Thienopyrrole acetic acids as antagonists of the CRTH2 receptor

The bioisosteric replacement of the indole core of CRTH2 antagonists using thienopyrroles was investigated, resulting in potent antagonists with good selectivity over DP1. Early ADME/PK assessment of this chemotype demonstrated bioavailability in mice.     

Specific versus nonspecific binding of cationic PNAs to duplex DNA

Although peptide nucleic acids (PNAs) are neutral by themselves, they are usually appended with positively charged lysine residues to increase their solubility and binding affinity for nucleic acid targets. Thus obtained cationic PNAs very effectively interact with the designated duplex DNA targets in a sequence-specific manner forming strand-invasion complexes. We report on the study of the nonspecific effects in the kinetics of formation of sequence-specific PNA-DNA complexes. We find that in a typical range of salt concentrations used when working with strand-invading PNAs (10-20 mM NaCl) the PNA binding rates essentially do not depend on the presence of nontarget DNA in the reaction mixture. However, at lower salt concentrations (<10 mM NaCl), the rates of PNA binding to DNA targets are significantly slowed down by the excess of unrelated DNA. This effect of nontarget DNA arises from depleting the concentration of free PNA capable of interacting with DNA target due to adhesion of positively charged PNA molecules on the negatively charged DNA duplex. As expected, the nonspecific electrostatic effects are more pronounced for more charged PNAs. We propose a simple model quantitatively describing all major features of the observed phenomenon. This understanding is important for design of and manipulation with the DNA-binding polycationic ligands in general and PNA-based drugs in particular.     

The Role of a Novel Auxiliary Pocket in Bacterial Phenylalanyl-tRNA Synthetase Druggability

The antimicrobial activity of phenyl-thiazolylurea-sulfonamides against Staphylococcus aureus PheRS are dependent upon phenylalanine levels in the extracellular fluids. Inhibitor efficacy in animal models of infection is substantially diminished by dietary phenylalanine intake, thereby reducing the perceived clinical utility of this inhibitor class. The search for novel antibacterial compounds against Gram-negative pathogens led to a re-evaluation of this phenomenon, which is shown here to be unique to S. aureus. Inhibition of macromolecular syntheses and characterization of novel resistance mutations in Escherichia coli demonstrate that antimicrobial activity of phenyl-thiazolylurea-sulfonamides is mediated by PheRS inhibition, validating this enzyme as a viable drug discovery target for Gram-negative pathogens. A search for novel inhibitors of PheRS yielded three novel chemical starting points. NMR studies were used to confirm direct target engagement for phenylalanine-competitive hits. The crystallographic structure of Pseudomonas aeruginosa PheRS defined the binding modes of these hits and revealed an auxiliary hydrophobic pocket that is positioned adjacent to the phenylalanine binding site. Three viable inhibitor-resistant mutants were mapped to this pocket, suggesting that this region is a potential liability for drug discovery.