Seattle Genetics Receives FDA Fast Track Designation for SGN-35 for the Treatment of Hodgkin Lymphoma

BOTHELL, Wash.--(Business Wire)--
Seattle Genetics, Inc. (Nasdaq:SGEN) today announced that the U.S. Food and Drug
Administration (FDA) has granted fast track designation to SGN-35 for the
treatment of Hodgkin lymphoma. SGN-35, an antibody-drug conjugate (ADC), is in
an ongoing pivotal trial under a Special Protocol Assessment (SPA) from the FDA
for relapsed or refractory Hodgkin lymphoma.

"Receiving fast track designation is another important component of our
regulatory strategy for SGN-35, and a key step for this program," said Clay B.
Siegall, Ph.D., President and Chief Executive Officer of Seattle Genetics. "With
our pivotal trial underway, we expect data in 2011. Our goal remains to submit a
new drug application (NDA) in 2011 with potential commercial launch in 2012."

The fast track program is designed to facilitate the development and expedite
the review of new drugs that are intended to treat serious or life-threatening
conditions and that demonstrate the potential to address unmet medical needs.
Fast track designated drugs ordinarily qualify for priority review, thereby
expediting the FDA review process. In addition, the designation allows the
SGN-35 NDA to be considered for submission on a rolling basis, allowing the FDA
to review sections of the NDA as they are completed.

In February 2009, Seattle Genetics initiated a pivotal trial of SGN-35. The
study is evaluating efficacy and safety of single-agent SGN-35 in 100 patients
with relapsed or refractory Hodgkin lymphoma. The primary endpoint of the trial
is objective response rate assessed by an independent radiographic 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 United States, Canada and Europe. In January 2009, the
company received an SPA for the pivotal trial, which is an agreement with the
FDA regarding the trial design necessary to support an efficacy claim in an NDA.
SGN-35 has received orphan drug designation in the United States and Europe for
both Hodgkin lymphoma and anaplastic large cell lymphoma (ALCL).

Seattle Genetics plans to initiate a phase II study of single-agent SGN-35 in
approximately 55 patients with relapsed or refractory systemic ALCL. In
addition, the company plans to report data from an ongoing weekly dosing phase I
clinical trial of SGN-35 during an oral presentation at the American Society of
Clinical Oncology annual meeting to be held May 29 to June 2, 2009.

About SGN-35

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 a targeted cell-killing effect.

About Hodgkin 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. Based on market research, Seattle Genetics
believes that there are several thousand newly relapsed or refractory lymphoma
patients in the United States each year who would be potentially eligible for
treatment with SGN-35, and that the U.S. prevalence population of these patients
is approximately 10,000 individuals.

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.
Seattle Genetics has collaborations for its ADC technology with a number of
leading biotechnology and pharmaceutical companies, including Genentech, Bayer,
CuraGen, Progenics, Daiichi Sankyo and MedImmune, a subsidiary of AstraZeneca,
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, timelines and market potential 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 ALCL,
whether caused by competition, adverse events, patient enrollment rates,
regulatory issues or other factors; that the clinical trials, including the
pivotal clinical trial for relapsed or refractory Hodgkin lymphoma, may not
demonstrate that SGN-35 is both safe and effective; 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 and 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 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.

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

Copyright Business Wire 2009