RESUMEN
Antibiotics that inhibit multiple bacterial targets offer a promising therapeutic strategy against resistance evolution, but developing such antibiotics is challenging. Here we demonstrate that a rational design of balanced multitargeting antibiotics is feasible by using a medicinal chemistry workflow. The resultant lead compounds, ULD1 and ULD2, belonging to a novel chemical class, almost equipotently inhibit bacterial DNA gyrase and topoisomerase IV complexes and interact with multiple evolutionary conserved amino acids in the ATP-binding pockets of their target proteins. ULD1 and ULD2 are excellently potent against a broad range of gram-positive bacteria. Notably, the efficacy of these compounds was tested against a broad panel of multidrug-resistant Staphylococcus aureus clinical strains. Antibiotics with clinical relevance against staphylococcal infections fail to inhibit a significant fraction of these isolates, whereas both ULD1 and ULD2 inhibit all of them (minimum inhibitory concentration [MIC] ≤1 µg/mL). Resistance mutations against these compounds are rare, have limited impact on compound susceptibility, and substantially reduce bacterial growth. Based on their efficacy and lack of toxicity demonstrated in murine infection models, these compounds could translate into new therapies against multidrug-resistant bacterial infections.
Asunto(s)
Antibacterianos/farmacología , Diseño de Fármacos , Farmacorresistencia Bacteriana Múltiple/efectos de los fármacos , Secuencia de Aminoácidos , Animales , Antibacterianos/uso terapéutico , Proteínas Bacterianas/química , Proteínas Bacterianas/genética , Evolución Molecular Dirigida , Modelos Animales de Enfermedad , Inhibidores Enzimáticos/farmacología , Células Hep G2 , Humanos , Concentración de Iones de Hidrógeno , Células MCF-7 , Pruebas de Sensibilidad Microbiana , Mutación/genética , Piel/efectos de los fármacos , Piel/microbiología , Infecciones Estafilocócicas/tratamiento farmacológico , Staphylococcus aureus/efectos de los fármacos , Pruebas de ToxicidadRESUMEN
Bacterial DNA gyrase is an important target for the development of novel antibacterial drugs, which are urgently needed because of high level of antibiotic resistance worldwide. We designed and synthesized new 4,5,6,7-tetrahydrobenzo[d]thiazole-based DNA gyrase B inhibitors and their conjugates with siderophore mimics, which were introduced to increase the uptake of inhibitors into the bacterial cytoplasm. The most potent conjugate 34 had an IC50 of 58 nM against Escherichia coli DNA gyrase and displayed MIC of 14 µg/mL against E. coli ΔtolC strain. Only minor improvements in the antibacterial activities against wild-type E. coli in low-iron conditions were seen for DNA gyrase inhibitor - siderophore mimic conjugates.
Asunto(s)
Diseño de Fármacos , Imitación Molecular , Sideróforos/farmacología , Tiazoles/química , Inhibidores de Topoisomerasa II/farmacología , Antibacterianos/farmacología , Bacterias/efectos de los fármacos , Pruebas de Sensibilidad MicrobianaRESUMEN
Human DNA topoisomerase II is one of the major targets in anticancer therapy, however ATP-competitive inhibitors of this target have not yet reached their full potential. ATPase domain of human DNA topoisomerase II belongs to the GHKL ATPase superfamily and shares a very high 3D structural similarity with other superfamily members, including bacterial topoisomerases. In this work we report the discovery of a new chemotype of ATP-competitive inhibitors of human DNA topoisomerase IIα that were discovered through screening of in-house library of ATP-competitive inhibitors of bacterial DNA gyrase and topoisomerase IV. Systematic screening of this library provided us with 20 hit compounds. 1,2,4-Substituted N-phenylpyrrolamides were selected for a further exploration which resulted in 13 new analogues, including 52 with potent activity in relaxation assay (IC50 = 3.2 µM) and ATPase assay (IC50 = 0.43 µM). Cytotoxic activity of all hits was determined in MCF-7 cancer cell line and the most potent compounds, 16 and 20, showed an IC50 value of 8.7 and 8.2 µM, respectively.
