Monoclonal Antibodies
Anti-angiogenesis
Targeted therapy is the
result of about 100 years of research dedicated to understanding the differences
between cancer cells and normal cells. To date, cancer treatment has
focused primarily on killing rapidly dividing cells because one feature of
cancer cells is that they divide rapidly. Unfortunately, some of our
normal cells divide rapidly too, causing multiple side effects.
Targeted therapy is about
identifying other features of cancer cells. Scientists look for specific
differences in the cancer cells and the normal cells. This information is
used to create a targeted therapy to attack the cancer cells without damaging
the normal cells, thus leading to fewer side effects. Each type of
targeted therapy works a little bit differently but all interfere with the
ability of the cancer cell to grow, divide, repair and/or communicate with other
cells. Modern targeted therapy types include the use of monoclonal
antibodies and anti-angiogenesis drugs, both of which are described in greater
depth here.
The different types of
targeted therapies are defined in three broad categories. Some targeted
therapies focus on the internal components and function of the cancer
cell. The targeted therapies use small molecules that can get into the
cell and disrupt the function of the cells, causing them to die. There
are several types of targeted therapy that focus on the inner parts of the
cells. Other targeted therapies target receptors that are on the
outside of the cell. Therapies that target receptors are also known
as monoclonal antibodies. Anti-angiogenesis drugs target the blood
vessels that supply oxygen to the cells, ultimately causing the cells to
starve.
Researchers agree that
targeted therapies are not a replacement for traditional therapies.
Targeted therapies involve production of components such as monoclonal
antibodies or anti-angiogenesis drugs may best be used in the short term,
combination with traditional therapies. More research is needed to
identify which cancers may be best treated with targeted therapies such as
monoclonal antibodies or anti-angiogenesis drugs and to identify
additional targets for more types of cancer.
Targeted Cancer Therapies
Using Monoclonal Antibodies as Targeted Therapy
Monoclonal antibodies are a relatively new type of "targeted" cancer
therapy. Antibodies are part of the immune system. Normally, the
body creates antibodies in response to an antigen (such as a protein in a germ)
entering the body. The antibodies attach to the antigen in order to mark
the antigen for destruction by the body's immune system. In the
laboratory, scientists analyze specific antigens on the surface of cancer cells
(target) to determine a protein to match the antigen. Then, using protein
from animals and humans, scientists work to create a special antibody that will
attach to the target antigen. An antibody will attach to a matching
antigen like a key fits a lock. This technology allows treatment to
target specific cells, causing less toxicity to healthy cells.
Monoclonal antibody therapy can be done only for cancers in which antigens (and
the respective antibodies) have been identified. The following are
monoclonal antibodies:
Anti-angiogenesis
(Angiogenesis Inhibitors)
Anti-angiogenesis is the process of stopping the formation of new blood
vessels. A little background on angiogenesis would be helpful to
understand how this works.
In normal tissue, new blood
vessels are formed during tissue growth and repair (i.e. a healing wound), and
during the development of baby during pregnancy. Blood vessels carry
oxygen and nutrients to tissue that are necessary for growth and
survival. In cancer, tumors need blood vessels in order to grow and
spread. Through a complex process, endothelial cells (which line the
blood vessels) are able to divide and grow and create new blood vessels.
This process is called angiogenesis and it occurs in both healthy tissue and in
cancerous tissue.
There are known substances
that both stimulate angiogenesis and stop, or inhibit, angiogenesis.
Since 1971, Judah Folkman, a surgeon from
It is too early to know if
these angiogenesis inhibitors will be effective components in human cancer
therapy. Currently, there are more than 20 compounds being tested on a
variety of cancers in clinical trials. Some of these angiogenesis
inhibitors are available commercially, approved by the FDA for other
uses. Drugs like Interferon-alpha and Thalidomide are believed to have some
ability to inhibit angiogenesis and are being studied in specific cancer types
of cancers. Other anti-angiogenesis drugs are new, not approved by
the FDA and can only be given in clinical trial situations; most often for
advanced disease. Researchers are working to learn the safety and
efficacy of these medications.
The hope is that
angiogenesis inhibitors will have less toxicity, since it would only affect the
development of new blood vessels. However, since these medications are
given systemically (absorbed by the whole body), unexpected side effects are
likely. It is also too early to tell if anti-angiogenesis drugs will
damage healthy blood vessels that may be needed elsewhere in the body.
The benefits and risks of anti-angiogenesis drugs will be determined through
clinical trials over the next several years.
Using (and enhancing) the
body's natural systems and processes to aid in cancer therapy is closely
related to the topic of immunotherapy and the immune system in general.
Source: chemocare.com