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Seattle Genetics Reports Preclinical Data on SGN-40 and an Anti-CD19 Antibody-Drug Conjugate

BOTHELL, Wash.--(BUSINESS WIRE)--Oct 24, 2007 - Seattle Genetics, Inc. (Nasdaq: SGEN) today reported preclinical data on SGN-40, a humanized monoclonal antibody that is currently in clinical trials for non-Hodgkin's lymphoma and multiple myeloma in collaboration with Genentech, Inc. In addition, data were presented by Seattle Genetics on its proprietary anti-CD19 antibody-drug conjugate (ADC) for the treatment of a variety of hematologic malignancies, and several of the company's collaborators presented on their own ADC programs.

The data are being presented at the American Association for Cancer Research-National Cancer Institute-European Organization for Research and Treatment of Cancer (AACR-NCI-EORTC) International Conference on Molecular Targets and Cancer Therapeutics being held in San Francisco, CA.

Seattle Genetics' researchers presented preclinical data elucidating two mechanisms by which SGN-40 signals cell death (apoptosis) in models of non-Hodgkin's lymphoma. Through independent mechanisms of action, SGN-40 causes depletion of an important survival signal (BCL-6) for cancer cells and also increases the level of another protein (Tap63a) thought to enhance susceptibility of tumor cells to chemotherapy. This is the first report of a therapeutic antibody able to modulate both of these pathways (Abstract #B63). Planned clinical trials in non-Hodgkin's lymphoma and multiple myeloma will exploit these signaling properties by combining SGN-40 with a number of standard therapies.

Researchers also presented preclinical data for the first time on the company's proprietary anti-CD19 ADC program. The anti-CD19 ADCs were shown to effectively bind to target cells with high affinity, internalize and induce potent cancer-cell-killing activity. Data also demonstrated durable tumor regressions at low doses in multiple cancer models (Abstract #B60). The CD19 antigen is a pan-B cell marker expressed on many hematologic malignancies.

"The promising data from our anti-CD19 ADC program suggests that this compound has therapeutic potential for multiple types of cancer, including non-Hodgkin's lymphoma, chronic lymphocytic leukemia and acute lymphoblastic leukemia," said Clay B. Siegall, President and Chief Executive Officer at Seattle Genetics. "This program is an important component of our increasingly broad and diverse pipeline, and combines the potency of our ADC technology with our expertise in developing therapies to address unmet needs in hematologic cancers."

Several of Seattle Genetics' collaborators are presenting data on programs utilizing the company's ADC technology, including:

-- CuraGen is presenting data from its ongoing phase I clinical trial of CR011-vcMMAE for the treatment of metastatic melanoma (Abstract B47), as well as preclinical findings on the program (Abstract A68).

-- MedImmune is reporting preclinical data from its ADC targeted to EphA2 for solid tumors (Abstract B61).

Seattle Genetics' ADC technology empowers antibodies by linking them to potent drug payloads. The company's technology employs synthetic, highly potent drugs that are bound to monoclonal antibodies through proprietary linker systems. The linkers are designed to be stable in the bloodstream but to release the drug payload under specific conditions once inside target cells, thereby sparing non-target cells from the toxic effects of traditional chemotherapy.

Downloadable copies of Seattle Genetics' posters are available from the "Technology" section of the company's website at

About Seattle Genetics

Seattle Genetics is a biotechnology company developing monoclonal antibody-based therapies for the treatment of multiple types of cancer, including lymphoma, multiple myeloma, leukemia and solid tumors. The company has an exclusive worldwide collaboration agreement with Genentech to develop and commercialize SGN-40. Seattle Genetics also has three other proprietary programs in ongoing clinical trials: SGN-33, SGN-35 and SGN-30. 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. More information can be found at

Certain of the statements made in this press release are forward-looking, such as those, among others, relating to the potential therapeutic potential of Seattle Genetics' product candidates and ADC technology. 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 related to adverse clinical results as our product candidates move into and advance in clinical trials, risks inherent in early stage development and failure by Seattle Genetics' collaborators to advance product candidates incorporating its technology. More information about the risks and uncertainties faced by Seattle Genetics is contained in Seattle Genetics' 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.


Seattle Genetics, Inc.
Peggy Pinkston, Corporate Communications

Posted: October 2007