Efficacy and safety of mirikizumab in psoriasis: results from a 52‐week, double‐blind, placebo‐controlled, randomized withdrawal, phase III trial (OASIS‐1)

BACKGROUND: Interleukin‐23 inhibitors are effective and safe for treating moderate‐to‐severe plaque psoriasis. OBJECTIVES: To evaluate the efficacy and safety of mirikizumab in adult patients with moderate‐to‐severe plaque psoriasis through 52 weeks in a phase III randomized controlled trial. METHODS: OASIS‐1 (NCT03482011) was a double‐blind, placebo‐controlled, randomized withdrawal, phase III trial. Patients (n = 530, randomized 4 : 1) received subcutaneous mirikizumab 250 mg or placebo every 4 weeks (Q4W) through week 16. Coprimary endpoints were superiority of mirikizumab vs. placebo on static Physician’s Global Assessment (sPGA; score of 0 or 1 with ≥ 2‐point improvement) and ≥ 90% improvement in Psoriasis Area and Severity Index (PASI 90, responders) at week 16. Mirikizumab responders were rerandomized (1 : 1 : 1) to mirikizumab 250 mg every 8 weeks (Q8W), mirikizumab 125 mg Q8W, or placebo Q8W through week 52. Secondary endpoints were evaluated at weeks 16 and 52. Safety was monitored in all patients. RESULTS: All primary and key secondary endpoints were met. At week 16, sPGA(0,1) responses were significantly greater with mirikizumab (293 of 423, 69·3%) than placebo (seven of 107, 6·5%) (P < 0·001). PASI 90 response was also greater with mirikizumab (272 of 423, 64·3%) than placebo (seven of 107, 6·5%) (P < 0·001). Significantly more patients in the mirikizumab arms achieved PASI 75 and PASI 100 (mirikizumab 349, 82·5% and 137, 32·4%; placebo 10, 9·3% and 1, 0·9%, respectively; all P < 0·001). At week 52, PASI 90, PASI 100 and sPGA(0,1) responses were mirikizumab 250Q4W/placeboQ8W (N = 91; 19%, 10%, 18%), mirikizumab 250Q4W/125Q8W (N = 90; 86%, 59%, 86%) and mirikizumab 250Q4W/250Q8W (N = 91; 86%, 60%, 82%; all P < 0·001), respectively. Rates of serious adverse events were similar across treatments (induction: mirikizumab 1·2% vs. placebo 1·9%; maintenance: mirikizumab 250Q4W/125Q8W 1%, mirikizumab 250Q4W/250Q8W 3% vs. placebo 3%). No deaths occurred. CONCLUSIONS: Mirikizumab was superior to placebo at week 16 and maintained efficacy through week 52, with no new safety signals. What is already known about this topic? Interleukin (IL)‐23 is a key cytokine in the pathogenesis of psoriasis. Drugs targeting the p19 subunit of IL‐23 have recently been approved for the treatment of adult patients with moderate‐to‐severe plaque psoriasis. Patients with moderate‐to‐severe plaque psoriasis achieved significantly greater improvements in skin measures and patient‐reported quality‐of‐life measures after 16 weeks when treated every 8 weeks with mirikizumab compared with placebo in a phase II clinical trial. What does this study add? Compared with placebo, mirikizumab demonstrated high levels of efficacy at week 16 in a large phase III trial; safety profiles were similar between the mirikizumab and placebo arms. After week 16, patients maintained on doses of mirikizumab 250 mg every 8 weeks (Q8W) or 125 mg Q8W showed similar efficacy and favourable safety profiles over 52 weeks, whereas patients switched to placebo gradually lost efficacy over time.