FabI Inhibitors Research Articles

Exploring Teucrium aureo-candidum Essential Oil as a Promising Alternative to Triclosan for Targeting Enoyl-Acyl Carrier Protein Reductase: Chemical Composition, Antibacterial Activity, and Molecular Docking Study.

The chemical composition of the essential oil isolated from the aerial parts of Teucrium aureo-candidum, an endemic aromatic shrub collected from Moghrar and Djeniene Bourezg in the Nâama region (Algeria), was determined for the first time using GC/FID and GC/MS. A total of 45 constituents were identified, representing 87.73% of the oil. Characterized by unique chemical variability, it was primarily composed of sesquiterpene hydrocarbons (29.53%) and oxygenated sesquiterpenes (30.06%), with the major compounds being γ-cadinene (5.24%), δ-cadinene (4.24%), α-muurolene (4.04%), τ-muurolol (11.35%), and α-cadinol (3.30%). However, monoterpene hydrocarbons and oxygenated monoterpenes accounted for 23.98% and 1.64%, respectively, contributing to a relatively low fraction. The essential oil demonstrated notable antibacterial activity, particularly against Gram-positive bacteria. Due to safety concerns associated with triclosan, a known inhibitor of the Enoyl-Acyl Carrier Protein Reductase (FabI) enzyme, the essential oil components from this plant were explored as alternatives through a combination of experimental approaches and in silico molecular docking studies. The results revealed that α-cadinol, spathulenol, caryophyllene, and α-muurolene exhibited strong FabI inhibition, with better bioavailability and lower toxicity than triclosan, highlighting their potential in combating antibiotic-resistant bacteria.

Model-based translation of results from in vitro to in vivo experiments for afabicin activity against Staphylococcus aureus.

Translation of experimental data on antibiotic activity typically relies on pharmacokinetic/pharmacodynamic (PK/PD) indices. Model-based approaches, considering the full antibiotic killing time course, could be an alternative. To develop a mechanism-based modelling framework to assess the in vitro and in vivo activity of the FabI inhibitor antibiotic afabicin, and explore the ability of a model built on in vitro data to predict in vivo outcome. A PK/PD model was built to describe bacterial counts from 162 static in vitro time-kill curves evaluating the effect of afabicin desphosphono, the active moiety of the prodrug afabicin, against 21 Staphylococcus aureus strains. Combined with a mouse PK model, outcomes of afabicin doses of 0.011-190 mg/kg q6h against nine S. aureus strains in a murine thigh infection model were predicted, and thereafter refined by estimating PD parameters. A sigmoid Emax model, with EC50 scaled by the MIC described the afabicin desphosphono killing in vitro. This model predicted, without parameter re-estimation, the in vivo bacterial counts at 24 h within a ±1 log margin for most dosing groups. When parameters were allowed to be estimated, EC50 was 38%-45% lower in vivo, compared with in vitro, within the studied MIC range. The developed PK/PD model described the time course of afabicin activity across experimental conditions and bacterial strains. This model showed translational capacity as parameters estimated on in vitro time-kill data could well predict the in vivo outcome for a wide variety of doses in a mouse thigh infection model.

N-acyl-4-arylaminopiperidines: Design and synthesis of a potential antimicrobial scaffold

We report a concise synthesis of N-acylated piperidines through a Knoevenagel-Doebner condensation/amide construction/ amination sequence. The design of the piperidines considered the pharmacophoric features found in previously reported inhibitors of FabI, an enzyme implicated in bacterial fatty acid biosynthesis. After the microbiological evaluation at 50 μM, the analogs displayed moderate activity against some pathogens from the ESKAPE group, reaching up to 42 % of growth inhibition for MRSA, 54 % for K. pneumoniae, and 37 % for P. aeruginosa (multiresistant strains). Docking studies demonstrate that almost all of them docked satisfactorily into the catalytic domain of S. aureus FabI, maintaining a similar pose as other reported inhibitors. The results shown herein propose the N-acyl-4-arylaminopiperidines as the basis for the development of more active candidates.

