Comparison of secukinumab effectiveness in treating psoriatic lesions in patients with psoriasis alone and concomitant psoriatic arthritis: A retrospective longitudinal cohort study

Background Secukinumab, an interleukin-17A inhibitor, has been widely used to treat psoriasis (PsO) and psoriatic arthritis (PsA). However, it remains unclear whether psoriasis patients with PsA achieve comparable effectiveness to those with psoriasis alone. Objective To compare secukinumab's effectiveness in treating psoriatic lesions in psoriasis patients and those with concomitant PsA and to analyse the disparities. Methods A retrospective longitudinal cohort study was conducted on patients treated with secukinumab for PsO and PsA between June 1, 2020 and December 1, 2022. Psoriasis area and severity index (PASI) scores were assessed at weeks 0, 4, 12, 24 and 48. The achievement of PASI 75, PASI 90 and PASI 100 were assessed between the PsO and PsA group with logistic generalised estimating equations using a logit link. Propensity score matching was used for sensitivity analysis. Results 336 psoriatic patients were enrolled, of whom 41 had PsA as well. After adjustment, patients with PsA demonstrated comparable PASI 75/90/100 responses at week 4 but significantly inferior outcomes at weeks 12, 24 and 48 compared to those with psoriasis alone. The treatment disparity in PASI 75 achievement emerged at week 12 (94.9% vs 82.5% odds ratio (OR) 0.264, 95% confidence interval (CI) 0.098-0.711, p =0.008); it was most pronounced at week 48 (95.0% vs 73.3% OR 0.139, 95% CI 0.054-0.356, p <0.001). Limitations Small sample size, retrospective data collection and single-centre validation. Conclusion Concomitant PsA was associated with reduced long-term effectiveness of secukinumab in terms of skin clearance. The difference in efficacy was evident as early as week 12, peaking at week 48, which establishes week 12 as a clinical decision node for reassessment in PsA patients.