Seattle Genetics Announces Initiation of Phase Ib Clinical Trial of SGN-40 in Combination with Rituxan and Gemzar for Non-Hodgkin Lymphoma

04-08-2008

Seattle Genetics, Inc. (Nasdaq:SGEN) announced today that it has initiated a phase Ib clinical trial of SGN-40 in combination with Rituxan(R) (rituximab) and Gemzar(R) (gemcitabine) for patients with relapsed or refractory diffuse large B-cell lymphoma (DLBCL), the most common type of non-Hodgkin lymphoma.

"We are executing on a multi-pronged development plan with SGN-40 in DLBCL, an aggressive type of non-Hodgkin lymphoma, based on data from our phase I single-agent trial with SGN-40 that demonstrated multiple objective antitumor responses in this disease," said Thomas C. Reynolds, M.D., Ph.D., Chief Medical Officer of Seattle Genetics. "The SGN-40 plus Rituxan/Gemzar combination trial complements our other ongoing DLBCL trials, including a phase IIb trial evaluating SGN-40 in combination with Rituxan plus chemotherapy in the second-line setting and a single-agent phase II trial in relapsed or refractory patients. These trials are part of our joint development plan with Genentech, Inc. to broadly assess the potential of SGN-40 in non-Hodgkin lymphoma and multiple myeloma."

The phase Ib, open-label single-arm study will enroll up to approximately 30 patients with relapsed or refractory DLBCL at multiple cancer centers in the United States. Patients will receive escalating doses of SGN-40 in combination with Rituxan and Gemzar. The study will assess safety, pharmacokinetics and preliminary antitumor activity of the combination regimen.

SGN-40 Development Program

SGN-40 is a humanized monoclonal antibody that is currently in phase I and phase II clinical trials for non-Hodgkin lymphoma and multiple myeloma under a worldwide collaboration agreement with Genentech. SGN-40 targets the CD40 antigen, which is expressed on most B-cell lineage hematologic malignancies, as well as solid tumors such as bladder, renal and ovarian cancer.

Seattle Genetics and Genentech are conducting a joint development plan for SGN-40 that includes six ongoing or planned clinical trials of SGN-40 both as a single agent and combined with standard therapies for non-Hodgkin lymphoma and multiple myeloma. The ongoing trials include a phase IIb of SGN-40 in combination with R-ICE (Rituxan, ifosfamide, carboplatin and etoposide) in DLBCL, a phase II single-agent study in DLBCL, a phase Ib of SGN-40 in combination with Rituxan for follicular and marginal zone non-Hodgkin lymphoma and a phase Ib of SGN-40 in combination with Revlimid(R) (lenalidomide) for multiple myeloma.

Under the terms of the collaboration agreement with Genentech, Seattle Genetics received an upfront payment of $60 million in February 2007, and is entitled to receive potential milestone payments exceeding $800 million and escalating double-digit royalties starting in the mid-teens on sales of SGN-40. Seattle Genetics also has an option to co-promote SGN-40 in the United States. Genentech funds research, development, manufacturing and commercialization expenses for SGN-40, including reimbursing Seattle Genetics for costs incurred in connection with activities it funds for the program. To date, Seattle Genetics has earned a total of $20 million in milestone payments from Genentech associated with SGN-40 clinical trial initiations.

About Diffuse Large B-Cell Lymphoma

Non-Hodgkin lymphoma (NHL) represents a diverse group of cancers that develop in the lymphatic system and are characterized by uncontrolled growth and accumulation of abnormal lymphocytes. Lymphocytes are a type of white blood cells that are responsible for defending the body against infection. The most common forms of NHL are follicular (slow growth) and diffuse large B-cell lymphoma (a faster growing sub-type).

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 has a worldwide collaboration with Genentech to develop and commercialize SGN-40. Seattle Genetics also has two other product candidates in ongoing clinical trials: SGN-33 and SGN-35. In addition, the company has developed proprietary antibody-drug conjugate (ADC) technology comprised of highly potent synthetic drugs and stable linkers for attaching the drugs to monoclonal antibodies. Seattle Genetics has collaborations for its ADC technology with a number of leading biotechnology and pharmaceutical companies, including Genentech, Bayer, CuraGen, Progenics and MedImmune, as well as an ADC co-development agreement with Agensys.

Certain of the statements made in this press release are forward-looking, such as those, among others, relating to the therapeutic potential of SGN-40. 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 or activity in this phase I clinical trial and the risk of adverse clinical results as SGN-40 advances in clinical trials. More information about the risks and uncertainties faced by Seattle Genetics is contained in the Company's filings 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.

CONTACT: Seattle Genetics Corporate Communications
Peggy Pinkston, 425-527-4160
ppinkston@seagen.com