Exploring the antimicrobial activity of Origanum majorana L. against the highly virulent multidrug-resistant Acinetobacter baumannii AB5075: UPLC-HRMS profiling with in vitro and in silico studies

BackgroundThe infamous multidrug-resistant (MDR) bacterium Acinetobacter baumannii is becoming a nightmare in intensive care units across the globe. Since there are now very few effective antimicrobial agents, it is necessary to explore unconventional resources for novel antimicrobials. This study investigated the potential antimicrobial activity of Origanum majorana L. against A. baumannii employing multiple approaches including antimicrobial susceptibility, fractionation, ultra-performance liquid chromatography–high-resolution mass spectrometry (UPLC-HRMS) dereplication, and in silico analysis for target/ligand identification.ResultsOn the extremely pathogenic MDR strain A. baumannii AB5075, O. majorana L. has shown a significant growth inhibitory effect (MIC = 0.675 mg/mL). The polar 50% methanol fraction was the most active (MIC = 0.5 mg/mL). The UPLC-HRMS dereplication of the bioactive fraction detected 29 metabolites belonging to different chemical classes. Justicidin B, one of the identified metabolites, was projected by preliminary in silico analysis to be the most highly scoring metabolite for binding with molecular targets in A. baumannii with a Fit score = 8.56 for enoyl-ACP reductase (FabI) (PDB ID: 6AHE), suggesting it to be its potential target. Additionally, docking, molecular dynamics simulation, and bioinformatics analysis suggested that this interaction is similar to a well-known FabI inhibitor. The amino acids involved in the interaction are conserved among different MDR A. baumannii strains and the effectiveness could extend to Gram-negative pathogens within the ESKAPE group.ConclusionsOriganum majorana L. extract exhibits antimicrobial activity against A. baumannii using one or more metabolites in its 50% methanol fraction. The characterized active metabolite is hypothesized to be justicidin B which inhibits the growth of A. baumannii AB5075 via targeting its fatty acid synthesis.

In vitro and in vivo enhancement effect of glabridin on the antibacterial activity of colistin, against multidrug resistant Escherichia coli strains

BackgroundThe increase in antimicrobial resistance leads to complications in treatments, prolonged hospitalization, and increased mortality. Glabridin (GLA) is a hydroxyisoflavan from Glycyrrhiza glabra L. that exhibits multiple pharmacological activities. Colistin (COL), a last-resort antibiotic, is increasingly being used in clinic against Gram-negative bacteria. Previous reports have shown that GLA is able to sensitize first line antibiotics such as norfloxacin and vancomycin on Staphylococcus aureus, implying that the use of GLA as an antibiotic adjuvant is a promising strategy for addressing the issue of drug resistance. However, the adjuvant effect on other antibiotics, especially COL, on Gram-negative bacteria such as Escherichia coli has not been studied. PurposeThe objective of our study was to investigate the targets of GLA and the synergistic effect of GLA and COL in E. coli, and to provide further evidence for the use of GLA as an antibiotic adjuvant to alleviate the problem of drug resistance. MethodsWe first investigated the interaction between GLA and enoyl-acyl carrier protein reductase, also called "FabI", through enzyme inhibition assay, differential scanning fluorimetry, isothermal titration calorimetry and molecular docking assay. We tested the transmembrane capacity of GLA on its own and combined it with several antibiotics. The antimicrobial activities of GLA and COL were evaluated against six different susceptible and resistant E. coli in vitro. Their interactions were analyzed using checkerboard assay, time-kill curve and CompuSyn software. A series of sensitivity tests was conducted in E. coli overexpressing the fabI gene. The development of COL resistance in the presence of GLA was tested. The antimicrobial efficacy of GLA and COL in a mouse model of urinary tract infection was assessed. The anti-biofilm effects of GLA and COL were investigated. ResultsIn this study, enzyme kinetic analysis and thermal analysis provided evidence for the interaction between GLA and FabI in E. coli. GLA enhanced the antimicrobial effect of COL and synergistically suppressed six different susceptible and resistant E. coli with COL. Overexpression experiments showed that targeted inhibition of FabI was a key mechanism by which GLA synergistically enhanced COL activity. The combination of GLA and COL slowed the development of COL resistance in E. coli. Combined GLA and COL treatment significantly reduced bacterial load and mitigated urinary tract injury in a mouse model of E. coli urinary tract infection. Additionally, GLA + COL inhibited the formation and eradication of biofilms and the synthesis of curli. ConclusionOur findings indicate that GLA synergistically enhances antimicrobial activities of COL by targeting inhibition of FabI in E. coli. GLA is expected to continue to be developed as an antibiotic adjuvant to address drug resistance issues.

