Seattle Genetics to Host Conference Call and Webcast Discussion of Third Quarter 2009 Financial Results on October 22, 2009

Seattle Genetics, Inc. (Nasdaq:SGEN) announced today that it will report its third quarter 2009 financial results on Thursday, October 22, 2009, after the close of financial markets. Following the announcement, company management will host a conference call and webcast discussion of the results and provide a general corporate update. Access to the event can be obtained as follows:

LIVE access on Thursday, October 22, 2009, 2:00 p.m. Pacific Time (PT) / 5:00 p.m. Eastern Time (ET)

• Telephone 800-762-8908 (domestic) or 480-629-9774 (international); conference ID 4172548
• Webcast available at www.seattlegenetics.com in the Investors and News section

REPLAY access

• Telephone replay will be available beginning at approximately 4:00 p.m. PT on October 22, 2009 through 4:00 p.m. PT on October 26, 2009 by calling 800-406-7325 (domestic) or 303-590-3030 (international); conference ID 4172548
• Webcast replay will be available on the Seattle Genetics website at www.seattlegenetics.com in the Investors and News section

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. The company’s lead product candidate, brentuximab vedotin (SGN-35), is in a pivotal trial under a special protocol assessment with the FDA. Brentuximab vedotin is empowered by Seattle Genetics’ proprietary antibody-drug conjugate (ADC) technology comprising highly potent synthetic drugs and stable linkers for attaching the drugs to monoclonal antibodies. In addition, Seattle Genetics has three other product candidates in ongoing clinical trials: lintuzumab (SGN-33), dacetuzumab (SGN-40) and SGN-70. Dacetuzumab is being developed under a worldwide collaboration with Genentech (a wholly-owned member of the Roche Group). Seattle Genetics has collaborations for its ADC technology with a number of leading biotechnology and pharmaceutical companies, including Genentech, Bayer, CuraGen, Progenics, Daiichi Sankyo, MedImmune, a subsidiary of AstraZeneca, and Millennium: The Takeda Oncology Company, as well as an ADC co-development agreement with Agensys, a subsidiary of Astellas Pharma. More information can be found at www.seattlegenetics.com.