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Targeted Genetics Corporation (TGEN) Announces Breakthrough Research By University of Iowa Collaborator

10/19/2005 5:13:16 PM

SEATTLE, April 12 /PRNewswire-FirstCall/ -- Targeted Genetics Corporation announced today that Dr. Beverly Davidson of the University of Iowa published encouraging preclinical results for a potential treatment of Huntington's Disease (HD). Dr. Davidson is an academic collaborator of Sirna Therapeutics , Targeted Genetics' partner for the development of novel therapies for the treatment of HD. The results of the independent preclinical study demonstrate that RNA interference (RNAi) therapy may have a beneficial impact on the symptoms and progression of HD. The study appeared April 5 in the Online Early Edition of Proceedings of the National Academy of Sciences (PNAS) ( and will be published in the April 19th issue of PNAS.

With RNA interference therapy, researchers for the first time have been able to attack the fundamental cause of Huntington's Disease and reduce the protein expression from the disease gene. The study is the first to show that a therapy designed to inhibit the expression of this protein has a beneficial effect on the disease symptoms. The study used RNAi to treat a mouse model of HD. Adeno-associated viral (AAV) vectors were used to express the siRNAs (short interfering RNAs) and were directly injected into the brain of mice with HD. The studies were conducted using AAV serotype 1 (AAV1) vectors. vectors of this serotype may have advantages as compared to vectors of some other AAV serotypes in a neurological setting by providing a higher transduction efficiency over a wider area of the brain. Results of the study by Dr. Davidson demonstrated nearly normal movement in the mice and significant improvements in characteristic neurological damage compared to untreated mice. The study also demonstrated that levels of toxic HD protein in siRNA treated mice were reduced to 40 percent of normal levels.

Dr. Beverly Davidson, senior author on the recent PNAS publication, said, "Many of the current approaches aimed at treating HD are indirect and target the symptoms of the disease. RNAi gives us the first opportunity to attack the fundamental problem and reduce protein expression from the disease gene. It is very exciting that a partial reduction in the HD protein is sufficient to produce a very beneficial effect in the animal. It means that we may not have to turn the gene off completely. Our results showed that with a partial reduction, disease progression can be delayed, and possibly prevented if given prior to onset. We are pleased with the study results and excited to collaborate with Sirna Therapeutics and Targeted Genetics to move the technology to clinical trials and commercialization."

"It is extremely encouraging to see this groundbreaking research from the University of Iowa and we are very excited to be working in partnership with Sirna toward the development of an siRNA therapeutic for Huntington's Disease," said H. Stewart Parker, President and Chief Executive Officer of Targeted Genetics. "Huntington's Disease is a devastating ailment that affects thousands of people for which there is currently no treatment. This research represents a major step toward developing an siRNA therapeutic to help patients suffering from HD."

Dr. Steven Hersch, Associate Professor of Neurology at Massachusetts General Hospital and Harvard Medical School, and chairman of Sirna's Clinical Advisory Board for neurodegeneration commented, "I am highly encouraged by Dr. Davidson's research, as it demonstrates that an siRNA is able to positively impact Huntington's Disease by reducing the disease-causing HD protein production in an animal model. Although much preclinical work remains necessary, the proof of concept threshold has now been crossed that validates siRNA as a potentially potent approach to treating Huntington's disease."

In January 2005, Targeted Genetics formed a collaboration to combine its AAV delivery platform with Sirna's RNAi expertise. Targeted Genetics and Sirna will co-develop an AAV vector-based treatment for Huntington's Disease, sharing development costs and revenues.

About RNA interference

RNA interference (RNAi) is a natural, selective process for turning off genes. RNAi is triggered by short interfering RNA (siRNA) molecules that engage a group of cellular proteins, known as RISC (RNA induced silencing complex). The RISC guides the siRNA to its target messenger RNA (mRNA, the messenger between DNA and proteins) by complementary base pairing for the targeted break-up of the mRNA thus halting protein expression or viral replication. The RISC-siRNA-complex binds and cleaves multiple mRNA molecules in a catalytic fashion.

