Seattle Genetics and Agensys, an Affiliate of Astellas, Announce Co-Development of an Additional Antibody-Drug Conjugate (ADC)

  Seattle Genetics and Agensys, an Affiliate of Astellas, Announce
  Co-Development of an Additional Antibody-Drug Conjugate (ADC) Under Existing
  Collaboration

Business Wire

BOTHELL, Wash. & SANTA MONICA, Calif. -- June 27, 2013

Seattle Genetics, Inc. (NASDAQ:SGEN) and Agensys, Inc., an affiliate of
Tokyo-based Astellas Pharma Inc. (Tokyo:4503), today announced that Seattle
Genetics has exercised an option to co-develop an additional antibody-drug
conjugate (ADC) under the companies’ existing ADC collaboration agreement. The
ADC, called ASG-15ME, targets the tumor antigen SLITRK6, which is known to be
expressed on bladder and lung cancer. Agensys has submitted an investigational
new drug (IND) application to the U.S. Food and Drug Administration (FDA) for
a phase 1 trial of ASG-15ME.

“Through our collaboration and co-development agreements with companies like
Agensys/Astellas, Seattle Genetics continues to enhance its ability to
innovate by combining our industry-leading ADC technology with proprietary
cancer targets and antibodies to develop potential new treatments for patients
with cancer,” said Eric L. Dobmeier, Chief Operating Officer of Seattle
Genetics. “ADCs represent a novel therapeutic approach, and through our
pipeline and collaborations more than half of the ADC candidates in clinical
development utilize our technology. We look forward to working with
Agensys/Astellas to advance ASG-15ME.”

“We’re eager to continue our strong collaboration with Seattle Genetics for
ASG-15ME,” said David Stover, Ph.D., Senior Vice President, Agensys Site Head.
“This collaboration with Seattle Genetics is in line with our goal to utilize
the most advanced technologies to generate more innovative medicines in
oncology.”

ASG-15ME is an ADC composed of a fully human antibody directed to SLITRK6, an
antigen expressed in multiple solid tumors. Preclinically, ASG-15ME has
demonstrated antitumor activity in models of bladder and lung cancer. The
antibody is attached to a potent, synthetic cytotoxic agent, monomethyl
auristatin E (MMAE), via an enzyme-cleavable linker using Seattle Genetics’
proprietary technology. The ADC is designed to be stable in the bloodstream,
but to release MMAE upon internalization into SLITRK6-expressing tumor cells,
resulting in targeted cell-killing.

Upon the option exercise, Seattle Genetics will make an option exercise
payment and thereafter fund half of the future development costs for the
ASG-15ME program. The impact of the option exercise on Astellas’ current
fiscal year (from April 1, 2013, to March 31, 2014) financial forecast will be
immaterial.

About the Seattle Genetics / Agensys Collaboration

Seattle Genetics and Agensys entered into the ADC collaboration in January
2007, and expanded it in November 2009. Under the collaboration, Agensys has
the right to obtain exclusive ADC licenses for multiple cancer targets. The
companies are co-developing and will globally co-commercialize and share
profits on a 50:50 basis for ASG-5ME, ASG-22ME and ASG-15ME. Any ADC programs
to which Seattle Genetics does not opt-in will be developed and commercialized
exclusively by Agensys, and Seattle Genetics is entitled to progress-dependent
fees, milestone payments and mid-single-digit royalties on worldwide net sales
of such products.

ADCs are monoclonal antibodies that are designed to selectively deliver
cytotoxic agents to tumor cells. With over a decade of experience and
knowledge in ADC innovation, Seattle Genetics has developed proprietary
technology employing synthetic cytotoxic agents and stable linker systems that
attach these cytotoxic agents to the antibody. Seattle Genetics’ linker
systems are designed to be stable in the bloodstream and release the potent
cell-killing agent once inside targeted cancer cells. This approach is
intended to spare non-targeted cells and thus reduce many of the toxic effects
of traditional chemotherapy while enhancing antitumor activity. Agensys
utilizes its portfolio of novel cancer targets to generate high-affinity fully
human, proprietary antibodies, and combines selected antibodies with Seattle
Genetics’ ADC technology to produce new cancer therapies.

