ABSTRACT
Novel mechanisms of action and new chemical scaffolds are needed to rejuvenate antibacterial drug discovery, and riboswitch regulators of bacterial gene expression are a promising class of targets for the discovery of new leads. Herein, we report the characterization of 5-(3-(4-fluorophenyl)butyl)-7,8-dimethylpyrido[3,4-b]quinoxaline-1,3(2H,5H)-dione (5FDQD)—an analog of riboflavin that was designed to bind riboswitches that naturally recognize the essential coenzyme flavin mononucleotide (FMN) and regulate FMN and riboflavin homeostasis.
In vitro
, 5FDQD and FMN bind to and trigger the function of an FMN riboswitch with equipotent activity. MIC and time-kill studies demonstrated that 5FDQD has potent and rapidly bactericidal activity against
Clostridium difficile
. In C57BL/6 mice, 5FDQD completely prevented the onset of lethal antibiotic-induced
C. difficile
infection (CDI). Against a panel of bacteria representative of healthy bowel flora, the antibacterial selectivity of 5FDQD was superior to currently marketed CDI therapeutics, with very little activity against representative strains from the
Bacteroides
,
Lactobacillus
,
Bifidobacterium
,
Actinomyces
, and
Prevotella
genera. Accordingly, a single oral dose of 5FDQD caused less alteration of culturable cecal flora in mice than the comparators. Collectively, these data suggest that 5FDQD or closely related analogs could potentially provide a high rate of CDI cure with a low likelihood of infection recurrence. Future studies will seek to assess the role of FMN riboswitch binding to the mechanism of 5FDQD antibacterial action. In aggregate, our results indicate that riboswitch-binding antibacterial compounds can be discovered and optimized to exhibit activity profiles that merit preclinical and clinical development as potential antibacterial therapeutic agents.
摘要
抗菌药物的研发需要新的作用机制和新的化学支架,而细菌基因表达的核糖开关调控因子是一类很有希望发现新线索的靶点。在此,我们报告了 5-(3-(4-氟苯基)丁基)-7,8-二甲基吡啶并[3,4-b]喹喔啉-1,3(2H,5H)-二酮(5FDQD)的特性,它是一种核黄素类似物,旨在与核糖开关结合,而核糖开关能自然识别必需的辅酶黄素单核苷酸(FMN)并调节 FMN 和核黄素的平衡。
体外
在体外,5FDQD 和 FMN 与 FMN 核糖开关结合并触发其功能,两者的活性相当。MIC 和时间杀伤研究表明,5FDQD 对以下细菌具有强效和快速的杀菌活性
艰难梭菌
.在 C57BL/6 小鼠中,5FDQD 可完全阻止由抗生素引起的致命性艰难梭菌感染的发生。
艰难梭菌
感染(CDI)。与一组代表健康肠道菌群的细菌相比,5FDQD 的抗菌选择性优于目前市场上销售的 CDI 治疗药物,但对下列细菌中的代表性菌株活性极低
细菌
,
乳酸杆菌
,
双歧杆菌
,
放线菌
和
普雷沃茨菌属
属。因此,与比较药相比,单次口服 5FDQD 对小鼠可培养的盲肠菌群的改变较小。总之,这些数据表明,5FDQD 或密切相关的类似物有可能提供较高的 CDI 治愈率,同时降低感染复发的可能性。未来的研究将寻求评估 FMN 核糖开关结合在 5FDQD 抗菌作用机制中的作用。总之,我们的研究结果表明,可以发现并优化核糖开关结合型抗菌化合物,使其表现出值得作为潜在抗菌治疗药物进行临床前和临床开发的活性特征。