bAntivirulence agents inhibit the production of disease-causing virulence factors but are neither bacteriostatic nor bactericidal. Antivirulence agents against methicillin-resistant Staphylococcus aureus (MRSA) strain USA300, the most widespread community-associated MRSA strain in the United States, were discovered by virtual screening against the response regulator AgrA, which acts as a transcription factor for the expression of several of the most prominent S. aureus toxins and virulence factors involved in pathogenesis. Virtual screening was followed by similarity searches in the databases of commercial vendors. The small-molecule compounds discovered inhibit the production of the toxins alpha-hemolysin and phenol-soluble modulin ␣ in a dose-dependent manner without inhibiting bacterial growth. These antivirulence agents are small-molecule biaryl compounds in which the aromatic rings either are fused or are separated by a short linker. One of these compounds is the FDA-approved nonsteroidal anti-inflammatory drug diflunisal. This represents a new use for an old drug. Antivirulence agents might be useful in prophylaxis and as adjuvants in antibiotic therapy for MRSA infections.

The dwindling repertoire of antibiotics to treat methicillin-resistant Staphylococcus aureus (MRSA) calls for novel treatment options. Quorum-quenching agents offer an alternative or an adjuvant to antibiotic therapy. Three biaryl hydroxyketone compounds discovered previously (F1, F12, and F19; G. Yu, D. Kuo, M. Shoham, and R. Viswanathan, ACS Comb Sci 16:85-91, 2014) were tested for efficacy in MRSA-infected animal models. Topical therapy of compounds F1 and F12 in a MRSA murine wound infection model promotes wound healing compared to the untreated control. Compounds F1, F12, and F19 afford significant survival benefits in a MRSA insect larva model. Combination therapy of these quorum-quenching agents with cephalothin or nafcillin, antibiotics to which MRSA is resistant in monotherapy, revealed additional survival benefits. The quorum-quenching agents sensitize MRSA to the antibiotic by a synergistic mode of action that also is observed in vitro. An adjuvant of 1 g/ml F1, F12, or F19 reduces the MIC of nafcillin and cephalothin about 50-fold to values comparable to those for vancomycin, the antibiotic often prescribed for MRSA infections. These findings suggest that it is possible to resurrect obsolete antibiotic therapies in combination with these novel quorum-quenching agents. Methicillin-resistant Staphylococcus aureus (MRSA) is a widespread bacterial pathogen, causing various infections, ranging from skin and soft tissue infections to serious invasive infections, such as pneumonia, endocarditis, bacteremia, and sepsis (1, 2). Rising antibiotic resistance and diminishing investment by the pharmaceutical industry in the development of new antibiotics have created an urgent need for novel anti-MRSA agents (3). Quorum-quenching agents provide an alternative and an adjuvant to conventional antibiotic therapy (4, 5). The mechanism of action of quorum-quenching agents is fundamentally different from that for antibiotics. Quorum-quenching agents are neither bactericidal nor bacteriostatic. They inhibit the production of disease-causing toxins by the pathogen, thereby disarming the pathogen of its capacity to inactivate host defense factors. An intact host immune system has a better chance to clear a bacterial infection. A quorum-quenching agent tips the balance of bacterial virulence factors and host defense factors in favor of the host.Virulence factor production in Staphylococcus aureus is regulated by a quorum-sensing mechanism predominantly under the control of the agr operon (6, 7). In previous work, we have identified small-molecule biaryl hydroxyketone compounds that target the response regulator AgrA and inhibit its interaction with promoter P3, curtailing the production of toxins and virulence factors (8). In a follow-up study, a combinatorial library of 148 compounds was synthesized based on the most efficacious hit compound (9). A member of this biaryl hydroxyketone library, named F12, was the most efficacious of the synthesized compounds, demonstrating 98% in vitro MRSA rabbit erythrocyte hemolysis inhi...

