THOUSAND OAKS, Calif. and FREMONT, Calif., Aug. 1 /PRNewswire-FirstCall/
-- Amgen (Nasdaq: AMGN) and Abgenix, Inc. (Nasdaq: ABGX) today announced that
the U.S. Food and Drug Administration (FDA) has granted fast track designation
for panitumumab, an experimental fully human monoclonal antibody directed
against the epidermal growth factor receptor (EGFr), for patients with
metastatic colorectal cancer who have failed standard chemotherapy treatment.
    "We are advancing the development of panitumumab with the hope of offering
patients a new treatment option in their fight against metastatic colorectal
cancer," said Willard Dere, M.D., chief medical officer and senior vice
president of global development at Amgen.
    Under the FDA Modernization Act of 1997, fast track designation allows the
FDA to accept, on a rolling basis, portions of a marketing application for
review prior to the completion of the final registrational package.  Fast
track designation may potentially expedite the review of a drug that is
intended for the treatment of a serious life- threatening condition and
demonstrates the potential to address an unmet medical need for such a
condition.
    In light of this fast track designation, Amgen and Abgenix are working
toward initiating the submission of the Biologics License Application (BLA)
for panitumumab in patients who have failed prior standard chemotherapy,
including irinotecan and oxaliplatin, by the end of 2005.  The completed
submission of the BLA could extend into the first quarter of 2006, depending
on timing and outcome of clinical data.  FDA has previously indicated that
data from one pivotal trial, once completed, could be acceptable with
additional data from other pending studies to support a submission for
marketing approval in the United States.
    "Panitumumab is the first fully human monoclonal antibody to inhibit EGFr,
and fast track designation represents an important milestone in its
development," said Bill Ringo, chief executive officer at Abgenix. "We are one
step closer to bringing this promising new treatment to patients with advanced
colorectal cancer."
    Patients and physicians can access http://www.amgentrials.com for more
information about ongoing panitumumab clinical trials.

    About Panitumumab
    Co-developed by Amgen and Abgenix, panitumumab is an investigational
product in a novel class of targeted cancer treatments called epidermal growth
factor receptor (EGFr) inhibitors.  Panitumumab (formerly ABX-EGF) is the
first fully human monoclonal antibody directed against EGFr and is being
evaluated as both a monotherapy and in combination with other agents for the
treatment of various types of cancer, including colorectal, lung and kidney.
Panitumumab was generated with Abgenix's XenoMouse(R)(1) technology, which
creates a fully human monoclonal antibody that contains no murine (mouse)
protein.  The fully human nature of panitumumab may result in a safety profile
with a low incidence of infusion reactions, antigenicity and allergic
response.  These are attributes currently being investigated in clinical
trials.  Pivotal clinical studies evaluating panitumumab as a third-line
monotherapy in colorectal cancer patients are ongoing with an every-other-week
dosing regimen.

    About the Epidermal Growth Factor Receptor (EGFr)
    Although EGFr normally helps regulate the growth of many different cells
in the body, EGFr can also stimulate cancer cells to grow.  In fact, many
cancer cells actually require signals mediated by EGFr for their survival.
Residing on the surface of these tumor cells, EGFr is activated when naturally
occurring proteins in the body, epidermal growth factor (EGF) or transforming
growth factor alpha (TGFa), bind to it.  This binding changes the shape of
EGFr, which, in turn, triggers internal cellular signals that stimulate tumor
cell growth.
    Panitumumab binds to EGFr, preventing EGF and TGFa from binding to the
receptor and interfering with the signals that would otherwise stimulate
growth of the cancer cell and allow it to survive.

    About Amgen
    Amgen discovers, develops and delivers innovative human therapeutics.  A
biotechnology pioneer since 1980, Amgen was one of the first companies to
realize the new science's promise by bringing safe and effective medicines
from lab, to manufacturing plant, to patient. Amgen therapeutics have changed
the practice of medicine, helping millions of people around the world in the
fight against cancer, kidney disease, rheumatoid arthritis, and other serious
illnesses.  With a broad and deep pipeline of potential new medicines, Amgen
remains committed to advancing science to dramatically improve people's lives.
To learn more about our pioneering science and our vital medicines, visit
http://www.amgen.com.

    About Abgenix
    Abgenix is a biopharmaceutical company focused on the discovery,
development and manufacturing of human therapeutic antibodies.  The company's
antibody development platform includes a leading technology and state-of-the-
art manufacturing capabilities that enable the rapid generation, selection and
production of high affinity, fully human antibody product candidates to a
variety of disease targets.  Abgenix leverages its leadership position in
human antibody technology to build a diversified product portfolio through its
own development efforts and the establishment of collaborations with multiple
pharmaceutical and biotechnology companies.  For more information on Abgenix,
visit the company's website at http://www.abgenix.com.

    Amgen Forward-Looking Statement
    This news release contains forward-looking statements that involve
significant risks and uncertainties, including those discussed below and
others that can be found in Amgen's Form 10-K for the year ended December 31,
2004, and in Amgen's periodic reports on Form 10-Q and Form 8-K.  Amgen is
providing this information as of the date of this news release and does not
undertake any obligation to update any forward-looking statements contained in
this document as a result of new information, future events or otherwise.
    No forward-looking statement can be guaranteed and actual results may
differ materially from those we project.  Discovery or identification of new
product candidates or development of new indications for existing products
cannot be guaranteed and movement from concept to product is uncertain;
consequently, there can be no guarantee that any particular product candidate
or development of a new indication for an existing product will be successful
and become a commercial product.  Further, preclinical results do not
guarantee safe and effective performance of product candidates in humans.  The
complexity of the human body cannot be perfectly, or sometimes, even
adequately modeled by computer or cell culture systems or animal models.  The
length of time that it takes for us to complete clinical trials and obtain
regulatory approval for product marketing has in the past varied and we expect
similar variability in the future.  We develop product candidates internally
and through licensing collaborations, partnerships and joint ventures.
Product candidates that are derived from relationships may be subject to
disputes between the parties or may prove to be not as effective or as safe as
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or others could identify side effects or manufacturing problems with our
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