SAEs) Adjusted by Duration of Subject Exposure to Study Treatment During the Maintenance Treatment Period

The number of SAEs adjusted by duration of exposure to study treatment was scaled such that it provided an incidence rate per 100 patient-years. If a participant had multiple events, the time of exposure was calculated to the first occurrence of the AE being considered. If a participant had no events, the total time at risk was used.

Time frame: From Week 16 to Safety Follow-Up (up to 52 weeks duration)

Number of TEAEs Leading to Withdrawal Adjusted by Duration of Subject Exposure to Study Treatment During the Maintenance Treatment Period

The number of TEAEs leading to discontinuation adjusted by duration of exposure to study treatment was scaled such that it provided an incidence rate per 100 patient-years. If a participant had multiple events, the time of exposure was calculated to the first occurrence of the AE being considered. If a participant had no events, the total time at risk was used.

Time frame: From Week 16 to Safety Follow-Up (up to 52 weeks duration)