RESUMEN
Macrolides and ketolides comprise a family of clinically important antibiotics that inhibit protein synthesis by binding within the exit tunnel of the bacterial ribosome. While these antibiotics are known to interrupt translation at specific sequence motifs, with ketolides predominantly stalling at Arg/Lys-X-Arg/Lys motifs and macrolides displaying a broader specificity, a structural basis for their context-specific action has been lacking. Here, we present structures of ribosomes arrested during the synthesis of an Arg-Leu-Arg sequence by the macrolide erythromycin (ERY) and the ketolide telithromycin (TEL). Together with deep mutagenesis and molecular dynamics simulations, the structures reveal how ERY and TEL interplay with the Arg-Leu-Arg motif to induce translational arrest and illuminate the basis for the less stringent sequence-specific action of ERY over TEL. Because programmed stalling at the Arg/Lys-X-Arg/Lys motifs is used to activate expression of antibiotic resistance genes, our study also provides important insights for future development of improved macrolide antibiotics.
Asunto(s)
Antibacterianos/farmacología , Cetólidos/farmacología , Macrólidos/farmacología , Inhibidores de la Síntesis de la Proteína/farmacología , Secuencias de Aminoácidos , Secuencia de Aminoácidos , Antibacterianos/química , Bacillus subtilis/efectos de los fármacos , Bacillus subtilis/enzimología , Bacillus subtilis/genética , Sitios de Unión/genética , Microscopía por Crioelectrón , Farmacorresistencia Microbiana/genética , Eritromicina/química , Eritromicina/farmacología , Genes Bacterianos , Cetólidos/química , Cetólidos/farmacocinética , Macrólidos/química , Metiltransferasas/química , Metiltransferasas/genética , Metiltransferasas/metabolismo , Simulación de Dinámica Molecular , Mutagénesis Insercional , Biosíntesis de Proteínas/efectos de los fármacos , Inhibidores de la Síntesis de la Proteína/química , Ribosomas/efectos de los fármacosRESUMEN
PURPOSE: The preclinical pharmacokinetic and pharmacodynamic properties of a potent fluoroketolide RBx14255 against Streptococcus pneumoniae and Haemophilus influenzae was compared with telithromycin and human clinical dose was predicted for preclinical development. METHODS: The in vitro pharmacokinetic characterization was performed for solubility, Caco-2 permeability, microsomal stability, CYP inhibition and plasma protein binding. In vivo pharmacokinetic studies were performed in Swiss albino mice, Sprague Dawley rats and Beagle dogs. The pharmacodynamic studies were carried out in mouse against S. pneumoniae in systemic infection and against S. pneumoniae and H. influenzae in rat lung infection models. RESULTS: RBx14255 showed superior potency and efficacy in mouse and rat infection models. RBx14255 showed pH dependent solubility (0.41 mg/mL at pH 6.8 and >1 mg/mL at pH 1.2), moderate Caco-2 permeability (A to B: 12 nm/s) with high efflux ratio. It showed high plasma protein binding (>97%) in mouse and low binding (45- 70%) in rat, dog and human. The compound is mainly metabolized through CYP3A4. Pharmacokinetic parameters and absolute bioavailability of both, RBx14255 and telithromycin are similar in mouse. Both the ketolides showed low plasma clearance (18% of the normal hepatic blood flow rate) in mouse, moderate to high clearance in rat and dog. Mean oral bioavailability was high in mouse (≥85%), moderate in rat (RBx14255: 15% and telithromycin: 51%) and high to moderate in dog (RBx14255: 98% and telithromycin: 56%). The predicted efficacious dose for a 70 kg man ranges from 124 mg BID to 226 mg BID. CONCLUSION: RBx14255 displayed significantly better pharmacodynamics which correlates with the pharmacokinetic properties against S. pneumoniae and H. influenzae as compared to telithromycin. The predicted human efficacious doses are in the range of 124-226 mg, making it amenable to oral dosage form drug in human. This could be a promising clinical candidate for future studies.
