RESUMEN
Multidrug-resistant (MDR) Pseudomonas aeruginosa infections are a major clinical challenge. Many isolates are carbapenem resistant, which severely limits treatment options; thus, novel therapeutic combinations, such as imipenem-relebactam (IMI/REL), ceftazidime-avibactam (CAZ/AVI), ceftolozane-tazobactam (TOL/TAZO), and meropenem-vaborbactam (MEM/VAB) were developed. Here, we studied two extensively drug-resistant (XDR) P. aeruginosa isolates, collected in the United States and Mexico, that demonstrated resistance to IMI/REL. Whole-genome sequencing (WGS) showed that both isolates contained acquired GES ß-lactamases, intrinsic PDC and OXA ß-lactamases, and disruptions in the genes encoding the OprD porin, thereby inhibiting uptake of carbapenems. In one isolate (ST17), the entire C terminus of OprD deviated from the expected amino acid sequence after amino acid G388. In the other (ST309), the entire oprD gene was interrupted by an ISPa1328 insertion element after amino acid D43, rendering this porin nonfunctional. The poor inhibition by REL of the GES ß-lactamases (GES-2, -19, and -20; apparent Ki of 19 ± 2 µM, 23 ± 2 µM, and 21 ± 2 µM, respectively) within the isolates also contributed to the observed IMI/REL-resistant phenotype. Modeling of REL binding to the active site of GES-20 suggested that the acylated REL is positioned in an unstable conformation as a result of a constrained Ω-loop.
Asunto(s)
Infecciones por Pseudomonas , Pseudomonas aeruginosa , Aminoácidos , Antibacterianos/farmacología , Antibacterianos/uso terapéutico , Compuestos de Azabiciclo/farmacología , Compuestos de Azabiciclo/uso terapéutico , Combinación de Medicamentos , Humanos , Imipenem/farmacología , Imipenem/uso terapéutico , Pruebas de Sensibilidad Microbiana , Porinas/genética , Infecciones por Pseudomonas/tratamiento farmacológico , Pseudomonas aeruginosa/genética , Pseudomonas aeruginosa/metabolismo , Estados Unidos , beta-Lactamasas/metabolismoRESUMEN
The development of new antimicrobial drugs is a priority to combat the increasing spread of multidrug-resistant bacteria. This development is especially problematic in gram-negative bacteria due to the outer membrane (OM) permeability barrier and multidrug efflux pumps. Therefore, we screened for compounds that target essential, nonredundant, surface-exposed processes in gram-negative bacteria. We identified a compound, MRL-494, that inhibits assembly of OM proteins (OMPs) by the ß-barrel assembly machine (BAM complex). The BAM complex contains one essential surface-exposed protein, BamA. We constructed a bamA mutagenesis library, screened for resistance to MRL-494, and identified the mutation bamAE470K BamAE470K restores OMP biogenesis in the presence of MRL-494. The mutant protein has both altered conformation and activity, suggesting it could either inhibit MRL-494 binding or allow BamA to function in the presence of MRL-494. By cellular thermal shift assay (CETSA), we determined that MRL-494 stabilizes BamA and BamAE470K from thermally induced aggregation, indicating direct or proximal binding to both BamA and BamAE470K Thus, it is the altered activity of BamAE470K responsible for resistance to MRL-494. Strikingly, MRL-494 possesses a second mechanism of action that kills gram-positive organisms. In microbes lacking an OM, MRL-494 lethally disrupts the cytoplasmic membrane. We suggest that the compound cannot disrupt the cytoplasmic membrane of gram-negative bacteria because it cannot penetrate the OM. Instead, MRL-494 inhibits OMP biogenesis from outside the OM by targeting BamA. The identification of a small molecule that inhibits OMP biogenesis at the cell surface represents a distinct class of antibacterial agents.
