Brilacidin (formerly PMX-30063) is a polymer-based antibiotic and an investigational new drug, that was studied in human clinical trials, and represents a new class of antibiotics called host defense protein mimetics. Brilacidin is an antibiotic that works by disrupting bacterial cell membranes, mimicking defensins that play a role in innate immunity. Brilacidin has shown great efficacy in phase II clinical trials against acute Staphylococcus aureus skin and skin structure infections, comparable to that of the lipopeptidic drug daptomycin, which is currently used clinically to treat drug-resistant staph infections. Brilacidin also has potent broad-spectrum activity in vitro against several other Gram-positive and Gram-negative pathogenic bacteria, including several multidrug-resistant strains.