This is a randomized, parallel-group, double-blind, placebo-controlled, multicenter, Phase III study designed to assess efficacy and safety of secukinumab compared to placebo in adult patients with active pSpA, composed of the subsets of undifferentiated pSpA and chronic reactive arthritis. Approximately 324 eligible participants with pSpA will enroll into the study with approximately 162 participants in each of the double-blind arms. This population will be comprised of approximately 292 participants with undifferentiated pSpA and approximately 32 participants with chronic reactive arthritis.~The participants will be stratified 1:1 ratio at randomization (Baseline) according to:~High Sensitivity C-reactive Protein (hsCRP) level: Participants will be equally stratified based on hsCRP (≤5mg/L) or hsCRP (>5 mg/L) as measured at Screening Visit 2 (SV2) with the hsCRP (≤5mg/L) strata capped at 50%.~Sub-type of pSpA: Approximately 90% of randomized participants will be diagnosed with undifferentiated pSpA and up to 10% participants with chronic reactive arthritis.~The trial consists of 5 periods: a screening, double-blind treatment, randomized withdrawal, an open label treatment and safety follow-up period, detailed below:~Screening period- Up to 8 weeks to assess participant's eligibility, composed of 2 visits - SV1 and SV2.~Double-blind Treatment period - Baseline (BSL) (Week 0) to Week 56 [Treatment Period 1]~Eligible participants will be randomized at BSL (Week 0) in a 1:1 ratio to one of the following double-blind arms:~Arm 1 (N=162 participants): Secukinumab 300 mg s.c. at Week 0, 1, 2, 3, 4, then every 4 weeks thereafter up to and including Week 52.~Arm 2 (N= 162 participants): Placebo s.c. at Week 0, 1, 2, 3, 4, then every 4 weeks thereafter up to and including Week 52.~Randomized Withdrawal- (Week 56 to Week 108) [Treatment Period 2]~Open-label Treatment period- (Week 20 to Week 216) [Treatment Period 3]~Safety Follow-up period - Following the EOT visit at Week 216, there will be an End of Treatment (EOS) visit at Week 224 for safety assessments~The primary endpoint analysis will be performed after all participants have completed the Week 16 visit. The investigators, site personnel and monitors will continue to remain blinded to the original treatment assignment that each participant received at randomization until after the database lock for final analysis.~Analysis Plan A is planned after participants have completed the Week 16 assessments. Analysis Plan B is planned after participants have completed the Week 52 assessments in order to support regulatory submission and/or publication purposes. The analysis at Week 108 will be conducted after all participants complete the Treatment Period 2. The final analysis will be conducted after all participants complete the study. Additional analyses may be performed to support interactions with health authorities, as necessary.
The purpose of this study is to investigate the efficacy and safety of subcutaneous (s.c) secukinumab in comparison with placebo for participants with two subtypes of active pSpA i.e. undifferentiated pSpA and chronic reactive arthritis, and with an inadequate response to conventional therapy despite current or previous Non-steroidal Anti Inflammatory Drugs (NSAIDs) and/or csDMARDs. Additionally, the study aims to evaluate efficacy and safety of continuing versus withdrawing secukinumab therapy in maintaining remission in the study population.