Clemizole inhibits CrtN-driven staphyloxanthin biosynthesis in Staphylococcus aureus to enhance host immune clearance

The growing threat of Staphylococcus aureus, including methicillin resistant strains, calls for therapies that disarm virulence. Staphyloxanthin, a carotenoid pigment, protects S. aureus from oxidative killing and supports immune evasion. Here we identify clemizole, an FDA approved antihistamine, as a direct inhibitor of CrtN, a key enzyme in staphyloxanthin biosynthesis. Clemizole suppresses pigment with an IC50 of 102.8 nM and inhibits CrtN activity with an IC50 of 2.57 μM, increasing killing by human whole blood, macrophages, neutrophils and oxidative stress. It remains active in S. aureus and Pseudomonas aeruginosa coculture. Surface plasmon resonance, docking, and mutagenesis confirm CrtN binding. In a murine skin infection model, clemizole reduces bacterial burden, accelerates wound healing, improves tissue architecture, and dampens local and systemic inflammation. These data validate CrtN as a tractable antivirulence target and support clemizole as a scaffold to promote host mediated clearance. Host immune clearance of Staphylococcus aureus is potentiated through disruption of CrtN-dependent staphyloxanthin biosynthesis, rendering the pathogen vulnerable to innate immune cell mediated killing in vivo.