Discovery of novel spiroquinoxaline derivatives as potent antifungal agents for the treatment of cryptococcal meningitis

Cryptococcal meningitis (CM), caused by Cryptococcus neoformans (C. neoformans), is marked by a rapidly rising incidence and mortality. Furthermore, the WHO has designated C. neoformans as a highest-priority pathogen within its critical fungal pathogens list. Novel antifungal agents and new therapeutic strategies for CM are urgently needed. Herein, a series of novel spiroquinoxaline antifungal compounds were discovered by phenotypic screening and structural optimization. Notably, compound B1 exhibited a potent in vitro antifungal activity against C. neoformans (MIC80 = 1–4 μg/mL). In a murine model of CM, compound B1 significantly reduced the brain fungal burden. Mechanism studies showed that compound B1 substantially suppressed key virulence factors of C. neoformans, including capsule formation, biofilm development, and melanin production, and promoted intracellular accumulation of reactive oxygen species and lipid peroxides. It is indicated that compound B1 provoked oxidative-stress-mediated cellular damage, thereby exerting antifungal activity. This study offered a novel promising lead for therapeutic development against cryptococcosis.