Inhibiting fatty acid synthesis overcomes colistin resistance.

Treating multidrug-resistant infections has increasingly relied on last-resort antibiotics, including polymyxins, for example colistin. As polymyxins are given routinely, the prevalence of their resistance is on the rise and increases mortality rates of sepsis patients. The global dissemination of plasmid-borne colistin resistance, driven by the emergence of mcr-1, threatens to diminish the therapeutic utility of polymyxins from an already shrinking antibiotic arsenal. Restoring sensitivity to polymyxins using combination therapy with sensitizing drugs is a promising approach to reviving its clinical utility. Here we describe the ability of the biotin biosynthesis inhibitor, MAC13772, to synergize with colistin exclusively against colistin-resistant bacteria. MAC13772 indirectly disrupts fatty acid synthesis (FAS) and restores sensitivity to the last-resort antibiotic, colistin. Accordingly, we found that combinations of colistin and other FAS inhibitors, cerulenin, triclosan and Debio1452-NH3, had broad potential against both chromosomal and plasmid-mediated colistin resistance in chequerboard and lysis assays. Furthermore, combination therapy with colistin and the clinically relevant FabI inhibitor, Debio1452-NH3, showed efficacy against mcr-1 positive Klebsiella pneumoniae and colistin-resistant Escherichia coli systemic infections in mice. Using chemical genomics, lipidomics and transcriptomics, we explored the mechanism of the interaction. We propose that inhibiting FAS restores colistin sensitivity by depleting lipid synthesis, leading to changes in phospholipid composition. In all, this work reveals a surprising link between FAS and colistin resistance.

Molecular Modelling Study and Antibacterial Evaluation of Diphenylmethane Derivatives as Potential FabI Inhibitors.

The need for new antibiotics has become a major worldwide challenge as bacterial strains keep developing resistance to the existing drugs at an alarming rate. Enoyl-acyl carrier protein reductases (FabI) play a crucial role in lipids and fatty acid biosynthesis, which are essential for the integrity of the bacterial cell membrane. Our study aimed to discover small FabI inhibitors in continuation to our previously found hit MN02. The process was initially started by conducting a similarity search to the NCI ligand database using MN02 as a query. Accordingly, ten compounds were chosen for the computational assessment and antimicrobial testing. Most of the compounds showed an antibacterial activity against Gram-positive strains, while RK10 exhibited broad-spectrum activity against both Gram-positive and Gram-negative bacteria. All tested compounds were then docked into the saFabI active site followed by 100 ns MD simulations (Molecular Dynamics) and MM-GBSA (Molecular Mechanics with Generalised Born and Surface Area Solvation) calculations in order to understand their fitting and estimate their binding energies. Interestingly, and in line with the experimental data, RK10 was able to exhibit the best fitting with the target catalytic pocket. To sum up, RK10 is a small compound with leadlike characteristics that can indeed act as a promising candidate for the future development of broad-spectrum antibacterial agents.

Do Go Chasing Waterfalls: Enoyl Reductase (FabI) in Complex with Inhibitors Stabilizes the Tetrameric Structure and Opens Water Channels.

The enzyme enoyl-ACP reductase (FabI) is the limiting step of the membrane's fatty acid biosynthesis in bacteria and a druggable target for novel antibacterial agents. The FabI active form is a homotetramer, which displays the highest affinity to inhibitors. Herein, molecular dynamics studies were carried out using the structure of FabI in complex with known inhibitors to investigate their effects on tetramerization. Our results suggest that multimerization is essential for the integrity of the catalytic site and that inhibitor binding enables the multimerization by stabilizing the substrate binding loop (SBL, L:195-200) coupled with changes in the H4/5 (QR interface). We also observed that AFN-1252 (naphtpyridinone derivative) promotes unique conformational changes affecting monomer-monomer interfaces. These changes are induced by AFN-1252 interaction with key residues in the binding sites (Ala95, Tyr146, and Tyr156). In addition, the analysis of water trajectories indicated that AFN-1252 complexes allow more water molecules to enter the binding site than triclosan and MUT056399 complexes. FabI-AFN-1252 simulations show accumulation of water molecules near the Tyr146/147 pocket, which can become a hotspot to the design of novel FabI inhibitors.

