RESUMO
Many drug candidates fail in clinical trials owing to a lack of efficacy from limited target engagement or an insufficient therapeutic index. Minimizing off-target effects while retaining the desired pharmacodynamic (PD) response can be achieved by reduced exposure for drugs that display kinetic selectivity in which the drug-target complex has a longer half-life than off-target-drug complexes. However, though slow-binding inhibition kinetics are a key feature of many marketed drugs, prospective tools that integrate drug-target residence time into predictions of drug efficacy are lacking, hindering the integration of drug-target kinetics into the drug discovery cascade. Here we describe a mechanistic PD model that includes drug-target kinetic parameters, including the on- and off-rates for the formation and breakdown of the drug-target complex. We demonstrate the utility of this model by using it to predict dose response curves for inhibitors of the LpxC enzyme from Pseudomonas aeruginosa in an animal model of infection.
Assuntos
Amidoidrolases/antagonistas & inibidores , Antibacterianos/farmacologia , Inibidores Enzimáticos/farmacologia , Ácidos Hidroxâmicos/farmacologia , Treonina/análogos & derivados , Animais , Antibacterianos/química , Antibacterianos/farmacocinética , Inibidores Enzimáticos/química , Inibidores Enzimáticos/farmacocinética , Ácidos Hidroxâmicos/química , Ácidos Hidroxâmicos/farmacocinética , Cinética , Camundongos Endogâmicos , Testes de Sensibilidade Microbiana , Modelos Biológicos , Estrutura Molecular , Ligação Proteica , Pseudomonas aeruginosa/efeitos dos fármacos , Pseudomonas aeruginosa/enzimologia , Treonina/química , Treonina/farmacocinética , Treonina/farmacologia , Fatores de TempoRESUMO
AZD0914 is a new spiropyrimidinetrione bacterial DNA gyrase/topoisomerase inhibitor with potent in vitro antibacterial activity against key Gram-positive (Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pneumoniae, Streptococcus pyogenes, and Streptococcus agalactiae), fastidious Gram-negative (Haemophilus influenzae and Neisseria gonorrhoeae), atypical (Legionella pneumophila), and anaerobic (Clostridium difficile) bacterial species, including isolates with known resistance to fluoroquinolones. AZD0914 works via inhibition of DNA biosynthesis and accumulation of double-strand cleavages; this mechanism of inhibition differs from those of other marketed antibacterial compounds. AZD0914 stabilizes and arrests the cleaved covalent complex of gyrase with double-strand broken DNA under permissive conditions and thus blocks religation of the double-strand cleaved DNA to form fused circular DNA. Whereas this mechanism is similar to that seen with fluoroquinolones, it is mechanistically distinct. AZD0914 exhibited low frequencies of spontaneous resistance in S. aureus, and if mutants were obtained, the mutations mapped to gyrB. Additionally, no cross-resistance was observed for AZD0914 against recent bacterial clinical isolates demonstrating resistance to fluoroquinolones or other drug classes, including macrolides, ß-lactams, glycopeptides, and oxazolidinones. AZD0914 was bactericidal in both minimum bactericidal concentration and in vitro time-kill studies. In in vitro checkerboard/synergy testing with 17 comparator antibacterials, only additivity/indifference was observed. The potent in vitro antibacterial activity (including activity against fluoroquinolone-resistant isolates), low frequency of resistance, lack of cross-resistance, and bactericidal activity of AZD0914 support its continued development.
