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
   • Patient global assessment of disease activity
   • Patient assessment of pain
   • Health Assessment Questionnaire - Disability Index (HAQ-DI)
   • High-sensitivity C-reactive protein (hsCRP).

Full analysis set; Non-responder imputation incorporating multiple imputation (MI) to handle missing data due to COVID-19 (NRI-C) was used in the analysis.

The Health Assessment Questionnaire Disability Index is a patient-reported questionnaire that measures the degree of difficulty a person has in accomplishing tasks in 8 functional areas (dressing, arising, eating, walking, hygiene, reaching, gripping, and errands and chores) over the past week. Participants assessed their ability to do each task on a scale from 0 (without any difficulty) to 3 (unable to do). Scores were averaged to provide an overall score ranging from 0 to 3, where 0 represents no disability and 3 represents very severe, high-dependency disability.

A negative change from Baseline in the overall score indicates improvement.

Full analysis set; a mixed effect model repeat measurement (MMRM) analysis with longitudinal data from observed cases up to Week 24, excluding data after initiation of rescue medication or initiation of concomitant medications for psoriatic arthritis (PsA) use that could meaningfully impact efficacy assessment, was used.

PASI is a composite score based on the percentage of the body surface area (BSA) affected by psoriasis and the intensity of erythema (reddening), induration (thickening or hardening of the skin), and desquamation (peeling of the skin) of lesions assessed at 4 anatomic sites (head, upper extremities, trunk, and lower extremities). At each location, the percentage of BSA involvement is assigned a score from 0 (no involvement) to 6 (90% to 100% involvement), and erythema, induration, and desquamation are scored on a scale from 0 (no symptoms) to 4 (very marked).

The PASI score ranges from 0 (no psoriasis) to 72 (very severe psoriasis). A PASI 90 response is the percentage of participants who achieved at least a 90% reduction (improvement) from Baseline in PASI score.

Full analysis set participants with Baseline psoriasis BSA involvement ≥ 3%; Non-responder imputation incorporating multiple imputation to handle missing data due to COVID-19 (NRI-C) was used in the analysis.

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
   • Patient global assessment of disease activity
   • Patient assessment of pain
   • Health Assessment Questionnaire - Disability Index (HAQ-DI)
   • High-sensitivity C-reactive protein (hsCRP).

Full analysis set; Non-responder imputation incorporating multiple imputation to handle missing data due to COVID-19 (NRI-C) was used in the analysis.

A participant was classified as achieving MDA if 5 of the following 7 criteria were met:

• Tender joint count (out of 68 joints) ≤ 1
• Swollen joint count (out of 66 joints) ≤ 1
• PASI score ≤ 1 (score ranges from 0 - 72) or percent BSA involved with psoriasis ≤ 3%
• Patient's assessment of pain ≤ 15 (VAS from 0 to 100)
• Patient's Global Assessment of disease activity ≤ 20 (VAS from 0 to 100)
• HAQ-DI score ≤ 0.5 (index score ranges from 0 to 3)
• Leeds Enthesitis Index ≤ 1 (assesses the presence or absence of enthesitis at 3 bilateral sites, for an overall score range from 0 to 6)

Full analysis set; Non-responder imputation incorporating multiple imputation to handle missing data due to COVID-19 (NRI-C) was used in the analysis.

The investigator assessed each fingernail for onycholysis (separation of the nail plate from the nail bed) and oil-drop (salmon patch) dyschromia (reddish-brown discoloration under the nail plate) on a scale of 0 (none present) to 3 (>30% of the nail), pitting (small, sharply defined depressions in the nail surface) on a scale of 0 (0 pits present) to 3 (> 50 pits present), and nail plate crumbling on a scale of 0 (no crumbling) to 3 (>50% of nail has crumbling) and presence (1) or absence (0) of leukonychia (white spots), splinter hemorrhages, nail bed hyperkeratosis, and red spots in the lunula.

The mNAPSI score is calculated as the sum of all the components for all of the participant's fingernails giving a range of possible scores from 0 (absence of nail psoriasis) to 130 (the most severe nail psoriasis). A negative change from Baseline indicates improvement.

Full analysis set with nail psoriasis at Baseline; a mixed effect model repeat measurement analysis with longitudinal data from observed cases up to Week 24, excluding data after initiation of rescue medication or initiation of concomitant medications for psoriatic arthritis use that could meaningfully impact efficacy assessment, was used.

The PGA-F is a clinician-rated outcomes assessment used to measure the severity of signs and symptoms associated with fingernail psoriasis. Participant's fingernails were assessed separately for nail bed signs and nail matrix signs of disease on a scale from 0 (clear) to 4 (severe). A participant's overall global score is the worse of the nail bed score and nail matrix score. For example, if a participant had a nail bed score '2' and a nail matrix score of '4,' this participant's overall score was '4.' A negative change from Baseline indicates improvement.

Full analysis set with nail psoriasis at Baseline; a mixed effect model repeat measurement analysis with longitudinal data from observed cases up to Week 24, excluding data after initiation of rescue medication or initiation of concomitant medications for psoriatic arthritis use that could meaningfully impact efficacy assessment, was used.

Resolution of enthesitis is defined as a Leeds Enthesitis Index (LEI) score = 0.

LEI is an enthesitis measure developed specifically for PsA and assesses the presence or absence of tenderness at the following 3 bilateral enthesial sites: medial femoral condyles, lateral epicondyles of the humerus, and Achilles tendon insertions. Tenderness on examination is recorded as either present (coded as 1), absent (coded as 0), or not assessed for each of the 6 sites. The LEI is calculated by taking the sum of the scores from the 6 sites. The LEI ranges from 0 to 6 (worst).

