Treatment of psoriasis with topical sirolimus: preclinical development and a randomized, double-blind trial

Background Systemically administered sirolimus has demonstrated efficacy in psoriasis in a multicentre European study. Objectives To determine the efficacy and safety of topically applied sirolimus in treating psoriasis. Methods In vitro studies were followed by a pilot study designed to determine if sirolimus penetrates human skin, and by a randomized, double-blind, left-right comparative, dose-ranging study consisting of treatment with 2.2% sirolimus for 6 weeks and 8% sirolimus for an additional 6 weeks in 24 patients with stable, chronic plaque psoriasis. The primary outcome measure was clinical score. Secondary measures were ultrasound plaque thickness, plaque erythema, and computerized image analysis of immunohistochemical stains for immunocytes and proliferating cells. Pharmacokinetics and blood chemistry monitoring for safety were also performed. Results A significant reduction in the clinical score (P = 0.03) (mean score 9.1 following sirolimus vs. 11.2 in control) was achieved with topical sirolimus. Measurements of plaque thickness and erythema did not show significant improvement with treatment. Computerized image analysis of biopsies showed a significant reduction in CD4+ cells (P = 0.0054) and proliferating cells (stained by Ki-67) in the epidermis (P = 0.0153) with sirolimus treatment compared with control. Conclusions Topically applied sirolimus penetrates normal skin and may have some antipsoriatic and immunosuppressive activity.