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Seattle Genetics Presents Preclinical Data on its Antibody-Drug Conjugate Technology and SGN-33 Program at AACR

BOTHELL, Wash. & SAN DIEGO--(BUSINESS WIRE)-- Seattle Genetics, Inc. (NASDAQ:SGEN) today announced data from multiple poster presentations at the 2008 Annual Meeting of the American Association for Cancer Research (AACR) highlighting preclinical findings with its proprietary antibody-drug conjugate (ADC) technology. Preclinical data were also presented on SGN-33, a humanized antibody that is in clinical trials for acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS).

"These AACR presentations demonstrate continued progress with our ADC programs, as well as our commitment to remaining a leader in empowering antibodies through ongoing research into future generations of ADC technology designed to further enhance the platform," said Clay B. Siegall, Ph.D., President and Chief Executive Officer at Seattle Genetics. "The promising clinical data we have observed with SGN-35 reinforces our enthusiasm for our preclinical pipeline of ADC product candidates, including SGN-75 and an anti-CD19 ADC."

ADCs are monoclonal antibodies linked to cell-killing drugs. Seattle Genetics' ADC 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 many of the toxic effects of traditional chemotherapy. Seattle Genetics' lead ADC, SGN-35, is in phase I clinical trials for patients with Hodgkin lymphoma or other CD30-positive hematologic malignancies. The company plans to report phase I data, including multiple objective responses, at the American Society of Clinical Oncology (ASCO) annual meeting in early June.

ADC Technology

Researchers reported preclinical data at AACR indicating the effectiveness of SGN-75 in targeting and delivering its auristatin drug payload into CD70-expressing tumors, where it is selectively retained as compared to normal tissues (Abstract #4063). Additional data were reported demonstrating the potent antitumor activity of SGN-75 in multiple solid tumor models, including renal cell cancer (Abstract #4064). SGN-75 is an anti-CD70 ADC that Seattle Genetics is advancing towards clinical trials in solid tumors and hematologic malignancies.

Data were also reported on Seattle Genetics' research into novel linkers for use with auristatins that can enhance the potency and tolerability of ADCs (Abstract #4907).

SGN-33 Program

Data were presented at AACR indicating SGN-33's ability to increase survival in multi-drug resistant (MDR)-positive preclinical models of AML that are characteristically resistant to chemotherapy. SGN-33 was shown to mediate effector function and reduce cytokine production in correlation with its antitumor activity in these models (Abstract #1513).

SGN-33 is a humanized monoclonal antibody in three ongoing clinical trials: a single-agent phase Ib trial for AML and MDS, a phase IIb combination study with low-dose cytarabine for the treatment of AML patients 60 years of age and older and a phase I trial in combination with Revlimid® (lenalidomide) for advanced MDS.

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

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 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 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.


Seattle Genetics, Inc.
Peggy Pinkston, Corporate Communications

Posted: April 2008