and Properties of CUO246, a Novel Bacterial DNA Gyrase/Topoisomerase IV Inhibitor.

CUO246, a novel DNA gyrase/topoisomerase IV inhibitor, is active against a broad range of Gram-positive, fastidious Gram-negative, and atypical bacterial pathogens and retains activity against quinolone-resistant strains in circulation. The frequency of selection for single step mutants of wild-type S. aureus with reduced susceptibility to CUO246 was <4.

Discovery and Optimization of DNA Gyrase and Topoisomerase IV Inhibitors with Potent Activity against Fluoroquinolone-Resistant Gram-Positive Bacteria.

Herein, we describe the discovery and optimization of a novel series that inhibits bacterial DNA gyrase and topoisomerase IV binding to, and stabilization of, DNA cleavage complexes. Optimization of this series led to the identification of compound , which has potent activity against Gram-positive bacteria, a favorable safety profile, and excellent pharmacokinetic properties. Compound was found to be efficacious against fluoroquinolone-sensitive infection in a mouse thigh model at lower doses than moxifloxacin.

Topoisomerase Inhibitors Addressing Fluoroquinolone Resistance in Gram-Negative Bacteria.

Since their discovery over 5 decades ago, quinolone antibiotics have found enormous success as broad spectrum agents that exert their activity through dual inhibition of bacterial DNA gyrase and topoisomerase IV. Increasing rates of resistance, driven largely by target-based mutations in the GyrA/ParC quinolone resistance determining region, have eroded the utility and threaten the future use of this vital class of antibiotics. Herein we describe the discovery and optimization of a series of 4-(aminomethyl)quinolin-2(1)-ones, exemplified by , that inhibit bacterial DNA gyrase and topoisomerase IV and display potent activity against ciprofloxacin-resistant Gram-negative pathogens.

Discovery of Novel Antibiotics as Covalent Inhibitors of Fatty Acid Synthesis.

The steady increase in the prevalence of multidrug-resistant has made the search for novel antibiotics to combat this clinically important pathogen an urgent matter. In an effort to discover antibacterials with new chemical structures and mechanisms, we performed a growth inhibition screen of a synthetic library against and discovered a promising scaffold with a 1,3,5-oxadiazin-2-one core. These compounds are potent against both methicillin-sensitive and methicillin-resistant strains.

Perspective on Antibacterial Lead Identification Challenges and the Role of Hypothesis-Driven Strategies.

For the past three decades, the pharmaceutical industry has undertaken many diverse approaches to discover novel antibiotics, with limited success. We have witnessed and personally experienced many mistakes, hurdles, and dead ends that have derailed projects and discouraged scientists and business leaders. Of the many factors that affect the outcomes of screening campaigns, a lack of understanding of the properties that drive efflux and permeability requirements across species has been a major barrier for advancing hits to leads.

Activity of LYS228, a Novel Monobactam Antibiotic, against Multidrug-Resistant Enterobacteriaceae.

LYS228 is a novel monobactam with potent activity against LYS228 is stable to metallo-β-lactamases (MBLs) and serine carbapenemases, including carbapenemases (KPCs), resulting in potency against the majority of extended-spectrum β-lactamase (ESBL)-producing and carbapenem-resistant strains tested. Overall, LYS228 demonstrated potent activity against 271 strains, including multidrug-resistant isolates. Based on MIC values, LYS228 (MIC, 1 μg/ml) was ≥32-fold more active against those strains than were aztreonam, ceftazidime, ceftazidime-avibactam, cefepime, and meropenem.

Advances and challenges in bacterial compound accumulation assays for drug discovery.

The identification of potent in vitro inhibitors of essential bacterial targets is relatively straightforward, however vanishingly few of these molecules have Gram-negative antibacterial potency and spectrum because of a failure to accumulate inside the bacteria. The Gram-negative bacterial cell envelope provides a formidable barrier to entry and couples with efflux pumps to prevent compound accumulation. Assays to measure the cellular permeation, efflux and accumulation of compounds in bacteria continue to be innovated and refined to guide drug discovery.

