Seattle Genetics and Millennium Present Updated Brentuximab Vedotin (SGN-35) Data at ASCO Annual Meeting

Chicago, IL – June 6, 2011 – Seattle Genetics, Inc. (Nasdaq: SGEN) and Millennium: The Takeda Oncology Company, a wholly owned subsidiary of Takeda Pharmaceutical Company Limited (TSE:4502), today reported updated data from a pivotal trial of brentuximab vedotin (ADCETRIS™) in relapsed or refractory Hodgkin lymphoma and a phase II trial in relapsed or refractory systemic anaplastic large cell lymphoma (ALCL). Brentuximab vedotin is an antibody-drug conjugate (ADC) directed to CD30, a defining marker of Hodgkin lymphoma and systemic ALCL, and a target also expressed in other malignancies. The updated data were presented today during poster presentations at the American Society of Clinical Oncology (ASCO) 2011 Annual Meeting being held in Chicago, IL.

In a pivotal trial of 102 relapsed or refractory Hodgkin lymphoma patients who had failed prior autologous stem cell transplant (ASCT), an independent review facility (IRF) evaluated the overall objective response rate and duration of responses. Per IRF, it was previously reported that 75 percent of patients achieved an objective response, including 34 percent with a complete remission (CR). The median duration of response for all responding patients was 6.7 months, and the median duration of response for patients achieving a CR had not yet been reached. In these updated data presented at ASCO based on additional patient follow-up, the median duration of response in patients with a CR was 20.5 months per IRF. At the time of last data analysis, 21 patients with a CR were alive and free of progression. The estimated 12-month overall survival for all patients was 89 percent. Patient follow-up is ongoing. (Abstract #8031)

In a phase II trial of 58 relapsed or refractory systemic ALCL patients, it was previously reported that, per IRF, 86 percent of patients achieved an objective response, including 53 percent with a CR. When previously reported, the median duration of response for all responding patients and for patients with a CR had not yet been reached. In updated data presented at ASCO based on additional patient follow-up, the rate of CRs per IRF increased to 57 percent. The median duration of overall objective response was 12.6 months and the median duration of response in patients with a CR was 13.2 months, both per IRF. Median overall survival had not been reached. Patient follow-up is ongoing. (Abstract #8032)

Across both trials, brentuximab vedotin treatment was associated with generally manageable adverse events. The most common adverse events of any Grade in the pivotal Hodgkin lymphoma trial were peripheral sensory neuropathy (47 percent), fatigue (46 percent), nausea (42 percent), upper respiratory tract infection (37 percent) and diarrhea (36 percent). The most common adverse events of any Grade in the phase II systemic ALCL trial were peripheral sensory neuropathy (41 percent), nausea (40 percent), fatigue (38 percent), fever (34 percent) and diarrhea (29 percent).

“The durability of the complete remissions among these highly treatment-refractory Hodgkin lymphoma patients is clinically meaningful, as it is uncommon for single-agent treatment to achieve complete remissions with a duration of more than 18 months,” said Dr. Robert Chen, Assistant Professor, Hematology & Hematopoietic Cell Transplantation at City of Hope and the 2010-2011 recipient of the Tim Nesvig Research Fellowship in Lymphoma. “There is a substantial unmet medical need in this setting, evidenced by historical data showing that almost half of Hodgkin lymphoma patients who relapse following ASCT will survive less than two years. The activity and tolerability data with brentuximab vedotin suggest that, if approved, brentuximab vedotin could be an important option for relapsed or refractory patients.”

“Systemic ALCL is an aggressive type of T-cell non-Hodgkin lymphoma for which there is a pronounced unmet need, particularly for patients with highly refractory disease such as those in this clinical trial,” said Dr. Andrei Shustov, Assistant Professor of Hematology at the University of Washington School of Medicine and Attending Physician in the Hematologic Malignancies Program at the Seattle Cancer Care Alliance. “The overall response rate of 86 percent previously reported, combined with the new duration of response data presented at ASCO, continue to support the clinical development of brentuximab vedotin for relapsed or refractory systemic ALCL patients. These data also provide rationale for future clinical studies in other CD30-positive tumors.”

About the Brentuximab Vedotin Trials

The pivotal Hodgkin lymphoma and phase II systemic ALCL trials were designed to assess the efficacy and safety of single-agent brentuximab vedotin in relapsed or refractory patients. Patients received 1.8 milligrams per kilogram of brentuximab vedotin every three weeks until disease progression, or up to a maximum of 16 total doses. The primary endpoint of both trials was objective response rate as assessed by an independent central review. Secondary endpoints included complete response rate, duration of response, progression-free survival, overall survival and tolerability.

In the pivotal Hodgkin lymphoma trial, the median age of patients was 31 years. Patients had received a median of 3.5 prior chemotherapy regimens. Seventy-one percent of patients were primary refractory, defined as patients who failed to achieve a complete remission to front-line chemotherapy or had relapsed within three months of receiving front-line chemotherapy. Forty-two percent of patients were refractory to their most recent prior therapy, and all patients had progressed following prior ASCT.

In the phase II systemic ALCL trial, the median age of patients was 52 years. Enrolled patients had received a median of two prior chemotherapy regimens. Sixty-two percent of patients were primary refractory. Seventy-two percent of patients were anaplastic lymphoma kinase (ALK) negative, generally suggesting a poor prognosis. Twenty-two percent of patients had not responded to any prior treatment, and 26 percent had failed prior autologous stem cell transplant.

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.

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.

About Systemic ALCL

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. ALCL is an aggressive type of T-cell non-Hodgkin lymphoma that highly expresses CD30.

About the Seattle Genetics/Millennium Collaboration

Seattle Genetics is jointly developing brentuximab vedotin with Millennium: The Takeda Oncology Company. 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 the Takeda Group will be solely responsible for development costs.

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 four other clinical-stage programs: SGN-75, ASG-5ME, 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.

About Millennium

Millennium: The Takeda Oncology Company, a leading biopharmaceutical company based in Cambridge, Mass., markets a first-in-class proteasome inhibitor in the US, and has a robust clinical development pipeline of global 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 and Takeda are available through their respective websites, www.millennium.com and www.takeda.com.

About Takeda

Located in Osaka, Japan, Takeda is a research-based global company with its main focus on pharmaceuticals. As the largest pharmaceutical company in Japan and one of the global leaders of the industry, Takeda is committed to strive towards better health for patients worldwide through leading innovation in medicine. Additional information about Takeda is available through its corporate website, www.takeda.com.

For Seattle Genetics: 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 and 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 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. 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.

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CONTACTS:
Seattle Genetics
Peggy Pinkston
425- 527- 4160
ppinkstonseagen.com

Millennium
Manisha Pai
617- 551- 7877
manisha.paimpi.com

Takeda
Corporate Communications Department
(81)- 3- 3278- 2037