Seattle Genetics Announces Upcoming SGN-35 Presentation at the American Society of Clinical Oncology Annual Meeting

Seattle Genetics, Inc. (Nasdaq: SGEN) announced today that SGN-35 phase I clinical data will be presented during a poster discussion session at the 44th American Society of Clinical Oncology (ASCO) Annual Meeting being held May 30 to June 3, 2008 at the McCormick Place Convention Center in Chicago, Illinois. The abstract, titled "Objective responses in a phase I dose-escalation study of SGN-35, a novel antibody-drug conjugate (ADC) targeting CD30, in patients with relapsed or refractory Hodgkin lymphoma” (Abstract #8526), is available on the ASCO website at www.asco.org. The ASCO poster presentation, scheduled for June 3, 2008, will provide updated clinical data beyond those in the abstract, including tolerability profile and objective antitumor responses in additional patients treated with SGN-35. At the time of abstract submission, 29 patients had been enrolled, including 26 with Hodgkin lymphoma and three with other CD30-positive hematologic malignancies. SGN-35 dose levels ranged from 0.1 to 2.7 milligrams per kilogram (mg/kg). Of 28 patients evaluable for response, nine had partial remissions. Stable disease was observed in 11 patients and eight patients had progressive disease. At dose levels of =1.2 mg/kg, seven of 13 patients (54 percent) achieved partial remissions. SGN-35 was generally well tolerated. The most common related adverse events were Grade 1 and 2, including fatigue and cough. SGN-35 is an ADC that utilizes Seattle Genetics’ proprietary technology to empower antibodies by linking them to potent cell-killing drugs. SGN-35 is in phase I clinical trials for patients with Hodgkin lymphoma and other CD30-positive hematologic malignances. 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 for 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 comprising 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, a wholly owned subsidiary of Astellas Pharma.