Sirna Issued UK Patent Covering RNAi-Mediated Inhibition of Gene Expression

Sirna Therapeutics, Inc. has announced that the United Kingdom Patent Office has issued a broad patent covering RNA interference mediated inhibition of gene expression using short-interfering ribonucleic acids.

The patent claims, which are not limited to a specific siRNA sequence or structure, broadly cover any siRNA molecule which targets conserved sequences within a virus or a gene.

First, it allows an siRNA therapeutic to target the conserved region of a virus thus targeting multiple strains of the virus as well as preventing escape mutants.

Second, the patent allows an siRNA therapeutic to target more than one gene in a biological pathway to increase therapeutic effect of an siRNA.

Together, these claims provide coverage for the development of siRNA therapeutics to treat RNA viruses such as Hepatitis C virus, human immunodeficiency virus, respiratory syncytial virus, influenza virus, bird flu virus, and severe acute respiratory syndrome as well as other viral or gene targets where targeting a conserved region would provide therapeutic benefit.

“To effectively develop RNAi-based therapeutics against certain RNA viruses, it is critical to target conserved sequences of the viral RNA,” stated Barry Polisky, PhD, Senior Vice President and Chief Scientific Officer at Sirna.

“These viruses mutate at a high frequency and can become resistant to single agent therapies. However, not all regions of the virus mutate at the same rate.”

“The conserved viral regions are those that mutate at a lower rate thus targeting this region decreases the likelihood that the virus can mutate to escape the action of a therapeutic.”

“By targeting conserved sequences of an RNA virus, such as HCV or RSV, we can have a potent therapeutic effect on a wide range of viral variants.”

The patent also addresses the potential for siRNA therapeutics targeting one or more genes in a biological pathway.

Targeting conserved sequences which are shared between two or more genes offers a therapeutic approach to diseases such as age-related macular degeneration (AMD).

For example, Sirna is investigating the regulation of angiogenesis in AMD by targeting multiple VEGF receptors - VEGFR1 and VEGFR2 - using a single siRNA molecule.
 
Instead of designing a separate therapeutic modality against each of these two receptors, it is possible to design a single siRNA to reduce the expression of both VEGF receptors by targeting common sequences shared by the two.
 
As such, siRNAs can be used to inhibit the expression of multiple genes involved in a disease process for increased therapeutic effect.

The claims in this patent are not limited to any specific gene target sequence or structure and are broadly applicable to inhibiting gene targets sharing conserved or homologous sequences.

To date, Sirna has filed over 125 patents in multiple countries around the world on mammalian genes and viruses responsible for neurological, cardiovascular, infectious, metabolic, ocular, oncology and respiratory human diseases.

The issuance of this patent follows three target patents and one broad- spectrum siRNA patent secured earlier this year by Sirna in the United Kingdom.

The UK patents, which address the Hepatitis C Virus, Vascular Endothelial Growth Factor and Vascular Endothelial Growth Factor Receptor-1, broadly cover siRNAs against these targets.

The company was also issued a broad patent covering the chemical and structural modifications of siRNAs necessary for the creation of viable siRNA-based therapeutics.

In the coming months Sirna expects that patents with similar scope and breadth will be issued in other major countries.