The sPGA is the physician's determination of the participant's Psoriasis (Ps) lesions overall at a given time point. Lesions were categorized by descriptions for induration, erythema, and scaling. Participant's Ps was assessed as 0 (clear), 1 (minimal), 2 (mild), 3 (moderate), 4 (severe), or 5 (very severe). An sPGA responder was defined as having a post-baseline sPGA score of "0" or "1" with at least a 2-point improvement from baseline. Participants who did not meet the clinical response criteria or had missing data at Week 52 were considered non-responders for Non-Responder Imputation (NRI) analysis.

All randomized participants analyzed according to the treatment to which they were assigned. As pre-specified in the analysis plan, outcome measures will not be reported for the Maximum Extended Enrollment (ME2) arms/groups but only for the main global study arms/groups.

The PASI combines the extent of body surface involvement in 4 anatomical regions (head, trunk, arms, and legs) and the severity of scaling, redness, and plaque induration/infiltration (thickness) in each region, yielding an overall score of 0 for no Ps to 72 for the most severe disease. For each region the percent area of skin involved was estimated from 0 (0%) to 6 (90%-100%) and severity was estimated by clinical signs of erythema, induration and scaling with a scores range from 0 (no involvement) to 4 (severe involvement). Each area is scored separately and the scores then combined for the final PASI. Final PASI calculated as: sum of severity parameters for each region * area score * weighing factor [head (0.1), upper limbs (0.2), trunk (0.3), lower limbs (0.4)]. Overall scores range from 0 (no Ps) to 72 (the most severe disease). Participants who did not meet the clinical response criteria or had missing data at Week52 were considered non-responders for NRI analysis.

All randomized participants analyzed according to the treatment to which they were assigned. As pre-specified in the analysis plan, outcome measures will not be reported for the Maximum Extended Enrollment (ME2) arms/groups but only for the main global study arms/groups.

The sPGA is the physician's determination of the participant's Ps lesions overall at a given time point. Lesions were categorized by descriptions for induration, erythema, and scaling. Participant's Ps was assessed as 0 (clear), 1 (minimal), 2 (mild), 3 (moderate), 4 (severe), or 5 (very severe). An sPGA responder was defined as having a post-baseline sPGA score of "0" or "1" with at least a 2-point improvement from baseline. Participants who did not meet the clinical response criteria or had missing data at Week 52 were considered non-responders for Non-Responder Imputation (NRI) analysis.

All randomized participants analyzed according to the treatment to which they were assigned. As pre-specified in the analysis plan, outcome measures will not be reported for the Maximum Extended Enrollment (ME2) arms/groups but only for the main global study arms/groups.

PASI combines the extent of body surface involvement in 4 anatomical regions (head, trunk, arms, and legs) and the severity of scaling, redness, and plaque induration/infiltration (thickness) in each region, yielding an overall score of 0 for no Ps to 72 for the most severe disease. For each region the percent area of skin involved was estimated from 0 (0%) to 6 (90%-100%) and severity was estimated by clinical signs of erythema, induration and scaling with a scores range from 0 (no involvement) to 4 (severe involvement). Each area is scored separately and the scores then combined for the final PASI. Final PASI calculated as: sum of severity parameters for each region * area score * weighing factor [head (0.1), upper limbs (0.2), trunk (0.3), lower limbs (0.4)]. Overall scores range from 0 (no Ps) to 72 (the most severe disease).

All randomized participants analyzed according to the treatment to which they were assigned. As pre-specified in the analysis plan, outcome measures will not be reported for the Maximum Extended Enrollment (ME2) arms/groups but only for the main global study arms/groups.

The PASI combines the extent of body surface involvement in 4 anatomical regions (head, trunk, arms, and legs) and the severity of scaling, redness, and plaque induration/infiltration (thickness) in each region, yielding an overall score of 0 for no Ps to 72 for the most severe disease. For each region the percent area of skin involved was estimated from 0 (0%) to 6 (90%-100%) and severity was estimated by clinical signs of erythema, induration and scaling with a scores range from 0 (no involvement) to 4 (severe involvement). Each area is scored separately and the scores then combined for the final PASI. Final PASI calculated as: sum of severity parameters for each region * area score * weighing factor [head (0.1), upper limbs (0.2), trunk (0.3), lower limbs (0.4)]. Overall scores range from 0 (no Ps) to 72 (the most severe disease).

All randomized participants analyzed according to the treatment to which they were assigned. As pre-specified in the analysis plan, outcome measures will not be reported for the Maximum Extended Enrollment (ME2) arms/groups but only for the main global study arms/groups.

The PASI combines the extent of body surface involvement in 4 anatomical regions (head, trunk, arms, and legs) and the severity of scaling, redness, and plaque induration/infiltration (thickness) in each region, yielding an overall score of 0 for no Ps to 72 for the most severe disease.

Least Squares mean (LSmean) was calculated using Mixed-Effects Model of Repeated Measures (MMRM) analysis including dosing regimen, country, baseline weight category, baseline value, visit, dosing regimen-by-visit, and baseline value-by-visit interactions as fixed factors, with variance-covariance structure set to unstructured.