Asunto(s)
Adenosina Trifosfatasas/metabolismo , Antineoplásicos/uso terapéutico , ADN-Topoisomerasas de Tipo II/química , Inhibidores de Topoisomerasa II/uso terapéutico , Antineoplásicos/farmacología , Humanos , Simulación del Acoplamiento Molecular , Inhibidores de Topoisomerasa II/farmacologíaRESUMEN
d-Amino acid oxidase (DAAO) inhibitors are typically small polar compounds with often suboptimal pharmacokinetic properties. Features of the native binding site limit the operational freedom of further medicinal chemistry efforts. We therefore initiated a structure based virtual screening campaign based on the X-ray structures of DAAO complexes where larger ligands shifted the loop (lid opening) covering the native binding site. The virtual screening of our in-house collection followed by the in vitro test of the best ranked compounds led to the identification of a new scaffold with micromolar IC50. Subsequent SAR explorations enabled us to identify submicromolar inhibitors. Docking studies supported by in vitro activity measurements suggest that compounds bind to the active site with a salt-bridge characteristic to DAAO inhibitor binding. In addition, displacement of and interaction with the loop covering the active site contributes significantly to the activity of the most potent compounds.
Asunto(s)
Amidas/farmacología , D-Aminoácido Oxidasa/antagonistas & inhibidores , Descubrimiento de Drogas , Inhibidores Enzimáticos/farmacología , Bibliotecas de Moléculas Pequeñas/farmacología , Amidas/síntesis química , Amidas/química , Dominio Catalítico/efectos de los fármacos , D-Aminoácido Oxidasa/metabolismo , Relación Dosis-Respuesta a Droga , Evaluación Preclínica de Medicamentos , Inhibidores Enzimáticos/síntesis química , Inhibidores Enzimáticos/química , Humanos , Ligandos , Estructura Molecular , Conformación Proteica , Bibliotecas de Moléculas Pequeñas/síntesis química , Bibliotecas de Moléculas Pequeñas/química , Relación Estructura-ActividadRESUMEN
ATP-competitive inhibitors of human DNA topoisomerase II show potential for becoming the successors of topoisomerase II poisons, the clinically successful anticancer drugs. Based on our recent screening hits, we designed, synthesized and biologically evaluated new, improved series of N-phenylpyrrolamide DNA topoisomerase II inhibitors. Six structural classes were prepared to systematically explore the chemical space of N-phenylpyrrolamide based inhibitors. The most potent inhibitor, 47d, had an IC50 value of 0.67 µM against DNA topoisomerase IIα. Compound 53b showed exceptional activity on cancer cell lines with IC50 values of 130 nM against HepG2 and 140 nM against MCF-7 cancer cell lines. The reported compounds have no structurally similarity to published structures, they are metabolically stable, have reasonable solubility and thus can serve as promising leads in the development of anticancer ATP-competitive inhibitors of human DNA topoisomerase IIα.
Asunto(s)
Antineoplásicos , Humanos , Antineoplásicos/química , Inhibidores de Topoisomerasa II/química , ADN-Topoisomerasas de Tipo II/metabolismo , Adenosina Trifosfato/metabolismo , Antígenos de Neoplasias/metabolismoRESUMEN
A new series of dual low nanomolar benzothiazole inhibitors of bacterial DNA gyrase and topoisomerase IV were developed. The resulting compounds show excellent broad-spectrum antibacterial activities against Gram-positive Enterococcus faecalis, Enterococcus faecium and multidrug resistant (MDR) Staphylococcus aureus strains [best compound minimal inhibitory concentrations (MICs): range, <0.03125-0.25 µg/mL] and against the Gram-negatives Acinetobacter baumannii and Klebsiella pneumoniae (best compound MICs: range, 1-4 µg/mL). Lead compound 7a was identified with favorable solubility and plasma protein binding, good metabolic stability, selectivity for bacterial topoisomerases, and no toxicity issues. The crystal structure of 7a in complex with Pseudomonas aeruginosa GyrB24 revealed its binding mode at the ATP-binding site. Expanded profiling of 7a and 7h showed potent antibacterial activity against over 100 MDR and non-MDR strains of A. baumannii and several other Gram-positive and Gram-negative strains. Ultimately, in vivo efficacy of 7a in a mouse model of vancomycin-intermediate S. aureus thigh infection was also demonstrated.
