Lack of improvement after short‐term topical antistaphylococcal endolysin SA.100 therapy in patients with mild‐to‐moderate atopic dermatitis: Results from a randomized, vehicle‐controlled trial

Atopic dermatitis (AD) is a chronic immune-mediated inflammatory skin disease. An overgrowth of Staphylococcus aureus (S. aureus) and decreased microbial diversity is apparent in 70%-90% of AD patients. SA.100 is a recombinant endolysin targeting S. aureus that might be a novel treatment for patients with mild-to-moderate AD. To test safety, pharmacodynamics and efficacy of SA.100 a double-blind, randomized, vehicle-controlled trial in 53 subjects with mild-to-moderate AD was performed. Patients were randomized equally to topical SA.100 or vehicle with stratification for S. aureus positivity. SA.100 was safe and well tolerated. No reduction of S. aureus and no changes in microbiome features were seen after 2 weeks of treatment. Additionally, no statistically significant changes in clinical or patient-reported outcomes were observed compared to vehicle. In conclusion, topical SA.100 was safe and well tolerated in patients with mild-to-moderate AD, but our findings do not support short-term clinical use.