To increase the sample size due to the smaller number of participants with enthesitis at Baseline, the pre-specified analysis of the resolution of enthesitis included pooled data from KEEPsAKE 1 (this study) and the companion study KEEPsAKE 2 (M15-998; NCT03671148).

Full analysis set participants with a Baseline LEI > 0; Includes pooled data from KEEPsAKE 1 (this study) and the companion study M15-998 (NCT03671148; KEEPsAKE2). Non-responder imputation incorporating multiple imputation to handle missing data due to COVID-19 (NRI-C) was used in the analysis.

Resolution of dactylitis is defined as a Leeds Dactylitis Index (LDI) score = 0.

LDI basic is a score based on finger circumference and tenderness, assessed across all digits. The LDI basic measures the ratio of the circumference of the affected digit to the circumference of the digit on the opposite hand or foot, using a minimum difference of 10% to define a dactylitic digit. The ratio of circumference is multiplied by a tenderness score (1 for tender, 0 for non-tender). If both sides of a digit are considered involved, or the circumference of the contralateral digit cannot be obtained, a standard reference table is used. Scores from each digit are summed to provide the final LDI. A higher LDI indicates worse dactylitis.

To increase sample size due to the smaller number of participants with dactylitis at Baseline, the pre-specified analysis of the resolution of dactylitis included pooled data from KEEPsAKE 1 (this study) and the companion study KEEPsAKE 2 (M15-998; NCT03671148).

Full analysis set participants with a Baseline LDI > 0; Includes pooled data from KEEPsAKE 1 (this study) and the companion study M15-998 (NCT03671148; KEEPsAKE2). Non-responder imputation incorporating multiple imputation to handle missing data due to COVID-19 (NRI-C) was used in the analysis.

The Sharp-van der Heijde modified scoring method for PsA measures the level of joint damage from radiographs of the hands and feet, and was assessed by 2 independent, blinded readers.

Joint erosion severity was assessed in 20 joints in each hand and wrist and 6 joints in each foot. Each joint was scored from 0 (no erosion) to 5 for hands/wrists or to 10 for feet (complete collapse). The total erosion score ranges from 0 to 320 (worst).

Joint space narrowing (JSN) was assessed in 20 joints of each hand and wrist, and 6 joints of each foot, from 0 (normal) to 4 (complete loss of joint space, bony ankylosis, or luxation). The total JSN score ranges from 0 to 208 (worst).

Joints with gross osteolysis or pencil in cup were assigned the maximum score for both erosions and JSN.

The total mTSS score is the sum of the joint erosion and JSN scores and ranges from 0 (normal) to 528 (worst).

Full analysis set participants with available data at Baseline; linear extrapolation was used for participants who discontinued prior to Week 24 or who were rescued prior to Week 24.

The Short Form 36-Item Health Survey (SF-36) Version 2 is a self-administered questionnaire that measures the impact of disease on overall quality of life during the past 4 weeks. The SF-36 consists of 36 questions in eight domains (physical function, pain, general and mental health, vitality, social function, physical and emotional health).

The physical component summary is a weighted combination of the 8 subscales with positive weighting for physical functioning, role-physical, bodily pain, and general health. The SF-36 PCS ranges from 0 to 100. A linear algorithm was applied to the calculation of the PCS which has a normative mean value of 50. Higher scores are associated with less disability; a score of 100 is equivalent to no disability and a score of 0 is equivalent to maximum disability. A positive change from Baseline score indicates improvement.

Full analysis set; a mixed effect model repeat measurement analysis with longitudinal data from observed cases up to Week 24, excluding data after initiation of rescue medication or initiation of concomitant medications for psoriatic arthritis use that could meaningfully impact efficacy assessment, was used.

The FACIT-Fatigue questionnaire is a self-administered patient questionnaire that consists of 13 questions designed to measure the degree of fatigue experienced by participants in the previous 7 days, including physical fatigue (e.g., I feel tired), functional fatigue (e.g., trouble finishing things), emotional fatigue (e.g., frustration), and social consequences of fatigue (e.g., limits social activity). Participants respond to the questions on a scale from 0 (not at all) to 4 (very much).

The FACIT-Fatigue score is computed by summing the item scores, after reversing those items that are worded in the negative direction. The FACIT-Fatigue score ranges from 0 to 52, where higher scores represent less fatigue.

A positive change from Baseline indicates improvement.

Full analysis set; a mixed effect model repeat measurement analysis with longitudinal data from observed cases up to Week 24, excluding data after initiation of rescue medication or initiation of concomitant medications for psoriatic arthritis (PsA) use that could meaningfully impact efficacy assessment, was used.

Participants who met the following 3 conditions for improvement from Baseline were classified as meeting the ACR50 response criteria:

1. ≥ 50% improvement in 68-tender joint count;

2. ≥ 50% improvement in 66-swollen joint count; and

3. ≥ 50% improvement in at least 3 of the 5 following parameters:

   • Physician global assessment of disease activity
   • Patient global assessment of disease activity
   • Patient assessment of pain
   • Health Assessment Questionnaire - Disability Index (HAQ-DI)
   • High-sensitivity C-reactive protein (hsCRP).

Full analysis set; Non-responder imputation incorporating multiple imputation to handle missing data due to COVID-19 (NRI-C) was used in the analysis.

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
   • Patient global assessment of disease activity
   • Patient assessment of pain
   • Health Assessment Questionnaire - Disability Index (HAQ-DI)
   • High-sensitivity C-reactive protein (hsCRP).

Full analysis set; Non-responder imputation incorporating multiple imputation to handle missing data due to COVID-19 (NRI-C) was used in the analysis.