Antifungal repurposing of clinical chelator DMSA against Cryptococcus neoformans via laccase and histidine biosynthesis inhibition.

As a globally distributed opportunistic fungus, Cryptococcus neoformans poses a significant threat to human health by causing fatal meningitis, which is associated with high mortality and morbidity rates. Current antifungals-polyenes, flucytosine, and azoles-are limited by toxicity and resistance, underscoring the need for new agents. This study evaluated dimercaptosuccinic acid (DMSA), a chelating agent used in the treatment of heavy metal poisoning, beginning with its effect on the virulence factor laccase. DMSA showed broad-spectrum activity against standard (H99, B3501) and clinical isolate strains, with MIC values of 32-64 μg/mL. It inhibited laccase (IC50 = 43.98 μM; Km = 0.547 mM with levodopa) and impaired multiple virulence factors, including capsule formation (43.2% reduction in H99), urease activity (68.6% inhibition in H99 and 53.4% in B3501), as well as biofilm formation and its metabolic activity. In a Galleria mellonella infection model, although survival was not significantly improved, DMSA reduced fungal burden by 30% (P < 0.05), supported by histology and Colony-Forming Units (CFU) counts. Further transcriptomic and nutrient supplementation assays indicated that the antifungal action of DMSA is mediated through interference with histidine biosynthesis, suggesting a mechanism beyond laccase inhibition.