Seattle Genetics Announces Pricing of Public Offering of Common Stock

Seattle Genetics anticipates using the net proceeds from the offering to fund research and development efforts, including manufacturing activities and clinical trials for its proprietary product candidates, build-out of a commercial infrastructure and for general corporate purposes, including working capital.

J.P. Morgan Securities Inc. and Goldman, Sachs & Co. are acting as joint book-running managers of the offering. Needham & Company, LLC, Oppenheimer & Co. Inc., RBC Capital Markets Corporation and William Blair & Company, LLC are acting as co-managers of the offering. A copy of the final prospectus supplement and accompanying prospectus relating to the offering, when available, may be obtained by contacting J.P. Morgan Securities Inc., Attention: Prospectus Department, 4 Chase Metrotech Center, CS Level, Brooklyn, NY 11245 or by calling (718) 242-8002 or Goldman, Sachs & Co., 85 Broad Street, SC Level, New York, New York 10004, Attention: Prospectus Department or by calling (866) 471-2526.

A shelf registration statement relating to the shares was filed with the Securities and Exchange Commission and is effective. This press release does not constitute an offer to sell, or the solicitation of an offer to buy, these securities, nor will there be any sale of these securities in any state or other jurisdiction in which such offer, solicitation or sale is not permitted.

About Seattle Genetics

Seattle Genetics is a clinical stage biotechnology company focused on the development and commercialization of monoclonal antibody-based therapies for the treatment of cancer and autoimmune disease.

Certain of the statements made in this press release are forward looking, such as those, among others, relating to Seattle Genetics’ expectations regarding the completion, timing and size of the public offering and its anticipated use of net proceeds from the offering. Actual results or developments may differ materially from those projected or implied in these forward-looking statements. Factors that may cause such a difference include, without limitation, risks and uncertainties related to market conditions and the satisfaction of customary closing conditions related to the public offering. There can be no assurance that Seattle Genetics will be able to complete the public offering on the anticipated terms, or at all. Seattle Genetics will continue to need significant amounts of additional capital to fund its operations and may be unable to raise capital when needed, which would force Seattle Genetics to delay, reduce the scope of or eliminate one or more of its development programs. Additional risks and uncertainties relating to the public offering, Seattle Genetics and its business can be found under the heading “Risk Factors” in Seattle Genetics’ Quarterly Report on Form 10-Q for the quarter ended June 30, 2009, and in the final prospectus supplement related to the public offering to be filed with the Securities and Exchange Commission. Seattle Genetics disclaims any intention or obligation to update or revise any forward-looking statements, whether as a result of new information, future events or otherwise.

Seattle Genetics, Inc.
Peggy Pinkston, 425-527-4160
ppinkston@seagen.com