Antisense antibacterials

Controlled delivery of antisense oligonucleotides: a brief review of current strategies

Antisense therapy has been investigated extensively over the past two decades, either experimentally for gene functional research or clinically as therapeutic agents owing to the conceptual simplicity, ease of design and low cost. The concept of this therapeutic approach is promising because short antisense oligonucleotides (ASOs) can be delivered into target cells for specific hybridisation with target mRNA, resulting in the inhibition of the expression of pathogenic genes. However, the efficient delivery of the ASO molecules into target cells remains challenging; this bottleneck together with several other technical hurdles need to be overcome before this approach becomes effective and widely adopted. A variety of vectors such as lipids, polymers, peptides and nanoparticles have been explored. This review outlines the recent advances of the non-viral ASO delivery strategies. Several recent scientific studies, including authors' contributions, have been selected to highlight the technical aspects of ASO delivery.

Beyond silencing--engineering applications of RNA interference and antisense technology for altering cellular phenotype

Since its discovery 10 years ago, RNA interference (RNAi) has evolved from a research tool into a powerful method for altering the phenotype of cells and whole organisms. Its near universal applicability coupled with its pinpoint accuracy for suppressing target proteins has altered the landscape of many fields. While there is considerable intellectual investment in therapeutics, its potential extends far beyond. In this review, we explore some of these emerging applications--metabolic engineering for enhancing recombinant protein production in both insect and mammalian cell systems, antisense technologies in bacteria as next generation antibiotics, and RNAi in plant biotechnology for improving productivity and nutritional value.

Hitting bacteria at the heart of the central dogma: sequence-specific inhibition

An important objective in developing new drugs is the achievement of high specificity to maximize curing effect and minimize side-effects, and high specificity is an integral part of the antisense approach. The antisense techniques have been extensively developed from the application of simple long, regular antisense RNA (asRNA) molecules to highly modified versions conferring resistance to nucleases, stability of hybrid formation and other beneficial characteristics, though still preserving the specificity of the original nucleic acids. These new and improved second- and third-generation antisense molecules have shown promising results. The first antisense drug has been approved and more are in clinical trials. However, these antisense drugs are mainly designed for the treatment of different human cancers and other human diseases. Applying antisense gene silencing and exploiting RNA interference (RNAi) are highly developed approaches in many eukaryotic systems. But in bacteria RNAi is absent, and gene silencing by antisense compounds is not nearly as well developed, despite its great potential and the intriguing possibility of applying antisense molecules in the fight against multiresistant bacteria. Recent breakthrough and current status on the development of antisense gene silencing in bacteria including especially phosphorothioate oligonucleotides (PS-ODNs), peptide nucleic acids (PNAs) and phosphorodiamidate morpholino oligomers (PMOs) will be presented in this review.

Novel agents for the treatment of resistant Gram-positive infections

Bacteria have proved themselves able to develop resistance to every antibiotic used clinically. Traditional agents used for treatment of serious infections caused by Gram-positive species have recently been supplemented with the introduction of linezolid, quinupristin-dalfopristin, several new quinolones and telithromycin. However, resistance to many of these agents has already been reported and, although each currently retains activity against the vast majority of clinical isolates of its target species, their long-term efficacy is uncertain. We must look to develop other compounds to replace and hopefully improve upon existing anti-Gram-positive agents. Daptomycin (a lipopeptide), oritavancin and dalbavancin (both second-generation glycopeptides) and ramoplanin (a glycolipodepsipeptide) are among the agents in advanced stages of development and, at present, many seem likely to proceed to licensing. In addition, it is encouraging that many agents active against novel bacterial targets have been discovered and are in earlier stages of development. In the next two decades, we should be optimistic that a regular flow of new anti-Gram-positive agents will enable us to offset the constant spectre of bacterial resistance.