Improved clinical outcome and biomarkers in adults with papulopustular rosacea treated with doxycycline modified-release capsules in a randomized trial

Background: Patients with rosacea have increased amounts of cathelicidin and protease activity but their usefulness as disease biomarkers is unclear. Objective: We sought to evaluate the effect of doxycycline treatment on cathelicidin expression, protease activity, and clinical response in rosacea. Methods: In all, 170 adults with papulopustular rosacea were treated for 12 weeks with doxycycline 40-mg modified-release capsules or placebo in a multicenter, randomized, double-blind, placebo-controlled study. Clinical response was compared with cathelicidin and protease activity in stratum corneum samples obtained by tape strip and in skin biopsy specimens obtained from a random subset of patients. Results: Treatment with doxycycline significantly reduced inflammatory lesions and improved investigator global assessment scores compared with placebo. Cathelicidin expression and protein levels decreased over the course of 12 weeks in patients treated with doxycycline. Low levels of protease activity and cathelicidin expression at 12 weeks correlated with treatment success. Low protease activity at baseline was a predictor of clinical response in the doxycycline treatment group. Limitations: Healthy control subjects were not studied. Conclusions: Improved clinical outcome correlated with reduced cathelicidin and protease activity, supporting both the mechanism of doxycycline and the potential of these molecules as biomarkers for rosacea.