GCN-Based Structure-Activity Relationship and DFT Studies of Staphylococcus aureus FabI Inhibitors

The enoyl-[acyl-carrier-protein] reductase (FabI) is an important enzyme in the fatty acid metabolism of Gram-positive bacteria, such as Staphylococcus aureus. FabI is also a potential target for the development of novel antibacterials. Several machine learning-driven studies were reported to develop FabI inhibitors, describing robust and predictive models. Herein, the authors applied the kGCN, a graph convolutional network framework, to generate classification models to select potential S. aureus FabI inhibitors. The most predictive model showed robustness for both active and inactive class prediction, according to statistical validation. Finally, the chemical interpretation of the model was consistent with prior experimental and theoretical works. The SAR analysis highlighted the importance of the occupation of hydrophobic pockets and polar interactions with Tyr-156 and NADPH cofactor present in the FabI catalytic site by potential inhibitors. A density functional theory study endorsed the SAR, where the electrostatic surfaces were consistent with the expected interactions with the pocket.

An Iterative Approach Guides Discovery of the FabI Inhibitor Fabimycin, a Late-Stage Antibiotic Candidate with In Vivo Efficacy against Drug-Resistant Gram-Negative Infections.

Genomic studies and experiments with permeability-deficient strains have revealed a variety of biological targets that can be engaged to kill Gram-negative bacteria. However, the formidable outer membrane and promiscuous efflux pumps of these pathogens prevent many candidate antibiotics from reaching these targets. One such promising target is the enzyme FabI, which catalyzes the rate-determining step in bacterial fatty acid biosynthesis. Notably, FabI inhibitors have advanced to clinical trials for Staphylococcus aureus infections but not for infections caused by Gram-negative bacteria. Here, we synthesize a suite of FabI inhibitors whose structures fit permeation rules for Gram-negative bacteria and leverage activity against a challenging panel of Gram-negative clinical isolates as a filter for advancement. The compound to emerge, called fabimycin, has impressive activity against >200 clinical isolates of Escherichia coli, Klebsiella pneumoniae, and Acinetobacter baumannii, and does not kill commensal bacteria. X-ray structures of fabimycin in complex with FabI provide molecular insights into the inhibition. Fabimycin demonstrates activity in multiple mouse models of infection caused by Gram-negative bacteria, including a challenging urinary tract infection model. Fabimycin has translational promise, and its discovery provides additional evidence that antibiotics can be systematically modified to accumulate in Gram-negative bacteria and kill these problematic pathogens.

Synthesis and Evaluation of Antimicrobial Activity of N-Substituted Indole Derivatives and Molecular Docking Studies

Abstracts: The increasing burden of microbial infection and emerging resistance against the available antimicrobial drugs drives the development of new agents. Two different series of indole-based compounds (VN-1 to VN-18) were synthesized and analyzed for antimicrobial activity by calculating the diameter of the inhibition zone using the broth dilution method and well diffusion method against Escherichia coli (E. coli) and environmental microbes. Most of the compounds displayed good to moderate activity against E. coli, and VN-4 and VN-9 displayed good inhibitory activity against the tested microbes. Molecular docking and binding energy calculation studies of all the synthesized compounds have been performed for targeting FabI, where most of the compounds showed significant interactions with the aromatic nicotinamide moiety of NAD+. In molecular dynamics studies, VN-9 stays inside the binding cavity for sufficient time to induce antimicrobial activity. Thus, these indole-based derivatives may lead to the development of new antimicrobial agents that may act as FabI inhibitors.

Triclosan is the Predominant Antibacterial Compound in Ontario Sewage Sludge.

