The high lethality of Staphylococcus aureus infections and the emergence of antibiotic resistance make the development of new antibiotics urgent. Our previous work identified a hit compound h1 (AF-353) as a novel Mycobacterium tuberculosis (Mtb) dihydrofolate reductase (DHFR) inhibitor. Herein, we analyzed the antimicrobial profile of h1 and performed a comprehensive structure–activity relationship (SAR) assay based on h1. The representative compound j9 exhibited potent antibacterial activity against S. aureus without cross-resistance to other antimicrobial classes. Multiple genetic and biochemical approaches showed that j9 directly binds to SaDHFR, resulting in strong inhibition of its enzymatic activity (IC₅₀ = 0.97 nM). Additionally, j9 had an acceptable in vivo safety profile and oral bioavailability (F = 40.7%) and also showed favorable efficacy in a mouse model of methicillin-resistant S. aureus (MRSA) skin infection. Collectively, these findings identified j9 as a novel SaDHFR inhibitor with the potential to combat drug-resistant S. aureus infections.

中文翻译：

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5-(5-碘-2-异丙基-4-甲氧基苯氧基)嘧啶-2,4-二胺 (AF-353) 衍生物作为新型 DHFR 金黄色葡萄球菌抑制剂的设计、合成和生物学评价


金黄色葡萄球菌感染的高致死率和抗生素耐药性的出现使得新型抗生素的开发刻不容缓。我们之前的工作鉴定了一个热门化合物h1 ( AF-353 ) 作为一种新型结核分枝杆菌( Mtb ) 二氢叶酸还原酶 (DHFR) 抑制剂。在此，我们分析了h1的抗菌谱，并基于h1进行了全面的构效关系 (SAR) 测定。代表性化合物j9对金黄色葡萄球菌表现出有效的抗菌活性，且与其他抗菌药物没有交叉耐药性。多种遗传和生化方法表明， j9直接与Sa DHFR 结合，导致其酶活性受到强烈抑制 (IC ₅₀ = 0.97 nM)。此外， j9具有可接受的体内安全性和口服生物利用度（ F = 40.7%），并且在耐甲氧西林金黄色葡萄球菌(MRSA) 皮肤感染小鼠模型中也显示出良好的疗效。总的来说，这些发现确定j9是一种新型Sa DHFR 抑制剂，具有对抗耐药金黄色葡萄球菌感染的潜力。