Monoclonal antibody therapy is sometimes referred to as passive immunotherapy because it doesn't directly stimulate your immune system to respond to a disease. Instead, monoclonal antibody therapy mimics the natural antibodies made by the body.
A monoclonal antibody is an immune protein made in a laboratory. It's designed to react with or attach to antigens - foreign substances such as bacteria, viruses, fungi and allergens - on the surface of cancer cells. The monoclonal antibody aims for the molecule and attaches itself to the cell, blocking or interfering with the cell's activity. Because the drug attacks a specific target or marker on the cell, monoclonal antibody therapy is also called targeted therapy.
Monoclonal antibody therapies can cause side effects, but they're generally milder than chemotherapy's side effects. Because they're designed to target and attack specific substances, they tend to leave normal cells unharmed. Targeted treatment may also increase the frequency of and prolong remissions.
Doctors use monoclonal antibodies either alone or with another substance attached to them:
- Naked antibodies don't have another chemical or radioactive material attached. Rituximab (Rituxan®) and alemtuzumab (Campath®) are examples of naked monoclonal antibody therapy. The antibodies recognize and attach to specific cells. They can destroy the cancer cell when they attach to the cell's critical antigen.
- Conjugated antibodies have radioactive isotopes (radioimmunotherapy) or toxins (immunotoxin) attached to them. Daunorubicin (Cerubidine®), doxorubicin (Adriamycin®), idarubicin (Idamycin®) and mitoxantrone (Novantrone®) are examples of conjugated antibody therapy. They deliver the toxic substance directly to the cancer cells and destroy them.
What to Expect
Monoclonal antibody therapies are usually given to individuals in an outpatient setting, usually over several weeks. The drug is delivered through a needle placed in your vein (intravenous infusion, or IV) in your arm. Your doctor may prescribe drugs before each infusion to reduce certain side effects. He or she regularly tests your blood between treatments and after treatment is completed to look for other side effects.
Side effects such as fever and chills, tiredness, headache and nausea are among the most commonly reported reactions to Rituxan and Campath. Other less common, but more severe, side effects include shortness of breath, a drop in blood pressure, an irregular heartbeat, chest pain and low blood cell counts