Asunto(s)
Antibacterianos/farmacología , Farmacorresistencia Bacteriana Múltiple/efectos de los fármacos , Haemophilus influenzae/efectos de los fármacos , Cetólidos/farmacología , Streptococcus pneumoniae/efectos de los fármacos , Animales , Antibacterianos/química , Perros , Humanos , Cetólidos/química , Masculino , Ratones , Pruebas de Sensibilidad Microbiana , Microsomas Hepáticos/química , Microsomas Hepáticos/metabolismo , Estructura Molecular , Ratas , Ratas Sprague-DawleyRESUMEN
Macrolide antibiotics bind to the exit tunnel of the ribosome and inhibit protein synthesis blocking its translocation. Thus, antibiotics including the known macrolide Erythromycin (ERY) are active against bacteria. However, at present, some bacteria show resistance to drugs, which requires the development of new powerful antibacterial agents. One possible way is to use the ERY structure, but change its side chains, while the size of the lactone ring can remain unchanged or change. In this work we consider Cethromycin (CET) and Solithromycin (SOL), which are ketolides with quinolylallyl group at C6 and aminophenyl at C11, respectively (both of them have the same lactone ring as ERY). Experiments have shown that these ketolides have improved efficacy against pathogens, but their binding affinity to the E. coli's ribosome is almost identical. To clarify this issue, we have studied in detail the binding mechanisms of ERY, CET and SOL using the docking and molecular dynamic simulations. In agreement with the experiments, we showed that these compounds have similar binding affinities. Desosamine and lactone ring groups play a critical role in the binding of ERY to the ribosome. In CET and SOL, the contribution of keto and alkylaryl groups is balanced by cyclic carbamate. We have demonstrated that increased fluctuations in the ribosomal residues at the binding site led to an increase in the entropic term in the free binding energy of ERY compared to SOL and CET. The alkyl-aryl arm of both ketolides strongly interacts with A752 and U2609. In addition, the presence of macrolides in the exit tunnel can alter the conformation of U2585, which is located in the peptidyl transferase center, through non-bonded interaction. Therefore, the side chain of ketolides affects not only the binding site but also other residues possibly leading to a strong effect on the protein synthesis process. We predict that to combat bacterial mutations, it is necessary either to design a bulk and charged group as a cladinose, or to use several groups with different signs of charges. This prediction can be used for the development of new efficient antibiotics.
Asunto(s)
Eritromicina/química , Eritromicina/metabolismo , Escherichia coli/metabolismo , Cetólidos/química , Cetólidos/metabolismo , Macrólidos/química , Macrólidos/metabolismo , Simulación de Dinámica Molecular , Ribosomas/metabolismo , Triazoles/química , Triazoles/metabolismo , Sitios de Unión , Entropía , Enlace de Hidrógeno , Metilación , Simulación del Acoplamiento Molecular , Electricidad Estática , Termodinámica , Factores de TiempoRESUMEN
BACKGROUND: RBx 14255 is a fluoroketolide in pre-clinical evaluation with potent activity against MDR Gram-positive pathogens. OBJECTIVES: To investigate the efficacy of RBx 14255 against bacterial meningitis caused by Streptococcus pneumoniae, Neisseria meningitidis or Haemophilus influenzae in an experimental murine meningitis model. METHODS: In vitro activity of RBx 14255 was evaluated against clinical isolates of S. pneumoniae, N. meningitidis and H. influenzae. The in vivo efficacy of RBx 14255 was evaluated against bacterial meningitis, induced with S. pneumoniae 3579 erm(B), S. pneumoniae MA 80 erm(B), N. meningitidis 1852 and H. influenzae B1414 in a murine meningitis model. RESULTS: RBx 14255 showed strong in vitro bactericidal potential against S. pneumoniae, N. meningitidis and H. influenzae with MIC ranges of 0.004-0.1, 0.03-0.5 and 1-4 mg/L, respectively. In a murine meningitis model, a 50 mg/kg dose of RBx 14255, q12h, resulted in significant reduction of bacterial counts in the brain compared with the pretreatment control. The concentration of RBx 14255 in brain tissue correlated well with the efficacy in this mouse model. CONCLUSIONS: RBx 14255 showed superior bactericidal activity in time-kill assays in vitro and in vivo in an experimental murine meningitis model. RBx 14255 could be a promising candidate for future drug development against bacterial meningitis.