Asunto(s)
Staphylococcus aureus , Staphylococcus aureus Resistente a Vancomicina , Animales , Ratones , Staphylococcus aureus/metabolismo , Antibacterianos/farmacología , Antibacterianos/uso terapéutico , Antibacterianos/química , Girasa de ADN/metabolismo , Topoisomerasa de ADN IV , Pruebas de Sensibilidad MicrobianaRESUMEN
We have developed compounds with a promising activity against Acinetobacter baumannii and Pseudomonas aeruginosa, which are both on the WHO priority list of antibiotic-resistant bacteria. Starting from DNA gyrase inhibitor 1, we identified compound 27, featuring a 10-fold improved aqueous solubility, a 10-fold improved inhibition of topoisomerase IV from A. baumannii and P. aeruginosa, a 10-fold decreased inhibition of human topoisomerase IIα, and no cross-resistance to novobiocin. Cocrystal structures of 1 in complex with Escherichia coli GyrB24 and (S)-27 in complex with A. baumannii GyrB23 and P. aeruginosa GyrB24 revealed their binding to the ATP-binding pocket of the GyrB subunit. In further optimization steps, solubility, plasma free fraction, and other ADME properties of 27 were improved by fine-tuning of lipophilicity. In particular, analogs of 27 with retained anti-Gram-negative activity and improved plasma free fraction were identified. The series was found to be nongenotoxic, nonmutagenic, devoid of mitochondrial toxicity, and possessed no ion channel liabilities.
Asunto(s)
Acinetobacter baumannii , Inhibidores de Topoisomerasa II , Humanos , Inhibidores de Topoisomerasa II/farmacología , Inhibidores de Topoisomerasa II/química , Pseudomonas aeruginosa/metabolismo , Acinetobacter baumannii/metabolismo , Antibacterianos/farmacología , Antibacterianos/química , Escherichia coli/metabolismo , Benzotiazoles , Pruebas de Sensibilidad Microbiana , Girasa de ADN/metabolismoRESUMEN
DNA gyrase is an important target for the development of novel antibiotics. Although ATP-competitive DNA gyrase (GyrB) inhibitors are a well-studied class of antibacterial agents, there is currently no representative used in therapy, largely due to unwanted off-target activities. Selectivity of GyrB inhibitors against closely related human ATP-binding enzymes should be evaluated early in development to avoid off-target binding to homologous binding domains. To address this challenge, we developed selective 3D-pharmacophore models for GyrB, human topoisomerase IIα (TopoII), and the Hsp90 N-terminal domain (NTD) to be used in in silico activity profiling paradigms to identify molecules selective for GyrB over TopoII and Hsp90, as starting points for hit expansion and lead optimization. The models were used to profile highly active GyrB, TopoII, and Hsp90 inhibitors. Selected compounds were tested in in vitro assays. GyrB inhibitors 1 and 2 were inactive against TopoII and Hsp90, while 3 and 4, potent Hsp90 inhibitors, displayed no inhibition of GyrB and TopoII, and TopoII inhibitors 5 and 6 were inactive at GyrB and Hsp90. The results provide a proof of concept for the use of target activity profiling methods to identify selective starting points for hit and lead identification.
RESUMEN
The rise in multidrug-resistant bacteria defines the need for identification of new antibacterial agents that are less prone to resistance acquisition. Compounds that simultaneously inhibit multiple bacterial targets are more likely to suppress the evolution of target-based resistance than monotargeting compounds. The structurally similar ATP binding sites of DNA gyrase and topoisomerase â £ offer an opportunity to accomplish this goal. Here we present the design and structure-activity relationship analysis of balanced, low nanomolar inhibitors of bacterial DNA gyrase and topoisomerase IV that show potent antibacterial activities against the ESKAPE pathogens. For inhibitor 31c, a crystal structure in complex with Staphylococcus aureus DNA gyrase B was obtained that confirms the mode of action of these compounds. The best inhibitor, 31h, does not show any in vitro cytotoxicity and has excellent potency against Gram-positive (MICs: range, 0.0078-0.0625 µg/mL) and Gram-negative pathogens (MICs: range, 1-2 µg/mL). Furthermore, 31h inhibits GyrB mutants that can develop resistance to other drugs. Based on these data, we expect that structural derivatives of 31h will represent a step toward clinically efficacious multitargeting antimicrobials that are not impacted by existing antimicrobial resistance.
