Seattle Genetics Initiates Phase II Trial of SGN-35 for Anaplastic Large Cell Lymphoma

Seattle Genetics Initiates Phase II Trial of SGN-35 for Anaplastic Large Cell Lymphoma

BOTHELL, Wash. -- Jun. 18, 2009-- Seattle Genetics, Inc. (NASDAQ:SGEN), today announced that it has initiated a phase II clinical trial of SGN-35 for patients with relapsed or refractory systemic anaplastic large cell lymphoma (ALCL). SGN-35 is an antibody-drug conjugate (ADC) that utilizes Seattle Genetics' proprietary technology to empower antibodies by linking them to potent cell-killing drugs.

"We have observed promising activity in ALCL patients in our phase I trials, notably six out of seven patients treated with SGN-35 have achieved a complete response," said Clay B. Siegall, Ph.D., President and Chief Executive Officer of Seattle Genetics. "SGN-35 could become an important therapeutic option for patients who relapse or fail to respond to the standard front-line chemotherapy regimen, and we believe that systemic ALCL may offer an additional registration pathway for SGN-35."

The single-arm phase II trial will assess efficacy and safety of single-agent SGN-35 in 55 patients with relapsed or refractory systemic ALCL. Patients will receive 1.8 milligrams per kilogram of SGN-35 every three weeks. The primary endpoint of the trial will be objective response rate determined by an independent review facility. Secondary endpoints include duration of response, progression-free survival, overall survival and tolerability. The company plans to enroll patients at more than 30 sites in the U.S., Canada and Europe.

Seattle Genetics is also conducting a pivotal trial of SGN-35 for Hodgkin lymphoma under a Special Protocol Assessment (SPA) with the U.S. Food and Drug Administration (FDA). Data from two phase I trials of SGN-35 were reported in June at the American Society of Clinical Oncology annual meeting and the 14th Congress of the European Hematology Association. In both phase I trials, relapsed or refractory Hodgkin lymphoma and systemic ALCL patients treated with single-agent SGN-35 achieved multiple objective responses at generally well-tolerated doses. The majority of adverse events were Grade 1 and 2, with the most common being fatigue, fever, peripheral neuropathy, diarrhea and nausea.

SGN-35 is an 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 Systemic Anaplastic Large Cell Lymphoma (ALCL)

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. Systemic ALCL is a type of T-cell non-Hodgkin lymphoma that expresses the CD30 antigen. Although standard front-line combination chemotherapy regimens used to treat systemic ALCL often result in long-term remissions and cures, there are limited therapeutic options and a strong unmet medical need for patients with relapsed or refractory disease. SGN-35 has received orphan drug designation for ALCL from both the FDA and the European Medicines Agency.

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 timelines of SGN-35 in systemic ALCL. 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 completion of the clinical trial of SGN-35 in systemic ALCL, 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; that fast track designation or priority review may not result in earlier approval; 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.