Subcellular Chemical Imaging of Antibiotics in Single Bacteria Using C-Secondary Ion Mass Spectrometry.

The inherent difficulty of discovering new and effective antibacterials and the rapid development of resistance particularly in Gram-negative bacteria, illustrates the urgent need for new methods that enable rational drug design. Here we report the development of 3D imaging cluster Time-of-Flight secondary ion mass spectrometry (ToF-SIMS) as a label-free approach to chemically map small molecules in aggregated and single Escherichia coli cells, with ∼300 nm spatial resolution and high chemical sensitivity. The feasibility of quantitative analysis was explored, and a nonlinear relationship between treatment dose and signal for tetracycline and ampicillin, two clinically used antibacterials, was observed.

Antibacterial and Solubility Optimization of Thiomuracin A.

Synthetic studies of the antimicrobial secondary metabolite thiomuracin A (1) provided access to analogues in the Northern region (C2-C10). Selective hydrolysis of the C10 amide of lead compound 2 and subsequent derivatization led to novel carbon- and nitrogen-linked analogues (e.g.

Antibacterials Developed to Target a Single Organism: Mechanisms and Frequencies of Reduced Susceptibility to the Novel Anti-Clostridium difficile Compounds Fidaxomicin and LFF571.

Clostridium difficile is the most common cause of antibacterial-associated diarrhea. Clear clinical presentation and rapid diagnostics enable targeted therapy for C. difficile infection (CDI) to start quickly.

Synthesis of ciprofloxacin dimers for evaluation of bacterial permeability in atypical chemical space.

We describe the synthesis and evaluation of a library of variably-linked ciprofloxacin dimers. These structures unify and expand on the use of fluoroquinolones as probes throughout the antibiotic literature. A dimeric analog (19) showed enhanced inhibition of its intracellular target (DNA gyrase), and translation to antibacterial activity in whole cells was demonstrated.

Multicenter, randomized clinical trial to compare the safety and efficacy of LFF571 and vancomycin for Clostridium difficile infections.

Clostridium difficile infection causes serious diarrheal disease. Although several drugs are available for treatment, including vancomycin, recurrences remain a problem. LFF571 is a semisynthetic thiopeptide with potency against C.

Pharmacokinetics of LFF571 and vancomycin in patients with moderate Clostridium difficile infections.

Clostridium difficile infection causes diarrheal disease with potentially fatal complications. Although treatments are available, including vancomycin, metronidazole, and fidaxomicin, the recurrence of disease after therapy remains a problem. LFF571 is a novel thiopeptide antibacterial that shows in vitro potency against C.

Subinhibitory concentrations of LFF571 reduce toxin production by Clostridium difficile.

LFF571 is a novel semisynthetic thiopeptide antibacterial that is undergoing investigation for safety and efficacy in patients with moderate Clostridium difficile infections. LFF571 inhibits bacterial protein synthesis by interacting with elongation factor Tu (EF-Tu) and interrupting complex formation between EF-Tu and aminoacyl-tRNA. Given this mechanism of action, we hypothesized that concentrations of LFF571 below those necessary to inhibit bacterial growth would reduce steady-state toxin levels in C.

Deletion of the β-acetoacetyl synthase FabY in Pseudomonas aeruginosa induces hypoacylation of lipopolysaccharide and increases antimicrobial susceptibility.

The β-acetoacetyl-acyl carrier protein synthase FabY is a key enzyme in the initiation of fatty acid biosynthesis in Pseudomonas aeruginosa. Deletion of fabY results in an increased susceptibility of P. aeruginosa in vitro to a number of antibiotics, including vancomycin and cephalosporins.

In vitro selection, via serial passage, of Clostridium difficile mutants with reduced susceptibility to fidaxomicin or vancomycin.

Objectives: Current treatments for Clostridium difficile infection include vancomycin, metronidazole and fidaxomicin. LFF571 is an experimental agent undergoing evaluation in humans for the treatment of moderate C. difficile infection.