All randomized participants analyzed according to the treatment to which they were assigned and had a baseline and post-baseline measurement for PASI. As pre-specified in the analysis plan, outcome measures will not be reported for the Maximum Extended Enrollment (ME2) arms/groups but only for the main global study arms/groups.

The PASI combines the extent of body surface involvement in 4 anatomical regions (head, trunk, arms, and legs) and the severity of scaling, redness, and plaque induration/infiltration (thickness) in each region, yielding an overall score of 0 for no Ps to 72 for the most severe disease.

Least Squares mean (LSmean) was calculated using Mixed-Effects Model of Repeated Measures (MMRM) analysis including dosing regimen, country, baseline weight category, baseline value, visit, dosing regimen-by-visit, and baseline value-by-visit interactions as fixed factors, with variance-covariance structure set to unstructured.

All randomized participants analyzed according to the treatment to which they were assigned and had a baseline and post-baseline measurement for PASI. As pre-specified in the analysis plan, outcome measures will not be reported for the Maximum Extended Enrollment (ME2) arms/groups but only for the main global study arms/groups.

The percentage involvement of psoriasis on each participant's body surface area (BSA) was assessed by the investigator on a continuous scale from 0% (no involvement) to 100% (full involvement), in which 1% corresponds to the size of the participant's hand including palm, fingers and thumb.

LS mean was calculated using MMRM analysis including dosing regimen, country, baseline weight category, baseline value, visit, dosing regimen-by-visit, and baseline value-by-visit interactions as fixed factors, with variance-covariance structure set to unstructured.

All randomized participants analyzed according to the treatment to which they were assigned who had baseline and a post-baseline measurement for BSA affected by Psoriasis. As pre-specified in the analysis plan, outcome measures will not be reported for the Maximum Extended Enrollment (ME2) arms/groups but only for the main global study arms/groups.

The NAPSI is a numeric, reproducible, objective tool for evaluation of fingernail (fn) Ps. This scale is used to evaluate the severity of fn bed Ps and fn matrix Ps by area of involvement in the fn unit. The fn is divided with imaginary horizontal and longitudinal lines into quadrants. Each fn is given a score for fn bed Ps (0 to 4) and fn matrix Ps (0 to 4) depending on presence (score of 1) or absence (score of 0) of any of the features of fn bed and fn matrix Ps in each quadrant. The NAPSI score of a fn is sum of scores in fn bed and fn matrix from each quadrant (maximum of 8). Each fn is evaluated, then the sum of all fn equals the total NAPSI score with a range from 0 to 80 (0 indicates no Ps, 80 indicates worst Ps). LS mean was calculated using MMRM analysis including dosing regimen, country, baseline weight category, baseline value, visit, dosing regimen-by-visit, and baseline value-by-visit interactions as fixed factors, with variance-covariance structure set to unstructured.

All randomized participants analyzed according to the treatment to which they were assigned who had baseline fingernail involvement and had a post-baseline measurement. As pre-specified in the analysis plan, outcome measures will not be reported for the Maximum Extended Enrollment (ME2) arms/groups but only for the main global study arms/groups.

The PSSI is a physician assessment of erythema, induration and desquamation and percent of scalp that is covered with a scores range from 0 (none) to 4 (very severe). The composite score is derived from the sum of scores for erythema, induration, and desquamation multiplied by the score recorded for the extent of the scalp area involved, 1 (<10%) to 6 (90-100%) with a total score ranging from 0 (less severity) to 72 (more severity). LS mean change was calculated using MMRM analysis including dosing regimen, country, baseline weight category, baseline value, visit, dosing regimen-by-visit, and baseline value-by-visit interactions as fixed factors, with variance-covariance structure set to unstructured.

All randomized participants analyzed according to the treatment to which they were assigned and had baseline scalp involvement and had a post-baseline measurement. As pre-specified in the analysis plan, outcome measures will not be reported for the Maximum Extended Enrollment (ME2) arms/groups but only for the main global study arms/groups.

The Palmoplantar PASI is a composite score derived from the sum scores for erythema, induration, and desquamation multiplied by a score for the extent of palm and sole area involvement, ranging from 0 (no PPASI) to 72 (most severe PPASI). The PPASI was only assessed if participants have palmoplantar psoriasis at baseline. LS mean was calculated using MMRM analysis including dosing regimen, country, baseline weight category, baseline value, visit, dosing regimen-by-visit, and baseline value-by-visit interactions as fixed factors, with variance-covariance structure set to unstructured.

All randomized participants analyzed according to the treatment to which they were assigned and had baseline palmoplantar Ps involvement and had post-baseline measurement. As pre-specified in the analysis plan, outcome measures will not be reported for the Maximum Extended Enrollment (ME2) arms/groups but only for the main global study arms/groups.

The Itch NRS is a participant-administered single-item 11-point horizontal scale anchored at 0 and 10, with 0 representing "no itch" and 10 representing "worst itch imaginable." Overall severity of a participant's itching from Ps is indicated by circling the number that best describes the worst level of itching in the past 24 hours. Participants who did not meet the clinical response criteria or had missing data at Week 52 were considered non-responders for Non-Responder Imputation (NRI) analysis.

