Sirna Therapeutics Announces RNAi Therapeutic Development Program to Address Huntington's Disease

Sirna Partners With Huntington's Disease Society of America

Studies Ongoing With Collaborators at University of Iowa to Assess RNAi-Based

Compounds for Neurodegeneration

Oct 20, 2004, 01:00 ET from Sirna Therapeutics, Inc.

    BOULDER, Colo., Oct. 20 /PRNewswire-FirstCall/ -- Sirna Therapeutics, Inc.
 (Nasdaq:   RNAI) today announced that the Company is moving forward with the
 development of an RNA interference (RNAI)-based treatment for Huntington's
 Disease.  Huntington's Disease (HD) is a devastating, degenerative brain
 disorder 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.  Early in 2005, Sirna expects to select
 investigational compounds for preclinical development based on the
 groundbreaking work of the Company's research collaborator, Dr. Beverly
 Davidson at the University of Iowa.  Sirna also announced today its
 collaboration with the Huntington's Disease Society of America (HDSA) and is
 looking forward to working with the Society's network of clinical
     Howard Robin, Sirna's President and Chief Executive Officer, commented,
 "We are extremely proud of our new relationship with the Huntington's Disease
 Society of America.  The Society's efforts have been instrumental in bringing
 hope to patients and their families affected by this devastating disease.
 Sirna's researchers and scientists are dedicated to suppressing the expression
 of the gene that causes Huntington's Disease."
     Dr. Roberto Guerciolini, Senior Vice President of Development and Chief
 Medical Officer at Sirna Therapeutics, commented, "For many neurodegenerative
 diseases, including Huntington's Disease, treatments are either non-existent
 or can do little to stop or reverse the progression of the disease.  Together
 with our collaborator, Dr. Beverly Davidson, Sirna is leading the effort to
 develop an effective treatment for Huntington's Disease."
     Sirna's collaborator, Dr. Beverly Davidson, recently demonstrated that a
 short interfering RNA (siRNA) efficiently inhibited gene expression in an
 animal model of a disease mimicking spinocerebellar ataxia 1 (SCA1), a member
 of a class of inherited human neurodegenerative diseases that includes
 Huntington's Disease.  The study appeared in the August issue of Nature
 Medicine (Volume 10, pp 816, August 2004).  The Company has exclusively
 licensed key patents from the University of Iowa Research Foundation for the
 use of RNAi technology in the field of neurological diseases, including those
 relating to SCA1, Huntington's, Parkinson's and Alzheimer's Diseases.  These
 patents complement Sirna's intellectual property in Huntington's Disease and
 further strengthen the Company's broad intellectual property portfolio
 covering the seminal RNAi technology, chemical modifications, therapeutic
 targets, delivery and manufacturing of siRNAs.
     About RNA Interference
     Sirna Therapeutics is using its proprietary technology and expertise in
 nucleic acids to develop a new class of nucleic acid-based therapeutics
 involving RNA interference.  RNAi is a mechanism used by cells to regulate the
 expression of genes and replication of viruses.  The RNA interference
 mechanism uses short interfering RNA (siRNA) to induce the destruction of
 target RNA using naturally occurring cellular protein machinery.  Harnessing
 the natural phenomenon of RNAi holds potential for the development of a new
 class of drugs with specificity towards a wide range of diseases that result
 from undesirable protein production or viral replication.
     About the Huntington's Disease Society of America
     The Huntington's Disease Society of America (HDSA) is a voluntary health
 agency with chapters, affiliates, support groups and Centers of Excellence
 throughout the United States.  The Huntington's Disease Society of America
 (HDSA) funds and supports research to find a cure, helps people and families
 affected by the disease, and educates the public and healthcare professionals
 about this genetic disease.
     The organization was founded by the late Marjorie Guthrie, widow of famous
 folk singer Woody Guthrie after he died of complications related to
 Huntington's Disease in 1967.
     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), hepatitis, oncology, and diseases of
 the central nervous system.  Sirna has filed an IND for its most advanced
 compound, Sirna-027, a chemically modified siRNA targeting the clinically
 validated vascular endothelial growth factor pathway to treat AMD.  The
 Company has strategic partnerships with Eli Lilly and Archemix and a leading
 intellectual property portfolio in RNAi.  More information on Sirna
 Therapeutics is available on the Company's web site at
     Statements in this press release which are not strictly historical are
 "forward-looking" statements which should be considered as subject to many
 risks and uncertainties.  For example, Sirna's ability to select promising
 investigational compounds for preclinical development and its ability to
 achieve any progress in suppressing gene expression for Huntington's Disease,
 are subject to considerable scientific uncertainty.  Other risks and
 uncertainties include Sirna's early stage of development and short operating
 history, whether Sirna can achieve and maintain profitability, whether Sirna
 can obtain and protect patents, the risk of third-party patent infringement
 claims, whether Sirna can engage collaborators and obtain regulatory approval
 for products, Sirna's concentration of stock ownership, and availability of
 materials for product manufacturing.  These and additional risk factors are
 identified in Sirna's Securities and Exchange Commission filings, including
 the Forms 10-K and 10-Q and in other SEC filings.  Sirna undertakes no
 obligation to revise or update any forward-looking statements in order to
 reflect events or circumstances that may arise after the date of this release.
     Sirna Contact: Martin E. Schmieg, Senior Vice President and Chief
 Financial Officer, Sirna Therapeutics, Inc., 303-449-6500
     Media Contact: Justin Jackson,; Investor Contact:
 Aline Schimmel,, Burns McClellan, Inc., 212-213-0006
     HDSA contact:  Deb Lovecky, 212-242-1968 extension 28,

SOURCE Sirna Therapeutics, Inc.