Seattle Genetics to Receive $12 Million Upfront Payment, up to $390 Million in Potential Milestone Payments and Mid-Single Digit Royalties

BOTHELL, WA, USA | December 21, 2009 | Seattle Genetics, Inc. (NASDAQ:SGEN), announced today that it has entered into a collaboration agreement with GlaxoSmithKline (GSK) under which GSK will pay an upfront fee of $12 million for rights to utilize Seattle Genetics’ antibody-drug conjugate (ADC) technology with multiple antigens to be named by GSK.

"By collaborating with leading companies such as GSK, we are broadening the reach of our proprietary ADC technology while also generating substantial non-dilutive capital for Seattle Genetics," said Eric L. Dobmeier, Chief Business Officer of Seattle Genetics. "We now have nine ADC licensees and we have generated more than $35 million during 2009 from new and ongoing ADC collaborations."

GSK is responsible for research, product development, manufacturing and commercialization of all ADC products under the collaboration. Seattle Genetics is eligible to receive from GSK up to $390 million in milestones if all ADCs in the collaboration are commercialized as well as mid-single digit royalties on worldwide net sales of any resulting ADC products. Seattle Genetics also will receive material supply and annual maintenance fees as well as research support payments for assistance provided to GSK under the collaboration.

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.

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: 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 Genentech, Bayer, CuraGen, a subsidiary of Celldex Therapeutics, Progenics, Daiichi Sankyo, MedImmune, a subsidiary of AstraZeneca, and Millennium: The Takeda Oncology Company, as well as an ADC co-development agreement with Agensys, an affiliate of Astellas. More information can be found at http://cts.businesswire.com/ct/CT?id=smartlink&url=http%3A%2F%2Fwww.seattlegenetics.com&esheet=6124831&lan=en_US&anchor=www.seattlegenetics.com&index=1&md5=c201d100ccba115fcca02787701d4bcf.

SOURCE: Seattle Genetics, Inc.