ST. LOUIS, May 7 — Sigma-Aldrich(TM) (Nasdaq: SIAL – News) and the second phase of The RNAi Consortium (TRC2) have commenced functional validation of the Consortium’s collection of approximately 160,000 previously-cloned lentiviral-based shRNA vector constructs. Currently, more than 5,000 clones have been tested in the functional validation process. Validated clones covering more than 700 genes are available in Sigma-Aldrich’s MISSION® shRNA collection, a number expected to grow by 75,000 clones per year through 2011. TRC2 will also generate and validate 150,000 additional clones and utilize its collection of validated shRNA libraries to develop new and improved RNAi screening strategies. Design and development of TRC libraries is led by the Broad Institute of MIT and Harvard. A key goal of the Consortium is to provide at least two clones with a knockdown level of 70% or greater for every human and mouse gene over the next four years. Research will also center on alternative vector development and improved design, with the possible creation of sub-libraries. Functional validation of these knockdown clones will provide significant time and cost savings to researchers by reducing the number of wells to screen, facilitating improved throughput. The total TRC shRNA collection will eventually comprise 300,000 pre-cloned lentiviral-based shRNA vector constructs targeting the human and mouse genomes. Sigma-Aldrich’s MISSION® shRNA portfolio is the exclusive source for researchers to access TRC and TRCII shRNA libraries in the plasmid DNA and lentiviral formats. All of the shRNA reagents will be fully functionally validated during phase 2 of The RNAi Consortium. This validation data will be accessible to customers by request, and online, making the MISSION® portfolio the only commercially available set of RNAi reagents guaranteed to work out of the box. Sigma-Aldrich will also expand its program to promote and educate the research community about the multiple applications of RNAi technology by providing educational tools and forums. “Sigma-Aldrich is committed to the development of RNAi technology. Through our collaboration with TRC2, we’re producing the most highly validated shRNA libraries available to the research community,” said Dave Smoller, President of Sigma-Aldrich’s Research Biotech Business Unit. “By making these tools available to researchers worldwide, Sigma-Aldrich is facilitating advanced disease and drug discovery research.” Lentiviral-based shRNA libraries enable researchers to study gene function and disease, both in standard cell lines and recognized difficult cell types such as primary, non-dividing, growth-arrested or terminally differentiated cells. Such cell lines are typically not amenable to standard transfection or genomic integration by other viral delivery systems, but they may be transduced efficiently with lentiviral particles. “Over the coming years, The RNAi Consortium intends to build upon its successes with shRNA to facilitate loss-of-function genetic screens in mammalian cells,” said David Root, Director of the RNAi Platform at the Broad Institute of MIT and Harvard and project leader for TRC2. “The existing TRC library has already proven highly effective for systematic viral-delivery RNAi screening. TRC2 will generate significant further improvements to the library and its applications.” The current MISSION® shRNA clone libraries comprise a comprehensive collection of more than 160,000 pre-cloned lentiviral-based shRNA vector constructs targeting more than 16,000 human genes (MISSION TRC-Hs1.0) and 16,000 mouse genes (MISSION TRC-Mm1.0). For more information about the MISSION® shRNA clone collections, please visit us online at http://www.sigma.com/trc2. About Sigma-Aldrich: Sigma-Aldrich is a leading Life Science and High Technology company. Its biochemical and organic chemical products and kits are used in scientific and genomic research, biotechnology, pharmaceutical development, the diagnosis of disease and as key components in pharmaceutical and other high technology manufacturing. The Company has customers in life science companies, university and government institutions, hospitals, and in industry. Over one million scientists and technologists use its products. Sigma-Aldrich operates in 36 countries and has 7,900 employees providing excellent service worldwide. Sigma-Aldrich is committed to Accelerating Customer Success through Leadership in Life Science, High Technology and Service. For more information about Sigma-Aldrich, please visit its award-winning Web site at http://www.sigma-aldrich.com. For more information about TRC2, please see the TRC Web page at http://www.broad.mit.edu/genome_bio/trc/. Cautionary Statement: This release contains forward-looking statements relating to future performance, goals, strategic actions and initiatives and similar intentions and beliefs and other statements regarding the Companies’ expectations, goals, beliefs, intentions and the like, which involve assumptions regarding the Company’s operations and conditions in the markets the Companies serve. The Companies do not undertake any obligation to update these forward-looking statements.