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Investor Relations                                                      Media Relations
- -------------------                                                     ---------------
John Calhoun, MD, MBA                                                   Susan W. Specht, MBA
Director, Corporate Communications & Investor Relations                 Associate Director, Corporate Communications
(206) 442-6744                                                          (206) 442-6592


FOR IMMEDIATE RELEASE

     ZymoGenetics Establishes Global Collaboration with Bayer HealthCare for
        Development and Commercialization of Recombinant Human Thrombin

          - ZymoGenetics to receive up to $198 million plus royalties,
                     including up to $70 million in 2007 -

  - Bayer HealthCare acquires product rights in all markets outside the U.S. -

 - Bayer HealthCare to support rThrombin sales efforts in U.S. for three years -

            - ZymoGenetics to host conference call Tuesday, June 19
                          at 8:30 a.m. Eastern Time -

Seattle, June 19, 2007 -- ZymoGenetics, Inc. (NASDAQ: ZGEN) announced today it
has entered into multi-year, domestic and global license and collaboration
agreements with Bayer HealthCare (NYSE: BAY) to maximize the potential of
ZymoGenetics' most advanced product candidate, recombinant human thrombin
(rThrombin). ZymoGenetics retains U.S. product rights. As part of a co-promotion
agreement, Bayer HealthCare will contribute its sales and marketing expertise
for the first three years following product launch, with the expectation that
the two firms will maximize penetration of the product into the U.S. market.

Bayer HealthCare will commercialize rThrombin in all countries outside the
United States, leveraging the company's strong commercial presence in these
markets. Bayer HealthCare will be responsible for any required clinical trials
and securing regulatory approvals and commercializing the product in all
countries outside the United States.

"We're delighted to have Bayer HealthCare as our partner for launching and
commercializing rThrombin," stated Bruce L.A. Carter, Ph.D., President and Chief
Executive Officer of ZymoGenetics. "With their history of successfully marketing
blood clotting factors and hospital-based products, Bayer HealthCare has the
capability and commitment to build the long-term value of rThrombin in Europe
and other rapidly growing health care markets around the world. By combining our
sales force with Bayer HealthCare's experienced sales force in the U.S., we hope
to accelerate the switch to rThrombin."


In 2007, ZymoGenetics expects to receive $70 million from Bayer HealthCare,
including a $30 million upfront payment and a $40 million milestone payment due
upon approval of rThrombin in the U.S. ZymoGenetics is eligible to receive up to
$128 million in additional development and sales-based milestones over the
course of the agreement.

"rThrombin has strong clinical data and considerable near-term revenue potential
for our hematology and surgical hemostasis business," said Arthur Higgins,
chairman of the Executive Committee for Bayer HealthCare LLC. "This product is
an attractive addition to our growing specialty pharmaceutical portfolio. Our
partnership with ZymoGenetics demonstrates Bayer's continued focus on working
collaboratively with innovative biotechnology companies to develop and
commercialize novel protein therapeutics."

In the United States, Bayer HealthCare will co-promote rThrombin with
ZymoGenetics for a three-year period beginning at launch. Bayer HealthCare will
leverage its strong surgery-focused field force of sales representatives and
medical science liaisons for the co-promotion effort, aimed toward establishing
a significant U.S. market share as well as expanding the size of the U.S.
thrombin market. ZymoGenetics will compensate Bayer HealthCare for its efforts
in the U.S. by paying a tiered commission of up to 20% on U.S. sales and up to
$20 million in sales bonus payments upon achievement of certain U.S. sales
levels. For two years following the end of the co-promotion period, ZymoGenetics
will pay Bayer HealthCare a sales commission at a reduced rate, subject to an
annual maximum.

For all sales outside the U.S., Bayer HealthCare will pay ZymoGenetics milestone
payments and tiered royalties based on annual sales levels. Bayer HealthCare
will retain rights to market rThrombin outside the United States indefinitely.

About rThrombin
ZymoGenetics is developing rThrombin, a recombinant form of human thrombin that
is not derived from animal or human blood, as an aid to controlling bleeding
during surgery. Thrombin is used in more than 1 million surgeries each year in
the United States. Currently, only thrombin derived from bovine blood is
available in the U.S. as a stand-alone thrombin product. Bovine-derived thrombin
has been associated with the development of antibodies that may cross-react with
human blood proteins and in some cases these antibodies appear to be related to
serious bleeding complications. The production of recombinant proteins is not
dependent on the availability of blood from animals or human donors and can be
scaled-up to meet market demand. ZymoGenetics has received notification of the
acceptance of its Biologics License Application by the FDA, with an anticipated
response (PDUFA) date of October 18, 2007.

Conference Call and Live Webcast Information
ZymoGenetics' senior management will host a conference call and live webcast on
June 19, 2007 at 8:30 a.m. Eastern Time. Interested parties should go to
www.zymogenetics.com (in the Investor Relations-Events section) or dial
877-407-0782 (International: 201-689-8567) approximately 10 minutes prior to the
scheduled start time for registration. The conference call and live webcast will
be archived for 30 days.

For replay, please visit www.zymogenetics.com or use the following information:


      o     U.S. callers: 877-660-6853
      o     International callers: 201-612-7415

Replay passcodes: account #: 286 and conference ID #: 246029

About ZymoGenetics

ZymoGenetics creates novel protein drugs with the potential to significantly
help patients fight their diseases. The Company is developing a diverse pipeline
of potential proprietary product candidates that are moving into and through
clinical development. These candidates span a wide array of clinical
opportunities that include bleeding, autoimmune diseases and cancer.
ZymoGenetics intends to commercialize these product candidates through internal
development, collaborations with partners, and out-licensing of patents from its
extensive patent portfolio. For further information, visit www.zymogenetics.com.

Bayer HealthCare AG

Bayer HealthCare, a subsidiary of Bayer AG, 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, Diabetes Care and Pharmaceuticals divisions. The
pharmaceuticals business operates under the name Bayer Schering Pharma and as
Bayer HealthCare Pharmaceuticals in the US and Canada. Bayer HealthCare's aim is
to discover and manufacture products that will improve human and animal health
worldwide.

This press release contains "forward-looking statements" within the meaning of
the Private Securities Litigation Reform Act of 1995. These forward-looking
statements are based on the current intent and expectations of the management of
ZymoGenetics. These statements are not guarantees of future performance and
involve risks and uncertainties that are difficult to predict. ZymoGenetics'
actual results and the timing and outcome of events may differ materially from
those expressed in or implied by the forward-looking statements because of risks
associated with our unproven discovery strategy, preclinical and clinical
development, regulatory oversight, intellectual property claims and litigation
and other risks detailed in the company's public filings with the Securities and
Exchange Commission, including the company's Annual Report on Form 10-K for the
year ended December 31, 2006. Except as required by law, ZymoGenetics undertakes
no obligation to update any forward-looking or other statements in this press
release, whether as a result of new information, future events or otherwise.