Asunto(s)
Adenosina Trifosfato/farmacología , Antibacterianos/farmacología , Girasa de ADN/metabolismo , Topoisomerasa de ADN IV/antagonistas & inhibidores , Escherichia coli/efectos de los fármacos , Staphylococcus aureus/efectos de los fármacos , Adenosina Trifosfato/síntesis química , Adenosina Trifosfato/química , Antibacterianos/síntesis química , Antibacterianos/química , Cristalografía por Rayos X , Topoisomerasa de ADN IV/metabolismo , Relación Dosis-Respuesta a Droga , Escherichia coli/enzimología , Escherichia coli/patogenicidad , Pruebas de Sensibilidad Microbiana , Simulación del Acoplamiento Molecular , Estructura Molecular , Staphylococcus aureus/enzimología , Staphylococcus aureus/patogenicidad , Relación Estructura-ActividadRESUMEN
Human DNA topoisomerase II is an important target in anticancer therapy. Despite the clinical success of drugs that target topoisomerase II, the development of resistant cancer cells can limit their clinical efficacy. To maximize the therapeutic potential of anticancer drugs, combination therapies and multitarget drugs have been suggested in many studies, where the use of multitarget drugs is advantageous from a pharmacokinetic point of view. There are various different options for the preparation of dual-target or multiple-target inhibitors, as topoisomerase II is both structurally (e.g., topoisomerase I, Hsp90, and kinases) and functionally (e.g., histone deacetylases and proteasome) connected to many validated anticancer targets. In this Perspective, we discuss the scientific background behind targeting topoisomerase II together with a number of other targets important in cancer therapy, review the present status, and discuss further options in the field.
Asunto(s)
Antineoplásicos/uso terapéutico , ADN-Topoisomerasas de Tipo II/metabolismo , Neoplasias/tratamiento farmacológico , Inhibidores de Topoisomerasa II/uso terapéutico , Animales , Antineoplásicos/farmacología , Línea Celular Tumoral , Diseño de Fármacos , Proteínas HSP90 de Choque Térmico/antagonistas & inhibidores , Humanos , Inhibidores de Topoisomerasa II/farmacología , Moduladores de Tubulina/farmacología , Moduladores de Tubulina/uso terapéuticoRESUMEN
A series of eleven 9-acridinyl amino acid derivatives were synthesized using a two-step procedure. Cytotoxicity was tested on the K562 and A549 cancer cell lines and normal diploid cell line MRC5 using the MTT assay. Compounds 6, 7, 8 and 9 were the most active, with IC50 values comparable to or lower than that of chemotherapeutic agent amsacrine. 8 and 9 were especially effective in the A549 cell line (IC50 ≈ 6 µM), which is of special interest since amsacrine is not sufficiently active in lung cancer patients. Cell cycle analysis revealed that 7 and 9 caused G2/M block, amsacrine caused arrest in the S phase, while 6 and 8 induced apoptotic cell death independently of the cell cycle regulation. In comparison to amsacrine, 6, 7, 8, and 9 showed similar inhibitory potential towards topoisomerase II, whereas only 7 showed DNA intercalation properties. In contrast to amsacrine, 6, 7, 8 and 9 showed a lack of toxicity towards unstimulated normal human leucocytes.
RESUMEN
The discovery of multi-targeting ligands of bacterial enzymes is an important strategy to combat rapidly spreading antimicrobial resistance. Bacterial DNA gyrase and topoisomerase IV are validated targets for the development of antibiotics. They can be inhibited at their catalytic sites or at their ATP binding sites. Here we present the design of new hybrids between the catalytic inhibitor ciprofloxacin and ATP-competitive inhibitors that show low nanomolar inhibition of DNA gyrase and antibacterial activity against Gram-negative pathogens. The most potent hybrid 3a has MICs of 0.5 µg/mL against Klebsiella pneumoniae, 4 µg/mL against Enterobacter cloacae, and 2 µg/mL against Escherichia coli. In addition, inhibition of mutant E. coli strains shows that these hybrid inhibitors interact with both subunits of DNA gyrase (GyrA, GyrB), and that binding to both of these sites contributes to their antibacterial activity.
RESUMEN
The emergence of multidrug-resistant bacteria is a global health threat necessitating the discovery of new antibacterials and novel strategies for fighting bacterial infections. We report first-in-class DNA gyrase B (GyrB) inhibitor/ciprofloxacin hybrids that display antibacterial activity against Escherichia coli. Whereas DNA gyrase ATPase inhibition experiments, DNA gyrase supercoiling assays, and inâ vitro antibacterial assays suggest binding of the hybrids to the E. coli GyrA and GyrB subunits, an interaction with the GyrA fluoroquinolone-binding site seems to be solely responsible for their antibacterial activity. Our results provide a foundation for a new concept of facilitating entry of nonpermeating GyrB inhibitors into bacteria by conjugation with ciprofloxacin, a highly permeable GyrA inhibitor. A hybrid molecule containing GyrA and GyrB inhibitor parts entering the bacterial cell would then elicit a strong antibacterial effect by inhibition of both the GyrA and GyrB subunits of DNA gyrase and potentially slow bacterial resistance development.
