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(1H)-ones, exemplified by 34, that inhibit bacterial DNA gyrase and topoisomerase IV and display potent activity against ciprofloxacin-resistant Gram-negative pathogens. X-ray crystallography reveals that 34 occupies the classical quinolone binding site in the topoisomerase IV-DNA cleavage complex but does not form significant contacts with residues in the quinolone resistance determining region

Optimization of Physicochemical Properties and Safety Profile of Novel Bacterial Topoisomerase Type II Inhibitors (NBTIs) with activity against Pseudomonas aeruginosa

Type II bacterial topoisomerases are well validated targets for antimicrobial chemotherapy. Novel bacterial type II topoisomerase inhibitors (NBTIs) of these targets are of interest for the development of new antibacterial agents that are not impacted by target-mediated cross-resistance with fluoroquinolones. We now disclose the optimization of a class of NBTIs towards Gram-negative pathogens, especially against drug-resistant Pseudomonas aeruginosa. Physicochemical properties (pKa and logD) were optimized for activity against P. aeruginosa and for reduced inhibition of the hERG channel. The optimized analogs 9g and 9i displayed potent antibacterial activity against P. aeruginosa, and a significantly improved hERG profile over previously reported analogs. 9g showed an improved QT profile in in vivo models and lower clearance in rat over earlier compounds. The compounds show promise for the development of new antimicrobial agents against drug-resistant Pseudomonas aeruginosa

Scale up synthesis of IID572: A new β-lactamase inhibitor

The new potentially best-in-class β-lactamase inhibitor IID572 was discovered by a late stage functionalization approach. An alternative scalable synthesis was developed to satisfy the short-term need for tox studies. The two key features were an intramolecular azomethine ylide [2+3] cycloaddition that allowed the quick formation of molecular complexity from cheap starting material and an efficient enzymatic resolution that resulted in high optical purity of a key intermediate

Impact of inducible blaDHA-1 on susceptibility of Klebsiella pneumoniae clinical isolates to LYS228 and identification of chromosomal mpl mutations mediating upregulation of plasmid borne DHA-1 expression

A panel of twenty three K. pneumoniae clinical isolates harboring plasmid-borne inducible β-lactamase DHA-1 (blaDHA-1) exhibited a wide range of susceptibilities to the novel monobactam LYS228 (MIC range 0.125 - >64 µg/mL). This panel was considerably less susceptible (MIC ≥ 8 µg/mL for 9/23 of the isolates) than was a previously reported Enterobacteriaceae strain panel comprised of 88 isolates expressing ESBLs, KPCs and MBL (MIC90 of 2 µg/mL), suggesting that blaDHA-1 can impact LYS228 susceptibility in clinical isolates. Mutants with decreased in vitro susceptibility to LYS228 and upregulated expression of blaDHA-1 were selected in vitro from K. pneumoniae blaDHA-1 strains. These had mutations in the chromosomal peptidoglycan recycling gene mpl. Pre-existing mpl mutations were identified among our clinical strains and these had strongly upregulated expression of blaDHA-1 and reduced susceptibility to LYS228. Therefore we have identified a novel mechanism of blaDHA upregulation in K. pneumoniae clinical isolates, furthering our understanding of the factors underlying β-lactam resistance and the variability in β-lactam susceptibility among these clinical strains

George Tucker photograph, Ports Down Fair, 1954.

J. Noyce's Gallopers horse truck photographed 15 April 1954. Built 1952, lettered 1953, the offside has different wording

In vitro activity of LYS228, a novel monobactam antibiotic, against multidrug-resistant enterobacteriaceae

LYS228 is a novel monobactam with potent activity against Enterobacteriaceae. LYS228 is stable to metallo-β-lactamases (MBLs) and serine carbapenemases, including Klebsiella pneumoniae carbapenemases (KPCs), resulting in potency against the majority of extended-spectrum β-lactamase (ESBL)-producing and carbapenemresistant Enterobacteriaceae strains tested. Overall, LYS228 demonstrated potent activity against 271 Enterobacteriaceae strains, including multidrug-resistant isolates. Based on MIC90 values, LYS228 (MIC90, 1 μg/ml) was ≥32-fold more active against those strains than were aztreonam, ceftazidime, ceftazidime-avibactam, cefepime, and meropenem. The tigecycline MIC90 was 4 μg/ml against the strains tested. Against Enterobacteriaceae isolates expressing ESBLs (n = 37) or displaying carbapenem resistance (n = 77), LYS228 had MIC90 values of 1 and 4 μg/ml, respectively. LYS228 exhibited potent bactericidal activity, as indicated by low minimal bactericidal concentration (MBC) to MIC ratios (MBC/MIC ratios of ≤4) against 97.4% of the Enterobacteriaceae strains tested (264/271 strains). In time-kill studies, LYS228 consistently achieved reductions in CFU per milliliter of 3 log10 units (≥99.9% killing) at concentrations ≥4× MIC for Escherichia coli and K. pneumoniae reference strains, as well as isolates encoding TEM-1, SHV-1, CTX-M-14, CTX-M-15, KPC-2, KPC-3, and NDM-1 β-lactamases

In Vitro Activity of LYS228, a Novel Monobactam Antibiotic, against Multidrug-resistant Enterobacteriaceae

LYS228 is a novel monobactam with potent activity against Enterobacteriaceae. LYS228 is stable to metallo-β-lactamases (MBLs) and serine carbapenemases, including Klebsiella pneumoniae carbapenemases (KPCs), resulting in potency against the majority of extended spectrum β-lactamase (ESBL)-producing and carbapenem-resistant Enterobacteriaceae (CRE) strains tested. Overall, LYS228 demonstrated potent activity against 271 Enterobacteriaceae strains, including multidrug-resistant isolates. Based upon MIC90 values, LYS228 (MIC90= 1 μg/mL) was ≥32-fold more active against these strains than were aztreonam, ceftazidime, ceftazidime/avibactam, cefepime, and meropenem. The MIC90 value for tigecyline was 4 μg/mL against the strains tested. Against Enterobacteriaceae isolates expressing ESBLs (N=37) or displaying carbapenem resistance (N=77), LYS228 had MIC90 values of 1 and 4 µg/mL, respectively. LYS228 exhibited potent bactericidal activity as indicated by low MBC to MIC ratios (≤4) against 97.4% (264/271) of the Enterobacteriaceae strains tested. In time-kill studies, LYS228 consistently achieved 3-log10 reduction in colony-forming units (CFU)/mL (≥99.9% killing) at concentrations ≥4X the MIC for E. coli and K. pneumoniae reference strains as well as isolates encoding TEM-1, SHV-1, CTX-M-14, CTX-M-15, KPC-2, KPC-3 and NDM-1 β-lactamases