Sample size was increased from 360 to 448 patients (based on a 95% CI). An expected difference of 3% was assumed for the sample size calculation. The re-randomization scheme at Week 17 was adjusted to a ratio of 2:1. The eligibility of patients based on their TB status was made more restrictive in exclusion criteria: Patients with a positive QFT at screening were no longer eligible for participation in the study to minimize the risk of possible TB re-activation. Correction of inclusion criterion: all s.c. injections were to be done at the site thus no explanation of self-administration. Assessment of exploratory PD biomarkers was excluded from the study. To standardize the process and to protect patients’ privacy, it was clarified that the psoriasis lesions were to be photographed only for specific body parts excluding the face. The instructions of storing GP2017 and Humira separated from other investigational medicinal products were removed as deemed not according to the normal routine. The prohibited regimen of topical corticosteroids was specified based on their levels of potency and instructions on how to determine their level of potency were added. It was added that if a patient prematurely discontinued from Treatment Period 1, the Week 17 visit assessments were to be performed as a discontinuation visit. If a patient prematurely discontinued from Treatment Period 2, the Week 35 visit assessments were to be performedd. An ECG assessment was added to Week 17 to match the assessments at Week 35. Safety laboratory at Screening (to provide a baseline laboratory assessment prior to study drug administration) and at Week 39 and final follow up 6 weeks after last dosing were added. The frequency of urine pregnancy tests performed in women of childbearing potential was increased to a minimum of every 4 weeks. An additional vital signs assessment at Visit 9 (Week 13) together with a physical examination was added.

The treatment period was extended to follow the current European guidelines (CHMP/EWP/2454/02) and (CHMP/BMWP/42832/2005), requesting one-year follow up data in case of chronic use. Before the amendment, the last drug administration was to take place at Week 33, which was extended by another 8 treatment visits from Week 35 to Week 49, followed by a last study visit at Week 51. During the Extension Period, safety, immunogenicity and efficacy data were to be collected continuously. Patients in the switching arms were to receive the treatment they had been randomized to at the study start throughout the extension period. Some patients had already completed and left the study after Week 35 (as per study protocol after Protocol amendment 2), when Amendment 3 became effective. The treatment-free follow-up period after the last injection of study treatment, to wash-out GP2017 or Humira, was removed and the study was to end after the Extension Period for all patients. Patients were able to receive a standard treatment after the end of the study to avoid potential disease exacerbation. The assay to measure the binding of ADAs used in this study, developed to ensure a high drug tolerance, was considered not necessary. Therefore, the last ADA assessment was to be performed two weeks after last study drug administration at Week 51. To provide additional results on very sensitive endpoints and as complement to the primary PASI75 analysis, the relative change from baseline in the continuous PASI score was to be evaluated until Week 16 and compared using powered MMRM analyses and analyses applying an ATE approach. Patients were allowed to interrupt study treatment administration, if they had an AE that in the opinion of the investigator needed to be sufficiently resolved before study treatment could be administered again. To account for stratification factors in the primary analysis, systemic therapy and body weight categories were to be included in the analysis as covariates