ABSTRACT
Synthetic studies of the antimicrobial secondary metabolite thiomuracin A (1) provided access to analogues in the Northern region (C2-C10). Selective hydrolysis of the C10 amide of lead compound 2 and subsequent derivatization led to novel carbon- and nitrogen-linked analogues (e.g., 3) which improved antibacterial potency across a panel of Gram-positive organisms. In addition, congeners with improved physicochemical properties were identified which proved efficacious in murine sepsis and hamster C. difficile models of disease. Optimal efficacy in the hamster model of C. difficile was achieved with compounds that possessed both potent antibacterial activity and high aqueous solubility.
Subject(s)
Anti-Bacterial Agents/pharmacology , Clostridioides difficile/drug effects , Clostridium Infections/drug therapy , Peptides, Cyclic/pharmacology , Thiazoles/pharmacology , Animals , Anti-Bacterial Agents/chemical synthesis , Anti-Bacterial Agents/chemistry , Cricetinae , Disease Models, Animal , Dose-Response Relationship, Drug , Mice , Microbial Sensitivity Tests , Models, Molecular , Molecular Structure , Peptides, Cyclic/chemical synthesis , Peptides, Cyclic/chemistry , Solubility , Structure-Activity Relationship , Thiazoles/chemical synthesis , Thiazoles/chemistryABSTRACT
Argyrins, produced by myxobacteria and actinomycetes, are cyclic octapeptides with antibacterial and antitumor activity. Here, we identify elongation factor G (EF-G) as the cellular target of argyrin B in bacteria, via resistant mutant selection and whole genome sequencing, biophysical binding studies and crystallography. Argyrin B binds a novel allosteric pocket in EF-G, distinct from the known EF-G inhibitor antibiotic fusidic acid, revealing a new mode of protein synthesis inhibition. In eukaryotic cells, argyrin B was found to target mitochondrial elongation factor G1 (EF-G1), the closest homologue of bacterial EF-G. By blocking mitochondrial translation, argyrin B depletes electron transport components and inhibits the growth of yeast and tumor cells. Further supporting direct inhibition of EF-G1, expression of an argyrin B-binding deficient EF-G1 L693Q variant partially rescued argyrin B-sensitivity in tumor cells. In summary, we show that argyrin B is an antibacterial and cytotoxic agent that inhibits the evolutionarily conserved target EF-G, blocking protein synthesis in bacteria and mitochondrial translation in yeast and mammalian cells.
Subject(s)
Oligopeptides/metabolism , Peptide Elongation Factor G/metabolism , Allosteric Site , Amino Acid Sequence , Animals , Burkholderia/drug effects , Cell Line, Tumor , Conserved Sequence , Crystallography, X-Ray , Humans , Mammals , Microbial Sensitivity Tests , Mitochondrial Proteins/metabolism , Molecular Sequence Data , Mutant Proteins/chemistry , Mutant Proteins/metabolism , Oligopeptides/chemistry , Oligopeptides/pharmacology , Peptide Elongation Factor G/antagonists & inhibitors , Peptide Elongation Factor G/chemistry , Protein Binding/drug effects , Pseudomonas aeruginosa/drug effects , Saccharomyces cerevisiae/metabolism , Sequence Homology, Amino AcidABSTRACT
Synthetic studies of the antimicrobial secondary metabolite thiomuracin A (1) were initiated to improve chemical stability and physicochemical properties. Functional group modifications of 1 included removing the C2-C7 side chain, derivatizing the C84 epoxide region, and altering the C44 hydroxyphenylalanine motif. The resulting derivatives simplified and stabilized the chemical structure and were evaluated for antibacterial activity relative to 1. The simplified structure and improved organic solubility of the derivatives facilitated isolation yields from fermentation broths and simplified the procedures involved for the process. These advancements increased material supply for continued medicinal chemistry optimization and culminated in the identification of 2, a structurally simplified and chemically stable analogue of 1 which retained potent antibiotic activity.