A first-in-human, randomized, double-blind, placebo-controlled, single- and multiple-ascending oral dose study to assess the safety and tolerability of LFF571 in healthy volunteers.

Clostridium difficile is the leading cause of hospital-acquired infectious diarrhea. LFF571 is a novel inhibitor of the prokaryotic translation elongation factor Tu and is active against a range of bacterial species, including C. difficile.

Antibiotic optimization and chemical structure stabilization of thiomuracin A.

Synthetic studies of the antimicrobial secondary metabolite thiomuracin A (1) were initiated to improve chemical stability and physicochemical properties. Functional group modifications of 1 included removing the C2-C7 side chain, derivatizing the C84 epoxide region, and altering the C44 hydroxyphenylalanine motif. The resulting derivatives simplified and stabilized the chemical structure and were evaluated for antibacterial activity relative to 1.

Fatty acid biosynthesis in Pseudomonas aeruginosa is initiated by the FabY class of β-ketoacyl acyl carrier protein synthases.

The prototypical type II fatty acid synthesis (FAS) pathway in bacteria utilizes two distinct classes of β-ketoacyl synthase (KAS) domains to assemble long-chain fatty acids, the KASIII domain for initiation and the KASI/II domain for elongation. The central role of FAS in bacterial viability and virulence has stimulated significant effort toward developing KAS inhibitors, particularly against the KASIII domain of the β-acetoacetyl-acyl carrier protein (ACP) synthase FabH. Herein, we show that the opportunistic pathogen Pseudomonas aeruginosa does not utilize a FabH ortholog but rather a new class of divergent KAS I/II enzymes to initiate the FAS pathway.

Pseudomonas aeruginosa directly shunts β-oxidation degradation intermediates into de novo fatty acid biosynthesis.

We identified the fatty acid synthesis (FAS) initiation enzyme in Pseudomonas aeruginosa as FabY, a β-ketoacyl synthase KASI/II domain-containing enzyme that condenses acetyl coenzyme A (acetyl-CoA) with malonyl-acyl carrier protein (ACP) to make the FAS primer β-acetoacetyl-ACP in the accompanying article (Y. Yuan, M. Sachdeva, J.

Efficacy of LFF571 in a hamster model of Clostridium difficile infection.

LFF571 is a novel semisynthetic thiopeptide antibiotic with potent activity against a variety of Gram-positive pathogens, including Clostridium difficile. In vivo efficacy of LFF571 was compared to vancomycin in a hamster model of C. difficile infection (CDI).

Discovery of LFF571: an investigational agent for Clostridium difficile infection.

Clostridium difficile (C. difficile) is a Gram positive, anaerobic bacterium that infects the lumen of the large intestine and produces toxins. This results in a range of syndromes from mild diarrhea to severe toxic megacolon and death.

Antibacterial optimization of 4-aminothiazolyl analogues of the natural product GE2270 A: identification of the cycloalkylcarboxylic acids.

4-Aminothiazolyl analogues of the antibiotic natural product GE2270 A (1) were designed, synthesized, and optimized for their activity against Gram positive bacterial infections. Optimization efforts focused on improving the physicochemical properties (e.g.

4-Aminothiazolyl analogs of GE2270 A: design, synthesis and evaluation of imidazole analogs.

Imidazole analogs of the antibiotic natural product GE2270 A (1) were designed, synthesized, and evaluated for gram positive bacteria growth inhibition. A recently reported, copper-mediated synthesis was exploited to prepare 4-thiazolyl imidazole analogs of 1. The synthesis described represents a structurally complex, natural product-based application of this recently reported synthetic methodology.

4-Aminothiazolyl analogues of GE2270 A: antibacterial lead finding.

4-Aminothiazolyl analogues of the antibacterial natural product GE2270 A (1) were designed, synthesized, and evaluated for gram positive bacteria growth inhibition. The aminothiazole-based chemical template was evaluated for chemical stability, and its decomposition revealed a novel, structurally simplified, des-thiazole analogue of 1. Subsequent stabilization of the 4-aminothiazolyl functional motif was achieved and initial structure activity relationships defined.