Sewage treatment plants (STPs) accumulate both antibiotic and nonantibiotic antimicrobial compounds that can select for antibiotic resistant bacteria. Herein, we aimed to identify the predominant antibacterial compounds impacting E. coli from Ontario sewage sludge consisting of thousands of unknown compounds. Among the 10 extracted sludge samples, 6 extracts exerted significant growth inhibition effects in E. coli. A total of 103 compounds were tentatively detected across the 10 sludge samples by suspect screening, among which the bacterial enoyl-ACP reductase (FabI) inhibitor triclocarban was detected at the highest abundance. A hypomorphic FabI knockdown E. coli strain was highly susceptible to the sludge extracts, confirming FabI inhibitors as the primary antibacterial compounds in the sludge. Protein affinity pulldown identified triclosan as the major ligand binding to a His-tagged FabI protein from the sludge, despite the higher abundance of triclocarban in the same samples. Effect-directed analysis was used to determine the contributions of triclosan to the observed antibacterial potencies. Antibacterial effects were only detected in F17 and F18 across 20 fractions, which was consistent with the elution of triclosan and triclocarban in the same two fractions. Further, potency mass balance analysis confirmed that triclosan explained the majority (58-113%) of inhibition effects from sludge extracts. This study highlighted triclosan as the predominant antibacterial compound in sewage sludge impacting E. coli despite the co-occurrence of numerous other antibiotics and nonantibiotics.

Biochemical and structural basis for Moraxella catarrhalis enoyl-acyl carrier protein reductase (FabI) inhibition by triclosan and estradiol

The enoyl-acyl carrier protein reductase (ENR) is an established drug target and catalyzes the last reduction step of the fatty acid elongation cycle. Here, we report the crystal structures of FabI from Moraxella catarrhalis (McFabI) in the apo form, binary complex with NAD+ and ternary complex with NAD + -triclosan (TCL) determined at 2.36, 2.12 and 2.22 Å resolutions, respectively. The comparative study of these three structures revealed three different conformational states for the substrate-binding loop (SBL), including an unstructured intermediate, a structured intermediate and a closed conformation in the apo, binary and ternary complex forms, respectively; indicating the flexibility of SBL during the ligand binding. Virtual screening has suggested that estradiol cypionate may be a potential inhibitor of McFabI. Subsequently, estradiol (EST), the natural form of estradiol cypionate, was assessed for its FabI-binding and -inhibition properties. In vitro studies demonstrated that TCL and EST bind to McFabI with high affinity (KD = 0.038 ± 0.004 and 5 ± 0.06 μM respectively) and inhibit its activity (Ki = 62.93 ± 3.95 nM and 25.97 ± 1.93 μM respectively) and suppress the growth of M. catarrhalis. These findings reveal that TCL and EST inhibit the McFabI activity and thereby affect cell growth. This study suggests that estradiol may be exploited as a novel scaffold for the designing and development of more potential FabI inhibitors.

Novel FabI inhibitor disrupts the biofilm formation of MRSA through down-regulating the expression of quorum-sensing regulatory genes

ObjectivesThe aim of this study was to explore the antibiofilm and antivirulence efficacy of benzylaniline 4k against MRSA. MethodsThe clinical MRSA strains were identified and used to evaluate their potential to form biofilm using crystal violet assay. The minimal inhibitory concentration (MIC) was determined using broth microdilution method. The expression of genes was detected using quantitative real-time PCR (qRT-PCR). Rabbit blood hemolytic assay was used to observe the inhibitory ability of alpha-hemolysin (Hla). ResultsCompound 4k showed potent antibacterial activity against 16 clinical MRSA with an MIC50 of 1.25 mg/L and MIC90 of 2.25 mg/L. The value of minimum biofilm eradication concentration (MBEC) against MRSA2858 biofilm was of 1.5 mg/L, close to its MIC, superior to those of vancomycin and erythromycin. Compound 4k eradicated the formation of biofilm through inhibiting the gene expression of branched-chain fatty acid synthesis, down-regulating the expression of quorum-sensing (QS) regulatory genes (norA, agrA, icaA, hla), decreasing the level of hemolysis in a dose-dependent manner, and inhibiting rabbit blood hemolysis by 86.9% at a concentration of 1.25 mg/L. In a mouse model of abdominal infection, compound 4k was more effective than vancomycin in reducing bacterial load. ConclusionsThese results suggested that compound 4k could be developed as promising an anti-MRSA agent through affecting quorum-sensing system.

Characterization of protein-ligand binding interactions of enoyl-ACP reductase (FabI) by native MS reveals allosteric effects of coenzymes and the inhibitor triclosan.

