The ACR20 is a composite endpoint based on the following assessments: 66/68 swollen joint count (SJC) or tender joint count (TJC), Subject's pain assessment (SPA)-visual analog scale (VAS),Subject's global assessment of disease activity (SGA)-VAS,Physician's global assessment of disease activity (PGA)-VAS, Health Assessment Questionnaire-Disability Index (HAQ-DI), and High sensitivity C-reactive protein (hs-CRP).The baseline value to assess the ACR20 during this study was the same baseline value used to assess the ACR20 during the parent study (ie, the Week 0 assessment in the parent study). Subjects were considered an ACR20 responder at a visit if compared to baseline in the parent study (CHS-0214-02) they achieved: At least 20% decrease in SJC, At least 20% decrease in TJC, and At least 20% improvement in at least 3 of the following 5 measures: C-reactive protein, HAQ-DI, SPA (using a VAS) for pain,SGA (using a VAS), orPGA (using a VAS).

All PASI score assessors must have demonstrated proficiency at performing the PASI. Every attempt was made to use the same assessor for each subject throughout the study. n subjects with PsO, durability of response (maintenance of a PASI-50 response or greater at each assessment) was based on scoring the PsO lesions on a scale of 0 to 4 for 3 characteristics: erythema, induration, and desquamation, and within 4 anatomical regions: head, trunk, upper extremities, and lower extremities. Within each of these regions, the area of involvement was scored on a scale of 0 to 6, with the total score being a weighted average, and weights defined by the area of involvement. The clinician assessed the subject's PsO lesions according to the PASI and provided this score within the case report form at Weeks 0 (as the Week 48 assessment of the parent study), 4, 12, 24, 36, and 48. Subjects were classified as having a PASI-50 response based upon 50% reduction from baseline of the parent study.

The primary efficacy endpoint in Part 1 was the percentage of subjects who achieved ACR20 (20% improvement according to American College of Rheumatology criteria) at week 24 compared to baseline (last non-missing value prior to first dose). Subjects were considered an ACR20 responder if when compared to baseline (last non-missing value prior to first dose), they achieved a 20% decrease in SJC (Swollen joint count), 20% decrease in TJC (Tender joint count), and 20% improvement in 3 of the following 5 measures: high sensitivity C reactive protein(hs-CRP), Health Assessment Questionnaire Disability Index(HAQ-DI), subjects global assessment of pain(SPA, VAS), subject's global assessment of disease activity(SGA-VAS), physician's global assessment of disease activity(PGA-VAS)