Assuntos
Antibacterianos/farmacologia , Barbitúricos/farmacologia , DNA Girase/efeitos dos fármacos , Inibidores da Síntese de Ácido Nucleico/farmacologia , Compostos de Espiro/farmacologia , Inibidores da Topoisomerase II/farmacologia , Formas Bacterianas Atípicas/efeitos dos fármacos , Farmacorresistência Bacteriana , Fluoroquinolonas/farmacologia , Bactérias Gram-Negativas/efeitos dos fármacos , Bactérias Gram-Positivas/efeitos dos fármacos , Isoxazóis , Testes de Sensibilidade Microbiana , Morfolinas , OxazolidinonasRESUMO
The objective of this study was to investigate the risk of attenuated efficacy due to adaptive resistance for the siderophore-conjugated monocarbam SMC-3176 in Pseudomonas aeruginosa by using a pharmacokinetic/pharmacodynamic (PK/PD) approach. MICs were determined in cation-adjusted Mueller-Hinton broth (MHB) and in Chelex-treated, dialyzed MHB (CDMHB). Spontaneous resistance was assessed at 2× to 16× the MIC and the resulting mutants sequenced. Efficacy was evaluated in a neutropenic mouse thigh model at 3.13 to 400 mg/kg of body weight every 3 h for 24 h and analyzed for association with free time above the MIC (fT>MIC). To closer emulate the conditions of the in vivo model, we developed a novel assay testing activity mouse whole blood (WB). All mutations were found in genes related to iron uptake: piuA, piuC, pirR, fecI, and pvdS. Against four P. aeruginosa isolates, SMC-3176 displayed predictable efficacy corresponding to the fT>MIC using the MIC in CDMHB (R(2) = 0.968 to 0.985), with stasis to 2-log kill achieved at 59.4 to 81.1%. Efficacy did not translate for P. aeruginosa isolate JJ 4-36, as the in vivo responses were inconsistent with fT>MIC exposures and implied a threshold concentration that was greater than the MIC. The results of the mouse WB assay indicated that efficacy was not predictable using the MIC for JJ 4-36 and four additional isolates, against which in vivo failures of another siderophore-conjugated ß-lactam were previously reported. SMC-3176 carries a risk of attenuated efficacy in P. aeruginosa due to rapid adaptive resistance preventing entry via the siderophore-mediated iron uptake systems. Substantial in vivo testing is warranted for compounds using the siderophore approach to thoroughly screen for this in vitro-in vivo disconnect in P. aeruginosa.
Assuntos
Antibacterianos/farmacologia , Azetidinas/farmacologia , Farmacorresistência Bacteriana/genética , Pseudomonas aeruginosa/metabolismo , Sideróforos/farmacologia , Sulfonamidas/farmacologia , Animais , Antibacterianos/farmacocinética , Azetidinas/farmacocinética , Feminino , Ferro/metabolismo , Camundongos , Camundongos Endogâmicos ICR , Testes de Sensibilidade Microbiana , Oligopeptídeos/metabolismo , Infecções por Pseudomonas/tratamento farmacológico , Infecções por Pseudomonas/microbiologia , Pseudomonas aeruginosa/efeitos dos fármacos , Sideróforos/farmacocinética , Sulfonamidas/farmacocinética , beta-Lactamases/metabolismoRESUMO
OBJECTIVES: The combination of aztreonam/avibactam has promising activity against MDR Gram-negative pathogens producing metallo-ß-lactamases (MBLs), such as New Delhi MBL-1. Pharmacokinetic (PK)/pharmacodynamic (PD) understanding of this combination is critical for optimal clinical dose selection. This study focuses on the determination of an integrated PK/PD approach for aztreonam/avibactam across multiple clinical Enterobacteriaceae strains. METHODS: Six clinical Enterobacteriaceae isolates expressing MBLs and ESBLs were studied in an in vitro hollow-fibre infection model (HFIM) using various dosing regimens simulating human-like PK for aztreonam/avibactam. The neutropenic murine thigh infection model was used for in vivo validation against two bacterial strains. RESULTS: MIC values of aztreonam/avibactam for the isolates ranged from 0.125 to 8 mg/L. Using a constant infusion of avibactam at 4 mg/L, the aztreonam PK/PD index was observed as % fT >MIC. Studies performed in the presence of a fixed dose of aztreonam revealed that the efficacy of avibactam correlates best with percentage of time above a critical threshold concentration of 2-2.5 mg/L. These conclusions translated well to the efficacy observed in the murine thigh model, demonstrating in vivo validation of the in vitro PK/PD target. CONCLUSIONS: PK/PD evaluations for aztreonam/avibactam in HFIM yielded a single target across strains with a wide MIC range. This integrated approach could be easily applied for forecasting clinically efficacious doses for ß-lactam/ß-lactamase inhibitor combinations.