The enzyme enoyl-ACP reductase (also called FabI in bacteria) is an essential member of the fatty acid synthase II pathway in plants and bacteria. This enzyme is the target of the antibacterial drug triclosan and has been the subject of extensive studies for the past 20 years. Despite the large number of reports describing the biochemistry of this enzyme, there have been no studies that provided direct observation of the protein and its various ligands. Here we describe the use of native MS to characterize the protein-ligand interactions of FabI with its coenzymes NAD+ and NADH and with the inhibitor triclosan. Measurements of the gas-phase affinities of the enzyme for these ligands yielded values that are in close agreement with solution-phase affinity measurements. Additionally, FabI is a homotetramer and we were able to measure the affinity of each subunit for each coenzyme, which revealed that both coenzymes exhibit a positive homotropic allosteric effect. An allosteric effect was also observed in association with the inhibitor triclosan. These observations provide new insights into this well-studied enzyme and suggest that there may still be gaps in the existing mechanistic models that explain FabI inhibition.

Dye degradation, antibacterial and in-silico analysis of Mg/cellulose-doped ZnO nanoparticles

Various concentrations of Mg into fixed amount of cellulose nanocrystals (CNC)-doped ZnO were synthesized using facile chemical precipitation. The aim of present study is to remove dye degradation of methylene blue (MB) and bactericidal behavior with synthesized product. Phase constitution, functional group analysis, optical behavior, elemental composition, morphology and microstructure were examined using XRD, FTIR, UV–Vis spectrophotometer, EDS and HR-TEM. Highly efficient photocatalytic performance was observed in basic medium (98%) relative to neutral (65%), and acidic (83%) was observed upon Mg and CNC co-doping. Significant bactericidal activity of doped ZnO nanoparticles depicted inhibition zones for G –ve and +ve bacteria ranging (2.20 - 4.25 mm) and (5.80–7.25 mm) for E. coli and (1.05 - 2.75 mm) and (2.80 - 4.75 mm) for S. aureus at low and high doses, respectively. Overall, doped nanostructures showed significant (P < 0.05) bactericidal efficacy against G +ve relative to G –ve. Furthermore, the molecular docking studies were employed to rationalize possible mechanism behind these in vitro bactericidal activities. In silico findings suggested CNC doped ZnO nanocomposites as possible inhibitors of β-lactamase (Binding score: −7.936 kcal/mol), DHFR (Binding score: −5.691 kcal/mol) and FabI (Binding score: −8.673 kcal/mol).

Facilitating Compound Entry as a Means to Discover Antibiotics for Gram-Negative Bacteria.

It has been over half a century since the last class of antibiotics active against the most problematic Gram-negative bacteria was approved by the Food and Drug Administration (FDA). The major challenge with developing antibiotics to treat these infections is not drug-target engagement but rather the inability of most small molecules to traverse the Gram-negative membranes, be retained, and accumulate within the cell. Despite an abundance of lead compounds, limited understanding of the physicochemical properties needed for compound accumulation (or avoidance of efflux) in Gram-negative bacteria has precluded a generalizable approach for developing Gram-negative antibiotics. Indeed, in many instances, despite years of intensive derivatization efforts and the synthesis of hundreds of compounds aimed at building in Gram-negative activity, little or no progress has been made in expanding the spectrum of activity for many Gram-positive-only antibiotics. In this Account, we describe the discovery and successful applications of a promising strategy for enhancing the accumulation of Gram-positive-only antibiotics as a means of imbuing compounds with broad-spectrum activity.Utilizing a prospective approach examining the accumulation in Escherichia coli for more than 180 diverse compounds, we found that small molecules have an increased likelihood to accumulate in E. coli when they contain an ionizable Nitrogen, have low Three-dimensionality, and are Rigid. Implementing these guidelines, codified as the "eNTRy rules" and assisted by web application www.entry-way.org, we have facilitated compound entry and systematically built Gram-negative activity into Gram-positive-only antibiotics. Though each antibiotic will have case-specific considerations, we describe a set of important criteria to consider when selecting candidate Gram-positive-only antibiotics for conversion to Gram-negative-active versions via the eNTRy rules. As detailed herein, using this blueprint the spectrum of activity was expanded for three antibiotic classes that engage three different biological targets: DNA gyrase inhibitor 6DNM, FabI inhibitor Debio-1452, and FMN riboswitch inhibitor Ribocil C. In each scenario, the eNTRy rules guided the synthesis of key analogues predisposed to accumulate in Gram-negative bacteria leading to compounds that display antibiotic activity (minimum inhibitory concentrations (MIC) ≤8 μg mL-1) against E. coli and other Gram-negative ESKAPE pathogens. While the eNTRy rules will continue to be refined and enhanced as more accumulation data is gathered, on the basis of these collective results and on other examples not covered herein it is clear that the eNTRy rules are actionable for the development of novel broad-spectrum antibiotics from Gram-positive-only compounds. By enabling the prediction of compound accumulation, the eNTRy rules should facilitate the process of discovering and developing novel antibiotics active against Gram-negative bacteria.

