Seattle Genetics Expands Antibody-Drug Conjugate Collaboration with Abbott

Seattle Genetics Expands Antibody-Drug Conjugate Collaboration with Abbott

Bothell, WA – October 23, 2012 – Seattle Genetics, Inc. (Nasdaq: SGEN) today announced that it has expanded its antibody-drug conjugate (ADC) collaboration with Abbott (NYSE: ABT). Under the expanded deal, Abbott will pay an upfront fee of $25 million for rights to utilize Seattle Genetics' auristatin-based ADC technology with antibodies to additional oncology targets. In addition, Seattle Genetics may receive up to $220 million in potential milestone payments per additional target upon achieving predetermined development and commercial objectives, as well as mid-to-high single-digit royalties on worldwide net sales of any resulting products under the multi-target collaboration.

"ADCs have emerged as an important therapeutic approach to cancer, driven by the FDA approval of ADCETRIS®, and encouraging data from numerous clinical and preclinical ADC programs in development by Seattle Genetics and our collaborators," said Natasha Hernday, Vice President, Corporate Development at Seattle Genetics. "We are leading the field in ADC development, and this expanded collaboration with Abbott further validates our technology and approach in targeting and treating cancer."

Seattle Genetics and Abbott originally entered into an ADC collaboration in March 2011 under which Abbott paid an upfront fee of $8 million for rights to utilize Seattle Genetics' ADC technology with antibodies to a single oncology target. Abbott is responsible for research, product development, manufacturing and commercialization of any ADC products under the expanded collaboration. In addition to the upfront payment and potential milestone payments and royalties, Seattle Genetics will receive annual maintenance fees and research support payments for assistance provided to Abbott under the collaboration.

ADCs are monoclonal antibodies that are designed to selectively deliver cytotoxic agents to tumor cells. With over a decade of experience and knowledge in ADC innovation, Seattle Genetics has developed proprietary technology employing synthetic cytotoxic agents, such as monomethyl auristatin E (MMAE) and monomethyl auristatin F (MMAF), and stable linker systems that attach these cytotoxic agents to the antibody. Seattle Genetics' linker systems are designed to be stable in the bloodstream and release the potent cell-killing agent once inside targeted cancer cells. This approach is intended to spare non-targeted cells and thus reduce many of the toxic effects of traditional chemotherapy while enhancing antitumor activity. ADCETRIS (brentuximab vedotin) is the first drug approved utilizing Seattle Genetics' ADC technology.

About Seattle Genetics
Seattle Genetics is a biotechnology company focused on the development and commercialization of monoclonal antibody-based therapies for the treatment of cancer. The U.S. Food and Drug Administration granted accelerated approval of ADCETRIS in August 2011 for two indications. ADCETRIS is being developed in collaboration with Millennium: The Takeda Oncology Company. In addition, Seattle Genetics has three other clinical-stage ADC programs: SGN-75, ASG-5ME and ASG-22ME. Seattle Genetics has collaborations for its ADC technology with a number of leading biotechnology and pharmaceutical companies, including Abbott, Agensys (an affiliate of Astellas), Bayer, Celldex Therapeutics, Daiichi Sankyo, Genentech, GlaxoSmithKline, Millennium, Pfizer and Progenics, as well as ADC co-development agreements with Agensys and Genmab. Across Seattle Genetics' internal and collaborator programs, there are more than 15 ADCs in clinical development utilizing the company's technology. More information can be found at 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 and future clinical progress, regulatory approval and commercial launch of products utilizing Seattle Genetics' ADC technology. 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 risks related to adverse clinical results as our product candidates or our collaborators' product candidates move into and advance in clinical trials, risks inherent in early stage development and failure by Seattle Genetics to secure or maintain relationships with collaborators. More information about the risks and uncertainties faced by Seattle Genetics is contained in the Company's quarterly report on Form 10-Q for the quarter ended June 30, 2012 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.