ABSTRACT
Infectious diseases caused by resistant Gram-negative bacteria have become a serious problem, and the development of therapeutic drugs with a novel mechanism of action and that do not exhibit cross-resistance with existing drugs has been earnestly desired. UDP-3-O-acyl-N-acetylglucosamine deacetylase (LpxC) is a drug target that has been studied for a long time. However, no LpxC inhibitors are available on the market at present. In this study, we sought to create a new antibacterial agent without a hydroxamate moiety, which is a common component of the major LpxC inhibitors that have been reported to date and that may cause toxicity. As a result, a development candidate, TP0586532, was created that is effective against carbapenem-resistant Klebsiella pneumoniae and does not pose a cardiovascular risk.
Subject(s)
Amidohydrolases/antagonists & inhibitors , Anti-Bacterial Agents/pharmacology , Drug Discovery , Enzyme Inhibitors/pharmacology , Escherichia coli/drug effects , Imidazoles/pharmacology , Klebsiella pneumoniae/drug effects , Amidohydrolases/metabolism , Anti-Bacterial Agents/chemical synthesis , Anti-Bacterial Agents/chemistry , Crystallography, X-Ray , Dose-Response Relationship, Drug , Enzyme Inhibitors/chemical synthesis , Enzyme Inhibitors/chemistry , Escherichia coli/enzymology , Imidazoles/chemical synthesis , Imidazoles/chemistry , Klebsiella pneumoniae/enzymology , Microbial Sensitivity Tests , Models, Molecular , Molecular Structure , Structure-Activity RelationshipABSTRACT
UDP-3-O-acyl-N-acetylglucosamine deacetylase (LpxC) is a zinc metalloenzyme that catalyzes the first committed step in the biosynthesis of Lipid A, an essential component of the cell envelope of Gram-negative bacteria. The most advanced, disclosed LpxC inhibitors showing antibacterial activity coordinate zinc through a hydroxamate moiety with concerns about binding to other metalloenzymes. Here, we describe the discovery, optimization, and efficacy of two series of compounds derived from fragments with differing modes of zinc chelation. A series was evolved from a fragment where a glycine moiety complexes zinc, which achieved low nanomolar potency in an enzyme functional assay but poor antibacterial activity on cell cultures. A second series was based on a fragment that chelated zinc through an imidazole moiety. Structure-guided design led to a 2-(1S-hydroxyethyl)-imidazole derivative exhibiting low nanomolar inhibition of LpxC and a minimum inhibitory concentration (MIC) of 4 µg/mL against Pseudomonas aeruginosa, which is little affected by the presence of albumin.
Subject(s)
Amidohydrolases/antagonists & inhibitors , Anti-Bacterial Agents/pharmacology , Bacterial Proteins/antagonists & inhibitors , Chelating Agents/pharmacology , Enzyme Inhibitors/pharmacology , Anilides/pharmacology , Anti-Bacterial Agents/chemical synthesis , Chelating Agents/chemical synthesis , Drug Discovery , Enzyme Inhibitors/chemical synthesis , Escherichia coli/drug effects , Escherichia coli/enzymology , Imidazoles/pharmacology , Microbial Sensitivity Tests , Molecular Structure , Piperidines/pharmacology , Pseudomonas aeruginosa/drug effects , Pseudomonas aeruginosa/enzymology , Structure-Activity Relationship , Zinc/chemistryABSTRACT
The development of effective respiratory syncytial virus (RSV) fusion glycoprotein (F protein) inhibitors against both wild-type and the D486N-mutant F protein is urgently required. We recently reported a 15-membered macrocyclic pyrazolo[1,5-a]pyrimidine derivative 4 that exhibited potent anti-RSV activities against not only wild-type, but also D486N-mutant F protein. However, NMR studies revealed that the 15-membered derivative 4 existed as a mixture of atropisomers. An optimization study of the linker moiety between the 2-position of the benzoyl moiety and the 7-position of the pyrazolo[1,5-a]pyrimidine scaffold identified a 16-membered derivative 42c with an amide linker that showed a rapid interconversion of atropisomers. Subsequent optimization of the 5-position of the pyrazolo[1,5-a]pyrimidine scaffold and the 5-position of the benzoyl moiety resulted in the discovery of a potent clinical candidate 60b for the treatment of RSV infections.
