ZymoGenetics And Serono Begin Phase 2 Clinical Trial With Atacicept In Rheumatoid Arthritis

ZymoGenetics,
Inc. (Nasdaq: ZGEN) and Serono (NYSE: SRA; virt-x: SEO) today announced the
start of a Phase 2 clinical trial in which atacicept therapy will be
evaluated in patients with rheumatoid arthritis (RA). The randomized,
double-blind, multi-center study will investigate the efficacy of atacicept
in patients with an inadequate response to prior treatment with TNF
inhibitors. The efficacy of atacicept will be evaluated according to the
American College of Rheumatology (ACR) criteria for defining clinical
improvement in RA patients.



"Data from our Phase 1b RA study indicate that atacicept has potential
as a treatment for rheumatoid arthritis," said Bruce L. A. Carter, Ph.D.,
President and Chief Executive Officer of ZymoGenetics. "A clear patient
need still exists for new therapies. The Phase 2 study should provide a
clear signal as to the efficacy of atacicept and this will enable us to
make an informed decision about targeting the RA market with atacicept."



"This Phase 2 study is part of a broad Phase 2 clinical trial program
in rheumatoid arthritis. It also marks an important step toward bringing
innovative treatments to patients whose medical needs are unmet by current
therapies," said Franck Latrille, Senior Executive Vice President,
Corporate Global Product Development at Serono.



The study will enroll 320 patients who have had active RA for more than
one year and who have had an inadequate response to at least 3 months of
TNF inhibitor therapy. Patients will be randomized into groups receiving
one of three dose levels (25 mg, 75 mg or 150 mg) of atacicept or placebo,
in addition to background methotrexate therapy, and they will be treated
for twenty-five weeks. Loading doses will be given twice weekly for 4
weeks, followed by 21 weekly maintenance doses. A follow-up visit will
occur 13 weeks after the last dose.



The primary endpoint will be the rate of ACR 20 response(1) at week 26.
Secondary objectives include further characterizing the efficacy, safety,
tolerability and pharmacologic profile of atacicept at each of these dose
levels. ACR 50 and 70 responses and DAS 28(2) will be used as secondary
measures of efficacy.



ZymoGenetics and Serono are also in dialogue with the FDA regarding the
systemic lupus erythematosus (SLE) Phase 2 clinical development program.
The companies are planning to initiate the trial in SLE in mid-2007.



Earlier this year, the companies completed Phase 1b studies with
atacicept in SLE and rheumatoid arthritis.



About Atacicept



ZymoGenetics and Serono are developing atacicept (formerly referred to
as TACI-Ig) for the treatment of autoimmune diseases and B-cell
malignancies. Atacicept contains the soluble TACI receptor that binds to
the cytokines BLyS and APRIL. These cytokines, in turn, are members of the
tumor necrosis factor (TNF) family that promote B-cell survival and
autoantibody production associated with certain autoimmune diseases such as
systemic lupus erythematosus (SLE). Current data indicates that levels of
BLyS and APRIL are elevated in patients with rheumatoid arthritis, SLE and
B-cell malignancies. Atacicept has been shown to affect several stages of
B-cell development and may inhibit the survival of cells responsible for
making antibodies.
















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Forward-looking Statements



For ZymoGenetics



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, 2005. 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.



For Serono



Some of the statements in this press release are forward looking. Such
statements are inherently subject to known and unknown risks, uncertainties
and other factors that may cause actual results, performance or
achievements of Serono S.A. and affiliates to be materially different from
those expected or anticipated in the forward-looking statements.
Forward-looking statements are based on Serono's current expectations and
assumptions, which may be affected by a number of factors, including those
discussed in this press release and more fully described in Serono's Annual
Report on Form 20-F filed with the U.S. Securities and Exchange Commission
on February 28, 2006. These factors include any failure or delay in
Serono's ability to develop new products, any failure to receive
anticipated regulatory approvals, any problems in commercializing current
products as a result of competition or other factors, our ability to obtain
reimbursement coverage for our products, the outcome of government
investigations and litigation and government regulations limiting our
ability to sell our products. Serono has no responsibility to update the
forward-looking statements contained in this press release to reflect
events or circumstances occurring after the date of this press release.



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 zymogenetics.



About Serono



Serono is a global biotechnology leader. The Company has eight
biotechnology products, Rebif(R), Gonal-f(R), Luveris(R),
Ovidrel(R)/Ovitrelle(R), Serostim(R), Saizen(R), Zorbtive(TM) and
Raptiva(R). In addition to being the world leader in reproductive health,
Serono has strong market positions in neurology, metabolism and growth and
has recently entered the psoriasis area. The Company's research programs
are focused on growing these businesses and on establishing new therapeutic
areas, including oncology and autoimmune diseases.



In 2005, Serono, whose products are sold in over 90 countries, achieved
worldwide revenues of US $2.6 billion. Reported net loss in 2005 was
US$106.1 million, reflecting a charge of US$725 million taken relating to
the settlement of the US Attorney's Office investigation of Serostim.
Excluding this charge as well as other non-recurring items, adjusted net
income grew 28.4% to US$565.3 million in 2005. Bearer shares of Serono
S.A., the holding company, are traded on the virt-x (SEO) and its American
Depositary Shares are traded on the New York Stock Exchange (SRA).


ZymoGenetics, Inc.

zymogenetics