Thiophene antibacterials that allosterically stabilize DNA-cleavage complexes with DNA gyrase.

A paucity of novel acting antibacterials is in development to treat the rising threat of antimicrobial resistance, particularly in Gram-negative hospital pathogens, which has led to renewed efforts in antibiotic drug discovery. Fluoroquinolones are broad-spectrum antibacterials that target DNA gyrase by stabilizing DNA-cleavage complexes, but their clinical utility has been compromised by resistance. We have identified a class of antibacterial thiophenes that target DNA gyrase with a unique mechanism of action and have activity against a range of bacterial pathogens, including strains resistant to fluoroquinolones. Although fluoroquinolones stabilize double-stranded DNA breaks, the antibacterial thiophenes stabilize gyrase-mediated DNA-cleavage complexes in either one DNA strand or both DNA strands. X-ray crystallography of DNA gyrase-DNA complexes shows the compounds binding to a protein pocket between the winged helix domain and topoisomerase-primase domain, remote from the DNA. Mutations of conserved residues around this pocket affect activity of the thiophene inhibitors, consistent with allosteric inhibition of DNA gyrase. This druggable pocket provides potentially complementary opportunities for targeting bacterial topoisomerases for antibiotic development.

Structure-guided design of antibacterials that allosterically inhibit DNA gyrase.

A series of DNA gyrase inhibitors were designed based on the X-ray structure of a parent thiophene scaffold with the objective to improve biochemical and whole-cell antibacterial activity, while reducing cardiac ion channel activity. The binding mode and overall design hypothesis of one series was confirmed with a co-crystal structure with DNA gyrase. Although some analogs retained both biochemical activity and whole-cell antibacterial activity, we were unable to significantly improve the activity of the series and analogs retained activity against the cardiac ion channels, therefore we stopped optimization efforts.

A specific and direct comparison of the trifluoromethyl and pentafluoro sulfanyl groups on the selective dopamine D(3) antagonist 3-(3-{[4-methyl-5-(4-methyl-1,3-oxazol-5-yl)-4H-1,2,4-triazol-3-yl]thio}propyl)-1-phenyl-3-azabicyclo[3.1.0]hexane template.

A direct and specific comparison of a trifluoromethyl group with the corresponding pentafluorosulfanyl group is made in terms of primary affinity and pharmacokinetic properties.

Synthesis and preliminary biological characterization of new semisynthetic derivatives of ramoplanin.

Ramoplanin is a glycolipodepsipeptide antibiotic active against Gram-positive bacteria including vancomycin-resistant enterococci. Ramoplanin inhibits bacterial cell wall biosynthesis by a mechanism different from that of glycopeptides and hence does not show cross-resistance with these antibiotics. The systemic use of ramoplanin has been so far prevented because of its low local tolerability when injected intravenously. To overcome this problem, the fatty acid side chain of ramoplanin was selectively removed and replaced with a variety of different carboxylic acids. Many of the new ramoplanin derivatives showed antimicrobial activity similar to that of the natural precursor coupled with a significantly improved local tolerability. Among them the derivative in which the 2-methylphenylacetic acid has replaced the di-unsaturated fatty acid side chain (48) was selected as the most interesting compound and submitted to further in vitro and in vivo characterization studies.

1,2,4-triazol-3-yl-thiopropyl-tetrahydrobenzazepines: a series of potent and selective dopamine D(3) receptor antagonists.

The discovery of new highly potent and selective dopamine D3 receptor antagonists has recently permitted characterization of the role of the dopamine D3 receptor in a wide range of preclinical animal models. A novel series of 1,2,4-triazol-3-yl-thiopropyl-tetrahydrobenzazepines demonstrating a high level of D3 affinity and selectivity with an excellent pharmacokinetic profile is reported here. In particular, the pyrazolyl derivative 35 showed good oral bioavailability and brain penetration associated with high potency and selectivity in vitro. In vivo characterization of 35 confirmed that this compound blocks the expression of nicotine- and cocaine-conditioned place preference in the rat, prevents nicotine-triggered reinstatement of nicotine-seeking behavior in the rat, reduces oral operant alcohol self-administration in the mouse, increases extracellular levels of acetylcholine in the rat medial prefrontal cortex, and potentiates the amplitude of the relative cerebral blood volume response to d-amphetamine in a regionally specific manner in the rat brain.

