Data Show Longer Duration of Responses and Concordance between Investigator-Assessed and Independent Review of Responses

BOTHELL, WA, USA I June 8, 2009 I Seattle Genetics, Inc. (Nasdaq: SGEN) today reported data from a phase I clinical trial of SGN-35 administered every three weeks to patients with Hodgkin lymphoma and other CD30-positive hematologic malignancies. Data highlights include longer median duration of response than previously reported and concordance between investigator-assessed and independent review of responses. The data were presented at the 14th Congress of the European Hematology Association (EHA) being held in Berlin, Germany.

“These maturing phase I data continue to reinforce our belief in the therapeutic potential of SGN-35,” said Thomas C. Reynolds, M.D., Ph.D., Chief Medical Officer of Seattle Genetics. “The lengthening duration of responses and the high level of concordance between investigator-assessed and independently reviewed response data are important in bolstering our development plans, including our ongoing pivotal trial of SGN-35 in relapsed and refractory Hodgkin lymphoma.”

SGN-35 Phase I Trial

In the phase I dose-escalation study, cohorts of patients received doses of SGN-35 every three weeks, ranging from 0.1 milligrams per kilogram (mg/kg) to 3.6 mg/kg. The median age of patients was 36 years. Enrolled patients had received a median of three prior chemotherapy regimens and 73 percent had received a prior autologous stem cell transplant. Forty-four patients were evaluable for response, including 41 with Hodgkin lymphoma, two with systemic anaplastic large cell lymphoma (ALCL) and one with angioimmunoblastic T-cell lymphoma.

The objective response rate across all dose levels based on investigator assessment was 39 percent, compared to 41 percent based on independent review. For patients treated at doses of 1.2 mg/kg and higher, the overall response rate was 54 percent based on investigator assessment, compared to 57 percent based on independent review. Currently, the median duration of response is at least 7.3 months with eight patients remaining in ongoing response. SGN-35 was generally well tolerated. The majority of adverse events were Grade 1 and 2, with the most common being fatigue, fever, peripheral neuropathy, diarrhea and nausea.

Seattle Genetics is advancing an ongoing pivotal trial of SGN-35 administered every three weeks for relapsed and refractory Hodgkin lymphoma and a planned phase II trial for systemic anaplastic large cell lymphoma. The pivotal trial is being conducted under a Special Protocol Assessment (SPA) with the U.S. Food and Drug Administration (FDA). SGN-35 is an antibody-drug conjugate (ADC) comprising an anti-CD30 antibody attached by an enzyme-cleavable linker to a potent, synthetic drug payload, monomethyl auristatin E (MMAE), using Seattle Genetics’ proprietary technology. The ADC is designed to be stable in the bloodstream, but to release MMAE upon internalization into CD30-expressing tumor cells, resulting in targeted cell-killing.

About CD30-Positive 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. According to the American Cancer Society, approximately 8,500 cases of Hodgkin lymphoma will be diagnosed in the United States during 2009. Anaplastic large cell lymphoma is a T-cell non-Hodgkin lymphoma that expresses the CD30 antigen.

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’s lead product candidate, SGN-35, is in a pivotal trial under an SPA with the FDA. SGN-35 is empowered by Seattle Genetics’ proprietary ADC technology comprising highly potent synthetic drugs and stable linkers for attaching the drugs to monoclonal antibodies. In addition, Seattle Genetics has three other product candidates in ongoing clinical trials: dacetuzumab (SGN-40), lintuzumab (SGN-33) and SGN-70. Dacetuzumab is being developed under a worldwide collaboration with Genentech (a wholly owned member of the Roche Group). Seattle Genetics has collaborations for its ADC technology with a number of leading biotechnology and pharmaceutical companies, including Genentech, Bayer, CuraGen, Progenics, Daiichi Sankyo, MedImmune, a subsidiary of AstraZeneca, and Millennium: The Takeda Oncology Company, as well as an ADC co-development agreement with Agensys, a subsidiary of Astellas Pharma. More information can be found at www.seattlegenetics.com.

Certain of the statements made in this press release are forward looking, such as those, among others, relating to the potential therapeutic benefit, regulatory pathway and development timelines of SGN-35. 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, among others: that the company may experience delays in the initiation and/or completion of the clinical trials of SGN-35 in Hodgkin lymphoma and anaplastic large cell lymphoma, whether caused by competition, adverse events, patient enrollment rates, regulatory issues or other factors; that data from our phase I clinical trials of SGN-35 may not necessarily be indicative of the subsequent clinical trial results, including our pivotal clinical trial results; and that the safety and/or efficacy results of these trials, including the SGN-35 pivotal clinical trial for relapsed or refractory Hodgkin lymphoma, will not support an application for marketing approval in the United States or any other country. More information about the risks and uncertainties faced by Seattle Genetics is contained in the company’s 10-K for the year ended December 31, 2008 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.

Source: Seattle Genetics, Inc.

Seattle Genetics, Inc.
Peggy Pinkston, 425-527-4160
ppinkston@seagen.com

 

SOURCE: Seattle Genetics