Asunto(s)
Antibacterianos/farmacología , Proteínas de la Membrana Bacteriana Externa/metabolismo , Proteínas de Escherichia coli/antagonistas & inhibidores , Escherichia coli/efectos de los fármacos , Multimerización de Proteína/efectos de los fármacos , Triazinas/farmacología , Proteínas de la Membrana Bacteriana Externa/antagonistas & inhibidores , Proteínas de la Membrana Bacteriana Externa/genética , Transporte Biológico/fisiología , Membrana Celular/efectos de los fármacos , Permeabilidad de la Membrana Celular/fisiología , Evaluación Preclínica de Medicamentos , Farmacorresistencia Bacteriana/genética , Escherichia coli/metabolismo , Proteínas de Escherichia coli/genética , Pruebas de Sensibilidad MicrobianaRESUMEN
Riboswitches are non-coding RNA structures located in messenger RNAs that bind endogenous ligands, such as a specific metabolite or ion, to regulate gene expression. As such, riboswitches serve as a novel, yet largely unexploited, class of emerging drug targets. Demonstrating this potential, however, has proven difficult and is restricted to structurally similar antimetabolites and semi-synthetic analogues of their cognate ligand, thus greatly restricting the chemical space and selectivity sought for such inhibitors. Here we report the discovery and characterization of ribocil, a highly selective chemical modulator of bacterial riboflavin riboswitches, which was identified in a phenotypic screen and acts as a structurally distinct synthetic mimic of the natural ligand, flavin mononucleotide, to repress riboswitch-mediated ribB gene expression and inhibit bacterial cell growth. Our findings indicate that non-coding RNA structural elements may be more broadly targeted by synthetic small molecules than previously expected.
Asunto(s)
Pirimidinas/química , Pirimidinas/farmacología , ARN Bacteriano/química , ARN Bacteriano/efectos de los fármacos , Riboswitch/efectos de los fármacos , Animales , Aptámeros de Nucleótidos/química , Bacterias/citología , Bacterias/efectos de los fármacos , Bacterias/crecimiento & desarrollo , Secuencia de Bases , Cristalografía por Rayos X , Infecciones por Escherichia coli/tratamiento farmacológico , Infecciones por Escherichia coli/microbiología , Proteínas de Escherichia coli/genética , Femenino , Mononucleótido de Flavina/metabolismo , Regulación Bacteriana de la Expresión Génica/efectos de los fármacos , Proteínas de Choque Térmico/genética , Transferasas Intramoleculares/genética , Ligandos , Ratones , Ratones Endogámicos DBA , Modelos Moleculares , Datos de Secuencia Molecular , Pirimidinas/aislamiento & purificación , Pirimidinas/uso terapéutico , ARN Bacteriano/genética , Reproducibilidad de los Resultados , Riboflavina/biosíntesis , Riboswitch/genética , Especificidad por SustratoRESUMEN
The outer membrane (OM) of Gram-negative bacteria forms a robust permeability barrier that blocks entry of toxins and antibiotics. Most OM proteins (OMPs) assume a ß-barrel fold, and some form aqueous channels for nutrient uptake and efflux of intracellular toxins. The Bam machine catalyzes rapid folding and assembly of OMPs. Fidelity of OMP biogenesis is monitored by the σE stress response. When OMP folding defects arise, the proteases DegS and RseP act sequentially to liberate σE into the cytosol, enabling it to activate transcription of the stress regulon. Here, we identify batimastat as a selective inhibitor of RseP that causes a lethal decrease in σE activity in Escherichia coli, and we further identify RseP mutants that are insensitive to inhibition and confer resistance. Remarkably, batimastat treatment allows the capture of elusive intermediates in the OMP biogenesis pathway and offers opportunities to better understand the underlying basis for σE essentiality.