All randomized participants analyzed according to the treatment to which they were assigned and who had baseline Itch NRS score greater than or equal to (>=) 4. As pre-specified in the analysis plan, outcome measures will not be reported for the Maximum Extended Enrollment (ME2) arms/groups but only for the main global study arms/groups

The DLQI is a simple, participant-administered, 10 question, validated, quality-of-life questionnaire that covers 6 domains: symptoms and feelings, daily activities, leisure, work and school, personal relationships, and treatment. Response categories include "not at all," "a lot," and "very much," with corresponding scores of 1, 2, and 3, respectively, and unanswered ("not relevant") responses scored as "0." Totals range from 0 to 30 (less to more impairment). Participants who did not meet the clinical response criteria or had missing data at Week 52 were considered non-responders for Non-Responder Imputation (NRI) analysis.

All randomized participants analyzed according to the treatment to which they were assigned. As pre-specified in the analysis plan, outcome measures will not be reported for the Maximum Extended Enrollment (ME2) arms/groups but only for the main global study arms/groups.

The DLQI is a simple, participant-administered, 10 question, validated, quality-of-life questionnaire that covers 6 domains: symptoms and feelings, daily activities, leisure, work and school, personal relationships, and treatment. Response categories include "not at all," "a lot," and "very much," with corresponding scores of 1, 2, and 3, respectively, and unanswered ("not relevant") responses scored as "0." Totals range from 0 to 30 (less to more impairment). LS mean change was calculated using MMRM analysis including dosing regimen, country, baseline weight category, baseline value, visit, dosing regimen-by-visit, and baseline value-by-visit interactions as fixed factors, with variance-covariance structure set to unstructured.

All randomized participants analyzed according to the treatment to which they were assigned and who had baseline and post-baseline DLQI data. As pre-specified in the analysis plan, outcome measures will not be reported for the Maximum Extended Enrollment (ME2) arms/groups but only for the main global study arms/groups.

The Itch NRS is a participant-administered single-item 11-point horizontal scale anchored at 0 and 10, with 0 representing "no itch" and 10 representing "worst itch imaginable." Overall severity of a participant's itching from Ps is indicated by circling the number that best describes the worst level of itching in the past 24 hours. LS mean change from baseline in PSSI was calculated using MMRM analysis including dosing regimen, country, baseline weight category, baseline value, visit, dosing regimen-by-visit, and baseline value-by-visit interactions as fixed factors, with variance-covariance structure set to unstructured.

All randomized participants analyzed according to the treatment to which they were assigned and who had baseline and post-baseline Itch NRS data. As pre-specified in the analysis plan, outcome measures will not be reported for the Maximum Extended Enrollment (ME2) arms/groups but only for the main global study arms/groups.

The pain VAS is a participant-administered single-item scale designed to measure Skin pain from Psoriasis using a 0-100 millimeter (mm) horizontal VAS. Overall severity of participant's skin pain from Psoriasis is indicated by placing a single mark on the horizontal 100 mm scale from 0 mm (no skin pain) to 100 mm (severe skin pain). LS mean was calculated using MMRM analysis including dosing regimen, country, baseline weight category, baseline value, visit, dosing regimen-by-visit, and baseline value-by-visit interactions as fixed factors, with variance-covariance structure set to unstructured.

All randomized participants analyzed according to the treatment to which they were assigned and who had baseline and post-baseline skin pain VAS data. As pre-specified in the analysis plan, outcome measures will not be reported for the Maximum Extended Enrollment (ME2) arms/groups but only for the main global study arms/groups.

EQ-5D-5L is a standardized measure of health status used to provide a simple, generic measure of health for clinical and economic appraisal. The EQ-5D-5L consists of 2 components: a descriptive system of the respondent's health and a rating of his/her current health state using a 0 (no pain) to 100mm VAS (severe pain). LS mean was calculated using MMRM analysis including dosing regimen, country, baseline weight category, baseline value, visit, dosing regimen-by-visit, and baseline value-by-visit interactions as fixed factors, with variance-covariance structure set to unstructured.

All randomized participants analyzed according to the treatment to which they were assigned and who had baseline and post baseline EQ-5D-5L VAS data. As pre-specified in the analysis plan, outcome measures will not be reported for the Maximum Extended Enrollment (ME2) arms/groups but only for the main global study arms/groups.

Trough concentrations at steady state of Ixekizumab were evaluated.

All randomized participants analyzed according to treatment to which they were assigned with evaluable PK samples that met the definition of being a trough concentration. As pre-specified in the analysis plan, outcome measures will not be reported for the Maximum Extended Enrollment (ME2) arms/groups but only for the main global study arms/groups.

Number of participants with treatment-emergent positive anti-ixekizumab antibodies was summarized by treatment group.

All randomized participants who received at least 1 dose of Ixekizumab and had evaluable anti-ixekizumab antibody measurement. As pre-specified in the analysis plan, outcome measures will not be reported for the Maximum Extended Enrollment (ME2) arms/groups but only for the main global study arms/groups.