Chemical Optimization of Selective Pseudomonas aeruginosa LasB Elastase Inhibitors and Their Impact on LasB-Mediated Activation of IL-1ß in Cellular and Animal Infection Models.

LasB elastase is a broad-spectrum exoprotease and a key virulence factor of Pseudomonas aeruginosa, a major pathogen causing lung damage and inflammation in acute and chronic respiratory infections. Here, we describe the chemical optimization of specific LasB inhibitors with druglike properties and investigate their impact in cellular and animal models of P. aeruginosa infection. Competitive inhibition of LasB was demonstrated through structural and kinetic studies. In vitro LasB inhibition was confirmed with respect to several host target proteins, namely, elastin, IgG, and pro-IL-1ß. Furthermore, inhibition of LasB-mediated IL-1ß activation was demonstrated in macrophage and mouse lung infection models. In mice, intravenous administration of inhibitors also resulted in reduced bacterial numbers at 24 h. These highly potent, selective, and soluble LasB inhibitors constitute valuable tools to study the proinflammatory impact of LasB in P. aeruginosa infections and, most importantly, show clear potential for the clinical development of a novel therapy for life-threatening respiratory infections caused by this opportunistic pathogen.

Tetrahydrofuran-Based Transient Receptor Potential Ankyrin 1 (TRPA1) Antagonists: Ligand-Based Discovery, Activity in a Rodent Asthma Model, and Mechanism-of-Action via Cryogenic Electron Microscopy.

Transient receptor potential ankyrin 1 (TRPA1) is a nonselective calcium-permeable ion channel highly expressed in the primary sensory neurons functioning as a polymodal sensor for exogenous and endogenous stimuli and has generated widespread interest as a target for inhibition due to its implication in neuropathic pain and respiratory disease. Herein, we describe the optimization of a series of potent, selective, and orally bioavailable TRPA1 small molecule antagonists, leading to the discovery of a novel tetrahydrofuran-based linker. Given the balance of physicochemical properties and strong in vivo target engagement in a rat AITC-induced pain assay, compound 20 was progressed into a guinea pig ovalbumin asthma model where it exhibited significant dose-dependent reduction of inflammatory response. Furthermore, the structure of the TRPA1 channel bound to compound 21 was determined via cryogenic electron microscopy to a resolution of 3 Å, revealing the binding site and mechanism of action for this class of antagonists.

TRPA1 modulation by piperidine carboxamides suggests an evolutionarily conserved binding site and gating mechanism.

The transient receptor potential ankyrin 1 (TRPA1) channel functions as an irritant sensor and is a therapeutic target for treating pain, itch, and respiratory diseases. As a ligand-gated channel, TRPA1 can be activated by electrophilic compounds such as allyl isothiocyanate (AITC) through covalent modification or activated by noncovalent agonists through ligand binding. However, how covalent modification leads to channel opening and, importantly, how noncovalent binding activates TRPA1 are not well-understood. Here we report a class of piperidine carboxamides (PIPCs) as potent, noncovalent agonists of human TRPA1. Based on their species-specific effects on human and rat channels, we identified residues critical for channel activation; we then generated binding modes for TRPA1-PIPC interactions using structural modeling, molecular docking, and mutational analysis. We show that PIPCs bind to a hydrophobic site located at the interface of the pore helix 1 (PH1) and S5 and S6 transmembrane segments. Interestingly, this binding site overlaps with that of known allosteric modulators, such as A-967079 and propofol. Similar binding sites, involving π-helix rearrangements on S6, have been recently reported for other TRP channels, suggesting an evolutionarily conserved mechanism. Finally, we show that for PIPC analogs, predictions from computational modeling are consistent with experimental structure-activity studies, thereby suggesting strategies for rational drug design.

Optimization of sphingosine-1-phosphate-1 receptor agonists: effects of acidic, basic, and zwitterionic chemotypes on pharmacokinetic and pharmacodynamic profiles.

The efficacy of the recently approved drug fingolimod (FTY720) in multiple sclerosis patients results from the action of its phosphate metabolite on sphingosine-1-phosphate S1P1 receptors, while a variety of side effects have been ascribed to its S1P3 receptor activity. Although S1P and phospho-fingolimod share the same structural elements of a zwitterionic headgroup and lipophilic tail, a variety of chemotypes have been found to show S1P1 receptor agonism. Here we describe a study of the tolerance of the S1P1 and S1P3 receptors toward bicyclic heterocycles of systematically varied shape and connectivity incorporating acidic, basic, or zwitterionic headgroups. We compare their physicochemical properties, their performance in in vitro and in vivo pharmacokinetic models, and their efficacy in peripheral lymphocyte lowering. The campaign resulted in the identification of several potent S1P1 receptor agonists with good selectivity vs S1P3 receptors, efficacy at <1 mg/kg oral doses, and developability properties suitable for progression into preclinical development.

Studies on the synthesis of the ABC rings of (+/-)-hexacyclinic acid.

A synthesis of the ABC-rings of the polyketide natural product hexacyclinic acid has been achieved. The B-ring was formed first via an intramolecular ester-tethered Diels-Alder reaction, and the A-ring was annulated to this by means of a SmI(2) mediated reductive 5-exo-trig cyclization of a samarium-ketyl radical onto a vinyl group. Finally, the C-ring was closed using olefin metathesis. Interestingly, use of enyne metathesis resulted in the synthesis of a more functionalized 5-membered C-ring in a model system, but an undesired 6-membered C-ring in the actual system. An investigation of this change in selectivity is discussed.

A racemic synthesis of an AB-ring system of hexacyclinic acid.

[structure: see text] An AB-ring system of the polyketide natural product hexacyclinic acid has been synthesized in racemic form. The key steps were an intramolecular Diels-Alder cyclization of an ester tethered 1,3-nonadiene-8-yne, which generated the B-ring, and a samarium diiodide mediated reductive annulation, which was used to form the A-ring.

Novel enantioselective synthesis of 1,3-butadien-2-ylmethanols via tandem alkylbromide-epoxide vinylations using dimethylsulfonium methylide.

[reaction: see text] The treatment of chiral trans-disubstituted and trisubstituted 2,3-epoxy-1-bromides with an excess of dimethylsulfonium methylide 1 affords the corresponding 1,3-butadien-2-ylmethanols in good to excellent yields via a double one-carbon homologation.