Asunto(s)
Proteínas de la Membrana Bacteriana Externa , Endopeptidasas , Proteínas de Escherichia coli , Escherichia coli , Proteínas de la Membrana , Desplegamiento Proteico , Factores de Transcripción , Proteínas de la Membrana Bacteriana Externa/genética , Proteínas de la Membrana Bacteriana Externa/metabolismo , Endopeptidasas/genética , Endopeptidasas/metabolismo , Escherichia coli/genética , Escherichia coli/metabolismo , Proteínas de Escherichia coli/genética , Proteínas de Escherichia coli/metabolismo , Proteínas de la Membrana/genética , Proteínas de la Membrana/metabolismo , Factores de Transcripción/metabolismoRESUMEN
BACKGROUND: The prevalence of antibiotic resistance is increasing, and multidrug-resistant Pseudomonas aeruginosa has been identified as a serious threat to human health. The production of ß-lactamase is a key mechanism contributing to imipenem resistance in P. aeruginosa. Relebactam is a novel ß-lactamase inhibitor, active against class A and C ß-lactamases, that has been shown to restore imipenem susceptibility. In a series of studies, we assessed the interaction of relebactam with key mechanisms involved in carbapenem resistance in P. aeruginosa and to what extent relebactam might overcome imipenem non-susceptibility. RESULTS: Relebactam demonstrated no intrinsic antibacterial activity against P. aeruginosa, had no inoculum effect, and was not subject to efflux. Enzymology studies showed relebactam is a potent (overall inhibition constant: 27 nM), practically irreversible inhibitor of P. aeruginosa AmpC. Among P. aeruginosa clinical isolates from the SMART global surveillance program (2009, n = 993; 2011, n = 1702; 2015, n = 5953; 2016, n = 6165), imipenem susceptibility rates were 68.4% in 2009, 67.4% in 2011, 70.4% in 2015, and 67.3% in 2016. With the addition of 4 µg/mL relebactam, imipenem susceptibility rates increased to 87.6, 86.0, 91.7, and 89.8%, respectively. When all imipenem-non-susceptible isolates were pooled, the addition of 4 µg/mL relebactam reduced the mode imipenem minimum inhibitory concentration (MIC) 8-fold (from 16 µg/mL to 2 µg/mL) among all imipenem-non-susceptible isolates. Of 3747 imipenem-non-susceptible isolates that underwent molecular profiling, 1200 (32%) remained non-susceptible to the combination imipenem/relebactam (IMI/REL); 42% of these encoded class B metallo-ß-lactamases, 11% encoded a class A GES enzyme, and no class D enzymes were detected. No relationship was observed between alleles of the chromosomally-encoded P. aeruginosa AmpC and IMI/REL MIC. CONCLUSIONS: IMI/REL exhibited potential in the treatment of carbapenem-resistant P. aeruginosa infections, with the exception of isolates encoding class B, some GES alleles, and class D carbapenemases.
Asunto(s)
Compuestos de Azabiciclo/farmacología , Imipenem/farmacología , Pseudomonas aeruginosa/efectos de los fármacos , Antibacterianos/farmacología , Proteínas Bacterianas/efectos de los fármacos , Combinación de Medicamentos , Farmacorresistencia Bacteriana Múltiple/efectos de los fármacos , Humanos , Cinética , Pruebas de Sensibilidad Microbiana , Infecciones por Pseudomonas/microbiología , Pseudomonas aeruginosa/enzimología , beta-Lactamasas/efectos de los fármacosRESUMEN
ß-Lactamase inhibitors with a bicyclic urea core and a variety of heterocyclic side chains were prepared and evaluated as potential partners for combination with imipenem to overcome class A and C ß-lactamase mediated antibiotic resistance. The piperidine analog 3 (MK-7655) inhibited both class A and C ß-lactamases in vitro. It effectively restored imipenem's activity against imipenem-resistant Pseudomonas and Klebsiella strains at clinically achievable concentrations. A combination of MK-7655 and Primaxin® is currently in phase II clinical trials for the treatment of Gram-negative bacterial infections.
Asunto(s)
Compuestos de Azabiciclo/química , Compuestos de Azabiciclo/farmacología , Cilastatina/química , Descubrimiento de Drogas , Inhibidores Enzimáticos/química , Imipenem/química , Inhibidores de beta-Lactamasas , Cilastatina/farmacología , Combinación Cilastatina e Imipenem , Cristalografía por Rayos X , Combinación de Medicamentos , Farmacorresistencia Bacteriana/efectos de los fármacos , Imipenem/farmacología , Concentración 50 Inhibidora , Klebsiella/efectos de los fármacos , Pruebas de Sensibilidad Microbiana , Modelos Biológicos , Pseudomonas/efectos de los fármacos , Relación Estructura-ActividadRESUMEN
Carbapenem-resistant Acinetobacter baumannii infections have limited treatment options. Synthesis, transport and placement of lipopolysaccharide or lipooligosaccharide (LOS) in the outer membrane of Gram-negative bacteria are important for bacterial virulence and survival. Here we describe the cerastecins, inhibitors of the A. baumannii transporter MsbA, an LOS flippase. These molecules are potent and bactericidal against A. baumannii, including clinical carbapenem-resistant Acinetobacter baumannii isolates. Using cryo-electron microscopy and biochemical analysis, we show that the cerastecins adopt a serpentine configuration in the central vault of the MsbA dimer, stalling the enzyme and uncoupling ATP hydrolysis from substrate flipping. A derivative with optimized potency and pharmacokinetic properties showed efficacy in murine models of bloodstream or pulmonary A. baumannii infection. While resistance development is inevitable, targeting a clinically unexploited mechanism avoids existing antibiotic resistance mechanisms. Although clinical validation of LOS transport remains undetermined, the cerastecins may open a path to narrow-spectrum treatment modalities for important nosocomial infections.
