Benzo-fused Lactams from a Diversity-oriented Synthesis (DOS) Library as Inhibitors of Scavenger Receptor BI (SR-BI)-mediated Lipid Uptake

We report a new series of 8-membered benzo-fused lactams that inhibit cellular lipid uptake from HDL particles mediated by Scavenger Receptor, Class B, Type I (SR-BI). The series was identified via a high-throughput screen of the National Institutes of Health Molecular Libraries Small Molecule Repository (NIH MLSMR), measuring the transfer of the fluorescent lipid DiI from HDL particles to CHO cells overexpressing SR-BI. The series is part of a previously reported diversity-oriented synthesis (DOS) library prepared via a build-couple-pair approach. Detailed structure–activity relationship (SAR) studies were performed with a selection of the original library, as well as additional analogs prepared via solution phase synthesis. These studies demonstrate that the orientation of the substituents on the aliphatic ring have a critical effect on activity. Additionally, a lipophilic group is required at the western end of the molecule, and a northern hydroxyl group and a southern sulfonamide substituent also proved to be optimal. Compound 2p was found to possess a superior combination of potency (av IC50 = 0.10 μM) and solubility (79 μM in PBS), and it was designated as probe ML312

Discovery of Bisamide-heterocycles as Inhibitors of Scavenger Receptor BI (SR-BI)-mediated Lipid Uptake

A new series of potent inhibitors of cellular lipid uptake from HDL particles mediated by scavenger receptor, class B, type I (SR-BI) was identified. The series was identified via a high-throughput screen of the National Institutes of Health Molecular Libraries Small Molecule Repository (NIH MLSMR) that measured the transfer of the fluorescent lipid DiI from HDL particles to CHO cells overexpressing SR-BI. The series is characterized by a linear peptidomimetic scaffold with two adjacent amide groups, as well as an aryl-substituted heterocycle. Analogs of the initial hit were rapidly prepared via Ugi 4-component reaction, and select enantiopure compounds were prepared via a stepwise sequence. Structure–activity relationship (SAR) studies suggest an oxygenated arene is preferred at the western end of the molecule, as well as highly lipophilic substituents on the central and eastern nitrogens. Compound 5e, with (R)-stereochemistry at the central carbon, was designated as probe ML279. Mechanistic studies indicate that ML279 stabilizes the interaction of HDL particles with SR-BI, and its effect is reversible. It shows good potency (IC50 = 17 nM), is non-toxic, plasma stable, and has improved solubility over our alternative probe ML278

Indolinyl-Thiazole Based Inhibitors of Scavenger Receptor-BI (SR-BI)-Mediated Lipid Transport

A potent class of indolinyl-thiazole based inhibitors of cellular lipid uptake mediated by scavenger receptor, class B, type I (SR-BI) was identified via a high-throughput screen of the National Institutes of Health Molecular Libraries Small Molecule Repository (NIH MLSMR) in an assay measuring the uptake of the fluorescent lipid DiI from HDL particles. This class of compounds is represented by ML278 (17–11), a potent (average IC50 = 6 nM) and reversible inhibitor of lipid uptake via SR-BI. ML278 is a plasma-stable, noncytotoxic probe that exhibits moderate metabolic stability, thus displaying improved properties for in vitro and in vivo studies. Strikingly, ML278 and previously described inhibitors of lipid transport share the property of increasing the binding of HDL to SR-BI, rather than blocking it, suggesting there may be similarities in their mechanisms of action

Piperazinyl quinolines as chemosensitizers to increase fluconazole susceptibility of Candida albicans clinical isolates

The effectiveness of the potent antifungal drug fluconazole is being compromised by the rise of drug-resistant fungal pathogens. While inhibition of Hsp90 or calcineurin can reverse drug resistance in Candida, such inhibitors also impair the homologous human host protein and fungal-selective chemosensitizers remain rare. The MLPCN library was screened to identify compounds that selectively reverse fluconazole resistance in a Candida albicans clinical isolate, while having no antifungal activity when administered as a single agent. A piperazinyl quinoline was identified as a new small-molecule probe (ML189) satisfying these criteria.National Institutes of Health (U.S.) (1 R03 MH086456-01

