Discovery of Benzocycloalkane Derivatives Efficiently Blocking Bacterial Virulence for the Treatment of Methicillin-Resistant S. aureus (MRSA) Infections by Targeting Diapophytoene Desaturase (CrtN).

Antivirulence strategies are now attracting interest for the inherent mechanism of action advantages. In our previous work, diapophytoene desaturase (CrtN) was identified to be an attractive and drugable target for fighting pigmented S. aureus infections. In this research, we developed a series of effective benzocycloalkane-derived CrtN inhibitors with submicromolar IC50. Analogue 8 blocked the pigment biosynthesis of three MRSA strains with a nanomolar IC50 value. Corresponding to its mode of action, 8 did not function as a bactericidal agent. 8 could sensitize S. aureus to immune clearance. In vivo, 8 was proven to be efficacious in an S. aureus Newman sepsis model and abscess formation model. For two typical MRSAs, USA400 MW2 and Mu50, 8 significantly decreased the staphylococcal loads in the liver and kidneys. Moreover, 8 showed minimal antifungal activity compared to that of NTF. In summary, 8 has the potential to be developed as a therapeutic drug, especially against intractable MRSA issues.