ABSTRACT
There is an urgent need to develop new and safer antitubercular agents that possess a novel mode of action. We synthesized and evaluated a novel series of 3-aminomethyl 4-halogen benzoxaboroles as Mycobacterium tuberculosis (Mtb) leucyl-tRNA synthetase (LeuRS) inhibitors. A number of Mtb LeuRS inhibitors were identified that demonstrated good antitubercular activity with high selectivity over human mitochondrial and cytoplasmic LeuRS. Further evaluation of these Mtb LeuRS inhibitors by in vivo pharmacokinetics (PK) and murine tuberculosis (TB) efficacy models led to the discovery of GSK3036656 (abbreviated as GSK656). This molecule shows potent inhibition of Mtb LeuRS (IC50 = 0.20 µM) and in vitro antitubercular activity (Mtb H37Rv MIC = 0.08 µM). Additionally, it is highly selective for the Mtb LeuRS enzyme with IC50 of >300 µM and 132 µM for human mitochondrial LeuRS and human cytoplasmic LeuRS, respectively. In addition, it exhibits remarkable PK profiles and efficacy against Mtb in mouse TB infection models with superior tolerability over initial leads. This compound has been progressed to clinical development for the treatment of tuberculosis.
Subject(s)
Antitubercular Agents/chemical synthesis , Antitubercular Agents/pharmacology , Boron Compounds/pharmacology , Enzyme Inhibitors/chemical synthesis , Enzyme Inhibitors/pharmacology , Heterocyclic Compounds, 2-Ring/pharmacology , Leucine-tRNA Ligase/antagonists & inhibitors , Mycobacterium tuberculosis/drug effects , Animals , Antitubercular Agents/pharmacokinetics , Boron Compounds/chemical synthesis , Boron Compounds/pharmacokinetics , Drug Discovery , Enzyme Inhibitors/pharmacokinetics , Female , Heterocyclic Compounds, 2-Ring/chemical synthesis , Humans , Mice , Mice, Inbred C57BL , Mycobacterium tuberculosis/enzymology , Structure-Activity Relationship , Substrate SpecificityABSTRACT
The recent development and spread of extensively drug-resistant and totally drug-resistant resistant (TDR) strains of Mycobacterium tuberculosis highlight the need for new antitubercular drugs. Protein synthesis inhibitors have played an important role in the treatment of tuberculosis (TB) starting with the inclusion of streptomycin in the first combination therapies. Although parenteral aminoglycosides are a key component of therapy for multidrug-resistant TB, the oxazolidinone linezolid is the only orally available protein synthesis inhibitor that is effective against TB. Here, we show that small-molecule inhibitors of aminoacyl-tRNA synthetases (AARSs), which are known to be excellent antibacterial protein synthesis targets, are orally bioavailable and effective against M. tuberculosis in TB mouse infection models. We applied the oxaborole tRNA-trapping (OBORT) mechanism, which was first developed to target fungal cytoplasmic leucyl-tRNA synthetase (LeuRS), to M. tuberculosis LeuRS. X-ray crystallography was used to guide the design of LeuRS inhibitors that have good biochemical potency and excellent whole-cell activity against M. tuberculosis Importantly, their good oral bioavailability translates into in vivo efficacy in both the acute and chronic mouse models of TB with potency comparable to that of the frontline drug isoniazid.