Asunto(s)
Infecciones por Acinetobacter , Acinetobacter baumannii , Antibacterianos , Proteínas Bacterianas , Lipopolisacáridos , Acinetobacter baumannii/efectos de los fármacos , Acinetobacter baumannii/metabolismo , Lipopolisacáridos/metabolismo , Animales , Infecciones por Acinetobacter/microbiología , Infecciones por Acinetobacter/tratamiento farmacológico , Ratones , Antibacterianos/farmacología , Proteínas Bacterianas/metabolismo , Transporte Biológico , Pruebas de Sensibilidad Microbiana , Humanos , Microscopía por Crioelectrón , Carbapenémicos/farmacología , Carbapenémicos/metabolismo , Modelos Animales de Enfermedad , Femenino , Transportadoras de Casetes de Unión a ATPRESUMEN
Acinetobacter baumannii, a commonly multidrug-resistant Gram-negative bacterium responsible for large numbers of bloodstream and lung infections worldwide, is increasingly difficult to treat and constitutes a growing threat to human health. Structurally novel antibacterial chemical matter that can evade existing resistance mechanisms is essential for addressing this critical medical need. Herein, we describe our efforts to inhibit the essential A. baumannii lipooligosaccharide (LOS) ATP-binding cassette (ABC) transporter MsbA. An unexpected impurity from a phenotypic screening was optimized as a series of dimeric compounds, culminating with 1 (cerastecin D), which exhibited antibacterial activity in the presence of human serum and a pharmacokinetic profile sufficient to achieve efficacy against A. baumannii in murine septicemia and lung infection models.
Asunto(s)
Transportadoras de Casetes de Unión a ATP , Infecciones por Acinetobacter , Acinetobacter baumannii , Antibacterianos , Proteínas Bacterianas , Lipopolisacáridos , Acinetobacter baumannii/efectos de los fármacos , Acinetobacter baumannii/metabolismo , Antibacterianos/farmacología , Antibacterianos/química , Animales , Lipopolisacáridos/metabolismo , Lipopolisacáridos/antagonistas & inhibidores , Ratones , Humanos , Proteínas Bacterianas/antagonistas & inhibidores , Proteínas Bacterianas/metabolismo , Transportadoras de Casetes de Unión a ATP/antagonistas & inhibidores , Transportadoras de Casetes de Unión a ATP/metabolismo , Infecciones por Acinetobacter/tratamiento farmacológico , Infecciones por Acinetobacter/microbiología , Pruebas de Sensibilidad MicrobianaRESUMEN
The use of ß-lactam (BL) and ß-lactamase inhibitor combination to overcome BL antibiotic resistance has been validated through clinically approved drug products. However, unmet medical needs still exist for the treatment of infections caused by Gram-negative (GN) bacteria expressing metallo-ß-lactamases. Previously, we reported our effort to discover pan inhibitors of three main families in this class: IMP, VIM, and NDM. Herein, we describe our work to improve the GN coverage spectrum in combination with imipenem and relebactam. This was achieved through structure- and property-based optimization to tackle the GN cell penetration and efflux challenges. A significant discovery was made that inhibition of both VIM alleles, VIM-1 and VIM-2, is essential for broad GN coverage, especially against VIM-producing P. aeruginosa. In addition, pharmacokinetics and nonclinical safety profiles were investigated for select compounds. Key findings from this drug discovery campaign laid the foundation for further lead optimization toward identification of preclinical candidates.
