Seattle Genetics Achieves Milestone Under Millennium Collaboration for European Medicines Agency Acceptance of Brentuximab Vedotin MAA

Seattle Genetics, Inc., (Nasdaq: SGEN) today announced that it will receive a $5 million milestone payment under its brentuximab vedotin (ADCETRIS^TM) collaboration with Millennium: The Takeda Oncology Company, a wholly owned subsidiary of Takeda Pharmaceutical Company Limited (TSE:4502). The milestone was triggered by the European Medicines Agency (EMA) acceptance of the Marketing Authorization Application (MAA) for brentuximab vedotin for the treatment of relapsed or refractory Hodgkin lymphoma and relapsed or refractory systemic anaplastic large cell lymphoma (ALCL). Brentuximab vedotin is an antibody-drug conjugate (ADC) directed to CD30, the defining marker of Hodgkin lymphoma and ALCL.

"The EMA acceptance of the MAA represents a significant achievement in the development of brentuximab vedotin, and takes us another step closer to our goal of bringing this ADC to relapsed or refractory Hodgkin lymphoma and systemic ALCL patients in need around the world,” said Clay B. Siegall, Ph.D., President and Chief Executive Officer at Seattle Genetics. "We also continue to make progress with brentuximab vedotin in the United States, as we interact with the FDA on our two regulatory submissions for these indications. The FDA’s Oncologic Drugs Advisory Committee will review our Biologics License Applications on July 14, 2011, and the action date is August 30, 2011 under the Prescription Drug User Fee Act.”

Under the terms of the collaboration agreement, Seattle Genetics has U.S. and Canadian commercialization rights and the Takeda Group has rights to commercialize brentuximab vedotin in the rest of the world. Seattle Genetics and the Takeda Group are funding joint development costs for brentuximab vedotin on a 50:50 basis, except in Japan where Takeda will be solely responsible for development costs.

About Brentuximab Vedotin

Brentuximab vedotin (ADCETRIS™) is an antibody-drug conjugate (ADC) comprising an anti-CD30 monoclonal antibody attached by a protease-cleavable linker to a potent, synthetic drug, monomethyl auristatin E (MMAE) utilizing Seattle Genetics' proprietary technology. The ADC employs a linker system that is designed to be stable in the bloodstream but to release MMAE upon internalization into CD30-expressing tumor cells. This approach is intended to spare non-targeted cells and thus may help minimize the potential toxic effects of traditional chemotherapy while allowing for the selective targeting of CD30-expressing cancer cells, thus potentially enhancing the antitumor activity.

The U.S. Food and Drug Administration (FDA) has accepted for filing two Biologics License Applications (BLAs) for brentuximab vedotin, including one for the treatment of relapsed or refractory Hodgkin lymphoma and one for the treatment of relapsed or refractory systemic ALCL. The BLAs for brentuximab vedotin are based on results from both a pivotal trial in relapsed or refractory Hodgkin lymphoma and a phase II trial in relapsed or refractory systemic ALCL.

Brentuximab vedotin is also being evaluated in multiple ongoing clinical trials, including a phase III study (the AETHERA trial) for patients at high risk of residual Hodgkin lymphoma following autologous stem cell transplant (ASCT), a phase II retreatment trial for relapsed patients who previously responded to brentuximab vedotin, a phase I combination trial for front-line treatment of Hodgkin lymphoma and a phase I combination trial for front-line systemic ALCL.

About Hodgkin Lymphoma

Lymphoma is a general term for a group of cancers that originate in the lymphatic system. There are two major categories of lymphoma: Hodgkin lymphoma and non-Hodgkin lymphoma. Hodgkin lymphoma is distinguished from other types of lymphoma by the presence of one characteristic type of cell, known as the Reed-Sternberg cell. A defining attribute of the Reed-Sternberg cell is its expression of the CD30 antigen.

According to the American Cancer Society, more than 8,800 cases of Hodgkin lymphoma will be diagnosed in the United States during 2011 and approximately 1,300 people are expected to die from the disease. Although front-line combination chemotherapy can result in durable response rates, up to 30 percent of these patients relapse or are refractory to front-line treatment and have few therapeutic options beyond ASCT.

About Systemic ALCL

ALCL is an aggressive type of T-cell non-Hodgkin lymphoma that highly expresses CD30. Although front-line combination chemotherapy can result in durable remissions, approximately 50 percent of ALCL patients relapse or are refractory to front-line treatment and have few therapeutic options. In the United States, approximately 2,000 systemic ALCL patients are diagnosed annually.

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 FDA has granted priority review to Biologics License Applications for its lead product candidate, brentuximab vedotin, for the treatment of relapsed or refractory Hodgkin lymphoma and relapsed or refractory systemic anaplastic large cell lymphoma, with a PDUFA date of August 30, 2011. Brentuximab vedotin is being developed in collaboration with Millennium: The Takeda Oncology Company. In addition, Seattle Genetics has five other clinical-stage programs: SGN-75, ASG-5ME, ASG-22ME, dacetuzumab (SGN-40) and SGN-70. 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.

Certain of the statements made in this press release are forward looking, such as those, among others, relating to the company’s expectations for regulatory approval and commercial launch of brentuximab vedotin. 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 that the safety and/or efficacy results of our clinical trials of brentuximab vedotin, including our pivotal clinical trial for relapsed or refractory Hodgkin lymphoma and the phase II trial for relapsed or refractory systemic ALCL will not support marketing approval for the submitted indications; that we receive a complete response letter to our BLAs for other reasons, including but not limited to, not satisfactorily completing pre-approval inspections of our contract manufacturers’ or our facilities; major amendments to our marketing application that delay the planned U.S. commercial launch; and that even if we receive approval, we are delayed or unsuccessful in the commercial launch of brentuximab vedotin. Further, brentuximab vedotin may be approved pursuant to the accelerated approval regulations and we may be subject to completing post-marketing requirements and obtaining preapproval of our marketing and promotional materials. We may also fail to achieve milestones under our collaborations and experience unforeseen increased expenses or unexpected reductions in revenues. 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, 2011 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.