BACKGROUND: Guselkumab is a fully human monoclonal antibody that binds selectively to the p19 subunit of interleukin-23, which has shown efficacy in patients with previous incomplete response to ustekinumab in the NAVIGATE clinical trial. [Correction added on [28-02-2023], after first online publication: 'humanized monoclonal antibody' has been changed to 'fully human monoclonal antibody' in the preceding sentence.] OBJECTIVES: We conducted a 104-week multicenter retrospective study to assess the effectiveness and safety of guselkumab in patients affected by plaque psoriasis with an inadequate response to ustekinumab in a real-life setting. METHODS: Our retrospective study included 233 adults affected by moderate-to-severe plaque psoriasis, enrolled in 14 different Italian centres, and treated with guselkumab after failing therapy with ustekinumab. Patient characteristics and PASI (Psoriasis Area and Severity Index) score at each visit (baseline, weeks 16, 52 and 104) were recorded. The percentages of patients achieving 75%, 90% and 100% (PASI 75, PASI 90 and PASI 100) improvement in PASI, compared with baseline, were registered. RESULTS: At week 52, PASI 75 was reached by 89.88% of patients, PASI 90 by 71.43%, PASI 100 by 58.83% and absolute PASI ≤2 by 90.48%. At week 104, similar effectiveness results were observed. Compared to the NAVIGATE trial, we observed higher rates of PASI 75/90/100. Patients with the involvement of difficult-to-treat areas were significantly less likely to achieve PASI90 and PASI100 at week 16. Obese patients had significantly lower rates of PASI75 and PASI ≤2 at week 52. At week 104, comparable responses were observed among all patients' subgroups, regardless of BMI status, involvement of difficult-to-treat areas, presence of cardiometabolic comorbidities and concomitant psoriatic arthritis. No significant safety findings were reported throughout the study. CONCLUSION: Our data suggest that the efficacy of guselkumab in patients with inadequate response to ustekinumab for plaque psoriasis in 'real-life' clinical practice is comparable with NAVIGATE study with higher percentages of patients achieving PASI90 and PASI100 at weeks 16, 52 and 104.