Assuntos
Antibacterianos/administração & dosagem , Antibacterianos/farmacocinética , Compostos Azabicíclicos/administração & dosagem , Compostos Azabicíclicos/farmacocinética , Aztreonam/administração & dosagem , Aztreonam/farmacocinética , Infecções por Enterobacteriaceae/tratamento farmacológico , Animais , Antibacterianos/farmacologia , Compostos Azabicíclicos/farmacologia , Aztreonam/farmacologia , Modelos Animais de Doenças , Enterobacteriaceae/efeitos dos fármacos , Feminino , Camundongos , Testes de Sensibilidade Microbiana , Modelos Biológicos , Resultado do Tratamento , Inibidores de beta-Lactamases/administração & dosagem , Inibidores de beta-Lactamases/farmacocinética , Inibidores de beta-Lactamases/farmacologia , beta-Lactamas/administração & dosagem , beta-Lactamas/farmacocinética , beta-Lactamas/farmacologiaRESUMO
Avibactam is a novel non-ß-lactam ß-lactamase inhibitor being developed in combination with ceftazidime, ceftaroline and aztreonam for the treatment of infections caused by Gram-negative bacteria. Avibactam protects the antibacterial activity of these antibiotics by inhibiting Ambler classes A and C and some class D ß-lactamases. The Gram-negative cell envelope presents a complex barrier to hydrophilic solutes and contains multiple molecular determinants of antibiotic susceptibility and resistance. To investigate the role of some of these determinants in the activity of avibactam and its partner antibiotics in Escherichia coli, an isogenic panel with deletions in specific components of the cell envelope was constructed in an E. coli W3110 strain background. The mutant constructs were also engineered to express the ß-lactamase CTX-M-15 as a tool to enable assessment of the activity of avibactam. Mutations to shorten the lipopolysaccharide (LPS), to reduce efflux from the basal (i.e. non-upregulated) level or to alter the outer membrane porin composition did not have appreciable effects on the in vitro activity of ceftazidime, ceftaroline or aztreonam alone or in combination with avibactam. In conclusion, in this susceptible strain background, none of the ß-lactams nor avibactam was measurably subject to efflux based on evaluating minimum inhibitory concentrations (MICs). None of the porin single or double mutations caused a decrease in susceptibility to the test compounds, implying that the compounds do not possess a strong porin preference, but instead can pass the outer membrane through a variety of routes.
Assuntos
Antibacterianos/farmacologia , Compostos Azabicíclicos/farmacologia , Escherichia coli/efeitos dos fármacos , Mutação , Inibidores de beta-Lactamases/farmacologia , beta-Lactamas/farmacologia , Membrana Celular/genética , Parede Celular/genética , Escherichia coli/genética , Deleção de Genes , Lipopolissacarídeos/genética , Testes de Sensibilidade Microbiana , Porinas/genéticaRESUMO
To identify new agents for the treatment of multi-drug-resistant Pseudomonas aeruginosa, we focused on siderophore-conjugated monocarbams. This class of monocyclic ß-lactams are stable to metallo-ß-lactamases and have excellent P. aeruginosa activities due to their ability to exploit the iron uptake machinery of Gram-negative bacteria. Our medicinal chemistry plan focused on identifying a molecule with optimal potency and physical properties and activity for in vivo efficacy. Modifications to the monocarbam linker, siderophore, and oxime portion of the molecules were examined. Through these efforts, a series of pyrrolidinone-based monocarbams with good P. aeruginosa cellular activity (P. aeruginosa MIC90 = 2 µg/mL), free fraction levels (>20% free), and hydrolytic stability (t1/2 ≥ 100 h) were identified. To differentiate the lead compounds and enable prioritization for in vivo studies, we applied a semi-mechanistic pharmacokinetic/pharmacodynamic model to enable prediction of in vivo efficacy from in vitro data.