Asunto(s)
Antibacterianos/farmacología , Girasa de ADN/metabolismo , Escherichia coli/efectos de los fármacos , Escherichia coli/enzimología , Inhibidores de Topoisomerasa II/farmacología , Antibacterianos/química , Relación Dosis-Respuesta a Droga , Pruebas de Sensibilidad Microbiana , Estructura Molecular , Relación Estructura-Actividad , Inhibidores de Topoisomerasa II/químicaRESUMEN
We designed and synthesized a series of inhibitors of the bacterial enzymes DNA gyrase and DNA topoisomerase IV, based on our recently published benzothiazole-based inhibitor bearing an oxalyl moiety. To improve the antibacterial activity and retain potent enzymatic activity, we systematically explored the chemical space. Several strategies of modification were followed: varying substituents on the pyrrole carboxamide moiety, alteration of the central scaffold, including variation of substitution position and, most importantly, modification of the oxalyl moiety. Compounds with acidic, basic, and neutral properties were synthesized. To understand the mechanism of action and binding mode, we have obtained a crystal structure of compound 16a, bearing a primary amino group, in complex with the N-terminal domain of E. coli gyrase B (24 kDa) (PDB: 6YD9). Compound 15a, with a low molecular weight of 383 Da, potent inhibitory activity on E. coli gyrase (IC50 = 9.5 nM), potent antibacterial activity on E. faecalis (MIC = 3.13 µM), and efflux impaired E. coli strain (MIC = 0.78 µM), is an important contribution for the development of novel gyrase and topoisomerase IV inhibitors in Gram-negative bacteria.
RESUMEN
Aim: DNA gyrase and topoisomerase IV are essential bacterial enzymes, and in the fight against bacterial resistance, they are important targets for the development of novel antibacterial drugs. Results: Building from our first generation of 4,5,6,7-tetrahydrobenzo[d]thiazole-based DNA gyrase inhibitors, we designed and prepared an optimized series of analogs that show improved inhibition of DNA gyrase and topoisomerase IV from Staphylococcus aureus and Escherichia coli, with IC50 values in the nanomolar range. Importantly, these inhibitors also show improved antibacterial activity against Gram-positive strains. Conclusion: The most promising inhibitor, 29, is active against Enterococcus faecalis, Enterococcus faecium and S. aureus wild-type and resistant strains, with minimum inhibitory concentrations between 4 and 8 µg/ml, which represents good starting point for development of novel antibacterials.
Asunto(s)
Antibacterianos/farmacología , Benzotiazoles/farmacología , Girasa de ADN/metabolismo , Bacterias Grampositivas/efectos de los fármacos , Inhibidores de Topoisomerasa II/farmacología , Antibacterianos/química , Benzotiazoles/química , Relación Dosis-Respuesta a Droga , Bacterias Grampositivas/enzimología , Bacterias Grampositivas/crecimiento & desarrollo , Humanos , Pruebas de Sensibilidad Microbiana , Modelos Moleculares , Estructura Molecular , Relación Estructura-Actividad , Inhibidores de Topoisomerasa II/químicaRESUMEN
A series of novel fluoroquinolone-Safirinium dye hybrids was synthesized by means of tandem Mannich-electrophilic amination reactions from profluorophoric isoxazolones and antibiotics bearing a secondary amino group at position 7 of the quinoline ring. The obtained fluorescent spiro fused conjugates incorporating quaternary nitrogen atoms were characterized by 1H NMR, IR, MS, and elemental analysis. All the synthetic analogues (3a-h and 4a-h) were evaluated for their in vitro antimicrobial, bactericidal, and antibiofilm activities against a panel of Gram positive and Gram-negative pathogenic bacteria. The most active Safirinium Q derivatives of lomefloxacin (4d) and ciprofloxacin (4e) exhibited molar-based antibacterial activities comparable to the unmodified drugs and displayed considerable inhibitory potencies in E. coli DNA gyrase supercoiling assays with IC50 values in the low micromolar range. Zwiterionic hybrids were noticeably less lipophilic than the parent quinolones in micellar electrokinetic chromatography (MECK) experiments. The tests performed in the presence of phenylalanine-arginine ß-naphthylamide (PAßN) or carbonyl cyanide m-chlorophenylhydrazone (CCCP) revealed that the conjugates are to some extent subject to bacterial efflux and cellular accumulation, respectively. Moreover, the hybrids did not exhibit notable cytotoxicity towards the HEK 293 control cell line and demonstrated low propensity for resistance development, as exemplified for compounds 3g and 4b. Finally, molecular docking experiments revealed that the synthesized compounds were able to bind in the fluoroquinolone-binding mode at S. aureus DNA gyrase and S. pneumoniae topoisomerase IV active sites.
