RESUMO
Bacterial enoyl-ACP reductase (FabI) catalyzes the final step in each cycle of bacterial fatty acid biosynthesis and is an attractive target for the development of new antibacterial agents. Our efforts to identify potent, selective FabI inhibitors began with screening of the GlaxoSmithKline proprietary compound collection, which identified several small-molecule inhibitors of Staphylococcus aureus FabI. Through a combination of iterative medicinal chemistry and X-ray crystal structure based design, one of these leads was developed into the novel aminopyridine derivative 9, a low micromolar inhibitor of FabI from S. aureus (IC(50) = 2.4 microM) and Haemophilus influenzae (IC(50) = 4.2 microM). Compound 9 has good in vitro antibacterial activity against several organisms, including S. aureus (MIC = 0.5 microg/mL), and is effective in vivo in a S. aureus groin abscess infection model in rats. Through FabI overexpressor and macromolecular synthesis studies, the mode of action of 9 has been confirmed to be inhibition of fatty acid biosynthesis via inhibition of FabI. Taken together, these results support FabI as a valid antibacterial target and demonstrate the potential of small-molecule FabI inhibitors for the treatment of bacterial infections.
Assuntos
Acrilamidas/síntese química , Aminopiridinas/síntese química , Antibacterianos/síntese química , Inibidores Enzimáticos/síntese química , Ácido Graxo Sintases/antagonistas & inibidores , Oxirredutases/antagonistas & inibidores , Acrilamidas/química , Acrilamidas/farmacologia , Aminopiridinas/química , Aminopiridinas/farmacologia , Animais , Antibacterianos/química , Antibacterianos/farmacologia , Cristalografia por Raios X , Bases de Dados Factuais , Enoil-(Proteína de Transporte de Acila) Redutase (NADH) , Inibidores Enzimáticos/química , Inibidores Enzimáticos/farmacologia , Ácido Graxo Sintases/química , Haemophilus influenzae/efeitos dos fármacos , Concentração Inibidora 50 , Testes de Sensibilidade Microbiana , Modelos Moleculares , Oxirredutases/química , Ratos , Infecções Estafilocócicas/tratamento farmacológico , Staphylococcus aureus/efeitos dos fármacos , Relação Estrutura-AtividadeRESUMO
Potent nanomolar inhibitors of Staphylococcus aureus methionyl tRNA synthetase have been derived from a file compound high throughput screening hit. Optimized compounds show excellent antibacterial activity against staphylococcal and enterococcal pathogens, including strains resistant to clinical antibiotics. Compound 11 demonstrated in vivo efficacy in an S. aureus rat abscess infection model.
Assuntos
Antibacterianos/síntese química , Enterococcus/efeitos dos fármacos , Inibidores Enzimáticos/síntese química , Metionina tRNA Ligase/antagonistas & inibidores , Quinolonas/síntese química , Staphylococcus/efeitos dos fármacos , Abscesso/tratamento farmacológico , Abscesso/microbiologia , Animais , Antibacterianos/química , Antibacterianos/farmacologia , Farmacorresistência Bacteriana , Inibidores Enzimáticos/química , Inibidores Enzimáticos/farmacologia , Quinolonas/química , Quinolonas/farmacologia , Ratos , Ratos Sprague-Dawley , Staphylococcus aureus/efeitos dos fármacos , Staphylococcus aureus/enzimologia , Relação Estrutura-AtividadeRESUMO
