Dharmacon Launches siSTABLE(TM) siRNA With Greatly Increased Stability And Extended Silencing Longevity

LAFAYETTE, Colo., Dec. 15 /PRNewswire/ -- Dharmacon, Inc., the leading global supplier of innovative RNA and RNA interference (RNAi) research products, today announced the launch of siSTABLE siRNA, its proprietary form of siRNA modified to significantly enhance stability, potency and silencing longevity while decreasing cellular toxicity. In comparative cell culture studies, siSTABLE siRNA maintains full silencing potency after seven days, while the silencing effect of unmodified siRNA is completely diminished by day seven. In human serum, where nucleases break down unmodified siRNA, siSTABLE siRNA half-life is increased more than 500 fold from minutes to over 85 hours (3 1/2 days). The siSTABLE siRNA modifications also alter siRNA processing within the cell, increasing gene silencing potency and specificity. Dharmacon is presenting data on siSTABLE siRNA at the 43rd Annual Meeting of the American Society for Cell Biology in San Francisco on December 15, 2003.

"We believe that siSTABLE siRNA represents a fundamental breakthrough for researchers using RNAi in cell culture or animal applications," said Stephen A. Scaringe, Ph.D., co-chairman and chief scientific officer at Dharmacon. "The extraordinary properties of siSTABLE siRNA will enable a range of experiments which were previously not feasible with conventional siRNA."

To develop siSTABLE siRNA, Dharmacon chemically modifies the siRNA strands in a novel and proprietary manner. The new product also builds on previously announced proprietary modifications contained in Dharmacon's patent pending ON-TARGET(TM) siRNA that inactivate the siRNA sense strand, completely eliminating its potential role in causing off-target silencing. These modifications together result in dramatically increased stability and longevity of effect while achieving very high gene silencing specificity. Microarray gene expression analysis studies to date have shown no cellular toxicity from use of siSTABLE siRNA. Dharmacon has filed patent applications on the siSTABLE siRNA technology.

"We are committed to working with life sciences researchers to make the potential advantages of RNAi widely available for an increasing range of biomedical applications" continued Dr. Scaringe, "siSTABLE siRNA outperforms conventional siRNA in both in vitro and in vivo applications. We are especially optimistic about the promise of siSTABLE siRNA for in vivo studies. The increased silencing longevity and specificity combined with controlled, non-viral delivery, and the chemically defined nature of this molecule, make siSTABLE an attractive candidate for animal model and potential therapeutic applications."

siSTABLE achieves greatest potency and stability when used in tandem with siRNA designed using Dharmacon's industry leading SMARTselection(TM) design algorithm though siSTABLE siRNA technology can be applied to any siRNA sequence. siSTABLE has also been shown to improve the silencing potency of moderately effective siRNA sequences.

siSTABLE siRNA is available today for in vitro cell culture applications to silence expression of genes with low turnover rates, for prolonged silencing, or for use in serum containing culture environments. siSTABLE siRNA for in vivo animal applications will be available January 2004. More information on siSTABLE can be found on the Dharmacon website http://www.dharmacon.com/ .

About Dharmacon

Dharmacon, Inc. is the world's leading provider of the most reliable and highest quality RNA oligonucleotides, small interfering RNA (siRNA) and related RNA-interference (RNAi) products and technologies to the life sciences industry. Founded in 1995, Dharmacon discovered and commercialized 2'-ACE(R), a novel, highly productive chemical strategy for RNA synthesis. Using its core expertise in chemistry, biology, bioinformatics and production, Dharmacon has pioneered a custom siRNA design service that employs its proprietary SMARTselection(TM) algorithm for maximizing the efficiency of gene silencing, a powerful and increasingly widely-used new technology based on siRNA. Dharmacon's proprietary SMARTselection(TM) and SMARTpool(R) technologies result in potent and specific gene silencing agents that can accelerate research and discovery across a broad range of biomedical and biological research. The company's recently released ON-TARGET(TM) siRNA further enhances silencing specificity by inactivating the sense strand of the siRNA duplex, one of the factors responsible for off-target effects. Dharmacon is based in Lafayette, Colorado. For more information, visit the company's Web site at http://www.dharmacon.com/

For further information, please contact: Michael Deines, V.P. Marketing of Dharmacon, +1-303-604-9499, or Media, Barbara Lindheim of GendeLLindheim BioCom Partners, +1-212-918-4650, for Dharmacon, Inc.

Dharmacon, Inc.

CONTACT: Michael Deines, V.P. Marketing of Dharmacon, +1-303-604-9499,or Media, Barbara Lindheim of GendeLLindheim BioCom Partners, +1-212-918-4650,for Dharmacon, Inc.

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