Asunto(s)
Antibacterianos , Inhibidores de beta-Lactamasas , Humanos , Inhibidores de beta-Lactamasas/farmacología , Inhibidores de beta-Lactamasas/uso terapéutico , Inhibidores de beta-Lactamasas/química , Antibacterianos/química , Imipenem/farmacología , beta-Lactamasas , Bacterias Gramnegativas , Pruebas de Sensibilidad MicrobianaRESUMEN
The resistance of methicillin-resistant Staphylococcus aureus (MRSA) to all ß-lactam classes limits treatment options for serious infections involving this organism. Our goal is to discover new agents that restore the activity of ß-lactams against MRSA, an approach that has led to the discovery of two classes of natural product antibiotics, a cyclic depsipeptide (krisynomycin) and a lipoglycopeptide (actinocarbasin), which potentiate the activity of imipenem against MRSA strain COL. We report here that these imipenem synergists are inhibitors of the bacterial type I signal peptidase SpsB, a serine protease that is required for the secretion of proteins that are exported through the Sec and Tat systems. A synthetic derivative of actinocarbasin, M131, synergized with imipenem both in vitro and in vivo with potent efficacy. The in vitro activity of M131 extends to clinical isolates of MRSA but not to a methicillin-sensitive strain. Synergy is restricted to ß-lactam antibiotics and is not observed with other antibiotic classes. We propose that the SpsB inhibitors synergize with ß-lactams by preventing the signal peptidase-mediated secretion of proteins required for ß-lactam resistance. Combinations of SpsB inhibitors and ß-lactams may expand the utility of these widely prescribed antibiotics to treat MRSA infections, analogous to ß-lactamase inhibitors which restored the utility of this antibiotic class for the treatment of resistant Gram-negative infections.
Asunto(s)
Antibacterianos/farmacología , Proteínas Bacterianas/antagonistas & inhibidores , Compuestos de Bifenilo/farmacología , Depsipéptidos/farmacología , Glicopéptidos/farmacología , Glicósidos/farmacología , Lipopéptidos/farmacología , Proteínas de la Membrana/antagonistas & inhibidores , Staphylococcus aureus Resistente a Meticilina/efectos de los fármacos , Oligopéptidos/farmacología , Infecciones Estafilocócicas/tratamiento farmacológico , beta-Lactamas/farmacología , Animales , Antibacterianos/aislamiento & purificación , Proteínas Bacterianas/genética , Proteínas Bacterianas/metabolismo , Transporte Biológico , Compuestos de Bifenilo/síntesis química , Depsipéptidos/aislamiento & purificación , Sinergismo Farmacológico , Quimioterapia Combinada , Femenino , Glicopéptidos/síntesis química , Glicopéptidos/aislamiento & purificación , Glicósidos/aislamiento & purificación , Humanos , Lipopéptidos/aislamiento & purificación , Proteínas de la Membrana/genética , Proteínas de la Membrana/metabolismo , Staphylococcus aureus Resistente a Meticilina/genética , Staphylococcus aureus Resistente a Meticilina/crecimiento & desarrollo , Ratones , Ratones Endogámicos BALB C , Pruebas de Sensibilidad Microbiana , Familia de Multigenes , Oligopéptidos/síntesis química , Serina Endopeptidasas/genética , Serina Endopeptidasas/metabolismo , Infecciones Estafilocócicas/microbiología , Resistencia betalactámica/efectos de los fármacos , Resistencia betalactámica/genética , beta-Lactamasas/genética , beta-Lactamasas/metabolismoRESUMEN
Bacterial infection remains a serious threat to human lives because of emerging resistance to existing antibiotics. Although the scientific community has avidly pursued the discovery of new antibiotics that interact with new targets, these efforts have met with limited success since the early 1960s. Here we report the discovery of platensimycin, a previously unknown class of antibiotics produced by Streptomyces platensis. Platensimycin demonstrates strong, broad-spectrum Gram-positive antibacterial activity by selectively inhibiting cellular lipid biosynthesis. We show that this anti-bacterial effect is exerted through the selective targeting of beta-ketoacyl-(acyl-carrier-protein (ACP)) synthase I/II (FabF/B) in the synthetic pathway of fatty acids. Direct binding assays show that platensimycin interacts specifically with the acyl-enzyme intermediate of the target protein, and X-ray crystallographic studies reveal that a specific conformational change that occurs on acylation must take place before the inhibitor can bind. Treatment with platensimycin eradicates Staphylococcus aureus infection in mice. Because of its unique mode of action, platensimycin shows no cross-resistance to other key antibiotic-resistant strains tested, including methicillin-resistant S. aureus, vancomycin-intermediate S. aureus and vancomycin-resistant enterococci. Platensimycin is the most potent inhibitor reported for the FabF/B condensing enzymes, and is the only inhibitor of these targets that shows broad-spectrum activity, in vivo efficacy and no observed toxicity.
