VECTIBIX BENEFITS AND SIDE EFFECTS
The Food and Drug Administration (FDA) approved Amgen's Vectibix
(panitumumab; formerly known as ABX-EGF) for the treatment of patients with
colorectal cancer that has metastasized (spread to other parts of the body) following
standard chemotherapy. Vectibix, a monoclonal antibody that binds to a protein
called epidermal growth factor receptor or EGFR on some cancer cells, received an
accelerated approval after showing effectiveness in slowing tumor growth and, in
some cases, reducing the size of the tumor. [4]

FDA approved Vectibix on the basis of the results of a randomized, controlled
clinical trial of 463 patients with metastatic cancer of the colon and the rectum after
undergoing treatment with chemotherapy drugs, fluoropyrimidine, oxaliplatin and
irinotecan. [4]

The mean time to disease progression or death in patients receiving Vectibix was
96 days versus 60 days in patients receiving the best standard supportive care. In
addition, 8 percent of the patients on Vectibix experienced a tumor shrinkage that in
some cases exceeded 50 percent of the pre-treatment size of the tumor. Both study
groups showed similar overall survival. [4]

SIDE EFFECTS OF VECTIBIX
The most serious adverse events in the studies of Vectibix included pulmonary
fibrosis, severe skin rash complicated by infections, infusion reactions, abdominal
pain, nausea, vomiting and constipation. The most common adverse side effects of
Vectibix associated with the drug included skin rash, fatigue, abdominal pain,
nausea, and diarrhea. [4]
First- and second-line therapy of metastatic colorectal cancer
In the United States, it is estimated that 150,000 new cases of colon cancer will be
diagnosed and 55,000 deaths will occur from colon and rectal cancer in 2006.
Approximately 70 percent of all colorectal carcinomas test positive for EGFR.
Colorectal cancer is the third most common cancer and the third leading cause of
cancer mortality in the United States. [4]

After years of stagnation, the treatment of metastatic colorectal cancer has recently
made dramatic advances. The previous standard of care, 5-fluorouracil, becomes
the backbone of combination regimens with oxaliplatin or irinotecan. The addition of
biological agents, such as the vascular endothelial growth factor inhibitor,
bevacizumab, and the epidermal growth factor receptor inhibitors, cetuximab and
panitumumab, have further enhanced the activity of conventional chemotherapy.
These advances have increased the overall survival of advanced colorectal cancer
patients, which was once 6 months with best supportive care, to over 2 years if all
active agents are used in the course of the disease. [3]

Role of Panitumumab in the management of metastatic colorectal cancer.
Panitumumab has proven to be very well tolerated alone and in combination with
other cytotoxic chemotherapeutic agents. Panitumumab has demonstrated efficacy
as monotherapy and with standard chemotherapeutic agents in a wide variety of
cancer types, including non-small-cell lung cancer, renal, and colorectal cancer. The
only significant toxicity or side effect has been a rash similar to that seen with other
agents targeting the epidermal growth factor receptor, and such reactions have
been predominantly mild to moderate. [1]

In metastatic colorectal cancer, panitumumab has been safe and efficacious when
given with other commonly used agents in this disease, including irinotecan and
fluorouracil. Current studies under way are looking at panitumumab in combination
with FOLFOX (fluorouracil/leucovorin/oxaliplatin) plus bevacizumab as well as with
novel agents that have yet to come into common clinical practice. [1]

Phase III Trial Results
The results of a phase III trial which compared panitumumab as a single agent to
best supportive care in patients with previously treated metastatic colorectal cancer
have recently been reported Pantitumumab therapy resulted in a 46% reduction in
the risk of tumor progression and a partial response rate of 8%. The side effect -
rash was reported in 90% of patients with increased severity significantly correlated
with improved medium overall survival (OS). [2]

About Amgen
Amgen has a market capitalization of about $79.77 billion and a range of drugs
aimed at treating cancer and anemia. It is the cancer franchise that caught a boost
with the approval of Vectibix in September of 2006. Vectibix is shaping up to be a
key competitor with Imclone Systems Inc's Erbitux. Both drugs are aimed to treat
colon cancer. [5]

REFERENCE:
[1] Saif MW and Cohenuram M, Yale University School of Medicine, Role of
panitumumab in the management of metastatic colorectal cancer. Clin Colorectal
Cancer. 2006 Jul;6(2):118-24. [2] Gibson TB, et al, CIG Medical Group,
Randomized phase III trial results of panitumumab, a fully human anti-epidermal
growth factor receptor monoclonal antibody, in metastatic colorectal cancer. Clin
Colorectal Cancer. 2006 May;6(1):29-31. [3] Terstriep S et al, Mayo Clinic College
of Medicine, First- and second-line therapy of metastatic colorectal cancer. Expert
Rev Anticancer Ther. 2006 Jun;6(6):921-30.  [4] FDA Approves a New Drug for
Colorectal Cancer, Vectibix FDA News September 27, 2006. [5] The Year in
Review: Amgen's Good News  AP December 27 2006
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