Triazolyl azabicyclo[3.1.0]hexanes: A class of potent and selective dopamine D(3) receptor antagonists.

Herein we report a detailed description of the structure-activity relationships for a novel series of "C-linked" 1,2,4-triazolylazabicyclo[3.1.0]hexanes. These derivatives are endowed with very high in vitro affinity and selectivity for the dopamine D(3) receptor. An optimization with respect to undesired affinity toward the hERG potassium channel is also reported. Members of this compound series also show excellent in vitro and in vivo pharmacokinetic properties.

1,2,4-Triazolyl azabicyclo[3.1.0]hexanes: a new series of potent and selective dopamine D(3) receptor antagonists.

The discovery of new highly potent and selective dopamine (DA) D(3) receptor antagonists has recently allowed the characterization of the DA D(3) receptor in a range of preclinical animal models of drug addiction. A novel series of 1,2,4-triazol-3-yl-azabicyclo[3.1.0]hexanes, members of which showed a high affinity and selectivity for the DA D(3) receptor and excellent pharmacokinetic profiles, is reported here. Members of a group of derivatives from this series showed good oral bioavailability and brain penetration and very high in vitro affinity and selectivity for the DA D(3) receptor, as well as high in vitro potency for antagonism at this receptor. Several members of this series also significantly attenuate the expression of conditioned place preference (CPP) to nicotine and cocaine.

6-(3,4-dichlorophenyl)-1-[(methyloxy)methyl]-3-azabicyclo[4.1.0]heptane: a new potent and selective triple reuptake inhibitor.

A pharmacophore model for triple reuptake inhibitors and the new class of 1-(aryl)-6-[alkoxyalkyl]-3-azabicyclo[3.1.0]hexanes were recently reported. Further investigation in this area led to the identification of a new series of potent and selective triple reuptake inhibitors endowed with good developability characteristics. Excellent bioavailability and brain penetration are associated with this series of 6-(3,4-dichlorophenyl)-1-[(methyloxy)methyl]-3-azabicyclo[4.1.0]heptanes together with high in vitro potency and selectivity at SERT, NET, and DAT. In vivo microdialysis experiments in different animal models and receptor occupancy studies in rat confirmed that derivative 17 showed an appropriate profile to guarantee further progression of the compound.

1-(Aryl)-6-[alkoxyalkyl]-3-azabicyclo[3.1.0]hexanes and 6-(aryl)-6-[alkoxyalkyl]-3-azabicyclo[3.1.0]hexanes: a new series of potent and selective triple reuptake inhibitors.

The discovery of new highly potent and selective triple reuptake inhibitors is reported. The new classes of 1-(aryl)-6-[alkoxyalkyl]-3-azabicyclo[3.1.0]hexanes and 6-(aryl)-6-[alkoxyalkyl]-3-azabicyclo[3.1.0]hexanes are described together with detailed SAR. Appropriate decoration of the scaffolds was achieved with the help of a triple reuptake inhibitor pharmacophore model detailed here. Selected derivatives showed good oral bioavailability (>30%) and brain penetration (B/B > 4) in rats associated with high in vitro potency and selectivity at SERT, NET, and DAT. Among these compounds, microdialysis and in vivo experiments confirm that derivative 15 has an appropriate developability profile to be considered for further progression.

Isoindolone derivatives, a new class of 5-HT2C antagonists: synthesis and biological evaluation.

Two independent approaches resulted in the identification of a series of isoindolone derivatives as potent and selective 5-HT2C antagonists. From a Medicinal Chemistry perspective this template was considered interesting as it allowed the incorporation of the carbon-carbon double bond of an earlier dihydropyrrolone series in an aromatic system within a comparatively simple and compact motif. Additionally an in silico screening approach of the corporate database using a 5-HT2C pharmacophore model resulted in the identification of a related structure containing this template. The strategy used to optimise potency at the target receptor and to improve the pharmacokinetic profile is described, resulting in molecules combining high potency with good selectivity and oral bioavailability.

Diaryl substituted pyrrolidinones and pyrrolones as 5-HT2C inhibitors: synthesis and biological evaluation.

Within the continuous quest for the discovery of novel compounds able to treat anxiety and depression, the generation of a pharmacophore model for 5-HT2C receptor antagonists and the discovery of a new class of potent and selective 5-HT2C molecules are reported.