Biocompatible dendrimers with well-defined nanosizes are increasingly being used as carriers for drug delivery. 5-Aminosalicylic acid (5-ASA) is an FDA approved therapeutic agent recently found effective in treating retinal degeneration of animal models. Here, a water-soluble dendrimer conjugate of 5-ASA (AGFB-ASA) was designed to treat such retinal degeneration. The drug was conjugated to a generation 2 (G2) lysine dendrimer with a silsesquioxane core (nanoglobule) by using a hydrolysable Schiff base spacer. Incubation of nanoglobular G2 dendrimer conjugates containing a 4-formylbenzoate (FB) Schiff base spacer in pH 7.4 phosphate buffers at 37 °C gradually released 5-ASA. Drug release from the dendrimer conjugate was significantly slower than from the low molecular weight free Schiff base of 5-ASA (FB-ASA). 5-ASA release from the dendrimer conjugate was dependent on steric hindrance around the spacer. After intraperitoneal injection, the nanoglobular 5-ASA conjugate provided more effective 7-day protection against light-induced retinal degeneration at a reduced dose than free 5-ASA in Abca4−/−Rdh8−/− mice. The dendrimer 5-ASA conjugate with a degradable spacer could be a good candidate for controlled delivery of 5-ASA to the eye for treatment of retinal degeneration.

Manganese-enhanced MRI has the potential to assess the response of the retina to prophylactic treatment based on the measurement of ion channel activity. This approach could be used as a complementary tool in preclinical development of new prophylactic therapies for retinopathies.

In the mol­ecule of the title compound, C5H7N7S, the essentially planar triazole ring and the 4‐amino‐5‐mercapto‐1,2,4‐triazole moiety make a dihedral angle of 70.97 (5)°. In the crystal structure, weak inter­molecular N—H⋯N and N—H⋯S hydrogen bonds stabilize the packing.

Retinal degeneration impairs the vision of millions in all age groups worldwide. Increasing evidence suggests that the etiology of many retinal degenerative diseases is associated with impairment in biochemical reactions involved in the visual cycle, a metabolic pathway responsible for regeneration of the visual chromophore (11-cis-retinal). Inefficient clearance of toxic retinoid metabolites, especially all-trans-retinal, is considered responsible for photoreceptor cytotoxicity. Primary amines, including retinylamine, are effective in lowing the concentration of all-trans-retinal within the retina and thus prevent retina degeneration in mouse models of human retinopathies. Here we achieved prolonged prevention of retinal degeneration by controlled delivery of retinylamine to the eye from polylactic acid nanoparticles in Abca4−/−Rdh8−/− (DKO) mice, an animal model of Stargardt disease/age-related macular degeneration. Subcutaneous administration of the nanoparticles containing retinylamine provided a constant supply of the drug to the eye for about a week and resulted in effective prolonged prevention of light-induced retinal degeneration in DKO mice. Retinylamine nanoparticles hold promise for prolonged prophylactic treatment of human retinal degenerative diseases, including Stargardt disease and age-related macular degeneration.

Antibiotic resistance coupled with decreased development of new antibiotics necessitates the search for novel antibacterial agents. Antivirulence agents offer an alternative to conventional antibiotics. In this work, we report on a family of small-molecule antivirulence agents against methicillin-resistant Staphylococcus aureus (MRSA), the most widespread bacterial pathogen. Structure-activity relationship studies led to the development of a concise synthesis of a 148-member biarylhydroxyketone library. An acylation bond-forming process afforded resorcinols (1) and aryloxy acetonitriles (2) as synthons. A Lewis-acid-activated Friedel-Crafts' acylation step involving a nitrile functionality of 2 by ZnCl2, followed by nucleophilic attack by 1 was executed to obtain biaryl hydroxyketones in excellent yields. A large number of products crystallized. This strategy affords a range of biarylhydroxyketones in a single step. This is the first collective synthetic study documenting access to this class of compounds through a single synthetic operation. In vitro efficacy of compounds in this library was evaluated by a rabbit erythrocyte hemolysis assay. The most efficacious compound, 4f-12, inhibits hemolysis by 98.1 ± 0.1% compared to control in the absence of the compound.

A series of novel 2-arylphenyl ether-3-(1H-1,2,4-triazol-1-yl)propan-2-ol derivatives were designed and synthesized as candidate fungicides. The new compounds were identified by (1)H NMR spectroscopy and element analysis. Their antifungal activities were evaluated. They exhibited excellent antifungal activities against five common pathogens in comparison with the commercial fungicides tebuconazole and difenoconazole. The antifungal activities of three new triazole alcohol compounds were compared with those of tebuconazole and difenoconazole at a concentration of 1 mug/mL.