Seattle Genetics Initiates Two Phase I Trials of SGN-CD19A

  Seattle Genetics Initiates Two Phase I Trials of SGN-CD19A

  - Clinical Trials Evaluating Novel ADC in Acute Lymphoblastic Leukemia and
                            Non-Hodgkin Lymphoma -

   - Represents Seattle Genetics’ Fifth Proprietary ADC Program in Ongoing
                              Clinical Trials -

Business Wire

BOTHELL, Wash. -- February 6, 2013

Seattle Genetics, Inc. (Nasdaq: SGEN) today announced the initiation of two
phase I clinical trials of SGN-CD19A, one for patients with B-cell acute
lymphoblastic leukemia (ALL) and one for patients with B-cell non-Hodgkin
lymphomas. SGN-CD19A utilizes Seattle Genetics’ industry-leading antibody-drug
conjugate (ADC) technology. The trials are designed to assess the safety and
antitumor activity of SGN-CD19A, an ADC targeted to CD19.

“CD19 is expressed in a variety of hematologic malignancies, including
non-Hodgkin lymphoma and ALL, and has limited expression on normal tissues
making it an ideal ADC target. Our preclinical data indicate that SGN-CD19A
internalizes rapidly into tumor cells, resulting in targeted cell killing,”
said Jonathan Drachman, M.D., Senior Vice President, Research and
Translational Medicine at Seattle Genetics. “Our SGN-CD19A clinical
development program comprises two trials that, together, will provide a robust
understanding of the activity and tolerability of this ADC in patients with
aggressive CD19-positive lymphomas or ALL. In addition to the five ADCs
already in ongoing clinical trials, we plan to advance two additional ADC
programs into the clinic during 2013, underscoring our leadership in the

The studies are phase I, open-label, dose-escalation clinical trials. The
primary endpoints are to estimate the maximum tolerated dose and to evaluate
the safety of SGN-CD19A. In addition, the trials will evaluate antitumor
activity, pharmacokinetics, progression-free survival and overall survival.
One trial will enroll adult and pediatric patients with relapsed or refractory
B-cell ALL, as well as patients with Burkitt lymphoma or leukemia or B-cell
lymphoblastic lymphoma. The dose escalation portion of the study is designed
to evaluate both weekly and every three week schedules and will enroll
approximately 80 patients at multiple centers in the United States. A second
trial will enroll patients with relapsed or refractory aggressive B-cell
non-Hodgkin lymphomas, including diffuse large B-cell lymphoma (DLBCL) and
mantle cell lymphoma. The dose escalation portion of the trial will evaluate
SGN-CD19A administered every three weeks and will enroll approximately 25
patients at multiple centers in the United States.

Both trials permit additional patients to be enrolled into expansion cohorts
following determination of the maximum tolerated dose.

For more information about the trials, including enrolling centers, please

About SGN-CD19A

SGN-CD19A is an ADC composed of an anti-CD19 antibody attached to a synthetic
cytotoxic cell-killing agent, monomethyl auristatin F (MMAF), using Seattle
Genetics’ proprietary technology. The ADC is designed to be stable in the
bloodstream, and to release its cytotoxic agent upon internalization into
CD19-expressing cells. This approach is intended to spare non-targeted cells
and thus reduce many of the toxic effects of traditional chemotherapy while
enhancing the antitumor activity.

About Acute Lymphoblastic Leukemia

Acute lymphoblastic leukemia, also called acute lymphocytic leukemia or ALL,
is an aggressive type of cancer of the bone marrow and blood that progresses
rapidly without treatment. In ALL, lymphoblasts, which are malignant, immature
white blood cells, multiply and crowd out normal cells in the bone marrow. ALL
is the most common type of cancer in children. According to the American
Cancer Society, approximately 6,000 people were to be diagnosed with ALL
during 2012 and more than 1,400 would die from the disease.

About Non-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. Non-Hodgkin lymphoma is further categorized into
indolent (low-grade) or aggressive, including DLBCL. DLBCL is the most common
type of non-Hodgkin lymphoma. According to the American Cancer Society, more
than 70,000 cases of non-Hodgkin lymphoma were to be diagnosed in the United
States during 2012 and nearly 19,000 people would die from the disease.

About Seattle Genetics

Seattle Genetics is a biotechnology company focused on the development and
commercialization of monoclonal antibody-based therapies for the treatment of
cancer. The company’s lead program, ADCETRIS, received accelerated approval
from the U.S. Food and Drug Administration in August 2011 and approval with
conditions from Health Canada in February 2013 for two indications. In
addition, under a collaboration with Millennium: The Takeda Oncology Company,
ADCETRIS received conditional approval from the European Commission in October
2012. Seattle Genetics also has four other clinical-stage antibody-drug
conjugate (ADC) programs: SGN-75, ASG-5ME, ASG-22ME and SGN-CD19A. Seattle
Genetics has collaborations for its ADC technology with a number of leading
biotechnology and pharmaceutical companies, including Abbott, Agensys (an
affiliate of Astellas), Bayer, Celldex Therapeutics, Daiichi Sankyo,
Genentech, GlaxoSmithKline, Millennium, Pfizer and Progenics, as well as ADC
co-development agreements with Agensys and Genmab. More information can be
found at

Certain of the statements made in this press release are forward-looking, such
as those, among others, relating to the therapeutic potential of SGN-CD19A.
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 the inability to show sufficient activity in these recently
initiated clinical trials and the risk of adverse events as SGN-CD19A advances
in clinical trials. More information about the risks and uncertainties faced
by Seattle Genetics is contained in the company’s 10-Q for the quarter ended
September 30, 2012 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.


Seattle Genetics, Inc.
Peggy Pinkston, 425-527-4160
Tricia Larson, 425-527-4180
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