Seattle Genetics Receives Orphan Drug Designation for SGN-30 in T-Cell Lymphomas.

Business Editors/Health/Medical Writers

BOTHELL, Wash.--(BUSINESS WIRE)--Feb. 26, 2004

Seattle Genetics, Inc. (Nasdaq:SGEN) announced today that the U.S. Food and Drug Administration (FDA) has granted orphan drug designation to its product candidate SGN-30 for T-cell lymphomas, a category of non-Hodgkin's lymphoma that includes anaplastic and cutaneous lymphoma. SGN-30 is a monoclonal antibody currently in phase II clinical trials for the treatment of anaplastic large cell lymphoma and Hodgkin's disease. The FDA previously granted SGN-30 orphan drug designation for Hodgkin's disease in July 2003. Seattle Genetics plans to initiate a phase II study of SGN-30 in cutaneous lymphoma later in 2004.

"We are focused on the rapid development of SGN-30 due to its potential for the treatment of CD30-expressing hematologic malignancies, including Hodgkin's disease and T-cell lymphomas," commented Clay B. Siegall, Ph.D., President and Chief Executive Officer of Seattle Genetics. "These orphan drug designations provide us with a number of benefits that further strengthen our SGN-30 program."

The Orphan Drug Act is intended to encourage companies to develop therapies for the treatment of diseases that affect fewer than 200,000 individuals in the United States. Orphan drug designation, granted by the FDA's Office of Orphan Products Development, provides Seattle Genetics with the opportunity to obtain grant funding from the U.S. government to defray costs of clinical trial expenses, tax credits for clinical research expenses, potential waiver of the FDA's application user fee and seven years of marketing exclusivity in the event of market approval.

About Lymphomas

Lymphoma is a general term for a group of cancers that originate in the lymphatic system. According to the American Cancer Society, approximately 54,300 new cases of non-Hodgkin's lymphoma, of which an estimated 15% are of T-cell origin, and 7,800 new cases of Hodgkin's disease will be diagnosed in the United States during 2004. In addition, the prevalence of both types of lymphoma is significantly higher. Due to the limited therapeutic options for refractory or relapsed lymphoma patients, there are significant opportunities for new treatments in these patient populations.

About Seattle Genetics

Seattle Genetics discovers and develops monoclonal antibody-based therapeutics to treat cancer and other human diseases. The company has built a diverse portfolio of product candidates targeted to many types of cancer, including two being tested in multiple ongoing clinical trials, SGN-30 and SGN-15, one expected to enter clinical trials in early 2004, SGN-40, and three in preclinical development, SGN-35, SGN-75 and SGN-17/19. The product candidates encompass three platform technologies: genetically engineered monoclonal antibodies, antibody-drug conjugates (ADCs) and antibody-directed enzyme prodrug therapy (ADEPT). Seattle Genetics has developed leading ADC technology comprised of highly potent drugs and stable linkers for attaching the drugs to monoclonal antibodies. The company currently has license agreements for its ADC technology with Genentech, Celltech Group and Protein Design Labs and for its ADEPT technology with Genencor International. More information about Seattle Genetics can be found at www.seattlegenetics.com.

Certain of the statements made in this press release are forward-looking. Actual results or developments may differ materially from those projected or implied in these forward-looking statements. Specifically, the statements regarding planned clinical trials and the potential therapeutic benefit of SGN-30 are forward-looking and actual results may differ materially from these statements for various reasons. Factors that may cause such a difference include difficulties in implementing the combined technologies of Seattle Genetics and its partners, 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 to secure collaborators or failure of those collaborators to perform their contractual obligations. 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.