For those countries where it was required, hepatitis B, hepatitis C and human immunodeficiency virus (HIV) serology testing during the Screening Period were added to the assessment schedule. These tests were already outlined in Exclusion Criterion No. 21 and results of these tests determined eligibility for the study. Thus the addition to the assessment schedule in this amendment was made in order to clarify and remove inconsistencies in the protocol. Collection of SPARCC at the Screening Visit was added to the assessment schedule as it was previously omitted in error. This test was already outlined in Inclusion Criterion No.5 and results of this test determined eligibility for the study. Thus the addition to the assessment schedule in this amendment was made in order to clarify and remove inconsistencies in the protocol.

1. To increase the study feasibility and to ease the study visit burden on patients without compromising the primary and secondary objectives of the study until Week 12.  Inclusion criterion no. 4, an ultrasound entry criterion that was considered too restrictive as it resulted in the most screen failures, was amended to allow inclusion of patients with a total synovitis score ≥ 2 and inflammation related to PD signal ≥ 2 for at least 1 affected joint as observed via PDUS of 48 joints, OR with an inflammation related to PD signal ≥ 1 for at least 2 affected joints as observed via PDUS of 48 joints.  The study visits and associated study assessments at Week 28, 32, 40, 44 and 48 were removed from the open-label Extension Period and home administration of study drug was introduced at these time points. The clinical efficacy assessments (including PDUS assessments) were removed from the double-blind Week 3 visit; and the PDUS assessment was removed from the Week 56 follow-up visit. The Extension Period was optional according to Investigator’s judgment and patient consent and exploratory study objectives only applied to this period. The removal of study visits during the Extension Period did not compromise patient safety given the benefit/ risk of secukinumab had already been assessed and secukinumab was registered in all participating countries. 2. Different aspects of the protocol were clarified following the review of different Ethics Committees (ECs):  Clarification was made in the patient population that patients must have had an inadequate response to non-biologic DMARDs to be consistent with study rationale and primary objective of the study.  The use of rescue medication was amended so it was less restrictive throughout the study and to make it more ethical for the patients randomized to placebo during the first 12 weeks given the risk of potential flare and existence of alternative therapies.

The sample size calculation in the trial was updated keeping in mind the difficulties of recruitment. The initial sample size calculation for this trial was extrapolated from anbultrasound study assessed to evaluate the early response of abatacept on synovitis in patients with rheumatoid arthritis (D’Agostino et al 2016a) given the lack of a previous ultrasound PsA trial with biologics. A blinded sample size re-estimation was supplemented with data from the first 72 patients who reached their Week 12 visit to provide the most accurate estimation. The sample size was adjusted to a new target of 164 patients in total (82 patients per arm). This was the mid-way point of the range plus a 5% adjustment based on the dropout rate of patients prior to Week 12 observed at the time of this calculation. The reduction of sample size from 218 to 164 patients helped achieve completion of the last patient first visit by the end of August 2019. 2. Different aspects of the protocol were clarified following comments from the Health Authorities (HA), Ethics Committees and investigators. a. The dose of non-steroidal anti-inflammatory drugs (NSAIDs) as rescue therapy prior to assessments in the trial until Week 24 was clarified. The requirement for patients to return to their previous NSAIDs’ dose following a transient increase in dose as rescue therapy 48 hours prior to study assessments was considered unethical by investigators and not accepted by patients who were in pain, and was therefore removed from the protocol.