Brilacidin is a nonpeptidic anti-infective in a new class of defensin mimetics used for the research of eye infections.

Brilacidin demonstrates higher potency against Gram-positive bacteria (except SV) than against Gram-negative bacteria, attributing its antibacterial efficacy primarily to bacterial cell membrane depolarization. It exhibits notable in vitro activity against Gram-positive strains, and a 0.5% topical formulation shows minimal irritation. Moreover, in a methicillin-resistant S. aureus (MRSA) keratitis model, where the corneal epithelium was removed, 0.5% Brilacidin achieved efficacy comparable to Vancomycin (VAN). Staphylococcus aureus (SA) and Staphylococcus epidermidis (SE) display the lowest minimum inhibitory concentrations (MICs) among the tested bacterial groups. The MIC90s for Brilacidin against Streptococcus pneumonia (SP), Streptococcus viridians (SV), Moraxella (MS), Haemophilus influenza (HI), Pseudomonas aeruginosa (PA), and Serratia marcescens (SM) are significantly higher, being 4, 32, 256, 32, 16, and 128 times respectively, compared to SA and SE.

Brilacidin at different concentrations exhibits varying levels of ocular irritancy in the NZW rabbit model when applied topically seven times at 30-minute intervals over three hours. Specifically, Brilacidin at a concentration of 1% is mildly irritating with a maximum mean total score (MMTS) of 23.0. Concentrations of 0.5% (MMTS 6.5) and 0.25% (MMTS 4.0) are minimally irritating, while 0.1% (MMTS 2.0) and TBS (MMTS 1.0) are practically nonirritating. This data suggests a dose-dependent relationship between Brilacidin concentration and ocular toxicity.