Designed Antimicrobial Peptides for Topical Treatment of Antibiotic Resistant Acne Vulgaris

Acne vulgaris, caused by the Gram-positive bacterium Cutibacterium acnes, is a prevalent dermatologic condition with substantial cutaneous and psychological morbidity. Mild acne is treated with topical antibiotics with more severe inflammatory forms requiring the prolonged use of oral antibiotics, resulting in antimicrobial resistance development. Innovative treatment alternatives, providing complete microbicidal eradication with minimal safety issues and limited susceptibility to microbial resistance, are fervently sought. Designed antimicrobial peptides (dAMPs) are engineered analogs of naturally occurring AMPs that possess a reduced likelihood of developing bacterial resistance. Seven novel dAMP sequences were screened for in vitro bactericidal effectiveness against antibiotic resistant C. acnes clinical isolates. Five peptides (RP444, RP551, RP554, RP556, and RP557) exhibited potent in vitro antibacterial activity. The Therapeutic Index, a measure of specificity for killing multidrug resistant C. acnes over mammalian cells, was determined using bioluminescent human keratinocytes. The Therapeutic Index was highest for the disulfide dAMP, RP556, with a value of 130. The lead dAMP candidate RP556, was further evaluated in a multidrug-resistant C. acnes intradermal murine infection model. A topical application of 5 mg/mL RP556 (0.5%) eliminated infection. If these preclinical results are translated clinically, dAMPs may become a viable topical monotherapy for the treatment of recalcitrant acne infections.