Asunto(s)
Antibacterianos/farmacología , Haemophilus influenzae/efectos de los fármacos , Cetólidos/farmacología , Neisseria meningitidis/efectos de los fármacos , Streptococcus pneumoniae/efectos de los fármacos , Animales , Antibacterianos/química , Modelos Animales de Enfermedad , Infecciones por Haemophilus/tratamiento farmacológico , Infecciones por Haemophilus/microbiología , Cetólidos/química , Meningitis Meningocócica/tratamiento farmacológico , Meningitis Meningocócica/microbiología , Meningitis Meningocócica/patología , Ratones , Pruebas de Sensibilidad Microbiana , Neumonía Neumocócica/tratamiento farmacológico , Neumonía Neumocócica/microbiología , Neumonía Neumocócica/patologíaRESUMEN
The clinical impact of drug-drug interactions based on time-dependent inhibition of cytochrome P450 (CYP) 3A4 has often been overpredicted, likely due to use of improper inhibitor concentration estimates at the enzyme. Here, we investigated if use of cytosolic unbound inhibitor concentrations could improve predictions of time-dependent drug-drug interactions. First, we assessed the inhibitory effects of ten time-dependent CYP3A inhibitors on midazolam 1'-hydroxylation in human liver microsomes. Then, using a novel method, we determined the cytosolic bioavailability of the inhibitors in human hepatocytes, and used the obtained values to calculate their concentrations at the active site of the enzyme, i.e. the cytosolic unbound concentrations. Finally, we combined the data in mechanistic static predictions, by considering different combinations of inhibitor concentrations in intestine and liver, including hepatic concentrations corrected for cytosolic bioavailability. The results were then compared to clinical data. Compared to no correction, correction for cytosolic bioavailability resulted in higher accuracy and precision, generally in line with those obtained by more demanding modelling. The best predictions were obtained when the inhibition of hepatic CYP3A was based on unbound maximal inhibitor concentrations corrected for cytosolic bioavailability. Our findings suggest that cytosolic unbound inhibitor concentrations improves predictions of time-dependent drug-drug interactions for CYP3A.
Asunto(s)
Citosol/química , Interacciones Farmacológicas/fisiología , Preparaciones Farmacéuticas/metabolismo , Citocromo P-450 CYP3A/química , Citocromo P-450 CYP3A/metabolismo , Inhibidores del Citocromo P-450 CYP3A/química , Inhibidores del Citocromo P-450 CYP3A/metabolismo , Citosol/metabolismo , Humanos , Cetólidos/química , Cetólidos/metabolismo , Cinética , Microsomas Hepáticos/química , Microsomas Hepáticos/enzimología , Microsomas Hepáticos/metabolismo , Preparaciones Farmacéuticas/química , Piperazinas/química , Piperazinas/metabolismo , Triazoles/química , Triazoles/metabolismoRESUMEN
Constitutively erythromycin-resistant apathogens are more difficult to address than inducibly resistant and efflux-resistant strains. Three series of the 4th generation 2-fluoro 9-oxime erythromycin ketolides were synthesized and evaluated. Incorporation of substituted heteroaryl groups (a - m), in contrast to previously reported the unsubstituted heteroaryl groups, proved to the beneficial for enhancement of the activities of the 9-propgargyl ketolide 8 series and the 9-allyl ketolide 14 series. But these aryl groups (a - m) cannot supply the resulting compounds 8 and 14, unlike corresponding the 6-allyl ketolide 20 series, with activity against constitutively resistant Streptococcus pneumoniae. However, hybrids of macrolides and quinolones (8, 14 and 20, Arâ¯=â¯n - t) exhibited not only high activities against susceptible, inducibly erm-mediated resistant, and efflux-mediated resistant strains, but also significantly improved potencies against constitutively resistant Streptococcus pneumoniae and Streptococcus pyogenes. The capacity was highlighted by introduction of newly designed carbamoyl quinolones (q, r, s and t) rather than commonly seen carboxy quinolones (o and p) as the pharmacophores. Structure-activity relationships and molecular modelling indicated that 8r, 14r and 20q may have different binding sites compared to current erythromycins. Moreover, 8r, 14r and 20q have 2.5-3.6 times prolonged half-life and 2.3- to 2.6-fold longer mean residence time in vivo over telithromycin. These findings pave the way for rational design of novel non-telithromycin macrolides that target new binding sites within bacterial ribosomes.
Asunto(s)
Antibacterianos/farmacología , Cetólidos/farmacología , Oximas/farmacología , Quinolonas/farmacología , Streptococcus pneumoniae/efectos de los fármacos , Streptococcus pyogenes/efectos de los fármacos , Antibacterianos/síntesis química , Antibacterianos/química , Relación Dosis-Respuesta a Droga , Diseño de Fármacos , Farmacorresistencia Bacteriana/efectos de los fármacos , Cetólidos/síntesis química , Cetólidos/química , Pruebas de Sensibilidad Microbiana , Estructura Molecular , Oximas/síntesis química , Oximas/química , Quinolonas/síntesis química , Quinolonas/química , Relación Estructura-ActividadRESUMEN
A series of novel 5-O-(4',6'-O-dimodified)-mycaminose 14-membered ketolides were assessed for their in vitro antibacterial activities against a panel of sensitive and resistant pathogens. Compound 1 and compound 2, two ester analogs, showed the best antibacterial activities against several macrolide-sensitive and macrolide-resistant strains. These results indicated that introducing ester to 6-OH and a small volume ether substituent to the 4-OH of mycaminose could improve the antibacterial activities of ketolides.
