Seattle Genetics Enters Into New Antibody-Drug Conjugate Collaboration with Bayer

  Seattle Genetics Enters Into New Antibody-Drug Conjugate Collaboration with

  Seattle Genetics eligible to potentially receive more than $500 million in
          fees and milestones plus royalties under multi-target deal

Business Wire

BOTHELL, Wash. -- June 25, 2013

Seattle Genetics, Inc. (NASDAQ:SGEN) today announced that it has entered into
a new antibody-drug conjugate (ADC) collaboration with Bayer HealthCare
(Bayer). Under the latest relationship, Bayer will pay upfront and option
exercise fees of up to $20 million for worldwide rights to utilize Seattle
Genetics’ auristatin-based ADC technology with antibodies to several oncology
targets. Seattle Genetics is also eligible to receive up to approximately $500
million in potential milestone payments, as well as royalties on worldwide net
sales of any resulting products under the multi-target collaboration. Bayer is
responsible for research, product development, manufacturing and
commercialization of all products under the collaboration.

“The significant clinical and preclinical progress across our ADC
collaborations, and enthusiasm for our technology as demonstrated by this
latest relationship with Bayer, continue to reinforce Seattle Genetics’
leadership position in the field,” said Natasha Hernday, Vice President,
Corporate Development, at Seattle Genetics. “Across internal and collaborator
programs, there are more than 15 ADCs in clinical development using our
technology, and we have the potential to receive more than $3.5 billion in
future milestones plus royalties from these strategic alliances.”

“Bayer is committed to translating the science of cancers into effective
therapies that can help people with cancer live longer and improve their
quality of life,” said Prof. Andreas Busch, Member of the Bayer HealthCare
Executive Committee and Head of Global Drug Discovery. “Antibody-drug
conjugates are promising approaches in oncology which can attack tumor cells
in a much more targeted way for cancer patients, such that healthy cells are
less severely affected. Antibody-drug conjugates are one of our focus areas in
oncology research and we are looking forward to strengthening our portfolio in
this area of personalized medicine through the collaboration with Seattle

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.

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

About Bayer HealthCare

The Bayer Group is a global enterprise with core competencies in the fields of
health care, agriculture and high-tech materials. Bayer HealthCare, a subgroup
of Bayer AG with annual sales of EUR 18.6 billion (2012), is one of the
world’s leading, innovative companies in the healthcare and medical products
industry and is based in Leverkusen, Germany. The company combines the global
activities of the Animal Health, Consumer Care, Medical Care and
Pharmaceuticals divisions. Bayer HealthCare’s aim is to discover, develop,
manufacture and market products that will improve human and animal health
worldwide. Bayer HealthCare has a global workforce of 55,300 employees (Dec
31, 2012) and is represented in more than 100 countries. More information at

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.


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