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.