Press Release

Seattle Genetics to Receive $9.5 Million Payment from Genentech to Extend Antibody-Drug Conjugate Collaboration

BOTHELL, Wash., Apr 20, 2010 (BUSINESS WIRE) --Seattle Genetics, Inc. (Nasdaq: SGEN) today announced that Genentech, Inc., a wholly owned member of the Roche Group (SIX: RO, ROG; OTCQX: RHHBY), will pay $9.5 million to renew exclusive licenses to specific targets and extend the research term under the parties' existing antibody-drug conjugate (ADC) collaboration agreement. Under the terms of the agreement, Genentech has rights to use Seattle Genetics' ADC technology with antibodies against targets selected by Genentech. Genentech is responsible for research, product development, manufacturing and commercialization. Seattle Genetics is entitled to receive fees, progress-dependent milestone payments and royalties on net sales of any resulting ADC products.

"We believe this collaboration, coupled with our multiple other ADC collaborations, reinforces the value of our industry-leading technology," said Eric L. Dobmeier, Chief Business Officer of Seattle Genetics. "For Seattle Genetics, these collaborations broaden the reach of our technology into diverse disease settings where empowered antibodies may be able to address significant unmet medical needs. In addition, these deals provide a substantial source of capital as we continue to advance our own pipeline of proprietary antibodies and ADCs for cancer."

Seattle Genetics has generated approximately $120 million through ADC technology license agreements with leading biotechnology and pharmaceutical companies. ADCs utilize the targeting ability of monoclonal antibodies to deliver potent, cell-killing payloads to specific cells. Seattle Genetics' proprietary technology employs synthetic, highly potent drugs attached to antibodies through stable linker systems. The linkers are designed to release the drug payload only under specific conditions once inside target cells, thereby sparing non-target cells many of the toxic effects of traditional chemotherapy.

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 U.S. Food and Drug Administration. Brentuximab vedotin is being developed in collaboration with Millennium: 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. Actual results or developments may differ materially from those projected or implied in these forward-looking statements. Specifically, statements regarding the therapeutic potential of antibody-drug conjugates are forward-looking and actual results may differ materially from these statements for various reasons. Factors that may cause such a difference include risks related to adverse clinical results as our product candidates move into and advance in clinical trials, risks inherent in early stage development and failure by our collaborators to perform their contractual obligations or advance products incorporating our technology. More information about the risks and uncertainties faced by Seattle Genetics is contained in the company's annual report on Form 10-K for the year ended December 31, 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