Uses for Recombinant Protein Drugs - Biotechnology and Your Health: Pharmaceutical Applications - page 80

Scientists have long hoped that biologic-based cancer treat-
ments would provide a deadly blow to the cancer cells while leaving
normal cells unaffected, thus sparing patients these devastating
and sometimes lethal side effects. That ideal has proven difficult
to achieve, in part because some of these biologic-based cancer
treatments rely on signal proteins that have multiple functions.
Interleukin-2 (Proleukin) is a good example of the narrow window
between benefit and harm that new cancer therapies share with the
old. Developed because it was believed to trigger an immune system
attack on tumor cells, interleukin-2 treatment produces a range of
side effects: fevers, aches and pains, diarrhea, nausea and vomiting,
very low blood pressure, difficulty breathing, and many more. The
symptoms can be nearly unbearable and even life-threatening
because interleukin makes the small blood vessels in the lungs leak
fluids. Depending on the kind of cancer, 2-4% of patients treated
with interleukin-2 die as a result of the treatment. Interleukin-2
is also used in denileukin diftitox (Ontak ® ), a recombinant protein
drug that combines interleukin-2 with the cell-killing part of
the diphtheria toxin protein. Denileukin diftitox is used to treat a
rare form of skin cancer called cutaneous T cell lymphoma that
comes from T lymphocytes. Because these cancer cells may display
receptors for interleukin-2 on their membranes, interleukin-2
becomes the missile that delivers the toxin warhead, killing the
cancer cells. Denileukin diftitox shares many side effects with
interleukin-2.
Monoclonal Treatments for Cancer
Monoclonal antibodies are used in a number of cancer treatments.
They can target particular molecules that are found only or most
often on certain cancer cells. Gemtuzimab ozogamicin (Mylotarg ® ),
used to treat a form of leukemia, consists of a cell-killing cancer
drug purified from bacteria chemically linked to a monoclonal
antibody that reacts with a protein present on the leukemia cells