Asunto(s)
Antibacterianos/química , Antibacterianos/farmacología , Cetólidos/química , Cetólidos/farmacología , Bacterias/efectos de los fármacos , Estructura MolecularRESUMEN
A series of quinoylalkyl side chains was designed and synthesized, followed by introduction into ketolides by coupling with building block 6 or 32. The corresponding targets 7a-n, 33b, and 33e were tested for their in vitro activities against a series of macrolide-sensitive and macrolide-resistant pathogens. Some of them showed a similar antibacterial spectrum and comparable activity to telithromycin. Among them, two C2-F ketolides, compounds 33b and 33e, displayed excellent activities against macrolide-sensitive and macrolide-resistant pathogens.
Asunto(s)
Antibacterianos/farmacología , Haemophilus influenzae/efectos de los fármacos , Cetólidos/farmacología , Quinolinas/farmacología , Staphylococcus/efectos de los fármacos , Antibacterianos/síntesis química , Antibacterianos/química , Azitromicina/farmacología , Relación Dosis-Respuesta a Droga , Farmacorresistencia Bacteriana , Cetólidos/síntesis química , Cetólidos/química , Resistencia a la Meticilina , Pruebas de Sensibilidad Microbiana , Estructura Molecular , Quinolinas/química , Relación Estructura-ActividadRESUMEN
The nafithromycin concentrations in the plasma, epithelial lining fluid (ELF), and alveolar macrophages (AM) of 37 healthy adult subjects were measured following repeated dosing of oral nafithromycin at 800 mg once daily for 3 days. The values of noncompartmental pharmacokinetic (PK) parameters were determined from serial plasma samples collected over a 24-h interval following the first and third oral doses. Each subject underwent one standardized bronchoscopy with bronchoalveolar lavage (BAL) at 3, 6, 9, 12, 24, or 48 h after the third dose of nafithromycin. The mean ± standard deviation values of the plasma PK parameters after the first and third doses included maximum plasma concentrations (Cmax) of 1.02 ± 0.31 µg/ml and 1.39 ± 0.36 µg/ml, respectively; times to Cmax of 3.97 ± 1.30 h and 3.69 ± 1.28 h, respectively; clearances of 67.3 ± 21.3 liters/h and 52.4 ± 18.5 liters/h, respectively, and elimination half-lives of 7.7 ± 1.1 h and 9.1 ± 1.7 h, respectively. The values of the area under the plasma concentration-time curve (AUC) from time zero to 24 h postdosing (AUC0-24) for nafithromycin based on the mean or median total plasma concentrations at BAL fluid sampling times were 16.2 µg · h/ml. For ELF, the respective AUC0-24 values based on the mean and median concentrations were 224.1 and 176.3 µg · h/ml, whereas for AM, the respective AUC0-24 values were 8,538 and 5,894 µg · h/ml. Penetration ratios based on ELF and total plasma AUC0-24 values based on the mean and median concentrations were 13.8 and 10.9, respectively, whereas the ratios of the AM to total plasma concentrations based on the mean and median concentrations were 527 and 364, respectively. The sustained ELF and AM concentrations for 48 h after the third dose suggest that nafithromycin has the potential to be a useful agent for the treatment of lower respiratory tract infections. (This study has been registered at ClinicalTrials.gov under registration no. NCT02453529.).
Asunto(s)
Antibacterianos/sangre , Antibacterianos/farmacocinética , Líquido del Lavado Bronquioalveolar/química , Cetólidos/sangre , Cetólidos/farmacocinética , Lactonas/farmacología , Neumonía Bacteriana/tratamiento farmacológico , Adulto , Antibacterianos/efectos adversos , Lavado Broncoalveolar , Broncoscopía , Chlamydophila pneumoniae/efectos de los fármacos , Femenino , Haemophilus influenzae/efectos de los fármacos , Voluntarios Sanos , Humanos , Cetólidos/química , Cetólidos/farmacología , Lactonas/química , Legionella pneumophila/efectos de los fármacos , Macrófagos Alveolares/citología , Masculino , Persona de Mediana Edad , Moraxella catarrhalis/efectos de los fármacos , Mycoplasma pneumoniae/efectos de los fármacos , Neumonía Bacteriana/microbiología , Alveolos Pulmonares/química , Staphylococcus aureus/efectos de los fármacos , Streptococcus pneumoniae/efectos de los fármacos , Adulto JovenRESUMEN
A series of novel 11-O-carbamoyl clarithromycin ketolides were designed, synthesized and evaluated for their in vitro antibacterial activity. The results showed that the majority of the target compounds displayed improved activity compared with references against erythromycin-resistant S. pneumoniae A22072 expressing the mef gene, S. pneumoniae B1 expressing the erm gene and S. pneumoniae AB11 expressing the mef and erm genes. In particular, compounds 9, 18, 19 and 22 showed the most potent activity against erythromycin-resistant S. pneumoniae A22072 with the MIC values of 0.5µg/mL. Furthermore, compounds 11, 18, 19, 24 and 29 were also found to exhibit favorable antibacterial activity against erythromycin-susceptible S. pyogenes with the MIC values of 0.125-1µg/mL, and moderate activity against erythromycin-susceptible S. aureus ATCC25923 and B. subtilis ATCC9372.
