ETX2514 is a broad-spectrum ß-lactamase inhibitor for the treatment of drug-resistant Gram-negative bacteria including Acinetobacter baumannii.

Multidrug-resistant (MDR) bacterial infections are a serious threat to public health. Among the most alarming resistance trends is the rapid rise in the number and diversity of ß-lactamases, enzymes that inactivate ß-lactams, a class of antibiotics that has been a therapeutic mainstay for decades. Although several new ß-lactamase inhibitors have been approved or are in clinical trials, their spectra of activity do not address MDR pathogens such as Acinetobacter baumannii. This report describes the rational design and characterization of expanded-spectrum serine ß-lactamase inhibitors that potently inhibit clinically relevant class A, C and D ß-lactamases and penicillin-binding proteins, resulting in intrinsic antibacterial activity against Enterobacteriaceae and restoration of ß-lactam activity in a broad range of MDR Gram-negative pathogens. One of the most promising combinations is sulbactam-ETX2514, whose potent antibacterial activity, in vivo efficacy against MDR A. baumannii infections and promising preclinical safety demonstrate its potential to address this significant unmet medical need.

Selective inhibitors of bacterial t-RNA-(N(1)G37) methyltransferase (TrmD) that demonstrate novel ordering of the lid domain.

The tRNA-(N(1)G37) methyltransferase (TrmD) is essential for growth and highly conserved in both Gram-positive and Gram-negative bacterial pathogens. Additionally, TrmD is very distinct from its human orthologue TRM5 and thus is a suitable target for the design of novel antibacterials. Screening of a collection of compound fragments using Haemophilus influenzae TrmD identified inhibitory, fused thieno-pyrimidones that were competitive with S-adenosylmethionine (SAM), the physiological methyl donor substrate. Guided by X-ray cocrystal structures, fragment 1 was elaborated into a nanomolar inhibitor of a broad range of Gram-negative TrmD isozymes. These compounds demonstrated no activity against representative human SAM utilizing enzymes, PRMT1 and SET7/9. This is the first report of selective, nanomolar inhibitors of TrmD with demonstrated ability to order the TrmD lid in the absence of tRNA.

Novel topoisomerase inhibitors: microbiological characterisation and in vivo efficacy of pyrimidines.

Pyrimidine compounds were identified as inhibitors of DNA topoisomerase IV through high-throughput screening. This study was designed to exemplify the in vitro activity of the pyrimidines against Gram-positive and Gram-negative microorganisms, to reveal the mode of action of these compounds and to demonstrate their in vivo efficacy. Frequencies of resistance to pyrimidines among Staphylococcus aureus and Streptococcus pneumoniae were <10(-10) at four times their minimum inhibitory concentrations (MICs). These compounds exhibited a dual mode of action through inhibition of the ParE subunit of DNA topoisomerase IV as well as the GyrB subunit of DNA gyrase, a homologue of DNA topoisomerase IV. Pyrimidines were shown to have MIC(90) values (MIC that inhibited 90% of the strains tested) of ≤2 mg/L against Gram-positive pathogens, including meticillin-resistant S. aureus, quinolone- and meticillin-resistant S. aureus, vancomycin-resistant enterococci, penicillin-non-susceptible S. pneumoniae and Streptococcus pyogenes, and MIC(90) values of 2- to >16 mg/L and ≤0.5 mg/L against the Gram-negative pathogens Haemophilus influenzae and Moraxella catarrhalis, respectively. The pyrimidines were bactericidal and exhibited a ca. 1000-fold reduction of the bacterial counts at 300 mg/kg in a S. pneumoniae lung infection model. The microbiological properties and in vivo efficacy of pyrimidines underscore their potential as candidates for the treatment of soft-tissue infections and hospital-acquired pneumonia.

A high-throughput-compatible fluorescence anisotropy-based assay for competitive inhibitors of Escherichia coli UDP-N-acetylglucosamine acyltransferase (LpxA).

LpxA, the first enzyme in the biosynthetic pathway for the Lipid A component of the outer membrane lipopolysaccharide in Gram-negative bacteria, is a potential target for novel antibacterial drug discovery. A fluorescence polarization assay was developed to facilitate high-throughput screening for competitive inhibitors of LpxA. The assay detects displacement of a fluorescently labeled peptide inhibitor, based on the previously reported inhibitor peptide 920, by active site ligands. The affinity of the fluorescent ligand was increased ~10-fold by acyl carrier protein (ACP). Competition with peptide binding was observed with UDP-N-acetylglucosamine (IC(50) ~6 mM), UDP-3-O-(R-3-hydroxymyristoyl)-N-acetylglucosamine (IC(50) ~200 nM), and DL-3-hydroxymyristic acid (IC(50) ~50 µM) and peptide 920 (IC(50) ~600 nM). The IC(50)s were not significantly affected by the presence of ACP.