Discovery and Optimization of Novel <i>Sa</i>FabI Inhibitors as Specific Therapeutic Agents for MRSA Infection

Abstract

As the rate-limiting enzyme in fatty acid biosynthesis, <i>Staphylococcus aureus</i> enoyl-acyl carrier protein reductase (<i>Sa</i>FabI) emerges as a compelling target for combating methicillin-resistant <i>S. aureus</i> (MRSA) infections. Herein, compound <b>1</b>, featuring a 4-(1<i>H</i>-benzo[<i>d</i>]imidazol-2-yl)pyrrolidin-2-one scaffold, was identified as a potent <i>Sa</i>FabI inhibitor (IC₅₀ = 976.8 nM) from an in-house library. Subsequent optimization yielded compound <b>n31</b>, with improved inhibitory efficacy on enzymatic activity (IC₅₀ = 174.2 nM) and selective potency against <i>S. aureus</i> (MIC = 1-2 μg/mL). Mechanistically, <b>n31</b> directly inhibited <i>Sa</i>FabI in cellular contexts. Moreover, <b>n31</b> exhibited favorable safety and pharmacokinetic profiles, and dose-dependently treated MRSA-induced skin infections, outperforming the approved drug, linezolid. The chiral separation of <b>n31</b> resulted in <b>(</b><i><b>S</b></i><b>)-n31</b>, with superior activities (IC₅₀ = 94.0 nM, MIC = 0.25-1 μg/mL) and <i>in vivo</i> therapeutic efficacy. In brief, our research proposes <b>(</b><i><b>S</b></i><b>)-n31</b> as a promising candidate for <i>Sa</i>FabI-targeted therapy, offering specific anti-<i>S. aureus</i> efficacy and potential for further development.