Seattle Genetics and Millennium Announce Initiation of Phase I Combination Clinical Trial of Brentuximab Vedotin (SGN-35) for Front-line Hodgkin Lymphoma

Seattle Genetics, Inc. (Nasdaq: SGEN) and Millennium Pharmaceuticals, Inc.: The Takeda Oncology Company today announced that they have initiated a phase I clinical trial of brentuximab vedotin (SGN-35) in combination with chemotherapy for the treatment of newly diagnosed Hodgkin lymphoma patients. Brentuximab vedotin is an antibody-drug conjugate (ADC) that is also in single-agent clinical trials, including a pivotal trial for relapsed and refractory Hodgkin lymphoma and a phase II trial for systemic anaplastic large cell lymphoma. The target for brentuximab vedotin is CD30, which is expressed on these hematologic malignancies. The phase I combination trial will evaluate brentuximab vedotin plus Adriamycin (doxorubicin), bleomycin, vinblastine and dacarbazine (ABVD), a commonly used front-line chemotherapy regimen for Hodgkin lymphoma.

"We believe this is an important first step in our investigation of brentuximab vedotin in earlier stage Hodgkin lymphoma patients, towards our ultimate goal of determining the potential of brentuximab vedotin to improve patient outcomes,” said Thomas C. Reynolds, M.D., Ph.D., Chief Medical Officer of Seattle Genetics. "In preclinical studies, including in models with high tumor burden, our data demonstrate that brentuximab vedotin combined with ABVD results in improved antitumor activity compared to ABVD alone, providing a foundation on which to explore this combination in the clinical setting.”

"Millennium is pleased to be collaborating with Seattle Genetics on brentuximab vedotin, and we are excited about this molecule’s potential in Hodgkin lymphoma,” said Nancy Simonian, M.D., Chief Medical Officer at Millennium. "Millennium and Seattle Genetics have a shared goal to develop innovative new medicines where there is an unmet need for patients.”

The phase I dose-escalation trial will evaluate the safety of combining brentuximab vedotin and ABVD, as well as assess pharmacokinetics and the antitumor activity of the combination. The study is expected to enroll approximately 40 patients at multiple centers in the United States and Canada.

Seattle Genetics is conducting an ongoing pivotal trial of brentuximab vedotin for relapsed and refractory Hodgkin lymphoma. The trial is being conducted under a Special Protocol Assessment (SPA) with the U.S. Food and Drug Administration (FDA), and top-line data are planned in the second half of 2010. In addition, the company is conducting an ongoing phase II trial for relapsed and refractory systemic anaplastic large cell lymphoma and a phase II retreatment trial for relapsed patients who previously responded to brentuximab vedotin therapy. The company also plans to initiate a phase III relapse prevention trial for post-transplant Hodgkin lymphoma patients in the first half of 2010.

Seattle Genetics is developing brentuximab vedotin in collaboration with Millennium Pharmaceuticals, Inc.: The Takeda Oncology Company, under which Seattle Genetics has U.S. and Canadian commercialization rights and Millennium has rights to commercialize brentuximab vedotin in the rest of the world. Seattle Genetics and Millennium are jointly funding worldwide development costs for brentuximab vedotin on a 50:50 basis.

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 pathologically 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, approximately 8,500 cases of Hodgkin lymphoma were to be diagnosed in the United States during 2009.

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 an SPA with the FDA. Brentuximab vedotin is being developed in collaboration with Millennium Pharmaceuticals, Inc.: 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, Celldex Therapeutics, Progenics, Daiichi Sankyo, MedImmune, a subsidiary of AstraZeneca, Millennium: The Takeda Oncology Company and GlaxoSmithKline, as well as an ADC co-development agreement with Agensys, an affiliate of Astellas. More information can be found at www.seattlegenetics.com.

About Millennium

Millennium Pharmaceuticals, Inc.: The Takeda Oncology Company, a leading biopharmaceutical company based in Cambridge, Mass., markets a first-in-class proteasome inhibitor, and has a robust clinical development pipeline of product candidates. Millennium Pharmaceuticals, Inc. was acquired by Takeda Pharmaceutical Company Ltd. in May, 2008. The Company’s research, development and commercialization activities are focused in oncology. Additional information about Millennium is available through its website, www.millennium.com.

Certain of the statements made in this press release are forward looking, such as those, among others, relating to the therapeutic and commercial potential of brentuximab vedotin in combination with chemotherapy and in front-line settings. 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 inability to show sufficient safety in the phase I combination clinical trial and the risk of adverse clinical results as brentuximab vedotin 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 September 30, 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.

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