Harnessing Random Peptide Mixtures to Overcome Multidrug-Resistant Fungal Infections

Invasive fungal infections, characterized by high mortality rates, present a growing health concern due to the limited spectrum of effective drugs, escalating numbers of immunocompromised patients, and the rapid emergence of drug resistance. Addressing this challenge requires alternative therapeutic strategies. Candidate drugs should fulfill key requirements to qualify for clinical use, including negligible host toxicity, high in vitro and in vivo antifungal activity, in vivo stability, and modes of action that reduce the potential for the emergence of resistant strains. Antimicrobial peptides (AMPs) stand out as a promising class of compounds to combat antimicrobial resistance. Leveraging the unique properties of AMPs, we previously developed a novel approach to synthesize random peptide mixtures (RPMs) with robust bactericidal activity against drug-resistant bacteria. Here, we evaluate the antifungal potential of RPMs. Our findings demonstrate high potency of FK20 (L-Phenylalanine-L-Lysine, 20-mer) RPM against Candida auris, a newly emerged multidrug-resistant human pathogen. In vitro studies demonstrated effective eradication of C. auris, with scanning electron microscopy revealing outer membrane damage and confocal microscopy confirming cellular penetration. FK20 also demonstrates activity against C. albicans, C. glabrata, and C. parapsilosis, broadening therapeutic scope. Importantly, experimental evolution assays confirm FK20 RPM hinders resistance development in C. auris. A synergistic activity was observed when FK20 treatment was combined with caspofungin to inhibit C. auris biofilm formation. Lastly, we demonstrate the significant therapeutic potential of FK20 RPM in a murine model of systemic candidiasis. Our findings underscore the promise of RPMs as novel, efficacious, and safe treatment for drug-resistant fungal infections. ImportanceThe rising prevalence of invasive fungal infections, particularly among immunocompromised individuals, has become a critical public health concern. However, antifungal drug development has not kept pace with this growing need, and treatment options remain limited to a small number of drug classes. The emergence of multidrug-resistant fungal pathogens, such as Candida auris, further exacerbates this crisis by reducing the efficacy of existing therapeutics and increasing the risk of treatment failure. In this study, we evaluate the antifungal potential of FK20, a random peptide mixture (RPM) composed of L-phenylalanine and L-lysine. FK20 displays potent activity against C. auris and other clinically relevant Candida species, impairs biofilm formation, and exhibits synergy with caspofungin. Importantly, FK20 limits the emergence of resistance and demonstrates therapeutic efficacy in a murine model of systemic candidiasis. These findings establish RPMs as a promising new class of antifungals with broad-spectrum activity and clinical potential against drug-resistant fungal infections.