Diversity-Oriented Synthesis Yields a Novel Lead for the Treatment of Malaria

Here, we describe the discovery of a novel antimalarial agent using phenotypic screening of Plasmodium falciparum asexual blood-stage parasites. Screening a novel compound collection created using diversity-oriented synthesis (DOS) led to the initial hit. Structure–activity relationships guided the synthesis of compounds having improved potency and water solubility, yielding a subnanomolar inhibitor of parasite asexual blood-stage growth. Optimized compound 27 has an excellent off-target activity profile in erythrocyte lysis and HepG2 assays and is stable in human plasma. This compound is available via the molecular libraries probe production centers network (MLPCN) and is designated ML238.Chemistry and Chemical Biolog

High-Throughput Screen in Cryptococcus neoformans Identifies a Novel Molecular Scaffold That Inhibits Cell Wall Integrity Pathway Signaling

Cryptococcus neoformans is one of the most important human fungal pathogens; however, no new therapies have been developed in over 50 years. Fungicidal activity is crucially important for an effective anticryptococal agent and, therefore, we screened 361,675 molecules against C. neoformans using an adenylate kinase release assay that specifically detects fungicidal activity. A set of secondary assays narrowed the set of hits to molecules that interfere with fungal cell wall integrity and identified three benzothioureas with low in vitro mammalian toxicity and good in vitro anticryptococcal (minimum inhibitory concentration = 4 μg/mL). This scaffold inhibits signaling through the cell wall integrity MAP kinase cascade. Structure–activity studies indicate that the thiocarbonyl moiety is crucial for activity. Genetic and biochemical data suggest that benzothioureas inhibit signaling upstream of the kinase cascade. Thus, the benzothioureas appear to be a promising new scaffold for further exploration in the search for new anticryptococcal agents

Overcoming fluconazole resistance in Candida albicans clinical isolates with tetracyclic indoles

Continuing efforts to discover novel means of combating fluconazole resistance in Candida albicans have identified an indole derivative that sensitizes strains demonstrating resistance to fluconazole. This tetracycle (3, ML229) does not appear to act through established Hsp90 or calcineurin pathways to chemosensitize C. albicans, as determined in Saccharomyces cerevisiae models, and may be a useful probe to uncover alternative resistance pathways.National Institutes of Health (U.S.) (NIH-MLPCN program (1 U54 HG005032-1))National Institutes of Health (U.S.) (NIH (1 R03 MH086456-01)

Identification of Inhibitors of PvdQ, an Enzyme Involved in the Synthesis of the Siderophore Pyoverdine

Pseudomonas aeruginosa produces the peptide siderophore pyoverdine, which is used to acquire essential Fe3+ ions from the environment. PvdQ, an Ntn hydrolase, is required for the biosynthesis of pyoverdine. PvdQ knockout strains are not infectious in model systems, suggesting that disruption of siderophore production via PvdQ inhibition could be exploited as a target for novel antibacterial agents, by preventing cells from acquiring iron in the low iron environments of most biological settings. We have previously described a high-throughput screen to identify inhibitors of PvdQ that identified inhibitors with IC50 values of ∼100 μM. Here, we describe the discovery of ML318, a biaryl nitrile inhibitor of PvdQ acylase. ML318 inhibits PvdQ in vitro (IC50 = 20 nM) by binding in the acyl-binding site, as confirmed by the X-ray crystal structure of PvdQ bound to ML318. Additionally, the PvdQ inhibitor is active in a whole cell assay, preventing pyoverdine production and limiting the growth of P. aeruginosa under iron-limiting conditions

Efficient Routes to a Diverse Array of Amino Alcohol-Derived Chiral Fragments

Efficient syntheses of chiral fragments derived from chiral amino alcohols are described. Several unique scaffolds were readily accessed in 1–5 synthetic steps leading to 45 chiral fragments, including oxazolidinones, morpholinones, lactams, and sultams. These fragments have molecular weights ranging from 100 to 255 Da and are soluble in water (0.085 to >15 mM)