Asunto(s)
Antibacterianos/síntesis química , Claritromicina/síntesis química , Cetólidos/química , Antibacterianos/química , Antibacterianos/farmacología , Proteínas Bacterianas/genética , Proteínas Bacterianas/metabolismo , Claritromicina/análogos & derivados , Claritromicina/farmacología , Farmacorresistencia Bacteriana/efectos de los fármacos , Eritromicina/farmacología , Bacterias Gramnegativas/efectos de los fármacos , Bacterias Grampositivas/efectos de los fármacos , Proteínas de la Membrana/genética , Proteínas de la Membrana/metabolismo , Metiltransferasas/genética , Metiltransferasas/metabolismo , Pruebas de Sensibilidad Microbiana , Streptococcus pneumoniae/efectos de los fármacos , Streptococcus pyogenes/efectos de los fármacos , Relación Estructura-ActividadRESUMEN
Macrolides, one of the most prescribed classes of antibiotics, bind in the bacterial ribosome's polypeptide exit tunnel and inhibit translation. However, mutations and other ribosomal modifications, especially to the base A2058 of the 23S rRNA, have led to a growing resistance problem. Here, we have used molecular dynamics simulations to study the macrolides erythromycin and azithromycin in wild-type, A2058G-mutated, and singly or doubly A2058-methylated Escherichia coli ribosomes. We find that the ribosomal modifications result in less favorable interactions between the base 2058 and the desosamine sugar of the macrolides, as well as greater displacement of the macrolides from their crystal structure position, illuminating the causes of resistance. We have also examined four azithromycin derivatives containing aromatic indole-analog moieties, which were previously designed based on simulations of the stalling peptide SecM in the ribosome. Surprisingly, we found that the studied moieties could adopt very different geometries when interacting with a key base in the tunnel, A751, possibly explaining their distinct activities. Based on our simulations, we propose modifications to the indole-analog moieties that should increase their interactions with A751 and, consequently, enhance the potency of future azithromycin derivatives.
Asunto(s)
Antibacterianos/química , Antibacterianos/farmacología , Diseño de Fármacos , Escherichia coli/efectos de los fármacos , Macrólidos/química , Macrólidos/farmacología , Azitromicina/análogos & derivados , Azitromicina/química , Azitromicina/farmacología , Farmacorresistencia Bacteriana , Eritromicina/química , Eritromicina/farmacología , Escherichia coli/genética , Infecciones por Escherichia coli/tratamiento farmacológico , Infecciones por Escherichia coli/microbiología , Humanos , Cetólidos/química , Cetólidos/farmacología , Simulación de Dinámica Molecular , Mutación Puntual/efectos de los fármacos , Ribosomas/efectos de los fármacos , Ribosomas/genéticaRESUMEN
Erythromycin was long viewed as a bacteriostatic agent. The erythromycin derivatives, 9-oxime ketolides have a species-specific bactericidal profile. Among them, the 3'-allyl version of the 9-oxime ketolide 1 (Ar=3-quinolyl; 17a) is bactericidal against Streptococcus pneumoniae and Streptococcus pyogenes. In contrast, the 2-fluoro analogs of 1, 13a (Ar=6-quinolyl), 13b (Ar=3-quinolyl) and 24a (Ar=4-isoquinolyl), show bactericidal activities against S. pneumoniae, Staphylococcus aureus and Moraxella catarrhalis, while the 2-fluoro analogs 13c (Ar=3-aminopyridyl) and 24b (Ar=3-carbamoylpyridyl) are only bactericidal against S. pneumoniae and Haemophilus influenzae. Reduction of the ketolides led to novel epiacylides, the 3-O-epimers of the acylides. Alteration of linker length (30b vs. 30a), 2-fluorination (33 vs. 30a) and incorporation of additional spacers at the 9-oxime or 6-OH (35, 40 vs. 30a) did not restore the epiacylides back to be as active as the acylide 31. Molecular docking suggested that epimerization at the 3-position reshapes the orientation of the 3-O-sidechain and leads to considerably weaker binding with bacterial ribosomes.
