Sirna Therapeutics Joins Russell 3000 Index

SAN FRANCISCO, July 6  /PRNewswire-FirstCall/ -- Sirna Therapeutics, Inc. (NASDAQ:RNAI), a leading RNAi-based therapeutics company, announced today that it has been added to the Russell 3000 and the Russell 2000 Indexes effective June 30, 2006.

"Being added to the Russell Index is one more indicator of the important progress Sirna has made over the past year advancing RNAi-based therapeutics," stated Howard W. Robin, President and Chief Executive Officer of Sirna.  "Our inclusion in the highly-regarded Russell indexes will further increase Sirna's visibility with investors and continue to provide us a solid investor base."

Russell indexes are widely used by investment managers and institutional investors for index funds and as benchmarks for both passive and active investment strategies. Investment managers who oversee these funds purchase shares of member stocks according to that company's weighting in the particular index. Annual reconstitution of the Russell indexes captures the 3,000 largest U.S. publicly traded stocks as of the end of May, ranking them by total market capitalization to create the Russell 3000. The largest 1,000 companies in the ranking comprise the Russell 1000 while the remaining 2,000 companies become the widely used Russell 2000.

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 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 B and C, dermatology, asthma, Huntington's disease, diabetes and oncology. Sirna Therapeutics completed its Phase 1 clinical trial for Sirna-027 in AMD in 2005 and with its strategic partner, Allergan, Inc., expects to move Sirna-027 into Phase 2 clinical trials in 2006. Sirna has selected a clinical compound for hepatitis C virus, Sirna-034, which the Company plans to bring into Phase 1 clinical trials by the end of 2006. Sirna has established an exclusive multi-year strategic alliance with GlaxoSmithKline for the development of siRNA compounds for the treatment of respiratory diseases. Sirna has a leading intellectual property portfolio in RNAi covering over 250 mammalian gene and viral targets and over 200 issued or pending patents covering other major aspects of RNAi technology, including microRNA technology. More information on Sirna Therapeutics is available on the Company's web site at http://www.sirna.com/.

About Russell Investment Group

Russell, a global leader in multi-manager investment services, provides investment products and services in 44 countries. Russell manages more than $167 billion in assets and advises clients worldwide representing $2.4 trillion. Founded in 1936, Russell is a subsidiary of Northwestern Mutual and is headquartered in Tacoma, Wash., with additional offices in New York, Toronto, London, Paris, Singapore, Sydney, Auckland and Tokyo. For more information, go to http://www.russell.com/.

Safe Harbor Statement

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. Patent applications may not result in issued patents, and issued patents may not be enforceable or could be invalidated. Other risks and uncertainties include, among others, Sirna's early stage of development and short operating history, Sirna's history and expectation of losses and need to raise capital, Sirna's need to obtain clinical validation and regulatory approval for Sirna-027, Sirna-034 and Sirna's other product candidates, any of which could have negative results, Sirna's need to engage collaborators, Sirna's need to obtain and protect intellectual property, and the risk of third-party patent infringement claims. These and additional risk factors are identified in Sirna's Securities and Exchange Commission filings, including its 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.

  Contacts
  Greg Weaver, SVP & CFO, Sirna Therapeutics, Inc., 415-512-7200
  Alan Zachary, McKinney/Chicago, 312-944-6784 x 316
  Brandon Belcher, The Ruth Group, 646-536-7009


DATASOURCE: Sirna Therapeutics, Inc.



CONTACT:  Greg Weaver, SVP & CFO of Sirna Therapeutics, Inc.,

[phone], or Alan Zachary of McKinney/Chicago, [phone] x 316,

or Brandon Belcher of The Ruth Group, [phone] 



Web site:  http://www.sirna.com/

http://www.russell.com/ 

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