Real-World Effectiveness of Bimekizumab in Predominantly Difficult-to-Treat Patients with Psoriatic Arthritis Followed in a Combined Dermatology–Rheumatology Clinic: A 24-Week Multicenter Study

Introduction: Bimekizumab (BKZ), a monoclonal antibody targeting interleukin (IL)-17A and IL-17F, has shown high efficacy in clinical trials. However, real-world data on its use in psoriatic arthritis (PsA) are limited. This study aimed to evaluate the effectiveness and safety of BKZ over 24 weeks in a real-world setting. Methods: A retrospective, multicenter study was conducted at two Italian rheumatology centers, enrolling adult patients with PsA who initiated BKZ treatment between January 2023 and February 2025. Clinical data were collected at baseline, week 12, and week 24. Results: Forty patients with PsA were included. Of these, 75% had failed at least two biologic and/or targeted synthetic disease-modifying antirheumatic drugs (b/tsDMARDs) prior to BKZ and 25/40 (62.5%) had failed at least one IL-17A inhibitor (IL-17Ai). Among these 25 patients, 32% experienced a primary failure and 68% a secondary failure. The median baseline Disease Activity in Psoriatic Arthritis (DAPSA) score was 22.9 (17.5–27.2), decreasing to 6.0 (3.1–12.8) at week 24 (p < 0.001). By week 24, 72.5% achieved DAPSA low disease activity (LDA), and 25% achieved DAPSA remission. The median swollen joint count (SJC) decreased from 3.0 (0.8–5.3) to 0.0 (IQR 0.0–1.0), and median tender joint count (TJC) decreased from 4.5 (3.0–7.3) to 1.0 (0.0–2.0) (both p < 0.001). Pain visual analog scale (VAS) and Patient Global Assessment (PGA) improved significantly, from 7.0 (6.0–8.0) and 7.5 (6.5–8.0) at baseline to 2.0 (1.0–5.0) and 2.0 (1.0–4.5) at week 24 (both p < 0.001). Skin involvement also improved, with 51.5% achieving Psoriasis Area and Severity Index (PASI) 100 by week 24. The safety profile was favorable; 15% of patients developed mild oral candidiasis, none of which required treatment discontinuation. Conclusion: BKZ demonstrated rapid and sustained improvements in PsA symptoms in a challenging real-world population, with a favorable safety profile.