Seattle Genetics Reports on SGN-30 Cutaneous ALCL Phase II Clinical Trial at the Society of Investigative Dermatology Meeting.

BOTHELL, Wash. -- Seattle Genetics, Inc. (Nasdaq:SGEN) today reported data from its ongoing phase II clinical trial of SGN-30 in cutaneous anaplastic large cell lymphoma (ALCL) and other lymphoproliferative disorders at the Society of Investigative Dermatology annual meeting being held in Philadelphia May 3-6. Multiple patients achieved objective antitumor responses to SGN-30 therapy, including both complete and partial responses. The study includes patients with relapsed or refractory CD30-expressing cutaneous T-cell disease, including cutaneous ALCL, transformed mycosis fungoides and lymphomatoid papulosis.

"We are encouraged by our data in this relapsed and refractory patient population, especially the high response rate with SGN-30 and the significant durations of response observed in several patients," said Clay B. Siegall, Ph.D., President and Chief Executive Officer at Seattle Genetics. "SGN-30 may provide an important therapeutic option for advanced cutaneous T-cell malignancies, which are often painful, disfiguring and can greatly impact patients' quality of life."

SGN-30 (anti-CD30 mAb) is Active and Well Tolerated in Patients with Cutaneous Anaplastic Large Cell Lymphoma, Large Cell Transformation of Mycosis Fungoides and Lymphomatoid Papulosis (Abstract #268)

In this phase II study, which is designed to assess antitumor activity, tolerability and pharmacokinetics of a multi-dose regimen of SGN-30, patients receive six doses of 12 milligrams per kilogram of SGN-30 every two to three weeks. Patients may continue on study for up to three courses of therapy (total of 18 doses). Eleven patients have been enrolled in the study to date with a median age of 69 years and a median of two prior therapies. Six patients achieved objective antitumor responses, including one ongoing complete response lasting more than ten months and five partial responses. Three patients have stable disease and two had progressive disease. All three patients with stable disease and one of the patients with a partial response are still receiving their first course of SGN-30 therapy. Multiple doses of SGN-30 have been well tolerated. Drug-related adverse events have been typically mild and consistent with antibody administration. Accrual to the study is ongoing.

About SGN-30

SGN-30 is a monoclonal antibody that targets the CD30 antigen, which is expressed on hematologic malignancies including Hodgkin's disease and some T-cell non-Hodgkin's lymphomas. Seattle Genetics is conducting ongoing phase II clinical trials of SGN-30 as a single agent in systemic ALCL and cutaneous ALCL. In addition, the company is collaborating with the National Cancer Institute (NCI) on two phase II clinical trials that will combine SGN-30 and chemotherapy regimens, one for the front-line treatment of systemic ALCL and the other for the treatment of Hodgkin's disease.

About Seattle Genetics

Seattle Genetics is a biotechnology company focused on the development of monoclonal antibody-based therapies for the treatment of cancer and immunologic diseases. The company is conducting multiple clinical trials of its three lead product candidates, SGN-30, SGN-40 and SGN-33, and preclinical development of several late-stage programs, including SGN-35. In addition, Seattle Genetics has developed proprietary antibody-drug conjugate (ADC) technology comprised of highly potent synthetic drugs and stable linkers for attaching the drugs to monoclonal antibodies. The company currently has license agreements for its ADC technology with a number of leading biotechnology and pharmaceutical companies, including Genentech, Bayer, CuraGen and MedImmune. More information about Seattle Genetics' pipeline and technologies 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 future advancement and therapeutic potential of SGN-30. 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 SGN-30 advances in clinical trials, such as patients exhibiting progressive disease or severe adverse events. 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.