Efficacy and safety of guselkumab in biologic-naïve patients with active axial psoriatic arthritis: study protocol for STAR, a phase 4, randomized, double-blinded, placebo-controlled trial

Background: Axial involvement constitutes a specific domain of psoriatic arthritis (PsA). Interleukin (IL)-23 inhibitors have demonstrated improvement in axial PsA (axPsA) symptoms, but have not shown efficacy in treating ankylosing spondylitis (AS), suggesting differences in axPsA processes and treatments. In a post hoc, pooled analysis of patients with investigator- and imaging-confirmed sacroiliitis in two phase 3, randomized, placebo-controlled studies (DISCOVER-1 and DISCOVER-2), patients treated with guselkumab, an IL-23p19 inhibitor, had greater axial symptom improvements compared with placebo. Confirmatory imaging at baseline was restricted to the sacroiliac (SI) joints, occurred prior to/at screening, and was locally read. Methods: The STAR study will prospectively assess efficacy outcomes in PsA patients with magnetic resonance imaging (MRI)-confirmed axial inflammation. Eligible, biologic-naïve patients with PsA (N = 405) for ≥ 6 months and active disease (≥ 3 swollen and ≥ 3 tender joints, C-reactive protein [CRP] ≥ 0.3 mg/dL) despite prior non-biologic disease-modifying antirheumatic drugs, apremilast, and/or nonsteroidal anti-inflammatory drugs will be randomized (1:1:1) to guselkumab every 4 weeks (Q4W); guselkumab at week (W) 0, W4, then every 8 weeks (Q8W); or placebo with crossover to guselkumab at W24, W28, then Q8W. Patients will have Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) score ≥ 4, spinal pain component score (0–10 visual analog scale) ≥ 4, and screening MRI-confirmed axial involvement (positive spine and/or SI joints according to centrally read Spondyloarthritis Research Consortium of Canada [SPARCC] score ≥ 3 in ≥ 1 region). The primary endpoint is mean change from baseline in BASDAI at W24; multiplicity controlled secondary endpoints at W24 include AS Disease Activity Score employing CRP (ASDAS), Disease Activity Index for PsA (DAPSA), Health Assessment Questionnaire – Disability Index (HAQ-DI), Investigator’s Global Ass