Seattle Genetics and Agensys recently completed enrollment in a phase I pancreatic cancer trial of ASG-5ME dosed weekly. The companies plan to evaluate ASG-5ME in patients with gastric cancer based on preclinical expression data.About ASG-5MEASG-5ME is an ADC composed of a fully human antibody directed to SLC44A4, a solute carrier antigen family member identified by Agensys to be overexpressed in epithelial cancers, including more than 80 percent of samples derived from patients with prostate, pancreatic and gastric cancers. The antibody is attached to monomethyl auristatin E (MMAE) via an enzyme-cleavable linker using Seattle Genetics’ proprietary technology. The ADC is designed to be stable in the bloodstream, but to release MMAE upon internalization into SLC44A4-expressing tumor cells, resulting in targeted cell-killing. Seattle Genetics and Agensys are co-developing and will globally co-commercialize and share profits on a 50:50 basis for ASG-5ME and ASG-22ME. Seattle Genetics also has an option for 50:50 cost and profit-sharing of a third ADC program at the time of investigational new drug submission. About AgensysAgensys, Inc., an affiliate of Astellas Pharma Inc., is developing a pipeline of therapeutic fully human monoclonal antibodies (MAbs) to treat cancer. The MAb product pipeline is being generated to Agensys' diverse portfolio of proprietary, clinically relevant cancer targets. Agensys' target portfolio and related products are protected by a large patent estate. The company has full capabilities to generate, develop and manufacture antibody products. Agensys is progressing a pipeline of both naked and antibody-drug conjugated (ADC) therapeutic antibodies, directed at a variety of cancer indications, including those of the prostate, kidney, pancreas, ovary, bladder, lung, colon, breast and skin. ADC products are based on drug platform technologies developed by Seattle Genetics. Agensys is developing a growing pipeline of clinical stage functional MAbs and ADC products. About AstellasAstellas Pharma Inc., located in Tokyo, Japan, is a pharmaceutical company dedicated to improving the health of people around the world through the provision of innovative and reliable pharmaceutical products. Astellas has approximately 17,000 employees worldwide. The organization is committed to becoming a global category leader in urology, immunology & infectious diseases, oncology, neuroscience, DM complications & metabolic diseases. For more information on Astellas Pharma Inc., please visit www.astellas.com/en. About Seattle GeneticsSeattle 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 ® (brentuximab vedotin) 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, Bayer, Celldex Therapeutics, Daiichi Sankyo, Genentech, GlaxoSmithKline, Millennium, Pfizer and Progenics, as well as ADC co-development agreements with Agensys, an affiliate of Astellas, and Genmab. More information can be found at www.seattlegenetics.com. For Seattle Genetics:Certain of the statements made in this press release are forward looking, such as those, among others, relating to further evaluation of ASG-5ME and the initiation of future clinical trials. 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 risk of adverse events as ASG-5ME advances 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 March 31, 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.