Randomized Phase 3 Trial Shows Panitumumab Significantly Improved Progression-Free Survival and Disease Control in Metastatic Colorectal Cancer Patients
THOUSAND OAKS, Calif.--(BUSINESS WIRE)--April 3, 2006--Amgen
(Nasdaq:AMGN), the world's largest biotechnology company, today
announced pivotal Phase 3 results demonstrating that panitumumab
significantly improved progression-free survival and disease control
(response rate and stable disease) compared to best supportive care
(BSC) in metastatic colorectal cancer patients who had failed standard
chemotherapy. The results were presented in a Clinical Plenary Session
at the 97th Annual Meeting of the American Association for Cancer
Research (Abstract #CP-1).
"Panitumumab reduced the rate of disease progression by
approximately half compared to best supportive care alone in these
heavily pre-treated patients," said Marc Peeters, M.D., Ph.D.,
coordinator of Digestive Oncology Unit, University Hospital Ghent, and
one of the study's lead investigators. "Furthermore, the difference in
objective response rates and the proportion of patients with disease
stabilization between panitumumab and best supportive care alone
demonstrated the significant activity of this agent."
In this multi-national, open-label Phase 3 study, 463 patients
with metastatic colorectal cancer who had failed standard
chemotherapy, including oxaliplatin and irinotecan, were randomized to
receive 6 mg/kg panitumumab plus BSC (n=231) every two weeks or BSC
alone (n=232). An independent, central radiology review board assessed
disease progression and tumor shrinkage.
Patients who received panitumumab every two weeks showed a 46
percent decrease in tumor progression rate versus those who received
best supportive care alone (p less than 0.000 000 001). A
significantly higher proportion of patients were alive and free of
disease progression on panitumumab at all of the scheduled time points
through week 32. For example, after six months (week 24) approximately
four times as many panitumumab-treated patients were alive and
progression-free (18 percent versus five percent with BSC alone).
Twice as many panitumumab-treated patients were alive and
progression-free at week 32 (10 percent versus four percent with BSC
Study investigators also reported that panitumumab significantly
improved disease control versus BSC alone (36 percent versus 10
percent, respectively), as measured by response rate and stable
disease. The objective, independently evaluated response rate was
eight percent with panitumumab versus zero with BSC alone, and the
median duration of response was 17 weeks. The stable disease rate was
28 percent with panitumumab versus 10 percent with BSC alone.
Approximately 75 percent of the best supportive care patients
entered a cross-over arm to receive panitumumab after their disease
had progressed (n=174). Panitumumab treatment also showed a clinical
benefit in the patients crossing over from the BSC arm, despite their
disease progression. In these patients, panitumumab treatment resulted
in a nine percent partial response and 32 percent stable disease, as
well as one complete response.
An interim analysis of overall survival between the two groups was
similar. The rate (75 percent) and timing (median 7.0 weeks) of
crossover from the BSC alone arm to receiving panitumumab, and the
anti-tumor activity observed after crossover, likely confounded the
ability to demonstrate a treatment effect on overall survival (Hazard
ratio = 0.93).
Panitumumab improved progression-free survival and response rate
regardless of the measured level or intensity of EGFr staining.
Improvements in progression-free survival and disease control also
occurred regardless of age, sex, primary tumor location (colon versus
rectum), or performance status.
Per protocol, administration of panitumumab did not require
pre-medication or a loading dose and the incidence of infusion
reactions (of any severity) was low (one percent). There were no grade
3 or 4 infusion reactions. More patients in the panitumumab arm
reported skin toxicities, fatigue, abdominal pain, nausea and
diarrhea. Hypomagnesemia was observed in 38 percent of
panitumumab-treated patients (three percent Grade 3/4). No de novo
human anti-human antibody (HAHA) or anti-panitumumab antibody
formation was observed. In patients with anti-panitumumab antibodies,
there was no impact on efficacy, safety and pharmacokinetics.
Patients and physicians can access www.amgentrials.com for more
information about ongoing panitumumab clinical trials.
Amgen will host a webcast with the investment community today at
12:30 P.M. EDT to discuss the Phase 3 data. Open to members of the
news media, investors and the general public, the webcast can be found
on Amgen's Web site, www.amgen.com, under Investors. It will be
archived and available for replay at least 72 hours after the event.
Panitumumab is an investigational fully human monoclonal antibody
that targets the epidermal growth factor receptor (EGFr), a protein
that plays an important role in cancer cell signaling. Panitumumab, an
IgG2 monoclonal antibody, binds with high affinity to the EGFr.
Panitumumab was generated with XenoMouse(R) technology, which creates
a fully human monoclonal antibody that contains no murine (mouse)
protein. The body's immune system can recognize the mouse protein
found in chimeric and humanized antibodies as foreign and launch an
immune response in the form of infusion reactions, allergic reactions
or anaphylaxis. The goal of developing fully human monoclonal
antibodies is to offer effective, high affinity therapies that
minimize the potential for this type of immune response.
Panitumumab received Fast Track designation from the U.S. Food and
Drug Administration (FDA) in July 2005 for patients with metastatic
colorectal cancer who have failed standard chemotherapy treatment. It
is being evaluated in clinical trials as both a monotherapy and in
combination with other agents for the treatment of various types of
cancer, including colorectal, lung and head and neck.
About the Epidermal Growth Factor Receptor (EGFr)
Although EGFr normally helps regulate the growth of many different
cells in the body, EGFr also can 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, such as
epidermal growth factor (EGF) or transforming growth factor alpha
(TGF-alpha), 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 the natural
ligands such as EGF and TGF-alpha 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 Colorectal Cancer
Colorectal cancer is the third most common cancer diagnosed in men
and in women in the United States. The American Cancer Society
estimates that about 106,680 new cases of colon cancer and 41,930 new
cases of rectal cancer will be diagnosed in 2006.
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