ABSTRACT
Natural products have provided considerable value to the pharmaceutical industry over the past half century. In particular, the therapeutic areas of infectious diseases and oncology have benefited from numerous drug classes derived from natural product sources. Unfortunately, pharmaceutical companies have significantly decreased activities in natural product discovery during the past several years. Biotechnology companies working in the fields of combinatorial biosynthesis, genetic engineering and metagenomic approaches to identify novel natural product lead molecules have had limited success. Despite what appears to be a slow death of natural product discovery research, many new and interesting molecules with biological activity have been published in the past few years. If natural product materials continue to be tested for desirable therapeutic activities, we believe that significant progress in identifying new antibiotics, oncology therapeutics and other useful medicines will be made.
Subject(s)
Biological Products , Drug Industry/trends , Amino Acid Sequence , Anti-Infective Agents/chemistry , Anti-Infective Agents/isolation & purification , Anti-Infective Agents/pharmacology , Antineoplastic Agents/chemistry , Antineoplastic Agents/isolation & purification , Antineoplastic Agents/pharmacology , Biological Products/chemistry , Biological Products/classification , Biological Products/isolation & purification , Biological Products/pharmacology , Molecular Sequence Data , Molecular StructureABSTRACT
Further structure-activity relationships of a novel series of fungal efflux pump inhibitors with respect to potentiation of the activity of fluconazole against strains of C. albicans and C. glabrata over-expressing ABC-type efflux pumps are systematically explored. Rat protein binding and pharmacokinetics of selected analogues are reported.
Subject(s)
Antifungal Agents/pharmacology , Membrane Transport Proteins/drug effects , Piperazines/chemistry , Quinazolinones/pharmacology , Serum/chemistry , Animals , Antifungal Agents/blood , Antifungal Agents/chemistry , Antifungal Agents/pharmacokinetics , Candida albicans/drug effects , Hepatocytes/metabolism , Male , Membrane Transport Proteins/metabolism , Molecular Structure , Piperazine , Quinazolinones/blood , Quinazolinones/pharmacokinetics , Rats , Rats, Sprague-Dawley , Structure-Activity RelationshipABSTRACT
The discovery of a series of quinazolinone-based fungal efflux pump inhibitors by high-throughput screening for potentiation of fluconazole in C. albicans is described. Attempts to improve the aqueous solubility of screening hits led to the discovery of an analog with greatly improved physical properties and activity against clinically-relevant Candida spp.
Subject(s)
ATP-Binding Cassette Transporters/antagonists & inhibitors , Antifungal Agents/chemical synthesis , Candida/drug effects , Fungal Proteins/antagonists & inhibitors , Membrane Transport Modulators , Membrane Transport Proteins/antagonists & inhibitors , Piperazines/chemical synthesis , Quinazolines/chemical synthesis , Antifungal Agents/pharmacology , Candida/enzymology , Drug Resistance, Fungal , Drug Synergism , Fluconazole/chemistry , Fluconazole/pharmacology , Humans , In Vitro Techniques , Models, Molecular , Piperazines/chemistry , Piperazines/pharmacology , Quinazolines/chemistry , Quinazolines/pharmacology , Solubility , Stereoisomerism , Structure-Activity RelationshipABSTRACT
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.
Subject(s)
Antifungal Agents/chemical synthesis , Candida/drug effects , Membrane Transport Modulators , Membrane Transport Proteins/antagonists & inhibitors , Piperazines/chemical synthesis , Quinazolines/chemical synthesis , Antifungal Agents/chemistry , Antifungal Agents/pharmacology , Candida/enzymology , Candida albicans/drug effects , Candida albicans/enzymology , Candida glabrata/drug effects , Candida glabrata/enzymology , Drug Resistance, Fungal , Drug Synergism , Fluconazole/chemistry , Fluconazole/pharmacology , Fungal Proteins/antagonists & inhibitors , Humans , Microbial Sensitivity Tests , Piperazines/chemistry , Piperazines/pharmacology , Quinazolines/chemistry , Quinazolines/pharmacology , Stereoisomerism , Structure-Activity RelationshipABSTRACT
A collection of Aspergillus fumigatus mutants highly resistant to itraconazole (RIT) at 100 micro g ml(-1) were selected in vitro (following UV irradiation as a preliminary step) to investigate mechanisms of drug resistance in this clinically important pathogen. Eight of the RIT mutants were found to have a mutation at Gly54 (G54E, -K, or -R) in the azole target gene CYP51A. Primers designed for highly conserved regions of multidrug resistance (MDR) pumps were used in reverse transcriptase PCR amplification reactions to identify novel genes encoding potential MDR efflux pumps in A. fumigatus. Two genes, AfuMDR3 and AfuMDR4, showed prominent changes in expression levels in many RIT mutants and were characterized in more detail. Analysis of the deduced amino acid sequence encoded by AfuMDR3 revealed high similarity to major facilitator superfamily transporters, while AfuMDR4 was a typical member of the ATP-binding cassette superfamily. Real-time quantitative PCR with molecular beacon probes was used to assess expression levels of AfuMDR3 and AfuMDR4. Most RIT mutants showed either constitutive high-level expression of both genes or induction of expression upon exposure to itraconazole. Our results suggest that overexpression of one or both of these newly identified drug efflux pump genes of A. fumigatus and/or selection of drug target site mutations are linked to high-level itraconazole resistance and are mechanistic considerations for the emergence of clinical resistance to itraconazole.