Asunto(s)
Aminoglicósidos/farmacología , Antibacterianos/farmacología , Proteínas Bacterianas/antagonistas & inhibidores , 3-Oxoacil-(Proteína Transportadora de Acil) Sintasa/antagonistas & inhibidores , 3-Oxoacil-(Proteína Transportadora de Acil) Sintasa/química , 3-Oxoacil-(Proteína Transportadora de Acil) Sintasa/metabolismo , Acetamidas/farmacología , Acetamidas/toxicidad , Adamantano , Aminobenzoatos , Aminoglicósidos/química , Aminoglicósidos/metabolismo , Aminoglicósidos/toxicidad , Anilidas , Animales , Antibacterianos/química , Antibacterianos/metabolismo , Antibacterianos/toxicidad , Apoproteínas/química , Apoproteínas/metabolismo , Proteínas Bacterianas/química , Proteínas Bacterianas/metabolismo , Cristalografía por Rayos X , Linezolid , Lípidos/biosíntesis , Ratones , Pruebas de Sensibilidad Microbiana , Modelos Moleculares , Conformación Molecular , Oxazolidinonas/farmacología , Oxazolidinonas/toxicidad , Streptomyces/metabolismo , Especificidad por SustratoRESUMEN
With the emergence and rapid spreading of NDM-1 and existence of clinically relevant VIM-1 and IMP-1, discovery of pan inhibitors targeting metallo-beta-lactamases (MBLs) became critical in our battle against bacterial infection. Concurrent with our fragment and high-throughput screenings, we performed a knowledge-based search of known metallo-beta-lactamase inhibitors (MBLIs) to identify starting points for early engagement of medicinal chemistry. A class of compounds exemplified by 11, discovered earlier as B. fragilis metallo-beta-lactamase inhibitors, was selected for in silico virtual screening. From these efforts, compound 12 was identified with activity against NDM-1 only. Initial exploration on metal binding design followed by structure-guided optimization led to the discovery of a series of compounds represented by 23 with a pan MBL inhibition profile. In in vivo studies, compound 23 in combination with imipenem (IPM) robustly lowered the bacterial burden in a murine infection model and became the lead for the invention of MBLI clinical candidates.
Asunto(s)
Infecciones Bacterianas , Inhibidores de beta-Lactamasas , Animales , Ratones , Inhibidores de beta-Lactamasas/farmacología , Inhibidores de beta-Lactamasas/uso terapéutico , Inhibidores de beta-Lactamasas/química , Imipenem/farmacología , Imipenem/uso terapéutico , beta-Lactamasas/metabolismo , Antibacterianos/farmacología , Antibacterianos/uso terapéutico , Antibacterianos/química , Pruebas de Sensibilidad MicrobianaRESUMEN
The bridged monobactam ß-lactamase inhibitor MK-8712 (1) effectively inhibits class C ß-lactamases. Side chain N-alkylated and ring-opened analogs of 1 were prepared and evaluated for combination with imipenem to overcome class C ß-lactamase mediated resistance. Although some analogs were more potent inhibitors of AmpC, none exhibited better synergy with imipenem than 1.
Asunto(s)
Antibacterianos/química , Inhibidores Enzimáticos/química , Monobactamas/síntesis química , Inhibidores de beta-Lactamasas , Antibacterianos/síntesis química , Antibacterianos/farmacología , Sitios de Unión , Simulación por Computador , Inhibidores Enzimáticos/síntesis química , Inhibidores Enzimáticos/farmacología , Imipenem/farmacología , Pruebas de Sensibilidad Microbiana , Monobactamas/farmacología , Estructura Terciaria de Proteína , Relación Estructura-Actividad , beta-Lactamasas/metabolismoRESUMEN
4,7-Dichloro-1-benzothien-2-yl sulfonylaminomethyl boronic acid (DSABA, Compound I) was discovered as the first boronic acid-based class D beta-lactamase inhibitor. It exhibited an IC(50) of 5.6 microM against OXA-40. The compound also inhibited class A and C beta-lactamases with sub to low microM IC(50), and synergized with imipenem against Acinetobacter baumannii.