Afabicin. Enoyl-(acyl-carrier-protein) reductase FabI inhibitor, Antibacterial drug

Afabicin. Enoyl-(acyl-carrier-protein) reductase FabI inhibitor, Antibacterial drug

Afabicin, a First-in-Class Antistaphylococcal Antibiotic, in the Treatment of Acute Bacterial Skin and Skin Structure Infections: Clinical Noninferiority to Vancomycin/Linezolid.

Afabicin (formerly Debio 1450, AFN-1720) is a prodrug of afabicin desphosphono, an enoyl-acyl carrier protein reductase (FabI) inhibitor, and is a first-in-class antibiotic with a novel mode of action to specifically target fatty acid synthesis in Staphylococcus spp. The efficacy, safety, and tolerability of afabicin were compared with those of vancomycin/linezolid in the treatment of acute bacterial skin and skin structure infections (ABSSSI) due to staphylococci in this multicenter, parallel-group, double-blind, and double-dummy phase 2 study. Randomized patients (1:1:1) received either low-dose (LD) afabicin (intravenous [i.v.] 80 mg, followed by oral 120 mg, twice a day [BID]), high-dose (HD) afabicin (i.v. 160 mg, followed by oral 240 mg, BID), or vancomycin/linezolid (i.v. vancomycin 1 g or 15 mg/kg, followed by oral linezolid 600 mg, BID). The most frequent baseline pathogen was Staphylococcus aureus (97.5% of microbiological intent-to-treat [mITT] population), and 50.4% of patients had methicillin-resistant S. aureus Clinical response rates at 48 to 72 h postrandomization in the mITT population were comparable among treatment groups (94.6%, 90.1%, and 91.1%, respectively). Both LD and HD afabicin were noninferior to vancomycin/linezolid (differences, -3.5% [95% confidence interval {CI}, -10.8%, 3.9%] and 1.0% [95% CI, -7.3%, 9.2%], respectively). Most common treatment-emergent adverse events were mild and were headache (9.1% and 16.8%) and nausea (6.4% and 8.4%) with LD and HD afabicin, respectively. Afabicin was efficacious and well tolerated in the treatment of ABSSSI due to staphylococci, and these data support further development of afabicin for the treatment of ABSSSI and potentially other types of staphylococcal infections. (This study has been registered at ClinicalTrials.gov under identifier NCT02426918.).

FabI (enoyl acyl carrier protein reductase) - A potential broad spectrum therapeutic target and its inhibitors.

Development of new anti-bacterial agents acting upon underexploited targets and thus evading known mechanisms of resistance is the need of the hour. The highly conserved and distinct bacterial fatty acid biosynthesis pathway (FAS-II), presents a validated and yet relatively underexploited target for drug discovery. FabI and its isoforms (FabL, FabK, FabV and InhA) are essential enoyl-ACP reductases present in several microorganisms. In addition, the components of the FAS-II pathway are distinct from the multi-enzyme FAS-I complex found in mammals. Thus, inhibition of FabI and its isoforms is anticipated to result in broad-spectrum antibacterial activity. Several research groups from industry and academic laboratories have devoted significant efforts to develop effective FabI-targeting antibiotics, which are currently in various stages of clinical development for the treatment of multi-drug resistant bacterial infections. This review summarizes all the natural as well as synthetic inhibitors of gram-positive and gram-negative enoyl ACP reductases (FabI). The knowledge of the reported inhibitors can aid in the development of broad-spectrum antibacterials specifically targeting FabI enzymes from S.aureus, S.epidermidis, B.anthracis, B.cereus, E.coli, P. aeruginosa, P. falciparum and M. tuberculosis.