Asunto(s)
Antibacterianos/farmacología , Cetólidos/farmacología , Oximas/farmacología , Antibacterianos/síntesis química , Antibacterianos/química , Bacterias Gramnegativas/efectos de los fármacos , Bacterias Grampositivas/efectos de los fármacos , Cetólidos/síntesis química , Cetólidos/química , Simulación del Acoplamiento Molecular , Oximas/síntesis química , Oximas/química , Ribosomas/química , Estereoisomerismo , Relación Estructura-ActividadRESUMEN
Chemoselective substitutions in the C10-methyl group of erythromycin A ketolides is reported. The C10-methyl group in the clarithromycin derived substrate 10,11-anhydro-O6-methyl-descladinosylerythromycin was activated by conversion into an allyl acetate and thereafter to the corresponding allylic cyanide. Both the allylic acetate and the cyanide reacted with carbonyldiimidazole and ammonia to afford a C11,C12-cyclic carbamate with concurrent elimination of the allylic function to yield a methylene α,ß-unsaturated ketone. Conjugate addition with amines resulted in stereoselective C-N bond formation between the terminal methylene carbon and the amino nitrogen. Carbylation in the methylene group was effected under Stille conditions for cross-coupling with Pd-catalysis. With anion stabilized nucleophiles, such as a sodium salt of a malonate, stereoselectivity was observed in the formation of the 10-substituent. Stereoselective cycloaddition with trimethylsilyldiazomethane afforded a spirane where the C10 carbon of the macrolide skeleton had become a quaternary spirocarbon. Antibacterial in vitro data for a selected group of compounds against strains of respiratory pathogens S. pneumoniae and S. aureus are reported. Most of the compounds tested showed improved activities over CLA as a reference compound against efflux resistant S. pneumoniae as well as against efflux and inducibly resistant strains of S. aureus.
Asunto(s)
Antibacterianos/síntesis química , Claritromicina/síntesis química , Cetólidos/síntesis química , Antibacterianos/química , Antibacterianos/farmacología , Espectroscopía de Resonancia Magnética con Carbono-13 , Claritromicina/química , Claritromicina/farmacología , Cetólidos/química , Pruebas de Sensibilidad Microbiana , Espectroscopía de Protones por Resonancia Magnética , Espectrometría de Masa por Ionización de Electrospray , Staphylococcus aureus/efectos de los fármacos , Streptococcus pneumoniae/efectos de los fármacos , Relación Estructura-ActividadRESUMEN
The chemical modification of structurally complex fermentation products, a process known as semisynthesis, has been an important tool in the discovery and manufacture of antibiotics for the treatment of various infectious diseases. However, many of the therapeutics obtained in this way are no longer effective, because bacterial resistance to these compounds has developed. Here we present a practical, fully synthetic route to macrolide antibiotics by the convergent assembly of simple chemical building blocks, enabling the synthesis of diverse structures not accessible by traditional semisynthetic approaches. More than 300 new macrolide antibiotic candidates, as well as the clinical candidate solithromycin, have been synthesized using our convergent approach. Evaluation of these compounds against a panel of pathogenic bacteria revealed that the majority of these structures had antibiotic activity, some efficacious against strains resistant to macrolides in current use. The chemistry we describe here provides a platform for the discovery of new macrolide antibiotics and may also serve as the basis for their manufacture.
Asunto(s)
Antibacterianos/síntesis química , Antibacterianos/farmacología , Descubrimiento de Drogas/métodos , Macrólidos/síntesis química , Macrólidos/farmacología , Amino Azúcares/síntesis química , Amino Azúcares/química , Amino Azúcares/farmacología , Antibacterianos/química , Bacterias/efectos de los fármacos , Humanos , Cetólidos/síntesis química , Cetólidos/química , Macrólidos/química , Pruebas de Sensibilidad Microbiana , Estructura Molecular , Bibliotecas de Moléculas Pequeñas/síntesis química , Bibliotecas de Moléculas Pequeñas/química , Triazoles/síntesis química , Triazoles/química , Triazoles/farmacologíaRESUMEN
Ketolides belong to the latest generation of macrolides and are not only effective against macrolide susceptible bacterial strains but also against some macrolide resistant strains. Here we present data providing insights into the mechanism of action of K-1602, a novel alkyl-aryl-bearing fluoroketolide. According to our data, the K-1602 interacts with the ribosome as a one-step slow binding inhibitor, displaying an association rate constant equal to 0.28 × 10(4) M(-1) s(-1) and a dissociation rate constant equal to 0.0025 min(-1). Both constants contribute to produce an overall inhibition constant Ki equal to 1.49 × 10(-8) M, which correlates very well with the superior activity of this compound when compared with many other ketolides or fluoroketolides.