Asunto(s)
Antibacterianos/farmacología , Ácidos Borónicos/farmacología , Inhibidores Enzimáticos/farmacología , Inhibidores de beta-Lactamasas , Acinetobacter baumannii/efectos de los fármacos , Antibacterianos/química , Ácidos Borónicos/química , Inhibidores Enzimáticos/química , Concentración 50 Inhibidora , Pruebas de Sensibilidad MicrobianaRESUMEN
Bridged monobactam beta-lactamase inhibitors were prepared and evaluated as potential partners for combination with imipenem to overcome class C beta-lactamase mediated resistance. The (S)-azepine analog 2 was found to be effective in both in vitro and in vivo assays and was selected for preclinical development.
Asunto(s)
Carbapenémicos/química , Descubrimiento de Drogas/métodos , Imipenem/química , Inhibidores de beta-Lactamasas , Animales , Compuestos Bicíclicos Heterocíclicos con Puentes/química , Compuestos Bicíclicos Heterocíclicos con Puentes/farmacología , Carbapenémicos/farmacología , Combinación de Medicamentos , Imipenem/farmacología , Ratones , Infecciones por Pseudomonas/tratamiento farmacológico , Infecciones por Pseudomonas/enzimología , Pseudomonas aeruginosa/efectos de los fármacos , Pseudomonas aeruginosa/fisiología , Relación Estructura-Actividad , Resistencia betalactámica/efectos de los fármacos , Resistencia betalactámica/fisiología , beta-Lactamasas/metabolismoRESUMEN
The growing prevalence of drug resistant bacteria is a significant global threat to human health. The antibacterial drug rifampin, which functions by inhibiting bacterial RNA polymerase (RNAP), is an important part of the antibacterial armamentarium. Here, in order to identify novel inhibitors of bacterial RNAP, we used affinity-selection mass spectrometry to screen a chemical library for compounds that bind to Escherichia coli RNAP. We identified a novel small molecule, MRL-436, that binds to RNAP, inhibits RNAP, and exhibits antibacterial activity. MRL-436 binds to RNAP through a binding site that differs from the rifampin binding site, inhibits rifampin-resistant RNAP derivatives, and exhibits antibacterial activity against rifampin-resistant strains. Isolation of mutants resistant to the antibacterial activity of MRL-436 yields a missense mutation in codon 622 of the rpoC gene encoding the RNAP ß' subunit or a null mutation in the rpoZ gene encoding the RNAP ω subunit, confirming that RNAP is the functional cellular target for the antibacterial activity of MRL-436, and indicating that RNAP ß' subunit residue 622 and the RNAP ω subunit are required for the antibacterial activity of MRL-436. Similarity between the resistance determinant for MRL-436 and the resistance determinant for the cellular alarmone ppGpp suggests a possible similarity in binding site and/or induced conformational state for MRL-436 and ppGpp.
Asunto(s)
Antibacterianos/farmacología , ARN Polimerasas Dirigidas por ADN/antagonistas & inhibidores , Farmacorresistencia Bacteriana/efectos de los fármacos , Sitios de Unión , Farmacorresistencia Bacteriana/genética , Inhibidores Enzimáticos/farmacología , Escherichia coli/enzimología , Espectrometría de Masas , Unión Proteica , Rifampin/farmacología , Bibliotecas de Moléculas PequeñasRESUMEN
To combat the threat of antibiotic-resistant Gram-negative bacteria, novel agents that circumvent established resistance mechanisms are urgently needed. Our approach was to focus first on identifying bioactive small molecules followed by chemical lead prioritization and target identification. Within this annotated library of bioactives, we identified a small molecule with activity against efflux-deficient Escherichia coli and other sensitized Gram-negatives. Further studies suggested that this compound inhibited DNA replication and selection for resistance identified mutations in a subunit of E. coli DNA gyrase, a type II topoisomerase. Our initial compound demonstrated weak inhibition of DNA gyrase activity while optimized compounds demonstrated significantly improved inhibition of E. coli and Pseudomonas aeruginosa DNA gyrase and caused cleaved complex stabilization, a hallmark of certain bactericidal DNA gyrase inhibitors. Amino acid substitutions conferring resistance to this new class of DNA gyrase inhibitors reside exclusively in the TOPRIM domain of GyrB and are not associated with resistance to the fluoroquinolones, suggesting a novel binding site for a gyrase inhibitor.
