High throughput screen reveals four compounds with novel antifungal activity, including a metal-responsive candidate with in vivo efficacy against Candida albicans

Fungal infections represent a growing global health concern, aggravated by the paucity of effective antifungal therapies and the rapid rise of drug resistance. The development of new treatments is challenging due to the shared eukaryotic biology of fungi and human hosts, which restricts selective molecular targets and contributes to issues such as host toxicity and fungistatic activity. These challenges underscore the pressing need for new agents with distinct modes of action. In this study, we identified four promising compounds with novel antifungal activity from a high-throughput screen of 20,000 compounds against the opportunistic fungal pathogen, Candida albicans, namely Z1199266541, Z1024453766, Z56842335, and Z126932704. Subsequently, the compounds were characterized in vitro to assess their spectrum of activity, efficacy against a fluconazole-resistant isolate (CaCi-17), and effectiveness in combination treatments, followed by in vivo evaluation in a Galleria mellonella infection model. Among the candidates, Z56842335 emerged as a lead compound, effectively clearing infection caused by the Candida albicans in this invertebrate model. Mechanistic analyses revealed that the antifungal activity of Z56842335 is mitigated by supplementation with iron, copper, and zinc, indicating a metal-dependent mode of action. Notably, despite its apparent metal-binding capacity, Z56842335 displays a narrow spectrum of activity, targeting only C. albicans and, to a lesser extent C. dubliniensis. This selectivity suggests that, in addition to metal availability, species-specific factors such as differences in metal acquisition, intracellular metal buffering, or compound uptake or accumulation may contribute to susceptibility, highlighting a promising yet mechanistically intriguing avenue for further investigation.