About the Proceedings of the National Academy of Sciences

PNAS is one of the world's most-cited multidisciplinary scientific serials. Since its establishment in 1914, it continues to publish cutting-edge research reports, commentaries, reviews, perspectives, colloquium papers, and actions of the Academy. Coverage in PNAS spans the biological, physical, and social sciences. PNAS is published weekly in print, and daily online in PNAS Early Edition.

About Huntington's disease

Huntington's Disease (HD) is a devastating, inherited, degenerative brain disorder that is progressive and always fatal and for which there is, at present, no effective treatment or cure. HD affects more than 30,000 people in the United States, with another 200,000 at risk of inheriting the deadly gene. The disease-causing gene produces a protein that is toxic to certain brain cells, and the subsequent neuronal damage leads to the movement disorders, psychiatric disturbances and cognitive decline that characterize this disease. It is a dominant, fatal neurological disorder with no cure and no treatment that directly reduces mutant htt gene expression or otherwise prevents onset of the disease.

About Sirna Therapeutics

Sirna Therapeutics is a clinical-stage biotechnology company developing RNAi-based therapies for serious diseases and conditions, including age- related macular degeneration (AMD), Huntington's disease, diabetes, asthma, oncology, hepatitis C and hair removal. Sirna Therapeutics has initiated a Phase 1 clinical trial for its most advanced compound, Sirna-027, a chemically modified siRNA targeting the clinically validated vascular endothelial growth factor pathway to treat AMD. Sirna Therapeutics has strategic partnerships with Eli Lilly and Company, Targeted Genetics and Archemix Corporation and a leading intellectual property portfolio in RNAi. More information on Sirna Therapeutics is available on the Company's web site at

About Targeted Genetics

Targeted Genetics Corporation develops gene-based products for preventing and treating acquired and inherited diseases. The Company has clinical product development programs, targeting AIDS prophylaxis and inflammatory arthritis. The Company also has a promising pipeline of product candidates focused on hyperlipidemia, congestive heart failure and Huntington's disease that are being developed under collaboration agreements with others, and a broad platform of gene delivery technologies for application in nucleic acid-based drug development. For more information about Targeted Genetics, visit its website at

Contact: Stacie D. Byars 206-521-7392

Safe Harbor Statement under the Private Securities Litigation Reform Act of 1995:

This release contains forward-looking statements regarding our research programs, clinical trials, our product development and our potential to leverage our development platforms and other statements about our plans, objectives, intentions and expectations. In particular, the statements regarding the Company's pipeline and potential application of this research to any future product candidates are forward-looking statements. These statements, involve current expectations, forecasts of future events and other statements that are not historical facts. Inaccurate assumptions and known and unknown risks and uncertainties can affect the accuracy of forward-looking statements. Factors that could affect our actual results include, but are not limited to, delay or failure in developing an HD product candidate, results of animal research are not necessarily indicative of results in humans, the timing, nature and results of our research, potential development of alternative technologies or more effective products by competitors, our ability to obtain and maintain regulatory or institutional approvals, our ability to obtain, maintain and protect our intellectual property related to any of our research or product candidates, and our ability to raise capital when needed, as well as other risk factors described in the section entitled "Factors Affecting Our Operating Results, Our Business and Our Stock Price" in our Annual Report on Form 10-K for the year ended December 31, 2004. You should not rely unduly on these forward-looking statements, which apply only as of the date of this release. We undertake no duty to publicly announce or report revisions to these statements as new information becomes available that may change our expectations.

Investor and Media Contact: Stacie D. Byars Director, Communications Targeted Genetics Corporation (206) 521-7392

Targeted Genetics Corporation

CONTACT: Stacie D. Byars, Director, Communications of Targeted GeneticsCorporation, +1-206-521-7392

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