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 IC(50) of 102.8 nM and inhibits CrtN activity with an IC(50) 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.