A Vma13-targeted thiadiazole-succinimide disrupts V-ATPase dependent arginine-polyamine homeostasis to block Candida albicans escape from macrophages

Invasive candidiasis caused by Candida albicans is a life-threatening nosocomial infection with limited therapies and high morbidity and mortality among immunocompromised patients. Within host phagocytes, C. albicans catabolizes arginine to produce ammonia and fuels polyamine biosynthesis, which correlates with phagosomal alkalinization and yeast-to-hypha morphogenesis, facilitating macrophage escape and systemic dissemination. However, new antifungal strategies blocking this fungal escape remain scarce. Here, we characterize the thiadiazole-succinimide derivative ETSI, an arginine-dependent antifungal small molecule with minimal direct growth inhibition under arginine-free conditions yet robust anti-C. albicans activity in arginine-rich microenvironments mimicking the macrophage intracellular niche. Mechanistically, ETSI targets the vacuolar Vma13 to inhibit vacuolar H-ATPase (V-ATPase), dissipating vacuolar proton (H+) gradients and leading to cytoplasmic H+ retention. The accumulated cytoplasmic H+ traps intracellular ammonia and blocks its external release, while impaired vacuolar metabolite sequestration further triggers cytotoxic accumulation of arginine and polyamine metabolites. This dual metabolic perturbation suppresses phagosomal alkalinization, retains C. albicans in yeast form and blocks macrophage escape. ETSI is the first small molecule blocking C. albicans escape via disrupted Vma13/V-ATPase dependent arginine-polyamine homeostasis. This work identifies an intracellular metabolic vulnerability and establishes a niche-targeted antifungal strategy distinct from classic growth-suppressive drugs for treating invasive candidiasis.