Asunto(s)
Cetólidos/química , Cetólidos/farmacología , Ribosomas/efectos de los fármacos , Unión Competitiva , Farmacorresistencia Bacteriana/efectos de los fármacos , Escherichia coli/efectos de los fármacos , Cinética , Puromicina/química , Proteínas Ribosómicas/química , Proteínas Ribosómicas/metabolismo , Tilosina/química , Tilosina/farmacologíaRESUMEN
A subset of Gram-negative bacterial pathogens uses a type III secretion system (T3SS) to open up a conduit into eukaryotic cells in order to inject effector proteins. These modulate pathways to enhance bacterial colonization. In this study, we screened established bioactive compounds for any that could repress T3SS expression in enterohemorrhagic Escherichia coli (EHEC) O157. The ketolides telithromycin and, subsequently, solithromycin both demonstrated repressive effects on expression of the bacterial T3SS at sub-MICs, leading to significant reductions in bacterial binding and actin-rich pedestal formation on epithelial cells. Preincubation of epithelial cells with solithromycin resulted in significantly less attachment of E. coli O157. Moreover, bacteria expressing the T3SS were more susceptible to solithromycin, and there was significant preferential killing of E. coli O157 bacteria when they were added to epithelial cells that had been preexposed to the ketolide. This killing was dependent on expression of the T3SS. Taken together, this research indicates that the ketolide that has accumulated in epithelial cells may traffic back into the bacteria via the T3SS. Considering that neither ketolide induces the SOS response, nontoxic members of this class of antibiotics, such as solithromycin, should be considered for future testing and trials evaluating their use for treatment of EHEC infections. These antibiotics may also have broader significance for treating infections caused by other pathogenic bacteria, including intracellular bacteria, that express a T3SS.
Asunto(s)
Antibacterianos/farmacología , Escherichia coli O157/efectos de los fármacos , Cetólidos/farmacología , Macrólidos/farmacología , Bibliotecas de Moléculas Pequeñas/farmacología , Triazoles/farmacología , Sistemas de Secreción Tipo III/antagonistas & inhibidores , Animales , Antibacterianos/química , Adhesión Bacteriana/efectos de los fármacos , Células CACO-2 , Bovinos , Línea Celular , Descubrimiento de Drogas , Células Epiteliales/efectos de los fármacos , Células Epiteliales/microbiología , Escherichia coli O157/genética , Escherichia coli O157/metabolismo , Expresión Génica , Ensayos Analíticos de Alto Rendimiento , Humanos , Cetólidos/química , Macrólidos/química , Pruebas de Sensibilidad Microbiana , Mucosa Respiratoria/efectos de los fármacos , Mucosa Respiratoria/microbiología , Triazoles/química , Sistemas de Secreción Tipo III/genética , Sistemas de Secreción Tipo III/metabolismoRESUMEN
9-Oxime acylides have different SAR and binding modes from 9-oxime ketolides. An aminopyridyl or carbamoylpyridyl group anchored at the end of the 9-oxime 2-propargyl group is beneficial for antimicrobial activity. Both the 2-pyridyl and 3-pyridyl groups derived from 3-OH have stacking interactions with the base pair G2505/C2610 (Escherichia coli numbering) of the bacterial rRNA. Compounds 3 presented characteristic features that belong to bactericidal agents when used against constitutive-erm resistant Staphylococcus aureus, susceptible and mef-encoded Streptococcus pneumoniae, inducible-erm resistant Streptococcus pyogenes, and Moraxella catarrhalis. A docking model indicated that the carbamoylpyridyl group of 3h may hydrogen bond to G2061 in addition to π-π stacking over the adenine of A2062 that proved to gate the tunnel for the egress of the nascent peptide. This study suggests that the 9-oxime acylides possess a bactericidal mechanism that is different from the traditional near-complete inhibition of protein synthesis. These studies provide a foundation for the rational design of macrolide antibiotics.
