Optimization of Antifungal 1,5-Diaryl-Pyrazole Acetyl-CoA Synthetase Inhibitors

Acetyl-CoA Synthetases (ACS) have emerged as a potential drug target for the treatment of diseases ranging from fungal and parasitic infections to cancer and hyperlipidemia. While species-selective ACS inhibitors have been reported, broad-spectrum inhibition of ACS enzymes has only been achieved with nucleoside-derived, bisubstrate analogs such as alkyl esters of adenosine monophosphate (AMP). Previously, we identified the diaryl pyrazole AR-12 as a non-nucleoside inhibitor of S. cerevisiae ACS with broad-spectrum antifungal activity. In this study, we undertook a medicinal-chemistry approach to optimize the AR-12 scaffold with the goals of improving its pharmacology and activity against ACS enzymes from human fungal pathogens such as Candida albicans, Cryptococcus neoformans, and Aspergillus fumigatus. These efforts have led to the improved on-target activity for a set of analogs against multiple fungal enzymes. We identified key substituents that are critical determinants of the ACS inhibition displayed by this diaryl pyrazole class of inhibitors. Modeling and molecular dynamics calculations also indicate that these improved molecules likely bind in the same region of the ACS active site in which the alkyl-AMP esters bind. Finally, the most active diaryl pyrazole has improved mammalian cytotoxicity and pharmacology relative to AR-12. However, additional optimization of this class of ACS inhibitors will be needed to generate a molecule with efficacy in preclinical animal models.