Sirna Therapeutics to Summarize Program Progress and Strategic Ocular Alliance with Allergan at the

SAN FRANCISCO, Sept. 29 /PRNewswire-FirstCall/ -- Sirna Therapeutics, Inc. the leading clinical-stage RNAi therapeutics company, will be presenting at the UBS Global Life Sciences Conference in the Grand Hyatt Hotel, New York, NY today Thursday, September 29, 2005 at 9:30 am EDT. Sirna CEO, Howard W. Robin will provide an update on Sirna pipeline programs as well as a summary of its strategic ocular alliance with Allergan.

An audio webcast of the presentation will be available at the company’s corporate web site at www.sirna.com. Participants are urged to log on to the web site 15 minutes prior to the scheduled start time to download and install any necessary audio software. The audio webcast replay will be available on Sirna’s web site, www.sirna.com, for 30 days.

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 has presented interim Phase 1 clinical trial data for its most advanced compound, Sirna-027, a chemically optimized siRNA targeting the clinically validated vascular endothelial growth factor pathway to treat AMD. The results to date, demonstrate that Sirna-027 for AMD is safe and well tolerated. Visual acuity has stabilized in 100 percent of patients treated and clinically significant improvement, of three lines or greater on the ETDRS eye chart, has been observed in 25 percent of the patients tested. Sirna Therapeutics has collaborations with Eli Lilly and Company, Targeted Genetics, Archemix Corporation and Protiva Biotherapeutics. Sirna has a leading intellectual property portfolio in RNAi with 43 issued patents and over 250 pending applications worldwide. More information on Sirna Therapeutics is available on the Company’s web site at http://www.sirna.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. For example, there is a significant risk for any given patent application that it will not become an issued patent, or that for any issued patent, it could be subject to challenge or may not be enforceable. Further, Sirna’s ability to develop products and operate as a going concern is contingent upon having readily available cash to fund its operating programs and is subject to the escalating expenses and risks associated with the initiation of clinical trials and their potential outcomes. Additional risks and uncertainties include 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 products, Sirna’s need to obtain and protect intellectual property, risk of third-party patent infringement claims, Sirna’s need to attract and retain qualified personnel, Sirna’s need to engage collaborators, availability of materials for product manufacturing, the highly competitive nature of the pharmaceutical market, the limited trading volume and history of volatility of Sirna’s common stock, Sirna’s concentration of stock ownership, and risks from relocating Sirna headquarters. 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.

Contacts: Rebecca Galler Robison, Senior Director, Corporate Strategy Sirna Therapeutics, Inc., +1-303-449-6500 Francesca DeMartino (investors) or Jason Rando (media), both of The Ruth Group, +1-646-536-7024 / 7025

Sirna Therapeutics, Inc.

CONTACT: Rebecca Galler Robison, Senior Director, Corporate Strategy ofSirna Therapeutics, Inc, +1-303-449-6500; or Investors, FrancescaDeMartino, +1-646-536-7024, or Media, Jason Rando, +1-646-536-7025, both ofThe Ruth Group, for Sirna Therapeutics, Inc.