Asunto(s)
Antibacterianos/síntesis química , Oximas/química , Antibacterianos/química , Antibacterianos/farmacología , Sitios de Unión , Farmacorresistencia Bacteriana/efectos de los fármacos , Eritromicina/química , Haemophilus influenzae/efectos de los fármacos , Enlace de Hidrógeno , Cetólidos/química , Cetólidos/farmacología , Staphylococcus aureus Resistente a Meticilina/efectos de los fármacos , Pruebas de Sensibilidad Microbiana , Simulación del Acoplamiento Molecular , Subunidades Ribosómicas Grandes Bacterianas/química , Subunidades Ribosómicas Grandes Bacterianas/metabolismo , Staphylococcus aureus/efectos de los fármacos , Streptococcus pyogenes/efectos de los fármacos , Relación Estructura-ActividadRESUMEN
Adenine at position 752 in a loop of helix 35 from positions 745 to 752 in domain II of 23S rRNA is involved in binding to the ribosome of telithromycin (TEL), a member of ketolides. Methylation of guanine at position 748 by the intrinsic methyltransferase RlmA(II) enhances binding of telithromycin (TEL) to A752 in Streptococcus pneumoniae. We have found that another intrinsic methylation of the adjacent uridine at position 747 enhances G748 methylation by RlmA(II), rendering TEL susceptibility. U747 and another nucleotide, U1939, were methylated by the dual-specific methyltransferase RlmCD encoded by SP_1029 in S. pneumoniae. Inactivation of RlmCD reduced N1-methylated level of G748 by RlmA(II) in vivo, leading to TEL resistance when the nucleotide A2058, located in domain V of 23S rRNA, was dimethylated by the dimethyltransferase Erm(B). In vitro methylation of rRNA showed that RlmA(II) activity was significantly enhanced by RlmCD-mediated pre-methylation of 23S rRNA. These results suggest that RlmCD-mediated U747 methylation promotes efficient G748 methylation by RlmA(II), thereby facilitating TEL binding to the ribosome.
Asunto(s)
Antibacterianos/farmacología , Proteínas Bacterianas/metabolismo , Cetólidos/farmacología , Metiltransferasas/metabolismo , ARN Ribosómico 23S/metabolismo , Streptococcus pneumoniae/enzimología , Antibacterianos/química , Farmacorresistencia Bacteriana , Guanina/metabolismo , Cetólidos/química , Metilación , ARN Ribosómico 23S/química , Streptococcus pneumoniae/efectos de los fármacos , Streptococcus pneumoniae/genética , Uridina/metabolismoRESUMEN
Macrolides are an important class of antibiotics that target the bacterial ribosome. Computer simulations of macrolides are limited as specific force field parameters have not been previously developed for them. Here, we determine CHARMM-compatible force field parameters for erythromycin, azithromycin, and telithromycin, using the force field toolkit (ffTK) plugin in VMD. Because of their large size, novel approaches for parametrizing them had to be developed. Two methods for determining partial atomic charges, from interactions with TIP3P water and from the electrostatic potential, as well as several approaches for fitting the dihedral parameters were tested. The performance of the different parameter sets was evaluated by molecular dynamics simulations of the macrolides in ribosome, with a distinct improvement in maintenance of key interactions observed after refinement of the initial parameters. Based on the results of the macrolide tests, recommended procedures for parametrizing very large molecules using ffTK are given.
Asunto(s)
Antibacterianos/química , Azitromicina/química , Eritromicina/química , Cetólidos/química , Macrólidos/química , Ribosomas/química , Algoritmos , Amino Azúcares/química , Sitios de Unión , Escherichia coli/química , Escherichia coli/metabolismo , Hexosas/química , Simulación de Dinámica Molecular , Electricidad Estática , Termodinámica , Thermus thermophilus/química , Thermus thermophilus/metabolismo , Agua/químicaRESUMEN
Without quantum theory any understanding of molecular interactions is incomplete. In principal, chemistry, and even biology, can be fully derived from non-relativistic quantum mechanics. In practice, conventional quantum chemical calculations are computationally too intensive and time consuming to be useful for drug discovery on more than a limited basis. A previously described, original, quantum-based computational process for drug discovery and design bridges this gap between theory and practice, and allows the application of quantum methods to large-scale in silico identification of active compounds. Here, we show the results of this quantum-similarity approach applied to the discovery of novel liver-stage antimalarials. Testing of only five of the model-predicted compounds in vitro and in vivo hepatic stage drug inhibition assays with P. berghei identified four novel chemical structures representing three separate quantum classes of liver-stage antimalarials. All four compounds inhibited liver-stage Plasmodium as a single oral dose in the quantitative PCR mouse liver-stage sporozoites-challenge model. One of the newly identified compounds, cethromycin [ABT-773], a macrolide-quinoline hybrid, is a drug with an extensive (over 5,000 people) safety profile warranting its exploitation as a new weapon for the current effort of malaria eradication. The results of our molecular modeling exceed current state-of-the-art computational methods. Drug discovery through quantum similarity is data-driven, agnostic to any particular target or disease process that can evaluate multiple phenotypic, target-specific, or co-crystal structural data. This allows the incorporation of additional pharmacological requirements, as well as rapid exploration of novel chemical spaces for therapeutic applications.