Asunto(s)
Antibacterianos/farmacología , Inhibidores Enzimáticos/farmacología , Bacterias Gramnegativas/efectos de los fármacos , Bacterias Grampositivas/efectos de los fármacos , Compuestos de Amonio Cuaternario/farmacología , Quinolonas/farmacología , Antibacterianos/síntesis química , Antibacterianos/química , Girasa de ADN/metabolismo , Topoisomerasa de ADN IV/antagonistas & inhibidores , Topoisomerasa de ADN IV/metabolismo , Relación Dosis-Respuesta a Droga , Inhibidores Enzimáticos/síntesis química , Inhibidores Enzimáticos/química , Bacterias Gramnegativas/metabolismo , Bacterias Grampositivas/metabolismo , Células HEK293 , Humanos , Pruebas de Sensibilidad Microbiana , Estructura Molecular , Compuestos de Amonio Cuaternario/síntesis química , Compuestos de Amonio Cuaternario/química , Quinolonas/química , Relación Estructura-ActividadRESUMEN
ATP competitive inhibitors of DNA gyrase and topoisomerase IV have great therapeutic potential, but none of the described synthetic compounds has so far reached the market. To optimise the activities and physicochemical properties of our previously reported N-phenylpyrrolamide inhibitors, we have synthesized an improved, chemically variegated selection of compounds and evaluated them against DNA gyrase and topoisomerase IV enzymes, and against selected Gram-positive and Gram-negative bacteria. The most potent compound displayed IC50 values of 6.9â¯nM against Escherichia coli DNA gyrase and 960â¯nM against Staphylococcus aureus topoisomerase IV. Several compounds displayed minimum inhibitory concentrations (MICs) against Gram-positive strains in the 1-50⯵M range, one of which inhibited the growth of Enterococcus faecalis, Enterococcus faecium, S. aureus and Streptococcus pyogenes with MIC values of 1.56⯵M, 1.56⯵M, 0.78⯵M and 0.72⯵M, respectively. This compound has been investigated further on methicillin-resistant S. aureus (MRSA) and on ciprofloxacin non-susceptible and extremely drug resistant strain of S. aureus (MRSA VISA). It exhibited the MIC value of 2.5⯵M on both strains, and MIC value of 32⯵M against MRSA in the presence of inactivated human blood serum. Further studies are needed to confirm its mode of action.
Asunto(s)
Antibacterianos/química , Topoisomerasa de ADN IV/antagonistas & inhibidores , Pirrolidinas/química , Inhibidores de Topoisomerasa II/farmacología , Amidas/química , Antibacterianos/farmacología , Girasa de ADN/efectos de los fármacos , Bacterias Gramnegativas/efectos de los fármacos , Bacterias Grampositivas/efectos de los fármacos , Humanos , Staphylococcus aureus Resistente a Meticilina/efectos de los fármacos , Pruebas de Sensibilidad Microbiana , Inhibidores de Topoisomerasa II/químicaRESUMEN
The ATP binding site located on the subunit B of DNA gyrase is an attractive target for the development of new antibacterial agents. In recent decades, several small-molecule inhibitor classes have been discovered but none has so far reached the market. We present here the discovery of a promising new series of N-phenylpyrrolamides with low nanomolar IC50 values against DNA gyrase, and submicromolar IC50 values against topoisomerase IV from Escherichia coli and Staphylococcus aureus. The most potent compound in the series has an IC50 value of 13â¯nM against E. coli gyrase. Minimum inhibitory concentrations (MICs) against Gram-positive bacteria are in the low micromolar range. The oxadiazolone derivative 11a, with an IC50 value of 85â¯nM against E. coli DNA gyrase displays the most potent antibacterial activity, with MIC values of 1.56⯵M against Enterococcus faecalis, and 3.13⯵M against wild type S. aureus, methicillin-resistant S. aureus (MRSA) and vancomycin-resistant Enterococcus (VRE). The activity against wild type E. coli in the presence of efflux pump inhibitor phenylalanine-arginine ß-naphthylamide (PAßN) is 4.6⯵M.