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^® (brentuximab vedotin), 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 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 AbbVie, Agensys (an
affiliate of Astellas), Bayer, Celldex, 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 www.seattlegenetics.com.

About Agensys

Agensys, Inc., an affiliate of Astellas Pharma Inc., is developing a pipeline
of therapeutic fully human monoclonal antibodies (MAbs) to treat cancer. The
MAb product pipeline is being generated to Agensys’ diverse portfolio of
proprietary, clinically relevant cancer targets. Agensys’ target portfolio and
related products are protected by a large patent estate. The company has full
capabilities to generate, develop and manufacture antibody products. Agensys
is progressing a pipeline of both naked and antibody-drug conjugated (ADC)
therapeutic antibodies, directed at a variety of cancer indications, including
those of the prostate, kidney, pancreas, ovary, bladder, lung, colon, breast
and skin. ADC products are based on drug platform technologies developed by
Seattle Genetics. Agensys is developing a growing pipeline of clinical-stage
functional MAbs and ADC products.

About Astellas

Astellas Pharma Inc., located in Tokyo, Japan, is a pharmaceutical company
dedicated to improving the health of people around the world through the
provision of innovative and reliable pharmaceuticals. Astellas has
approximately 17,000 employees worldwide. The organization is committed to
becoming a global category leader in Urology, Immunology (including
Transplantation) and Infectious Diseases, Oncology, Neuroscience and DM
Complications and Kidney Diseases. For more information on Astellas Pharma
Inc., please visit the company website at www.astellas.com/en.

For Seattle Genetics, Inc.:

Certain of the statements made in this press release are forward looking, such
as those, among others, relating to the therapeutic potential and future
clinical progress, regulatory approval and commercial launch of products
utilizing Seattle Genetics’ ADC technology. 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 our product candidates or our collaborators’
product candidates move into and advance in clinical trials, risks inherent in
early-stage development and failure by Seattle Genetics to secure or maintain
relationships with collaborators. More information about the risks and
uncertainties faced by Seattle Genetics is contained in the Company’s
quarterly report on Form 10-Q for the quarter ended March 31, 2013, 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.

For Agensys, Inc.

This press release includes forward-looking statements based on assumptions
and beliefs in light of the information currently available to management and
subject to significant risks and uncertainties. Forward-looking statements
include all statements other than statements of historical fact, including
plans, strategies and expectations for the future, statements regarding the
expected timing of filings and approvals relating to the transaction, the
expected timing of the completion of the transaction, the ability to complete
the transaction or to satisfy the various closing conditions, future revenues
and profitability from or growth or any assumptions underlying any of the
foregoing. Statements made in the future tense, and words such as
“anticipate,” “expect,” “project,” “continue,” “believe,” “plan,” “estimate,”
“pro forma,” “intend,” “potential,” “target,” “forecast,” “guidance,”
“outlook,” “seek,” “assume,” “will,” “may,” “should,” and similar expressions
are intended to qualify as forward-looking statements. Forward-looking
statements are based on estimates and assumptions made by management that are
believed to be reasonable, though they are inherently uncertain and difficult
to predict. Investors and security holders are cautioned not to place undue
reliance on these forward-looking statements.

Actual financial results may differ materially depending on a number of
factors, including adverse economic conditions, currency exchange rate
fluctuations, adverse legislative and regulatory developments, delays in new
product launch, pricing and product initiatives of competitors, the inability
of the company to market existing and new products effectively, interruptions
in production, infringements of the company’s intellectual property rights and
the adverse outcome of material litigation. This press release contains
information on pharmaceuticals (including compounds under development), but
this information is not intended to make any representations or advertisements
regarding the efficacy or effectiveness of these pharmaceuticals nor provide
medical advice of any kind.

Contact:

Seattle Genetics, Inc.
Investors:
Peggy Pinkston, 425-527-4160
ppinkston@seagen.com
or
Media:
Tricia Larson, 425-527-4180
tlarson@seagen.com
or
For Agensys, Inc.:
Astellas
Jenny M. Kite, 847-682-4530 (cell)
Jenny.Kite@Astellas.com
 
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