Quinazolinone fungal efflux pump inhibitors. Part 2: In vitro structure-activity relationships of (N-methyl-piperazinyl)-containing derivatives.

Structure-activity relationships of a novel series of fungal efflux pump inhibitors with respect to potentiation of the activity of fluconazole against strains of Candida albicans and Candida glabrata over-expressing ABC-type efflux pumps are systematically explored.

The potential of phosphodiesterase 4 inhibitors for the treatment of depression: opportunities and challenges.

The potential use of phosphodiesterase 4 (PDE4) inhibitors to treat various inflammatory diseases such as asthma and chronic obstructive pulmonary disease has garnered significant attention from the pharmaceutical industry over the last few years. In contrast, the potential use of PDE4 inhibitors to treat central nervous system disorders, such as major depressive disorders, has received less attention. With a growing body of work linking intracellular signaling pathways such as modulation of the cAMP second messenger system to a positive outcome following antidepressant therapy, the role that PDE4 inhibitors could play in the treatment of mood disorders has become more apparent. The following review examines the promise that PDE4 inhibitors may hold for the treatment of these diseases.

MexAB-OprM-specific efflux pump inhibitors in Pseudomonas aeruginosa. Part 1: discovery and early strategies for lead optimization.

The identification of a series of compounds that specifically inhibit efflux by the MexAB-OprM pump system in Pseudomonas aeruginosa is described. Synthesis and in vitro structure-activity relationships (SARs) are outlined. Early leads lacked activity in animal models, and efforts to improve solubility and reduce serum protein binding by the introduction of polar groups are discussed.

MexAB-OprM specific efflux pump inhibitors in Pseudomonas aeruginosa. Part 2: achieving activity in vivo through the use of alternative scaffolds.

Problems of low solubility, high serum protein binding, and lack of efficacy in vivo in first generation MexAB-OprM specific efflux pump inhibitors were addressed. Through the use of pharmacophore modelling, the key structural elements for pump inhibition were defined. Use of alternative scaffolds upon which the key elements were arrayed gave second generation leads with greatly improved physical properties and activity in the potentiation of antibacterial quinolones (levofloxacin and sitafloxacin) versus Pseudomonas aeruginosa in vivo.

The relationship between physicochemical properties, in vitro activity and pharmacokinetic profiles of analogues of diamine-containing efflux pump inhibitors.

Following the optimization of diamine-containing efflux pump inhibitors with respect to in vitro potentiation activity, in vivo stability and acute toxicity, we addressed the question of how to control the pharmacokinetic properties of the series. Upon intravenous administration in the rat, tissue levels of MC-04,124 (the lead compound) were high and prolonged compared to those in the serum. The lipophilicity and basicity of analogues of this compound were systematically varied, and effects on potency and pharmacokinetics explored. The ratio of drug levels in tissue versus serum was not significantly reduced in any of the active analogues examined.

Conformationally-restricted analogues of efflux pump inhibitors that potentiate the activity of levofloxacin in Pseudomonas aeruginosa.

Conformational restriction of the ornithine residue of the efflux pump inhibitor D-ornithine-D-homophenylalanine-3-aminoquinoline (MC-02,595, 2) furnished bioisosteric proline derivatives that were less toxic in vivo and as active as the lead in potentiating the activity of the fluoroquinolone levofloxacin via the inhibition of efflux pumps in Pseudomonas aeruginosa.

Molecular basis for fungal selectivity of novel antimitotic compounds.

Compounds that selectively disrupt fungal mitosis have proven to be effective in controlling agricultural pests, but no specific mitotic inhibitor is available for the treatment of systemic mycoses in mammalian hosts. In an effort to identify novel mitotic inhibitors, we used a cell-based screening strategy that exploited the hypersensitivity of a yeast alpha-tubulin mutant strain to growth inhibition by antimitotic agents. The compounds identified inhibited yeast nuclear division and included one structural class of compounds shown to be fungus specific. MC-305904 and structural analogs inhibited fungal cell mitosis and inhibited the in vitro polymerization of fungal tubulin but did not block mammalian cell microtubule function or mammalian tubulin polymerization. Extensive analysis of yeast mutations that specifically alter sensitivity to MC-305904 structural analogs suggested that compounds in the series bind to a site on fungal beta-tubulin near amino acid 198. Features of the proposed binding site explain the observed fungal tubulin specificity of the series and are consistent with structure-activity relationships among a library of related compounds.

Peptidomimetics of efflux pump inhibitors potentiate the activity of levofloxacin in Pseudomonas aeruginosa.

Several classes of peptidomimetics of the efflux pump inhibitor D-ornithine-D-homophenylalanine-3-aminoquinoline (MC-02,595) have been prepared and evaluated for their ability to potentiate the activity of the fluoroquinolone levofloxacin in Pseudomonas aeruginosa. A number of the new analogues were as active or more active than the lead, demonstrating that a peptide backbone is not essential for activity.