Abstract
Background/Objectives: Psoriatic arthritis (PsA) is a chronic inflammatory condition that primarily affects the musculoskeletal system and skin. While biologic and targeted synthetic DMARDs have improved treatment, many patients still fail to achieve remission. Combining conventional synthetic disease modifying anti-rheumatic drugs (csDMARDs) with biologic (b) DMARDs or targeted synthetic (ts) DMARDs shows no added benefit over monotherapy with IL-17, IL-23 inhibitors, or JAK inhibitors, unlike TNFi, which benefit from csDMARD co-administration. Guselkumab (GUS) and risankizumab (RKZ) target IL-23 with high specificity. RCTs (DISCOVER 1 and 2, COSMOS) have confirmed GUS efficacy regardless of methotrexate (MTX) use, though liver toxicity was higher with MTX. Real-world data on GUS remain limited, with gaps in understanding its long-term effectiveness and drug survival. The aim of this study is to assess the following three points within a multicenter Italian real-life cohort of PsA patients treated with guselkumab (GUS) and followed for 12 months: (1) effectiveness and safety of GUS; (2) drug retention rate (DRR) and reasons for discontinuation; (3) impact of comorbidities on achieving minimal disease activity (MDA). Methods: This study utilized data from the GISEA registry, which includes centers in different parts of Italy (north, center, south, and islands), and included patients aged 18 and older diagnosed with PsA according to the CASPAR criteria. Results: Data on 170 PsA patients treated with GUS were collected. In the first 6 months, a prompt mean percentage improvement in all clinimetric indexes was observed compared to the baseline. At 6-month follow-up, ACR 20 was reached by 60% of patients, ACR 50 by 30%, ACR 70 by 15%, MDA by 28%, and DAPSA < 14 by 50% of patients in the overall group. Significant differences were found in the rate of ACR 50 in the bDMARD-naive group (50%) compared to one bDMARDs non-responder (NR) (8%) (p = 0.021). At 12-month follow-up, a notable gap was observed in the rate of patients reaching MDA between bDMARD-naive (60%) and one bDMARDs NR (22%) (p = 0.035) and between bDMARD-naive (60%) and ≥2 bDMARDs NRs (22%) (p = 0.024). By using multivariate binary logistic analysis, the predictors of reaching MDA at 12-month follow-up were naive bDMARDs (OR: 7.9, 95% CI: 1.3-44.8, p = 0.019) and a higher value of pGA at baseline (OR: 1.1, 95% CI: 1-1.5; p = 0.046). The presence of comorbidities, including fibromyalgia and obesity, did not seem to affect the reaching of MDA. At 12-month follow-up, the GUS retention rate was 76%, with a mean survival time of 10.5 months ± 0.2 (95% CI: 10-10.9). No significant differences in GUS survival time were found among bDMARD-naive, one bDMARDs NR, and ≥2 bDMARDs NR patients (in the latter, regardless of the previous mechanism of action: TNFi or other mechanism), as well as between patients treated with GUS in monotherapy and those treated in combination with csDMARDs. A low rate (17%) of discontinuation was found due to both primary NR and secondary NR. The high safety of GUS was recorded. In fact, discontinuation due to adverse events (all definable as minor) was observed in just 4% of patients. By using COX regression multivariate analysis, the factors associated with higher GUS discontinuation risk were a more severe baseline PASI (HR: 1.05, 95% CI: 1-1.1, p = 0.038) and higher baseline ESR (HR:1.06, 95% CI: 1-1.03, p = 0.05). Conclusions: Good performance of GUS was observed in both biologic-naive patients and those with failure of previous bDMARDs (regardless of the mechanism of action of the previous drug: TNFi or non-TNFi), presenting good persistence in therapy even when used as a third mechanism of action. Its high safety profile allows the use of GUS even in particularly complex patients.