A 52-week, open-label study of the efficacy and safety of ixekizumab, an anti-interleukin-17A monoclonal antibody, in patients with chronic plaque psoriasis

Background: Patients with moderate to severe plaque psoriasis demonstrated positive responses to ixekizumab, an anti-interleukin-17A monoclonal antibody, in a phase-II, randomized, placebo-controlled trial. Objective: We sought to evaluate long-term efficacy and safety of ixekizumab. Methods: After receiving 10, 25, 75, or 150 mg of ixekizumab or placebo during randomized, placebo-controlled trial, patients with less than 75% improvement from baseline on the Psoriasis Area and Severity Index (PASI) score (PASI75) entered open-label extension (OLE); patients with PASI75 or higher entered a treatment-free period (weeks 20-32), then entered OLE after meeting response criteria. During OLE, patients received 120 mg of subcutaneous ixekizumab every 4 weeks. Results: In all, 120 patients entered OLE; 103 completed 52 weeks or more of treatment. Overall, 77% of patients achieved PASI75 at week 52 (nonresponder imputation). Patients who responded to treatment in the randomized, placebo-controlled trial maintained a high-level response by week 52 of OLE (PASI75 = 95%; 90% improvement from baseline on the PASI score = 94%; 100% improvement from baseline on the PASI score = 82%). Irrespective of dose in the randomized, placebo-controlled trial, each group had similar response rates at week 52 of OLE. The exposure-adjusted incidence rate for adverse events was 0.47 and for serious adverse events was 0.06 per patient-year during OLE. Limitations: No control group, small sample sizes, and bias toward retention of patients with positive responses limit interpretation. Conclusion: A high proportion of patients responded to ixekizumab therapy and maintained clinical responses over 1 year of treatment with no unexpected safety signals.