4 research outputs found
Data_Sheet_1_Identification of a Novel Polyamine Scaffold With Potent Efflux Pump Inhibition Activity Toward Multi-Drug Resistant Bacterial Pathogens.PDF
<p>We have previously reported the use of combinatorial chemistry to identify broad-spectrum antibacterial agents. Herein, we extend our analysis of this technology toward the discovery of anti-resistance molecules, focusing on efflux pump inhibitors. Using high-throughput screening against multi-drug resistant Pseudomonas aeruginosa, we identified a polyamine scaffold that demonstrated strong efflux pump inhibition without possessing antibacterial effects. We determined that these molecules were most effective with an amine functionality at R1 and benzene functionalities at R2 and R3. From a library of 188 compounds, we studied the properties of 5 lead agents in detail, observing a fivefold to eightfold decrease in the 90% effective concentration of tetracycline, chloramphenicol, and aztreonam toward P. aeruginosa isolates. Additionally, we determined that our molecules were not only active toward P. aeruginosa, but toward Acinetobacter baumannii and Staphylococcus aureus as well. The specificity of our molecules to efflux pump inhibition was confirmed using ethidium bromide accumulation assays, and in studies with strains that displayed varying abilities in their efflux potential. When assessing off target effects we observed no disruption of bacterial membrane polarity, no general toxicity toward mammalian cells, and no inhibition of calcium channel activity in human kidney cells. Finally, combination treatment with our lead agents engendered a marked increase in the bactericidal capacity of tetracycline, and significantly decreased viability within P. aeruginosa biofilms. As such, we report a unique polyamine scaffold that has strong potential for the future development of novel and broadly active efflux pump inhibitors targeting multi-drug resistant bacterial infections.</p
Combinatorial Libraries As a Tool for the Discovery of Novel, Broad-Spectrum Antibacterial Agents Targeting the ESKAPE Pathogens
Mixture based synthetic combinatorial
libraries offer a tremendous
enhancement for the rate of drug discovery, allowing the activity
of millions of compounds to be assessed through the testing of exponentially
fewer samples. In this study, we used a scaffold-ranking library to
screen 37 different libraries for antibacterial activity against the
ESKAPE pathogens. Each library contained between 10000 and 750000
structural analogues for a total of >6 million compounds. From
this,
we identified a bis-cyclic guanidine library that displayed strong
antibacterial activity. A positional scanning library for these compounds
was developed and used to identify the most effective functional groups
at each variant position. Individual compounds were synthesized that
were broadly active against all ESKAPE organisms at concentrations
<2 μM. In addition, these compounds were bactericidal, had
antibiofilm effects, showed limited potential for the development
of resistance, and displayed almost no toxicity when tested against
human lung cells and erythrocytes. Using a murine model of peritonitis,
we also demonstrate that these agents are highly efficacious in vivo
Scaffold Ranking and Positional Scanning Utilized in the Discovery of nAChR-Selective Compounds Suitable for Optimization Studies
Nicotine
binds to nicotinic acetylcholine receptors (nAChR), which can exist
as many different subtypes. The α4β2 nAChR is the most
prevalent subtype in the brain and possesses the most evidence linking
it to nicotine seeking behavior. Herein we report the use of mixture
based combinatorial libraries for the rapid discovery of a series
of α4β2 nAChR selective compounds. Further chemistry optimization
provided compound <b>301</b>, which was characterized as a selective
α4β2 nAChR antagonist. This compound displayed no agonist
activity but blocked nicotine-induced depolarization of HEK cells
with an IC<sub>50</sub> of approximately 430 nM. <b>301</b> demonstrated
nearly 500-fold selectivity for binding and 40-fold functional selectivity
for α4β2 over α3β4 nAChR. In total over 5
million compounds were assessed through the use of just 170 samples
in order to identify a series of structural analogues suitable for
future optimization toward the goal of developing clinically relevant
smoking cessation medications
Highly Selective and Potent α4β2 nAChR Antagonist Inhibits Nicotine Self-Administration and Reinstatement in Rats
The
α4β2 nAChR is the most predominant subtype in the
brain and is a well-known culprit for nicotine addiction. Previously
we presented a series of α4β2 nAChR selective compounds
that were discovered from a mixture-based positional-scanning combinatorial
library. Here we report further optimization identified highly potent
and selective α4β2 nAChR antagonists <b>5</b> (AP-202)
and <b>13</b> (AP-211). Both compounds are devoid of in vitro
agonist activity and are potent inhibitors of epibatidine-induced
changes in membrane potential in cells containing α4β2
nAChR, with IC<sub>50</sub> values of approximately 10 nM, but are
weak agonists in cells containing α3β4 nAChR. In vivo
studies show that <b>5</b> can significantly reduce operant
nicotine self-administration and nicotine relapse-like behavior in
rats at doses of 0.3 and 1 mg/kg. The pharmacokinetic data also indicate
that <b>5</b>, via sc administration, is rapidly absorbed into
the blood, reaching maximal concentration within 10 min with a half-life
of less than 1 h