Ixekizumab for the treatment of psoriatic arthritis: an Italian multicentric retrospective observational study

: Ixekizumab (IXE), an IL-17 A inhibitor, demonstrated efficacy in clinical trials in patients with psoriatic arthritis (PsA), and favorable data have emerged from real-world evidence studies on psoriasis as well. However, real-world data specific to PsA remain limited. This study aims to assess IXE effectiveness in reducing disease activity in patients with PsA and determine its drug retention rate (DRR) over 24 months. The secondary aim is to identify factors potentially affecting long-term persistence on therapy. A retrospective observational study was conducted. Consecutive adult patients meeting the CASPAR criteria for PsA and treated with IXE for ≥ 3 months were included. Patients were evaluated at regular intervals on a routine clinical basis for disease activity and quality of life assessment. 132 patients (78 females, 54 males; mean age 59.1 ± 11.9 years) were included. At baseline, the median (IQR) Disease Activity in Psoriatic Arthritis (DAPSA) was 16.2 (7.7), and the visual analogue scale (VAS) for pain was 6.5 (3.0). In patients with axial involvement, the median (IQR) Ankylosing Spondylitis Disease Activity Score – C-reactive protein (ASDAS-CRP) was 3.4 (1.3), and the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) was 5.0 (1.5). IXE treatment was associated with statistically significant reductions in DAPSA (p < 0.001), ASDAS-CRP (p < 0.001), BASDAI (p < 0.001), VAS-pain (p < 0.001), Health Assessment Questionnaire (HAQ) (p < 0.001), erythrocyte sedimentation rate (p = 0.014), and CRP (p = 0.004) over 24 months. At 24 months, remission and low disease activity, according to DAPSA thresholds, were achieved by 46.7% and 93.3% of patients, respectively, while Very Low Disease Activity and Minimal Disease Activity criteria were met by 16.0% and 34.0%, respectively. IXE DRR was 82.1%, 76.3%, and 73.3% at 12, 18, and 24 months, respectively, with lower values in female patients (p = 0.036). No differences were observed in IXE DRR when stratifying the cohort by axial involvement (p = 0.84), prior exposure to biologics or tsDMARDs (p = 0.68), or body mass index (BMI) categories (p = 0.48). In conclusion, IXE enabled rapid and sustained disease control in patients with PsA across multiple disease domains. The high DRR supports its long-term use, regardless of prior biologic exposure or BMI. Gender differences in IXE treatment response may warrant further exploration.