Subject(s)
Antitubercular Agents/pharmacology , Leucine-tRNA Ligase/antagonists & inhibitors , Mycobacterium tuberculosis/drug effects , Protein Synthesis Inhibitors/pharmacology , Administration, Oral , Animals , Antitubercular Agents/administration & dosage , Antitubercular Agents/chemistry , Antitubercular Agents/pharmacokinetics , Disease Models, Animal , Drug Evaluation, Preclinical/methods , Female , Humans , Leucine-tRNA Ligase/chemistry , Leucine-tRNA Ligase/genetics , Mice, Inbred BALB C , Mice, Inbred C57BL , Mice, Inbred Strains , Microbial Sensitivity Tests , Mycobacterium smegmatis/drug effects , Mycobacterium smegmatis/genetics , Mycobacterium tuberculosis/genetics , Protein Synthesis Inhibitors/administration & dosage , Protein Synthesis Inhibitors/chemistry , Protein Synthesis Inhibitors/pharmacokinetics , Structure-Activity Relationship , Tuberculosis/drug therapy , Vero CellsABSTRACT
Gram-negative bacteria cause approximately 70% of the infections in intensive care units. A growing number of bacterial isolates responsible for these infections are resistant to currently available antibiotics and to many in development. Most agents under development are modifications of existing drug classes, which only partially overcome existing resistance mechanisms. Therefore, new classes of Gram-negative antibacterials with truly novel modes of action are needed to circumvent these existing resistance mechanisms. We have previously identified a new a way to inhibit an aminoacyl-tRNA synthetase, leucyl-tRNA synthetase (LeuRS), in fungi via the oxaborole tRNA trapping (OBORT) mechanism. Herein, we show how we have modified the OBORT mechanism using a structure-guided approach to develop a new boron-based antibiotic class, the aminomethylbenzoxaboroles, which inhibit bacterial leucyl-tRNA synthetase and have activity against Gram-negative bacteria by largely evading the main efflux mechanisms in Escherichia coli and Pseudomonas aeruginosa. The lead analogue, AN3365, is active against Gram-negative bacteria, including Enterobacteriaceae bearing NDM-1 and KPC carbapenemases, as well as P. aeruginosa. This novel boron-based antibacterial, AN3365, has good mouse pharmacokinetics and was efficacious against E. coli and P. aeruginosa in murine thigh infection models, which suggest that this novel class of antibacterials has the potential to address this unmet medical need.
Subject(s)
Amino Acyl-tRNA Synthetases/antagonists & inhibitors , Anti-Bacterial Agents/pharmacology , Boron Compounds/pharmacology , Escherichia coli/drug effects , Gram-Negative Bacterial Infections/drug therapy , Pseudomonas aeruginosa/drug effects , Amino Acyl-tRNA Synthetases/metabolism , Animals , Anti-Bacterial Agents/chemical synthesis , Anti-Bacterial Agents/pharmacokinetics , Bacterial Proteins/antagonists & inhibitors , Bacterial Proteins/metabolism , Boron Compounds/chemical synthesis , Boron Compounds/pharmacokinetics , Crystallography, X-Ray , Drug Discovery , Drug Resistance, Multiple, Bacterial/drug effects , Escherichia coli/enzymology , Female , Gram-Negative Bacterial Infections/microbiology , Humans , Leucine/metabolism , Mice , Microbial Sensitivity Tests , Molecular Docking Simulation , Pseudomonas aeruginosa/enzymology , Structure-Activity Relationship , Thigh/microbiology , beta-Lactamase Inhibitors , beta-Lactamases/metabolismABSTRACT
CDC7 is a serine/threonine kinase that has been shown to be required for the initiation and maintenance of DNA replication. Up-regulation of CDC7 is detected in multiple tumor cell lines, with inhibition of CDC7 resulting in cell cycle arrest. In this paper, we disclose the discovery of a potent and selective CDC7 inhibitor, XL413 (14), which was advanced into Phase 1 clinical trials. Starting from advanced lead 3, described in a preceding communication, we optimized the CDC7 potency and selectivity to demonstrate in vitro CDC7 dependent cell cycle arrest and in vivo tumor growth inhibition in a Colo-205 xenograft model.
Subject(s)
Cell Cycle Proteins/antagonists & inhibitors , Protein Kinase Inhibitors/chemistry , Protein Serine-Threonine Kinases/antagonists & inhibitors , Pyrimidinones/chemistry , Pyrimidinones/pharmacokinetics , Animals , Binding Sites , Cell Cycle Checkpoints/drug effects , Cell Cycle Proteins/metabolism , Cell Line, Tumor , Computer Simulation , Humans , Mice , Neoplasms/drug therapy , Protein Kinase Inhibitors/pharmacokinetics , Protein Kinase Inhibitors/therapeutic use , Protein Serine-Threonine Kinases/metabolism , Protein Structure, Tertiary , Pyrimidinones/therapeutic use , Rats , Structure-Activity Relationship , Transplantation, Heterologous , Up-RegulationABSTRACT
A new class of benzoxaborole ß-lactamase inhibitors were designed and synthesized. 6-Aryloxy benzoxaborole 22 inhibited AmpC P99 and CMY-2 with K(i) values in the low nanomolar range. Compound 22 restored antibacterial activity of ceftazidime against Enterobacter cloacae P99 expressing AmpC, a class C ß-lactamase enzyme. The SAR around the arylbenzoxaboroles, which included the influence of linker and substitutions was also established.
