Secukinumab, a fully human monoclonal antibody, neutralizes interleukin-17A, a cornerstone cytokine driving the multiple manifestations of psoriasis. This post-hoc analysis of the SUPREME study was performed to determine the sustainability of response to secukinumab in terms of Psoriasis Area and Severity Index (PASI) 90 in patients with moderate-to-severe plaque psoriasis. Based on PASI 90 response at week 16, patients were stratified as PASI 90 responders (PASI90R, n = 337) or non-responders (PASI90NR, n = 72). At week 20, 94.2% (n = 295/313) achieved PASI 90/100 response in PASI90R, with response maintained through week 48 (89.6%, n = 189/211). An increased proportion of patients achieved PASI 90/100 response in PASI90NR (week 20: 29.9%, n = 20/67; week 48: 57.1%, n = 20/35). Overall, 64.4% patients achieved absolute PASI score = 0 at week 24 with response sustained to week 48 (66.9%). Secukinumab showed sustained and stable efficacy in maintaining PASI 90 response in patients with moderate-to-severe plaque psoriasis up to week 48.