Subject(s)
Anti-Bacterial Agents/chemical synthesis , Peptides, Cyclic/chemical synthesis , Thiazoles/chemical synthesis , Animals , Anti-Bacterial Agents/chemistry , Anti-Bacterial Agents/pharmacology , Clostridioides difficile/drug effects , Crystallography, X-Ray , Enterococcus/drug effects , Escherichia coli/genetics , Escherichia coli/metabolism , Escherichia coli Proteins/biosynthesis , Escherichia coli Proteins/chemistry , Female , Gram-Positive Bacterial Infections/drug therapy , Male , Mice , Microbial Sensitivity Tests , Models, Molecular , Molecular Structure , Peptide Elongation Factor Tu/chemistry , Peptides, Cyclic/chemistry , Peptides, Cyclic/pharmacology , Protein Synthesis Inhibitors/chemical synthesis , Protein Synthesis Inhibitors/chemistry , Protein Synthesis Inhibitors/pharmacology , Rats , Rats, Sprague-Dawley , Staphylococcus aureus/drug effects , Streptococcus pyogenes/drug effects , Structure-Activity Relationship , Thiazoles/chemistry , Thiazoles/pharmacology , Transcription, Genetic/drug effectsABSTRACT
Clostridium difficile (C. difficile) is a Gram positive, anaerobic bacterium that infects the lumen of the large intestine and produces toxins. This results in a range of syndromes from mild diarrhea to severe toxic megacolon and death. Alarmingly, the prevalence and severity of C. difficile infection are increasing; thus, associated morbidity and mortality rates are rising. 4-Aminothiazolyl analogues of the antibiotic natural product GE2270 A (1) were designed, synthesized, and optimized for the treatment of C. difficile infection. The medicinal chemistry effort focused on enhancing aqueous solubility relative to that of the natural product and previous development candidates (2, 3) and improving antibacterial activity. Structure-activity relationships, cocrystallographic interactions, pharmacokinetics, and efficacy in animal models of infection were characterized. These studies identified a series of dicarboxylic acid derivatives, which enhanced solubility/efficacy profile by several orders of magnitude compared to previously studied compounds and led to the selection of LFF571 (4) as an investigational new drug for treating C. difficile infection.
Subject(s)
Anti-Bacterial Agents/chemical synthesis , Clostridioides difficile/drug effects , Enterocolitis, Pseudomembranous/drug therapy , Thiazoles/chemical synthesis , Animals , Anti-Bacterial Agents/pharmacokinetics , Anti-Bacterial Agents/pharmacology , Cricetinae , Crystallography, X-Ray , Enterococcus/drug effects , Escherichia coli Proteins/antagonists & inhibitors , Escherichia coli Proteins/chemistry , Female , Male , Mesocricetus , Mice , Microbial Sensitivity Tests , Models, Molecular , Molecular Structure , Peptide Elongation Factor Tu/antagonists & inhibitors , Peptide Elongation Factor Tu/chemistry , Rats , Rats, Sprague-Dawley , Solubility , Staphylococcus aureus/drug effects , Streptococcus pyogenes/drug effects , Structure-Activity Relationship , Thiazoles/pharmacokinetics , WaterABSTRACT
4-Aminothiazolyl analogues of the antibiotic natural product GE2270 A (1) were designed, synthesized, and optimized for their activity against Gram positive bacterial infections. Optimization efforts focused on improving the physicochemical properties (e.g., aqueous solubility and chemical stability) of the 4-aminothiazolyl natural product template while improving the in vitro and in vivo antibacterial activity. Structure-activity relationships were defined, and the solubility and efficacy profiles were improved over those of previous analogues and 1. These studies identified novel, potent, soluble, and efficacious elongation factor-Tu inhibitors, which bear cycloalkylcarboxylic acid side chains, and culminated in the selection of development candidates amide 48 and urethane 58.
Subject(s)
Anti-Bacterial Agents/chemical synthesis , Carboxylic Acids/chemical synthesis , Gram-Positive Bacterial Infections/drug therapy , Peptides, Cyclic/chemical synthesis , Thiazoles/chemical synthesis , Animals , Anti-Bacterial Agents/chemistry , Anti-Bacterial Agents/pharmacology , Area Under Curve , Carboxylic Acids/chemistry , Carboxylic Acids/pharmacology , Crystallography, X-Ray , Drug Resistance, Bacterial , Female , Gram-Positive Bacteria/drug effects , Gram-Positive Bacteria/genetics , Male , Mice , Microbial Sensitivity Tests , Models, Molecular , Molecular Conformation , Mutation , Peptides, Cyclic/chemistry , Peptides, Cyclic/pharmacology , Rats , Rats, Sprague-Dawley , Sepsis/drug therapy , Solubility , Stereoisomerism , Structure-Activity Relationship , Thiazoles/chemistry , Thiazoles/pharmacologyABSTRACT
Several 2-aminotetralones were identified as novel inhibitors of the bacterial enzymes MurA and MurZ. A number of these inhibitors demonstrated antibacterial activity against Staphylococcus aureus and Escherichia coli with MICs in the range 8-128 microg/ml. Based on structure-activity relationships we propose that the alpha-aminoketone functionality is responsible for the inhibitory activity and evidence is provided to support a covalent mode of action involving the C115 thiol group of MurA/MurZ.
