Press Release

Seattle Genetics Achieves Milestone under Antibody-Drug Conjugate Collaboration with Genentech

BOTHELL, Wash., Mar 03, 2010 (BUSINESS WIRE) -- Seattle Genetics, Inc. (Nasdaq: SGEN) announced today that it has achieved a milestone under its antibody-drug conjugate (ADC) collaboration with Genentech, Inc., a wholly owned member of the Roche Group (SIX: RO, ROG; OTCQX: RHHBY). The milestone was triggered by Genentech's submission of an Investigational New Drug (IND) application with the U.S. Food and Drug Administration (FDA) for an ADC utilizing Seattle Genetics' technology for the treatment of cancer.

"This IND submission is reflective of the continued progress by our collaborators in the development of product candidates based on our proprietary ADC technology," said Eric L. Dobmeier, Chief Business Officer of Seattle Genetics. "We are pleased that Genentech has advanced an ADC program using our technology towards clinical trials. We believe this further demonstrates the potential of ADCs to play an increasingly important role in the treatment of cancer and other serious diseases."

ADCs are empowered monoclonal antibodies that carry potent, cell-killing drugs. Seattle Genetics has developed proprietary technology employing synthetic, highly potent drugs that can be attached to antibodies through stable linker systems. The linkers are designed to be stable in the bloodstream and release the drugs under specific conditions once inside targeted cells. This approach is intended to spare non-targeted cells and thus reduce many of the toxic effects of traditional chemotherapy. To date, Seattle Genetics has generated approximately $110 million through ADC technology license agreements with leading biotechnology and pharmaceutical companies.

Under the terms of the ADC collaboration agreement, Genentech has rights to use Seattle Genetics' ADC technology with monoclonal antibodies against targets selected by Genentech. Genentech is responsible for research, product development, manufacturing and commercialization activities under the collaboration. Seattle Genetics is entitled to receive fees, progress-dependent milestone payments and royalties on net sales of any resulting ADC products.

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, is in a pivotal trial under a special protocol assessment with the FDA. Brentuximab vedotin is being developed in collaboration with Millennium Pharmaceuticals, Inc.: The Takeda Oncology Company. In addition, Seattle Genetics has four other product candidates in ongoing clinical trials: lintuzumab (SGN-33), dacetuzumab (SGN-40), SGN-70 and SGN-75. Seattle Genetics has collaborations for its ADC technology with a number of leading biotechnology and pharmaceutical companies, including Bayer, Celldex Therapeutics, Daiichi Sankyo, Genentech, GlaxoSmithKline, MedImmune, a subsidiary of AstraZeneca, Millennium: The Takeda Oncology Company, and Progenics, as well as an ADC co-development agreement with Agensys, an affiliate of Astellas. More information can be found at http://www.seattlegenetics.com.

Certain of the statements made in this press release are forward looking, such as those, among others, relating to the therapeutic potential of Seattle Genetics' ADC technology and the potential for our collaborators to advance their ADC product candidates. 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 the inability to show sufficient safety or activity as our or our collaborators' ADC product candidates move into and advance in clinical trials. More information about the risks and uncertainties faced by Seattle Genetics is contained in the company's 10-Q for the quarter ended September 30, 2009 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.

SOURCE: Seattle Genetics, Inc.

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