Uses for Recombinant Protein Drugs - Biotechnology and Your Health: Pharmaceutical Applications - page 81

and on some white blood cells. The antibody delivers the drug to
the cells and shuttles the whole thing inside, where the drug is
clipped off and then binds to and damages the cell's DNA, thus
killing the cell.
Antibodies can also be effective without a linked “warhead.” In
some situations, the tail end of the antibody that has attached to the
tumor cell starts a process that utlimately kills the cell. Rituximab
(Rituxan ® ), a monoclonal antibody that binds to CD20, present
on antibody-producing white blood cells—B lymphocytes, or B
cells—and on the surface of solid tumor cells derived from B
lymphocytes, is used to treat B cell solid tumors.
Other antibodies used to treat cancer work by binding to a
docking protein for a growth factor receptor, thus preventing the
growth factor from binding. Trasuzumab (Herceptin ® ) is used to
treat breast cancer that has spread throughout the body, and cetux-
imab (Erbitux ® ) isused for tumors of the digestive tract. Both are
monoclonal antibodies that bind to two different receptors for
epidermal growth factor, a protein hormone that triggers cell
division. By occupying the receptors and denying access to the
growth factor, the antibodies cause tumor cells to die. When used
with chemotherapy drugs, these antibodies administer a double blow
to these advanced tumors.
Both normal cells and tumor cells require blood circulation
to provide the oxygen and the nourishment they need to survive.
Bevacizumab (Avastin™) is used to treat advanced forms of cancer
of the digestive system; it is a reengineered mouse monoclonal
antibody that binds to a growth factor receptor required for the
development of blood circulation around a tumor.
Stop and Consider
What advantages might factory-produced biotechnology drugs have
over proteins purified from humans?