Asunto(s)
Antibacterianos/farmacología , Girasa de ADN/metabolismo , Inhibidores de Topoisomerasa II/farmacología , Farmacorresistencia Bacteriana/genética , Escherichia coli/efectos de los fármacos , Escherichia coli/enzimología , Fluoroquinolonas/farmacología , Pruebas de Sensibilidad Microbiana , Dominios Proteicos , Pseudomonas aeruginosa/efectos de los fármacos , Pseudomonas aeruginosa/enzimologíaRESUMEN
5'-Adenosine monophosphate-activated protein kinase (AMPK) is a master regulator of energy homeostasis in eukaryotes. Despite three decades of investigation, the biological roles of AMPK and its potential as a drug target remain incompletely understood, largely because of a lack of optimized pharmacological tools. We developed MK-8722, a potent, direct, allosteric activator of all 12 mammalian AMPK complexes. In rodents and rhesus monkeys, MK-8722-mediated AMPK activation in skeletal muscle induced robust, durable, insulin-independent glucose uptake and glycogen synthesis, with resultant improvements in glycemia and no evidence of hypoglycemia. These effects translated across species, including diabetic rhesus monkeys, but manifested with concomitant cardiac hypertrophy and increased cardiac glycogen without apparent functional sequelae.
Asunto(s)
Proteínas Quinasas Activadas por AMP/metabolismo , Cardiomegalia/inducido químicamente , Glucosa/metabolismo , Homeostasis/efectos de los fármacos , Imidazoles/farmacología , Piridinas/farmacología , Animales , Bencimidazoles , Glucemia/efectos de los fármacos , Ayuno , Glucógeno/metabolismo , Hipoglucemia/inducido químicamente , Imidazoles/efectos adversos , Imidazoles/química , Insulina/farmacología , Macaca mulatta , Masculino , Ratones , Ratones Endogámicos C57BL , Músculo Esquelético/efectos de los fármacos , Músculo Esquelético/metabolismo , Piridinas/efectos adversos , Piridinas/químicaRESUMEN
Resistance to existing classes of antibiotics drives the need for discovery of novel compounds with unique mechanisms of action. Nargenicin A1, a natural product with limited antibacterial spectrum, was rediscovered in a whole-cell antisense assay. Macromolecular labeling in both Staphylococcus aureus and an Escherichia coli tolC efflux mutant revealed selective inhibition of DNA replication not due to gyrase or topoisomerase IV inhibition. S. aureus nargenicin-resistant mutants were selected at a frequency of â¼1 × 10(-9), and whole-genome resequencing found a single base-pair change in the dnaE gene, a homolog of the E. coli holoenzyme α subunit. A DnaE single-enzyme assay was exquisitely sensitive to inhibition by nargenicin, and other in vitro characterization studies corroborated DnaE as the target. Medicinal chemistry efforts may expand the spectrum of this novel mechanism antibiotic.
Asunto(s)
ADN Polimerasa III/genética , Descubrimiento de Drogas , Antibacterianos/química , Antibacterianos/metabolismo , Antibacterianos/farmacología , Replicación del ADN/efectos de los fármacos , ADN Polimerasa Dirigida por ADN/metabolismo , Farmacorresistencia Bacteriana/genética , Escherichia coli/efectos de los fármacos , Concentración 50 Inhibidora , Lactonas/química , Lactonas/metabolismo , Lactonas/farmacología , Mutación , Inhibidores de la Síntesis del Ácido Nucleico/química , Inhibidores de la Síntesis del Ácido Nucleico/farmacología , Staphylococcus aureus/efectos de los fármacosRESUMEN
6-Anilinopyrazolo[3,4-d]pyrimidin-4-ones are novel dGTP analogues that inhibit the replication-specific enzyme DNA polymerase III (DNA pol III) of Staphlococcus aureus and other Gram-positive (Gr+) bacteria. To enhance the potential of these inhibitors as antimicrobial agents, a structure-activity relationship was developed involving substitutions at the 2, 4, and pyrazolo NH positions. All of the new inhibitors were tested for their ability to inhibit S. aureus DNA pol III and the growth of several other Gr+ bacteria in culture. 2-Anilino groups with small hydrophobic groups in the meta or para position enhanced both antipolymerase and antimicrobial activity. 2-Benzyl-substituted inhibitors were substantially less active. Substitution in the 4-position by oxygen gave the optimal activity, whereas substitution at the pyrazolo NH was not tolerated. These pyrazolo[3,4-d]pyrimidine derivatives represent a novel class of antimicrobials with promising activities against Gr+ bacteria.