New Biomarker Data Links KRAS Gene to Vectibix(TM) Clinical Response

Biomarker Analysis from Randomized, Controlled Trial Represents an Advance in the Science of Anti-EGFR Therapy in Metastatic Colorectal Cancer

Amgen (NASDAQ: AMGN) today announced the results of a biomarker
analysis that supports KRAS as a predictive clinical biomarker that
could be used to select patients who are more likely to respond to
treatment with Vectibix(TM) (panitumumab) monotherapy.

These data were generated from an analysis of the Phase 3,
randomized, controlled clinical trial that investigated the treatment
effect of Vectibix in patients with metastatic colorectal cancer
(mCRC). Previously reported results from this study demonstrated that
Vectibix monotherapy improved progression-free survival ((PFS), HR
0.54; p less than 0.001)) and response rate (10 percent versus 0
percent) in heavily pre-treated patients with mCRC after failure of
standard chemotherapy. The new biomarker analysis met its primary and
secondary endpoints by demonstrating that the effect of Vectibix on
PFS was confined exclusively to the approximately 60 percent of
patients whose tumors harbor normal, non-mutated (wild-type) KRAS. No
effect of Vectibix therapy was observed in patients who had tumors
with mutations in KRAS regardless of the endpoint studied. These data
have been shared with U.S. and global regulatory agencies and have
been submitted for peer-reviewed publication.

Additionally, pooled data from three Phase 2 trials and a Phase 3
extension study provide supportive evidence regarding the predictive
value of KRAS in Vectibix monotherapy. Results were presented during
the Presidential Session at the 14th European Cancer Conference (ECCO)
in Barcelona, Spain.

Twenty years of study indicate that KRAS plays an important role
in cell growth regulation and oncogenesis. In mCRC, the epidermal
growth factor receptor (EGFR) transmits signals through a set of
intracellular proteins. Upon reaching the nucleus, these signals
instruct the cancer cell to reproduce and metastasize, leading to
cancer progression. Anti-EGFR therapies work by blocking the
activation of EGFR, thereby inhibiting downstream events that lead to
malignant signaling. However, it is hypothesized that in patients with
tumors harboring a mutated KRAS gene, the KRAS protein is always
turned "on," regardless of whether the EGFR has been activated or
therapeutically inhibited.

Thus, in patients with mutant KRAS, signaling continues despite
anti-EGFR therapy. Activated KRAS is detected in approximately 40
percent of metastatic colorectal cancer, depending on the testing
method used. Multiple studies support anti-EGFR therapy being
significantly more effective in patients with non-mutated KRAS.

"Preclinical research has long implicated the RAS oncogene in
cancer biology, but now this research may be translated into patient
management," said Roger M. Perlmutter, M.D., Ph.D., executive vice
president of Research and Development at Amgen. "In the future,
physicians may select treatment options specifically for patients
whose tumors harbor the non-mutated KRAS gene."

In a second analysis, patient samples from four mCRC monotherapy
studies of safety and efficacy with Vectibix were used to generate the
hypothesis that tumors with mutated KRAS are associated with drug
resistance. Of the 62 patient samples evaluated in the analysis, 21
had the activated KRAS and none responded to therapy. The analysis
also found that there was a statistically significant association
between KRAS mutation status and response to Vectibix (p=0.013).

"Being able to select which patients may benefit from treatment
would reduce the individual patient and societal burdens often
associated with cancer therapy," said Tim Turnham, Ph.D., chief
executive officer, Colon Cancer Alliance. "The robustness and outcome
of this biomarker analysis is an important step forward in advancing
the field of personalized cancer care."

Last week the European Committee for Medicinal Products for Human
Use (CHMP) issued a positive opinion recommending a conditional
marketing authorization for Vectibix(TM) (panitumumab) in the European
Union (EU) for patients with refractory metastatic colorectal cancer
with non-mutated (wild-type) KRAS genes.

About Vectibix

Vectibix is indicated in the U.S. for the treatment of patients
with epidermal growth factor receptor- (EGFR) expressing mCRC after
disease progression on or following fluoropyrimidine-, oxaliplatin-,
and irinotecan- containing chemotherapy regimens. The effectiveness of
Vectibix for the treatment of EGFR-expressing, metastatic colorectal
carcinoma is based on progression-free survival. Currently no data are
available that demonstrate an improvement in disease-related symptoms
or increased survival with Vectibix.

Important Product Safety Information

Dermatologic toxicities, related to Vectibix blockade of EGF
binding and subsequent inhibition of EGF receptor-mediated signaling
pathways, included but were not limited to dermatitis acneiform,
pruritus, erythema, rash, skin exfoliation, paronychia, dry skin, and
skin fissures. Dermatologic toxicities were reported in 89 percent of
patients treated with Vectibix and were severe in 12 percent of
patients. Severe dermatologic toxicities were complicated by
infection, including sepsis, septic death, and abscesses requiring
incisions and drainage. Vectibix may need to be withheld or
discontinued for severe dermatologic toxicities.

Severe infusion reactions occurred with Vectibix in approximately
1 percent of patients. Severe infusion reactions were identified as
anaphylactic reactions, bronchospasm, fever, chills, and hypotension.
Although fatal infusion reactions have not been reported with
Vectibix, they have occurred with other monoclonal antibody products.
Severe infusion reactions require stopping the infusion and possibly
permanently discontinuing Vectibix, depending on the severity and/or
persistence of the reaction.

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 deep and broad 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 www.amgen.com.

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