Ark Therapeutics Group plc has filed a patent application relating to a breakthrough small hairpin RNA (shRNA) based technology that allows both the up- and down-regulation of multiple genes via Ark's existing method of gene delivery. The discovery, which was made by Ark's scientists in Finland, represents a major advance on existing RNA silencing technology and has the potential for use in the treatment of a variety of human diseases involving defective genes, either where the genes do not work or are overactive.
Gene expression is the process by which information from a gene is made into a functional product such as a protein. In this process, ribonucleic acid (RNA) acts as a form of messenger which reads the DNA code and then 'tells' a structure (ribosome) in the cytoplasm precisely what protein to make. If a gene is defective, existing gene silencing methods can 'switch off' the gene effect using a technology known as small interfering RNA (siRNA) which interferes with the messenger RNA, but this technology only has the ability to suppress the effect of the gene. The technology is also limited by current delivery mechanisms. siRNA is usually delivered to cells using synthetic oligonucleotides in very large quantities in an attempt to get them into the nucleus and cytoplasm of cells. In disease models various liposome type approaches have been used but they still deliver less siRNA to the cytoplasm than is generally required. Alternatively, adenoviruses can be used to deliver the siRNA but this method does not always place it in the right compartment in the cytoplasm for correct processing.
Therefore, although conventional siRNA technology is able to silence the target gene, the technology is in many ways limited in terms of its medical application. Earlier attempts to modulate gene effects, such as the zinc finger protein-based approach to down-regulate or up-regulate endogenous gene expression, have also encountered problems such as lack of specificity.
Ark's new shRNA technology is unique in that it appears to be actively taken to the nucleus of the cell where it acts on the promoter of the target gene via an epigenetic mechanism. After processing in the nucleus, it can both down-regulate (silence) or up-regulate (increase) gene expression within the cell (endogenous gene expression). Ark's new technology can also perform multiple gene up- or down-regulation with the same vector construct. Importantly, it can be delivered using Ark's existing and established viral vector technologies according to the length of time an effect is needed.
Professor John Martin, chief scientific officer of Ark, commented, "Since the Human Genome Project, the link between disease development and an individual's DNA is increasingly being recognised. RNA silencing to block a defective gene has been an area of great interest for the pharmaceutical industry in recent years but this technology moves it to a different level. Many diseases are caused by under or over expression of multiple genes and so the potential ability to 'turn up' or 'turn down' the effects of the 'in situ' existing genes, without having to insert new genes to correct the pathology, is a groundbreaking step forward both for patients and medical science."
Dr Nigel Parker, CEO of Ark, added, "This is extremely exciting technology which in many respects complements our previous discovery of targeted gene insertion two years ago and which we believe has the potential for broad utilisation in the treatment of disease. We now have a full toolkit which provides the flexibility to both selectively insert beneficial genes or correct defective genes, enabling us to develop a wide range of DNA based medical treatments, for example to switch off cell proliferation or migration in the treatment of cancer and vascular disease. It is becoming increasingly evident that DNA based medicines have the potential to provide therapeutic solutions to a number of presently untreatable diseases and Ark continues to operate at the forefront of this highly innovative area of medicine."