A new pharmacokinetically enhanced formulation of amoxicillin-clavulanate (2,000 mg of amoxicillin/125 mg of clavulanate twice a day; ratio 16:1) has been designed, with sustained-release technology, to allow coverage of bacterial strains with amoxicillin-clavulanic acid MICs of at least 4/2 mug/ml. The bacteriological efficacy of amoxicillin-clavulanate, 2,000/125 mg twice a day, ratio 16:1, was compared in a rat model of respiratory tract infection versus four other amoxicillin-clavulanate formulations: 8:1 three times a day (1,000/125 mg), 7:1 three times a day (875/125 mg), 7:1 twice a day (875/125 mg), and 4:1 three times a day (500/125 mg); levofloxacin (500 mg once a day); and azithromycin (1,000 mg on day 1 followed thereafter by 500 mg once a day). Bacterial strains included Streptococcus pneumoniae, with amoxicillin-clavulanic acid MICs of 2/1 (one strain), 4/2, or 8/4 microg/ml (three strains each), and Haemophilus influenzae, one beta-lactamase-positive strain and one beta-lactamase-negative, ampicillin-resistant strain. Animals were infected by intrabronchial instillation. Antibacterial treatment commenced 24 h postinfection, with doses delivered by computer-controlled intravenous infusion to approximate the concentrations achieved in human plasma following oral administration. Plasma concentrations in the rat corresponded closely with target human concentrations for all antimicrobials tested. Amoxicillin-clavulanate, 2,000/125 mg twice a day, ratio 16:1, was effective against all S. pneumoniae strains tested, including those with amoxicillin-clavulanic acid MICs of up to 8/4 microg/ml and against beta-lactamase-producing and beta-lactamase-negative ampicillin-resistant H. influenzae. These results demonstrate the bacteriological efficacy of pharmacokinetically enhanced amoxicillin-clavulanate 2,000/125 mg twice a day (ratio 16:1) against S. pneumoniae with amoxicillin-clavulanic acid MICs of at least 4/2 microg/ml and support clavulanate 125 mg twice a day as sufficient to protect against beta-lactamase in this rat model.
Assuntos
Combinação Amoxicilina e Clavulanato de Potássio/farmacologia , Haemophilus influenzae/efeitos dos fármacos , Streptococcus pneumoniae/efeitos dos fármacos , Amoxicilina/farmacocinética , Amoxicilina/farmacologia , Animais , Azitromicina/farmacologia , Ácido Clavulânico/farmacocinética , Ácido Clavulânico/farmacologia , Humanos , Levofloxacino , Testes de Sensibilidade Microbiana , Ofloxacino/farmacologia , Ratos , Ratos Sprague-DawleyRESUMO
Bacterial enoyl-acyl carrier protein (ACP) reductase (FabI) catalyzes the final step in each elongation cycle of bacterial fatty acid biosynthesis and is an attractive target for the development of new antibacterial agents. High-throughput screening of the Staphylococcus aureus FabI enzyme identified a novel, weak inhibitor with no detectable antibacterial activity against S. aureus. Iterative medicinal chemistry and X-ray crystal structure-based design led to the identification of compound 4 [(E)-N-methyl-N-(2-methyl-1H-indol-3-ylmethyl)-3-(7-oxo-5,6,7,8-tetrahydro-1,8-naphthyridin-3-yl)acrylamide], which is 350-fold more potent than the original lead compound obtained by high-throughput screening in the FabI inhibition assay. Compound 4 has exquisite antistaphylococci activity, achieving MICs at which 90% of isolates are inhibited more than 500 times lower than those of nine currently available antibiotics against a panel of multidrug-resistant strains of S. aureus and Staphylococcus epidermidis. Furthermore, compound 4 exhibits excellent in vivo efficacy in an S. aureus infection model in rats. Biochemical and genetic approaches have confirmed that the mode of antibacterial action of compound 4 and related compounds is via inhibition of FabI. Compound 4 also exhibits weak FabK inhibitory activity, which may explain its antibacterial activity against Streptococcus pneumoniae and Enterococcus faecalis, which depend on FabK and both FabK and FabI, respectively, for their enoyl-ACP reductase function. These results show that compound 4 is representative of a new, totally synthetic series of antibacterial agents that has the potential to provide novel alternatives for the treatment of S. aureus infections that are resistant to our present armory of antibiotics.