Placebo Response in Phase 3 Trials of Systemic Therapies for Moderate-to-Severe Plaque Psoriasis:A Systematic Review and Meta-Analysis

Background: Wide fluctuations in placebo responses have been reported in phase 3 trials of systemic therapies for moderate-to-severe plaque psoriasis. Methods: In this systematic review and meta-analysis, we assessed placebo responses in phase 3 trials of systemic therapies for moderate-to-severe plaque psoriasis. The medical databases PubMed Medline, Embase, and Web of Science were searched for studies reporting on phase 3 psoriasis trials. A proportion meta-analysis determined the proportion of placebo-treated psoriasis patients obtaining a 75, 90, or 100% reduction in Psoriasis Area and Severity Index (PASI), that is, PASI75, PASI90, or PASI100, respectively, at week 12. In the assessment of PASI75 response, 44 trials with a total number of 7,972 patients were included. Conclusion: In pooled analyses, 5.2% (95% CI 4.7-5.7%) obtained PASI75, 2.1% (95% CI 1.7-2.4%) obtained PASI90, and 0.3% (95% CI 0.1-0.5%) obtained PASI100 among placebo receivers. No temporal changes were observed. The overall proportion of placebo responders in phase 3 psoriasis trials is low and does not appear to be increasing in recent years.